Control of a nonlinear continuous stirred tank reactor via event triggered sliding modes

Abstract

Continuous Stirred Tank Reactors (CSTR) are the most important and central equipment in many chemical and biochemical industries, that exhibit second order complex nonlinear dynamics. The nonlinear dynamics of CSTR poses many design and control challenges. The proposed controller guarantees a stable closed loop behavior over multiple operating points even in the presence of perturbations and parametric anomalies. An event driven sliding mode control is presented in this work to regulate the temperature and concentration states very close to the equilibrium points of a CSTR. The control is executed only when a predefined condition gets violated and hence, the controller is relaxed when the system is operating under tolerable limits of closed loop performance. A novel dynamic event triggering rule is presented to maintain desired performance with minimum computational cost. The inter event execution time is shown to be lower bounded by a finite positive quantity to exclude Zeno behavior. Sliding mode control (SMC) combined with event triggering scheme retains the inherent robustness of traditional SMC and aids in reducing computational load on the controller involved. Simulation results validate the efficiency of the proposed controller.