- Mechanism and Robotics
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Method for six-legged robot stepping on obstacles by indirect force estimation
Chinese Journal of Mechanical Engineering volume 29, pages 669–679 (2016)
Abstract
Adaptive gaits for legged robots often requires force sensors installed on foot-tips, however impact, temperature or humidity can affect or even damage those sensors. Efforts have been made to realize indirect force estimation on the legged robots using leg structures based on planar mechanisms. Robot Octopus III is a six-legged robot using spatial parallel mechanism(UP-2UPS) legs. This paper proposed a novel method to realize indirect force estimation on walking robot based on a spatial parallel mechanism. The direct kinematics model and the inverse kinematics model are established. The force Jacobian matrix is derived based on the kinematics model. Thus, the indirect force estimation model is established. Then, the relation between the output torques of the three motors installed on one leg to the external force exerted on the foot tip is described. Furthermore, an adaptive tripod static gait is designed. The robot alters its leg trajectory to step on obstacles by using the proposed adaptive gait. Both the indirect force estimation model and the adaptive gait are implemented and optimized in a real time control system. An experiment is carried out to validate the indirect force estimation model. The adaptive gait is tested in another experiment. Experiment results show that the robot can successfully step on a 0.2 m-high obstacle. This paper proposes a novel method to overcome obstacles for the six-legged robot using spatial parallel mechanism legs and to avoid installing the electric force sensors in harsh environment of the robot’s foot tips.
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Supported by National Basic Research Program of China(973 Program, Grant No. 2013CB035501), and Research Fund of the State Key Lab of MSV of China(Grant No.MSV201208)
XU Yilin, born in 1989, is currently a PhD candidate at State Key Laboratory of Mechanical System and Vibration, Shanghai Jiao Tong University, China. His research interests include control of the legged robots.
GAO Feng, born in 1956, is currently a professor at State Key Laboratory of Mechanical System and Vibration, Shanghai Jiao Tong University, China. His main research interests include parallel robots, design theory and its applications, large scale and heavy payload manipulator design, large scale press machine design and optimization, design and manufactory of nuclear power equipment, legged robots design and control.
PAN Yang, born in 1988, is currently a post-doctor at State Key Laboratory of Mechanical System and Vibration, Shanghai Jiao Tong University, China. His research interests include design and control of legged robots.
CHAI Xun, born in 1990, is currently a PhD candidate at State Key Laboratory of Mechanical System and Vibration, Shanghai Jiao Tong University, China. His research interest is visual control of legged robots.
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Xu, Y., Gao, F., Pan, Y. et al. Method for six-legged robot stepping on obstacles by indirect force estimation. Chin. J. Mech. Eng. 29, 669–679 (2016). https://doi.org/10.3901/CJME.2016.0122.012
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DOI: https://doi.org/10.3901/CJME.2016.0122.012