The dynamic modeling and dynamics response analysis of ultra-precision drive machine

Ultra-precision drive machine (UPDM) is a complex drive system, which is characteristic of lubricating with air-bearings and driving with linear motor and planar motor together. The reticle stage in high resolution step & scan projection-lithography utilizes this drive system to achieve high-speed and high-precision motion with 10nm positioning accuracy. With respect to the effect of dynamic characteristics of the stiffness of air-bearings, air-bearings and flexible joints are equivalent to linear springs and a dynamic model is established. Dynamic parameters are obtained by the integration of experimental modal tests and dynamic simulations. Based on the model, the dynamic response is analyzed and the acceleration response curves are obtained in X, Y and Z-direction, respectively. These simulation results are in good agreement with those of the experiment and the deviation is 4% below, which shows the dynamic model is reasonable and feasible. Natural frequencies and vibration modes are obtained. The displacement response of the mover of LSM and the stator of SSM are obtained by transient response analysis, which demonstrates the variation of air pressure, air flow and magnetic forces will influence on positioning accuracy of the system.