Robust Control And Safety Protection For Aero-engine Based On Switching Strategy

Aero-engine is a strongly nonlinear,time-varying and complex pneumatic thermodynamic system.More and more experts and scholars who are in the field of control pay attention to aero-engine control problems.In this thesis,a turbofan engine is used as the research object.The thesis sets up a turbofan engine equilibrium manifold expansion(EME)model which can be expressed as analytical expressions.In order to study the control problem of the engine complicated operation process,the thesis designs the state feedback controllers and the switching strategy to improve the dynamic quality of the turbofan engine.To solve the control problem of EME model with external distractions,the thesis designs robust H_?controllers based on the switching strategy.For the safety protection problem of the turbofan engine,the thesis designs the speed protection controller loop and an appropriate switching strategy based on the theory of multi-loop switching control.The main contents can be stated as follows:Firstly,according to the actual test data of a turbofan engine,the thesis uses the two-step static separation identification method to establish the model of the turbofan engine equilibrium manifold expansion which can be expressed as analytical expressions.For the control problem of the engine complicated operation process,the thesis selects different equilibrium points in the scope of the EME model and establishes the linear model and state feedback controllers around these points.An appropriate switching rule on running states is designed for the EME model to improve the dynamic quality.The simulation validates that switching control between state feedback controllers have more advantages than single controller control.Secondly,in order to improve the turbofan engine control accuracy,the thesis establishes the EME model with external distractions and designs robust H_? controllers based on the switching strategy.The thesis selects several equilibrium points in the scope of the EME model and establishes the linear model with uncertainty and external distractions and state feedback controllers around these points.According to the robust H_? control theory,the thesis designs robust H_? controllers around these points and appropriate switching rules which can make the EME model asymptotic stabilized and satisfy with the H_? performance ?.The simulation validates that robust H_? controllers based on the switching strategy can make a good control effect.Finally,for the safety protection problem in the turbofan engine,considering the contradiction between the engine speed dynamic rapidity and the engine security,the thesis uses the theory of multi-loop switching control to design the speed protection controller loop.Based on the engine speed safe boundary,an appropriate switching strategy is designed for the EME model.When the engine speed is closed to or over the safe boundary,the EME model control system can switch from the performance control loop to the speed protection control loop to protect the running process of the turbofan engine.The simulation validates that the safety protection design can make the engine have good dynamic quality and safety performance.