Null-space dynamics-based control of redundant manipulators in reducing impact

Abstract

This paper presents an impact control algorithm for reducing the potentially damaging effects of interaction of redundant manipulators with their environments. In the proposed control algorithm, the redundancy is resolved at the torque level by locally minimizing joint torque, subject to an operational space dynamic formulation which maps the joint torque set into the operational forces. For a given pre-impact velocity of the manipulator, the proposed approach involves generating joint space trajectories throughout the motion near the contact, which instantaneously minimizes the impulsive force which is a scalar function of the manipulator's configurations. This is done by using the null space dynamics, which does not affect the motion of an end-effector. The comparative evaluation of the proposed algorithm with a local torque optimization algorithm without reducing impact is performed by computer simulation. The simulation results illustrate the effectiveness of the algorithm in reducing both the effects of impact and large torque requirements.