The Research On Nonlinear System Fault Accommodation Based On Inverse System Method

Modern control system are becoming more and more integrated, complex andsophisticated in their demand for performance, reliability and increasing autonomy. Itis inevitable for lots of sensors, actuators, and system components coordinatedoperation that the fault occurs. In order to reduce bad influence caused by failure, it isbecoming particularity important to improve system reliability and security. Themethod of fault diagnosis and fault-tolerant control was considered as one of mainsolutions, which has been a hotspot and difficulty for these problems.However, the existence of the nonlinearity in the practical plant and uncertaintyand noise of the plant models make it more and more complex and difficult. Base onthis statement, the fault accommodation approaches for nonlinear system are studied,which main works include the design of fault diagnosis observer and basic controller.The main research results are given as follows：1. In order to enhance the convergence of fault estimation of nonlinear actuatorfailure system in the existing research results, a pure integral style fault adaptivealgorithm was improved by introducing a proportional term; an adaptive observer wasdesigned to estimate the actuator fault, so that the fastness and stability of faultestimation were improved, and it was proved that the convergence of the faultdiagnosis observer could be achived in theory.2. An iterative learning observer of fault diagnosis for the weakness of actutotfault research in linear system was proposed by introducing a PD style iterativelearing strategy, which could estimatie the fault fastly and exactly. And it is alsoproved that the convergence of the fault diagnosis observer could be achived intheory.3. According to the above designed fault diagnosis observer, the fastness ofactuator fault estimation was realized, so that the research on fault conpense and therobust of uncertainty could be carried out by the guidance of inverse system methodand introducing internal model control for the existence of parameter uncertainty anddisturbances of the plant model.4. An extended state observer was designed for the switched problem of faultadaptive law in the study of nonlinear system actuator fault. An augment system wasconstruted by making the unknown system actuator fault and disturbance as an extended system state for fault detection and fault estimation to avoid the switchedproblem of fault adaptive law; and combined with inverse system method and thevalue of fault estimation to compensate the fault influence. And a robust guaranteedcost optimal controller for the compensated perseo linear system was proposed basedon the extended state observer.Finally, according to the above method for typical example of the effectivenessof simulation research, the results showed that different actuator fault estimationalgorithms given by the paper for the corresponding fault were fast, accurate; underthe situation of nomal and fault the system had a good dynamic, static, and robustperformance based on the internal model and the guaranteed cost controller of theinverse system method.