Nonlinear control of a novel active magnetic bearings technology based high-precision positioning stage

This paper presents modelling and control of a novel positioning stage based on Active Magnetic Bearings (AMB) technology. The stage includes a single moving part levitated and controlled with 6 degrees of freedom by 6 couples of reluctance electromagnetic actuators. The position control of the stage is achieved by simultaneous stabilization of each one of its 6 actuators. The proposed control law is an output feedback nonlinear controller combined with a velocity observer. This observer is based on the concept of approximate differentiation. The main feature of the presented positioning stage is that all 6-DOF are controlled by electromagnetic forces generated by AMB actuators. No other means, such as permanent magnets or mechanical support, are present in order to counteract the payload´s weight against gravity.