Research On Fault Reconstruction Of Longitudinal Flight Control System Based On Observer

Since commercial aircrafts will encounter complicated and variable external ambient environments during flight,various adverse factors will affect the reliability and stability of flight control systems with different levels.This might result in various operational risks and even cause serious flight disasters.Therefore,based on the existing flight control systems and external ambient environments characteristics,the analyses of scientific and effective system fault-reconstruction mechanism can significantly improve the performance of control systems and improve the safety of aircraft flight.Sensor fault detection is studied for flight control systems with bounded disturbance inputs.By non-singular linear transformation of the output signal,the sensor fault is equivalently transformed into the actuator fault,and the residual generation method which is robust to the interferences and sensitive to the fault is proposed in this thesis.The sliding mode observer is designed to estimate the residual.The detection of the sensor fault is realized,the accurate estimation of the sensor fault signal is obtained,and the reconstruction of the sensor signal is realized.Simulation results demonstrate the effectiveness of the proposed method.For nonlinear flight control systems satisfying the Lipschitz condition,the robust reconstruction problem for actuators and sensors faults happened simultaneously case is studied based on the sliding mode observer.A linear transformation matrix is introduced,and a post filter is added to construct the dimension-increasing system.Combined with H_?control,the robust sliding mode observer gain matrix design method is transformed into a multi-objective convex optimization problem under LMI constraints.An adaptive law is introduced into the sliding mode gain to ensure that the state estimation error is asymptotically stable.On this basis,an actuator and sensor fault reconstruction algorithm is given.Simulation experiments demonstrate the effectiveness of this algorithm.A fault reconstruction method based on PD-type(Proportion Differentiation,PD)iterative learning observer is proposed for longitudinal flight control systems that satisfy Lipschitz conditions with actuator failures and external disturbances.The design method of systematic iterative learning observer is proposed based on linear matrix inequality techniques.The stability conditions of the above design method are proved theoretically according to Lyapunov stability theory.The method has demonstrated the expected robust performance index,and can accurately reconstruct the fault types such as sudden faults and time-varying faults in the presence of random disturbances and measurement noises.The simulation results show the effectiveness of this fault reconstruction method.