Increased tracking ability of pulse width modulation-driven pneumatic servo systems via a modified pneumatic circuit

Abstract

In this article, to increase the tracking ability of pulse width modulation (PWM)-driven pneumatic servo systems, the pneumatic circuit is modified such that an identical PWM signal is demanded by both fast switching valves. As a result, the problem of allocating different duty cycles to the valves is vanished, due to the synchronized pulsing inputs. A simple PWM algorithm is applied to compensate the dead zones in the relation between the duty cycle input and the valve flow output. An experimental investigation is carried out to indicate the capabilities of the proposed circuit. Closed-loop tests are implemented and high tracking performance for frequencies up to 5Hz are obtained, whereas experiments with frequencies up to 1Hz were reported in previous studies. In similar conditions of load and cylinder size, experiments of the proposed circuit indicate acceptable results with simple PD controller, compared with the more complicated controllers and circuits of previous studies.