Motion Control for Object Manipulation Using Nonholonomic Constraints

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We tried to achieve the robust stable grasp with soft-fingers, which can produce larger friction forces on the object. The deformation model of the soft-finger has been established and verified by experiments. Furthermore, a motion control method where the deformation is considered has been proposed as the preliminary of the object manipulation with the nonholonomy. For the improvement of the grasp stability, the compliance control has been introduced. The stiffness coefficients and the position of gravity of the object have been related to the grasp stability by the analysis. A compliance controller with a disturbance observer has been proposed in order to overcome the large frictions of the joints of the fingers. The conditions and controller were verified by experiments. On the other hand, for the pushing manipulation with the nonholonomy, the cooperative control of the arm-hand system has been developed in the case where the grasped object is pushing to a wall. The controller is based on the manipulability ellipsoids of the arm and hand. The arm and fingers can avoid the singular orientations by the controller.