Adaptive object impedance control of dual-arm cooperative humanoid manipulators

A novel adaptive object impedance control strategy is presented for dual-arm cooperative humanoid manipulators. A general impedance scheme comprising internal impedance control and object impedance control is adopted, which aims at conferring a compliant behavior both in end-effector level and object lever. The adaptation law for the stiffness and damping of object impedance is derived from Lyapunov stability theory. In contrast with general object impedance, the proposed controller can exhibit different impedance characteristics according to the force exerted by environment on the object and can achieve minimizing the metabolic cost of the adaptation process. Simulation results show the object impedance controller exhibits explicit compliance behavior when the interaction with environment is weak and presents accumulation property of the stiffness and damping when the interaction is strong.