Analysis and classical control design of servo system using high order disturbance observer

In earlier papers, it has been reported that a fast and precise servo system, which has low-sensitivity to parameter variation and disturbance, can be realized with simple structure by using a high order disturbance observer. However, a clear and simple design method satisfying specifications for robust stability, influence of measurement noise, and relative stability has hardly been proposed. In this paper, we clarify the class of the robust servo system realized by adjusting the order of the disturbance observer and show design of an estimated disturbance feedback by the disturbance observer, which can represent a classical control approach. We apply this strategy to a design of a position servo system and realize the high performance robust servo system using the high order disturbance observer.