Accurate position control of a pneumatic actuator using on/off solenoid valves

The development of a fast, accurate and inexpensive position controlled pneumatic actuator that may be applied to a variety of robotic applications is described. A novel PWM valve pulsing algorithm allowed on/off solenoid valves to be used in place of costly servo valves. A linear process model was obtained from experimental data using system identification. A PID controller with added friction compensation and position feedforward was successfully implemented. A worst case steady state accuracy of 0.21 mm was achieved with a rise time of 180 ms for step inputs from 0.11 mm to 64 mm. Following errors to 64 mm s-curve profiles were less than 2.0 mm. The controller was robust to a six fold increase in the system mass. The actuator's overall performance is comparable to that achieved by other researchers using servo valves.