An approach to design of feedback systems with time delay

Because of the distinctive characteristics, time delay is even now a difficult and unresolved problem in control engineering. Therefore many compensation methods of it have been proposed so far. The most famous one of them all is Smith predictor. It is a kind of prediction method and equivalently eliminates time delay from closed control loop. State predictive control is briefly an extension of Smith predictor in state space. However it should be noted that the performances of these methods deteriorate in case that time delay is fluctuant and unpredictable. In this paper, a new approach to design of feedback systems with time delay is proposed. It is based on innovative time delay compensation method by disturbance observer and the concept of network disturbance. Because this method does not need delay time model, it is applicable to the system with fluctuant and unpredictable time delay. Furthermore it also considers suppression technique of disturbance. Then new controller that can be designed regarding transient and steady-state response separately is proposed. The validity of proposed method is verified by simulation and experimental results.