Study On Nonlinear Dynamic Characteristics Of A4DOF Vehicle Suspension System Under Road Surface-speed Coupling Excitation

The vehicle suspension system is a necessary unit to ensure travelling normal andenhance vehicle’s performance. Extensive use has been made of the componentsbecause of improving vehicle’s performance to some extent. The quite complexdynamic characteristics may appear in nonlinear vehicle suspension when the vehiclemoves over bumpy and rough roads, such as chaotic vibration. Analysing the dynamiccharacteristics of vehicle suspension with the combined road surface-speed excitationhas important theoretic significance and higher practical application value.The road surface-speed coupling excitation model is presented in the paper. Themethod of numerical emulation, such as phase portrait, Poincaré map, PSP map andfrequency spectrum, based on MATLAB environment the differential equation of a4DOF nonlinear vehicle suspension system is conducted to analyse the static dynamiccharacteristics and the trending dynamic characteristics before and after exerting activecontrol. What’s more, the vehicle ride comfort influenced by the complex dynamiccharacteristics is studied finally. The major contents of the thesis include the followingthree parts:①The road surface-speed coupling excitation model is presented. The systemstate equations are established after analyzing the form of the coupling excitation andthe nonlinear factors of the vehicle suspension.②The method of numerical emulation based on MATLAB environment isconducted to analyse the static dynamic characteristics at different speeds and thetrending dynamic characteristics in a speed range before and after exerting activecontrol. Analyse the effect of quasi-periodic motion and chaotic motion on the systemproperty by the comparison of dynamic characteristics before and after exerting activecontrol.③Vibration strength based on vertical vibration acceleration and PSP valuebased on vertical vibration velocity can be used to study the significant influence ofquasi-periodic motion and chaotic motion on vehicle ride comfort.The results indicate that chaotic vibration often affects other vibrational state andaffects vehicle ride comfort through affecting other vibrational state.