Research On Coupling Vibration Of Mid-Low Speed Maglev Vehicle On Light Switch Steel Beam

The mid-low speed maglev is supported by electromagnetic suspension(EMS),which requires the suspension control to maintain the rated suspension gap through active control.If the coupling vibration of mid-low speed maglev vehicle on light switch steel beam(LSSB)can not be effectively suppressed,the vehicles can not be kept in normal suspension.Such coupling vibration is caused by various factors,including vehicle structure,levitation system,line condition and etc.The switch is the weak link of the mid-low speed maglev line.The performance of mid-low speed maglev vehicle negotiating LSSB is one of the main factors which decide the safety and ride comfort of such vehicles.Hence,it is of high importance to conduct research on the coupling vibration of mid-low speed maglev vehicles on LSSB.The thesis offered a survey of existing maglev technologies and vehicle-coupled-guideway vibration analysis methods.Analyses were made to explore the working principle and structure characteristics of the EMS mid-low speed maglev vehicle and the switch line equipment(LSSB).A 3D finite element model(FEM)was developed for certain active switch for mid-low speed maglev vehicles.Such steel beam allows variable sections and has vertical support across mid-span.Analyses of natural vibration properties of the active beam were made for various constraint conditions.The substructure analyses on the degree of freedom(DOF)reduction were made for the active beam with ANSYS.Analysis results were utilized to develop a rigidflexible coupling vehicle-switch model of in SIMPACK considering the air-spring mounting in the middle and on the two ends of each suspension frame.Based on such models,analyses were made to explore influences of vehicle speeds,air-spring mounting positions,the mass and the stiffness of active beam on the coupling vibration of mid-low speed maglev vehicle on LSSB.Conclusions could be made as following:The span between two adjacent active beam was short,and the first order vertical natural frequency of main line LSSB was higher.For elastic constraint condition,the calculated first order vertical bending frequency was close to the lowest vertical natural frequency of the applied active beam with vertical support across mid-span,which validated the rationality of the developed 3D shell element FEM for active beam.Vehicle speed had remarkable influences on the vehicle-LSSB coupling vibration.For speeds lower than 30 km/h,such coupling vibration would be enhanced under lower speed conditions.Maglev vehicles would show better negotiating performance for higher speed conditions.For switch negotiating speed in the 60 km/h~ 80 km/h crossing range,the center frequency of the excitation that suspension force applies on active beam was close to the main frequency of the active beam,which made the maximum vibration acceleration of the active beam greater than that under other vehicle speeds.The vertical deformation of an active beam was mainly affected by external load and the structure parameters of such active beam.There was no remarkable difference of the vertical deformation of the active beam between the maglev vehicle with mid-set air-spring and that with end-set air-spring.For both air-spring mounting conditions,the maximum vertical and lateral acceleration of carbody was sensitive to low switch negotiating speed and showed rare differences under high speed conditions.For all the ten considered speed conditions,the maximum carbody accelerations under both air-spring mounting conditions were all with in the acceptable range defined in corresponding standards.When a maglev vehicle was running on a light active beam,such beam was easier to be affected by external excitations.The mass of an active beam had significant influences on vehicle-LSSB coupling vibration.The first order main frequency of such beam would increase with mass reduction.The stiffness change of active beam also had significant influences on the vehicle-LSSB coupling vibration.A reduction of beam stiffness would cause reduction of the first order main frequency,increase of maximum lateral and vertical deformation and increase of maximum vertical carbody acceleration.