Dynamic compensation of modeling uncertainties and disturbances of a precision planar motion stage based on sliding mode observer

This paper discusses dynamic modeling, controller design, simulation, and experiment for a non-contact three-degree-of-freedom planar motion stage for precision measurement and control of positions. A simplified model of this planar motion stage driven by four permanent magnetic linear motors is established on an assumption that the influence of the small yawing motion on the electromagnetic characteristics of the planar motion stage can be neglected. Overall control strategy, including a fine-tuned proportional integral derivative component to yield basic dynamic performance and a component derived from sliding mode observer to estimate and compensate for modeling uncertainties and disturbances, is developed and implemented in a digital signal processor. Simulation study and experimental results of using a three-axis interferometer as the position sensor are presented to verify the effectiveness of the suggested dynamic compensation strategy and tracking performance of the non-contact planar motion stage.