Robust internal-force based impedance control for coordinating manipulators-theory and experiments

Abstract A robust internal force-based impedance control scheme for coordinating manipulators is introduced. Internal forcebased impedance control enforces a relationship between the velocity of each manipulator and the internal force on the manipulated objects and requires no knowledge of the object dynamic model. Each manipulator's nonlinear dynamics is compensated by a robust auxiliary controller which is insensitive to robot-model uncertainty. The controller is only weakly-dependent on each manipulator's inertia matrix. The scheme is computationally inexpensive and suitable for general-purpose microcomputer implementation. Stability of the system is analyzed including the e ects of computational delays on both a single-arm manipulator in contact with a rigid surface and a dual-arm system manipulating a rigid object. We show that the inertia matrix has a lower bound with respect to the estimated manipulator Cartesian end-point inertia which is independent of the sampling period. Rigorous experimental investigations are performed and the results presented which validate the proposed concepts.