Research On Linear-Parameter-Varying Control For Transient State Of Aero-Engine

With the specification and standard of aero-engine developing rapidly,higher accuracy of models and stronger robustness of contollers under different operating conditions are greatly required.As for the transition stage,the aero-engine needs a certain thrust to change from one condition of work to another,like start,acceleration and deceleration while the thrust is controlled by the core-speed.The existing aero-engine gain scheduling controller designs which aiming at the whole flight envelope,mostly use the altitude and mach as the scheduling parameters,and transform LPV system to an affine parameter-dependence structure.Those methods may rise conservatism and inaccuracy when the status variable like core speed changes in large-scale.The robust GS theory based on aero-engine LPV system is studied in this thesis,and some new methods which have smaller conservatism are obtained and applied to the control of turbofan engine.The main research contents and contributions are presented as follows:Firstly,LPV system modeling of the robust GS is studied.The scheduling parameters selection and system matrix ecpression form of the system model is analized in this paper.As for the conservatism and accuracy of specific working conditions when the core speed had a greater influence on the change of the system features.The transformation methods of nonlinear system to LPV system about the core speed is put forward,and the LPV system of polynomial parameter-dependence and affine parameter-dependence is proposed.Secondly,in view of the LPV model of affine parameter-dependence about the core speed,we provide an alternative method of gain-scheduled control based on LMI theory to design core speed controller,which is applied to the linearized model of turbofan engine.Finally,in view of the LPV model of polynomial parameter-dependence about the core speed,using the controller design method aimed at polynomial model through the bounded real lemma combined with sum of squares theory,derive the SOS constraints to ensure the stability of the gain scheduling system,and applied on the core speed control when external parameters chaging in a certain scale.Aim at the large range of the flight envelope,using method based on Gap-Metric through generalized distance between the systems doing switching control.The simulation result testifies the new one is better.The control method,using the core speed as the scheduling parameter,are applied to the turbofan engine control system,and it is meaningful for the robust GS of the high-performance turbofan engine.