Robust dual-arm manipulation of rigid objects via palm grasping-theory and experiments

An internal force-based impedance control scheme for two coordinating robots manipulating a rigid object via palm grasping is introduced. The minimal internal force required to maintain the grasp on the object is computed from the frictional constraints and sensed forces. A closed-form solution to the minimization problem is developed which makes the algorithm suitable for real-time control. The controller uses sensed moments at the palm interface to maintain proper orientation of the palms to achieve maximum surface contact. Each manipulator´s nonlinear dynamics is compensated by a robust auxiliary controller which is insensitive to robot-model uncertainty and payload variation. The controller is only weakly-dependent on each manipulator´s inertia matrix. Stability of the system is analyzed. Rigorous experimental investigations are are performed and the results presented which validate the proposed concepts