Controlling Impact Forces in Pneumatic Robot Hand Designs

Abstract

Robot hands capable of applying controllable forces to a wide variety of objects would increase the number of robotic applications in manufacturing. One frequently overlooked part of the force control problem is the initial impact between the robot hand “finger” and the object. Experimentally determined impact forces for a variety of hand fingertip and object surface stiffnesses are presented. Impact forces predicted from low order, lumped parameter linear models are also presented for comparison. These results are used to justify velocity control as the means for reducing impact forces. Minimum time optimal control of a robot hand finger with a zero final velocity constraint would give rapid grasping with zero impact force between the finger and object. Experimental and numerical optimal control results for a pneumatically actuated finger are presented. A proof-of-concept robot hand which implements a “near-optimal” control strategy for grasping objects at imprecisely known locations is presented and discussed with experimental results.