Abstract: A standard projection mapping-based adaptive robust controller is proposed to achieve high-accuracy motion trajectory tracking control of a pneumatic cylinder driven by fast switching on/off solenoid valves. Due to the model errors, unmodelled dynamics and the unknown disturbances, there exist large parametric uncertainties and rather severe uncertain nonlinearities in the modeling of the pneumatic position servo system. To address these problems, the proposed controller employs on-line parameter estimation to reduce the extent of parametric uncertainties, and utilizes a nonlinear robust control method to attenuate the effects of parameter estimation errors, uncertain nonlinearities and disturbances. Therefore, a prescribed transient control performance and high tracking accuracy is guaranteed. In addition, the complete separation of the estimator design and the robust control law design is realized due to the adoption of the standard projection mapping technology. Extensive experimental results are presented to illustrate the effectiveness of the proposed controller and its performance robustness to sudden disturbances. For tracking a sinusoidal trajectory with amplitude of 0.09 m, frequency of 0.5 Hz, the maximum absolute tracking error is 1.51 mm and the root-mean-square tracking error is 0.72 mm.

Key words: adaptive robust control, fast switching on/off valve, motion trajectory tracking control, pneumatic position servo system