Robust discrete adaptive input-output-based sliding mode controller

A robust input-output-based discrete adaptive sliding mode controller is proposed. It combines an integral action, a nonlinear output feedback, an adjustable sliding mode and an adaptive plant parameter estimator. The controller design is carried out via the Lyapunov direct method. A pole assignment procedure is developed for determination of the integral control gain and the coefficients of the sliding mode hyperplane. An on-line update for coefficients of the hyperplane is used to improve control loop behaviour further. Compared with the optimally tuned proportional-integral-derivative (PID) controller, the new controller has increased robustness with regard to the variation in the main process parameters and it has much better set point tracking characteristics. The new controller also exhibits very good disturbance rejection property comparable work or better than to that obtained by the optimally tuned PID controller. Simulation experiments are made to illustrate the quality and robustness of control achieved.