Comparison of contorl Strategies for Piezoelectric and Magnetostrictive Micropositioning Devices for Ultra-Precision Machining

摘要

Ultra-precision machining to sub-micrometre depths is shown to be a threshold area of work requiring a combination of the best of materials, sensors, positioning devices (actuators) and control strategies. In ultra-precision design, it is extremely likely that there will be few design options for selection. In the case of ultra fine tool feed, the piezoelectric actuator is a potential choice. Currently, European and Japanese tool manufacturers are investigating magnetostrictive actuators for this purpose. Bot hpiezoelectric and magnetostrictive materials suffer from hysteresis type non-linearity, so that the output of such systems depends upon the previous input, and absolute positioning is only achiveable with the aid of feedback control. This work compares some modern control techniques for the positioning of a tool post for ultra-precision machining of brittle materials (in the nanometric range), eg, lead-lag Filter, PID with feedforward and fuzzy logic. The performance of the micropositioning device (tool post) using both piezoelectric and magnetostric-tive actuators is assesed by means of simulation techniques. The predicteis performance is compared with resutls obtained by other authors.