Research On Vertical Coupled Vibration Of Medium-Low Speed Maglev Vehicle And Bridge Under The Condition Of Controlled Current Fluctuation

With the rapid economic growth,the urban rail transit has developed by leaps and bounds.The medium-low speed maglev transportation system has become an important part of urban rail transit by virtue of its strong climbing ability and low construction cost,which has broad development prospects.In engineering applications,the medium-low speed maglev transportation system has experienced strong vehicle-bridge coupling vibration.The vehicle-bridge coupling vibration will seriously affect the safety and comfort of vehicle driving,and will also cause large deformation and vibration of the bridge structure.It affects the safety and durability of the bridge structure,so it is necessary to carry out in-depth research on this.The levitation control current is an important variable of the levitation module in the maglev transportation system.The fluctuation characteristics of the controlled current will affect the vibration of the maglev vehicle-bridge coupling system.This paper studies the vertical coupling vibration of medium-low speed maglev vehicle bridges under controlled current fluctuations.The main research contents are as follows:(1)The levitation,steering and driving principles of the electromagnetic levitation system,as well as the levitation constant current and levitation controlled current characteristics are analyzed.The electromagnetic levitation model based on the controlled current was established according to the fluctuation characteristics of the controlled current.The calculation model of the levitation control current was derived by using the proportional integral-differential controller,and the stability range of the controlled current fluctuation parameters in the calculation model was derived by using the stability criterion.Finally,the expression of the electromagnetic levitation force based on the levitation control current was obtained.(2)A dynamic model of maglev vehicle and bridge coupling vibration system with medium-low speed is established under the condition of controlled current.The models include medium-low speed maglev vehicle model,and track beam model.According to the structural characteristics of medium-low speed maglev vehicle,the dynamic equation of maglev vehicle was derived by d’Alembert principle,and the fluctuation characteristics of levitation control current were considered in the equation.The hypothesis of track beam is put forward and the dynamic equation of track beam is derived by finite element method.Finally,the coupled vibration equation of medium-low speed maglev vehicle and bridge was established,and a numerical simulation program was compiled by FORTRAN language to calculate the coupled vibration equation,which was realized in the development software of Visual Studio.(3)The vertical dynamic response characteristics of the maglev vehicle and bridge coupling vibration system with different fluctuation parameters of the suspension control current are systematically studied.The results show that the overall dynamic response of the coupling system decreases first and then increases with the increase of integral parameters and differential parameters.Under the condition of controlled current,the dynamic response of the coupling system is in a safe value.When the influence of the fluctuation parameter combination of controlled current on the coupling system at different speeds is studied,it is found that the dynamic response of the coupling system increases with the increase of the speed under different parameter combinations.The parameter combination I(integral parameter K_i=30,differential parameter K_d=170)is higher than the parameter combination II(integral parameter K_i=40,differential parameter K_d=170)is more advantageous;When the influence of parameter combinations of controlled current on the coupling system under different spans is studied,it is found that the dynamic response of the coupling system under different parameter combinations increases with the increase of the span.Parameter combination I is more suitable for the coupling system with the large span,while parameter combination II is more suitable for the coupling system with the small span.