| Urban light rail transportation has been widely introduced due to its environmental protection,land utilization rate,low construction cost,and low investment.100% lowfloor vehicles have been widely introduced for their lower floor surfaces,and the independent rotating wheels used in low-floor vehicles that has the advantages of low noise;strong passing ability with small curve radius;convenient maintenance,etc.,but the centering of independently rotating wheels is poor;and it is easy to run against one side of the track;which causes aggravation of wheel and rail wear and increases the hidden danger of derailment.Under this background,based on the independent rotating wheel bogie structure,it is obviously necessary to study the unsprung mass of 100%low-floor vehicles and the dynamic performance of the entire vehicle.Traditional dynamic modeling generally regards vehicle components as rigid bodies.In the actual driving situation of the vehicle,the elastic model of the equipment of unsprung mass will appear when the wheel-rail excitation frequency and the natural frequency of the equipment resonate,based on this phenomenon,study the influence of the modal vibration of the unsprung mass on the vehicle dynamics when it is excited.Based on the influence of the flexibility characteristics of the unsprung axle-bridge and the wheels of the independently rotating wheel bogie on the dynamic performance of the vehicle,a certain type of 100% low-floor vehicle is the research object,and based on establishing its multi-rigid body model,it is further established the three-module rigid-flexible coupling dynamics model of the complete vehicle considering the flexibility of the axle-bridge and the three-module rigid-flexible coupling dynamics model of the complete vehicle considering the flexibility of the wheelset.The calculation results of the axle-bridge vibration response show that when the vertical natural vibration frequency of the axle-bridge structure is 15-25 Hz,its mode shape will be excited by the wheel-rail dynamic action,which will have a greater impact on the dynamic performance of the vehicle.The axle-bridge lateral vibration response of the rigid-flexible coupling model compare with the rigid-body model,the amplitude reduced by about 15%.Based on this research,the lightweight design of the axle bridge structure was carried out,and its geometric cross-section was optimized and its mass was reduced by about 15%.After the axle-bridge is optimized,the vehicle’s stability and curve passability have been improved.The analysis of the vibration response of the flexible wheel shows that the vibration of the flexible wheel is larger than that the rigid wheel at high frequency,the lateral vibration response is greater than that the rigid wheel at low frequency,and the vertical vibration response is smaller than that of the rigid wheel.Through calculation,it is found that considering the unsprung mass flexibility of the vehicle will aggravate the vehicle vibration,affect the wheel-rail relationship of the vehicle,and reduce the stability of the vehicle.At the same time,the rigid-flexible coupling model considering the flexibility of the axle bridge is more rigid than the rigid model.The lateral force of the wheel axle and the derailment coefficient is increased;the vertical force of the wheel/rail and the wheel load reduction rate are reduced.Considering the flexibility of the axle bridge affects the curve passing of the vehicle to a certain extent.The rigid-flexible coupling model considering the wheel flexibility is more rigid.The lateral force of the wheel axle,the vertical force of the wheel-rail,the wheel load reduction rate,and the derailment coefficient are reduced.Considering the wheel flexibility,the wheel-rail wear is reduced to a certain extent,and the curve of the vehicle is improved.Passability.To a certain extent,it provides engineering references for the axle bridge design of 100% low-floor vehicles. |
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