Abstract: To improve the control bandwidth and the performances of an ultra-precision positioning stage which has mechanical resonant and system delay, an optimized loop shaping (OLS) controller design method is presented. Analysis based on loop shaping design method shows that insufficient phase lead of the PID type controller is the major bandwidth limiting factor. And a higher order controller promising to achieve a higher control bandwidth is proposed. Controller parameters design is described as an optimization problem with loop shaping (LS) design method, and then solved by generic algorithm. Comparative experiments are carried out between the OLS controller and the PID controller tuned by trial and error. The results indicate the performances such as rising time, setting time and positioning error improve considerably, while the maximal overshoot increases somewhat but remains in the allowable range of engineering practice, which validates the effectiveness of the proposed method.

Key words: Control bandwidth, Controller optimization, Generic algorithm, Ultra-precision positioning stage