Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

Recently, soft robots have attracted considerable attention; however, they often undergo large deformations. Thus, their lifespans are critical issues. Therefore, this study proposes a novel method for extending the lives of rubber materials. We extend the fatigue life of rubber materials by focusing on the hysteresis of the straininduced crystallization characteristics of rubber. Strain-induced crystallization is a phenomenon wherein rubber molecules exhibit crystal structures by elongation. These crystal structures are generated by elongation and disappear with relaxation. However, hysteresis occurs in both the generation and disappearance processes. Therefore, if the rubber is not completely relaxed, the disappearance of the crystal layers is slowed by hysteresis, and the formation of cracks is hindered. Herein, we select two types of rubbers: those exhibiting strain-induced crystallization characteristics (natural rubber (NR)) and those that do not (styrene-butadiene rubber (SBR)). First, wide-angle X-ray diffraction is used to confirm the formation of crystal layers under stretching for both types of rubbers. Fatigue life test is conducted using rectangular test pieces made of NR and SBR by repeated tensile tests. Subsequently, a fatigue life test is conducted for a straight-fiber-type pneumatic artificial muscle prepared by NR and SBR. The results reveal that the fatigue life is approximately 100 times longer than normal, thereby confirming the effects of prolonging the fatigue life using the hysteresis of strain-induced crystallization.

DOI： 10.1016/j.polymertesting.2022.107800

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPRINGER INTERNATIONAL PUBLISHING AG  

In this study, a support device for liquefied petroleum (LP) gas cylinder delivery was developed and evaluated using questionnaires. This study contributes to developing a method for reducing the burden of gas cylinder delivery. LP gas cylinders are manually transported, and the physical burden on delivery personnel is high. Existing methods to minimize this burden include cart transportation. In the delivery environment, narrow spaces and steps exist, increasing the difficulty of cart transportation. Therefore, we propose a support device as a new method for reducing this burden. The support device was designed based on a survey of the LP gas cylinder delivery environment and a method for holding cylinders. The support device enhanced walking and was less physically demanding. The subjective evaluation showed that it exhibits the characteristics of the main method used for holding cylinders while improving the shortcomings. This device significantly reduces the load on the upper body during delivery.

DOI： 10.1007/978-3-031-15226-9_50

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Other Link： https://dblp.uni-trier.de/db/conf/clawar/clawar2022.html#ObaON022

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPRINGER INTERNATIONAL PUBLISHING AG  

In this study, the authors model and conduct experiment on the braid propulsion unit of an excavation robot for lunar exploration. In existing studies, it is difficult for robots to create sufficiently big holes and achieve deep excavations. Therefore, in this study, we developed a lunar earthworm-type excavation robot "LEAVO," which attempts to excavate boreholes for environmental sensors and collect samples in particular layers. LEAVO has already succeeded in a vertical excavation of more than 938 mm and we have verified its usefulness in the first target mission. However, the existing propulsion unit of LEAVO cannot sufficiently bend and grip curved or uneven walls. In this research, we proposed a novel propulsion unit using braid to achieve curving excavation for the second target mission, modeled the gripping force of the proposed mechanism, and measured the gripping force of the prototype using the mechanism. The experiment demonstrated the validity of the modeling and the usefulness of the proposed mechanism.

DOI： 10.1007/978-3-031-15226-9_6

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Other Link： https://dblp.uni-trier.de/db/conf/clawar/clawar2022.html#FujikawaTTOT0K22

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We present the development of a wearable body support device for LP gas delivery work and evaluation of the device by wearers. This study proposes a method for reducing the physical burden involved in delivering LP gas cylinders, as LP gas cylinders are transported manually. Delivery personnel must navigate stairs and narrow spaces, which make it difficult to use existing methods for reducing physical burden, such as carts. We aim to develop a device that can be used for LP gas delivery. In a previous study, we conducted a field survey. We found that the burden on delivery workers was due not only to carrying the cylinder, but also to lifting. Based on the field survey, this paper describes the development of a lifting support device that reduces the physical burden and facilitates smooth delivery. The subjective evaluations confirmed that the proposed device reduced the physical burden while providing the same ease of lifting as do conventional grasping methods. The device is designed to support lifting during delivery work and greatly supports lifting movements during delivery work.

DOI： 10.1109/IECON51785.2023.10312418

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In recent years, the sea ice in the Arctic Ocean has been decreasing due to climate change caused by greenhouse gases. Therefore, the phenomena under the sea ice must be investigated. The existing method of autonomous underwater vehicle (AUV) exploration is limited by its narrow communication and acoustic triangulation range. Therefore, digging a hole through the ice sheet is proposed to secure a communication relay system under the ice sheet. The objective of this study is to develop a robot using peristaltic motion as a system for drilling holes in sea ice. In the previous study, we determined the required specifications for the sea ice drilling robot. In this study, the excavation unit and the propulsion unit of the sea ice drilling robot are developed according to this specification. The basic characteristics of each mechanism were evaluated, and the digging performance of the excavation unit and the gripping performance of the propulsion unit were confirmed.

DOI： 10.1109/IECON51785.2023.10311873

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In recent years, force feedback devices have been developed to improve the reality of VR experiences. However, a majority of force feedback devices target the upper limbs. Force feedback to the lower limbs will enable a VR experience that cannot be achieved by force feedback to the upper limbs alone. In this study, an exoskeletal lower limb force-feedback device was developed to improve the sense of reality in a Virtual Reality (VR) space. This device has Magnetorheological (MR) fluid brakes placed at the joints and can present frictional and viscous force through torque control. We designed a drag model that simplifies the force generated in reality as the force presented when the knee is operated in water. Then, the sensation of motion when the knee is flexed and extended in water was evaluated from the viewpoints of reality and drag force. The experimental results showed that the force presentation using the MR fluid brake proportional to the velocity gave a sense of reality of approximately 50%.

DOI： 10.1109/ISIE51358.2023.10227941

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Sewerage systems are indispensable infrastructures; thus, it is important to monitor their condition through periodic inspections. The wall thickness of pipes is particularly important during inspection. However, measuring the wall thickness of pipes in long, narrow, and complicated shapes using existing technologies is difficult. Therefore, this study aims to establish a method for measuring and estimating the inside diameter of pipes that can be used for long-distance, complex buried pipes. In a previous study, a pneumatically driven robot was developed for long-distance pipe inspection. We proposed a method to estimate the pipe inner diameter from the information obtained from the driving unit of this robot. In this method, a geometry model of the pneumatic drive unit was developed, and the model was used to estimate the pipe's inner diameter from the supply pressure and flow rate to the unit. Experimental results show that the developed model can estimate the inside diameter within an error range of less than 5%. This method can be used to estimate the inside diameters of long, narrow, and complicated pipes, and it can help prevent accidents, such as liquefaction and gas leakage caused by pipe failure.

DOI： 10.1109/ISIE51358.2023.10228060

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Other Link： https://dblp.uni-trier.de/db/conf/isie/isie2023.html#NagashimaINUO23

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It is estimated that 250 million visually impaired people reside worldwide, and this number is expected to increase. Even though Braille blocks and guide dogs are used to guide the visually impaired, availability of installation location and cost are some of the major issues in implementing the same. Therefore, there is a need for a device for personal guidance that does not limit the location of use. Therefore, this study focuses on force-sensing presentation using the reaction force of air jets. The proposed white cane-type force-sensing device consists of a white cane, an air pressure source, solenoid valves, and a nozzle is attached to the white cane to inject compressed air. The reaction force obtained at the time of jetting generates a moment in the hand of the user, presenting force perception. Here, as a part of an initial study of the device, the effectiveness of the directional presentation, an obstacle avoidance experiment using an ultrasonic sensor, and a demonstration experiment of guidance were conducted.

DOI： 10.1109/SII55687.2023.10039470

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This study proposes an evaluation simulator for gastrointestinal stents that reproduces the three-dimensional (3D) behavior of the intestine. One of the symptoms of colorectal cancer is intestinal obstruction. When an intestinal obstruction occurs, the contents of the intestinal tract become blocked, which has various adverse effects on the body. Treatment of intestinal obstruction is generally conservative, but surgery is performed when improvement is not expected. Currently, there are two methods of evaluating the performance of gastrointestinal stents: durability and movement tests. In the durability test, a compression test is repeatedly performed to evaluate the durability of the gastrointestinal stent. In the movement test, the stent is compressed continuously like a wave, and the displacement of the gastrointestinal stent with respect to the number of repetitions is measured. These two types of evaluation tests are used to evaluate the function of the gastrointestinal stent. However, there is no unified standard for evaluation tests of gastrointestinal stents, and each manufacturer conducts their own performance tests. In addition, current evaluation test methods differ from the actual intestine at multiple points. Therefore, an evaluation test method that can reproduce the environment of the intestinal tract with high accuracy is needed. Therefore, the authors focused on a peristaltic pump that mimics a living body. We propose an evaluation simulator for gastrointestinal stents that can reproduce 3D behavior similar to actual intestinal peristalsis, based on the driving principle of a unit-connected peristaltic pump. This paper first establishes the concept behind the development of an evaluation simulator for gastrointestinal stents, and then describes the developed evaluation simulator. Finally, we conducted experiments to measure the contraction pattern and internal pressure during contraction of the evaluation simulator and evaluated this simulator by comparing it with the actual peristalsis of the intestinal tract. The experimental results confirmed that it is possible to reproduce behavior similar to the actual intestinal tract movement.

DOI： 10.1109/ROBIO58561.2023.10354781

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Other Link： https://dblp.uni-trier.de/db/conf/robio/robio2023.html#UzawaHON23

Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Artificial muscles are advantageous owing to dynamic stiffness; however, the drawback of this is their poor controllability. Here, a reinforcement learning-based control system is proposed and exemplified on a realistic artificial muscle-driven robot. The proposed system suppresses the modeling error, and allows to generate dynamic motion patterns that utilize the body structure and variable stiffness characteristics. As an example application, we consider drum playing. We propose a reinforcement learning-based realistic drum-playing robot. We propose a reinforcement learning-based strategy for this realistic robot and confirm its effectiveness through simulations and experiments.

DOI： 10.1109/IECON49645.2022.9968757

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Language：Japanese   Publisher：THE VIRTUAL REALITY SOCIETY OF JAPAN  

Various haptic devices for application to virtual reality have been developed. Most of them have to be stationary on a desk, thus users cannot move around. To overcome this shortcoming, we propose a wearable force feedback device that uses air jet. In this paper, a prototype for hand position guidance which is able to provide force in any direction is developed, and its performance to guide the wearer’s hand is evaluated by experiments.

DOI： 10.18974/tvrsj.27.3_264

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI  

With the diversification of robots, modularization of robots has been attracting attention. In our previous study, we developed a robot that mimics the principle of human joint drive using a straight-fiber-type pneumatic rubber artificial muscle ("artificial muscle") and a magnetorheological fluid brake ("MR brake"). The variable viscoelastic joints have been modularized. Therefore, this paper evaluates the basic characteristics of the developed Joint Module, characterizes the variable viscoelastic joint, and compares it with existing modules. As basic characteristics, we confirmed that the Joint Module has a variable viscoelastic element by experimentally verifying the joint angle, stiffness, viscosity, and tracking performance of the generated torque to the command value. As a characteristic evaluation, we verified the change in motion and response to external disturbances due to differences in driving methods through simulations and experiments and proved the strength of the variable viscoelastic joint against external disturbances, which is a characteristic of variable viscoelastic joints. Based on the results of the basic characterization and the characterization of the variable viscoelastic drive joint, we discussed what kind of device the Joint Module is suitable to be applied to and clarified the position of the variable viscoelastic joint as an actuator system.

DOI： 10.3390/act11030089

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In this paper, we describe the development of short-fiber oriented rubber and its application to elongation-type actuators. Short-fiber oriented rubber, i.e., rubber containing oriented short fibers with lengths of 3 mm, has anisotropy in the direction of fiber orientation. In a previous study, it was shown that short fiber-reinforced artificial muscles made of short-fiber oriented rubber can achieve up to 17% shrinkage. However, in that study, characteristics other than the amount of shrinkage were not measured, the basic characteristics of the developed artificial muscle were unclear, and the shrinkage ratio was smaller than that for existing straight-fiber-type artificial muscle. In the present study, we developed a new method for fabricating short-fiber oriented rubber and measured the tensile characteristics in the direction of fiber orientation and vertical to the orientation direction. Moreover, we developed an elongation-type artificial muscle from the rubber sheet and measured its elongation characteristics. Test results indicated that the fabricated rubber sheet had anisotropy. They also indicated that the anisotropy increased with the fiber concentration and that the fiber restraint acted not only in the orientation direction but also in the vertical direction. Furthermore, the developed elongation-type artificial muscle was three times more anisotropic in the ratio of axial changes to diametral changes. On the basis of these results, we expect to develop an automated production method for soft actuators.

DOI： 10.1109/IECON49645.2022.9969096

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Springer  

The results of an excavation experiment in an actual sea area using the earth worm type seabed exploration robot are reported in this paper. The robot tested in the experiments is SEAVO II, which has been developed by the authors. Seawater-resistant processing was applied to the SEAVO II, and field experiments were conducted on the coast of Izu Oshima island. Four types of experiments were conducted: vertical excavation in sand, gravel, and water, and horizontal excavation in sand. In the vertical excavation on sand, the SEAVO II successfully excavated 490 mm, which is the same level as that of the previous studies. However, although the excavation was difficult and the excavating distance was limited to 100 mm or less for the other three conditions, the issues in each environment could be clarified.

DOI： 10.1007/978-3-030-86294-7_30

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Other Link： https://dblp.uni-trier.de/db/conf/clawar/clawar2021.html#OkuiTTTIW0Y21

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The intestines are an autonomous decentralized system with a neural network independent of the brain. Until now, some devices could reproduce the movement of the intestines, but autonomously switching the movement pattern as the biological intestine was impossible. In this study, we proposed a method for generating an autonomous peristaltic movement of a peristaltic continuous mixing conveyor that mimics the intestines. Peristaltic movements contribute to the transport of intestinal contents. With the proposed method, peristaltic movement is generated when the intestinal contents are detected by a unit with a unitized device. The proposed method was installed in a peristaltic continuous mixing conveyor and experimentally verified. The peristaltic movement was generated when there was content, and the content was successfully transported.

DOI： 10.1109/SII52469.2022.9708865

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Other Link： https://dblp.uni-trier.de/db/conf/sii/sii2022.html#MatsuiOTNON22

Language：English   Publisher：Springer  

Mineral resources such as rare earths are deposited 2 to 3 m below the seafloor; for detailed studies to elucidate their origin and existence, it is necessary to collect samples of seafloor sediments. Currently, vertical drilling is commonly used to collect samples, but it is inefficient because the seafloor sediments are widely deposited horizontally. Therefore, we develop a robotic seafloor explorer. In this study, we worked on horizontal drilling as the next stage. First, a mechanical model of the robot's penetration into the ground during horizontal excavation was developed, and the expected challenges of horizontal drilling were discussed based on the model. After that, horizontal excavation experiments were conducted, and the challenges were clarified from the results.

DOI： 10.1007/978-3-030-86294-7_29

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Other Link： https://dblp.uni-trier.de/db/conf/clawar/clawar2021.html#TokoiTTWO0Y21

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

We propose a transport system combining peristaltic motion and a negative pressure as a new method of transporting and collecting feces for space toilets. In recent years, for the development of space exploration, the need for a regenerative Environmental Control and Life Support System (ECLSS) to perform manned space exploration for long periods without resource supply has emerged. Currently, human feces is disposed of, but if it can be reused like urine, the performance of the ECLSS can be significantly improved. Existing space toilets do not reuse of feces, and the transfer of feces presents a technical problem. There is no technology that can reliably transport highly viscous solid-liquid mixtures on an intermittent basis. If such technologies are developed, they will be useful for transporting not only feces in space but also chemicals on the ground. Therefore, the authors propose a peristaltic system based on the intestinal tracts of living organisms for the transport of feces in space. Each unit of the system can be actively closed and opened by air pressure. The units are operated in turn to transport feces. The proposed driving method utilizes the pressure difference between the units of a peristaltic pump to increase the transfer rate. A prototype system consisting of three units was developed, and a simulated feces transfer experiment was conducted to validate the proposed method. In the experiment, we compared the conventional peristaltic driving method and the proposed peristaltic driving method, and the results indicated that the proposed method can carry more than twice the amount of simulated feces. Thus, the proposed method is suitable for the transfer of feces in space and can be used to transfer highly viscous solid-liquid mixed fluids under intermittent supply and with little water consumption.

DOI： 10.1109/ACCESS.2022.3227068

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In wearable assist devices, the assumed and actual command timings are different. This discrepancy cause problems, such as a decrease in the assist effect. In this study, we focus on viscosity, which is a characteristic of human muscles, and propose viscosity assistance to solve the problems. This method outputs the torque based on the predetermined viscosity coefficient and the actual angular velocity if the torque and angular velocity of the human joints are in opposite directions. The possibility of viscosity assist is demonstrated by analyzing the seated movement, and an assist device using a magnetorheological fluid brake is developed. The assist device is driven using three command inputs: time-based, joint angle-based, and constant viscosity coefficient command inputs. Under conditions based on time and angle, the actual output deviates from the assumed value when the motion is different from the expected motion. In terms of the viscosity command, when only the constant command is used throughout the entire motion section, some subjects showed almost identical results to those expected. Even if a deviation from this assumption is indicated, the degree of agreement can be improved by switching several types of viscosity coefficients during motion.

DOI： 10.1109/RO-MAN53752.2022.9900630

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Other Link： https://dblp.uni-trier.de/db/conf/ro-man/ro-man2022.html#ShimodaFMONN22

Publishing type：Research paper (international conference proceedings)  

There is an urgent requirement to solve the problem of global warming. The sea ice beneath the Arctic Ocean strongly affects the global climate. However, it has not been fully explored. The range of Autonomous Underwater Vehicles (AUV) used for under-ice exploration is limited owing to their short communication range. To solve this problem, we propose a communication relay system that uses a sea ice drilling robot. We conducted excavation and gripping experiments on actual sea ice to study the parameters and control methods required to design a sea ice drilling robot. The required specifications of excavation and propulsion units were obtained from the experimental results, and a recovery method was developed to address drilling failure.

DOI： 10.1109/IECON49645.2022.9968618

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For space rockets, a rotating mixer is used to produce solid fuel. However, mixing with the rotary mixer is subject to high shear forces that limit the equipment drive. In a previous study, the authors developed a new production method using a pneumatically driven peristaltic mixing pump that simulates the intestine and a sensing system with pressure and flow rate sensors. Solid rocket fuel was successfully produced by a small pump unit. In this study, mixing experiments of solid propellant consisting of several types of powders, including metal powder and highly viscous fluids were conducted using a pump unit with a volume size eight times larger than that used in the previous study. In this experiment, mixing was performed with the materials packed in a plastic bag to increase efficiency. This reduces the contact area between the rubber tube and the contents of the device. Because only part of the mixing process is reflected in the behavior of the device, it is difficult to see differences in the sensor values, and it is unknown whether existing methods can be applied. The results of the experiment showed that the existing sensing system could be used to confirm the differences in characteristics due to the mixing process based on the time series data of air pressure and flow rate. By using Gaussian mixture model, which is a type of clustering, the mixing state was roughly binary discrimination from the acquired sensor values. This suggests that it is possible to estimate the mixing degree in large pumps using existing systems.

DOI： 10.1109/IECON49645.2022.9968625

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Because information transmission by force is a vector quantity with magnitude and direction, it can directly affect humans. However, most existing force feedback devices are stationary, and their movement is restricted. On the other hand, wearable force-feedback devices induce a strange feeling, as they must support the reaction force of the presented force at the body fixing part. Therefore, in this paper, we propose a posture guidance method using force feedback provided by air jets. Specifically, for table tennis movement guidance, we developed a prototype with two degrees of freedom using a table tennis racket. We also conducted a hand posture guidance experiment and confirmed that the proposed method can guide the wrist posture without disturbing the wearer's movement.

DOI： 10.1109/IECON49645.2022.9968815

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Recently, force feedback devices have been developed to improve the virtual reality (VR) experiences. However, most conventional force feedback devices target the upper limbs. In addition to achieving force feedback to the upper limbs, realizing force feedback to the lower limbs will make it possible to realize an experience in the VR space, which would not be achieved by force feedback to the upper limbs alone. The authors have elucidated the perceptual characteristics of the human dropping sensation to present force feedback to the lower limbs. In this study, we develop a pair of wearable force feedback shoes that can realize the falling sensation in the VR space. The proposed device meets the required specifications for descent height and acceleration to render the falling sensation. Furthermore, we confirm the usefulness of the theoretical equation by measuring the basic characteristics of the developed device.

DOI： 10.1109/IECON49645.2022.9968554

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In recent years, force feedback devices have been developed to improve the reality of virtual reality (VR) experiences. However, most of the general force feedback devices target the upper limbs. By realizing force feedback to the lower limbs, it is possible to realize an experience in VR space that cannot be achieved by force feedback to the upper limbs alone. Therefore, in this study, we developed a lower limb force feedback device based on a physical model of the human lower limb. The output torque of the developed device that met the target torque by the experiment was confirmed. The device was then experimented with to determine if it could reproduce an impact force similar to that of a soccer pass as an initial study. The results suggested that even a low torque of 10 Nm could reproduce a soccer pass.

DOI： 10.1109/IECON49645.2022.9968915

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In this study, we evaluate the dropping sensation for the development of a wearable lower limb force feedback device that can render both dropping and walking sensations. The developed device can render the dropping sensation at a smaller height than in reality by decelerating and stopping descent during the rendering of the drop image. Considering the user will be walking with the device, a smaller device height leads to better safety. The purpose of this study is to clarify the required specifications of the height of the vertical range of motion of the platform part, and the feasibility of the concept of rendering the dropping sensation. For this purpose, the dropping sensation for the difference in human acceleration time and human deceleration acceleration was evaluated. The results showed that the rendering of the dropping sensation required more than 0.41 s of descent at an acceleration of approximately 1377 mm/s2. Moreover, the dropping sensation and sense of reality were not impaired, even when the platform part of the foot was decelerated. This result indicates that the device can be made smaller.

DOI： 10.1109/RO-MAN50785.2021.9515498

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Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Investigation of the lunar subsurface environment is expected to lead to the elucidation of the origin of stars and the discovery of new resources. However, there are still many unknowns in this regard. In a previous study, we developed a drilling robot for lunar exploration and succeeded in drilling vertically up to 938 mm. However, control methods for the robot have not been studied in detail so far, and the grasping state of the propulsion unit during drilling has not been observed. In the study described in this paper, threshold coordination method for the current of the propulsion unit's motors is introduced to achieve effective hole grasping and propulsion. Subsequently, gripping force and penetrating force characteristics of the propulsion unit are tested to understand the grasping state of the propulsion unit during drilling based on the current value and the angle information of the motor. Finally, in-pipe propulsion and excavation experiments were conducted. From the experimental results, we concluded that the proposed control method can be used to grasp the hole with changing hole diameter and monitor the grasping state of the propulsion unit in the hole.

DOI： 10.1109/AIM46487.2021.9517536

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Other Link： https://dblp.uni-trier.de/db/conf/aimech/aim2021.html#TokoiTWTOSKN21

Language：Japanese   Publisher：IEEE  

Continuous mixing and conveying technologies for processing solid-liquid mixtures and highly viscous fluids are required in the manufacture of food and medicine. A device featuring such a technology, namely the peristaltic continuous mixing conveyor, has been developed by the authors previously. This device, imitating the movement of intestines, is capable of mixing and conveying content by inflating a rubber tube using air pressure. Herein, we aim to estimate the degree of mixing of the contents via machine learning using data from pneumatic factor sensors installed in this device. However, the low measurement accuracy of these sensors when dealing with compressible fluids makes the mixing degree estimation difficult. Therefore, in this study, to improve the measurement accuracy of the sensing system, we installed an accelerometer that could directly measure the behavior of the rubber tube inside the device without any contact with the contents being required. Upon operation of the device with various objects within it, the sensor angle of the rubber tube was obtained from the accelerometer values for each input. The sensor angle at steady state after air supply was 22.5° greater for the rigid bodies than for the mixtures of powder and liquid. For the powder-liquid mixtures, a linear relationship was demonstrated between the percent concentration of mass and the sensor angle at a steady state. The results suggest that the content of the device can be determined with greater accuracy by using the attitude angle obtained from the accelerometer than from the conventional pneumatic factor sensors.

DOI： 10.1109/AIM46487.2021.9517474

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Other Link： https://dblp.uni-trier.de/db/conf/aimech/aim2021.html#OshinoWMNON21

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In a virtual reality (VR) space, wearing a head-mounted display can help with the visualization of objects although users cannot experience realistic tactile sensations. Recently, several force feedback devices have been developed, including wearable devices that use straight-fiber-type pneumatic muscles and magnetorheological fluids. This allows the devices to render elastic, frictional, and viscous forces during spatially unrestricted movement. However, during friction and viscosity rendering, the elasticity of the artificial muscle is influenced by the elastic element of the muscle, preventing proper presentation of the force. Therefore, this study proposed a clutch mechanism to switch the force presentation of elastic elements by the contraction of artificial muscles. The mechanism was incorporated into a wearable four-degrees-of-freedom force feedback device, and its elastic, frictional, and viscous force feedback performances were quantitatively assessed via fundamental property experiments. Furthermore, a VR space was constructed to present the operator with force perceptions of virtual elastic, frictional, and viscous objects within that space, and the system's performance was qualitatively assessed. The results confirmed a reduction in the effect of elastic elements and an improvement in the presentation performance. Additionally, the use of this device in the VR space was confirmed to improve the realism of virtual objects in terms of friction and viscosity.

DOI： 10.1109/ICIT46573.2021.9453574

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI  

In this paper, the prototype of the assistive suit for lower limbs was developed. The prototype was based on an assist method with joint stiffness and antagonized angle control. The assist method comprises a system consisting of a pneumatic artificial muscle and a pull spring, which changes the joint stiffness and the antagonized angle to correspond to the movement phase and aims at coordinated motion assistance with the wearer. First, the characteristics of the developed prototype were tested. It was confirmed that the measured value of the prototype followed the target value in the relationship between torque and angle. In addition, there was hysteresis in the measured value, but it did not affect the assist. Next, the evaluation of standing-up and gait assist by measuring electromyography (EMG) of the knee extensor muscle was conducted using the prototype. In all subjects, a decrease in EMG due to the assist was confirmed. In one subject, the maximum decrease rate at the peak of the EMG was about 50% for standing-up motion and about 75% for gait motion. From the results of these assist evaluations, the effectiveness of the assist method based on the joint stiffness and antagonistic angle control using the prototype was confirmed.

DOI： 10.3390/act10010017

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

This paper describes the development of a compact pneumatic valve that can obtain a high flow rate in a periodically pneumatically driven pipe-moving robot. Plumbing facilities around the world have fallen into disrepair in recent years. Pneumatically driven mobile robots are widely used as an inspection method due to the small inner diameter and complicated shape of the pipes. Various types of robots have been studied, such as earthworm, inchworm, and spiral tube robots. However, these robots are driven by existing pneumatic valve technologies, such as needle-type and solenoid valves, which limit the use of small mobile robots. Small pneumatic valves have a low flow rate, and the entire system is complicated because multiple air pressures are controlled by multiple electrical systems. Thus, focusing on the structure and periodic motion of the ball valve, we developed a pneumatic valve that can periodically apply pressure to multiple pneumatic actuators using only rotational motion with one degree of freedom. We also applied this pneumatic valve to a wave propagation robot and discussed the theoretical running speed of the robot with this valve.

DOI： 10.1109/ACCESS.2021.3135035

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.2139/ssrn.3996748

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Publishing type：Research paper (scientific journal)   Publisher：Japan Society for Aeronautical and Space Sciences  

DOI： 10.2322/tastj.19.211

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In this study, the authors comprehensively evaluated the traveling performance of a flexible pipe inspection robot (PI-RO) that can actively output both propulsion and traction forces. Household pipes must be frequently inspected for cracks and corrosion to ensure continuous provision of water and gas. As these pipes are essential for our everyday life, it is difficult to suspend their usage for long periods; hence, inspection should be conducted for short durations. In addition, inspecting entire pipelines using existing methods is challenging because the pipes are constructed over long distances and have complex structures. Therefore, we developed a flexible robot that can actively output propulsion and traction forces to inspect long-distance complex pipelines, such as household pipelines. Herein, we describe the flexible structural design of a PI-RO that inspects thin one-inch pipes (inner diameter of approximately 28 mm) typically present in household piping. We also evaluated the characteristics of each PI-RO unit. Finally, we confirmed that the PI-RO is not significantly affected by the traveling environment, such as long distances and complex small-diameter pipes, by conducting traveling experiments on small pipes (inner diameter 28 mm) and long-distance (up to approximately 11.7 m) complex pipes composed of horizontal, vertical, and 90° bend pipes.

DOI： 10.1109/ACCESS.2021.3114698

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

We propose herein a method for estimating the mixing state of the contents of a peristaltic continuous mixing conveyor simulating the intestine, developed for mixing and conveying powders and liquids. This study serves to improve a previously proposed method for estimating the mixing state using a logistic regression model with the pressure and flow rate sensors installed in the device as inputs. Moreover, the estimation accuracy of the proposed method is better than that of the previous method. The generalizability of the proposed method is evaluated for four conditions in which the feeding order of the contents, powder, and liquid are changed. The feeding order is as follows: powder first, liquid first, and powder and liquid alternately. As a result, a highly accurate estimation of mixing is achieved under the condition wherein the powder component is in the unit adjacent to the lid, but not under the condition wherein the liquid component is fed first. It is speculated that this is because the movement of the powder component inside the device is more easily reflected by the pressure and flow rate sensors installed in the device than in the liquid component.

DOI： 10.1109/ACCESS.2021.3112614

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

Welding is one of the forms of nonautomated, heavy labor used in the shipbuilding industry. In the shipbuilding process, the hull is first welded by an industrial automatic welding machine, then irregular welded part correction and welding in narrow places that machines cannot reach are performed by welding workers. Welding operators are required to weld indeterminate objects in narrow working spaces. In addition, it is difficult to perform high-quality welding because the ability to accurately trace a welding line at a constant speed requires a long training period. In this research, a welding training device that assists trainees in skill acquisition was developed. The proposed device, which comprises two magnetorheological (MR) brakes, renders a welding path and restricts welding speed. The MR brakes have a response speed comparable to that of powder brakes, have a high output-to-weight ratio, and are also considered to be suitable for use in welding training devices. A prototype and control strategy were developed, and the performance of the device in actual welding work was evaluated. Results shows that path rendering strategy is possible to present routes with an accuracy of 1 mm or better and speed control strategy can regulate the speed required for welding.

DOI： 10.1088/1361-665X/aba846

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Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Many haptic devices are currently being developed for human upper limbs. There are various types of force feedback devices for upper limbs, such as desktop and wearable type. However, the lower limbs absorb most of the force when standing or walking. Therefore, to render the sensation of force to the lower limbs, a device worn like a shoe to enable users to walk and have a wide range of movement and a device that provides a dropping sensation have been developed. However, both wide-area movement and a dropping sensation could not be combined in one device. Therefore, the authors propose the concept of a lower limb force feedback device that allows the user to wear it like a shoe and provides the sensation of dropping while enabling wide-area movement. In addition, as the first stage of device development, the authors evaluated the human sensation of dropping. Consequently, it was found that a relatively high sensation of dropping can be provided to a human even with an acceleration smaller than the gravitational acceleration in real space. Thus, the lower limb force feedback device to be developed in the future will allow the user to experience the sensation of dropping by using an acceleration smaller than the gravitational acceleration in real space.

DOI： 10.1109/RO-MAN47096.2020.9223476

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Other Link： https://dblp.uni-trier.de/db/conf/ro-man/ro-man2020.html#TanakaOONN20

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Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Seabed mineral resources have been discovered on the bottom of the ocean; to utilize them, samples must be obtained and analyzed. In this study, a seafloor robotic explorer that can excavate and sample seafloor soil is developed. In a previous study, we developed a drilling robot that could excavate 650 mm into the ground while being underwater. And, we discovered that the excavation robot rotation speed, penetration force, and characteristics of the target ground affected the excavation resistance. In this paper, the effect of penetration force on excavation efficiency is verified experimentally using both dry and underwater silica sand ground with different ground characteristics. Results of the experiment indicated that the most efficient excavation was performed at 15 N in dry silica sand ground. In underwater silica sand ground, the excavation efficiency improved as the penetration force increased, and the most efficient excavation was achieved when the penetration force was 10 N. Hence, we concluded that controlling the excavation parameters, which are penetration force and rotational speed, enables an efficient excavation according to ground characteristics.

DOI： 10.1109/AIM43001.2020.9158934

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Other Link： https://dblp.uni-trier.de/db/conf/aimech/aim2020.html#ToyamaITWOYN20

Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Various haptic devices for application to virtual reality have been developed. Most of them have to be stationary on a desk, thus users cannot move around. To overcome this shortcoming, exoskeletal haptic devices have been developed. However, they also have shortcomings such as discomfort caused by the reaction force of the presented haptic force in another part of the body. In addition, the limited range of motion caused by exoskeleton structure is also a problem. Therefore, in this research, we propose a wearable device without an exoskeletal structure that uses airjet to provide force feedback. In this study, ω-jet, a prototype for the finger joints, was developed, and its basic characteristics were evaluated. Moreover, the prototype was evaluated based on its performance in an elastic ball presentation experiment. The results confirmed that the proposed device was capable of rendering virtual balls of different sizes and stiffness.

DOI： 10.1109/AIM43001.2020.9158981

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Other Link： https://dblp.uni-trier.de/db/conf/aimech/aim2020.html#OkuiMTON20

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In order to prevent accidents caused by the aging of sewer pipes, it is necessary to identify the state of the pipe as well as the damage position. A pipeline diagram is required to specify the location of the damage, but pipeline diagrams are often lost. Therefore, it is necessary to measure the pipeline shape and create a pipeline diagram. We developed a robot for sewage pipe inspection that mimics the movement method of earthworms. In this paper, we propose a method for estimating the pipe shape from an inertial measurement unit (IMU) sensor mounted on the developed robot with peristaltic motion. The pipe shape is realized by a combination of distance measurement using acceleration and changes in angular velocity, and bending pipe discrimination using changes in the attitude angle of the sensor. To solve the problem in which a cumulative error occurs when the acceleration is second-order integrated in the distance measurement, the cumulative error was corrected in consideration of the periodicity of the progression and stops during the peristaltic motion; this is a unique movement method of this robot. In bending pipe discrimination, a bending pipe and a straight pipe were distinguished based on changes in the angular velocity, and the angle of the bending pipe was judged from the attitude angle of the sensor. The developed robot with an IMU was crawl on a pipe composed of multiple bending pipe and inclined pipe for pipe rise, and the pipe shape was estimated using the proposed method. In the experiments, it was possible to measure the length of the pipeline with an error of 1.42 % relative to the actual length, and it was possible to express the approximate shape of the pipeline.

DOI： 10.1109/AIM43001.2020.9158972

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Other Link： https://dblp.uni-trier.de/db/conf/aimech/aim2020.html#SatoMIYONN20

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

A variable viscoelastic joint was developed that mimics the principle of human joint drive and uses a pneumatic artificial muscle with an antagonistic arrangement and a magnetic viscous fluid brake. Herein, the versatility of this joint was improved via modularization. The variable viscoelastic joint module is the world's first pneumatic drive module with an internal power source and variable viscoelastic characteristics.

DOI： 10.1109/AIM43001.2020.9158861

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Other Link： https://dblp.uni-trier.de/db/conf/aimech/aim2020.html#MachidaKSYON20

Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

A peristaltic continuous mixing conveyor that focuses on the mechanism of the intestine has been developed as a technology for the mixing and transport of a solid-liquid mixture and high viscosity fluids. The developed peristaltic continuous mixing conveyor succeeded in the mixing and transport of such mixtures in a previous study. A simple cyclic pattern is currently used as the movement pattern of the system, and the control method can be further improved. In this study, we aim to realize an intelligent mixing and generation of a conveyor pattern based on intestinal movement. The mixing state of content during activation was estimated through machine learning. The results from the time-series measurement data show that an internal mixing state in three units of the peristaltic continuous mixing conveyor was estimated.

DOI： 10.1109/RoboSoft48309.2020.9116058

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Other Link： https://dblp.uni-trier.de/db/conf/robosoft/robosoft2020.html#WakamatsuIHAMKN20

Publishing type：Research paper (international conference proceedings)  

This study proposes the development of a locomotion robot using a deformable dielectric elastomer for actuation without pre-stretch. Electroactive polymers (EAPs) that are driven by electrical stimulation have recently garnered attention. Among EAPs, dielectric elastomer actuators (DEAs) are focused herein. DEAs have a structure wherein a dielectric is sandwiched between elastic electrodes. The performance of the DEA depends on the relative permittivity, Young's modulus, and the applicable voltage of the dielectric material. DEAs are usually used with pre-stretching, because of the material properties of the dielectric, which requires a large stress in the initial stage of extension, and the increase in the displacement of DEAs with the application of pre-stretch. However, because rigid frames are generally used for prestretching, there are few DEA applications that utilize their flexibility. Therefore, we focused on slide-ring materials (SRMs) as new dielectric materials. SRMs are polymer materials in which the cross-linking points move freely, and having excellent properties as dielectrics for DEA applications. Thus, pre-stretching is not required, and applications utilizing the flexibility of DEAs is possible. In previous research, a bending unit that did not require pre-stretching was manufactured by attaching non-stretchable tape to one side of the DEA using an SRM as the dielectric material. In addition, a locomotion robot with a bending unit was developed, and it was confirmed that the robot achieved locomotion because of a phase difference between the units. However, the basic characteristics of the bending unit and locomotion robot were not discussed. Therefore, in this research, we measured the frequency characteristics of the bending unit alone and demonstrated the locomotion of the robot.

DOI： 10.1117/12.2558422

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Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Actuators known as pneumatic artificial muscles are superior for practical use because they do not require maintenance, are inexpensive, and can be assembled with a drive unit and an energy generation unit independently. However, because these actuators expand greatly in the radial direction when pressurized, one problem is that they occupy a large amount of space and consume a significant amount of flow. In this study, we propose a space-saving, constant-axis fiber-reinforced artificial muscle that does not expand and also takes advantage of the benefits of pneumatic artificial muscles. Hence, this paper reports on the driving principle of the proposed noninflatable pneumatic artificial muscle and the basic characteristics are then confirmed using a prototype.

DOI： 10.1109/SII46433.2020.9026201

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Other Link： https://dblp.uni-trier.de/db/conf/sii/sii2020.html#OkuiIKN20

Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Mineral resources have been discovered on the bottom of the ocean; to utilize them, seabed soil samples must be obtained and analyzed. This study aimed to develop a seafloor robotic explorer that can excavate and gather samples of the seafloor soil. In our previous study, we developed a drilling robot named SEAVO II that could excavate 430 mm into the sand ground underwater. However, in the present study, the target to be excavated was the rare earth mud layer. Therefore, we examined the drilling properties specific to the underwater clay ground. In addition, a drilling experiment in the clay ground was conducted using SEAVO II. The results showed that SEAVO II could successfully dri11430 mm into the clay ground underwater.

DOI： 10.1109/SII46433.2020.9026231

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Other Link： https://dblp.uni-trier.de/db/conf/sii/sii2020.html#IsakaTWTOYN20

Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Force feedback devices are attracting attention as a way to apply virtual and augmented reality to entertainment, sports, and rehabilitation. We previously developed a force feedback device using pneumatic artificial muscle and a magneto-rheological fluid clutch. However, problems occurred, such as an increase in the weight of the device and complications in the control system. To solve these problems, a new force feedback method using an elastic spring and a magneto-rheological fluid clutch was therefore proposed. In addition, the force feedback characteristics of the force feedback method were modeled. A 1-degree-of-freedom force feedback device using the new force feedback method was also developed. The model characteristics of the force feedback for rendering the elasticity using the device were confirmed experimentally.

DOI： 10.1109/SII46433.2020.9025927

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Other Link： https://dblp.uni-trier.de/db/conf/sii/sii2020.html#OobaOON20

Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this paper, we describe the performance of a pneumatic artificial muscle integrally molded by a 3D printer that can mold materials with different stiffnesses.In the recent years, soft and hard materials can be integrally molded as the performances of 3D printers improve. For this reason, attention has been focused on the integral molding of actuators by using 3D printers. In this study, an artificial muscle is integrally molded by a state-of-the-art 3D printer, and the amount of contraction and contraction force generated are experimentally measured. In particular, the integrally molded artificial muscle formulated in this study is a pleated artificial muscle that does not require high material stretching performance. When the stiffness of the leaf spring material constituting the 3D printable artificial muscle is changed in a stepwise manner, the generated contraction amount and force were measured. From these measurement results, the usefulness of this actuator was confirmed by comparing the generated force with that of a pneumatic piston with the same inner diameter.

DOI： 10.1109/SII46433.2020.9026165

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Other Link： https://dblp.uni-trier.de/db/conf/sii/sii2020.html#ItoKON20

Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

We attempt to generate traveling waves by applying a dielectric elastomer actuator (DEA) with a sliding ring material (SRM). A normal DEA using silicon or acrylic rubber requires pre-stretching with a rigid frame to obtain a large displacement, owing to the material properties of the dielectric, which require a large stress to be applied at the initial stage of the extension. A DEA using an SRM does not need to be restricted by a rigid frame and can be expected to generate large displacements and complex motions while maintaining its flexibility. In this paper, we report the development of a traveling wave generator as an initial study. Through experiments, the developed DEA was confirmed to function as an actuator without pre-stretching. In the future, in addition to determining the optimum phase difference, frequency band, and shape of the constrained parts to increase the speed, we plan to develop a mobile robot utilizing a DEA traveling wave with a mechanism that would allow the units to overlap.

DOI： 10.1109/SII46433.2020.9026285

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Other Link： https://dblp.uni-trier.de/db/conf/sii/sii2020.html#HayashiKOYTN20

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

Seabed mineral resources have been found on the bottom of the ocean, and to utilize them, samples must be taken and analyzed. This study develops a seafloor robotic explorer that can excavate and sample seafloor soil. In a previous study, we developed a drilling robot that could excavate 430 mm into the ground while underwater. However, excavation deeper than 430 mm was not possible because the discharging outlet became buried, making it difficult to discharge the drilled soil. In this paper, we develop a discharging mechanism utilizing water jetting to improve the excavation depth to 650 mm and potentially deeper.

DOI： 10.1109/ACCESS.2020.2972572

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Language：Japanese   Publisher：The Robotics Society of Japan  

In recent years, the aging of pipelines has been severe and has caused fatal accidents. The pipe diameters are small, and the layouts are complex. Pneumatically driven mobile robots have become popular as inspection methods. Various types of robots have been studied, like earthworm-type robots, inchworm-type robots, and spiral-tube-type robots. Typically, they make periodic movements; however, they have challenges because they are driven by existing pneumatic valve technologies, which are limited to small mobile robots. Small pneumatic valves have low flow rates and limit the performance of pneumatic actuators. Therefore, we focused on the structure of the ball valve and periodic motion. Furthermore, in this paper, we developed the Compact Rotary Valve Mechanism for pneumatic mobile robots in pipe inspection, which generates periodic air pressure.

DOI： 10.7210/jrsj.38.965

DOI： 10.20965/jrm.2023.p0633_references_DOI_GrMm5ygjFtfynoUzZ62TOKgGCeZ

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In the study, we propose a negative-pressure-driven soft linear actuator for the fixation part of an exoskeleton. In the study, a concept of the fixation part that is easy to wear with reliable force transmission is first proposed. Subsequently, a negative-pressure-driven soft linear actuator for the proposed fixation method is introduced and prototyped. Finally, basic characteristic experiments are conducted with a prototype. The results indicate that decreases in the pressure increase the actuator's contraction force and maximum contraction. It exhibits a large hysteresis that is approximately 50% at maximum contraction force. Increases in the width increase the contraction force. Increases in the height increase the force and rate of contraction.

DOI： 10.13180/clawar.2020.24-26.08.30

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：FUJI TECHNOLOGY PRESS LTD  

In recent years, the burden per worker has increased due to a decrease in the working population. Wearable assist suits have been developed as one of the methods for solving the problem. To extend the assist suit to practical situations, it is necessary to provide a motion judgment interface for judging the motion of a wearer. Therefore, in our study, a motion judgment algorithm is proposed for assist suits, based on variable viscoelasticity. The proposed algorithm judges sitting, standing-up, stance, sitting-down, and gait using only the joint angle information of the suit and verification is performed using human joint angles obtained by motion capture. Thus, the motion judgment rate is 90% or more for sitting, standing-up, stance, and sitting-down, and 80% or more for gait, confirming the usefulness of motion judgment. Additionally, based on these results, further verification is performed on an actual machine. As a result, in a series of motions starting from the sitting to the standing-up, the stance, and the gait, the motion judgement is successful five times from the sitting to the standing-up, the stance, and once in gait. In a series of motions from sitting to standing-up, the stance, and sitting-down, the motion judgment is successful five times during sitting; five times during sitting, stance, and sitting-down; and three times during standing-up. In this way, it is confirmed that the proposed method can judge the motion only by angle information, although there is a problem in a success rate depending on the motion.

DOI： 10.20965/jrm.2020.p0863

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this paper, we propose an assistance method that controls joint stiffness and the antagonized angle using variable elastic elements. The proposed system changes the stiffness and angle so that they correspond to the phase of movement and performs movement assistance in cooperation with the wearer. To achieve structural variability in the configuration of stiffness and the antagonized angle, we propose a joint structure in which the artificial muscle and tension spring are antagonistically arranged. While performing a movement, motion analysis was conducted to investigate the change in joint stiffness and antagonized angle. We confirmed that the proposed joint and human joint have the same tendency while in motion.

DOI： 10.1109/ICAR46387.2019.8981664

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELSEVIER  

Copyright © 2019. The Authors. Published by Elsevier Ltd. All rights reserved. In this study, an experiment is conducted to evaluate a squat motion while using the wearable variable viscoelastic assistive suit “Airsist I,” and the assistive effect of the suit is confirmed. Wearable assistive suits help in reducing the burden on laborers. Airsist I was developed in a previous study, based on the characteristics of variable viscoelasticity. In addition, a variable viscoelastic control strategy was proposed. However, an evaluation has not been performed to confirm the assistive effect of Airsist I. Therefore, this study reports on the confirmation of the assistive effect of the variable viscoelastic suit Airsist I.

DOI： 10.1016/j.ifacol.2019.11.050

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Copyright © 2019. The Authors. Published by Elsevier Ltd. All rights reserved. In the shipbuilding industry, welding is one of the forms of nonautomated heavy labor, and the welding operator is required to weld indeterminate objects in a narrow working space. Therefore, it is difficult to use large equipment, such as industrial robots. In addition, it is not easy to perform high-quality welding, because tracing a welding line accurately at a constant speed requires a long training period. In this research, the aim was to develop a welding assist device that can be applied to a welding environment. The proposed device fixes to the welding surface by magnetic force and assists semiautomatic welding with a magnetorheological (MR) brake. MR brakes have a sufficient response speed compared with powder brakes, have a large output weight ratio, and are considered to be suitable for welding assistance. In this work, a strategy for control of path rendering and speed restriction by MR brakes is proposed. Its effectiveness was confirmed by experiments with a prototype.

DOI： 10.1016/j.ifacol.2019.11.057

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Using a head-mounted display, users can immerse themselves in virtual reality space and users can via the visual recognition of virtual objects. However, users do not experience the same haptic perception when they interact with these objects, that they do with actual objects. Force feedback devices can render haptic perception. They are classified into desktop and wearable types. A wearable 1 degree of freedom force feedback device using magnetorheological fluid brake, magnetorheological clutches, and pneumatic artificial muscles has been previously developed and it was confirmed that the device can render elasticity, friction, and viscosity. In addition, a wearable 4 degrees of freedom force feedback device using magnetorheological fluid clutches and pneumatic artificial muscles that can render elasticity was also previously developed. However, it was not established that the device could render friction, and viscosity using magnetorheological fluid clutches and pneumatic artificial muscles. In this report, it is confirmed that such a device can render friction and viscosity using magnetorheological fluid clutches and pneumatic artificial muscles without the need for magnetorheological fluid brake.

DOI： 10.1109/IECON.2019.8927514

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

Currently, researchers are actively conducting studies and experiments on soft robots due to their increasing abilities to cooperate with humans. Particular attention is being paid to pneumatic artificial muscles because of their flexibility and relatively light weight as actuators. Among the multiple types of pneumatic artificial muscles, the straight-fiber-type has a structure, which is typically configured in a cylindrical rubber tube reinforced by fibers in the axial direction. The application of an internal pressure expands the tube in the radial direction, while it contracts in the axial direction. In this study, the deformation of such tubes was theoretically analyzed. First, the differential equation for the cylinder profile was derived, and the solution then obtained in the closed form, when the rubber is relatively soft enough compared to the fiber. Finally, for a large enough inner pressure, the profile of the reinforced rubber cylinder was derived from the incomplete elliptic integral. Moreover, the spring constant, the contraction ratio, and the maximum stress were obtained regarding the cylinder length. The spring constant linearly increased with the initial length of the cylinder. The contraction ratio also increased with the initial cylinder length up to 54.3%. The maximum stress was found to be related to the elastic modulus of the rubber but not to the inner pressure; when the cylinder length was three to five times larger than the initial diameter of the cylinder, the rubber exhibited small a maximum stress and large contraction ratio.

DOI： 10.1109/LRA.2019.2902016

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this study, we made the assumption that the feeling of a firm handshake is related to the stiffness of the elbow joint and we performed handshake experiments under variable stiffness conditions to verify the assumption. EMG signals were recorded to be used as an evaluation. Then human-robot handshake experiments were performed utilizing a handshake manipulator proposed in the previous research. The joint of the manipulator was driven by antagonized artificial muscles, which are considered to be soft actuators designed to mimic the movement of real human muscles. The muscle activations of the subject were compared when the subject shook hand with the experimenter and the manipulator. And it has been demonstrated that even though the subject was not aware of the experiment conditions, the muscle activations are higher in the firm handshake condition in both human-human handshake and human robot handshake experiments, which indicated that firmness of handshakes are related to the stiffness of the joint and the EMG signals can used as an evaluation method.

DOI： 10.1109/ICARM.2019.8833897

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

Force-feedback devices, along with virtual reality, are being studied for applications related to entertainment and rehabilitation. These devices generally comprise either direct drive motors or motors with reduction gear. However, suitable force feedback with high stiffness requires high-power and very large motors with reduction gears. Although rigidity can be increased with reduction gears, they reduce back-drivability and limit the motion freedom of the device. To address these problems, we developed a force-feedback device actuated with a magnetorheological clutch and pneumatic artificial muscles. The device can smoothly vary its stiffness and viscosity, and provides good back-drivability. In this paper, we report the development and testing of a prototype with one rotational and three translational degrees of freedom. We evaluated the effectiveness of force feedback per degree of freedom, and the prototype being used to resemble lid opening.

DOI： 10.1088/1361-665X/ab192a

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

In this study, a handshake manipulator with variable viscoelastic joints was proposed. The variable viscoelastic joint system comprised of antagonized artificial muscles and a magneto-rheological fluid brake. This joint system resembles the characteristic of real human joint. The objective of this study is to evaluate the proposed manipulator's effectiveness in the research of human-robot physical interaction and to verify that by adjusting the viscosity and stiffness of the joint it is possible to create handshakes with different feelings. In this research two sets of experiments were conducted; the first set of experiments was to conducted on the manipulator alone in order to test the performance of the manipulator. And the second set of experiments was the subjective evaluation of the manipulator when subjects shook hand with the manipulator under variable viscosity and stiffness conditions. The results of these experiments indicated that the manipulator was suitable for doing research on human-robot handshake, and the variable viscosity and stiffness of the elbow joint did create distinctive feelings to the subjects.

DOI： 10.1088/1361-665X/ab0d9b

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Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Dielectric elastomer actuator (DEA) is a soft actuator with low manufacturing cost and high energy efficiency; it expands when an electric field is applied. The structure of DEA comprises a dielectric material interlayered with elastic electrodes similar to a sandwich. The performance of DEA is determined by the material of the dielectric layer, which is generally silicon or acrylic rubber. This study focused on investigating the characteristics and various applications of slide ring material (SRM) as a dielectric. SRM is more suitable for use as a dielectric of DEA as compared to silicone and acrylic rubbers in terms of the dielectric constant and hysteresis loss. Several measurement methods of existing DEAs measure only uniaxial deformation. However, the actual DEA strain distribution is not completely uniform. In addition, obtaining the two-dimensional (2D) strain distribution leads to a better understanding of the lifetime and performance of DEA as DEA deforms in 2D practical applications. Therefore, this study measured the strain on the DEA, while changing the load, applied voltage, and number of layers, using the image correlation method, which is a 2D planar measurement method. This measurement confirmed the two-dimensionally spreading strain distribution. The relationship between the stress, strain, and number of DEA layers was also obtained.

DOI： 10.1109/SII.2019.8700353

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A dielectric elastomer actuator (DEA) is a soft actuator with low manufacturing cost and high energy efficiency. The structure of a DEA consists of a dielectric material interlayered with elastic electrodes, and DEA expands when an electric field is applied. The degree of freedom of movement of the DEA can be increased by devising the electrode arrangement in DEA. The performance of DEA is determined by permittivity, Young's modulus, and applicable electric field. Material properties including hysteresis loss are also important when a DEA is used as a sensor or high precision actuator. Generally, silicon and acrylic rubbers are used as the dielectric layer. This study focused on the use of a slidering material (SRM) as a more suitable dielectric for DEA than silicone and acrylic rubbers in terms of its dielectric constant and hysteresis loss. In a previous study, a DEA was developed using SRM as a dielectric, and the image correlation method (ICM) was applied to measure the strain distributions in a two-dimensional plane and the basic characteristics of DEA with one pair of electrodes. Here, the strain distribution was measured when the electrodes of the DEA were segmented into several pairs as the next step in the investigation of its basic characteristics. Patterns of electrode arrangements and the amount of DEA prestretching were changed, and strain distribution was measured using ICM.

DOI： 10.1117/12.2514194

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Language：Japanese   Publisher：The Japan Fluid Power System Society  

<p>Pneumatic rubber artificial muscle is attracting attention as an actuator having high cooperativeness with human because of its feature of being flexible and lightweight. The authors have developed Straight fiber type pneumatic artificial muscle (SF-ARM), which is a high power, highly displaced pneumatic rubber artificial muscle. Although SF-ARM has excellent contraction characteristics, it has a problem of short fatigue life. Therefore, in this study, focusing on strain-induced crystallization of natural rubber, the fatigue life of SF-ARM has been extended. First, strain-induced crystallization of natural rubber were confirmed by wide angle X-ray diffraction. Next, analysis of strain concentration in the vicinity of the crack was performed by the finite element method. Finally, a fatigue life test of SF-ARM was carried out to confirm the effect of prolonging the fatigue life by using strain-induced crystallization.</p>

DOI： 10.5739/jfps.50.46

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Various types of soft actuators have been developed for application in wearable movement-assist devices or soft robots. The authors have developed a straight-fiber-reinforced pneumatic rubber artificial muscle (SF-ARM). The SFARM is composed of rubber that is reinforced with fibers aligned only in the axial direction. When air pressure is applied to the SF-ARM, the reinforced fibers limit the rubber expansion to the radial direction so that the muscle contracts in the axial direction. The SF-ARM contracts by 38% at maximum, and this contraction rate exceeds the contraction rate of the McKibben artificial muscle. However, the SF-ARM is not well-suited for practical use because the strain on the SF-ARM while it is actuated is large which can cause fatigue failure of the rubber. This study focuses on suppressing the growth of cracks using strain-induced crystallization of the natural rubber, to prolong the lifetime of the SF-ARM. Natural rubbers form a crystalline layer in the direction perpendicular to the direction of stretching. This crystal layer effectively suppresses the growth of cracks in the SF-ARM when under strain. Deliberately developing a crystal layer should extend the lifetime of the SF-ARM. First, this study confirmed the formation of a crystal layer under extension of natural rubber (NR) and styrene butadiene rubber (SBR) using wide-angle X-ray diffraction measurements. Next, the strain concentration near the crack was analyzed using finite element method simulations. Finally, fatigue-life tests were conducted with SF-ARMs made of NR and SBR.

DOI： 10.1117/12.2513246

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Pneumatically driven wearable assistive devices for walking have been developed recently. These devices can achieve flexible assistance without control; however, they require large and heavy air compressors for activation. In this study, a pneumatically driven source using vibration energy regeneration from walking was developed. The aim was to activate the cylinder using vibrations due to walking and compressed air. A mass element, which is connected to a human body via a spring and a cylinder, vibrates along with the human gait cycle. Next, a prototype was developed and tested. In walking experiments, stored pressure was measured at several gait cycles and masses for comparison. Results indicate that the gait cycle period and masses affect the stored pressure; the highest pressure recorded was 0.08 MPa.

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Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Pneumatic soft actuators has been developed to improved characteristics, such as operating flexibility, low weight, and high output etc. However, the application range of these artificial muscles has been limited by their fragility, the size of pneumatic source and the system size required to control the position and force. Therefore, this research proposes hollow artificial muscles with air cylinder that is high durability and driven with less air. Furthermore, this actuator control both stiffness and displacement independently as single mechanical element.

DOI： 10.1109/BIOROB.2018.8487219

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This paper presents a socks type wearable soft actuator driven by pneumatics: Motion Socks, aimed to provide exercise for both ankle and toes automatically and safely. The goal of this project is to prevent the symptom of DVT (Deep Vein Thrombosis) which tends to arise for the elderlies lying on the bed for a long time. To improve the blood circulation effectively, two design methods are proposed. One is the desirable design of soft pneumatic actuators to provide exercise, which enables the force vector to act on the instep of the foot perpendicularly in order to reduce the load on the foot. The other is a limiter as the safety function to prevent undesirably large force from acting on ankle and toes, which is composed of magnets and hinges to detect the load, and a tube type valve to exhaust. The validity of the proposed methods is verified through the experiment, which shows the developed Motions Socks could effectively improve the blood flow.

DOI： 10.1109/AIM.2018.8452682

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© 2018 IEEE. A pneumatic artificial muscle is an air pressure-activated rubber actuator. It is lightweight and high in power density compared to motorized actuators and fluid-powered cylinders. In addition, it shows high compatibility with the human body because it has good flexibility. The authors have developed a straight-fiber-type pneumatic artificial muscle (SF-ARM) with high output and contraction amounts compared to those of the widely used McKibben-type artificial muscle. Although the fatigue life of the McKibben type has been examined, similar studies have not yet been performed for SF-ARM. In this study, the extension of the lifetime of SF-ARM, development of high-deformation rubber material, and examination of the SF-ARM aspect ratio were performed. First, from deformation analysis by the finite element method, the target elongation value of the rubber material was determined and a suitable material was developed. Next, the fatigue life and contraction characteristics were measured by reducing the strain of the rubber material by changing the aspect ratio. The results showed a relationship between the lifetime and the shape of the artificial muscle. We demonstrate that the relationship between the lifetime and contraction force and ratio, according to the application, can be selected by manipulating the shape and the size of the SF-ARM.

DOI： 10.1109/ROBOSOFT.2018.8404918

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© 2018 IEEE. This paper reports on an improvement to a feedforward controller for a straight-fiber-type artificial muscle that can control the amount of contraction, stiffness, and contraction force by use of an experimental identification model. This straight-fiber-type artificial muscle has a higher contraction force and a higher contraction rate than a McKibben artificial muscle. In a previous study, we developed a feedforward controller for a straight-fiber-type artificial muscle based on a mechanical model. However, this controller could not accurately control the stiffness or the contraction force. A feedback controller was necessary to compensate for the lack of feedforward control accuracy, which increased the system complexity. In addition, the calculations of the previous controller were so complex that the microcontroller could not keep up with the sequential calculations. This is not practical when the controller is used in devices such as an assist suit. In this paper, to solve these problems, we propose a novel feedforward controller based on an experimental identification model whose calculations are simpler than the previous ones. An experimental identification model enables the feedforward controller to improve the accuracy by identifying the parameters used in the model. Also, we compare the accuracy of the proposed controller with the previous one.

DOI： 10.1109/ROBOSOFT.2018.8404893

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

This letter proposes a novel hybrid pneumatic power source for the development of a portable pneumatic source. The hybrid pneumatic source achieves a lightweight system by combining two pneumatic sources: one that can generate high pressure/small suppliable flow and one that can generate small pressure/large suppliable flow. In this study, first, the mobility of various pneumatic sources is evaluated by experiments. The evaluation methods involve a small battery-driven compressor, tank, phase change of material, and chemical reaction. From the results, it is clarified that there is no best method because each method has advantages and disadvantages. Then, a hybrid pneumatic source utilizing the result is proposed. Finally, a prototype that has phase change of CO2 and dimethyl ether as a pneumatic source is developed, and the effectiveness of the proposed method is confirmed by experiments.

DOI： 10.1109/LRA.2018.2792145

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SAGE Publications Ltd  

In this study, a variable viscoelastic joint system with a clutch for human assistance was proposed. The variable viscoelastic joint system comprised antagonized artificial muscles and magneto-rheological fluid brake. This system enabled the human assisting device, such as exoskeletons, to retain structural softness when compared with the existing devices driven by motor and reduction gear, which could only achieve superficial softness. In addition, a clutch system that provided high back-drivability to the wearer by structurally separating the device from the wearer was proposed. As an initial step in designing the human assisting device, a prototype with the proposed variable viscoelastic joint system for knee assistance is developed. Also, its control method was developed. Furthermore, experiments were conducted to confirm the influence of the proposed viscoelastic joint system and control method on the wearer.

DOI： 10.1177/1045389X17705216

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Language：Japanese   Publisher：The Robotics Society of Japan  

This paper proposes a novel hybrid pneumatic power source for a development of a portable pneumatic source. The hybrid source achieves light weight system by combination of multiple pneumatic sources. This paper is divided as follows. Firstly, the mobility of various pneumatic sources are evaluated by experiments. Evaluated methods are a small compressor driven by battery, tank, phase change of material, and chemical reaction. From the results, it was clarified that there is no best method since each method have advantages and disadvantages. Secondly, hybrid pneumatic source is proposed utilizing the result. Finally, a prototype is developed and the effectiveness of the proposed method is confirmed by experiments.

DOI： 10.7210/jrsj.36.233

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Language：Japanese   Publisher：The Society of Instrument and Control Engineers  

Recently, many devices driven by pneumatic actuators have been developed. In additions, many researches on pneumatic artificial muscles focusing on characteristics such as flexible operation, light weight and high output have been conducted. These artificial muscles were limited in their application range due to their durability and the necessity of an air pressure source. Therefore, in this research, as another approach apart from the improvement of the air pressure source device, we propose hollow artificial muscle with high efficiency and high durability.

DOI： 10.9746/sicetr.54.557

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

A pneumatic artificial muscle is a rubber actuator activated by air pressure. It is lightweight and has the high power density compared to other actuators such as motors and fluid powered cylinders. In addition, it can provide high compatibility with human since its flexibility. Authors have developed the Straight-fiber-type pneumatic artificial muscle which has high output and high contraction amount compared to the McKibben type artificial muscle that is widely used. However, the lifetime of the Straight-fiber-type pneumatic artificial muscle has not been considered so far. In this paper, effects of aspect ratio and materials on the lifetime of the artificial muscle are examined for prolonging the lifetime. Firstly, the desirable maximum stretch rate of the material is developed. Secondly, fatigue life is measured by reducing the elongation of the rubber material by changing the aspect ratio of length and inner diameter in the SF-ARM. Finally we measure the influence on the output characteristics by changing aspect ratio. The result shows relationship of the lifetime and the aspect ratio of the artificial muscle. We showed that the artificial muscle’s lifetime and contraction characteristics can be selected according to the application.

DOI： 10.1299/transjsme.17-00299

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Language：Japanese   Publisher：The Robotics Society of Japan  

<p>Recently, assisting human motion with a wearable robot is studied widely. These assisting systems are proposed from various points of view. Our study has proposed an assisting system that the torque, angle, and the viscoelasticity of the joint are variable because the human muscle has the characteristic of variable viscoelasticity. This system consists of antagonized muscle that the stiffness is variable and magneto-rheological fluid brake that the viscosity is variable. Therefore, the system enables the wearable assistive device such as exoskeletons to be structurally soft and to provide the wearer with a high back-drivability. We have proposed the assisting method by changing the viscoelasticity of the device joint according to the viscoelasticity of wearer's muscle. But suitable viscoelasticity of the joint for the assistive motion is not well known. In this paper, an experiment is conducted to examine how the viscoelasticity of the joint affects to human motion when assisting. Also, based on the results from the experiments, we propose the control method for the joint viscoelasticity of the device that responds to the assistive motion and confirm the effects with the experiments. </p>

DOI： 10.7210/jrsj.36.567

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DOI： 10.1109/ROBOSOFT.2018.8404893

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Language：Japanese   Publisher：一般社団法人 日本機械学会  

&lt;p&gt;The cylindrical rubber is axially reinforced by the fiber and closed by the rigid ends. When the inner pressure is applied to this fiber reinforced rubber cylinder, the diameter expands and the length shrinks. Such the cylinder can be used as the soft actuator, that is, the artificial muscle. In this paper, this problem is analyzed theoretically. Firstly, the differential equation, which is satisfied the cylinder&#039;s profile, is derived. Secondary, the solution is obtained as the closed form, when the rubber is soft enough compared to the fiber. Finally, it is found that the profile of the rubber cylinder is given by the incomplete elliptic integral, when the inner pressure is large enough. Moreover, the spring constant, the contraction ratio and the maximum stress are obtained with respect to the length of the cylinder. The spring constant is linearly increasing with the inclement of the initial length of the cylinder. The contraction ratio is increasing with the inclement of the initial length of the cylinder and converged to 54.3%. The maximum stress is related to the elastic modulus of the rubber and is not related to the inner pressure. When the length of the cylinder is through three to five times larger than the initial diameter of the cylinder, the rubber has the small maximum stress and the large contraction ratio.&lt;/p&gt;

DOI： 10.1299/transjsme.18-00351

DOI： 10.1299/transjsme.21-00290_references_DOI_9BBAHHSD7Dm6U1R0heJSGo5sD4X

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Pneumatic soft actuators has been developed to improved characteristics, such as operating flexibility, low weight, and high output etc. However, the application range of these artificial muscles has been limited by their fragility, the size of pneumatic source and the system size required to control the position and force. Therefore, this research proposes hollow artificial muscles with air cylinder that is high durability and driven with less air. Furthermore, this actuator control both stiffness and displacement independently as single mechanical element.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE Computer Society  

A body fixing method for wearable assistive devices was proposed that utilized jamming transition and the expansion of an elastic bag. The proposed fixing part comprised a jamming layer, a rubber bag, and other components. The jamming layer deformed due to the application of pressure to an elastic bag. Then, it hardened due to negative pressure. In this research, we described the configuration and movement of the proposed method and conducted a sensory evaluation using a prototype.

DOI： 10.23919/ICCAS.2017.8204222

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Electrical and Electronics Engineers Inc.  

A range of pneumatically-driven devices have been developed. However, these require a large air compressor, making them heavy, bulky, and therefore inappropriate for use in portable devices. In this study, we proposed and tested a portable pneumatic power source using the chemical reaction between sodium bicarbonate and citric acid. The carbon dioxide generated in the reaction was used as a pneumatic power source. The chemicals used are inexpensive, nontoxic, and readily available. From the result of basic experiment demonstrated in this paper, we conclude that the method can provide enough high pressure (more than 1 MPa) for activating pneumatic actuators and the chemical reaction is safe since it is endothermic reaction. We also demonstrated a novel system that provides continuous mixing of the reagents, using a pressure booster. The system keeps a pressure inside of a tank moderate, and tank can become light weight because it doesn't need to endure high pressure.

DOI： 10.1109/IROS.2017.8202272

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Electrical and Electronics Engineers Inc.  

In this study, a variable viscoelastic joint system comprising antagonized artificial muscles and magneto-rheological fluid brakes is proposed. This system enables human assisting devices such as robotic exoskeletons to retain structural softness when compared with the existing devices driven by motors and reduction gears, which can only achieve superficial softness. The authors had proposed the system and showed its effectiveness via experiments using a prototype with one degree of freedom in their previous works. In this study, as the next step in designing the human assisting device, a lower body assistive prototype 'Airsist' is introduced. In addition, a control method that can cooperate with the wearer without the need for an additional operation is proposed.

DOI： 10.1109/IROS.2017.8206242

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In recent years in Japan, over half of all workers suffered from lower back pain. This has become a social problem that needs to be addressed. To reduce its occurrence, we developed a flexible, high-output waist assist suit called 'AB-Wear' in a previous study. The AB-Wear suit can assist human motion and reduce muscular fatigue of the waist. However, the assistive forces of the device generate compressive forces on the backbone, which have adverse effects on the body. Hence, in this study, we propose an exoskeleton-type AB-Wear equipped with a compressive force reduction mechanism, called 'semi-endoskeleton-type AB-Wear'. This device has a reduction mechanism similar to a flexible flat spring behind the upper body. Because of this structure, this device can generate an effective assistive force. First, we explain the difference between the semi-endoskeleton-type AB-Wear and the previous device. Then, we model the semi-endoskeleton-type AB-Wear because the model is used for its operation. Moreover, its effectiveness is confirmed using musculoskeletal simulation. Finally it is evaluated by measuring surface electromyography (EMG) on a subject's body to confirm its effectiveness with a real body. The EMGs of the wearer with and without the suit are compared. The usefulness of the AB-Wear is confirmed by simulation and experiment.

DOI： 10.1109/ICRA.2017.7989711

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Language：Japanese   Publishing type：Research paper (international conference proceedings)   Publisher：The Japan Society of Mechanical Engineers  

Pneumatic driven systems are widely used in various fields. Recently, it is applied to wearable assist systems since it is lightweight, high-power and retains structural softness. To activate these pneumatic actuators, air compressor which is driven by large motors or engine is used generally. These heavy and large systems prevent pneumatic systems from being portable. If portable pneumatic power source were developed, pneumatic system could be used in wider fields. Thus, in this study, we aim to develop portable pneumatic power source that is enable to withstand practical use. As an initial step, various air compressing methods are evaluated in terms of portability in this paper. Methods to compare are small compressor activated by battery, phase change of material a chemical reaction.

DOI： 10.1299/jsmermd.2017.2p1-d02

DOI： 10.20965/jrm.2018.p0752_references_DOI_9NQpVoc1kai9cqGTk8y6cAuNg3d

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

A body fixing method for wearable assistive devices was proposed that utilized jamming transition and the expansion of an elastic bag. The proposed fixing part comprised a jamming layer, a rubber bag, and other components. The jamming layer deformed due to the application of pressure to an elastic bag. Then, it hardened due to negative pressure. In this research, we described the configuration and movement of the proposed method and conducted a sensory evaluation using a prototype.

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Language：Japanese   Publisher：The Japan Fluid Power System Society  

This paper is concerned with portable pneumatic power source using chemical reaction of sodium bicarbonate and citric acid. Carbon dioxide generated in the chemical reaction is used as the compressed air. Both sodium bicarbonate and citric acid are inexpensive, nontoxic, and readily available. This paper is organized as follows. Firstly, the characteristics of the chemical reaction is surveyed and the appropriate pneumatic power source system is discussed. Secondly, a pressure booster that can achieve a stable air generation system without external power is described. Thirdly, the experiment using the prototype system is conducted to confirm the effectiveness of the proposed method.

DOI： 10.5739/jfps.48.17

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In this paper, permissible resistant torque considering back-drivability is verified to develop a wearable assist suit (WAS). The WAS has a clutch and a variable viscoelasticity joint. In this paper, permissible resistant torque is defined as torque that is acceptable in daily use. As first stage of the WAS development, the paper discusses the relationship between the resistant torque to the knee and the degree of discomfort experienced by the wearer as evaluated through a survey questionnaire experiment. In addition, the influence of the resistant torque on a muscle of the knee extension is considered and confirmed by measuring surface electromyography (surface-EMG).

DOI： 10.1109/ICARCV.2016.7838709

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In this study, a variable viscoelastic joint system with a clutch for a human assistance was proposed. The variable viscoelastic joint system comprised antagonized artificial muscles and magneto-rheological fluid brake (MR-brake). This system enabled the human assisting device such as exoskeletons to retain structural softness when compared with the existing devices driven by motor and reduction gear, which could only achieve superficial softness. In addition, a clutch system that provided high back-drivability to the wearer by structurally separating the device from the wearer was proposed. As an initial step in designing the human assisting device, a prototype with the proposed variable viscoelastic joint system for knee assistance is developed. Also, its control method were developed. Furthermore, experiments were conducted to confirm the influence of the proposed viscoelastic joint system on the wearer and the effectiveness of the clutch system.

DOI： 10.1109/ICARCV.2016.7838562

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In recent years, force feedback devices have been developed to improve the reality of VR experiences. However, most of the general force feedback devices target the upper limbs. By realizing force feedback to the lower limbs, it will be possible to realize an experience in VR space that cannot be achieved by force feedback to the upper limbs alone. Therefore, the authors aim to develop a lower limb force feedback device. In this study, we developed a lower limb force feedback device based on a physical model at soccer kicking. The output torque of the developed device was confirmed that met the target torque by the experiment.

DOI： 10.1299/jsmermd.2022.2p2-d04

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

In recent years, force feedback devices have been developed to improve the reality of VR experiences. However, most of the general force feedback devices target the upper limbs. By realizing force feedback to the lower limbs, it will be possible to realize an experience in VR space that cannot be achieved by force feedback to the upper limbs alone. The authors have clarified the perceptual characteristics of the human dropping sensation in order to present force feedback to the lower limbs. In this study, we developed a wearable force feedback device that can present the sensation of dropping in VR space.

DOI： 10.1299/jsmermd.2022.2p2-d05

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Language：Japanese   Publisher：東京 : 日本AEM学会  

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Pneumatic drive systems are widely used in assistance devices and flexible drive robots owing to their characteristics of light weight, high output, and flexibility. However, those devices cannot perform instantaneous operation because those devices have low responsiveness. Then we focus on the physical properties of flammable dimethyl ether (DME), and we considered using combustion of DME to improve the responsiveness of pneumatic drive systems. We developed artificial muscle which is driven by burning DME inside the device. In this paper, we conducted the experiment to investigate the response time and displacement of artificial muscle when DME burned in the device.

DOI： 10.1299/jsmermd.2021.2p1-h01

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Language：English   Publisher：The Japan Society of Applied Electromagnetics and Mechanics  

Bio-robotics is a research field that learns from the structural and control systems acquired by living organisms in the process of evolution and makes use of them in robotics. When imitating living organisms, it is still difficult to completely imitate their components such as muscles and skeletal structures, and trial and error is being carried out by applying various methods. Magnetic smart fluids are also attracting attention in bio-inspired robotics because not only they are liquids but also able to generate displacements and their properties by an external magnetic field. In this paper, we explain the earthworm-type robot and the variable viscoelastic joint system which is a bio-inspired robot using magnetic smart fluid.

DOI： 10.14243/jsaem.29.629

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

In this paper, we proposed the application of a device using a variable viscoelastic joint for training and rehabilitation. By varying the antagonistic angle of the device with respect to the human motion, the training effects with different loads were verified. The proposed device can switch between training and rehabilitation by changing the antagonistic angle. However, the training effect using the variable viscoelastic joint has not been confirmed yet. Therefore, we measured the muscle potential during the movement when the antagonistic angle of the device was changed. As a result, the value of the EMG increased as the angle of the knee joint and the antagonistic angle of the device during the movement increased. It was confirmed that the variable viscoelastic joint can be applied to training.

DOI： 10.1299/jsmermd.2021.2p2-e05

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The authors have developed a variable viscoelastic joint module that mimics the principle of human joint drive. It is composed of antagonized pneumatic artificial muscles and a magnetorheological fluid brake. In the previous research, the joint module is developed and the variable stiffness performance is evaluated. In this paper, the variable viscous element of the joint module is evaluated by experiment. Result confirmed that the module has variable viscosity characteristics and it can be applied to robotic systems.

DOI： 10.1299/jsmermd.2021.2p2-g03

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Various haptic devices for application to virtual reality have been developed. Most of them have to be stationary on a desk, thus users cannot move around. To overcome this shortcoming, we propose a wearable force feedback device that uses air jet. In this paper, a prototype for hand position guidance which is able to provide force in any direction is developed, and its performance is evaluated by experiments.

DOI： 10.1299/jsmermd.2021.1a1-h02

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In a virtual reality (VR) space, wearing a head-mounted display can help with the visualization of objects, however, users cannot experience realistic tactile sensations. Recently, several force feedback devices have been developed, including wearable devices that use straight-fiber-type pneumatic muscles and magnetorheological fluids. This allows the devices to render elastic, frictional, and viscous forces during spatially unrestricted movement. Nevertheless, there are two problems. One is that there were items with low scores in the subjective evaluation regarding the discrimination of device weight and force magnitude. The other is the inability to handle many bilateral upper limb movement tasks. Therefore, this study aims to develop a device that can handle movements that interact with both arms.

DOI： 10.1299/jsmermd.2021.1a1-h04

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Pneumatic artificial muscles are advantageous owing to dynamic stiffness. However, the drawback of this is their poor controllability. In this paper, a reinforcement learning-based control system using a real robot is proposed to improve controllability. The proposed system is aimed to generate dynamic motion patterns that utilize the body structure and variable stiffness characteristics. We propose a reinforcement learning-based realistic drum-playing robot, and confirm its effectiveness through experiments.

DOI： 10.1299/jsmermd.2021.2p2-e07

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In the inspection of sewage pipes, it is necessary to prepare a pipeline map in order to efficiently identify the damaged areas, which are often lost so it is necessary to prepare a pipeline map at the same time as the inspection. The authors have previously developed a peristaltic robot for sewer pipe inspection and have estimated the pipe shape using IMU sensors. However, the accuracy of the estimated map was not enough to be put into practice. In this study, we try to improve the estimation accuracy by measuring the information of the position and orientation of the start and end points of the pipeline to constrain the estimated pipeline shape. The authors represent the pipe geometry with only three parameters, and the correction is performed by iterative calculation using the inverse Jacobian matrix.

DOI： 10.1299/jsmermd.2021.1a1-g08

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The purpose of this study is to investigate the effects on human fall sensation when a VR fall sensation presentation device is used to decelerate the device during descent. A questionnaire survey using VAS was conducted to evaluate the effects of acceleration and deceleration on the sensation of falling. A questionnaire using VAS was used to evaluate the sensation of falling and the sense of reality depending on the amount of acceleration and the amount of deceleration. The results suggest that, within the range of acceleration used in this experiment, the deceleration of the device does not significantly impair the sense of falling and the sense of reality.

DOI： 10.1299/jsmermd.2021.2a1-m07

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The mixing and transporting process of a solid–liquid mixture and a high-viscosity fluid is separate batch processes, leading to an increase in maintenance costs and disposal costs. To achieve continuous mixing and transporting process, the authors have developed a pneumatic peristaltic mixing conveyor based on the movement of transporting bolus in the intestinal tract. The proposed conveyer is possible to mix and transport with one device continuously, however, it has not been studied to mix and transport at the same time like the actual intestine does. In this paper, we proposed a congruence which is able to continuously switch between segmental and peristaltic movement in order to achieve a continuous mixing and transporting.

DOI： 10.1299/jsmermd.2021.2p1-e06

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We proposed herein a method for estimating the mixing state of the contents of a peristaltic continuous mixing conveyor simulating the intestine, developed for mixing and conveying powders and liquids. This study serves to improve a previously proposed method for estimating the mixing state using a logistic regression model with the pneumatic factor sensors installed in the device as inputs. To improve the estimation method, we changed the method of acquiring training data and labeling in the learning model. Moreover, comparison of the estimation accuracy and the result of the proposed method was better than that of the previous method.

DOI： 10.1299/jsmermd.2021.2p2-g01

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In transporting LP gas tanks, the load of workers is high due to handling heavy LP gas tanks. In previous studies, the physical load of workers when handling LP gas tanks was not evaluated quantitatively. This study aimed to evaluate the physical load in handling the LP gas by motion capture system and muscle potential. In this paper, a posture with carrying on the shoulder the LP gas tank was evaluated from the viewpoint of load torque of joints, muscle potential, and compression force of intervertebral discs.

DOI： 10.1299/jsmermd.2021.2p2-i10

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Currently, soft actuators are being actively researched. Genellary, soft actuators are more difficult to control than ordinary actuators because of their flexibility. Therefore, there is a need for a sensor that can be unified with the soft actuator and measure the change in shape of large deformations without interfering with the deformation of the soft actuator. In this study, we propose a strain sensor that can measure the displacement of a soft actuator based on a conductive paste with silver as a filler. This paper describes the investigation of the basic properties of conductive pastes using silver filler and the measurement equipment.

DOI： 10.1299/jsmermd.2021.2p1-e05

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Seabed mineral resources such as rare earth elements are widely and shallowly distributed in the deep sea floor 2-3m. Seafloor sampling and analysis are needed to determine their distribution. Vertical drilling with a drilling vessel is effective for depth sampling. However, it requires enormous cost and limits the sampling range to the pipe diameter. Therefore, we are developing a seafloor exploration robot that can excavate horizontally and collect rare earth samples. In this paper, we report the result of field test in an actual sea floor using an excavating robot with water proof finish.

DOI： 10.1299/jsmermd.2020.1a1-b13

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In recent years, attention has been focused on soft actuators, especially dielectric elastomer actuators. DEA has a structure in which a dielectric is sandwiched between flexible electrodes. The performance of DEA depends on the dielectric. Generally, silicon rubber or acrylic rubber is used for the dielectric. When using these materials, the DEA typically requires significant stress during the initial stages of elongation and must be pre-stretched using a rigid frame. This rigid frame limits design and movement, and limits the range of DEA applications. Therefore, we focused on a dielectric material called a slide ring material. SRM can be stretched with low stress during the initial stages of elongation, therefore DEA which has SRM as dielectric can deform largely without pre-stretch. In this paper, a bending unit is developed using DEA with SRM, and its movement is confirmed by experiment.

DOI： 10.1299/jsmermd.2020.1a1-j02

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There are many force feedback devices that focus on upper limbs. However, in the real world, not only the upper limbs get force feedback. Therefore, the authors attempt to develop a wearable lower limb force feedback device that enables users to move around in wide area. However, there is a limit to the size of a device worn by human, and it is difficult to present an acceleration equivalent to gravitational acceleration with a wearable type device. Therefore, the authors proposed a method of giving a descent acceleration smaller than the real world and evaluated the sensation of falling of humans.

DOI： 10.1299/jsmermd.2020.1p1-n02

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Pneumatic drive systems are widely used in assistance devices and flexible drive robots owing to their characteristics of light weight, high output, and excellent flexibility. Compressed air generated by engine compressors and large motors is mainly used to drive these devices, but such large and heavy air pressure sources are barriers to the mobilization of pneumatic drive devices. Then ,we focus on the physical properties of flammable dimethyl ether (DME), and consider obtaining energy in two stages via a phase change and the combustion of DME to develop a new mobile air pressure source that can release enough pressure and flow. In this paper, we measured the pressure when the mixed gas is burned in a semi-hermetic state.

DOI： 10.1299/jsmermd.2020.1p2-h01

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Valuable seabed mineral resources such as rare earth elements are deposited 2–3 meters into the deep sea floor, and sampling and analyzing the seafloor is necessary to clarify how they are generated and distributed. We have developed a seafloor robotic explorer that can excavate horizontally and collect samples of rare earth elements, which may enable wide-area exploration as multiple robots could be simultaneously implemented to autonomously search beneath the seabed. The seafloor robotic explorer may excavate sediments such as clay and sand before reaching the rare earth layer. In previous studies, it has been discovered that the rotation speed, penetration force, and characteristics of the sediment affected the excavation resistance. Therefore, we assumed that controlling the rotation speed and penetration force would enable an efficient excavation according to the ground characteristics. Therefore, in this paper, we examined the effect of penetration force on drilling efficiency using both dry and underwater silica sand ground with different ground characteristics.

DOI： 10.1299/jsmermd.2020.1a1-b03

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This paper introduces a two-degree-of-freedom pipe selection mechanism using contraction and extension unit composed of single tube and a T branch experiment of an in-pipe mobile robot equipped with this mechanism. Household piping is used for gas transportation to each household. If the pipe is cracked or corroded due to long-term use, it becomes difficult to supply a stable gas. Therefore, inspection of household piping is necessary. The existing methods require a lot of time for the inspection or it is difficult to inspect the entire pipeline. Therefore, in this study we developed an inspection robot for home piping using a mobile robot. To date, the robots proposed have been able to bend in the direction along the pipeline, as the tip of the robot passively bends when passing through the curved pipe. However, at the branch pipe, there is no mechanism that actively bends the tip of the robot, and the pipe cannot be selected and moved in a specific direction. Therefore, this paper proposes the application of a small pipe selection mechanism combining a ball-point pen knock mechanism and a wire bending mechanism to an in-pipe mobile robot using the pressure difference of a single tube.

DOI： 10.1299/transjsme.20-00052

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This paper describes multi-segmentation of artificial muscles integrally molded by a 3D printer and simplification of post-processing. In recent years, with the improvement in performance of 3D printers, it has become possible to integrally mold flexible and hard materials. From this, attention has been focused on the integral molding of actuators that makes effective use of the complex structure of 3D printers. Most of the actuators using 3D printers use air pressure, and in consideration of the material properties, pistons using a bellows structure are common. However, the output of the piston is small because the pressure receiving area is small. Therefore, the pneumatic artificial muscle was integrally molded using the structural advantage. In this paper, we focused on the contraction length of the artificial muscle, and integrally molded the artificial muscle with the increased number of segments. In addition, the design was changed to reduce post-processing after molding. We also discussed the effect of increasing the number of segments on contraction by measuring the contraction of the artificial muscle.

DOI： 10.1299/jsmermd.2020.1p2-h14

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In this paper, a prototype of a joint in which a pneumatic artificial muscle and a tension spring are antagonistically arranged (one-sided spring antagonized joint) was developed, and the basic characteristics of the prototype were evaluated. The relationship between the torque and the angle of the prototype showed that torque increases as the angle increases (or vice versa). It was also found that the joint stiffness and the antagonized angle changed with each applied pressure. From these results, it was confirmed that the prototype showed the same behavior as the theoretical one-sided spring antagonized joint.

DOI： 10.1299/jsmermd.2020.2p1-c02

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Research on haptic devices aiming at application to virtual reality (VR) has been conducted. Most of them have to be fixed on a desk, and users can’t move around. To avoid this problem, exoskeleton type haptic device have been developed. However, there are problems such as discomfort caused by the reaction force of the presented haptic force at another part of the body. In addition, limitation of the rage of motion by exoskeleton structure is also problem. Therefore, in this research, we propose a wearable force feed back device using air jet without skeletal structure. In this report, an elastic ball presentation experiment using a prototype was conducted. Results confirmed the ability to render virtual ball with different sizes and stiffness.

DOI： 10.1299/jsmermd.2020.2a1-p05

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The authors have developed A variable viscoelastic joint that mimics the principle of human joint drive and uses a pneumatic artificial muscle with an antagonistic arrangement and a magnetic viscous fluid brake. In this paper, the versatility of this joint was improved by modularizing this joint. The variable viscoelastic joint module is the world's first pneumatic drive module with a variable viscoelastic characteristic that includes a power source inside the device. We believe that the development of this device will make it easier to manufacture robots that are lighter, safer and easier to maintain than robots that use motors and reduction gears, and will operate at lower cost.

DOI： 10.1299/jsmermd.2020.2a2-h04

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In the inspection of sewer pipes, it is necessary to identify the damaged part, and a pipe diagram is indispensable, but it is often dissipated and many pipe maps do not exist. Therefore, it is required to create pipeline diagrams. Therefore, the authors used an IMU sensor that measures three-axis acceleration and three-axis angular velocity, and corrected the cumulative error that occurred at that time by using the traveling characteristics of the earthworm's peristaltic motion, which is a periodic motion of progression and stopping. We tried to measure the pipe length and the pipe shape. In this report, we conducted a basic evaluation experiment to measure the pipe length with high accuracy, and investigated the effectiveness of this method.

DOI： 10.1299/jsmermd.2020.2a2-h06

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In order to excavate lunar underground, we have developed a lunar earthworm-type excavation robot “LEAVO”. The target missions of LEAVO are 1) excavate boreholes for environmental sensors and 2) collect some samples in particular layer. LEAVO has succeeded in 938 mm vertical excavation, and we confirmed its usefulness in the target mission 1). In addition, in order to expand the excavation range to achieve mission 2), a distributed driving system was developed as a new drive system for bending and horizontal excavation, and excavation performance was confirmed through excavation experiments. In this study, we design and develop a propulsion unit for an excavation robot in combination with a distributed driving system.

DOI： 10.1299/jsmermd.2020.2p1-b03

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In order to excavate lunar underground, we have developed a lunar earthworm-type excavation robot “LEAVO”. The target missions of LEAVO are 1) excavate boreholes for environmental sensors and 2) collect some samples in particular layer. LEAVO has succeeded in 938 mm vertical excavation and we confirmed its usefulness in the target mission 1). Then, we now aim to study curving excavation to achieve target mission 2). This study aims to excavate regolith in a particular layer with LEAVO. For this reason, new driving system is developed. It enables to deploy drive motor on the circumference of the excavating axis so LEAVO can curve easily. Therefore, the authors conduct excavation experiment using excavating unit, and check the possibility of the proposed system.

DOI： 10.1299/jsmermd.2019.2p1-t06

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A four degrees of freedom wearable force feedback device with pneumatic artificial muscles and magnetorheological fluid clutches have been developed. The device has four degrees of freedom at shoulder and elbow. By arranging artificial muscles and magnetorheological fluid clutches at each joint, the device can render elasticity using characteristic of artificial muscle, friction, and viscosity by controlling torque of magnetorheological fluid clutch. We have already confirmed that the device render elasticity and friction. However, we have not confirmed whether the device can render viscosity yet. In this paper, we derived an equation for rendering viscosity, and conducted an experiment based on the equation.

DOI： 10.1299/jsmermd.2019.2a1-s07

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The pneumatic soft actuator converts the input energy by utilizing structural deformation or material deformation according to the applied pressure to obtain the output. Although various forms of operation are conceivable, in practice it was difficult to freely design under manufacturing constraints. In recent years, with the development of 3D printers, flexible materials such as rubber as well as hard materials such as conventional resin can be printed. It is now possible to manufacture an actuator having a complicated shape combining a resin material and a rubber material that have been difficult to produce. In this paper, Pleated Pneumatic Artificial Muscles using 3D printer which can design freely using resin and rubber material with fabricated and evaluated contraction characteristics.

DOI： 10.1299/jsmermd.2019.2a1-c07

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Recently, in Japan, a burden for labor is increasing due to the aging society. To solve these problem, assistive suits are proposed for one of the solutions. In the previous study, an assistive suit, Airsist I has been developed that is based on the variable viscoelasticity. However, the motion judgment interface for Airsist I has not been studied. In this study, joint angle and joint angular velocity are used to judge the motion of the wearer, because Airsist I has a high backdrivability. This paper reports the motion judgment algorithm that is based on the wearer’s joint angle, and joint angular velocity, and experiments are conducted to evaluate the utility of the algorithm.

DOI： 10.1299/jsmermd.2019.1a1-h10

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Force feedback devices are attracting attention as a means to apply virtual reality and augmented reality to sports, entertainment, and rehabilitation. We have developed a force feedback device Using pneumatic artificial muscle and magneto-rheological fluid clutch. However, there were problems such as increase in the weight of the device and complication of control system. In order to solve these problems, a new force feedback method using an elastic spring and a magneto-rheological fluid clutch was proposed. The force feedback characteristics of the force feedback method were modeled. A 1-degree-of-freedom force feedback device using a new force feedback method was developed. Modeled characteristics of force feedback were confirmed by conducting experiment for rendering elasticity using the device.

DOI： 10.1299/jsmermd.2019.1p1-t04

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The authors have developed a peristaltic motion type transport machine simulating the movement of the intestinal tract. As a drilling earth and sand transportation method, we have proposed sediment transport by a peristaltic motion type transport machine. Vertical transport experiments of samples with varying particle size and moisture content so far have been conducted to show that samples of each particle size can be transported. However, we don’t know how the conveying amount varies depending on the liquid limit and water content ratio of each sample. In this report, we discuss the boundary of lifting sample by discussing the transport amount from the ratio of moisture content and liquidity limit.

DOI： 10.1299/jsmermd.2019.1p2-d04

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Pneumatic artificial muscles have characteristics that are not found in motors such as lightweight and flexible. However, it is difficult to accurately sensing of state due to large deformation during operation and nonlinearity. To solve the problem, authors focus on a piezoelectric wire sensor which can sense change of shape. In this paper, we investigated the output characteristics of the piezoelectric wire sensor when changing collision speed, load and contact surface shape for sensing of artificial muscle. Results show that while the collision speed and the output are in a proportional trend, the load and the contact surface shape have less influence on the output.

DOI： 10.1299/jsmermd.2019.1p2-k02

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Movement of ankle and pneumatic compression to lower limb are able to increase the blood flow, and effective for DVT prevention. However, people with neuromotor disabilities can not move their ankle, and pneumatic compression can cause nerve palsy of fibula. Therefore, we proposed the device which can provide both passive movement of ankle and pneumatic compression to lower limb. In this paper, a prototype driven by pneumatic actuators is developed, and a change of blood flow with the prototype is evaluated.

DOI： 10.1299/jsmermd.2019.2p1-c09

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In order to process lunar underground excavation, we have developed a lunar earthworm-type excavation robot ("LEAVO"). As we achieved vertical excavation with it, we now aim to perform curving excavation to make LEAVO be able to collect samples more efficiently in a particular layer. To achieve this goal, it is necessary for the LEAVO's excavation sub-units to support the robot on different borehole diameters, because the diameter enlarges in curves. As the previously developed curving excavation system could not support correctly the robot in the curves, we propose in this paper a "grasping system using a scroll chuck" and test its output characteristics. By doing so, we will conclude if it can be applied in a curving excavation system.

DOI： 10.1299/jsmermd.2019.2p1-t07

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DOI： 10.1299/jsmermd.2019.2a1-t08

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Force feed back devices have been studied. Many of them are desktop type fixed to a heavy object such as desks, and they can not be used for applications with movement. Wearable devices have been developed, however, other problems such as discomfort caused by the reaction force of the device at another part of the body are occured. In this research, a force feed back method using compressed air jetting for wearable force feed back device is proposed. In this paper, concept of the method is introduced and the effectiveness is verified with prototype.

DOI： 10.1299/jsmermd.2019.1p2-t09

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Language：Japanese   Publisher：The Robotics Society of Japan  

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DOI： 10.7210/jrsj.37.34

DOI： 10.1299/transjsme.23-00208_references_DOI_OhaCHh18wG1gGvawcDd2xOO7GqV

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DOI： 10.7210/jrsj.37.57

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In this paper, an assistance method that controls the joint stiffness and antagonized angle using variable elastic elements is proposed. The proposed system changes the joint stiffness and antagonized angle so that they correspond to the phase of movement, and performs movement assistance in cooperation with the wearer. As a structurally variable configuration of stiffness and antagonized angle, a joint structure in which an artificial muscle and tension spring are antagonistically arranged is proposed. A mathematical model of one side spring antagonized joint is proposed and its characteristics is examined.

DOI： 10.1299/jsmermd.2019.1a1-i01

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Valuable seabed mineral resources such as rare earth elements are deposited 2–3 meters into the deep sea floor, and sampling and analyzing the seafloor is necessary to clarify how they are generated and distributed. The current general sampling method based on vertical drilling effectively acquires the geological profile in the vertical direction. However, it is inefficient for investigating deposits widely distributed in the horizontal direction because the sampling range is limited to the diameter of the pipe. We are developing a seafloor robotic explorer that can excavate horizontally and collect samples of rare earth elements, which may enable wide-area exploration as multiple robots could be simultaneously implemented to autonomously search beneath the seabed. The excavation depth of our previously reported underwater drilling robot SEAVO II was limited to 430 mm; the discharging outlet became buried in the ground, making it difficult to discharge the drilled soil and ultimately limiting the excavation depth. In this work, we introduce a discharging mechanism that implements water jetting to improve the excavation depth.

DOI： 10.1299/jsmermd.2019.2a1-i02

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In this paper, evaluation experiment of an antagonistic joint with two artificial muscles is conducted with feedforward controller which is based on the experimental identification model. The previous controller was based on a mechanical equilibrium model which we can understand the characteristics of the artificial muscle. However, the accuracy of the controller was poor, and the calculation is too complex that the sequential calculation cannot keep up with a real time control on a microcontroller. Thus, this paper proposes an experimental identification model whose calculation is simpler, and has a better accuracy than the previous one. Also, the parameters in the model are easily identified by the measurement experiment of the artificial muscle. And apply the feedforward controller which is based on an experimental identification model to the antagonist joint with two artificial muscles.

DOI： 10.1299/jsmermd.2018.2a2-g14

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A pneumatic artificial muscle is an air pressure-activated rubber actuator. It is lightweight and high in power density compared to motorized actuators and fluidic cylinders. The authors have developed a straight-fiber-type pneumatic artificial muscle (SF-ARM) with high output and contraction amounts compared to those of the widely used McKibben type artificial muscle. Until now, the ratio between the inside diameter of the SF-ARM and the operating part length was examined. However, there is a limit in extending the fatigue life by decreasing the aspect ratio. Therefore, in this study, we have extended the life by changing stress amplitude. As a result, fatigue life could be improved by reducing stress amplitude.

DOI： 10.1299/jsmermd.2018.2a2-g15

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Pneumatic driven assistive devices have advantages such as structurally flexible movement, however, they have a problem in its mobilization since they need heavy air compressor to be activated. Therefore, in this research, we developed a hybrid portable pneumatic source for pneumatic driven assistive device based on the principle of a hybrid pneumatic source in the previous research. The developed prototype can supply more than 600 NL total flow by one energy supply and 0.7 MPa of pressure with the portable weight. The assistive device was also driven using the prototype, and it was confirmed that the device could be driven properly.

DOI： 10.1299/jsmermd.2018.2p1-h16

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Low back pain is a typical occupational illness, and wearable assistive devices have been studied for its prevention. These wearable assistive devices assist extension of the waist or hip joint, however, they can not assist other joints such as elbow. Also, wearer has to support the weight of the device itself during an action other than lifting-up motion such as walking. In this research, to solve the problem above, a ground contacting type assistive device which assists lifting-up motion is proposed. The proposed device aims at a lightweight construction and high assist efficiency by letting the weight of the heavy object transmit directly to the ground. In this paper, we describe the concept, and the effectiveness of the proposed method is verified by ex0periment with a prototype.

DOI： 10.1299/jsmermd.2018.1p1-c16

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In this study, a variable viscoelastic joint system comprising antagonized artificial muscles and magneto-rheological fluid brakes is proposed. This system enables human assisting devices such as robotic exoskeletons to retain structural softness when compared with the existing devices driven by motors and reduction gears, which can only achieve superficial softness. The authors had proposed the system and showed its effectiveness via experiments using a prototype with one degree of freedom in their previous works. In this study, as the next step in designing the human assisting device, a lower body assistive prototype “Airsist I” is introduced. In addition, a control method that can cooperate with the wearer without the need for an additional operation is proposed.

DOI： 10.1299/jsmermd.2017.1p1-k08

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As an entertainment robot, musical instrument performance robots are being studied. However, it is difficult to play musical instruments with the same expression as human for existing robots. Especially, in regards to percussion, it is quite difficult because human changes not only torque of joint but stiffness and viscous during playing. Therefore, we focus on applying a variable viscoelastic joints authors have studied to performance robot that playing percussive instrument. In this paper, concept of the robot is proposed and 1 degree of freedom prototype is developed. Moreover, sound volume measuring experiment is conducted by the prototype. The result is compared to the result obtained by a motor driven prototype.

DOI： 10.1299/jsmermd.2017.2a2-f05

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Pneumatic driven systems are widely used in various fields. Recently, it is applied to wearable assist systems since it is lightweight, high-power and retains structural softness. To activate these pneumatic actuators, air compressor which is driven by large motors or engine is used generally. These heavy and large systems prevent pneumatic systems from being portable. If portable pneumatic power source were developed, pneumatic system could be used in wider fields. Thus, in this study, we aim to develop portable pneumatic power source that is enable to withstand practical use. As an initial step, various air compressing methods are evaluated in terms of portability in this paper. Methods to compare are small compressor activated by battery, phase change of material a chemical reaction.

DOI： 10.1299/jsmermd.2017.2p1-d02

DOI： 10.20965/jrm.2018.p0752_references_DOI_9NQpVoc1kai9cqGTk8y6cAuNg3d

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Working population decreases because of the aging society. Therefore the workload per person increases. To solve this problem, assist suit is studied activity. This study has proposed a new actuation system with variable viscoelastic joint for an exoskeleton assist suit. This variable viscoelastic joint system is composed of antagonized artificial muscles and magneto-rheological fluid brake (MR-brake). The system enables assist suit to have structural softness and high back-drivability. This paper evaluated back-drivability of the system. So, organoleptic evaluation experiment which compares variable viscoelastic joint system to actuation system with motor and reduction gear was conducted. As a result, high back-drivability of variable viscoelastic joint system was confirmed.

DOI： 10.1299/jsmermd.2017.1p2-j08

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

In this study, a novel actuation system for an exoskeleton with a variable viscoelastic joint and clutch was proposed. The variable viscoelastic joint system comprised antagonized artificial muscles and magneto-rheological fluid brake (MR-brake). This system enabled the exoskeleton to retain structural softness when compared with the existing exoskeletons driven by motor and reduction gear, which could only achieve superficial softness. In addition, a clutch system that provided high back-drivability to the wearer by structurally separating the exoskeleton from the wearer was proposed. As an initial step in designing the exoskeleton, a knee exoskeleton with the proposed system and its control method were developed in this study. Furthermore, experiments were conducted to confirm the influence of the proposed viscoelastic system on the wearer and the effectiveness of the clutch system.

DOI： 10.1299/jsmermd.2016.2a2-13b1

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

A variable viscoelastic joint system with a clutch for a human assistance is proposed in this research. The variable viscoelastic joint system comprised antagonized artificial muscles and magneto-rheological fluid brake (MR-brake). This system enabled the human assisting device such as exoskeletons to retain structural softness when compared with the existing devices driven by motor and reduction gear, which could only achieve superficial softness. In this paper, a space saving pulley for antagonized pneumatic muscle is proposed. Generally, required assisting torque of human joints at flexion and extension are different. Therefore, adopting a step pulley is preferable when joints are driven by antagonized pneumatic muscle. However, a step pulley makes a joint system thicker and generates unnecessary torque. The proposed pulley resolve these problem by placing two antagonized wires in the same plane which is vertical to rotation axis of the pulley.

DOI： 10.1299/jsmemecj.2016.s1510205

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Recently, many devices driven by pneumatic have been developed. Generally, they need large air compressor to obtain compressed air. However, such large and heavy pneumatic power source prevent such devices to be portable. Thus, in this paper, portable pneumatic power source using chemical reaction of sodium hydrogen carbonate and citric acid is proposed. Carbon dioxide generated in the chemical reaction is used for compressing air. Both sodium hydrogen carbonate and citric acid are generally used for cleaning, and it is cheap and non-poisonous. In addition, an experiment is conducted to verify effectiveness of proposed power source.

DOI： 10.1299/jsmermd.2016.2a1-03b6

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

To achieve dynamic motion, such as jumping and running, generating large instantaneous force and decreasing impact force at the time of the landing are needed. However, when increasing the instantaneous force of actuators such as motors and hydraulic actuators, the weight of robot also tend to increase. Therefore, in this study, we focused on the variable viscoelastic element with the human muscle. In this paper, we developed a bipedal jumping robot with variable viscoelastic joints. In this robot, we adopted straight-fiber-type artificial muscle as a variable elastic element and the magnetorheological fluid (MR) brake as a variable viscous-friction element. Moreover, we conducted the bending and stretching operation experiment by this robot. In this experiment, we used the experimental parameters which were determined based on human bending and stretching operation. As a result, it was confirmed that this robot realized the bending and stretching operation.

DOI： 10.1299/jsmemecj.2016.s1510201

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Working population decreases because of the aging society. Therefore the workload per person increases. To solve this problem, wearable assist suit (WAS) is studied activity. So the authors propose novel WAS which has a clutch and a variable viscoelasticity joint. As first stage of the WAS development, relationship between resistance torque to knee and the discomfort the wearer experiences is investigated by a survey questionnaire experiment. Range of resistance torque to the knee which is acceptable in daily use for a wearer is declared. Moreover, the influence of resistant torque on a muscle of knee extension is considered and confirmed by measuring surface-electromyography.

DOI： 10.1299/jsmermd.2016.2a2-14a1

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

This paper presents a fluid powered Motion Socks aimed to prevent deep vein thrombosis (DVT). As the basic design concept, "Safe Area" is introduced, which can assure both safe driving direction for the foot and efficient force transmission. To satisfy this concept, two types of fluid powered actuators with flexible structure are proposed to generate pulling motion and pushing one. The proposed Motion Socks can realize four different motions by using three pull-actuators and one push-actuator. Additionally, in order to measure the posture of the ankle, a sensing device composed of two bending sensors is proposed, which is attached on the inside of Motion Socks. The proposed whole system could successfully promote the blood circulation and its validity was experimentally verified.

DOI： 10.1299/jsmermd.2014._1a1-g02_1

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

This paper describes the development of a fluid powered Motion Socks aimed to prevent deep vein thrombosis (DVT). In general, actuators have a characteristic that the more degree of freedom they have, the lager they are. Also, slippage between a body and wearable devices is an issue as well. In order to solve these problems, it is suggested the device called curved tube actuator for creating flexure motion of ankles using an actuator capable of generating force vertically to a body. The creating flexion motions of an ankle using this actuator were showed through experiment showing the effectiveness of the actuator regarding support of ankle motion.

DOI： 10.1299/jsmermd.2012._2p1-b01_1

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Language：Japanese   Publisher：東京 : 日本フルードパワーシステム学会  

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Other Link： https://ndlsearch.ndl.go.jp/books/R000000004-I030671180

Publisher：The Ceramic Society of Japan  

Highly-oriented Si nanoparticles (SNP) were precipitated in amorphous SiO₂ using separation by implanted oxygen (SIMOX) method and showed visible luminescence at room temperature. In order to investigate the microstructure of the SNPs, we observed the Si/SiO₂ interface by cross-sectional high-resolution transmission electron microscopy (HRTEM). The three-dimensional shape of the SNPs observed from different directions is an {111}-surrounded octahedral structure, each apex of which has an {100} facet. The upper (surface-side) interface of SiO₂/Si(100) contains missing atomic rows, while the lower (substrate-side) interface of Si(100)/SiO₂ is atomically flat except for the steps at the intersection with (111) plane. Similar atomically sharp structures were observed at the Si{111}/SiO₂ interfaces. Image-simulation of the interfaces well reproduced the microstructures observed by HRTEM and proved that the interfaces are those of amorphous SiO₂ and single-crystal Si without any intermediate layer.

DOI： 10.2109/jcersj.106.1255

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Application no：特願2017-051685  Date applied：2017.3.16

Announcement no：特開2018-153358  Date announced：2018.10.4

Applicant (Organization)：学校法人中央大学

Application no：特願2017-051679  Date applied：2017.3.16

Announcement no：特開2018-155298  Date announced：2018.10.4

Registration no：特許第6873468号  Date registered：2021.4.23 

Applicant (Organization)：学校法人中央大学

Application no：特願2016-215450  Date applied：2016.11.2

Announcement no：特開2018-071740  Date announced：2018.5.10

Registration no：特許第6854504号  Date registered：2021.3.18 

Applicant (Organization)：学校法人中央大学

Application no：特願2016-200304  Date applied：2016.10.11

Announcement no：特開2018-061613  Date announced：2018.4.19

Registration no：特許第6781457号  Date registered：2020.10.20 

Applicant (Organization)：学校法人中央大学

Application no：特願2016-126474  Date applied：2016.6.27

Announcement no：特開2018-003855  Date announced：2018.1.11

Registration no：特許第6757027号  Date registered：2020.9.1 

Applicant (Organization)：学校法人中央大学