MODEL-REFERENCE ADAPTIVE-CONTROL OF LONG STROKE PRECISION POSITIONINGSYSTEMS WITH PIECEWISE-LINEAR GAIN

A model reference adaptive control with piecewise linear gain (PLG/MRA C) is proposed in this study to improve the performance of model refer ence adaptive control with fixed gain (FG/MRAC) in long stroke precisi on positioning system. The PID FG/MRAC and PLG/MRAC controllers were e mployed and tested on a precision stage of air-lubricated capstan driv e, DC servo motor and air-lubricated slides. The results showed that w hile PLG/MRAC demonstrated consistent performances and robustness when the stroke length varied from 25nm to 10mm and loads increased to 521 % of its original mass; PID performed poorly on both accounts and FG/M RAC, though had good resistance to varying loads, went unstable when t he stroke length increased to 3 mu m.