Coarse-Fine Composite Control of Manipulator’s End-Effector Based on Stereovision

Abstract This paper deals with the coarse-fine composite closed-loop control method of position of the manipulator’s end-effectors. A fine position tracking mechanism of the manipulator’s end-effectors is proposed, which consists of three independent prismatic joints and is fixed at the traditional manipulator’s end-link. The traditional manipulator is used in the coarse tracking of the end-effector’s position, and the mechanism is used in the fine tracking of the end-effector’s position owing to its high positioning precision caused by its shorter links. Stereovision technology is introduced into the manipulator’s control system. The object to be grasped is imaged on two CCD fixed at the end prismatic joint of the mechanism, and the two images is processed by a fast method in order to obtain the position of the object to be grasped. Then the position difference between the object to be grasped and the mechanism’s end-effectors will be feeded back to input of the controller as the error of coarse tracking. The above methods realize the coarse-fine composite closed-loop control of position at manipulator’s end-effectors based on stereovision.