Sliding mode control based on LTR observer for PH neutralization process

A sliding mode control (SMC) method based on loop transfer reCovery (LTR) observer is proposed for the equivalent first-order model of pH neutralization process in this paper. The non-singular linear transformations is also used to make delay-free transform for the time-delay process. At the same time, two observers are designed by using LTR method: one is used to observe the system states and the other is used to estimate the variable of the sliding mode surface which is difficult to obtain. And then, integrator is used to weaken the chattering. The pH process is controlled by sliding mode controller eventually. The simulation results show that the proposed method can solve the problems of nonlinear controlled object, time-delay, and parameter uncertainty existing in the pH process effectively and the system has a strong robustness.