Impedance control for multi-arm manipulation

In this paper a geometrically consistent impedance concept is applied to control a multi-arm system. The case of a common rigid object rigidly grasped by the manipulators in the system is considered. A six-DOF impedance behaviour is enforced at the object level so as to keep limited the force/moment due to the interaction with an external environment. Moreover, in order to avoid large internal forces, a six-DOF impedance behaviour is imposed at each end-effector. The adoption of the unit quaternion to describe object frame orientation ensures consistency with the task geometry. The overall control scheme is of inverse dynamics type with an inner motion loop which provides robustness to unmodeled dynamics and disturbances.