Control Study For Over-under TBCC Engine With Safety Boundaries

Hypersonic propulsion technology has significant application value in the field of military attack,space transportation,space development,etc.It plays an irreplaceable role in the field of national defense and military.The combined propulsion system is the most promising first-stage propulsion of two-stage-to-orbit vehicle due to its advantages such as wide working envelope,huge applied value and self-starting on the ground,which has gained certain attention from many military powers such as the United States,Japan,Germany and Russia.Most of the countries mentioned have initiated explorations and researches on key technologies of the combined propulsion system,and some of them have carried out experiments.According to the current research development,there are still many technical difficulties in the field of combined propulsion technology to overcome.The control of combined propulsion system is the most important one.This thesis studied several questions about the key technologies related to the challenges of the safety boundaries exploration and the control of combined propulsion system.Firstly,Turbine-Based Combined Cycle(TBCC)engine model was established.Component-level modeling methods were used to establish a lumped parameter mathematical model of inlet,turbine engine,ramjet engine,etc.These component models were integrated into a mathematical model of TBCC.Safety characteristics were introduced into the model by defining the safety margins.The calculation model was built on Matlab/Simulink platform.The model can be used to simulate and calculate the turbojet mode,ramjet mode and the mode transition process.By analyzing the engine characteristics under different modes,it can provide reference for the subsequent research on the control of TBCC.Secondly,the safety characteristics of TBCC engine and the control regulations under situations of different engine safety characteristics are analyzed.The measurable physical quantities describing the safe boundaries were determined.The values of the safety boundaries of working Mach number were obtained.The influence of inlet flow condition and geometric factors on the safe boundaries were analyzed.Under the limitation of the safety boundaries,the feasible region of fuel have been analyzed when the engine geometric structure is fixed,and the influence of the geometric factors on the practicable of fuel in the two engines are analyzed.Thus the adjusting regulations for the fuel and geometric factors under the safety boundaries were obtained.Based on the above adjusting regulations,a set of control regulations for given thrust output is designed.The regulations can be used for open-loop control or subsequent closed-loop control.Thirdly,the study on the control of TBCC engine adjustment\protection multipattern switch was carried out.Based on adjustment\protection multi-working pattern,a switching strategy was designed to guarantee the performance and safety under the whole work envelope.The switching control system was designed as a two-layer structure consisting of the lower sub-loop controllers and the upper undisturbed switching controller.The signals determined by real-time parameters and super parameters were designed for each sub-loop,and the output signals of each sub-loop were combined to designing switching rules,which could selected two online loops among seven loops and solve the switching problem.Finally,the multivariable control of TBCC engine was discussed.An H-infinity multivariable robust control method based on loop shaping was adopted,and the two-in-two-out controllers for ramjet and turbojet were designed.The structures of multivariable controllers were presented and the performance and robustness of system were analyzed.After that,the effect of multivariable controllers was verified under fixed Mach number and real flight trajectory respectively.