LSM control of Maglev vehicle ride quality

The ride quality of a high speed repulsion type magnetically levitated vehicle using linear synchronous motor (LSM) propulsion has been studied. Vehicle motion is dependent upon the active LSM forces, the passive magnetic lift and drag forces, the aerodynamic drag force, and the technique employed for control. Derivations of the passive lift and drag forces and of the active heave and propulsion control forces are presented. For a balanced three phase LSM, it is shown that harmonic force pulsations disappear, except for the sixth harmonic and its multiples. A control technique which stabilizes the surge motion and provides needed damping in heave to guarantee acceptable ride quality has been simulated. Transient responses, for a vehicle traveling at 120 m/s show stable well damped motion. At this velocity, sixth harmonic effects are completely negligible. Stochastic results show that the heave motion power spectral density response to a moderately rough guideway, i.e., A = 1.34 × 10^-5m, more than satisfies the UMTA ride quality specification.     

Numerical Evaluation of Levitation Force Oscillation of HTS Bulk Exposed to AC Magnetic Field over NdFeB Guideway

The levitation force of the YBCO bulk over an NdFeB guideway used in the high-temperature superconducting (HTS) maglev vehicle system is oscillated by the application of the AC external magnetic field. In our previous work, we interpreted that the oscillation is due to the shielding current fluctuation caused by fluctuant external magnetic field. In this paper, based on the Bean model, an analytical model is adopted to evaluate the levitation force. Comparing with the experimental results, the calculated results show good matching. The model can reveal the oscillation characteristics of the levitation force of HTS bulk which is being exposed to AC external magnetic field. Therefore, the levitation force oscillation of the HTS bulk in the maglev vehicle system can be evaluated by this numerical method.     

Levitation Force Relaxation of HTS YBCO Bulk under Load

The loading capacity of the high temperature superconducting (HTS) maglev vehicle is closely relative to the maglev characteristics of the HTS bulk under the load. The investigation of the characteristics is necessary for the application of the HTS maglev vehicle. In our previous work, it was found that the levitation force relaxation increased with the increase of the reloading. In this paper, in terms of a HTS maglev system composed of the permanent magnetic guideway (PMG) and a HTS YBCO bulk, the levitation force relaxation under different loads is investigated by the numerical calculation and the experiment. It is found that the normalized relaxation rate of the levitation force increased with the increase of the load. The influence of the load on the current density distribution is also discussed in this paper. This work might be helpful for the research of the loading capacity of the HTS maglev vehicle.      

Levitation Performance of Bulk High Temperature Superconductor Above the Permanent Magnet Guideway at Different Temperatures

The levitation performance of a high temperature superconducting (HTS) Maglev system was investigated at different temperatures for HTS Maglev vehicle application. Using a cryogenic measurement system, we studied the effects of the HTS’s temperatures and the HTS’s field-cooling heights (FCHs) on the levitation force and its force density by applying a two-pole Halbach array’s permanent magnet guideway (PMG) at different temperatures. Results show that the levitation force is not only dependent on the temperature but also dependent on the original FCH. The effect of the temperature on the levitation force is considerably minute in low FCH. However, it was confirmed that the levitation force of HTS is larger at a lower temperature than at a higher temperature in high FCHs. Moreover, by applying the temperature of 60 K, the levitation force density of the system can be increased by 65% and 57.3% compared to the force density at 77 K in 35 mm and 40 mm FCHs. Hence, more magnetic energy at a low temperature area and high FCH can be utilized. The advancement of Maglev system’s performance will directly promote the development of HTS Maglev application and is helpful for the further HTS Maglev vehicle.     

Superconductor Losses and Damping Effects Under Zero Field Cooling and Field Cooling Conditions in a HTSC-Magnet Levitation System

The levitation and guidance forces of an HTS-Maglev vehicle are studied for different zero field cooling (ZFC) and field cooling (FC) conditions, with both forces showing hysteresis behavior in the FC condition. The levitation force has very different magnitudes depending on the cooling conditions employed in the Maglev vehicle. We also report and analyze a damping phenomenon in the levitation and guidance forces and associate the occurrence of damping with power losses located in the YBCO material when the Maglev vehicle operates in the FC condition. These results are very important for further HTS-Maglev vehicle system designs since power losses can disrupt YBCO superconductivity.     

Influence of YBCO Bulk’s Movement Speed and Operation Time on Levitation Force at Different Temperatures

In order to enhance levitation performance of the high temperature superconducting (HTS) magnetic levitation (Maglev) vehicle and have more stable and safer operation, levitation forces of YBCO bulk with different movement speeds and operation time at different temperatures are studied. The levitation force is measured using a cryogenic measurement system which has advanced instrumentation. Experimental results show that the levitation force is not only dependent on the temperature but also on the YBCO bulk’s movement speed and operation time. It is found that the effect of YBCO bulk’s movement speed and operation time on the levitation force is larger at higher temperatures, while such effect is smaller at lower temperatures.     

Levitation Force Relaxation of HTS Bulk above NdFeB Guideways at Different Approaching Speeds

The zero-field cooling levitation force relaxation of the YBCO bulk above two types of NdFeB guideways, which were used in the high-temperature superconducting maglev vehicle system, was studied experimentally when the bulk moved towards the guideways at different speeds. In this experiment, a sample with the diameter of 50 mm and thickness of 15 mm was used; the time range in the relaxation measurements was from 0 s to 200 s. As a result, a nearly linear logarithmic decay of the levitation forces with time was observed. It was found that the influence of the approaching speeds on the levitation force relaxation is different, and that the levitation force decay is closely related to the guideway structures. Based on the monopole peak PMG, the approaching speeds will influence more the levitation force decay than the multipole Halbach. So the maglev vehicle above mutipole Halbach structure PMG will work more stably than that above the monopole peak PMG.      

Effect of AC Magnetic Field on the Levitation Force of YBCO Bulk above NdFeB Guideway

In the present High Temperature Superconducting (HTS) maglev vehicle system, the nonuniformity of the magnetic field along the movement direction above the NdFeB guideway is inevitable due to the assembly error and inhomogeneous of the material property of the NdFeB magnet. In order to investigate the influence of the nonuniformity on the levitation performance of the HTS bulk, an electromagnet supplied by AC current is used to simulate the nonuniformity of the external magnetic field. The levitation force of the HTS bulk is measured when applying AC currents to the electromagnet coils. Experimental results indicate that the levitation force changes abruptly and then oscillates after applying AC external magnetic field, and the levitation force is attenuated by the AC magnetic field after withdrawing the AC field. Moreover, the oscillation amplitude and the attenuation rate of the levitation force increase with the amplitude of the AC external magnetic field.     

Superconducting bulk magnet for maglev vehicle: Stable levitation performance above permanent magnet guideway

High-temperature superconducting (HTS) maglev vehicle is well known as one of the most potential applications of bulk high-temperature superconductors (HTSCs) in transported levitation system. Many efforts have promoted the practice of the HTS maglev vehicle in people's life by enhancing the load capability and stability. Besides improving the material performance of bulk HTSC and optimizing permanent magnet guideway (PMG), magnetization method of bulk HTSC is also very effective for more stable levitation. Up to now, applied onboard bulk HTSCs are directly magnetized by field cooling above the PMG for the present HTS maglev test vehicles or prototypes in China, Germany, Russia, Brazil, and Japan. By the direct-field-cooling-magnetization (DFCM) over PMG, maglev performances of the bulk HTSCs are mainly depended on the PMG's magnetic field. However, introducing HTS bulk magnet into the HTS maglev system breaks this dependence, which is magnetized by other non-PMG magnetic field. The feasibility of this HTS bulk magnet for maglev vehicle is investigated in the paper. The HTS bulk magnet is field-cooling magnetized by a Field Control Electromagnets Workbench (FCEW), which produces a constant magnetic field up to 1 T. The levitation and guidance forces of the HTS bulk magnet over PMG with different trapped flux at 15 mm working height (WH) were measured and compared with that by DFCM in the same applied PMG magnetic field at optimal field-cooling height (FCH) 30 mm, WH 15 mm. It is found that HTS bulk magnet can also realize a stable levitation above PMG. The trapped flux of HTS bulk magnet is easily controllable by the charging current of FCEW, which implies the maglev performances of HTS bulk magnet above PMG will be adjustable according to the practical requirement. The more trapped flux HTS bulk magnet will lead to bigger guidance force and smaller repulsion levitation force above PMG. In the case of saturated trapped flux for experimental HTS bulk magnet, it is not effective to improve its maglev performances by increasing of charging magnetic field, when the guidance force at WH 15 mm is 5.7 times larger than that by DFCM of FCH 30 mm. So introducing HTS bulk magnet into the present maglev system is feasible and more controllable to realize stable levitation above applied PMG, which is an important alternative for the present HTS maglev vehicle.     

Influence of the Air Gap between Adjacent Permanent Magnets on the Performance of NdFeB Guideway for HTS Maglev System

For the permanent magnet guideway (PMG) of the high temperature superconducting (HTS) magnetic levitation (Maglev) vehicle system, there should be many air gaps between two adjacent permanent magnets by connecting, which may fluctuate magnetic field in the propulsion direction of the vehicle. A three-dimensional (3D) model of a PMG is built up using FLUX 3D software. The magnetic field density of an NdFeB PMG is measured and simulated by 3D and 2D models. Comparison among their results indicate that the simulation results of the 3D model agree better with the measuring results than that of the 2D model, and thus the 3D model is more suitable to describe the PMG. By the model, the influence of the air gap on the uneven of the magnetic field density in the propulsion direction is studied. It is found that the magnetic field 15 mm above the PMG is roughly even in the propulsion direction, although the magnetic field at 2 mm is not even. Since the working height 15 mm is a sensitivity parameter for the onboard high temperature superconductor (HTSC), the levitation force at working height 15 mm above PMG is measured, which indicates that the influence of the air gap on the levitation force is very small so as to be ignored in the quasi-static state.     

Oscillation Characteristics of Levitation Force of YBCO Bulk Exposed to AC Magnetic Field above NdFeB Guideway

In the present High Temperature Superconducting (HTS) maglev vehicle system, the nonuniformity of the magnetic field along the movement direction above the NdFeB guideway is inevitable due to the assembly error and inhomogeneity of the material property of the NdFeB magnet. In order to investigate the influence of the nonuniformity on the levitation performance of the HTS bulk, the experiment involved an electromagnet, which is supplying AC current to simulate the nonuniformity of the external magnetic field. The levitation force of the HTS bulk is measured when applying AC current on the electromagnet coils. The results indicate that the levitation force abruptly changes and oscillates after applying AC external magnetic field. The effect of the amplitude of the AC magnetic field on the levitation force is studied; the result shows that the oscillation amplitude of the levitation force increases with the amplitude of the AC external magnetic field and is independent of the Field Cooling Height (FCH) of the bulk.     

变速磁流变半主动悬架车辆与随机路面系统的模糊振动控制

建立半主动悬架车辆和随机路面系统模型,在采用磁流变减振器的基础上,应用模糊逻辑控制理论,进行车辆半主动悬架模糊控制器的设计,获得在模糊控制理论下可调阻尼力随时间变化的关系,应用simulink编制车路模型的仿真程序,研究在模糊控制算法下的匀变速行驶车辆路面系统平顺性问题。计算结果表明,与被动悬架的车辆相比,模糊控制的磁流变半主动悬架车辆可以改善行驶平顺性,同时还可减少车对路面的作用力,这对于车路系统是有利的,对于深入分析路面结构动力响应也具有重要的参考价值。     

Significant Correlations Between Levitation-Suspension Forces and Critical Current Densities in Bulk YBCO/Ag Composite Superconductors Fabricated by Infiltration and Growth Processing Technique

We report on significant correlations between the levitation-suspension forces and critical current densities in bulk YBCO/Ag composite superconductors fabricated by infiltration and growth processing (IGP) technique. Based on our studies, we have found that there is a strong correlation between various parameters obtained from levitation and suspension force curves and the magnetic J _cs calculated from M-H loops using the standard Bean’s model-type approaches. Significantly, the levitation force gap and the critical current density of the bulk sample are in direct correlation. We also find that it is possible to qualitatively predict the J _cs of samples from the levitation and suspension force curves by using this cost-effective measurement technique as a preliminary tool. These correlations provide a novel approach to rapid selection and characterization of bulk superconducting samples for their employment in practical applications.     

Influence of AC External Magnetic Field on the Levitation Force Relaxation of HTS Bulk Above NdFeB Guideway

In the present High-Temperature Superconducting (HTS) maglev vehicle system, the air gaps between the adjacent permanent magnets make the magnetic fields above the NdFeB guideway non-uniform. So one is required to study the characteristics of levitation force of the HTS bulk influenced by non-uniform fields. In this paper, we have studied the characteristics of the levitation force relaxation by an experiment in which the AC external magnetic field generated by an electromagnet is used to simulate the time-varying external magnetic field caused by the inhomogeneity of the NdFeB guideway. From the experiment results, it is found that the levitation force is attenuated with the application of the AC external magnetic field, and the decay is increased with the amplitude of the AC magnetic field, but the decay is almost independent of the frequency of the AC magnetic field.     

基于车桥耦合振动的车辆舒适性分析

研究车桥耦合振动引起的车辆舒适性问题对合理设计桥梁结构,从而减小车桥耦合振动响应和提高司乘人员的乘坐质量具有重要意义。分别利用有限元法和达郎伯原理建立了大跨度公路斜拉桥三维模型和9个自由度的车辆空间模型。通过位移和力的协调条件将车桥两个子系统耦合起来,求解车桥系统的振动微分方程。基于计算机软件ANSYS中的APDL语言编写了求解振动微分方程迭代计算的命令流,以ISO2631-1―1997标准建立了评价车辆舒适性的方法,并据此分析了主跨为550m的福建长门大桥在多车辆通过时考虑不同车速和车重时的车辆动力响应和车辆舒适性。计算结果表明,随着车速的增加,车辆的动力响应增加,舒适性变差;而随着车重的增加,车辆的动力响应减小,舒适性变好。     

车辆半主动悬架阻尼多模式切换控制研究

为提高车辆行驶平顺性,提出了一种基于阻尼多模式切换减振器的车辆半主动悬架及其控制方法。相较于传统阻尼可调减振器,该新型减振器通过控制两个高速开关电磁阀的通断状态即可实现四种不同的阻尼工作模式,从而使得车辆半主动悬架的阻尼控制更加高效和节能。分析了阻尼多模式切换减振器的基本原理,建立了减振器阻尼特性数学模型。结合车辆悬架系统的阻尼比范围,确定了减振器关键部件参数,并通过仿真获取了四种阻尼工作模式下的减振器复原阻尼系数和压缩阻尼系数。在此基础上,进一步建立了车辆半主动悬架数学模型,采用模糊控制逻辑设计了悬架阻尼多模式切换控制策略。仿真结果表明,相较于传统被动悬架和基于天棚控制的半主动悬架,基于阻尼多模式切换减振器的车辆半主动悬架可以进一步改善车辆行驶平顺性。     

Decay Characteristics of Levitation Force of YBCO Bulk Exposed to AC Magnetic Field above NdFeB Guideway

The superconducting maglev vehicle is one of the most promising applications of HTS bulks. In such a system, the nonuniformity of the magnetic field along the movement direction above the NdFeB guideway is inevitable due to the assembly error and inhomogeneity of the material property of the NdFeB magnet. So it is required to study the characteristics of levitation force of the bulks affected by the non-uniform applied magnetic fields along the moving direction. In this paper, we will study the characteristics of the levitation force relaxation between the HTS bulk and the NdFeB guideway by an experiment in which AC external magnetic field generated by an electromagnet is used to simulate the time-varying external magnetic field caused by the inhomogeneity of the guideway. From the experimental results, it has found that the levitation force is decreasing with the application of the AC external magnetic field, and the decay increasing with the amplitude of the applied magnetic field and is almost independent of the frequency.     

Flux Concentrator Optimization of PMG for High-Temperature Superconducting Maglev Vehicle System

The permanent magnetic guideway (PMG) composed of permanent magnet (PM) and steel is developed under flux concentration principle, which is the crucial component of high-temperature superconducting (HTS) maglev vehicle system. Optimum PMG design is an effective way to increase levitation force and associated stiffness for improving the load capability of HTS maglev vehicle. In order to realize higher vertical field component B _z in upper surface, three PMG demonstrators with three different forms of flux concentrator are fabricated with same volume of magnet. The levitation performances of onboard HTS bulks array over them are studied. The experimental results indicate that the PMG with a permanent magnet as the flux concentrator would produce biggest levitation force, levitation stiffness and trapped flux when interacting with HTS superconductor.     

Influence of the Vertical Inclination of Permanent Magnet Guideway on Levitation Characteristics of Hts Maglev System

In the application of high temperature superconducting (HTS) magnetic levitation (maglev) system under vertical inclination of permanent magnetic guideway (PMG), the component of the total weight of levitation body above the PMG will be changed. Therefore, the influence of the vertical inclination of PMG on levitation characteristics of HTS maglev system cannot be ignored, such as the levitation gap, the levitation force, guidance force and driving force of the linear motor. In order to investigate the influence of the vertical inclination angle on levitation characteristics of the HTS maglev system, a HTS maglev launch platform has been designed and fabricated for the investigation the influence of vertical inclination angle between the range of 0° and 18° on the levitation and guidance and driving force parameters of the HTS maglev launch platform. Experimental results show that the levitation gap was the main levitation characteristic for HTS maglev system under vertical inclination of PMG, which increased with increment of the vertical inclination angle. However, the levitation force, and the driving force of the linear motor decreased. The guidance force could not be influenced by the increment of levitation gap. The experimental results are helpful toward improving the running performance of the HTS Maglev launch system.     

汽车钢板弹簧动力学建模及应用研究

摘 要：针对传统的钢板弹簧动力学模型在整车平顺性仿真分析时,存在的仿真精度低、未考虑运动特性等问题。本文对钢板弹簧的动态特性对整车平顺性的影响进行研究。根据运动学理论,推导钢板弹簧的运动学特性计算公式,并分析钢板弹簧的运动特性对其弹性恢复力和阻尼力的影响;利用Hyper Mesh和ANSYS建立钢板弹簧的三维有限元模型,并将该模型导入基于Adams建立的整车动力学模型。对整车动力学模型进行平顺性仿真分析,结果表明：采用钢板弹簧模型与减震器模型的整车平顺性仿真结果与实车测试结果的最大误差分别为14.67%、30.48%;本文建立的钢板弹簧模型比单纯将钢板弹簧简化为具有静刚度和阻尼的减震器模型,其平顺性仿真结果与实际更为接近。