Manipulator control at kinematic singularities: a dynamically consistent strategy

This paper presents a general strategy for manipulator control at kinematic singularities. When a manipulator is in the neighborhood of singular configurations, it is treated as a redundant mechanism in the subspace orthogonal to the singular directions of the end-effector. Control in this subspace is based on operational forces, while null space joint torques are used to deal with the control in the singular directions. Decoupled behavior is guaranteed by using the dynamically consistent force/torque relationship. Two different types of kinematic singularities are identified and strategies dealing with these singularities are developed. Experimental results of the implementation of this approach on a PUMA 560 manipulator are presented