Fault Diagnosis For Control Systems Based On Observers

With the development of the technology and the improvement of productivity, the modern control systems are becoming larger and more complicated. The possibility of fault arising in system is also increasing. In order to improve the reliability and security of the system, it is becoming urgent to building a monitoring system. The monitoring system is used to monitor the system states, detect the fault in system in time, analyze and judge the reason and characteristics of the fault, and take some required measures to avoid catastrophic accident. This research based on observers for fault diagnosis for control system is becoming more and more important and calling much more attention. The main content studied in this dissertation is as follow:Firstly, the dissertation introduces the theory of model-based fault detection, describe the normal and faulty model of system, and prove this method has ability to detect faults when system is in faulty. The unknown input observer is been detailed described and applied to a linear system.Secondly, the problem fault estimation is dealt with for a class of T-S fuzzy systems. The unknown input observer for general linear systems is modified to the design of residual generator for T-S fuzzy systems. This approach could increase the robustness of the residual to disturbance and obtain the desired result.Thirdly, a fault diagnosis scheme is proposed for Takagi-Sugeno systems based on an L2 Approach. With the reference model introduced, a fault observer used L2 approach is formulated to construct a generalized residual, which is used to reflect the system fault. According to the theory of Lyapunov, the sufficient conditions maintained the stability of the observer. The conditions were expressed via linear matrix inequalities (LMIs), so gain matrix L2 can be obtained by solving the LMIs. The effectiveness and feasibility were verified with calculation examples.As a summary, a brief conclusion of this thesis is given and further research in this field is discussed also.