Automatic landing control using H[infinity] control and stable inversion
The design of an automatic landing system (ALS) is a challenging task. It is both a robust and a tracking control problem. In this thesis, a method combining H[Infinity] robust control and stable inversion is employed to develop controllers for an automatic landing system. We adopt the linearized longitudinal model of a Boeing 747 commercial airplane to verify this method. The control actuators, wind gust, and wind shear models are also established to simulate the landing process. H[Infinity] control is a robust control method. It can optimize the system performance and provide robust stability against uncertainties in the plant. The stable inversion is a precision tracking approach. We combine these two methods together to satisfy both robust and exact tracking requirements for the automatic landing system. Based on the stable inversion technique, the desired altitude and airspeed trajectories are also designed. The numerical simulation results show that the automatic landing system can meet FAA (Federal Aviation Administration) requirements for Category III precision approach landing. As expected, the integrated system can achieve accurate tracking, in the presence of measurement noise, wind gust, and wind shear with low intensity. Compared with existing approaches in automatic landing systems, the method used in this thesis can achieve higher precision. Finally, this method is particularly well suited for automatic landing systems using Global Positioning System.