Pneumatic stage positioning with model following control and PDD² control

This paper addresses the performance improvement of positioning for a pneumatic stage. In the positioning with proportional-derivative-double derivative (PDD²) control, the stiffness and damping of a control system can be easily adjusted. However, due to unknown parameter of a pneumatic system, there is a difficulty in achieving high repeatability of positioning. To solve this problem, model following control (MFC) is combined with the PDD² control. Since, by using the MFC, the pressure in a chamber can track the output of a desired model, the repeatability is improved under the condition that the parameter of pneumatic system is unknown. It is shown that the desired model of a first-order lag system is appropriate for the positioning of the pneumatic stage. Furthermore, the difference between MFC and disturbance observer is discussed. The effectiveness of the proposed approach is shown by experiments on positioning.