Pneumatic systems offer a number of advantages: typically they are fast, simple to maintain and inexpensive. However, the high compressibility of air makes control of the actuator very difficult. The purpose of this paper is to analyze the behaviors of a ball screw table powered by a vane-type air motor and then to design a robust sliding mode controller for position control. Due to the compressibility of the air and friction in the mechanism, the overall system is nonlinear. A robust sliding mode control is developed to overcome the effects of the uncertainty. Experimental results are given to validate the proposed position control strategy.