Robust Controller Design For Airplane And Research On Stability Margins

The study of robust flight control is important to both the efficiency of air transportation and the flight safety. In this thesis, H_∞ control theory is applied to airplane landing control under wind disturbances. Two H_∞ approaches are employed to design the robust controller, i.e., Algebraic Riccati Equation (ARE) approach and Linear Matrix Inequality (LMI) approach, and the stability margins of the system is studied in the last section. The main results of this thesis are as follows:1. Controller design by using ARE approach and computer simulations.2. Weighting matrices' selection of high order ARE. A parameter-selecting method is proposed to determine the weighting matrices of high order Riccati equation. By using this method the high order Riccati equation is solved efficiently and satisfying H_∞ state feedback controller with robust stability is developed.3. Controller design by using LMI approach and computer simulations. The similar parameter-selecting method is used to determine the parameter matrices of high order LMIs.4. Comparison of two approaches. The relationship of the ARE approach and LMI approach is discussed. Some simulation tests are given to compare these two approaches from several aspects. The results indicate that the two approaches are equivalent under the same assumptions.5. Analysis on stability margins. The stability margins of controllers designed in this thesis are examined to avoid poor margins of a H_∞ controller.6. Robust stability Analysis. Gain margins of a practical airplane with flight controller is analyzed. Robust stability of the system is examined so that model uncertainties could be contained.