Kinematics and internal force in grasping multiple objects

Discusses the analysis of kinematics and internal force under the gravitational field in grasping multiple objects. We first provide a general, mathematical formulation on the kinematic relationships for multiple objects grasped by a multifingered hand. We show a sufficient condition for lifting up two objects toward the palm. An experimental result verifies that the sufficient condition can be easily satisfied. We also analyze the internal forces for grasped objects, and introduce an index for evaluating the degrees of freedom of internal forces. Finally, we show a couple of examples to explain the physical interpretation of internal forces in connection with the index