Abstract
Applications requiring accurate position control of cylinders are in increasing use in industry. Pneumatic cylinder systems have the potential to fulfill this requirement due to their high speed and reliability at a relatively low cost. This paper outlines a technique of repeated positioning of a pneumatic cylinder. The system runs with a sequential on-off action of air valves as its basic control algorithm. To acquire accurate positioning at the time of each operation, three proximity switches are installed for one desired stop position to detect the slider passing as well as its velocity. In this scheme, less deviation of the stop position can be obtained by braking within a certain range of velocity which can affect the positioning performance. It is experimentally suggested that there is an optimal velocity for starting to apply the braking. The results are analyzed by simulation to validate that the existence of an optimal velocity is strongly related to the frictional fluctuation and the braking characteristics. Finally, experiments of repeated positioning are conducted to show the effectiveness of the proposed braking method.
