Study On Dynamic Characteristics And Application Of Composite Nonlinear Vibration Isolation System With Inerter

Rail transit provides convenience for people’s travel and cargo collection and distribution transportation,but with the increase of train running speed and operating mileage,the vibration problem of rail vehicles becomes more and more prominent.The vibration of train body caused by train running will affect the stability of vehicle running and ride comfort.With the concept of inertial vessel proposed,the new mechanical vibration isolation system of "inertial vessel-spring-damping" came into being,broke the shackles of the classical vibration isolation system of "spring-damping",and opened up a new direction for the improvement of the performance of vehicle vibration reduction system.At present,the research on vibration reduction measures of vehicle system mainly focuses on high-frequency vibration,while the research on low-frequency vibration isolation has not yet reached good vibration reduction expectations.In this paper,the composite vibration isolation structure formed by combining inertial vessel and quasi-zero-stiffness structure is applied to the second-series suspension system.By studying the system dynamics characteristics of vehicles,It provides some theoretical and scientific basis for the design and application of the low-frequency vibration isolation system of rail vehicles.The specific research content and results are as follows:1.The mathematical models of the nonlinear vibration isolation structure with inertial vessel and the composite nonlinear vibration isolation structure with inertial vessel are established,and the vibration dynamics of the above two models are analyzed.The first order harmonic balance method is used for numerical simulation to obtain the approximate solution of the system,and the fourth order Runge-Kutta algorithm is used for numerical comparison to verify the accuracy of the approximate solution obtained by the first order harmonic balance method.By comparing and analyzing the vibration isolation performance of the two types of models,the model with better vibration isolation performance is selected.On this basis,the force transfer equation of the composite nonlinear vibration isolation structure with inertial vessel is derived.Based on this,the vibration isolation performance of the system is described and the influence of different parameters on the vibration isolation performance of the system is clarified.The results show that under the same parameters,the response amplitude of the main structure decreases and the resonance frequency is closer to the low frequency region.At the same time,the response amplitude at the node decreases more significantly,which can effectively protect the inertial vessel as a vibration isolation element.The combined vibration isolation model not only expands the bandwidth of low-frequency vibration isolation,but also reduces the force transfer rate,and the vibration reduction effect is effectively improved.2.Based on Poincare mapping analysis,the nonlinear dynamic characteristics of the nonlinear vibration isolation structure with inertial vessel under harmonic excitation and the effects of different system parameters on the attractor were studied,and the effects of periodic motion,bifurcation and motion state transition in the low frequency region on the vibration reduction of the system model were further analyzed.3.The nonlinear dynamic characteristics of the composite nonlinear vibration isolation system with inertial vessel under the influence of multi-source excitation are studied.The approximate solution of the system is solved by the first-order harmonic balance method,and the influence level of multi-source excitation on the amplitude-frequency characteristics of the vibration isolation system is determined.The state equation of the system is determined and the bifurcation diagram of the system is obtained by using the fourth-order Runge-Kutta method and the nonlinear dynamic characteristics are analyzed.The results show that constant excitation affects the shaking of the head twice,resulting in 5 solution intervals.The combined bifurcation occurs in the main resonance frequency domain of the system,and the motion state transition process of the system is obviously different from that of the system under single frequency excitation.Constant excitation will destroy the original equilibrium position of the system,and the original fork bifurcation in the main resonance domain of the system will disappear,which means that the system does not have quasi-symmetric characteristics at this time.4.On the basis of the above research,the vertical vibration model of 1/4 vehicle system with compound nonlinear vibration isolation structure containing inertial vessel was established,and the influence of different inertial coefficient on the vertical response of train was analyzed.Compared with the traditional vertical vibration model of the traditional vehicle system,the two system responses were compared and analyzed,and the response values were reduced to different degrees.At the same time,Sperling stability index was used to evaluate the vibration isolation effect,and the results showed that the running stability and vibration isolation effect of the composite nonlinear vibration isolation structure system with inertial vessel were significantly improved,indicating that the vibration reduction effect of the scenario application would be relatively good.The above research shows that the composite vibration isolation structure system formed by the combination of inertial vessel and quasi-zero stiffness structure has a good vibration reduction effect for low frequency vibration isolation compared with the classical vibration reduction system,and it is expected to be vigorously promoted and applied in the design and scene application of rail transit vehicle vibration reduction.