On controlling robots with redundancy in an environment with obstacles

Abstract

This paper presents a method to solve the problem of obstacle avoidance for a redundant manipulator so that it closely tracks the desired end-effector trajectory and simultaneously avoids workspace obstacles. The proposed method introduces the describing function J to indicate whether collision occurs between the robot and obstacles. The obstacle avoidance task is achieved by formulating the performance criterion J > Jmin (Jmin represents the minimal distance between the redundant robot and obstacles), and by using configuration control to ensure that this criterion is satisfied. The calculation of J function is only related to some vertices which are used to generate and model the robot and obstacles, and the computational times are nearly linear with the total number of vertices. The configuration control algorithm which achieves end-effector motion and obstacle avoidance does not require either a complex dynamic model or complicated inverse kinematics transformations of the robot. Several simulation cases for a four-link planar manipulator are given to prove that the proposed collision-free trajectory planning scheme is efficient and practical.