Geometrically consistent impedance control for dual-robot manipulation

The goal of the paper is the application of a geometrically consistent impedance concept to control interaction with the environment of a rigid object manipulated by a dual-robot system. A six-DOF impedance is specified at the object level to confer a compliant behavior for both the translational and the rotational motion when an external force and moment occurs at the contact. Geometric consistency is ensured thanks to the use of the unit quaternion to describe object frame orientation. The resulting object motion is decomposed into the equivalent motions at the end effectors of the two robots, via a task-oriented formulation. The control scheme is derived according to an inverse dynamics strategy with adoption of an inner motion loop providing robustness to unmodeled dynamics and disturbances. Experimental results on the two industrial robots available in the lab are discussed.