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.