Research Of The Nonlinear Vibration Character Of Vehicle Suspension System

With the rapid development of the railway transportation and the continuousimprovement of people’s living standard, people have put forward higher requirements on thetrain’s running speed and comfort. The vibration caused by the increasing speed has been paidmore and more attention. The performance of vehicle suspension directly affects the ridingcomfort and safety. Based on these points, it seems essential to do some research on theeffects of vehicle suspension system on vibration. This thesis takes the1/4vehicle bodysimple model as research subject, the vibration characteristics of vehicle in the presence ofnonlinear suspension system is studied. The works are listed as follows:In the first chapter, the overview nonlinear vibrations research and current situation ofthe suspension system are summarized, and the work is illustrated at the end of the chapter aswell.In the second chapter, the structure and classification of the suspension system aredescribed briefly, and the nonlinear character and control strategy of the suspension systemare analyzed as well.In the third chapter, the amplitude-frequency response function is deprived by homotopyanalysis method based on the model of one degree of freedom, and the influence theexcitation amplitude and nonlinear factors have on the vehicle resonance curve is analyzed. Itis proved that it is valid to use the homotopy analysis method to solve the one degree offreedom forced motion equations by comparing with the numerical simulation method. Also,the track irregularity excitation threshold in the chaos is deduced by forecasting the region inthe chaos using the Melnikov method. At last, the influence the nonlinear factors of thesuspension system have on the chaos region is analyzed.In the fourth chapter, the nonlinear functions are solved by homotopy analysis methodbased on the suspension model of1/4body, and the numerical solution and analytical solutionare contrasted by Matlab programming. Also, the influences the nonlinear factors and thetrack excitation amplitude of the suspension and the load have on the vibration characteristicsof the suspension systems are studied. What’s more, it is deuced that the vehicle system inthis thesis is stable, to some extent, the system will not be in chaos when the nonlinearparameters change by studying the stability of the vehicle system using the Routh-Hurwitscriterion and the lyapunov theory.In the fifth chapter, the time domain simulation on the power spectrum of US andGerman track are made in Matlab/Simulink. A two degree of freedom vehicle system Simlinkmodel is set up, and the simulation analysis on the vehicle system is made. Then, the linearrelative controllable and the semi-active suspension system based on magnetor-heological damper control are put forward. And two programs are contrasted by the control effect in arandom track spectrum. Moreover, the control effect in the step track spectrum is analyzed inorder to study the influence of the sudden large amplitude excitation. The results show thatthe dynamic performance of suspension system based on linear relative controllable is betterthan that of passive suspension, and the semi-active suspension system based onmagnetorheological damper is better than that of linear relative control.