Turbofan Engine H_∞ Output Feedback Control And Delay Compensation Strategy

As the"brain and nerve"of the engine,the aero engine control system is a key functional system to ensure the stable operation of the engine under the restrictive conditions of aerodynamic heat and mechanical design,as well as within the full envelope.In recent years,aeroengine distributed control system has become a research hotspot as a light-weight,easy-to-maintain,and highly reliable control system architecture.However,network communication under the distributed architecture introduces time delay that affects system performance.Therefore,the research of delay compensation strategy is of great significance.Relying on the“Research on Time Delay Stability Analysis and Compensation Methods under Distributed Architecture”project of a research institute,the research on the H_∞output feedback control and time delay compensation strategies of turbofan engines is carried out.The main contents are as follows:(1)Aiming at the stable control problem of turbofan engine with strong nonlinearity and large parameter perturbation,the design of dual-variable controller and direct thrust controller of the engine is realized based on the H_∞mixed sensitivity method.Aiming at the problem that the thrust of the engine cannot be directly measured,the indirect thrust control based on the sensor method and the direct thrust control based on the airborne adaptive model are studied.Based on the linear model established by the system identification,the H_∞output feedback controllers are designed respectively to realize the speed and pressure ratio tracking control and direct thrust control.(2)Aiming at the engine dual-variable control system with delay,a system stability judgment method is given.The composition of the delay in the turbofan engine control system and its influence on the system are analyzed,and a modeling method of the delay system is given.Based on the Lyapunov stability principle,the method of the stability analysis and the maximum allowable delay are given.The comparison of simulation and theoretical analysis results verifies the rationality of the method proposed in the paper.(3)Aiming at the problem of performance degradation of turbofan engine bivariate system based on H_∞control under delay,a delay compensation method based on Smith principle is given.For the forward channel delay and feedback channel delay in the closed loop,different compensation algorithms and full delay compensation algorithms are proposed.Aiming at the problem that the traditional Smith algorithm relies too much on the precise model of the controlled object,the Smith adaptive compensation algorithm and the dual-controller Smith control method are studied.The simulation results show that the control system designed by the improved method has good dynamic performance and robust stability.(4)The simulation based on Truetime platform and hardware-in-the-loop(HIL)test are carried out.Results show that the existence of delay reduces the stability of the system,Which also verifies the effectiveness of the designed control system with delay compensation strategy and the feasibility in engineering applications.