New fuzzy control- based grasping algorithm for a novel compliant robot gripper

Abstract

This paper presents a fuzzy controller for two-finger gripper, one finger is fixed and the other is movable. Control system input / output variables ldquospeed command for servo motor driver / rate of force increaserdquo are measured and processed to model the mechanical system. A new grasping and control algorithm is proposed which adjusts the motion of one finger of the gripper without the risk of object crushing or dropping and also to maintain the object slip in a reasonable limit. The rules set of the proposed algorithm is derived empirically by investigation of the human hand skills that layer control approach can be implemented on different stages. Based on these stages, three fuzzy controllers was employed, the first controller is to guess the acceleration of the object resulting from few applied force and gives the suitable value of speed command, the second controller is to sense the pushing force to the object before the grasping process and its output is added to the first controller, the third controller is to enhance the behaviors of the first ad second based on the object acceleration and the applied force feed back. The controllers receive the object acceleration, object acceleration rate, pushing force and the applied force and adjust the finger motion. The designed controller is quite robust because knowledge concerning the size, the weight, or the surface texture of the grasped object is not required. The control system is simulated and the experimental results are obtained to demonstrate the efficiency of the introduced algorithm.