Method for Six-Legged Robot Stepping on Obstacles by Indirect Force Estimation

• Published in: Chinese journal of mechanical engineering 2016-07, Vol.29 (4), p.669-679
• Main Authors: Xu, Yilin, Gao, Feng, Pan, Yang, Chai, Xun
• Format: Article
• Language: English
• Subjects: Adaptive control; Barriers; Electrical Machines and Networks; Electronics and Microelectronics; Engineering; Engineering Thermodynamics; Experiments; Gait; Heat and Mass Transfer; Impact damage; Instrumentation; Inverse kinematics; Jacobi matrix method; Jacobian matrix; Kinematics; Legs; Machines; Manufacturing; Mechanical Engineering; Mechanism and Robotics; Power Electronics; Processes; Robots; Sensors; Theoretical and Applied Mechanics; Tips; Walking; 传感器安装; 估计; 六足机器人; 步态设计; 步行机器人; 空间并联机构; 逆运动学模型; 障碍物
• ISSN: 1000-9345; 2192-8258
• DOI: 10.3901/CJME.2016.0122.012

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.