Determination of contact forces in grasping

The determination of contact forces between a grasped object and fingers of a robot hand is treated in this research. In previous research on fingertip grasps, the underlying assumption is generally that the fingers can apply any required force. In cases of enveloping or power grasps, the latter assumption does not always hold because same components of the contact forces may not be controllable. These uncontrollable forces need to be separated in the representation of contact forces to ensure that the contact forces are obtained by adjusting the controllable components of the contact forces. This paper provides a method to solve this problem. We decompose the space of contact forces into four subspaces. Based on this decomposition, the contact forces can be explicitly represented with respect to the joint torques. Therefore, the application of the technique leads to a controllable solution. Three examples are provided to illustrate the decomposition.