The Research Of Sliding Mode Control For PH Neutralization Process

The pH neutralization process control is common in the chemical and biological process such as wastewater treatment,electro hydrolysis and pharmaceuticals.There are significant research interests in the pH control problem because of its environment effects and it is a challenging problem due to its high non-linearity,difficulty of modeling,extreme sensitivity near the neutralization point and time-varying gain.As early as the 50s of last century,a lot of literature has been devoted to the modeling and control problems of pH neutralization process.Because the model of pH neutralization process is complicated and the design of nonlinear controller is difficult,the study of pH neutralization process has not been systematized.At present,there are many control methods for pH neutralization process.Have their own advantages,but there are also such as poor robustness,poor real-time,complex algorithms and other defects,the need for improvement.Therefore,the study of pH neutralization process control method has theoretical value and practical value.Based on a great number of related literatures in modeling and control of pH neutralization process,firstly,the basic concept of pH,the mechanism of neutralization reaction and pH control problems are introduced in detail,and gives the derivation steps of two typical pH process model,this paper is based on the two models to discuss the pH neutralization process control the.Secondly,based on the principle of sliding mode variable structure control,this paper proposes a system state observer based on the LTR method,which is designed for the external disturbance and the perturbation of the sliding observer.With a complete invariance,can effectively weaken the sliding mode buffeting and dependence on the state.And a sliding mode variable structure control system based on LTR observer is designed for a class of uncertain input delay systems,which lays the foundation for the study of pH neutralization process control.The simulation results show that the designed controller has good control effect and robustness,and the system is stable quickly.Finally,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.For the neutralization process with time delay,a non-singular linear transformation is used to ' perform time-delay transformation.The LTR method is used to design two observers:an observing system state,an observing slip surface function is difficult to obtain the state;Implement system control,and use the integrator to shake,The control method proposed in this chapter can solve the non-linearity,large delay and perturbation.The control method proposed by this model has certain universality.At last,A sliding mode control(SMC)method based on loop transfer recovery(LTR)observer is the pH process nonlinear model based on principle of charge and carbide ion balance.This method first deals with the non-linearity of the controlled object,and designs two observers:the system state is observed by the open-loop state observer and the other is used to estimate the sliding mode variables that are difficult to estimate in the dynamic sliding mode.Structural control method for system control.The method successfully overcomes the problem of severe nonlinearity and system uncertainty in pH neutralization process,weakening the control jitter,and simulating the fuzzy sliding mode control method,showing the superiority of the method.