Singularity robust manipulator control using virtual joints

Abstract

A singularity handling method is proposed in this paper. It is done by introducing virtual redundant joints into the Jacobian matrix to maintain the rank of the Jacobian matrix when singularity occurs. These additional joints do not exist physically. Therefore, although mathematically stable, the manipulator still cannot perform tasks in the degenerate direction(s). This method is comparatively straight forward to implement and it does not have a singular subspace defined within which a special and different control algorithm is performed, thus it avoids the problem associated with discontinuous control or switching of control. The method was tested on simulation and implemented in real-time on the PUMA 560 robot.