Language：Japanese   Publisher：The Robotics Society of Japan  

Small rovers are suitable for carpooling or precursor missions and have been expected to explore complex areas where large rovers are hard to traverse. However, the moving performance of small rovers is lower than that of large rovers in general. This study designs a novel jumping mechanism that mimics a grasshopper leg for small rovers. We produced nine different leg expansion trajectories by changing the joint positions of the mechanism and investigated how these trajectories affected jumping performance. The highest jumping was obtained with a straight expansion trajectory and a kicking behind the foot, and kicking in front of the foot with a upward convex expansion trajectory generated the longest jump distance.

DOI： 10.7210/jrsj.40.643

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Authorship：Lead author   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers ({IEEE})  

© 2016 IEEE. This letter presents the hopping performance evaluation on three types of terrains and novel foot pad designs for efficient traverse of hopping rovers. Hopping rovers, called Hopper, are expected to explore scientific richness areas where wheeled vehicles are hard to traverse. In order to succeed in the robotic planetary exploration, optimization and efficient designs of rovers are essential. Almost all planetary surfaces are covered with sand, called regolith, which makes hopping efficiency bad. In this letter, we discover the hopping performance on three kinds of terrains. Moreover, we also propose the method of increasing hopping performance on soft soil. Inspired by the conventional wheeled vehicle design, treads, called grouser, are installed on the bottom of the foot pad. While grousers are effective on hard ground and soft soil, they are ineffective on bilayer terrain. Bilayer means that hard ground is covered with thin regolith. And the other novel grouser shape is designed based on the soil interaction model using a multi-objective evolutionary algorithm. The proposed design improves the hopping performance on soft soil in comparison with the straight grouser.

DOI： 10.1109/LRA.2019.2926222

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

© 2018 IEEE. This paper presents a novel mechanical design for efficient traverse of hopping rovers. In order to continue the exploration of planetary environment without any human help, optimizations and efficient designs of rovers are essential. In particular, improving robustness and decreasing energy consumption are crucial aspects of rovers design. Hopping efficiency on sandy surfaces is strikingly worse than on hard ground, because such soil is deformed and easily causes slip. The purpose of this paper is to develop a novel mechanical design which can get enough friction from granular media. First, the effects of soft soil for hopping are studied by comparing with hopping on hard ground in terms of energy. Next, a novel foot pad design for hopping on planetary terrain is proposed. Inspired by the conventional wheeled vehicle design, treads, called grouser, are installed for the bottom of the proposed foot pad. The effectiveness of the proposed design is validated through experimental evaluation.

DOI： 10.1109/aim.2018.8452427

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Authorship：Lead author   Publishing type：Research paper (scientific journal)  

© 2017, Fuji Technology Press. All rights reserved. Various planetary terrains or asteroids, which are hard to traverse with wheeled platforms, are expected to be explored. Bekker’s model cannot be applied to estimate the motions of rovers without wheels, such as the hopping rover (hopper). In this paper, the resistive force theory (RFT) approach is introduced. This approach is not based on Bekker’s model, and is expected to apply to any platform. However, this RFT approach only applies to static or quasi-static motion, such as in the case of slow motions. To apply the RFT approach to dynamic motions, such as hopping, the effect of velocity as a dynamic variable is also studied. Through the hopping experiments, the effectiveness of RFT with the velocity-term approach is investigated and compared to the RFT approach.

DOI： 10.20965/jrm.2017.p0895

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

© 2017 IEEE. For planetary exploration, small robots of just a few kilograms installed in the main spacecraft have a lot of advantages. Small robots can provide us with a wide range of exploration opportunities by using multi-robots, technical demonstrations, and science missions which require detailed data acquisition. There are not only mission advantages, but they can also be developed in a short period of time and at a low cost. MINERVA, MINERVA II, MASCOT are examples which are installed in the main spacecraft for surface exploration. In order to move on the surface of a "low gravity" object, like the Moon by a small robot, there are several options of locomotion, such as jumping, wheels, and legs. Wheel locomotion cannot step over obstacles where the size is bigger than the wheel radius, and the structure of leg locomotion is a very complicated piece of machinery and requires a lot of actuators. However, jumping locomotion is capable of moving a long distance by one action and the number of actuators required for jumping capability is very small. In addition, it can travel a longer distance on a planet or satellite which has a gravity lower than the Earth. For instance, it can jump 6 times longer on the Moon than on the Earth. To realize jumping locomotion for small robots in a low gravity environment, the mechanism has to meet the following functional requirements. (1) it can charge the required jumping energy, (2) it can release the energy instantly, (3) it can change the amount of the energy needed to control jumping distance, (4) it doesn't consume resources such as fuel and should be able to repeat the movement, (5) it has a ground contact part to apply power, (6) the size should be small and the weight should be small (7) it can move in a space environment (vacuum, high radiation). We studied some jumping mechanism concepts to meet these requirements. Our design of the mechanism uses springs to charge the energy and they are supported and connected to the shaft structure. A jumping pad is attached to the end of the structure and pushes the ground and robot so it can jump from the ground. For actuation, only one motor is used. In our mechanism, a one-way clutch is used to change from energy charge mode to release mode. This mode change is executed by changing the direction of motor rotation. After jumping, it can change the mode to energy charge mode again. The authors have developed a research model of the jumping rover which the jumping mechanism is mounted on. This model is developed for a lunar exploration mission. Science mission equipment mock-ups and wheels are also mounted on the model. The wheel is used to control the jumping direction. In this paper, our design of the jumping mechanism, development of a research model, and test results are presented in detail.

DOI： 10.1109/aero.2017.7943807

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Language：English   Presentation type：Oral presentation (general)  

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Presentation type：Oral presentation (general)  

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Presentation type：Symposium, workshop panel (public)  

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Language：English   Presentation type：Oral presentation (general)  

© 2018 IEEE. This paper presents a novel mechanical design for efficient traverse of hopping rovers. In order to continue the exploration of planetary environment without any human help, optimizations and efficient designs of rovers are essential. In particular, improving robustness and decreasing energy consumption are crucial aspects of rovers design. Hopping efficiency on sandy surfaces is strikingly worse than on hard ground, because such soil is deformed and easily causes slip. The purpose of this paper is to develop a novel mechanical design which can get enough friction from granular media. First, the effects of soft soil for hopping are studied by comparing with hopping on hard ground in terms of energy. Next, a novel foot pad design for hopping on planetary terrain is proposed. Inspired by the conventional wheeled vehicle design, treads, called grouser, are installed for the bottom of the proposed foot pad. The effectiveness of the proposed design is validated through experimental evaluation.

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Presentation type：Symposium, workshop panel (public)  

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Language：English   Presentation type：Oral presentation (general)  

© 2017 IEEE. For planetary exploration, small robots of just a few kilograms installed in the main spacecraft have a lot of advantages. Small robots can provide us with a wide range of exploration opportunities by using multi-robots, technical demonstrations, and science missions which require detailed data acquisition. There are not only mission advantages, but they can also be developed in a short period of time and at a low cost. MINERVA, MINERVA II, MASCOT are examples which are installed in the main spacecraft for surface exploration. In order to move on the surface of a "low gravity" object, like the Moon by a small robot, there are several options of locomotion, such as jumping, wheels, and legs. Wheel locomotion cannot step over obstacles where the size is bigger than the wheel radius, and the structure of leg locomotion is a very complicated piece of machinery and requires a lot of actuators. However, jumping locomotion is capable of moving a long distance by one action and the number of actuators required for jumping capability is very small. In addition, it can travel a longer distance on a planet or satellite which has a gravity lower than the Earth. For instance, it c

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Language：English   Presentation type：Oral presentation (general)  

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