Aerodynamic Features of High-Speed Maglev Trains with Different Marshaling Lengths Running on a Viaduct under Crosswinds

The safety and stability of high-speed maglev trains traveling on viaducts in crosswinds critically depend on their aerodynamic characteristics.Therefore,this paper uses an improved delayed detached eddy simulation(IDDES)method to investigate the aerodynamic features of high-speed maglev trains with different marshaling lengths under crosswinds.The effects of marshaling lengths(varying from 3-car to 8-car groups)on the train’s aerodynamic performance,surface pressure,and the flow field surrounding the train were investigated using the three-dimensional unsteady compressible Navier-Stokes(N-S)equations.The results showed that the marshaling lengths had minimal influence on the aerodynamic performance of the head and middle cars.Conversely,the marshaling lengths are negatively correlated with the time-average side force coefficient(CS)and time-average lift force coefficient(Cl)of the tail car.Compared to the tail car of the 3-car groups,the CS and Cl fell by 27.77%and 18.29%,respectively,for the tail car of the 8-car groups.It is essential to pay more attention to the operational safety of the head car,as it exhibits the highest time average CS.Additionally,the mean pressure difference between the two sides of the tail car body increased with the marshaling lengths,and the side force direction on the tail car was opposite to that of the head and middle cars.Furthermore,the turbulent kinetic energy of the wake structure on the windward side quickly decreased as marshaling lengths increased.

Study on Dynamic Characteristics of Superconducting Electrodynamic Maglev Train

This study considers a superconducting electrodynamic maglev train of MLX01 type.The characteristics of the electromagnetic spring coefficient of a single bogie under different magnetomotive force(MF) of the superconducting coil and standard air gap(Sag) were explored.In view of the small electromagnetic damping,a passive damping control strategy and an active damping control strategy were designed to increase the electromagnetic damping force between the superconducting coil and ground coil.Combined with the coupling numerical model of a single bogie,the vibration characteristics of the bogie in different directions with different damping control strategies were studied when the Sag and MF were fixed.The results can provide important theoretical support for stable operation control of maglev trains.

Disturbance rejection tube model predictive levitation control of maglev trains

Magnetic levitation control technology plays a significant role in maglev trains.Designing a controller for the levitation system is challenging due to the strong nonlinearity,open-loop instability,and the need for fast response and security.In this paper,we propose a Disturbance-Observe-based Tube Model Predictive Levitation Control(DO-TMPLC)scheme combined with a feedback linearization strategy for the levitation system.The proposed strategy incorporates state constraints and control input constraints,i.e.,the air gap,the vertical velocity,and the current applied to the coil.A feedback linearization strategy is used to cancel the nonlinearity of the tracking error system.Then,a disturbance observer is implemented to actively compensate for disturbances while a TMPLC controller is employed to alleviate the remaining disturbances.Furthermore,we analyze the recursive feasibility and input-to-state stability of the closed-loop system.The simulation results indicate the efficacy of the proposed control strategy.

Coupling vibration analysis of high-speed maglev train-viaduct systems with control loop failure

The risk of failure of the control loop can occur when a high-speed maglev train runs on viaduct.Meanwhile,the failure of the levitation magnets which balances the gravity of the maglev train could cause the train collision with track.To study the dynamic response of the train and the viaduct when the levitation magnet control loop failure occurs,a high-speed maglev train-viaduct coupling model,which includes a maglev controller fitted by measured force-gap data and considers the actual structure of train and viaduct,is established.Then the accuracy and effectiveness of the established approach are validated by comparing the computed dynamic responses and frequencies with the measurement results.After that,the dynamic responses of maglev train and viaduct are discussed under normal operation and control loop failures,and the most disadvantageous combination of control loop failures is obtained.The results show that when a single control loop fails,it only has a great influence on the failed electromagnet,and the maglev response of adjacent electromagnets has no obvious change and no collision occurs.But there is a risk of rail collisions when the dual control loop fails.

A study on aerodynamic noise characteristics of a high-speed maglev train with a speed of 600 km/h

Purpose–This study aims to explore the formation mechanism of aerodynamic noise of a high-speed maglev train and understand the characteristics of dipole and quadrupole sound sources of the maglev train at different speed levels.Design/methodology/approach–Based on large eddy simulation(LES)method and Kirchhoff–Ffowcs Williams and Hawkings(K-FWH)equations,the characteristics of dipole and quadrupole sound sources of maglev trains at different speed levels were simulated and analyzed by constructing reasonable penetrable integral surface.Findings–The spatial disturbance resulting from the separation of the boundary layer in the streamlined area of the tail car is the source of aerodynamic sound of the maglev train.The dipole sources of the train are mainly distributed around the radio terminals of the head and tail cars of the maglev train,the bottom of the arms of the streamlined parts of the head and tail cars and the nose tip area of the streamlined part of the tail car,and the quadrupole sources are mainly distributed in the wake area.When the train runs at three speed levels of 400,500 and 600 km$h1,respectively,the radiated energy of quadrupole source is 62.4%,63.3%and 71.7%,respectively,which exceeds that of dipole sources.Originality/value–This study can help understand the aerodynamic noise characteristics generated by the high-speed maglev train and provide a reference for the optimization design of its aerodynamic shape.

A nonlinear control method for the electromagnetic suspension system of the maglev train

To deal with the inherent nonlinearity and open-loop instability of the electromagnetic suspension（EMS） system,a new nonlinear control method is proposed.The simulation results show that,for a PID controller,the over-shoot of the system response to an airgap step disturbance is about 3 mm,and the transient time is 6 s;however,for the proposed nonlinear controller,there is no overshoot and transient time within 2 s.The proposed method has a faster response and stronger robustness.With a designed bi-DSP suspension controller,this nonlinear control method was implemented on the Shanghai Urban Maglev Test Line（SUMTL） to validate its effectiveness and feasibility.

Aerodynamic simulation of evacuated tube maglev trains with different streamlined designs

Based on the Navier-Stokes （N-S） equations of incompressible viscous fluids and the standard k-ε turbu- lence model with assumptions of steady state and two dimensional conditions, a simulation of the aerodynamic drag on a maglev train in an evacuated tube was made with ANSYS/FLOTRAN software under different vacuum pressures, blockage ratios, and shapes of train head and tail. The pressure flow fields of the evacuated tube maglev train under different vacuum pressures were analyzed, and then compared under the same blockage ratio condition. The results show that the environmental pressure of 1 000 Pa in the tube is the best to achieve the effect of aerodynamic drag reduction, and there are no obvious differences in the aerodynamic drag reduction among different streamline head shapes. Overall, the blunt-shape tail and the blockage ratio of 0.25 are more efficient for drag reduction of the train at the tube pressure of 1 000 Pa.

Communication simulation of on-board diagnosis network in high-speed Maglev trains

The on-board diagnosis network is the nervous system of high-speed Maglev trains, connecting all controller sensors, and corresponding devices to realize the information acquisition and control. In order to study the on-board diagnosis network＇s security and reliability, a simulation model for the on-board diagnosis network of high-speed Maglev trains with the optimal network engineering tool （OPNET） was built to analyze the network＇s performance, such as response error and bit error rate on the network load, throughput, and node-state response. The simulation model was verified with an actual on-board diagnosis network structure. The results show that the model results obtained are in good agreement with actual system performance and can be used to achieve actual communication network optimization and control algorithms.

The approach to calculate the aerodynamic drag of maglev train in the evacuated tube

In order to study the relationships between the aerodynamic drag of maglev and other factors in the evacuated tube, the formula of aerodynamic drag was deduced based on the basic equations of aerodynamics and then the calculated result was confirmed at a low speed on an experimental system developed by Superconductivity and New Energy R＆D Center of South Jiaotong University. With regard to this system a high temperature superconducting magnetic levitation vehicle was motivated by a linear induction motor （LIM） fixed on the permanent magnetic guideway. When the vehicle reached an expected speed, the LIM was stopped. Then the damped speed was recorded and used to calculate the experimental drag. The two results show the approximately same relationship between the aerodynamic drag on the maglev and the other factors such as the pressure in the tube, the velocity of the maglev and the blockage ratio. Thus, the pressure, the velocity, and the blockage ratio are viewed as the three important factors that contribute to the energy loss in the evacuated tube transportation.

Numerical Analysis of the Rotational Magnetic Springs for EDS Maglev Train

Different from the traditional railway trains,the combined levitation and guidance EDS maglev train is more likely to rotate after being disturbed.Therefore,the rotational electromagnetic stiffnesses are significant operating parameters for the train.In this paper,the different effects of each translational offset generated in the rotational motion on the corresponding rotational electromagnetic stiffnesses in the EDS maglev train are analyzed and calculated.Firstly,a three-dimensional model of the maglev train is established.Then,based on the space harmonic method and the equivalent circuit of the levitation and guidance circuits,the formulas of rolling,pitching and yawing stiffness are presented.Finally,by comparing with the three-dimensional finite element simulation results,the key translational displacements in the rotational motion which has a great impact on the stiffness are obtained.Hence,the three-dimensional analytical formula can be simplified and the computation can be reduced.In addition,the accuracy of the calculation results is verified by comparing with the experimental data of Yamanashi test line.

Multi-objective aerodynamic optimization design of high-speed maglev train nose

Purpose–The nose length is the key design parameter affecting the aerodynamic performance of high-speed maglev train,and the horizontal profile has a significant impact on the aerodynamic lift of the leading and trailing cars Hence,the study analyzes aerodynamic parameters with multi-objective optimization design.Design/methodology/approach–The nose of normal temperature and normal conduction high-speed maglev train is divided into streamlined part and equipment cabin according to its geometric characteristics.Then the modified vehicle modeling function(VMF)parameterization method and surface discretization method are adopted for the parametric design of the nose.For the 12 key design parameters extracted,combined with computational fluid dynamics(CFD),support vector machine(SVR)model and multi-objective particle swarm optimization(MPSO)algorithm,the multi-objective aerodynamic optimization design of highspeed maglev train nose and the sensitivity analysis of design parameters are carried out with aerodynamic drag coefficient of the whole vehicle and the aerodynamic lift coefficient of the trailing car as the optimization objectives and the aerodynamic lift coefficient of the leading car as the constraint.The engineering improvement and wind tunnel test verification of the optimized shape are done.Findings–Results show that the parametric design method can use less design parameters to describe the nose shape of high-speed maglev train.The prediction accuracy of the SVR model with the reduced amount of calculation and improved optimization efficiency meets the design requirements.Originality/value–Compared with the original shape,the aerodynamic drag coefficient of the whole vehicle is reduced by 19.2%,and the aerodynamic lift coefficients of the leading and trailing cars are reduced by 24.8 and 51.3%,respectively,after adopting the optimized shape modified according to engineering design requirements.

高速磁浮列车搭接结构悬浮系统仿真分析

为模拟高速磁浮列车悬浮系统运动过程并分析不同条件下的系统响应,本文围绕悬浮系统建模、控制器设计和仿真分析展开研究.首先,介绍以搭接结构为基本单元的高速磁浮列车悬浮系统的基本结构与工作原理,通过机理分析方法构建理想情况下的悬浮系统数学模型;然后,对悬浮系统模型进行合理简化,并针对简化模型设计标称控制器;最后,仿真验证了标称控制器的控制效果,并对比分析仿真和实验条件下永磁电磁混合悬浮系统的起浮降落过程.研究结果表明:仿真得到的悬浮间隙、悬浮电流等物理量的变化情况与实际系统的变化趋势吻合,稳态时误差小于5%.

磁浮列车悬浮力的公式优化及悬浮系统的建模与实验

EMS (Electro-magnetic suspension)型中低速磁浮列车的悬浮系统在建模过程中,通常利用泰勒公式将悬浮力在平衡点处线性化。线性化后的近似悬浮力公式与标称悬浮力公式之间存在一定的误差。本文将该误差作为一种不确定性进行研究,由此得到了新的悬浮力公式并创新性地构建了具有不确定性的悬浮系统模型。随后,利用所建立的模型设计了一个基于广义内模控制算法的悬浮控制器,并在悬浮系统的单转向架平台上进行了抗干扰能力测试和过台阶能力测试。实验结果表明在本文所提出的悬浮控制器作用下,系统具有良好的悬浮性能和鲁棒性。

空气弹簧组件对列车磁悬浮系统的影响

[目的]为研究作为组件之一的空气弹簧对列车磁悬浮系统的影响,解决磁浮列车磁悬浮系统因空气弹簧的影响而导致的悬浮性能变差的问题,开展了空气弹簧对磁悬浮系统性能影响的机理研究和仿真分析。[方法]首先建立不含空气弹簧的磁悬浮模型,并在此基础上设计控制算法,根据磁悬浮系统的性能指标,设计其最优控制参数;在控制算法和最优控制参数确定之后,再将空气弹簧的影响考虑到磁悬浮系统模型中,以研究空气弹簧的刚度对磁悬浮性能的影响。采用MATLAB软件对磁悬浮系统的性能进行了仿真,仿真过程中,在不改变控制参数时改变空气弹簧的刚度,以观测磁悬浮性能的变化情况;当磁悬浮性能变差时,通过优化控制参数,使得磁悬浮性能保持最优。[结果及结论]仿真结果表明:当空气弹簧的刚度在某一范围内时,刚度越大越不利于磁悬浮系统的稳定;在空气弹簧的刚度增大时,适当增加控制系统的刚度和阻尼会有利于磁悬浮系统的稳定。

超导电动磁浮列车电磁特性及悬浮稳定性控制

超导电动磁浮列车运行过程中电磁阻尼较小,借助列车直线同步电机牵引控制,设计悬浮稳定性控制系统,为列车的悬浮稳定提供一种技术手段。以MLX01型超导电动磁浮列车为研究对象,结合单个转向架与地面线圈组成结构的场-路-运动耦合数值模型,揭示了超导电动磁浮列车的悬浮特性。研究了超导电动磁浮列车超导磁场强度、悬浮位移、运行速度以及标准空气气隙之间的关系特性,分析了不同超导磁场强度和标准空气气隙下单个转向架悬浮方向电磁弹簧系数变化规律。采用矢量控制策略实现了超导磁浮列车直线同步电机直轴和交轴分量的解耦,建立了直轴电流与悬浮力之间的数值表达式,设计了悬浮稳定性控制结构,并采用状态反馈实现悬浮系统的极点配置。通过对比采用悬浮稳定性控制结构前后转向架平衡位移响应,证明了采用悬浮控制结构的有效性。研究结果表明,采用悬浮稳定性控制系统可有效抵抗外部干扰,维持列车的悬浮稳定,也可进一步提高列车的乘坐舒适性。

磁浮列车机械制动系统交叉耦合控制方法

机械制动系统在制动过程中产生一定的能量消耗,若控制策略不合理,容易导致制动能耗过大,影响磁浮列车的正常运行,为此,提出磁浮列车机械制动系统交叉耦合控制方法。根据磁浮列车机械制动系统结构框架,计算液压力伺服系统的传递系数和闸瓦与轨道之间的摩擦系数,以此获取磁浮列车机械制动系统传递函数。根据该传递系数,引入气隙、速度双重同步交叉耦合控制器,求取气隙同步误差和扰动量,获得交叉耦合控制结果。利用果蝇优化算法(fruit fly optimization algorithm,FOA)对该控制器的控制参数实施参数寻优,得到最优控制参数,进而实现磁浮列车机械制动系统交叉耦合稳定控制。实验结果表明,所提方法能够获取最优控制参数,并提高控制精度和效率。

真空管道磁悬浮系统构想

真空管道磁悬浮的悬浮和低空气阻力以最大化减少了列车前进的阻力,使得它具有平稳、舒适、超高效、超高速、超快捷的特点,从而决定了它必然是载人公共交通的发展方向之一。通过对真空管道磁悬浮系统和子系统磁浮列车、真空管道、真空设备系统(含密闭门、密闭窗、真空设备)、磁浮轨道系统、供电系统、自动控制系统、通信系统、售检票系统、综合维护系统的构想,及其相关子系统关键技术和运营场景的描述,提出了各子系统的主要构成和关键技术的解决思路,以及部分利用既有技术的思路。其运营场景的详细描述,对于相关子系统的研发提供了功能需求的支撑。

中低速磁浮列车多传感器融合测速方法

针对中低速磁浮列车测速问题,文章以凤凰中低速磁浮快线为研究对象进行分析,提出一种多传感器融合的测速方法。首先,分析涡流传感器的测速原理及其测速不准的主要原因;其次,针对中低速磁浮线路测速不准问题,从算法层面和运动学原理角度提出处理方法;最后,采用卡尔曼滤波算法对涡流传感器、雷达和加速度计的信息进行融合测速。试验结果表明,当列车速度大于1 m/s时,该方法的测速相对误差在±2%之内,满足磁浮列车的测速精度要求。

SIMULATION STUDY OF AERODYNAMIC FORCE FOR HIGH-SPEED MAGNETICALLY-LEVITATED TRAINS

Based on Reynolds average Navier-Storkes equations of viscous incompressible fluid and k-ε two equations turbulent model, the aerodynamic forces of high-speed magnetically-levitated （maglev） trains in transverse and longitudinal wind are investigated by finite volume method. Near 80 calculation cases for 2D transverse wind fields and 20 cases for 3D longitudinal wind fields are analyzed. The aerodynamic side force, yawing, drag, lift and pitching moment for different types of maglev trains and a wheel/rail train are compared under the different wind speeds. The types of maglev train models for 2D transverse wind analysis included electromagnetic suspension （EMS） type train, electrodynamic suspension （EDS） type train, EMS type train with shelter wind wall in one side or two sides of guideway and the walls, which are in different height or/and different distances from train body. The situation of maglev train running on viaduct is also analyzed. For 3D longitudinal wind field analysis, the model with different sizes of air clearances beneath maglev train is examined for the different speeds. Calculation result shows that： ① Different transverse effects are shown in different types of maglev trains. ② The shelter wind wall can fairly decrease the transverse effect on the maglev trains. ③ When the shelter wall height is 2 m, there is minimum side force on the train. When the shelter wall height is 2.5 m, there is minimum yawing moment on the train. ④ When the distance between inside surfaces of the walls and center of guideway is 4.0 m, there is minimum transverse influence on the train. ⑤ The size of air clearance beneath train body has a small influence on aerodynamic drag of the train, but has a fairly large effect on aerodynamic lift and pitching moment of the train. ⑥ The calculating lift and pitching moment for maglev train models are minus values.

600 km/h高速磁浮交通系统气动设计

中国轨道交通历经几代技术创新与发展,取得了令世界瞩目的成就。轮轨系统的黏着限制了轨道交通的进一步高速化,磁浮技术在轨道交通上的应用应运而生。“十三五”期间,中国开始研制600 km/h高速磁浮交通系统。高速磁浮列车运行速度为600 km/h,马赫数达到0.49,列车空气动力学性能急剧恶化,加之运行环境(车–轨间隙、两侧节流)的变化,呈现出与高速轮轨列车不同的气动特征,空气动力学问题成为高速磁浮列车设计研发的关键问题之一。本文探讨了600 km/h高速磁浮列车气动设计面临的技术挑战,提出了高速磁浮列车气动设计解决方案,介绍了我国600 km/h高速磁浮列车气动设计方案,展望了高速磁浮列车空气动力学未来研究方向。