Research On Kinematic Reliability Analysis And Simulation Of Landing Gear Retraction And Extension Mechanism Of Aircraft

Landing gear retraction and release mechanism plays a decisive role in aircraft landing.Only when the landing gear is put down in place can it play a good supporting role in landing.Only when the retraction and release mechanism is put up and down smoothly can the aircraft fly safely.In the reliability analysis of mechanism,the problem of clearance and flexibility has been paid more attention by scholars.It is difficult to avoid the aggravation of the gap due to the existence of the necessary original tolerance,installation and manufacturing error and wear in the working process.On the one hand,the elastic deformation and clearance of flexible components will seriously affect the motion accuracy of the mechanism,on the other hand,it also makes frequent contact and collision,which will affect the dynamic performance of the retraction mechanism.In this paper,the influence of the motion accuracy and dynamic characteristics of the mechanism considering the hinge clearance and the flexibility of the component is studied deeply,which lays a foundation for the motion,reliability and simulation analysis of the retractor mechanism with the hinge clearance and the flexibility of the component.The specific research contents of this paper are as follows:(1)The qualitative failure analysis of landing gear retraction and release mechanism is carried out through fault statistics.Firstly,based on the real image of a certain aircraft landing gear,the simplified three-dimensional model of the retractor mechanism is drawn in CATIA,and the working principle and the degree of freedom of the retractor mechanism are described to verify the motion uniqueness.Based on the statistics of landing gear faults collected in aviation safety network database,the main failure factors of landing gear retracting and releasing mechanism are determined by combining FTA and FMEA,which points out the direction for the next quantitative reliability analysis.(2)Based on the theory of effective rod length,the calculation model of motion reliability of retracting and releasing mechanism with clearance is established.Aiming at the practical application of landing gear retraction and release mechanism,two kinds of effective rod length calculation models of two hole type and pin type are established,and the functional relationship between the main support angle and rod length is established.According to the principle,the average value and standard deviation of hinge clearance are determined,so the simulation value of intermediate clearance rod of each kinematic pair can be obtained by sampling in MATLAB according to normal distribution,Then,the calculation model of effective rod length can be substituted into the function relation to analyze the reliability of the support angle difference of the retracting and releasing mechanism with clearance.(3)By using LMS virtual.Lab software and AMESim hydraulic software,a simulation model of landing gear retraction and release mechanism with hinge clearance flexible coupling effect is established.After calculating the relevant parameters of the hydraulic cylinder,the hydraulic simulation system is established in AMESim software by using PID displacement servo control,which provides hydraulic driving force and displacement adjustment for the retraction and release of the actuating cylinder.In the LMS virtual.lab dynamics software,the gap and flexibility are simulated in the model,and the automatic cycle operation of simulation and the extraction and storage of simulation results are realized by VBA macro program programming.(4)The dynamic characteristics and the reliability analysis based on the maximum driving force of the simulation model results of the landing gear retraction mechanism are carried out.Aiming at the analysis of the dynamic characteristics of the retracting and releasing mechanism under the condition of gap size,friction coefficient,gap number and gap flexible coupling,the nonlinear functional relationship between the random parameters and the maximum driving force of the actuator is established by using BP neural network,so as to complete the quantitative analysis of its reliability,so as to evaluate the reliability and sensitivity of the mechanism more accurately,It provides an effective basis for the regular maintenance of the mechanism and the regular replacement of key components.