Manipulability Measures of Cooperating Arms

Manipulability ellipsoids are well known tools for the evaluation of the capability of a manipulator to perform a velocity/force task. Recently, extensions of the manipulability ellipsoids to cooperating arms have been proposed in the literature, even if these approaches may suffer of some limitations. In fact, it is believed that these techniques can not deal with general manipulation systems, e.g. when some of the arms have not full mobility in the task space (defective arms), or when different contact models must be assumed between the object and the arms. In this paper, a new approach is presented for the measure of the manipulability of a multi-arm robotic system, considering the case of defective manipulators and general contact models. Examples are presented and discussed to illustrate the technique and compare it with previous methods.