Research On Comprehensive Performance Of Aircraft Brake Control System

Aircraft braking control system plays an important role in the take-off,landing,taxiing and turning of aircraft.The function,performance and architecture design of the system are related to the landing safety and economy of the aircraft.Its advanced technology also affects the development of aircraft and market development.Therefore,the aircraft braking control system is not only an important part of the landing gear,but also an essential important system for the safe operation of the aircraft.In recent years,the development of aircraft technology has put forward higher requirements for the development of aircraft braking control system.The original design methods and experimental aided design methods are not enough to meet the requirements of low cost,high reliability,high safety and high-level of research and development.The performance optimization of the existing products also needs to be further strengthened.Whether in the engineering application of braking system integration methodology or in the improvement of braking performance,there is still a certain gap between China and foreign countries.Therefore,this paper will use model-based system engineering(Model-based System Engineering,referred to as MBSE)methodology to complete the aircraft braking control system key requirements capture and validation,system architecture design.Through the analysis and optimization of the key factors affecting the performance,the performance enhancement model is distilled,which prepares for the follow-up product design and engineering application,and lays a good foundation for the improvement of the aircraft braking control system simulation level and professional ability at the same time.On the basis of analyzing the key requirements and designing architecture of the braking control system of a certain type of aircraft,the nonlinear factors,safety factors and boundary constraints outside the braking control system are considered as a whole in this paper.The main research contents are as follows:(1)The integrated development method of "Top-Down Design" of aircraft braking control system based on MBSE is proposed.In order to ensure the correctness of the captured key requirements,the behavior simulation modeling based on requirements is carried out by using the “Harmony SE” method,And the forward design and development process from the requirements to the architecture is described,which avoids the traditional design problems such as "pay more attention on implementation rather than requirement","design thearchitecture by captain's call"(without consultation or consideration)and "capture requirements relying on experience",and which reduces the development cost and improves the development efficiency.(2)The pressure-torque gain characteristics,friction characteristics,and process characteristics of aircraft braking materials are deeply studied,and the pressure-torque characteristics of aircraft braking materials are abstracted by analyzing the test results of many similar materials under different conditions.The pressure-torque characteristic model of the aircraft braking material is optimized,which avoids the distortion of simulation results caused by material characteristic error,and improves the validity and precision of simulation analysis.It lays a good foundation for further improving and optimizing the performance of aircraft braking control system.(3)Considering the complex nonlinear relationship between tire and runway characteristics,based on analysis of the influence factors of tire runway model with the Pacejka magic formula,a runway identification method based on the characteristic value of runway state is proposed.The eigenvalue interval of the typical runway is defined by the root mean square value of the eigenvalue threshold,and the runway state is identified based on the eigenvalue interval of the runway.and the maximum of the combination coefficient and the optimal slip rate are estimated in real time.It is proved that the recognition results are accurate and the recognition effect is good,which provides a guarantee for the improvement of brake efficiency.(4)Considering the low braking efficiency of the traditional quasi-regulating control method of PD + PBM,the calculation method of aircraft deceleration rate is optimized by using BP neural network and Lyapunov function control theory of asymmetric obstacle.An adaptive anti-skid control law of braking control system based on slip rate constraint is designed,which realizes the full regulation control of the braking control system and improves the braking efficiency(the braking efficiency of the wet runway is 80% under the full regulation control and the braking efficiency of the wet runway under quasi-adjustable control is 50% in AC25-7C).At the same time,the comprehensive performances of the whole aircraft braking control system under the various working conditions are analyzed and verified by means ofsimulation analysis and test bench test,which provides a guarantee for the improvement of the design level and further optimization of the performances of the whole aircraft braking control system.It saves the cost,shortens the cycle and improves the design efficiency for the development of the brake control system.