Hybrid Fuzzy Logic Algorithm for Position Control of Pneumatic Actuator With 3/2-Way Solenoid Valves

Pneumatic positioning devices are inexpensive and also have the advantages of high speed and cleanliness. However, due to the non-linearity of the working medium, pneumatic actuators are not commonly used in industry for programmable positioning applications. Recent researches in this area are mainly concentrated on using expensive servo valves as the control element. However, the systems generally have the problems of instability and load sensitivity. In this paper, a pneumatic cylinder is controlled by a series of low-cost two-state solenoid valves. The components in the system are taken from commercial stock items that do not have the tight tolerance demanded by traditional control methodologies. The inaccuracies of the components are compensated by a hybrid fuzzy logic algorithm which incorporates additional fuzzy pulse width modulation and small deviation control logics to achieve high accuracy and repeatability at all stroke positions.