A Loss-model-based Efficiency Optimization Control Method for Induction Traction System of High-speed Train under Emergency Self-propelled Mode

Increasing attention has been paid to the efficiency improvement of the induction traction system of high-speed trains due to the high demand for energy saving. In emergency self-propelled mode, however, the dc-link voltage and the traction power of the motor are significantly reduced, resulting in decreased traction efficiency due to the low load and low speed operations. Aiming to tackle this problem, a novel efficiency improved control method is introduced to the emergency mode of high-speed train traction system in this paper. In the proposed method, a total loss model of induction motor considering the behaviors of both iron and copper loss is established. An improved iterative algorithm with decreased computational burden is then introduced, resulting in a fast solving of the optimal flux reference for loss minimization at each control period. In addition, considering the parameter variation problem due to the low load and low speed operations, a parameter estimation method is integrated to improve the controller's robustness. The effectiveness of the proposed method on efficiency improvement at low voltage and low load conditions is demonstrated by simulated and experimental results.

Investigation of intense sheet electron beam transport using the macroscopic cold-fluid model and the single-particle orbit theory

The focusing and the stable transport of an intense elliptic sheet electron beam in a uniform magnetic field are investigated thoroughly by using the macroscopic cold-fluid model and the single-particle orbit theory.The results indicate that the envelopes and the tilted angles of the sheet electron beam obtained by the two theories are consistent.The single-particle orbit theory is more accurate due to its treatment of the space-charge fields in a rectangular drift tube.The macroscopic cold-fluid model describes the collective transport process in order to provide detailed information about the beam dynamics,such as beam shape,density,and velocity profile.The tilt of the elliptic sheet beam in a uniform magnetic field is carefully studied and demonstrated.The results presented in this paper provide two complete theories for systemically discussing the transport of the sheet beam and are useful for understanding and guiding the practical engineering design of electron optics systems in high power vacuum electronic devices.

四轮转向牵引车牵引飞机轨迹跟踪控制研究

为提高飞机在牵引过程中的轨迹跟踪精度与稳定性,以四轮转向飞机牵引系统为研究对象,建立了飞机牵引系统运动学模型,提出了基于模型预测控制(model predictive control,MPC)的牵引车四轮转向轨迹跟踪控制方法。以双移线工况作为参考轨迹,在MATLAB/Simulink中搭建飞机牵引系统运动控制仿真模型,结合牵引车车速以及4个车轮的转角分配关系,建立牵引车四轮转向轨迹跟踪控制器。将该控制器与传统比例积分微分控制(proportional integral differential,PID)进行对比分析,得出该控制器的优越性,并分别在1.5、3、4 m/s的速度下,将牵引车四轮转向与前轮转向轨迹跟踪控制器进行仿真对比分析。在1.5 m/s的速度下,通过改变飞机牵引系统的初始位姿对所设计的控制器进行仿真验证。结果表明:在3种不同的速度下,牵引车四轮转向轨迹跟踪控制下的飞机横向误差、航向角误差以及牵引车航向角误差均小于前轮转向轨迹跟踪控制。在存在初始偏差的情况下,四轮转向轨迹跟踪控制器能够使飞机及时完成对初始偏差的修正,减小轨迹跟踪误差,同时提高飞机牵引系统行驶过程中的稳定性。

城轨列车牵引能耗模型的关键参数拟合研究

在城市轨道交通节能方面,列车牵引能耗占有较大比重。为了在运能优化及节能之间找到平衡点,需对灵活编组列车牵引能耗进行分析,作为协调便捷性及经济性的参考依据。根据经典力学建立列车牵引能耗数学模型,为方便研究又建立了牵引能耗理想模型,通过分析杭州地铁某线路线历史运营数据,对其关键参数进行拟合研究,对拟合好的关键参数的关系式曲线进行鲁棒性验证。基于杭州地铁某线路的实际数据对建立的牵引能耗理想模型进行仿真验证,拟合结果为牵引能耗理想模型提供数据支持,并为牵引能耗理想模型的去理想化奠定基础,可在实际项目中推广应用,具有较好的理论价值和实际意义。

Experimental research on grouser traction of deep-sea mining machine

The traction characteristics of the grouser, cutting the simulative soil of deepsea sediment, with different tooth widths, tooth heights, and ground pressures are studied with traction characteristic test apparatus. A traction-displacement model is obtained by combining the analysis of the cutting mechanism. The results show that the tractiondisplacement curves of grousers with different tooth widths, tooth heights, and ground pressures have the same changing trend, which matches the Wong traction model. Their sensitivity coefficient and shear modulus are slightly fluctuated. Therefore, the average values can be used as the traction model parameters. The maximum traction of the grouser with a two-side edge and a 10 mm tooth width increment changing with the tooth height and ground pressure can be determined according to the grousers with different tooth widths. By combining the traction model parameters, the traction-displacement curve of the grouser with a certain group values of tooth width, tooth height, and ground pressure can be predicted. Therefore, the slip of the mining machine can be prevented to improve the mining efficiency.

Traction rheological properties of simulative soil for deep-sea sediment

The traction capacity of the mining machine is greatly in?uenced by the traction rheological properties of the deep-sea sediments. The best simulative soil was prepared for substituting the deep-sea sediment based on the deep-sea sediment collected from the Paci?c C-C mining area. Traction rheological properties of the simulative soil were studied by a home-made test apparatus. In order to accurately describe the traction rheological properties and determine traction rheological parameters, the Newtonian dashpot in Maxwell body of Burgers model was replaced by a self-similarity spring-dashpot fractance and a new rheological constitutive model was deduced by fractional derivative theory. The results show the simulative soil has obvious non-attenuate rheological properties. The transient creep and stable creep rate increase with the traction, but they decrease with ground pressure. The fractional derivative Burgers model are better in describing non-attenuate rheological properties of the simulative soil than the classical Burgers model. For the new traction rheological constitutive equation of the simulative soil, the traction rheological parameters can be obtained by ?tting the tested traction creep data with the traction creep constitutive equation. The ground contact length of track and walking velocity of the mining machine predicted by the traction rheological constitutive equation can be used to take full advantages of the maximum traction provided by the soil and safely improve mining effciency.

Possible implications of animal models for the assessment of visceral pain

Acute pain,provoked generally after the activation of peripheral nociceptors,is an adaptive sensory function that alerts the individual to avoid noxious stimuli.However,uncontrolled acute pain has a maladaptive role in sensory activity leading to development of a chronic pain state which persists even after the damage is resolved,or in some cases,in the absence of an initial local acute injury.Huge numbers of people suffer from visceral pain at least once during their life span,leading to substantial health care costs.Although studies reporting on the mechanism of visceral pain are accumulating,it is still not precisely understood.Therefore,this review aims to elucidate the mechanism of visceral pain through an evaluation of different animal models and their application to develop novel therapeutic approaches for treating visceral pain.To assess the nociceptive responses in viscera,several visceral pain models such as inflammatory,traction,stress and genetic models utilizing different methods of measurement have been devised.Among them,the inflammatory and traction models are widely used for studying the visceral pain mechanism of different disease conditions and post-operative surgery in humans and animals.A hapten,2,4,6-trinitrobenzene sulfonic acid(TNBS),has been extensively used as an inflammatory agent to induce visceral pain.The traction model seems to cause a strong pain stimulation and autonomic reaction and could thus be the most appropriate model for studying the underlying visceral pain mechanism and for probing the therapeutic efficacies of various anesthetic and analgesics for the treatment of visceral pain and hyperalgesia.

PERFORMANCE SIMULATION OF VEHICLES EQUIPPED WITH TRACTION DRIVE CVTS

A computer model for the performance simulation of vehicles equipped with traction drive continuously variable transmission （CVT） is presented. The model integrates the traction drive CVT subsystem into an existing overall vehicle system. The characteristics of engine output torque are formulated using neural networks, and torque converter is modeled using lookup tables. Component inputs and outputs are coupled in the dynamic equations and interfaces in the powertrain system. The model simulation can provide evaluation of vehicle performance in drivability, fuel economy and emission levels for various drive ranges prior to the prototyping of the vehicle. As a design tool, the model assists engineers in understanding the effect ofpowertrain components on vehicle performance and making decisions in the selection of key design parameters. The model is implemented in the MATLAB/Simulink environment. The performance simulation of a test vehicle is included as a numerical example to illustrate the effectiveness of the model.

Cycle life prediction of traction battery based on degradation data

The traction battery cycle life prediction method using performance degradation data was proposed. The example battery was a commercialized lithium-ion cell with LiMn2O4/Graphite cell system. The capacity faded with cycle number follows a traction function path. Two cycle life predicting models were established. The possible cycle life was extrapolated, which follows normal distribution well. The distribution parameters were estimated and the battery reliability was evaluated. The models＇ precision was validated and the effect of the cycle number on the predicting precision was analysed. The cycle life models and reliability evaluation method resolved the difficulty of battery life appraisal, such as long period and high cost.

Train energy simulation with locomotive adhesion model

Railway train energy simulation is an important and popular research topic.Locomotive traction force simulations are a fundamental part of such research.Conventional energy calculation models are not able to consider locomotive wheel-rail adhesions,traction adhesion control,and locomotive dynamics.This paper has developed two models to fill this research gap.The first model uses a 2D locomotive model with 27 degrees of freedom and a simplified wheel-rail contact model.The second model uses a 3D locomotive model with 54 degrees of freedom and a fully detailed wheel-rail contact model.Both models were integrated into a longitudinal train dynamics model with the consideration of locomotive adhesion control.Energy consumption simulations using a conventional model(1D model)and the two new models(2D and 3D models)were conducted and compared.The results show that,due to the consideration of wheel-rail adhesion model and traction control in the 3D model,it reports less energy consumption than the 1D model.The maximum difference in energy consumption rate between the 3D model and the 1D model was 12.5%.Due to the consideration of multiple wheel-rail contact points in the 3D model,it reports higher energy consumption than the 2D model.An 8.6%maximum difference in energy consumption rate between the 3D model and the 1D model was reported during curve negotiation.

Development of dynamic slip model for a shear crack

The objective of this paper is to develop a dynamic slip model for a shear crack under constant stress drop. This crack problem is formulated by a traction boundary integral equation （BIE） in the frequency domain and then solved by the hyper-singular boundary element method as well as the regularization technique proposed in this paper. Based on the spectral integral form of the kernel function, the unbounded term can be isolated and extracted from the hyper-singular kernel function by using the method of subtracted and added back in wave number domain. Finally, based on the inverse transformation from the frequency domain to the time domain, the time histories of crack opening displacement under constant stress drop can be determined. Three rupture models （simultaneous rupture model, symmetric bilaterally-propagating model and unilaterally propagating model） with specified time histories of stress drop are considered in this paper. Even though these three models will cause the same final slip shapes because of the same constant stress drop, the associated slip time functions differ significantly from each other during the rupture process.

Study of Even ^(230-238)U Isotopes by Using Cranked Nilsson Model,Single Particle Schrodinger Fluid and Collective Model

The Cranking Nilsson model is applied to calculate the single-particle energy eigenvalues and eigenfunctions of nuclei in a strongly deformed potential. Accordingly, The L. D. Energy, the Strutinsky inertia, the L. D. inertia, the volume conservation factor , the smoothed energy, the BCS energy, the G-value and the electric quadrupole moment of the five uranium isotopes: 230U, 232U, 234U, 236U and 238U are calculated as functions of the deformation parameter. Furthermore, the single-particle Schrodinger fluid is applied to calculate the rigid-body model, the cranking-model and the equilibrium-model moments of inertia of the five uranium isotopes. Moreover, the collective model is applied to calculate the rotational energies of these isotopes. The best potential and deformation parameters are also given.

结温导向的牵引变流器寿命优化控制

结温是影响绝缘栅双极型晶体管(IGBT)寿命的主要因素。为了提高地铁两电平牵引变流器寿命,提出一种降低结温的异步牵引电机双矢量模型预测转矩控制(DVMPTC)策略。将传统DVMPTC的第二个电压矢量选择范围缩小在与第一个电压矢量不切换或仅切换一次的范围,降低IGBT开关损耗的同时减小系统计算量;在代价函数中约束IGBT及其反并联二极管的损耗,动态加入损耗因子,并赋予权重系数,使得最优矢量的选择兼顾控制性能与降低损耗。通过仿真分析,本文所提方法相较于传统基于分段调制算法的直接转矩控制策略,降低了结温及其波动,提高了牵引变流器寿命。

数字孪生在轨道交通电力牵引系统应用的探讨与展望

随着我国轨道交通电力牵引系统的快速发展与技术成熟,其可靠性评估与智能化监控技术逐渐引起关注,数字孪生是基于数据与机器学习对实际物理系统的虚拟刻画技术,可以实现对实际物理系统的行为特征模拟与参数监测,因此将数字孪生技术引入轨道交通电力牵引系统领域,可为其数字化、智能化监控与运维提供发展思路与技术手段。文章首先对数字孪生技术目前在电力牵引系统中的应用现状进行了综述,进而列举了电力牵引系统数字孪生构建过程中所需的关键技术及其发展情况——在电力牵引系统领域,数字孪生及其相关技术仍在理论研究阶段,只有针对部分子系统的探索性研究,尚未形成完善的系统建模与智能监控体系;最后,文章展望了数字孪生技术在电力牵引系统领域的工程化实现前景,探讨了其投入工程应用可能会面临的内部技术问题与外部客观挑战,旨在为后续技术研究与实践提供参考。

基于热电类比的车载牵引变压器绕组区域暂态热响应特性研究

高速铁路动车组频繁穿梭于不同自然环境区域,且频繁“牵引-惰行-制动”状态切换,导致车载牵引变压器内部热场显著波动。为此,开展车载牵引变压器绕组区域暂态热响应相关研究:从车载牵引变压器绕组结构特性出发,基于热电类比提出停滞油热阻以考虑油流速度边界的影响,对热特性独立的单个冷却通道建立分布式暂态热网络模型,通过程序化编写实现可变结构参数的暂态热响应快速计算;基于已发表文献数据和计算流体动力学方法验证所提模型有效性;通过冷却通道时间常数、最热点温升稳定值定量分析绕组区域的暂态热响应特性及影响因素。结果表明:与CFD仿真相比,所提方法节省了99%以上的时间,平均相对误差为1.1%~3.1%,且适用范围不受结构参数限制;冷却通道时间常数与入口流速呈负相关,最热点温升稳定值与突变程度呈正相关、与入口流速呈负相关。

基于Simulink/MATLAB的实际地铁线路供电系统短路试验仿真分析

直流牵引供电系统在城市轨道交通中扮演着关键角色,其安全可靠的运行对整个城市轨道交通系统的运行至关重要。该文首先介绍地铁牵引供电系统的结构和功能,并建立地铁外部交流电源、整流机组和牵引网络的仿真模型。该仿真模型根据实际地铁牵引供电系统的结构和参数进行构建,旨在研究不同短路情况下的短路特性,包括电源出口短路、近距离短路和远距离短路。通过评估供电系统在短路故障下的稳定性和可靠性,得出若干研究结果。这些结果为地铁供电系统选择合适的一次设备提供理论依据,有助于确保城市轨道交通供电系统的稳定性和可靠性。

干式车载牵引变压器绕组区域动态温度计算模型

干式车载牵引变压器质量轻、安全系数高,但其内部热场随运行环境及负荷状态频繁波动。为实现干式车载牵引变压器绕组动态温度的快速计算,基于热电类比原理搭建分布式动态热网络拓扑结构,并借助CFD模型开展仿真试验,探究运行参数和风道尺寸对散热性能的影响,提出风道出口温度计算方法;基于干式车载牵引变压器绕组温升试验平台,验证动态温度计算模型的有效性。结果表明:针对不同结构参数和时变运行场景,所建绕组动态温度计算模型均能准确获取绕组区域温度分布及动态变化情况,相比CFD数值仿真节省99%以上的时间成本,有助于干式车载牵引变压器热容量的合理规划和设计效率的进一步提高。

GFRP型材-混凝土组合梁受弯性能分析

为了研究玻璃钢纤维(GFRP)型材-混凝土组合梁的受弯性能,采用有限元分析软件ABAQUS建立其数值模型并进行模拟分析。对混凝土采用塑性损伤模型,并考虑了GFRP型材的各向异性的特征,连接界面采用牵引-分离模型来模拟GFRP型材与混凝土的粘结-滑移行为。试验结果验证了模拟分析的正确性。此外,进行了参数扩展分析,研究了混凝土板截面尺寸、GFRP型材截面尺寸(腹板高度和腹板、翼缘板厚度)对GFRP型材-混凝土组合梁受弯性能的影响。结果表明:剪力键间距为100mm的组合梁的极限承载力比间距为150、200mm的试件分别高21.4%和30.7%。FRP剪力键可有效提高抗剪性能,改善界面粘结性能。混凝土截面高宽比超过1.2时,组合梁破坏模式从受弯破坏向剥离破坏转变。合理设计组合梁截面尺寸可以有效地提高组合梁的极限抗弯承载力、最大挠度和拟延性特征,在力学性能和工程造价之间取得良好的平衡。

基于二元相关退化的动车组车载变压器油纸绝缘剩余寿命预测

针对动车组车载变压器油纸绝缘剩余寿命预测中单性能退化指标难以全面反映油纸绝缘退化过程的问题,考虑车载变压器油纸绝缘退化的个体差异性及两性能指标间的相关关系,提出了基于Copula函数的两性能指标相关退化的油纸绝缘剩余寿命预测方法:采用具有随机效应的维纳过程建立油纸绝缘的两性能指标相关退化模型,基于赤池信息准则(Akaike Information Criterion, AIC)选择拟合效果更优的Copula函数来描述两性能指标间的相关关系,采用最大似然估计法估计初始时刻的模型参数,基于序列贝叶斯更新方法在线更新退化模型中的漂移系数,以实现油纸绝缘剩余寿命的在线预测。最后以加速热老化试验下油纸绝缘的聚合度和抗拉强度的退化数据进行实例验证。结果表明,两性能指标相关退化模型比单性能指标退化模型的剩余寿命预测值与实际值之间的平均绝对误差更小,预测的准确性更高,且随着模型参数不断更新,剩余寿命的预测值与实际值间的绝对误差在不断减小,预测结果的准确性在不断提升。

共母线开绕组永磁同步牵引电机级联模型预测电流控制

为抑制共母线开绕组永磁同步牵引电机传动系统转矩脉动和由共模电压以及三次谐波反电动势作用于零轴回路产生的零序电流,提出一种自抗扰级联模型预测电流控制方法。首先,在第1级采用第1个有效电压矢量使得q轴电流增加,第2个有效电压矢量使得q轴电流减小,这一新的筛选组合规则将2个有效矢量根据对q轴电流作用效果分组寻优和作用时间分配;其次,在第2级对第1级所选有效电压矢量的零轴分量局部寻优,在第3级对第1级和第2级优化后系统产生的零轴电流分量采用极性相反的零矢量进行矢量分类寻优抑制,并精确分配作用时间;然后,在第4级对前3级所选电压矢量进行开关状态局部寻优,确定最优电压矢量的低开关频率状态组合作用于逆变器。最后,引入自抗扰控制减少电机启动加速过程中的调速超调,并对所提策略和双矢量模型预测电流控制进行稳态和动态仿真对比。结果表明:所提策略对转矩脉动、零轴电流、总谐波畸变率、开关频率和调速超调都具有很好的抑制效果,避免了传统模型预测控制的多目标代价函数中权重系数整定,对系统的控制性能有明显的提升作用。研究结果为进一步对共母线开绕组永磁同步牵引电机传动系统弱磁控制进行究,以及将驱动控制系统应用于机车牵引提供参考。