Synthesis and comparison of fine actuator controllers for a 3-DOF micro parallel positioning platform

This paper presents the controller synthesis for a fine actuation system of a 3-DOF micro parallel positioning platform. The platform is composed of a dual stage servo system for realizing both long stroke and high precision, simultaneously. Among the dual stage, the fine actuation system is more important as it guarantees high speed and accuracy. First, a physics-based model for the fine actuation system is developed through the constraint equations of the parallel mechanism and the dynamic equations of the fine actuation system. Several experiments have been conducted and unknown physical parameters such as the stiffness and the damping coefficients were estimated to precisely predict the dynamics of the fine actuation system. Equipped with the physics-based model, the PID-based controller, mixed-sensitivity H₂ and H_infin controllers were designed to accomplish both high accuracy and fast response of the micro positioning platform, respectively. The satisfactory performances of the synthesized controllers were successfully verified and compared with one another through extensive simulations and experiments.