Geometry deviation effects of railway catenaries on pantograph– catenary interaction: a case study in Norwegian Railway System

This paper presents a non-contact measurement of the realistic catenary geometry deviation in the Norwegian railway network through a laser rangefinder.The random geometry deviation is included in the catenary model to investigate its effect on the pantograph–catenary interaction.The dispersion of the longitudinal deviation is assumed to follow a Gaussian distribution.A power spectrum density represents the vertical deviation in the contact wire.Based on the Monte Carlo method,several geometry deviation samples are generated and included in the catenary model.A lumped mass pantograph with flexible collectors is employed to reproduce the high-frequency behaviours.The stochastic analysis results indicate that the catenary geometry deviation causes a significant dispersion of the pantograph–catenary interaction response.The contact force standard deviations measured by the inspection vehicle are within the scope of the simulation results.A critical cut-off frequency that covers 1/16 of the dropper interval is suggested to fully describe the effect of the catenary geometry deviation on the contact force.The statistical minimum contact force is recommended to be modified according to the tolerant contact loss rate at high frequency.An unpleasant interaction performance of the pantograph–catenary can be expected at the catenary top speed when the random catenary geometry deviation is included.

Towards the performance limit of catenary meta-optics via field-driven optimization

Catenary optics enables metasurfaces with higher efficiency and wider bandwidth,and is highly anticipated in the imaging system,super-resolution lithography,and broadband absorbers.However,the periodic boundary approximation without considering aperiodic electromagnetic crosstalk poses challenges for catenary optical devices to reach their performance limits.Here,perfect control of both local geometric and propagation phases is realized through field-driven optimization,in which the field distribution is calculated under real boundary conditions.Different from other optimization methods requiring a mass of iterations,the proposed design method requires less than ten iterations to get the efficiency close to the optimal value.Based on the library of shape-optimized catenary structures,centimeter-scale devices can be designed in ten seconds,with the performance improved by ~15%.Furthermore,this method has the ability to extend catenary-like continuous structures to arbitrary polarization,including both linear and elliptical polarizations,which is difficult to achieve with traditional design methods.It provides a way for the development of catenary optics and serves as a potent tool for constructing high-performance optical devices.

A Novel Method for Aging Prediction of Railway Catenary Based on Improved Kalman Filter

The aging prediction of railway catenary is of profound significance for ensuring the regular operation of electrified trains.However,in real-world scenarios,accurate predictions are challenging due to various interferences.This paper addresses this challenge by proposing a novel method for predicting the aging of railway catenary based on an improved Kalman filter(KF).The proposed method focuses on modifying the priori state estimate covariance and measurement error covariance of the KF to enhance accuracy in complex environments.By comparing the optimal displacement value with the theoretically calculated value based on the thermal expansion effect of metals,it becomes possible to ascertain the aging status of the catenary.To improve prediction accuracy,a railway catenary aging prediction model is constructed by integrating the Takagi-Sugeno(T-S)fuzzy neural network(FNN)and KF.In this model,an adaptive training method is introduced,allowing the FNN to use fewer fuzzy rules.The inputs of the model include time,temperature,and historical displacement,while the output is the predicted displacement.Furthermore,the KF is enhanced by modifying its prior state estimate covariance and measurement error covariance.These modifications contribute to more accurate predictions.Lastly,a low-power experimental platform based on FPGA is implemented to verify the effectiveness of the proposed method.The test results demonstrate that the proposed method outperforms the compared method,showcasing its superior performance.

Trajectory compensation for multi-robot coordinated lifting system considering elastic catenary of the rope

The multi-robot coordinated lifting system is an unconstrained system with a rigid and flexible coupling.The deformation of the flexible rope causes errors in the movement trajectory of the lifting system.Based on the kinematic and dynamic analysis of the lifting system,the elastic catenary mod-el considering the elasticity and mass of the flexible rope is established,and the effect of the deform-ation of the flexible rope on the position and posture of the suspended object is analyzed.According to the deformation of flexible rope,a real-time trajectory compensation method is proposed based on the compensation principle of position and posture.Under the lifting task of the low-speed move-ment,this is compared with that of the system which neglects the deformation of the flexible rope.The trajectoy of the lifting system considering the deformation of flexible rope.The results show that the mass and elasticity of the flexible rope can not be neglected.Meanwhile,the proposed trajectory compensation method can improve the movement accuracy of the lifting system,which verifies the ef-fectiveness of this compensation method.The research results provide the basis for trajectory plan-ning and coordinated control of the lifting system。

Catenary dropper fault identification based on improved FCOS algorithm

The contact network dropper works in a harsh environment,and suffers from the impact effect of pantographs during running of trains,which may lead to faults such as slack and broken of the dropper wire and broken of the current-carrying ring.Due to the low intelligence and poor accuracy of the dropper fault detection network,an improved fully convolutional one-stage(FCOS)object detection network was proposed to improve the detection capability of the dropper condition.Firstly,by adjusting the parameterαin the network focus loss function,the problem of positive and negative sample imbalance in the network training process was eliminated.Secondly,the generalized intersection over union(GIoU)calculation was introduced to enhance the network’s ability to recognize the relative spatial positions of the prediction box and the bounding box during the regression calculation.Finally,the improved network was used to detect the status of dropper pictures.The detection speed was 150 sheets per millisecond,and the MAP of different status detection was 0.9512.Through the simulation comparison with other object detection networks,it was proved that the improved FCOS network had advantages in both detection time and accuracy,and could identify the state of dropper accurately.

电气化铁路接触网冲击振动除冰仿真分析

接触线覆冰严重影响电气化铁路的正常运行。通过Ansys有限元分析软件创建简单链形悬挂接触网有限元模型,采用负驰度法分析接触网模型的静力初始形态,在此基础上建立接触网覆冰模型。对模型进行模态分析和瞬态动力学分析,通过承力索驰度、模型固有频率以及网格收敛性3方面验证模型的合理性。基于人工敲打机械除冰方法,结合除冰准则,研究不同加载点、不同载荷大小以及不同覆冰层厚度对除冰效果的影响。综合分析各种载荷方式,归纳总结接触网除冰的一般规律,使除冰效果达到最佳。

新型电缆贯通供电系统短路特性分析

新型电缆贯通供电系统能够实现长距离输电、减少电分相数目,但两级供电模式将导致该系统结构复杂.为研究电缆贯通供电系统短路特性,首先,建立单位长度的牵引电缆和接触网-钢轨的二端口网络参数,将各个子网络级联等效成1个二端口网络,进而转化为Ⅱ型电路,实现牵引电缆和接触网-钢轨任意长度的分布参数建模;由于接触网短路后导致机车电压下降,基于车网耦合关系采用迭代计算求解短路电流电压,仿真验证计算方法的准确性.最后,解析不同短路类型的电气特性,重点分析分布电容对短路电流、电压的影响.研究结果表明:分布电容会引起短路电流增大,且在不同短路情况下均造成牵引变压器输出电压增加;接触网短路电流由两侧牵引变压器共同提供,距短路点越远提供的电流越少;电缆相间短路对非故障回路机车运行影响最大.

基于多尺度融合金字塔焦点网络的接触网零部件检测

作为高铁牵引供电系统的重要组成部分,接触网系统承担着向动车组传输电能的重要功能.实际工程运营表明,受弓网交互产生的持续冲击以及外部环境的影响,接触网支撑部件可能会出现“松、脱、断、裂”等缺陷,导致接触网结构可靠性下降,严重影响接触网系统稳定运行.因此,及时精确定位接触网支撑部件(CSCs),对保障高铁安全运行和完善接触网检修维护策略具有重大意义.然而,CSCs的检测通常面临着零部件种类多、尺度差异大、部分零部件微小的问题.针对以上问题,本文提出一种基于多尺度融合金字塔焦点网络的接触网零部件检测算法,将平衡模块和特征金字塔模块相结合,提高对小目标的检测性能.首先,设计了可分离残差金字塔聚合模块(SRPAM),用于优化模型多尺度特征提取能力、扩大感受野,缓解CSCs检测的多尺度问题;其次,设计了一种基于平衡特征金字塔的路径聚合网络(PA-BFPN),用于提升跨层特征融合效率和小目标检测性能.最后,通过对比试验、可视化实验和消融实验证明了所提方法的有效性和优越性.其中,所提的MFPFCOS在CSCs数据集上的检测精度(mAP)能够在达到48.6%的同时,实现30的FLOPs(Floating point operations per second),表明所提方法能够在检测精度和检测速度之间保持良好的平衡.

Review of research on interactions between deepwater steel catenary risers and soft clay seabeds

Steel catenary risers （SCR） have become an enabling technology for deepwater environments. A comprehensive review was conducted on recent research that examined interactions between deepwater steel catenary risers and soft clay seabeds. This included the STRIDE （steel risers in deepwater environments） and CARISIMA （catenary riser soil interaction model for global riser analysis） joint jndustry jrogram＇s test data as well as information from existing papers.

成兰铁路接触网缺陷分析与整治

接触网燃弧整治一直是工程难点,存在原因难以确定,整治手段缺乏等问题。在成兰铁路联调过程中,通过弓网受流试验发现了大量燃弧缺陷、受电弓异常振动现象,经检测数据联合分析并结合现场调查,完成了燃弧缺陷的精准判断与整治;通过硬点频谱分析确定了硬点类型,并验证了整治效果。复测结果证明通过数据分析快速定位缺陷位置、判断缺陷类型并进行针对性整治,可以有效降低燃弧率,改善线路整体弓网受流性能。

Study on A New Mooring System Integrating Catenary with Taut Mooring

Analyzed are the merits and demerits of catenary mooring system and taut mooring system, which are commonly used nowadays. As falling somewhere between these two systems, a new mooring system integrating catenary with taut mooring is proposed. In order to expound and prove the advantages of this new system, the motion performance of a semi-submersible platform is simulated by employing full time domain coupled analysis method. A comparison of the result of new mooting system with that of taut mooring system shows that the movement of the platform using the new type mooting system is smaller than that using the taut mooring system, which ensures a better working condition. Furthermore, the new mooring system is also compatible with the characteristics of catenary mooting system, which eliminates the requirement of anti-uplift capacity of the anchors.

Dynamic Response Study of Steel Catenary Riser Based on Slender Rod Model

A numerical model of the steel catenary riser(SCR) is built based on the slender rod model. The slender rod model,which describes the behavior of the slender riser in terms of the center line position, can solve the geometrical nonlinearity effectively. In a marine environment, the SCR is under the combined internal flow and external loads,such as wave and current. A general analysis considers only the inertial force and the drag force caused by the wave and current. However, the internal flow has an effect on the SCR; it is essential to explore the dynamic response of the SCR with the internal flow. The SCR also suffers the lift force and the fluctuating drag force because of the current. Finite element method is utilized to solve the motion equations. The effects of the internal flow, wave and current on the dynamic response of the SCR are considered. The results indicate that the increase of the internal flow density leads to the decrease of the displacement of the SCR, while the internal flow velocity has little effect on the SCR. The displacement of the SCR increases with the increase of the wave height and period. And the increasing wave period results in an increase in the vibration period of the SCR. The current velocity changes the displacements of the SCR in x-and z-directions. The vibration frequency of the SCR in y-direction increases with the increase of the current velocity.

Fatigue Characteristic Analysis of Deepwater Steel Catenary Risers at the Touchdown Point

This paper presents fatigue characteristic analysis of a deepwater steel catenary riser （SCR） under ambient excitations. The SCR involves complex nonlinear dynamic behaviors, especially at the touchdown point （TDP） where the riser first touches the seafloor. Owing to the significant interaction with soil, the touchdown zone is difficnlt to be modeled. Based on Lumped-Mass method and P-y curve, nonlinear springs are used to simulate the SCR-seabed coupled interaction. In case studies, an SCR＇s dynamic features have been obtained by transient analysis and the structure fatigue assessment has been carried out by S-N approach. The comparative analysis shows that the TDP is the key location where soil-riser interaction rises steeply and minimum fatigue life occurs. Parameters such as ocean environment loads, vessel motions, riser material and geometric parameters are discussed. The results indicate that the vessel motion is the principal factor for the structure fatigue life distribution.

Pantograph and catenary system with double pantographs for high-speed trains at 350 km/h or higher

The paper is aimed at developing an optimized design of the pantograph and catenary system with double pantographs at a speed of 350 km/h for the Wuhan-Guangzhou high-speed railway. First, the pantograph and catenary system for the Beijing-Tianjin high-speed railway was analyzed to verify whether its design objective could be fulfilled. It shows that the system is not able to satisfy the requirement of a sustainable running speed of 350 km/h. Then a new scheme for the pantograph and catenary system is proposed through optimization and renovation of the structure and parameters of the pantograph and catenary system, including the suspension type of the catenary, tension of the contact wire, and space between two pantographs. Finally, the dynamic performance of the new system was verified by simulation and line testing. The results show that the new scheme of the pantograph and catenary system for the Wuhan- Guangzhou high-speed railway is acceptable, in which the steady contact between the rear pantograph and the catenary at the space of 200 m can be maintained to ensure the current-collection quality. A current collection with double pantographs at a speed of 350 km/h or higher can be achieved.

Advances of research on high-speed railway catenary

The interaction between the catenary and pantograph is one of the most crucial factors that determine the train operation in high-speed railway. The bad state of catenary is able to directly influence the power supply safety of traction power system. In this paper, four aspects on the catenary research of high-speed railway are reviewed in detail, namely the solution methods for catenary equilibrium state, the dynamic modeling methods of catenary, the non-contact detection methods of catenary, and the static and dynamic evaluation methods of catenary. In addition, their recent advances are described. For the low solution accuracy of the initial equilibrium state of cate- nary, the structure finding method with multi-objective constraint and nonlinear finite element procedure are introduced to solve the problem. For the catenary＇s dynamic modeling, considering the influence of environmental wind on the catenary, environmental wind simula- tions and wind tunnel tests are used to obtain the aerodynamic coefficients and build the wind field along the catenary for analysis of its wind vibration characteristics. In order to improve the detection accuracy of non-contact detection for the catenary, the deep learning theory and real-time detection algorithms should be adopted in the future. In view of the lack of dynamic assessment method for the catenary, the modern spectrum evaluation, timefrequency analysis, big data technology and their combi- nations will be the important means for future catenary evaluation.

Multiaxial Fatigue Analyses of Stress Joints for Deepwater Steel Catenary Risers

In the present study, the dynamic and fatigue characteristics of two types of stress joints are investigated under ocean environmental condition. Connected with the riser and the platform, stress joint at the vessel hang-off position should be one of the main critical design challenges for a steel catenary riser （SCR） in deepwater. When the riser is under a high pressure and deepwater working condition, the stress state for the joint is more complex, and the fatigue damage is easy to occur at this position. Stress joint discussed in this paper includes two types： Tapered Stress Joint （TSJ） and Sleeved Stress Joint （SSJ）, and multiaxial fatigue analysis results are given for comparison. Global dynamic analysis for an SCR is performed first, and then the local boundary conditions obtained from the previous analysis are applied to the stress joint FE model for the later dynamic and multiaxial fatigue analysis. Results indicate that the stress level is far lower than the yield limit of material and the damage induced by fatigue needs more attention. Besides, the damage character of the two types of stress joints differs： for TSJ, the place where the stress joint connects with the riser is easy to occur fatigue damage; for SSJ, the most probable position is at the place where the end of the inner sleeve pipe contacts with the riser body. Compared with SSJ, TSJ shows a higher stress level but better fatigue performance, and it will have a higher material cost. In consideration of various factors, designers should choose the most suitable type and also geometric parameters.

Cross-Flow VIV-Induced Fatigue Damage of Deepwater Steel Catenary Riser at Touch-Down Point

A prediction model of the deepwater steel catenary riser VIV is proposed based on the forced oscillation test data, taking into account the riser-seafloor interaction for the cross-flow VIV-induced fatigue damage at touch-down point （TDP）. The model will give more reasonable simulation of SCR response near TDP than the previous pinned truncation model. In the present model, the hysteretic riser-soil interaction model is simplified as the linear spring and damper to simulate the seafloor, and the damping is obtained according to the dissipative power during one periodic riser-soil interaction. In order to validate the model, the comparison with the field measurement and the results predicted by Shear 7 program of a full-scale steel catenary riser is carried out. The main induced modes, mode frequencies and response amplitude are in a good agreement. Furthermore, the parametric studies are carried out to broaden the understanding of the fatigue damage sensitivity to the upper end in-plane offset and seabed characteristics. In addition, the fatigue stress comparison at TDP between the truncation riser model and the present full riser model shows that the existence of touch-down zones is very important for the fatigue damage assessment of steel catenary riser at TDP.

Dynamics of Large-Truncated Mooring Systems Coupled with A Catenary Moored Semi-Submersible

With the floating structures pushing their activities to the ultra-deep water, model tests have presented a challenge due to the limitation of the existing wave basins. Therefore, the concept of truncated mooring system is implemented to replace the full depth mooring system in the model tests, which aims to have the same dynamic responses as the full depth system. The truncated mooring system plays such a significant role that extra attention should be paid to the mooring systems with large truncation factor. Three different types of large truncation factor mooring system are being employed in the simulations, including the homogenously truncated mooring system, non-homogenously truncated mooring system and simplified truncated mooring system. A catenary moored semi-submersible operating at 1000 m water depth is presented. In addition, truncated mooring systems are proposed at the truncated water depth of 200 m. In order to explore the applicability of these truncated mooring systems, numerical simulations of the platform’s surge free decay interacting with three different styles of truncated mooring systems are studied in calm water. Furthermore, the mooring-induced damping of the truncated mooring systems is simulated in the regular wave. Finally, the platform motion responses and mooring line dynamics are simulated in irregular wave. All these simulations are implemented by employing full time domain coupled dynamic analysis, and the results are compared with those of the full depth simulations in the same cases. The results show that the mooring-induced damping plays a significant role in platform motion responses, and all truncated mooring systems are suitable for model tests with appropriate truncated mooring line diameters. However, a large diameter is needed for simplified truncated mooring lines. The suggestions are given to the selection of truncated mooring system for different situations as well as to the truncated mooring design criteria.

Synergetic Analysis and Possible Control of Vortex-Induced Vibrations in a Fluid-Conveying Steel Catenary Riser

This work aimed to demonstrate possibilities for both active and passive control of the vortex-induced vibration and fatigue life of steel catenary risers via an analysis of the self-organization and evolution of the structural vibration based on synergetic theory. An analysis of the complex interrelated and synergistic relationship between the order parameter and the fast variable was performed, and the master equation of the nodal displacements was established as the order parameter for the evolution of the riser's structural vibration. Passive control methods include modifying the structure's elastic modulus, the internal fluid velocity, the top tension and the structural damping ratio, while an active control involves adjusting the external flow rate. Optimized parameters were obtained by analyzing the non-steady state solution of the master equation. The results show that the fatigue life greatly increases as the riser's elastic modulus decreases. In contrast, the fatigue life decreases with an increase of the internal fluid velocity. With an increase of the top tension, the vibration amplitudes and the number of modes may decrease, resulting in fewer bending stress cycles and a longer fatigue life. Furthermore, the structural damping ratio should be as large as possible. Finally, an active and passive control of the riser structure's response to vortex-induced vibration and its fatigue life can be achieved by carefully modifying the parameters mentioned above. The results may provide a theoretical framework for engineering practice concerning the design and control of steel catenary riser structures which are affected by vortex-induced vibration.

Fatigue life evaluation on key components of high-speed railway catenary system

The fatigue load spectrum and operation life evaluation of key components in the catenary system under the high speed train running condition were investigated.Firstly,based on the catenary model and pantograph model,the couple dynamic equations of pantograph–catenary were built with the Lagrange’s method;then the dynamic contact force was obtained by the Newmark method at the train speeds of 250,280 and 300 km/h,respectively.Secondly,the finite element model(FEM)of one anchor section’s catenary was built to analyze its transient response under the contact force as train running;then the loading time history of messenger wire base,steady arm,registration tube,oblique cantilever,and straight cantilever were extracted.Finally,the key components’fatigue spectrum was carried out by the rain-flow counting method,and operation life was estimated in consideration of such coefficients,such as stress concentration,shape and dimension,surface treatment.The results show that the fatigue life of the catenary system reduces with the increasing of train speed;specifically,the evaluated fatigue life of the steady arm is shorter than other components.