Robust time delayed control system based on communication disturbance observer with inner loop input

This paper discusses novel structure of communication disturbance observer (CDOB) to deal with time delayed controlled system. CDOB works based on the concept of network disturbance which considers the effect caused by time delay as one kind of force disturbance and estimate its value using disturbance observer (DOB). From estimated network disturbance force, time delay is compensated to maintain the stability and performance of the system. The major advantage of this method is no time delay model requirement, thus it can be implemented easily in most cases where the time delay is unknown. However, in practice, time delay model is required to achieve robustness due to the effect of observers model uncertainty to the controlled system. A novel structure of CDOB to calculate the time delay compensation from delayed system input instead of system output is proposed. With the proposed method, the system become more robust to the model uncertainty without time delay model.