Novel Cylinder Positioning System Realised by Using Solenoid Valves

This paper presents a novel control design, developed to realise fast and accurate position control of a pneumatic actuator using inexpensive on/off solenoid valves. In contrast to conventional control methods, the proposed control method operates chatter free, based on air compression. The control principle was developed by investigating the dynamics of a pneumatic actuator with an identified mathematical model. This new approach is applied to a pneumatic double acting cylinder, controlled by a pair of 5/3 way directional single solenoid valves. The described closed-loop circuit copes with the discontinuities associated with the valve’s switching dynamics, and relatively long response time. The experimental apparatus uses an analogue displacement encoder for metering the piston’s position and velocity, and doesn’t incorporate pressure sensors thus ensuring a low cost system design. The results of experiments with various step responses show that the proposed control method performs well. The measured steady-state position errors are equal to the used potentiometer’s travel resolution, which is 0,01 mm. Therefore this novel control and the related pneumatic system design could be a cost effective alternative to the servo-pneumatic positioning systems.