Research On Warning And Control Of Aircraft In Low-altitude Windshear

Low-altitude windshear is a kind of weather phenomenon which threatens flight safety seriously,and a vast majority flight accidents are caused by windshear occurred during landing phase of aircraft.Most of the accidents are caused by pilots' wrong operation induced directly or indirectly by low-altitude windshear. Aimed at the problem, this thesis carries out deep research on warning and control of aircraft in low-altitude windshear.Firstly, we build a high-reality winshear model and flight dynamics model that takes into account effect of wind gradient in landing phase. By trimming and linearization, the linear models near trimming points are obtained. Based on linear models and nonlinear models respectively, the system's nature characteristics are analysed.Secondly, the classical method is used to design controller of aircraft automatic landing. Digital simulation results based on nonlinear model of aircraft show that the designed control laws can meet the requirements of performance and the designed control system has certain capacity of robustness towards windshear turbulence. Due to the obvious nonlinear characteristic of aircraft in windshear, the nonlinear dynamic inversion(NDI) method is employed for designing the controller of aircraft automatic landing. The proportional-integral loop is also adopted for compensating the system inversion error that arise from the disturbance of windshear and the perturbation of aircraft aerodynamic parameters caused by change of airspeed, which enhances the robustness and suppresses the influence of external disturbance and overcomes the NDI's shortcoming of requring accurate of model. In addition, the simulation results indicate that the method has good dynamics and good robustness, which effectively resists a greater strength of windshear interference compared with PID control.Thirdly, this thesis has considered the influential factors that the current warning algorithms does not considered, such as ground height, mass and control performance of aircraft. The Mont-Caro simulation experiment is taken into flight simulation test, which transform the uncertainty factors in windshear to probability of successful alarm and unnecessary alarm, and the final warning threshold values is computed based on two probabilities above. Compared with warning curve of Honeywell without consideration of altitude, mass and control performance, the warning curve of this thesis is more reasonable.Finally, this thesis builts a visual simulation model based on Flight Gear, and the virtualinstrument of simulation system based on Tilcon. The virtual simulation of control and warning of aircraft in windshear is achieved.