Research On Active Disturbance Rejection Control System And Parameter Optimization Of Civil Turbofan Engine

The development of aeronautical technology and the growing frequency of using the aircraft put forward higher requirements for aircraft engine performance and flight stability.The whole working process of an aircraft engine is a very complex aerodynamic thermodynamic process.Because the aerothermodynamics process varies greatly under different environmental conditions and states,the mathematical model of aero engine system is always changing and has strong non-linear characteristics.For such a nonlinear time-varying system,without effective control,the aircraft engine will not be able to work.Therefore,aero-engine control system,as a mechanism to improve engine performance,to protect engine components and to maintain engine stability,has become increasingly important.Nowadays,PID still plays a dominant role in aero-engine control.Although PID control has high stability margin,it has little margin of good dynamic quality.Also because of passive disturbance rejection,PID consumes more control energy.Therefore,this topic will study the aero-engine control system based on auto-disturbance rejection and optimize its parameters,so that the system has strong disturbance rejection ability.Finally the goal of maintaining good engine performance with lower control energy will be achieved.The main contents and work of this paper are as follows:First,the mathematical model of turbofan engine was deeply studied.The steady-state models and dynamic nonlinear models of the turbofan engine were established by component modeling technology based on the theory of aerodynamic and thermodynamic.In order to facilitate the research and design of the control system,the nonlinear component-level model was linearized at the steady-state point by partial derivative method.Then,the order of the model was reduced by spectral decomposition,and also the model was normalized.Through the above methods,the ill-conditioned problem of solving equations due to different order of magnitude of parameters was solved.The experimental results showed that the parameters obtained by this method can make the system response have excellent characteristics,but the instantaneous value of the control signal was prone to surge and exceed the endurance limit of the actuatorSecond,the turbofan engine control system was designed by using active disturbance rejection control(ADRC)technology.The structure of ADRC system for turbofan engine was designed.In this paper,an steady-state ADRC was designed for the system at each steady-state point,and the conditions for the stability of the control system were given.Then the controllers of each steady-state point were scheduled to form the steady-state controller of the engine under the whole state.In addition,the parameters of ADRC were analyzed in detail.We tuned the controller parameters using the bandwidth-based tuning method and then conducted a simulation experiment.Third,the parameter optimization of ADRC was studied by using adaptive genetic algorithm.In order to prevent the surge of control signals,We put the stability,dynamic characteristics of the system response and the constraints of the control signal into the fitness function.In this paper,the optimized ADRC was compared with the commonly used PID controller in the field of aero engine control.The simulation results showed that the parameters of the active disturbance rejection controller optimized by the adaptive genetic algorithm designed in this paper can effectively eliminate the surge of control signals and protect the safety of the actuator.Moreover,the system response showed good dynamic and steady-state characteristics.Finally,the controllers at each steady-state point were synthesized,and an ADRC control system system was designed for a non-linear turbofan engine by gain tuning method,which realized the control of the nonlinear turbofan engine.Based on the rotational speed of the high-pressure rotor of the engine,the parameters of the ADRC at the designed steady-state points were interpolated in real time to obtain the parameters of the controller at the unsteady-state points.We assigned these parameters to the dynamic controller,and then in order to control the non-linear engine,the steady-state controller and the dynamic controller were combined by the gain scheduling method.When the engine was near the steady-state point,it would be controlled by the steady-state controller,and when it was at the unsteady-state point,it would be controlled by the dynamic controller.The variation of the turbofan engine model parameters was non-linear,and also the dynamic controller obtained by interpolation was non-linear.Finally,the simulation results showed that the turbofan engine control system designed in this paper can effectively control the nonlinear engine.On the premise of ensuring the stable operation of the turbofan engine,it could make the engine have good dynamic characteristics,steady-state characteristics and anti-interference ability.