STABLE INTERACTION CONTROL AND COULOMB-FRICTION COMPENSATION USING NATURAL ADMITTANCE CONTROL

A new control system design formulation is presented for achieving high-performance, guaranteed-stable impedance control. While the bandwidth of the resulting controller is no higher than alternative techniques, the new formulation significantly improves performance when Coulomb friction is present in the system. The technique requires a careful choice of the target impedance. The resulting feedback compensators are causal and have stable poles, although they are often non-minimum phase. General rules for controller synthesis are derived. Experimental performance results are presented for a two-mass system with internal compliance and Coulomb friction. Results demonstrate that the technique is successful in rejecting internal friction force disturbances while maintaining a passive driving-point impedance. (C) 1994 John Wiley & Sons, Inc.