Network-based control with compensation for time-varying delay and modeling error

In this paper we propose a control method that compensates for the following two factors in network-based control systems: one is time-varying delay on network communication and the other is modeling error due to uncertainty of the plant. For the time-varying delay, we essentially deal with it with the accurate modeling by measuring the individual time delay and utilize it for model based compensator. Because the time delay on the network is not completely uncertain but measurable value. By measuring the values and using them for the control, the performance of the system can be improved. On the other hand, the accurate modeling of the plant is very difficult and the property of the actual plant may because of the variation of loads or with age deterioration; thus the modeling error is inevitable. The modeling error appears in the form of a loop gain variation that composes the closed loop together with the phase delay caused by the time delay. Therefore, we propose a compensator whose design is based on the robust control theory for the uncertainty of the plant.