Spatial impedance control of redundant manipulators

Abstract

This work is focused on impedance control of redundant manipulators. A spatial impedance formulation is presented where general 6-DOF end-effector tasks can be handled. A singularity-free angle/axis representation of end-effector orientation is used which allows geometric task consistency to be preserved. An inverse dynamics control with a dynamically consistent inverse of the geometric Jacobian matrix is developed with the adoption of an inner loop acting on the end-effector position and orientation conferring robustness to unmodeled dynamics and external disturbances. Stabilization of null-space velocities is ensured and utilization of redundant degrees of mobility is carried out to optimize an additional task function. Experimental results on a seven-joint industrial robot with force/torque sensor are discussed.