Study On The Vehicle-Track Coupled Dynamics Of HTS High Speed Maglev With The Excitation Of Magnetic Guideway Irregularity

High temperature superconducting(HTS)pinning maglev,which was first demonstrated in China,has excellent high-speed potential and environmental protection advantages.However,at present,this technology is still in the verification stage of medium and low speed experiments.To ensure this maglev vehicle run safely and stably at high speed,there are still several scientific issues required to be solved.One of the most important aspects is the vehicletrack coupled vibration at high speed.Hence,this thesis studied the coupled vibration between HTS maglev vehicle and permanent magnet guideway.The research contents are expressed as follows:Firstly,the levitation/guidance forces of HTS pinning maglev are obtained by combining experimental measurement and finite element simulation.Nonlinear hysteresis models are introduced to describe the levitation force and guidance force;the vibration process of the maglev system is dynamically identified based on the least square method by which the parameters in the model are obtained.On this basis,the levitation/guidance force model of Dewar utilized in engineering is deduced,which can provide the magnet-track relationship for the vehicle-track coupled dynamics.This magnet-track relationship consists of a nonlinear stiffness term and a linear damping term.The vibration simulation based on this magnet-track relationship is in good agreement with the experimental data.Secondly,aiming at the geometric irregularity and magnetic field inhomogeneity of permanent magnet guideway(PMG),two sets of testing equipment are designed,and one of them is selected to measure a ring test guideway.The results show that the magnetic field inhomogeneity is mainly caused by the joint between PMGs,which can be simulated by geometric sinusoidal pit.The magnetic field inhomogeneity is represented as a geometric form,and the irregularity spectrum of PMG is obtained after analyzing the acquired data.The establishment of this irregularity spectrum can provide input to vehicle-track coupled dynamics analysis.Thirdly,the force analysis of the maglev vehicle composed of six suspension frames and one car body is carried out in detail.A vehicle dynamics model with 35 degrees of freedom is established based on Newton’s second law.The vehicle dynamics model simulation is achieved in MATLAB,which has the good agreement with the numerical results of commercial software UM.Based on the force analysis on the PMG,the guideway dynamics model is established based on the Lagrange’s equation.The magnet-track relationship established in this thesis is utilized to couple the vehicle model and the track model.Fourthly,according to the weak damping characteristic of HTS pinning maglev system,a vibration reduction scheme without mechanical contact is designed.An electromagnetic shunt damper(EMSD)is designed in this thesis utilizing the magnetic field provided by PMG,and the relevant optimization method is proposed.Based on a two-degree-of-freedom vertical vibration model,the suggested values for the secondary suspension parameters of the maglev vehicle are obtained.The simulation results with the excitation of PMG irregularity show that the high-frequency excitation caused by the magnetic field inhomogeneity will cause highfrequency vibration of the levitation frames.And a secondary suspension system can isolate the vibration of the car body,so that the vehicle is nearly not affected by the high frequency excitation of the magnetic field.Finally,based on the vehicle-track coupled dynamics simulations,the effects of suspension parameters and under-track support on the vehicle-track coupled system are analyzed meticulously.The results show that the vehicle vibration is mainly caused by the PMG irregularity,and the PMG vibration has little influence on it.The PMG vibration is mainly caused by the weight suddenly loaded by the maglev vehicle and has weak relationship with the PMG irregularity.Combined with the stationarity analysis,several optimized determinations on the secondary suspension parameters of maglev vehicle are given.Further dynamic curve simulations and vehicle-line-bridge coupled vibration simulations show that the HTS pinning maglev system has good dynamic performance under the proposed parameters.The dynamic model established in this thesis can provide a simulation tool for more detailed vehicle-track dynamics analysis,and the electromagnetic shunt damper introduced in this thesis could also supply a feasible idea for the damping design of HTS maglev system.The parameter analysis carried out in this thesis can provide a reference for the future design of maglev system.