Abstract: Two degrees of freedom controller has more advantage in the servo control. Feedback guarantees the stability of close loop system and feedforward improves the tracing performance in this controller. Firstly, closed-loop system is identified with ARMAX model. Based on this identified model, zero phase error tracing controller (ZPETC) is designed. Closed-loop band width is increased to 100 rad/s or so. Feedback loop ensures disturbance rejection and robust stability. Inner loop feedback controller is disturbance observer and outer loop is displacement feedback controller. In simulation and experiment the well tracking accuracy is achieved.

Key words: Disturbance observer, Pneumatic servo system, Trajectory tracking, Zero phase error tracing controller