In order to realize precision force trajectory tracking control of pneumatic force servo system,the control valve flow characteristics and the thermodynamic properties of the air inside pneumatic cylinder chambers were studied and then a nonlinear model of the system was developed. Since the thermodynamic model order reduction will introduce significant modeling errors, temperature observers were constructed to estimate the chamber temperature. Then, an adaptive robust controller based on full-order thermodynamic model was proposed. The 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, unmodelled dynamics and disturbances. Therefore, the prescribed output force transient control performance and high tracking accuracy are guaranteed. Experimental results demonstrate that when a sinusoidal trajectory with amplitude of 100 N, frequency of 0.5 Hz, the average output force tracking error is 1.4 N and the maximum output force tracking error is 3.9 N．It is proven that the proposed controller is effective and the adoption of full-order thermodynamic model is necessary.
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