Experimenting and modelling the dynamics of pneumatic actuators controlled by the pulse width modulation (PWM) technique

In this paper an extensive set of experiments and a related mathematical model investigating the dynamics of pneumatic actuators controlled by on-off solenoid valves, whose opening and closing time response is based on a pulse width modulation (PWM) technique, is presented. The experimental set-up consists of both commercial electronics and circuits appropriately realized where particular needs are required. As well as providing a highly repeatable set of measurements, valuable for future comparisons, the experimental investigation also provides an appropriate base aimed at testing the performances of the analytical model. The analytical-experimental comparisons show the ability of the theoretical model to provide an accurate mean expectation of the position of the actuator less than about 2 mm. Such a capability of the model is tested for several operating and initial conditions during the first five cycles. The present theoretical model dealing with a non-linear dynamics phenomena whose behaviour is highly transient should be considered an attempt aimed at providing a valuable tool for designing control strategies without the need for expensive physical models.