IMPLEMENTATION OF DAMPED RESOLVED ACCELERATION CONTROL FOR A MANIPULATOR NEAR SINGULARITY

Abstract

Resolved acceleration control fails in the neighbourhood of the singularity of the Jacobian matrix. The damped least-squares method has been proposed to overcome this singularity problem. In earlier work, all components of the velocity of the end-effector were damped when a manipulator was near a singular point, so that some components of the velocity that are physically feasible were also damped, sacrificing accuracy. This paper presents a new approach that applies the damped least-squares method only to the degenerated directions since only the components of the velocity in the degenerated directions are inherently impossible to generate. This approach requires few computations and then can be implemented in real-time. Another feature is that the selection of the damping factor is a one-dimensional problem. The new damped resolved acceleration control scheme is implemented on the Puma 560 robot. The experiment results show the validity and the drawbacks of the damped resolved acceleration control in the neighbourhood of singular points.