Research On Fault Diagnosis And Accommodation Technology Of Chemical Liquid Storage Tank Level Control System

The rapid development of modern science and technology has made the chemical process increasingly complicated,refined and large-scale.For complex large-scale chemical production processes,fault diagnosis is essential to ensure safe production.Since chemical production has been in a state of non-stop production for a long time,long-term work will lead to some unavoidable component loss and line aging failures.As a result,production system downtime affects economic benefits,and even causes serious consequences such as explosions.This paper combines the most common liquid level control system of the liquid storage tank in the relevant chemical process,and models it as a switched system model to study the fault diagnosis.At present,for the research of switched systems,many of the literatures mainly focus on the analysis of the stability of the system,but the research on the fault diagnosis of the switched system is relatively rare.Therefore,its application in the field of chemical processes is greatly limited.In this paper,the chemical liquid storage tank liquid level control system is modeled as a fault diagnosis problem of the switched system based on the observer method.The research content of this paper is as follows:1.Research the problem of the fault detection filter design for liquid level control system with actuator faults.The actuator faults and the unknown disturbances are considered to be in finite frequency domain.By using the switched Lyapunov function and the average dwell-time techniques,efficient conditions are obtained,which can realize the residual signal sensitive to the fault and robust to the unknown disturbances.Linear matrix inequalities conditions are proposed to design the fault detection filter,which can guarantee the finite frequency H_- and H_? performance index.Finally,a practical example is provided and simulation results are conducted to demonstrate the effectiveness of the proposed approach.2.Research the problems of non-fragile fault estimation and fault accomodation for liquid level control system are investigated.Firstly,a non-fragile proportional integral observer is designed to achieve actuator FE for continuous-time switched systems.Based on the average dwell-time method and the switched Lyapunov function technique,a new actuator fault estimator is obtained.Then,based on the online FE information,a PIO-based non-fragile state feedback controller is designed to compensate the effect of the actuator fault by stabilizing the closed-loop switched system.Finally,an example is given to illustrate the correctness of the conclusion.3.Research the problems of fault estimation observer and optimal fault tolerant controller design for liquid level control systems are addressed.In this chapter,we study a class of singularly perturbed linear systems and reconstruct the system with the designed fault signal system.Construct a new augmentation system.Based on this,a full-dimensional proportional integral observer is solved.Then the optimal performance of the system is further discussed,and a state feedback controller that can make the system progressively stable is designed,and it can satisfy the linear quadratic optimal performance index to a minimum.Then through the specific examples,the effectiveness of the proposed method is verified by MATLAB simulation technology.Finally,an optimal fault tolerant controller is engineered to ensure that the closed-loop system have optimal performance.