A Novel Approach in Design of Model-free Fuzzy Sliding Mode Controller to SISO Chemical Processes

Abstract Sliding Mode Control (SMC) is a powerful methodology in the field of nonlinear feedback control with feature of proven robustness, performance and stability in the face of system nonlinearity and modeling uncertainties. Unfortunately, pure SMC controller suffers from two important problems; chattering phenomenon and formulation of equivalent dynamics. The aim of this paper is to design a novel model-free Fuzzy Sliding Mode Control (FSMC) to solve these drawbacks. In this method the equivalent component of the SMC is estimated using an auto-adjustable fuzzy inference system in order to remedy the model dependency problem and robustness improvement. Also, in this method the conventional switching component of the SMC is developed using additional saturation function to eliminate the chattering completely. Eventually, for verification, the proposed controller is implemented on an isothermal van de vusse reactor as a high nonlinear chemical process, subjected by unknown disturbance. It is revealed that the purposed method can improve system’s robustness and transient performance effectively in terms of complete suppression of the chattering and disturbance, specially, in the face of extra disturbances and reduction in settling time and percentage of overshoot in comparison with the two other model-free FSMC and Classical PID control.