Micro/macro-positioning control of a novel contactless active robotic joint using active magnetic bearing

Abstract

In this paper the micro/macro-positioning control of a novel contactless active robotic joint using active magnetic bearing (AMB) is presented. In clean environments, such as surgery or clean rooms, the use of robots with this novel joint is useful to avoid friction, dust generation, and oil lubrication. Moreover, this kind of robots can be used in the applications that need high precision micropositioning control such as semiconductor wafers manipulation to form semiconductor devices. The novel robotic joint used in this paper is designed using finite element method. This joint has 6 degrees-of-freedom (DOFs), 1-DOF for robot joint roll angle and 5-DOF for AMB. The robot joint roll angle is controlled in macro-scale accuracy. The macro-scale positioning of the joint roll angle is needed for gross motion like normal robot revolute joint. The other 5-DOF of the joint are controlled like AMB with the different that the target pitch and yaw angles as well as the axial, vertical and horizontal movements are different than zero but in micro-scale range. The robot joint roll angle is controlled using a PID-based Feedback linearization controller, while a state feedback controller with integral term is used for controlling the AMB 5-DOFs. The micro/macro-positioning control of the novel robotic joint is implemented using MATLAB/Simulink. The robustness of the controllers is tested against payload variations. The results demonstrate that the proposed novel robotic joint is feasible and valid in the applications that need high precision micro-macro-positioning control.