Air motors are widely used in the automation industry with special requirements, such as park-prohibited environments, mining, chemical manufacturing, and so on. However, during the past only few literatures discussed the dynamics of air motors or their control strategies. The purpose of this paper is to analyze the dynamics of a vane-type air motor, and design a fuzzy logic controller. It is found that the rotational speed of the air motor is strongly affected by the pressure and flow rate of the compressed air. Further, due to the mechanical friction, the overall system is actually nonlinear with dead-zone and has hysteretic behavior. The performance of conventional PI controllers implemented on the air motor usually results in large overshoot, slow response and significant fluctuation errors. To cope with the nonlinear effects of dead-zone and hysteretic behavior, we developed a fuzzy logic controller to improve the performance. The experimental results show that the proposed controller can effectively control the system with a settling time within 0.2 second, the error fluctuation less than 0.5% for high speed operation and 1.5% for low speed operation, and without any overshoot.
