Variable structure slip control for grasping objects

Abstract

A variable structure slip control strategy is developed for grasping objects by a robot end-effector. A hybrid controller comprised of a fuzzy controller and a PI controller is designed to perform the strategy. When a grasped object is slipped by an external force as a disturbance, the applied fingertip force is rapidly increased to stop sliding and then decreased to a reliable limit to hold the object. The control structure is automatically changed from PI control to fuzzy control if the slip is higher than the predetermined limit. The control system is simulated for a two fingered robot hand driven by permanent magnet dc motors.