Obstacle Avoidance Algorithm for Redundant Manipulators Based on Pseudo-distance Method

doi:10.3901/JME.2020.17.059

Abstract

Abstract: Focusing on the obstacle avoidance problem of redundant manipulators, an algorithm based on pseudo-distance technique for avoiding obstacles in redundant robot control is presented without master-slaver task conversion. The proximity between the redundant manipulator and the obstacle is calculated by using the pseudo-distance algorithm with analytic form. Then the minimum Euclidean distance is obtained by analyzing the conversion relation of the pseudo-distance and Euclidean distance, leading to resolving the minimum Euclidean distance efficiently between the manipulator and the obstacle. On the one part, based on the identification index of minimum pseudo-distance, obstacle avoidance at end-effector of manipulator is accomplished by endowing a repelling velocity of end-effector along the direction of minimum Euclidean distance. On the other hand, an adaptive damping control method based on the identification index is proposed for obstacle avoidance in null space of a redundant robot, generating repelling virtual force to push robot links away from obstacles and adjusting damping factors adaptively responding to repelling force. Finally, the efficiency and effectiveness of the proposed algorithm is verified by simulations and experiments of a 7 Degree-of-Freedom (DOF) redundant manipulator. The simulation results show the oscillation of end-effector caused by the master-slave task transformation of the traditional obstacle-avoiding method is avoided and obstacle avoidance running time is reduced dramatically in the end-effector obstacle avoidance, and in the null space obstacle avoidance, the avoidance of collisions between the manipulator and the obstacle is realized successfully under the low error tracking the desired trajectory. The final experiment results show that the multiple obstacles avoidance is also implement splendidly based on the proposed obstacle avoidance strategy and the correctness of the designed end-effector obstacle avoidance method and the null space obstacle avoidance method is further demonstrated.

Key words: redundant manipulator, pseudo-distance, end-effector obstacle avoidance, null space obstacle avoidance

CLC Number:

TG242

WAN Jun, YAO Jiafeng, YU Liang, ZHANG Liangan, WU Hongtao. Obstacle Avoidance Algorithm for Redundant Manipulators Based on Pseudo-distance Method[J]. Journal of Mechanical Engineering, 2020, 56(17): 59-70.

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