Optimal manipulation forces distribution for controlling an object motion in a four fingered robot hand (CybHand)

The real-time control of cooperating manipulators, and robots hands handling a rigid object involves the optimization of an underdetermined force system subject to both equality and inequality constraints. This paper addresses the force distribution problem in robots hands which is to solve for the setpoints of the finger contact forces and input joint torques for a particular system task. Frictional point contacts are assumed between the object and the fingers, and the aspect of task definition is to solve for joints torques even at ill-conditioned task configuration. Control laws are first formulated at the object level to provide decoupled force and position servo loops, where forces are computed using nonlinear constraints optimization technique to achieve an optimality criterion during an object motion. Numerical simulations for four fingered hand illustrate the feasibility of the approach.