The Key Technology Research Of Multi-pillar And Multi-wheel Series High Reliable Braking System

For multi-wheels and multi-strut aircraft,braking system is not only an important airborne equipment but also a relatively independent subsystem.In order to ensure the large aircrafts take-off and landing on the various and complicated runways,such as the crosswind runway,water runway,ice runway and the snow road potholes,the braking efficiency,safety and reliability requirements for its braking control system will become higher and more complicated,which ensure to absorb large aircraft landing energy and stop the aircraft.As the design and manufacture of large cargo aircraft in China is at an early age,the relevant standards and regulations are not very complete.From the development of foreign large aircrafts,high reliability,safety,airworthiness,testability,long life and easy maintenance are the inevitable requirements for the development of large aircrafts.The research on its key technologies,such as adaptive control law,reliability designs is of great practical and far-reaching historical significance.On account of the high reliability of the braking system required by large multi-wheels and multi-strut aircraft,this thesis gives a further study on the key technologies,for instance,the design method of braking system for large aircrafts,adaptive control law,method inhibiting the brake vibration,reliability analysis and verification techniques.The main contributes of this thesis are as follows:(1)A design method for brake control system based on the safety and reliability is put forward.Using top-down design method,functions of multi-wheel and multi-strut aircraft,such as normal brake and parking/emergency brake function are identified and analyzed,as well as the key indicators.Under the full consideration of the safety requirements of failure condition,take “uncommanded brake” as an example,the safety design methods and specific process are illustrated.Finally,the system architecture which satisfies the safety and reliability requirements of safety is formed.(2)In view of the low braking efficiency and poor recognition ability to runway of the traditional control method,this thesis firstly proposes the control strategy based on slip ratio and wheel deceleration ratio,and then design speed interpolation filter and Kalman filter to estimate coefficient force;establish the dynamic model of anti-skid braking system to simulate two kinds of runway with two kinds of control strategies.Finally,verify the control strategy by the inertia bench test for the braking system.The results show that the design method can identify runway accurately and quickly,with dynamic and static state performance,strong anti-interference ability,good robustness and high brake efficiency.(3)The researches on the vibration problem of multi-wheel and multi-strut aircraft braking under unsymmetrical loads and investigates the mechanism of brake vibration is conducted in this thesis.First,study the mechanism of braking vibration from the aspects of friction characteristics of the material for braking,brake pressure,brake housing structure and assembly gap.then establish the brake vibration model and carry out the brake vibration simulation analysis.Finally,based on the brake vibration source,the design method inhibiting the brake vibration is proposed.For the problem of the aircraft brake hydraulic system vibration,based on fluid structure interaction analysis for the pressure control system,the vibration mechanism is simulated,and the natural frequency of the aircraft brake hydraulic system is picked up.By comparing the result of the experimentation with that of the simulation,the method inhibiting the vibration of braking system for the multi-wheel and multi-strut aircraft is obtained,which is of great significance to improve the reliability of brake system.(4)Based on the wear failure of brake system and its products subject to Weibull distribution,the reliability,safety analysis method and the comprehensive verification technology for wheel brake system of large multi-wheels and multi-pillar aircraft are studied theoretically and engineeringly.The method using Weibull distribution to analyze reliability,safety is proposed for the first time and then verify the correctness of the Weibull distribution as the reliability and safety analysis method and its the mathematical model for brake system by experiments.Finally,a comprehensive verification method is obtained,and the test data indicate that the test method can better excite the fault,which is in accordance to the engineering practice and lay a foundation for the safe braking of aircraft.