Visual servoing of 6 DOF manipulator by multirate control with depth identification

Abstract

This paper presents a visual servoing of 6 degree-of-freedom (DOF) manipulator based on intersample disturbance rejection with switching scheme. In the controller, multirate intersample disturbance rejection algorithm is utilized, which was proposed by authors for general digital control system with restricted sampling frequency. The proposed feedforward scheme with open-loop estimation and switching function enables the disturbance rejection without any sacrifice of the closed-loop characteristics. A new precise formulation of delay problems in visual servoing is established as the image processing latency, the difference between sampling period of camera signal and control period of joint servo system, and delay of inner-loop joint servo system. By introducing novel multi-loop control schemes and depth identification, the proposed intersample disturbance rejection controller becomes applicable to the complicated visual servoing problem of 6 DOF manipulator with moving object points. Finally, the advantages of the proposed control system are verified through simulations using 6 DOF robot manipulator with multiple feature points.