Control of a Dual-Stage Positioning System Consisting of two Permanent Magnet Linear Motors for High-Precision Applications

Dual-stage actuators are used in applications with high requirements for positional accuracy. One of the most widespread types of these actuators uses voice coil motors for fine positioning. In this paper, a control strategy for a dual-stage actuator consisting of two permanent magnet linear motors is investigated. The control strategy is developed based on the mechanical model of dual-stage actuator and consists of a control concept as well as a decoupling algorithm of the two stages by means of a force feedforward control and a Luenberger Disturbance Observer. With this control strategy, the two stages can finally be decoupled from each other and the fine positioner can be linearized so that its control behavior is similar to that of a voice coil motor. With this setup, the position error of a permanent magnet linear motor can be improved significantly compared to a single-stage system also using a disturbance observer.