The paper describes an experimental investigation of pulse-width modulation (PWM) control of a pneumatic positioning system. PWM has been applied in the past to pneumatic positioning systems. But there are a number of different pneumatic circuit designs and PWM algorithms to choose from. This paper presents a new system design that is believed to be an improvement over previous pneumatic circuit and PWM algorithm designs. A single 3-position solenoid valve is used together with two manual flow control valves. The conventional PWM algorithm is modified with a dual switching gain to account for the valve characteristic. Test results indicate that the new system design can match the performance of previous designs. But careful consideration must be given to issues such as PWM carrier frequency and valve response times.

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