Research On Fault Diagnosis And Fault-tolerant Control Of Aircraft Actuator Using Observer

With the development of space technology, orbiting spacecraft missions are becoming increasingly complex, and spacecraft failure probabilities are increasing. In the research of fault diagnosis technology, mostly diagnosis measures use system state residual. Correctness of this method is based on setting threshold. The complexity influence the certainty of fault diagnosis. Considering this problem, in this paper, fault reconstruction of thought is applied, and used for control design.Firstly, attitude control system modeling problems were studied to clear the attitude control system design method, sensor and actuator working principle. Reaction wheel dynamics model was established, and based on this model, this paper discuss the proportional differential control controller and sliding mode controller design method. This has laid the foundation for the research of fault diagnosis and fault-tolerant technology.Secondly, this paper studies the fault reconstruction method based on observer. Under the premise of precise observations of the system state, fault reconstruction is realized by using the output part of the observer. One is based on sliding mode observer, and use the adaptive law to compensate system parameters of interference. The sliding part realized fault reconstruction. This method exists a certain time lag phenomenon; Another is based on the unknown input observer. With unknown input and fault decoupling technology, the paper realize the decoupling design of both, and both were reconstructed. This method reduces the dimension of the observer, so it is easy to be realized in engineering. For the two methods, the stability of the paper is proved by Lyapunov stability theory. From the simulation results, the observer achieved the state observation accurately. For the flywheel sudden fault and intermittent fault, the two observer achieved the fault reconstruction, and the higher accuracy.Finally, this paper studies the fault tolerant control method based on pseudo inverse method, and gives the stability proof for the flywheel intermittent faults. Namely, the output torque of the flywheel has a deviation, and under the premise of accurate fault reconstruction, additional control law is used to achieve the compensation of fault information. Simulation results show the regulation effect. Although the attitude angle is still exiting bias, the bias is very small. This indicate that the method have obvious effect for intermittent faults.