Research On Lose Nanding Gear Shimmy With Magnetorheological Principle

Aircraft shimmy often occurs during the aircraft taxiing process which leads to detrimental effects on the maneuverability and stability of the aircraft if it can't control appropriately.The damper which is designed on principle of magnetorheological has a wide adjustable range about damping force.It has obvious advantages in controlling shimmy.In the work of paper,the shimmy characteristics of nose landing gear are studied based on the mature single coil built-in magnetorheological dampers.Firstly,shimmy analysis model is established considering wheel oscillation,tire deformation and damper force characteristics.Based on the stability theory of differential equations,stability conditions of shimmy system are established,and the influence of system parameters on shimmy stability domain is analyzed,which lay the foundation for the simulation research of aircraft shimmy.Secondly,linear and nonlinear models are established which are based on the dynamic model of the magnetorheological damper by using the linear function and the Fourier series method.The damper performance test is used to determine the applicable conditions of the model.By analyzing the flow field and the performance requirements of magnetorheological fluids in damper hole,the mathematical model and the AMEsim hydraulic simulation model about damping force are constructed.The experimental data are used to correct and compare two models,and the causes of error are analyzed.The accurate calculation of damping force is completed.The results show that both models can meet the design requirements of damper,but the mathematical model has higher precision.Finally,the virtual prototype of aircraft shimmy is built by using ADAMS dynamic software platform,combining the damping force mathematical model of the damper and the structure model of the front landing gear.The influence law of key factors on shimmy system is analyzed by setting different working conditions,and the simulation results are verified by the mounting experiment of damper.The results show that shimmy stability is a dynamic process,and system needs different damping to reach the equilibrium state under different working conditions.When the force is insufficient or adequate,there is an unstable oscillation zone.If magnetorheological dampers want to achieve the best effect,the output damping force provided by MR dampers should match the force required by oscillating system.