Simulation And Analysis Of Dynamic And Fault Characteristics Of Landing Gear Extension And Retraction System Based On Modelica

Aircraft landing gear extension and retraction system is a complex physical system involving hydraulic,control,mechanical and other fields.In the design and development,it is necessary to comprehensively consider the coupling relationship between various fields.The multi-domain unified modeling and simulation method is adopted to consider the coupling relationship between various domains and solve the problem of data exchange and system integration among the multi-domain models of the complex system.In this paper,the landing gear extension and retraction system is established based on the multi-domain unified modeling language Modelica,and the dynamic characteristics and fault characteristics of the landing gear extension and retraction system are analyzed,which has important engineering significance for the design of accelerating landing gear extension and retraction system and improving the safety performance of landing gear extension and retraction system.The main research contents of this paper are as follows:First of all,expounds the structure and working principle of landing gear extension and retraction system,according to the top-down approach was carried out on the landing gear extension and retraction system decomposition,break it down for hydraulic subsystem,control subsystem and machinery subsystems,each subsystem is again decomposed into components that can be expressed in mathematical models.The corresponding Modelica model is established according to the mathematical model or working principle of hydraulic components,control components and mechanical components.Based on the component model,in accordance with the bottom-up approach to system integration,the subsystem model and system model is established,and the subsystem model was simulated and verified,which laid the model foundation for the subsequent dynamic characteristics analysis and fault characteristics analysis of the landing gear extension and retraction system.Then,the working scene of landing gear extension and retraction system is analyzed,and the corresponding simulation requirements are proposed.Based on the established simulation model of landing gear extension and retraction system,the normal extension and retraction dynamic characteristics and emergency retraction dynamic characteristics of the landing gear extension and retraction system were simulated and analyzed to verify the correctness and rationality of the simulation model of landing gear extension and retraction system,and the influence of different flight speeds on the normal extension and retraction and emergency retraction was analyzed.The results show that the greater the flight speed,the greater the aerodynamic load of the landing gear,the longer the normal retraction time,and the shorter the normal extension and emergency extension time.Finally,some typical faults of landing gear extension and retraction system are analyzed,and these faults are injected into the simulation model of landing gear extension and retraction system for fault characteristic simulation analysis,study the effect of different faults on landing gear extension and retraction performance,as well as to the part of the fault simulation model of emergency put function verification.It provides the basis for fault prevention and fault diagnosis of landing gear extension and retraction system.The results show that the insufficient system pressure will increase the retracting and extension time of the landing gear;the blockage of the retracting orifice is mainly to increase the retracting time;the blockage of the extension orifice is mainly to increase the extension time;leakage of the retraction-extension actuator cylinder will reduce the retraction time and increase the extension time;landing gear cannot be lowered due to upper lock unlocking fault;landing gear does not retract properly due to lower lock unlocking fault.