T-S Fuzzy Model And Robust H-infinity Control For Aerospace Vehicle Reentry Through Atmosphere

Aerospace vehicle (ASV), which is a new reusable aircraft, at present, many countries in the world are speeding up their efforts in the research on it. The United States and European countries have their own aerospace projects and have achieved significant research progress, while, the research on hypersonic vehicles in our country is at in the initial stage. ASV shows serious nonlinear and coupling characteristic. Moreover, ASV subjects to the unkown disturbancea and uncertainties, so the design of fly control system of ASV is an attractive subject in the modem control area. Around this problem, this thesis has done an in-depth study in the following two aspects:building the fuzzy model of ASV in re-entry stages, robust H∞control based on T-S fuzzy model.First, according to recent research results both domestic and abroad, it reviewed on the research status and methods of the flight control system, T-S fuzzy system and attitude control of reentry flight. And through the introduction of foreign re-entry phase of the ASV research status of the attitude control system to find the gap of that.Second, according to study on literature published abroad, we built up a mathematical model of ASV and analyzed the response in open loop with zero input. It has been proved that the model can reflect the complicated nonlinear, strong coupling, fast time-varying and uncertain characteristics of ASV. Then some relevant knowledge is surveyed about fuzzy control, T-S fuzzy systems and universal approximation of T-S fuzzy systems, which are basic knowledge for T-S fuzzy model. We study on the mathematical model of ASV and then establish affine nonlinear model of ASV. The key variables and the key points have been chosen based on the open loop response of ASV with zero input. We use Taylor theorem to change the nonlinear system into a linear system. Based on T-S fuzzy approximation theory, we determine the appropriate membership functions, fuzzy rules and the fuzzy subsystems of the fuzzy rules. The model of the attitude motion for re-entry phase of ASV has been established. The simulation results for T-S fuzzy model of ASV can provide the basis for controller design and analysis. Finally, according to T-S fuzzy model of ASV which has been established, using the theory of the single Lyapunov function to design a state feedback robust H∞controller based on T-S fuzzy model. And using Schur complement lemma and theorem to prove the method can make the system stable. The simulation results for the ASV prove the fuzzy controller which we design is feasibility and effective.