Digital Control of Pneumatic Cylinder

摘要

This paper describes a method to control a pneumatic cylinder using digital techniques.The pneumatic cylinder has been used as an actuator for industrial robots, because it is simple, small and economic. However it is difficult to decide precisely the position of the piston rod, owing to the air compression and the friction of the device itself.There is a servo system in one of the cylinder's positioning controls. This method can realize the positioning control system with high accuracy. However, the overshoot becomes big when the moved distance is long.We are trying to create a positioning control with least overshoot and high accuracy by using a new method of combined position control and speed control. However, the manipulated variable is often not continuous, and the overshoot becomes big if there is an error in the changing point from speed control to position control.We therefore guide the speed control system from the position control system by applying the optimal control theory that pays attention to the inside condition of the system. This new method gives continuity of the manipulated variable. As a result, we have been getting comparatively high precision with least overshoot.Furthermore we propose a method that is able to obtain the positioning accuracy below resolution of a sensor.