Development of a Pulse-Width Modulated Pneumatic Rotary Valve for Actuator Position Control

A new concept in the directional flow control of a high speed pneumatic actuation system is proposed. Two recent developments reported in the literature, namely (i) the application of pulse-width modulation techniques to on-off pneumatic valves and (ii) the introduction of a high speed rotary air valve, are merged in the design of a novel rotary flow control valve with built-in pulse-width modulation. Valve feasibility is demonstrated experimentally through the closed-loop position control of a pneumatic actuator. Static and dynamic performance characteristics as predicted by a detailed nonlinear lumped parameter model, compare favorably with measured data. Additionally, a simple linear time-invariant model, with a few empirical parameters, of the system is developed and validated through comparison with experiment and the nonlinear model. Then, several system design improvements based on this simple linear model are implemented and evaluated with the detailed nonlinear model.