Rail fastener defect inspection method for multi railways based on machine vision

Purpose–This research aims to improve the performance of rail fastener defect inspection method for multi railways,to effectively ensure the safety of railway operation.Design/methodology/approach–Firstly,a fastener region location method based on online learning strategy was proposed,which can locate fastener regions according to the prior knowledge of track image and template matching method.Online learning strategy is used to update the template library dynamically,so that the method not only can locate fastener regions in the track images of multi railways,but also can automatically collect and annotate fastener samples.Secondly,a fastener defect recognition method based on deep convolutional neural network was proposed.The structure of recognition network was designed according to the smaller size and the relatively single content of the fastener region.The data augmentation method based on the sample random sorting strategy is adopted to reduce the impact of the imbalance of sample size on recognition performance.Findings–Test verification of the proposed method is conducted based on the rail fastener datasets of multi railways.Specifically,fastener location module has achieved an average detection rate of 99.36%,and fastener defect recognition module has achieved an average precision of 96.82%.Originality/value–The proposed method can accurately locate fastener regions and identify fastener defect in the track images of different railways,which has high reliability and strong adaptability to multi railways.

更快速度下周期性短波不平顺引起的轮轨高频振动特性及控制限值

随着列车运行速度的不断加快,轮轨高频振动引起的车辆、轨道部件伤损问题更加突出,尤以周期性的短波不平顺最为常见。为了掌握轮轨高频振动自下而上的传递衰减规律以及制定合理的钢轨打磨策略,有必要针对车辆系统在高频激励条件下的耦合振动特性开展深入的理论研究。本文通过对大量实测数据的拟合,得到了更宽频段范围内的轨道高低不平顺谱拟合公式,并通过反演得到了0.002~100 m波长范围内的高低不平顺样本;在此基础上建立了高速动车组-轨道刚柔耦合动力学模型,其中对轮对、钢轨均考虑了弹性体振动模态,仿真分析了周期性短波不平顺引起的轮轨高频振动特性。结果表明,车辆各部件的振动频率分布范围为30~1390 Hz,且自下至上呈逐层衰减趋势。通过提取周期性短波不平顺幅值变化对轮轨相互作用的影响规律,进一步提出了适应400 km/h高速铁路的典型波长周期性短波不平顺的量化控制限值要求。

Estimation of speed-related car body acceleration limits with quantile regression

Purpose–This study aimed to facilitate a rapid evaluation of track service status and vehicle ride comfort based on car body acceleration.Consequently,a low-cost,data-driven approach was proposed for analyzing speed-related acceleration limits in metro systems.Design/methodology/approach–A portable sensing terminal was developed to realize easy and efficient detection of car body acceleration.Further,field measurements were performed on a 51.95-km metro line.Data from 272 metro sections were tested as a case study,and a quantile regression method was proposed to fit the control limits of the car body acceleration at different speeds using the measured data.Findings–First,the frequency statistics of the measured data in the speed-acceleration dimension indicated that the car body acceleration was primarily concentrated within the constant speed stage,particularly at speeds of 15.4,18.3,and 20.9 m/s.Second,resampling was performed according to the probability density distribution of car body acceleration for different speed domains to achieve data balance.Finally,combined with the traditional linear relationship between speed and acceleration,the statistical relationships between the speed and car body acceleration under different quantiles were determined.We concluded the lateral/vertical quantiles of 0.8989/0.9895,0.9942/0.997,and 0.9998/0.993 as being excellent,good,and qualified control limits,respectively,for the lateral and vertical acceleration of the car body.In addition,regression lines for the speedrelated acceleration limits at other quantiles(0.5,0.75,2s,and 3s)were obtained.Originality/value–The proposed method is expected to serve as a reference for further studies on speedrelated acceleration limits in rail transit systems.

Development of track geometry inspection equipment for high-speed comprehensive inspection train in China

Purpose–This study aims to analyze the development direction of track geometry inspection equipment for high-speed comprehensive inspection train in China.Design/methodology/approach–The development of track geometry inspection equipment for highspeed comprehensive inspection train in China in the past 20 years can be divided into 3 stages.Track geometry inspection equipment 1.0 is the stage of analog signal.At the stage 1.0,the first priority is to meet the China’s railways basic needs of pre-operation joint debugging,safety assessment and daily dynamic inspection,maintenance and repair after operation.Track geometry inspection equipment 2.0 is the stage of digital signal.At the stage 2.0,it is important to improve stability and reliability of track geometry inspection equipment by upgrading the hardware sensors and improving software architecture.Track geometry inspection equipment 3.0 is the stage of lightweight.At the stage 3.0,miniaturization,low power consumption,self-running and green economy are co-developing on demand.Findings–The ability of track geometry inspection equipment for high-speed comprehensive inspection train will be expanded.The dynamic inspection of track stiffness changes will be studied under loaded and unloaded conditions in response to the track local settlement,track plate detachment and cushion plate failure.The dynamic measurement method of rail surface slope and vertical curve radius will be proposed,to reveal the changes in railway profile parameters of high-speed railways and the relationship between railway profile,track irregularity and subsidence of subgrade and bridges.The 200 m cut-off wavelength of track regularity will be researched to adapt to the operating speed of 400 km/h.Originality/value–The research can provide new connotations and requirements of track geometry inspection equipment for high-speed comprehensive inspection train in the new railway stage.

A study on characteristic indexesof railway ballast bed underhigh-frequency radar

Purpose–In this paper,a high-frequency radar test system was used to collect the data of clean ballast bed and fouled ballast bed of ballasted tracks,respectively,for a quantitative evaluation of the condition of railway ballast bed.Design/methodology/approach–Based on original radar signals,the time–frequency characteristics of radar signals were analyzed,five ballast bed condition characteristic indexes were proposed,including the frequency domain integral area,scanning area,number of intersections with the time axis,number of timedomain inflection points and amplitude envelope obtained by Hilbert transform,and the effectiveness and sensitivity of the indexes were analyzed.Findings–The thickness of ballast bed tested at the sleep bottom by high-frequency radar is up to 55 cm,which meets the requirements of ballast bed detection.Compared with clean ballast bed,the values of the five indexes of fouled ballast bed are larger,and the five indexes could effectively show the condition of the ballast bed.The computational efficiency of amplitude envelope obtained by Hilbert transform is 140 s$km
1,and the computational efficiency of other indexes is 5 s$km
1.The amplitude envelopes obtained by Hilbert transform in the subgrade sections and tunnel sections are the most sensitive,followed by scanning area.The number of intersections with the time axis in the bridge sections was the most sensitive,followed by the scanning area.The scanning area can adapt to different substructures such as subgrade,bridges and tunnels,with high comprehensive sensitivity.Originality/value–The research can provide appropriate characteristic indexes from the high-frequency radar original signal to quantitatively evaluate ballast bed condition under different substructures.

A vertical coupling dynamic analysis method and engineering application of vehicle–track–substructure based on forced vibration

Purpose–This study aims to propose a vertical coupling dynamic analysis method of vehicle–track–substructure based on forced vibration and use this method to analyze the influence on the dynamic response of track and vehicle caused by local fastener failure.Design/methodology/approach–The track and substructure are decomposed into the rail subsystem and substructure subsystem,in which the rail subsystem is composed of two layers of nodes corresponding to the upper rail and the lower fastener.The rail is treated as a continuous beam with elastic discrete point supports,and spring-damping elements are used to simulate the constraints between rail and fastener.Forced displacement and forced velocity are used to deal with the effect of the substructure on the rail system,while the external load is used to deal with the reverse effect.The fastener failure is simulated with the methods that cancel the forced vibration transmission,namely take no account of the substructure–rail interaction at that position.Findings–The dynamic characteristics of the infrastructure with local diseases can be accurately calculated by using the proposed method.Local fastener failure will slightly affect the vibration of substructure and carbody,but it will significantly intensify the vibration response between wheel and rail.The maximum vertical displacement and the maximum vertical vibration acceleration of rail is 2.94 times and 2.97 times the normal value,respectively,under the train speed of 350 km$h
1.At the same time,the maximum wheel–rail force and wheel load reduction rate increase by 22.0 and 50.2%,respectively,from the normal value.Originality/value–This method can better reveal the local vibration conditions of the rail and easily simulate the influence of various defects on the dynamic response of the coupling system.