Fault Diagnosis And Fault Tolerant Control For Aircraft Engine Sensors Based On Fractional-order Sliding Mode

The safe and efficient operation of aircraft engine depends on the engine control system,which works on the basis of sensor measurement signals.Due to the extremely harsh working environment of aircraft engines,sensors are usually exposed to high temperatures,high pressures,and strong vibrations.This makes sensors very prone to malfunction and poses a threat to the operational safety of the engine.In order to improve the safety and reliability of aircraft engine,this thesis presents researches on sensors fault diagnosis and fault-tolerant control technology of aircraft engine based on the equilibrium manifold expansion model of aircraft engine,sliding mode theory and fractional calculus.The main content in this thesis as follows:1.Taking the nonlinear component-level model of a large bypass ratio turbofan engine as the research object,the corresponding equilibrium manifold expansion model is established by identification.,which lays a foundation for the future research on fault diagnosis and fault tolerant control.2.A sliding mode observer is designed based on the equilibrium manifold expansion model of the aircraft engine.The residual is generated by comparing the output estimate of the observer with the actual output of the object.Faults can be detected by changes in residuals.In order to reduce false alarm rate and missed alarm rate,an adaptive threshold is adopted.For fault isolation,a set of sliding mode observers are designed to generate structured residual,which is able to indicated faulty sensors.3.A fractional-order integral sliding mode observer is designed based on the equilibrium manifold expansion model of the aircraft engine.When the state estimation error system switches to sliding mode,the equivalent output error injection of the sliding mode observer is used to obtain an accurate estimation of sensors fault.The fault reconstruction performance of fractional-order sliding integral mode observer is compared with sliding mode observer and integral mode observer.In order to suppress the influence of system uncertainty on fault reconstruction,the robust design of fractional order integral sliding mode observer is carried out by using L2 gain theory.4.A fault tolerant control system for aircraft engine sensors fault is designed based on the fault diagnosis technology mentioned previous.When sensor faults are detected,fault tolerance is achieved by correcting sensor measurement data by the fault estimation.Several sliding mode controllers are designed for the fault tolerant system as well,including sliding mode control,integral sliding mode control and fractional-order integral sliding mode control.Their control performance are compared and analyzed...