| Aircraft braking system is an important airborne device to ensure aircraft braking safety and ground taxiing performance.Due to the influence of large kinetic energy,serious coupling of transverse and longitudinal torque,crosswind interference and complex runway environment in the process of high-speed takeoff and landing,it is very difficult to design aircraft anti-skid braking and deviation correction control.Model predictive control has good robustness for Multiple Input Multiple Output systems with constraints,and provides an effective solution to the braking control problem of aircraft under asymmetric conditions.Therefore,this thesis will deeply study the aircraft anti-skid braking and deviation correction control technology based on model prediction,so as to provide theoretical support for the design of actual aircraft braking system.The main contributions of this thesis are as follows:(1)Aiming at the problem that the existing aircraft anti-skid braking models ignore the coupling of transverse and longitudinal moments and can not fully describe the system dynamics,the composition,structure and working principle of the braking system are studied in detail.By analyzing the coupling mechanism of transverse and longitudinal torque in the process of aircraft braking,and considering the influence of left and right main wheel pairs on braking performance respectively,a ground taxiing dynamic model describing the system dynamics is established,which realizes the effective description of the transverse and longitudinal state of the system in the aircraft taxiing stage.(2)Considering the problem that the aircraft is vulnerable to be disturbed by crosswind,which leads to aircraft taxiing and yaw,a sliding mode disturbance observer based on finite time stability is designed to effectively estimate the crosswind disturbance,and a compensation mechanism is introduced to effectively suppress the crosswind disturbance to ensure the performance of deviation correction control.At the same time,Considering the problem that the aircraft can not identify the runway switching in time,resulting in the low efficiency of anti-skid braking,a threshold range analysis method based on front wheel load and combination coefficient is proposed.This method can provide the slip rate information to the controller in time under different runway switching conditions,so as to improve the efficiency of anti-skid braking.(3)Based on the established ground taxiing dynamic model,combined with the disturbance observer and runway identification method,a nonlinear model predictive controller is designed to complete the tasks of taxiing deviation correction and attitude correction while ensuring the efficiency of aircraft anti-skid braking.Taking a certain type of aircraft as an example,the simulation experiments are carried out under the conditions of crosswind interference,different runway environment,runway switching and asymmetric landing.The simulation results show that the control strategy proposed in this thesis can effectively improve the anti-skid efficiency and deviation correction performance of the braking system.There are 33 figures,11 tables,and 90 citations in this thesis. |
