Smith predictor–based sliding mode control with hyperbolic tangent function for unstable processes

In this work, a modified Smith predictor–based sliding mode control (SP-SMC) method is proposed for unstable plus time-delay processes. Sliding mode control has a discontinuous part in its control law which may cause chattering in the control signal if conventional switching strategy is used. A hyperbolic tangent function is employed as a switching element in the suggested SP-SMC technique to minimize the chattering effect. Optimal values of the controller’s unknown parameters are obtained using whale optimization algorithm which is a meta-heuristic technique. The process model used in the proposed Smith predictor control architecture is identified using measurements of limit cycle output which is obtained from online relay test. The proposed controller is found to be robust towards process parameter uncertainties and load disturbance. Suggested control technique results in fast set-point tracking response and significantly improved disturbance rejection performance compared to some other related methods.