Robust control employed QFT for a pneumatic position servo system using on/off solenoid valves

A nonlinear model on pneumatic position servo system based on solenoid valves is built, in which the hysteresis of the solenoid valves is taken into consideration. Further a parametric uncertainty pseudo linear model with time delay is conducted with feedback linearization. As to deal with the robust control problems against parameter uncertainty, noise and load disturbance, quantitative feedback theory (QFT) is employed to shaping the loop transmission, which is expected to own robust stability, robust disturbance rejection and tracking behaviour. The controller adopts the structure of two DOF, which owns an inner feedback loop in order to increase the damping. Friction compensation is also introduced to promote its performance. Finally the experiments based on the controller verify that the servo system embodies robust stability, dynamic performances of accurate and quick response.