Output tracking control for discrete time-varying delay systems via virtual reference model based approach

This paper proposes an output tracking control via virtual reference model for a class of discrete-time systems with time-varying delay and disturbances. In this proposed scheme, we combine a virtual reference model (VRM) and an observer-based fuzzy control strategy to develop output tracking controller. The Takagi-Sugeno fuzzy observer is used to estimate immeasurable state, while the controller is designed to guarantee the overall control system with H_∞ control performance. Sufficient conditions are derived in a linear matrix inequality form Lyapunov´s stability method. Moreover, the VRM-based fuzzy synthesis is fully illustrated by an example of discrete-time stirred tank reactor system. The effectiveness of the proposed controller is finally demonstrated and shown from satisfactory numerical results.