Control Strategy Design For Scramjet Engine With Flight/Propulsion Coupling Properties

The scramjet-powered hypersonic air-breathing flight vehicle has a wide application background especially in space transportation and the military in the foreseeable future. And there are many key problems are urgent to be solved in hypersonic air-breathing propulsion technology. Nowadays, many military powers and organizations including the U.S., Russia, Europe, Australia, Japan, and so forth, have been engaged on this field with great human resources and financial support to conduct hypersonic air-breathing propulsion projects. And those programs in the U.S. and Russia are already under the flight test phase and will soon reach to a success. In order to reduce the gap and distance in the top defense technologies in the future between China and other great military powers, and take a place at air-breathing hypersonic propulsion technology, it is quite necessary for Chinese researchers to consider and solve some key technical problems related to the field at present.First, the model for the airframe-scramjet integrated hypersonic airbreathing flight vehicle with safety boundaries is developed. Based on the special request on the coupled flight dynamics analysis and control design for the modeling the hypersonic vehicle, the dissertation describes the overall diagram block for the hypersonic vehicle model HIT-HAV with a non-symmetrical configuration. By aerodynamics analyzing, CFD calculating, experimental data comparing, data fitting and other methods, the integrated hypersonic air-breathing flight vehicle and scramjet engine model HIT-HAV is built. The final finished model HIT-HAV can outputs any aerodynamic parameters, thrust and safety margins and is verified by comparison analysis.Next, the coupled dynamics between scramjet engine and aerodynamics is analyzed. Based on the hypersonic vehicle/ scramjet engine model HIT-HAV with safety boundaries, the impact of the integrated aerodynamics/propulsion on the flight dynamics is analyzed. The couplings between the flight vehicle and scramjet engine are revealed by model simulation. Due to the influence of the coupled dynamics on the model structure and the capacity lack in traditional control, the necessity to conduct an integrated flight/propulsion control for hypersonic air-breathing flight vehicle is discussed. Due to the multiple tasks and multiple operation modes in scramjet engine, the necessity to conduct a scramjet thrust tracking and safety protecting multiobjective switching control is discussed.Then, the research on the scramjet engine tracking/protecting switching control design problem is conducted. A tracking/protecting multiobjective switching control solution under Min/Max switching rule for flight control and engine control is presented and the basic principles are analyzed. Then the stabilization condition of the specific switching control problem is given and the stability of subsystems is proved. The function of the precondition and guarantee for effective switching, i.e., the integral saturation limiting, is analyzed. Consider the closed-loop system after switching under Min switching rule as a dynamic response with initial conditions and the output maximum percent overshoot are deducted, which are dependent on not only the system parameters and controller parameters, but also on the initial conditions at switching point. The global maximum value for the output maximum percent overshoot is deducted and solved in initial conditions space and is defined as a conservative dynamic performance for the closed-loop switched system. Then a general dynamic performance index oriented switching control design method is presented. The switching control method is verified by simulating both the simplified scramjet engine and the vehicle model HIT-HAV.Finally, the research work on the coordinated control for airframe-scramjet integraged hypersonic vehicle is carried out. Based on a consideration to reduce design difficulty and minimize expense, a hypersonic vehicle/engine coordinated control based on safety margin is presented. The basic consideration and idea of coordinated control is: under a precondition of not to change the original flight and engine control structure, a coordinated factor based on vehicle and/or engine safety margin is brought in to guide the flight controller and engine controller to fit new or different flight conditions. As the safety margin can characterize the'distance'or'degree'that the present operation state of the vehicle or engine is apart the unsafe state, a coordinated control between flight performance and flight safety can be realized by detecting the safety margin in time and thereby changing the coordinated factor. The simulation under the coordinated control method is conducted on the nonlinear hypersonic flight vehicle HIT-HAV and the results show a rationality and feasibility of this method.