Robust H-infinity tracking control of MIMO nonlinear systems. Application to non-isothermal CSTR

A non-isothermal Continuous Stirred Tank Reactor (CSTR) is the most important element of chemical industrial equipment which exhibits a highly nonlinear behavior. It is one of multi-input multi-output (MIMO) nonlinear systems affected by disturbances. The operation of the non-isothermal CSTR is disturbed by external factors such as changes in the inlet concentration and temperature. Therefore, the two difficult issues in CSTR control are tracking trajectory and external disturbance attenuation. In this paper, a robust fuzzy tracking control via Takagi-Sugeno (T-S) MIMO systems is designed to robustly stabilize the non-isothermal CSTR system for both concentration and temperature schemes exposed to external disturbances. Takagi-Sugeno fuzzy approach for describing nonlinear model with several local linear models is proposed, and using a technique called Parallel Distributed Compensation (PDC), we derive LMI conditions for analyzing robust stability and performance based on Lyapunov functions, and a criterion is employed to guarantee the attenuation of disturbances. In trajectory tracking framework, an integral action is introduced as a new state variable. Finally, simulation results are given to prove that the proposed technique ensures the stability conditions and guarantees robustness against external disturbance with a good trajectory tracking.