Non-linear And Fuzzy Control Method For Flight Control System

The Microwave Landing System(MLS) has higher performance and more advantages than the Instrument Landing System(ILS), which will be adopted as the international standard landing system to replace ILS in this year. Therefore, it is of great importance to study the Microwave Landing System.As the complexity of flight tasks increases, the linearized equation based on the small disturbance theory is no longer adequate for the design of control systems, and the necessity of exploring a nonlinear approach seems increasingly obvious. On the other hand, fuzzy control method is easily adapted to parameter changes in a nonlinear system. Therefore, combining fuzzy control with nonlinear control method can make the latter effective.In this thesis, Microwave Landing System is introduced and studied firstly. Secondly, the method of feedback linearization is adopted to design the automatic landing system. The original nonlinear system is linearized to one one-order system and one two-order system. Then design methods for linear systems can be adopted to design each system separately. Thirdly, a new fuzzy control method is introduced to design the Aircraft Microwave Landing System, which is based on analytically optimal correction function without quantization. The method can eliminate the conventional fuzzy control system's steady-state errors and flutters. And, the method of forward feed control is used to reduce the tracing errors during glide slope phase. Different control laws are designed to fit the two phases of flare control and glide slope control separately. Finally, the perturbation of 10 parameters and the air disturbances including horizontal wind, vertical wind and gust are considered in the landing process.The simulation results show that the designed landing system possesses not only satisfactory performances but also strong robustness.