Design and control of dual-stage feed drive system in ultra-precision machine tools

The design and control of a Dual-stage Feed Drive (DSFD) system on a ultra-precision machine is presented. The DSFD system combining coarse (large stroke) and fine (fine resolution) drive stages in series is designed to provide the desired performance, in which a step motor is used for the coarse motion to obtain the large stroke and fast response speed, and a piezoelectric micro-actuator for the fine motion to achieve the high resolution and accuracy. A control system for the mechanism is developed based on a multiple model-based switching controller, and a movement distribution module is designed for the motion coordinations of coarse and fine movements. Finally, a experiment is undertaken by controlling both stages separately for the actual position on the DSFD system and a measurement is carried out by a laser interferometer. The experimental results show that the step motor has a working stroke of 90 mm with the displacement resolution of 0.3 μm and the piezoelectric micro-actuator has a working stroke of 40 μm with the positioning accuracy of 0.9 μm. The theoretical and experimental results show the validity of the control algorithm.