Control of on–off valves for linear flow characteristics is a challenging design problem due to nonlinearity of valve mechanism and fluidic properties under various operating conditions. In this study, averaging pulse width modulation (PWM) is proposed as a control valve signal by implementing PWM with predetermined duty period so that overflow at the open position and underflow at the closed position are divided proportionately around desired mean flow rates during entire cycle periods. Multichannels in a parallel pattern are implemented to yield linear flow characteristics with higher resolution than a single channel. With pressure and temperature measurements, the volumetric flow rate is determined by an empirical model of flow characteristics across flow control valves at given operating conditions. The experimental results on achieving the desired volumetric flow rate of air under actual flow conditions without a flow meter are presented for viability of the proposed methodology in practical uses.
Sequential Control of Multichannel On–Off Valves for Linear Flow Characteristics Via Averaging Pulse Width Modulation Without Flow Meter: An Application for Pneumatic Valves
Sirindhorn International Institute of Technology,
P.O. Box 22,
Pathum Thani 12121, Thailand
Contributed by the Dynamic Systems Division of ASME for publication in the JOURNAL OF DYNAMIC SYSTEMS, MEASUREMENT,AND CONTROL. Manuscript received January 24, 2018; final manuscript received July 16, 2018; published online September 10, 2018. Assoc. Editor: Heikki Handroos.
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Pawananont, K., and Leephakpreeda, T. (September 10, 2018). "Sequential Control of Multichannel On–Off Valves for Linear Flow Characteristics Via Averaging Pulse Width Modulation Without Flow Meter: An Application for Pneumatic Valves." ASME. J. Dyn. Sys., Meas., Control. January 2019; 141(1): 011007. https://doi.org/10.1115/1.4040969
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