Macro/micro-positioning control and stability analysis of contactless active robotic joint using active magnetic bearing

In clean environments, such as surgery or clean rooms, the robots with conventional joints are source of friction, dust generation, and oil lubrication. To overcome this problem, robots with contactless active robotic joint using active magnetic bearing (AMB) can be used. Moreover, this proposed kind of robots can be used in the applications that need high precision micropositioning control such as semiconductor wafers manipulation to form semiconductor devices. In this paper the macro/micro-positioning control of a novel contactless active robotic joint using active magnetic bearing is presented. In addition, the stability analysis of the controller is studied. The 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 macro/micro-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 macro-micro-positioning control.