Pneumatic cylinders are used as actuators for modern automated
systems in many industries applications for their numerous advantages.
Basically, those applications are implemented using components such
as proportional and servo pneumatic control valves that are relatively
expensive because of their high accuracy even in applications that
do not require such high accuracy. Recently, binary (on/off) solenoid
directional control valves (DCVs) have been used to replace many of
the expensive components and consequently reduce the system cost
with achieving acceptable accuracy. This paper presents a control
technique for a positioning system of a pneumatic double acting cylinder
controlled by pair of on/off solenoid DCVs. The control technique has
been developed based on a parametric study presented previously by the
authors[1]. The control technique depends on operating the DCVs using
a pulse width modulation (PWM) algorithm that is modified to employ
a valve dead-zone compensator (DZC) along with using optimum
pneumatic parameters gained from the performed parametric study. An
experimental test bed for a pneumatic double acting cylinder positioning
system that uses a pair of on/off solenoid DCVs has been installed to test
the accuracy of the presented control technique. A comparison between
the performance of the positioning control technique using the modified
PWM control algorithm and the traditional one has been carried out
to experimentally show the enhancement of the positioning accuracy
with acceptable maximum steady state error less than 0.7 mm when
using the modified PWM control technique due to reducing the system
nonlinearity associated with its dynamics.