Design of robust controller for liquid level system using disturbance rejection control based on prediction

The prime design objective of control system is to reject disturbances, to track set-point and ensure stable of closed loop response. The delay in input and slowness of process operation is observed in the many process applications. These issues create problems in control of processes. The intention of work is to develop a functional design that keeps the process status within admissible limits of delay. An approach of controller to reject disturbance on the basis of prediction is implemented in discrete time control system. An observer with extended state is used to estimate plant state and also the output without delay is obtained using filtered Smith predictor. The controller is designed for control of liquid level system. Simulation study is presented and the performance of designed controller is far better than conventional controller.