Experimental verifications of virtual-decomposition-based motion/force control

A virtual-decomposition-based control approach has been developed, which can accomplish a variety of control objectives without any restriction regarding the type of mechanical system that is being controlled. This paper presents experimental verifications involving two six-joint industrial robots (KUKA361 and KUKA160) performing hybrid tasks with rigid constraints. In order to achieve stable motion/force control in the presence of rigid unilateral constraints, the required velocities are redesigned by introducing filtered contact forces in all control dimensions. Based on a L₂/L_∞ stable tracking controller, the required velocities automatically provide the controlled robots with a hybrid control behavior in the case of a known contact geometry, and with an impedance control behavior in the case of an unknown contact geometry. The experiments yield consistent control results between the case of a single-arm constrained robot (KUKA361) and the case of a coordinated dual-robot system (KUKA361 + KUKA160). Furthermore, the experiments demonstrate the control stability in the presence of rigid contact, as well as very good force regulation. The transition phases from free motion to rigid contact are very smooth without any bouncing