Repeatable Redundant Manipulator Control Using Nullspace Quasivelocities

This paper presents a repeatable control scheme for redundant manipulators. It is developed in terms of physically meaningful variables, a concept closely related to integrability and homogeneity. This approach sheds a different light on some well-known phenomena related to redundant manipulator control. The control is developed by determining enough physically meaningful variables to describe the manipulator's motions in the task and nullspaces, in a manner that allows them to be controlled independently. These variables are then used to develop physically meaningful controller error signals. As a consequence, all configurations in the workspace are repeatable, except for those at, or very close, to a kinematic singularity. The approach is illustrated on a 6DOF planar manipulator.