Abstract: The characteristics of contact forces in grasping by dexterous hands are investigated. By decomposing the space of contact forces into four subspaces, a general formulation of contact forces is developed. It is applicable to both dexterous grasping and defective grasping. In the case of defective grasping, some components of the contact forces may not be generated by the joint torques of the fingers, thus become passive forces. These forces can be identified and decomposed by the method proposed. The contact forces can be further expressed into explicit functions of the joint torques and the external forces applied on the grasped object. The expression guarantees that optimized contact force solutions can be generated by controlling the joint torques of the fingers. Two numerical examples are provided to illustrate the method.

Key words: Dexterous hands, Grasping forces, Robots