Abstract In pH control system of acid injection mixture, the flow rate is easily disturbed due to the constant change of displacement in the platform acid flow control loop and the platform water flow control loop. In this study, a control strategy is proposed, that is, both the inner and outer ring controllers are linear active disturbance rejection controllers. The controller adopts linear active disturbance rejection controller, and the pH value of the mixture is controlled by cascade ratio. On the basis of the second order controller, the second order linear active disturbance rejection controller is designed based on the electric throttle valve and mixing tank model, and the simulation platform of pH control system of acid injection mixture is built by MATLAB(MATrix LABoratory)/Simulink. The controller design and simulation results of linear active disturbance rejection control algorithm and PID(Proportional Integral Derivative) algorithm are compared respectively. The simulation results show that under the interference of external uncertainties, the designed controller can not only track pH value quickly, but also reduce the overshoot and the stability time when disturbed, and effectively improve the dynamic response performance and robustness of the system.
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