Position control of a pneumatic cylinder actuator using modified PWM algorithm

Abstract

Pneumatic cylinders are used as actuators for modern automatedsystems in many industries applications for their numerous advantages.Basically, those applications are implemented using components suchas proportional and servo pneumatic control valves that are relativelyexpensive because of their high accuracy even in applications thatdo not require such high accuracy. Recently, binary (on/off) solenoiddirectional control valves (DCVs) have been used to replace many ofthe expensive components and consequently reduce the system costwith achieving acceptable accuracy. This paper presents a controltechnique for a positioning system of a pneumatic double acting cylindercontrolled by pair of on/off solenoid DCVs. The control technique hasbeen developed based on a parametric study presented previously by theauthors[1]. The control technique depends on operating the DCVs usinga pulse width modulation (PWM) algorithm that is modified to employa valve dead-zone compensator (DZC) along with using optimumpneumatic parameters gained from the performed parametric study. Anexperimental test bed for a pneumatic double acting cylinder positioningsystem that uses a pair of on/off solenoid DCVs has been installed to testthe accuracy of the presented control technique. A comparison betweenthe performance of the positioning control technique using the modifiedPWM control algorithm and the traditional one has been carried outto experimentally show the enhancement of the positioning accuracywith acceptable maximum steady state error less than 0.7 mm whenusing the modified PWM control technique due to reducing the systemnonlinearity associated with its dynamics.