Position and force control when positioning objects with robot hands

Robot hands capable of grasping a wide variety of objects at imprecisely known locations would increase the number of industrial robot applications in manufacturing. An important part of this problem is the ability to reposition objects that have been grasped in a mislocated position. A lumped-parameter model for a two degree-of-freedom robot hand is presented and several control strategies for repositioning objects are presented. Simulations of these control strategies indicate that using position control for one finger while simultaneously using force control for the other finger gives the best combination of fast motion, acceptable grasping forces, and small steady-state positioning errors.