Research On Technology Of Aeroengine Sliding Mode Fault Tolerant Control

Aeroengine is a complex system with nonlinearity,strong coupling and uncertainty,so there must be advanced control technology to ensure the engine to work safely,stably and efficiently.And it is because of the very poor working environment with high speed,high temperature,and high pressure as well as strong vibration that brings the very high frequency of occurrence of failures.In this case,the design of fault tolerant control system with the aim of improving the reliability and safety of engine is of great significance.The theory of sliding mode applied to fault diagnoses and fault tolerant control system of aeroengine is mainly studied in this paper.First of all,according to the laws of pneumatics and thermodynamics of each component of the engine in the working process,the static and dynamic mathematical model of a certain type of biaxial mixed turbofan engine is established with analytical method.The parameters of design point and the certain section of the engine are provided by Gas Turb10.The state space model with corresponding dimension is built with the least square fitting method,which lays the foundation for the following design of sliding mode controller and sliding mode observer.Next,with the reference of the classical sliding mode control theory,and the phenomenon that the reaching law based on the sign function will lead to the problem of chattering,the improved method is adopted that is to substitute the original sign function with the saturation function and continuous function respectively.The sliding mode controller is designed with the method of pole assignment.The simulation results show that the optimized approach is able to reduce the overshoot and the steady-state error.The most prominent advantage is that it can effectively weaken the chattering.Then,the sliding mode theory is applied to the fault diagnosis of gas-path components of aeroengine.Utkin sliding mode observer is designed to achieve the accurate estimation of system states.The stability of the observer is analyzed.The system is able to have the property of disturbance rejection when satisfying the matching conditions.And then the augmented sliding mode observer is designed based on the Utkin observer.The linear matrix inequality method helps to realize the health estimation of engine gas-path components.And then the gas-path components faults and sensor faults can be distinguished and isolated effectively with the method of designing a group of observers.So the multi-fault diagnosis of aeroengine is realized.Compared with the Kalman Filter,the Sliding mode observer shows the better estimation performance as well as its robustness.Finally,the simulation of active fault-tolerant control of aeroengine is realized with the combination of the theories of sliding mode controller and sliding mode observer.The result shows that fault tolerant control system can timely detect the sensor fault,estimate the fault signal and give the feedback to the controller so as to achieve the fault tolerant control.