Robust time delayed control systems with communication disturbance observer

A time delay compensation method based on the concept of network disturbance and communication disturbance observer has been proposed so far. The method has the same effectiveness as that of Smith predictor and the validity has been experimentally verified. Furthermore, the advantage of the method is that it works without delay time model. However, whereas the method has been practically applied in several situations, the robustness has never been studied so far. In this paper, we present robustness of the time delayed control systems with the time delay compensation method. Some problems caused by model uncertainty and constraint on cutoff frequency are firstly discussed. Then a time delayed control system with communication disturbance observer based on two-degree-of-freedom control structure is designed. The control system makes it possible to achieve zero steady-state error. Moreover, the transient response is designed easily by parameters of controllers. Here, the transient characteristic and the attenuation performance of model uncertainty can be designed separately. Simulation results verify the validity of the control system.