Train wheel-rail force collaborative calibration based on GNN-LSTM

Accurate wheel-rail force data serves as the cornerstone for analyzing the wheel-rail relationship.However,achieving continuous and precise measurement of this force remains a significant challenge in the field.This article introduces a calibration algorithm for the wheel-rail force that leverages graph neural networks and long short-term memory networks.Initially,a comprehensive wheel-rail force detection system for trains was constructed,encompassing two key components:an instrumented wheelset and a ground wheel-rail force measuring system.Subsequently,utilizing this system,two distinct datasets were acquired from the track inspection vehicle:instrumented wheelset data and ground wheel-rail force data,a feedforward neural network was employed to calibrate the instrumented wheelset data,referencing the ground wheel-rail force data.Furthermore,ground wheel-rail force data for the locomotive was obtained for the corresponding road section.This data was then integrated with the calibrated instrumented wheelset data from the track inspection vehicle.Leveraging the GNN-LSTM network,the article establishes a mapping relationship model between the wheel-rail force of the track inspection vehicle and the locomotive wheel-rail force.This model facilitates continuous measurement of locomotive wheel-rail forces across three typical scenarios:straight sections,long and steep downhill sections,and small curve radius sections.

Imaging a force field via an optically levitated nanoparticle array

Levitated optomechanical systems represent an excellent candidate platform for force and acceleration sensing.We propose a force-sensing protocol utilizing an optically levitated nanoparticle array.In our scheme,N nanoparticles are trapped in an optical cavity using holographic optical tweezers.An external laser drives the cavity,exciting N cavity modes interacting simultaneously with the N nanoparticles.The optomechanical interaction encodes the information of the force acting on each nanoparticle onto the intracavity photons,which can be detected directly at the output ports of the cavity.Consequently,our protocol enables real-time imaging of a force field.

Research on the influence of flexible wheelset rotation effect on wheel rail contact force

Purpose-Under the high-speed operating conditions,the effects of wheelset elastic deformation on the wheel rail dynamic forces will become more notable compared to the low-speed condition.In order to meet different analysis requirements and selecting appropriate models to analyzing the wheel rail interaction,it is crucial to understand the influence of wheelset flexibility on the wheel-rail dynamics under different speeds and track excitations condition.Design/methodology/approach-The wheel rail contact points solving method and vehicle dynamics equations considering wheelset flexibility in the trajectory body coordinate system were investigated in this paper.As for the wheel-rail contact forces,which is a particular force element in vehicle multibody system,a method for calculating the Jacobian matrix of the wheel-rail contact force is proposed to better couple the wheel-rail contact force calculation with the vehicle dynamics response calculation.Based on the flexible wheelset modeling approach in this paper,two vehicle dynamic models considering the wheelset as both elastic and rigid bodies are established,two kinds of track excitations,namely normal measured track irregularities and short-wave irregularities are used,wheel-rail geometric contact characteristic and wheel-rail contact forces in both time and frequency domains are compared with the two models in order to study the influence of flexible wheelset rotation effect on wheel rail contact force.Findings-Under normal track irregularity excitations,the amplitudes of vertical,longitudinal and lateral forces computed by the flexible wheelset model are smaller than those of the rigid wheelset model,and the virtual penetration and equivalent contact patch are also slightly smaller.For the flexible wheelset model,the wheel rail longitudinal and lateral creepages will also decrease.The higher the vehicle speed,the larger the differences in wheel-rail forces computed by the flexible and rigid wheelset model.Under track short-wave irregularity excitations,the vertical force amplitude computed by the flexible wheelset is also smaller than that of the rigid wheelset.However,unlike the excitation case of measured track irregularity,under short-wave excitations,for the speed within the range of 200 to 350 km/h,the difference in the amplitude of the vertical force between the flexible and rigid wheelset models gradually decreases as the speed increase.This is partly due to the contribution of wheelset's elastic vibration under short-wave excitations.For low-frequency wheel-rail force analysis problems at speeds of 350 km/h and above,as well as high-frequency wheel-rail interaction analysis problems under various speed conditions,the flexible wheelset model will give results agrees better with the reality.Originality/value-This study provides reference for the modeling method of the flexible wheelset and the coupling method of wheel-rail contact force to the vehicle multibody dynamics system.Furthermore,by comparative research,the influence of wheelset flexibility and rotation on wheel-rail dynamic behavior are obtained,which is useful to the application scope of rigid and flexible wheelset models.

Flexible Tactile Electronic Skin Sensor with 3D Force Detection Based on Porous CNTs/PDMS Nanocomposites

Flexible tactile sensors have broad applications in human physiological monitoring,robotic operation and human-machine interaction.However,the research of wearable and flexible tactile sensors with high sensitivity,wide sensing range and ability to detect three-dimensional(3D)force is still very challenging.Herein,a flexible tactile electronic skin sensor based on carbon nanotubes(CNTs)/polydimethylsiloxane(PDMS)nanocomposites is presented for 3D contact force detection.The 3D forces were acquired from combination of four specially designed cells in a sensing element.Contributed from the double-sided rough porous structure and specific surface morphology of nanocomposites,the piezoresistive sensor possesses high sensitivity of 12.1 kPa?1 within the range of 600 Pa and 0.68 kPa?1 in the regime exceeding 1 kPa for normal pressure,as well as 59.9 N?1 in the scope of<0.05 N and>2.3 N?1 in the region of<0.6 N for tangential force with ultra-low response time of 3.1 ms.In addition,multi-functional detection in human body monitoring was employed with single sensing cell and the sensor array was integrated into a robotic arm for objects grasping control,indicating the capacities in intelligent robot applications.

Knot-inspired optical sensors for slip detection and friction measurement in dexterous robotic manipulation

Friction plays a critical role in dexterous robotic manipulation.However,realizing friction sensing remains a challenge due to the difficulty in designing sensing structures to decouple multi-axial forces.Inspired by the topological mechanics of knots,we construct optical fiber knot(OFN)sensors for slip detection and friction measurement.By introducing localized self-contacts along the fiber,the knot structure enables anisotropic responses to normal and frictional forces.By employing OFNs and a change point detection algorithm,we demonstrate adaptive robotic grasping of slipping cups.We further develop a robotic finger that can measure tri-axial forces via a centrosymmetric architecture composed of five OFNs.Such a tactile finger allows a robotic hand to manipulate human tools dexterously.This work could provide a straightforward and cost-effective strategy for promoting adaptive grasping,dexterous manipulation,and human-robot interaction with tactile sensing.

An integrated approach for the optimization of wheel-rail contact force measurement systems

A comprehension of railway dynamic behavior implies the measure of wheel-rail contact forces which are affected by disturbances and errors that are often difficult to be quantified. In this study, a benchmark test case is proposed, and a bogie with a layout used on some European locomotives such as SIEMENS El90 is studied. In this layout, an additional shaft on which brake disks are installed is used to transmit the braking torque to the wheelset through a single-stage gearbox. Using a mixed approach based on finite element techniques and statistical considerations, it is possible to evaluate an optimal layout for strain gauge positioning and to optimize the measurement system to diminish the effects of noise and disturbance. We also conducted preliminary evaluations on the precision and frequency response of the proposed system.

Modeling of Energy Processes in Wheel-Rail Contacts Operating under Influence of Periodic Discontinuous Forces

In this paper we present new numerical simulation approaches for determining the energy processes under periodic conditions caused by time-discontinuous forces in the wheel-rail contacts. The main advantage of the presented method is the total elimination of frequency analysis, which in effect introduces important simplifications in the identification of the effects in the contact. The second important feature is the fact that the method is based on the analysis of appropriate loops on the energy phase plane leading to an easy estimation of the rail strength through the evaluation of the loop’s area. That model based simulation in the applied dynamics relies on advanced methods for model setup, robust and efficient numerical solution techniques and powerful simulation tools for practical applications. Fundamental properties of contact displacements of the rail surface have been considered on the basis of the newly established method. The contact zone between railway wheels and the rail surfaces made of bulk materials is perceived as strong enough to resist the normal (vertical) forces introduced by heavy loads and the dynamic response induced by track and wheel irregularities. The analysis is carried out for a wheel running on an elastic rail rested on sleepers arranged on completely rigid foundation. The equations of displacement motion are established through the application of the Lagrange equations approach. The established model of the wheel-rail contact dynamics has been applied to that same roll plane but with taking into account a nonlinear characteristic of the sleeper with respect to the ground. Attention then is focused completely on the modeling of the energy absorbed by the rail. The applied method employs the energy state variables as time functions leading to determine the susceptibility of a given contact on the strength induced by the rail roll.

二进制程序中House of Force漏洞利用技术分析

近年来,随着堆的漏洞不断被挖掘出来,Glibc也对自身的算法和代码进行了针对性地修补,采取了漏洞缓解、堆块尺寸检测等防御保护机制,但是仍然存在漏洞被利用的可能。首先对House of Force技术原理进行了分析,在此基础之上分析了针对该技术可利用漏洞的检测方法,包括生成崩溃输入、符号化种子输入、基于符号执行的漏洞检测和生成测试用例等过程,通过审计有漏洞的程序代码,发现该程序的漏洞点,并通过House of Force技术,编写脚本实现了漏洞的成功利用,最后指出了针对House of Force攻击的防御思路和方法。

Safety evaluation for railway vehicles using an improved indirect measurement method of wheel–rail forces

The wheel-rail force measurement is of great importance to the condition monitoring and safety evaluation of railway vehicles. In this paper, an improved indirect method for wheel-rail force measurement is proposed to evaluate the running safety of railway vehicles. In this method, the equilibrium equations of a suspended wheelset are derived and the wheel-rail forces are then be obtained from measured suspension and inertia forces. This indirect method avoids structural modifications to the wheelset and is applicable to the long-term operation of railway vehicles. As the wheel-rail lateral forces at two sides of the wheelset are difficult to separate, a new derailment criterion by combined use of wheelset derailment coefficient and wheel unloading ratio is proposed. To illustrate its effectiveness, the indirect method is applied to safety evaluation of rail- way vehicles in different scenarios, such as the cross wind safety of a high-speed train and the safety of a metro vehicle with hunting motions. Then, the feasibility of using this method to identify wheel-rail forces for low-floor light rail vehicles with resilient wheels is discussed. The values identified by this method is compared with that by Simpack simulation for the same low-floor vehicle, which shows a good coincidence between them in the time domain of the wheelset lateral force and the wheel-rail vertical force. In addition, use of the method to determine the high-frequency wheel-rail interaction forces reveals that it is possible to identify the high-frequency wheel-rail forces through the accelerations on the axle box.

Dynamic performance of six-axle locomotive subjected to asymmetric brake shoe forces

To research the influence of asymmetric brake shoe forces(ABSF)induced by braking failure on the dynamic performance of six-axle locomotive,the static equilibrium model of three-axle bogie and dynamic model for locomotive are established.The coupling vibration equations of axle hung motor and wheelset are derived.For the air braking,the influence mechanism of ABSF on the wheel-rail asymmetric motion and force characteristics are discussed.It can be found that if the ABSF is applied in the front wheelset,all the wheelsets move laterally in the same direction.Once the ABSF occurs in the middle or rear one,other wheelsets may move laterally towards the opposite direction.The motion amplitude and direction of all wheelsets strictly depend on the resultant moment of suspension yawing moment and brake shoe asymmetric moment.For the asymmetric braking,the free lateral gap of axle-box could increase the wheelset motion amplitude,but could not change the moving direction.In both the straight line and curve,the ABSF may lead to wheelset misaligning motion,intensify the wheel-rail lateral dynamic interaction and deteriorate wheel-rail contact state.Especially for the steering wheelsets,the asymmetric braking increases the wheelset attack angle significantly,which forms the worst braking condition.

Sweat detection theory and fluid driven methods: A review

In recent years, analyses of sweat have become more popular since it doesn't require invasive sampling procedures. Although blood still remains the golden standards in clinical, analyses of other common body fluids,such as sweat, have become increasingly important. Because the compositions of sweat and blood are osmotically related, the content of certain metabolites in sweat can directly reflect the disease. Sweat detection can be used as an alternative to blood detection and allows continuous monitoring. Increased development of wearable sensors makes it possible for continuous sweat detection. Here, this paper gave a review about the sweat detection methods, such as fluorescence sensing, electrochemical sensing and colorimetric sensing. The advantages and disadvantages of each method and their developing trend in sweat detection were summarized. Then, for the problem of continuous sweat sampling, three methods(capillary force, hydrogel osmotic pump, evaporationdriven micropump) were introduced through different structures of microfluidic chip, and the level of sweat collection and transport achieved by related research was demonstrated. This review aims to provide guidance for future research in sweat detection and stimulate further interest in continuous monitoring of sweat using microfluidic chip.

Dynamics analysis of vibration process in Particle Impact Noise Detection

Particle Impact Noise Detection (PIND) test is a reliability screening technique for hermetic device that is prescribed by MIL-PRF-39016E. Some test conditions are specified, although MIL-PRF-39016E did not specify how to obtain these condi- tions. This paper establishes the dynamics model of vibration process based on first order mass-spring system. The corresponding Simulink model is also established to simulate vibration process in optional input excitations. The response equations are derived in sinusoidal excitations and the required electromagnetic force waves are computed in order to obtain a given vibration and shock accelerations. Last, some simulation results are given.

Effect of a preload force on anchor system frequency

The interrelationship between preload forces and natural frequencies of anchors was obtained from the structure of an anchor and its mechanical characteristics. We established a numerical model for the dynamic analysis of a bolt support system taking into consideration the working surroundings of the anchor. The natural frequency distribution of the system under various preload forces of the anchor was analyzed with ANSYS. Our results show that each order of the system frequency varied with an increase in preload forces. A single order frequency decreased with an increase in the preload force. A preload force affected low-order frequencies more than high-order frequencies. We obtained a functional relationship by fitting preload forces and fundamental frequencies, which was in agreement with our theretical considerations. This study provides theoretical support for the detection of preload forces.

Yoctonewton force detection based on optically levitated oscillator

Optically levitated oscillators in high vacuum have excellent environmental isolation and low mass compared with conventional solid-state sensors,which makes them suitable for ultrasensitive force detection.The force resolution usually scales with the measurement bandwidth,which represents the ultimate detection capability of the system under ideal conditions if sufficient time is provided for measurement.However,considering the stability of a real system,a method based on the Allan variance is more reliable to evaluate the actual force detection performance.In this study,a levitated optomechanical system with a force detection sensitivity of 6.33±1.62 zN/Hz^(1/2)was demonstrated.And for the first time,the Allan variance was introduced to evaluate the system stability due to the force sensitivity fluctuations.The force detection resolution of 166.40±55.48 yN was reached at the optimal measurement time of 2751 s.The system demonstrated in this work has the best force detection performance in both sensitivity and resolution that have been reported so far for optically levitated particles.The reported high-sensitivity force detection system is an excellent candidate for the exploration of new physics such as fifth force searching,high-frequency gravitational waves detection,dark matter research and so on.

Spatial information recognizing of ocean eddies based on virtual force field and its application

A new approach to detecting ocean eddies automatically from remote sensing imageries based on the ocean eddy＇s eigen-pattern in remote sensing imagery and ＂force field-based shape extracting method＂ is proposed. First, the analysis on extracting eddies＇ edges from remote sensing imagery using conventional edge detection arithmetic operators is performed and returns digitized vector edge data as a result. Second, attraction forces and fusion forces between edge curves were analyzed and calculated based on the vector eddy edges. Thirdly, the virtual significant spatial patterns of eddy were detected automatically using iterative repetition followed by optimized rule. Finally, the spatial form auto-detection of different types of ocean eddies was done using satellite images. The study verified that this is an effective way to identify and detect the ocean eddy with a complex form.

基于LabVIEW的继电保护测试仪自动检测系统设计

针对现有的继电保护测试仪检测程序繁琐,自动化程度低,点对点调试效率低下等问题,提出基于LabVIEW的继电保护测试仪自动检测系统;系统硬件以STM32F407ZGT6为主控芯片研制了继电保护测试仪输出转换装置,自动控制测试仪与标准器连成试验回路,代替人工拆接线行为;系统软件以LabVIEW为开发平台,设计了仪器通信、自动检测、生成报告、强制选择测点等模块,实现了继电保护测试仪的全自动检测;通过对某型继电保护测试仪进行测试,结果表明该系统工作状态稳定,能够实现一键式全自动检测,用户界面友好,可以替代繁琐的人工检测方法,具有一定的工程应用前景。

北京地铁盾构隧道渗漏病害成因及对管片结构的影响研究

为揭示城市盾构隧道渗漏病害的形成机制,对北京地铁部分盾构隧道渗漏病害的主要类型、位置及程度进行统计分析。通过现场检测、地质雷达及内窥镜探测等手段,探究盾构隧道渗漏病害机制及成因,并通过数值模拟研究管片接缝渗漏时的地层变形规律及管片结构内力特征。研究表明:1)盾构管片接缝渗漏为主要的盾构隧道渗漏类型,占比超过60%,渗漏发生的位置集中在拱顶,以滴漏为主。2)盾构隧道渗漏水的主要内因是管片接缝处的不均匀变形,主要外因是地下水迅速升高导致存在渗漏隐患的隧道位于水位以下;同时,隧道周边地层更易形成富水体,增大了隧道渗漏病害的发生概率。3)盾构管片接缝处渗漏位置越靠近拱底,渗漏越严重,渗漏附近地层孔隙水压力消散的数值、最终达到稳定时的地表沉降越大。4)接缝局部渗漏导致的管片结构椭圆化变形较小,更易使结构出现向下且倾向渗漏点位方向的偏移;另外,渗漏位置变化相比渗漏程度对管片结构内力的影响大。

基于改进YOLOv5s的输电线路防外力破坏行为检测识别

电力系统的安全对于整个能源传输过程至关重要;针对输电线路下超大工程车辆和烟火为主要的外力破坏行为,对单阶段目标检测算法YOLOv5s进行改进,首先针对输电线路多雨雾烟尘等工作环境,引入限制对比度自适应直方图均衡算法CLAHE对图片进行去雾处理,提升图片对比度;针对检测目标距离较远的问题,在YOLOv5s网络的基础上添加CA注意力机制,提升了模型对目标的定位能力;将原网络中的最邻近差值采样方式替换为轻量级通用上采样算子CARAFE,更好地捕捉特征图的同时引入较小的参数量;最后在网络的特征融合层,使用具有通道混洗思想的GSConv卷积模块代替标准卷积模块,减少模型参数量,再利用slim_neck特征融合结构,强化目标关注度,达到减少模型参数量同时提升检测精度的效果;实验结果表明:改进后的YOLOv5s网络,mAP提升了4.4%,参数量减少了3.4%,权重模型内存减小了2.7%,证明了算法的有效性。

基于YOLO-2MCS的输电线路走廊隐患目标检测方法

输电线路在跨越高速铁路、高速公路和重要输电通道场景下易受到外力破坏,可能严重影响输电线路安全可靠运行。针对此问题,该文通过构建输电线路走廊隐患目标数据集,提出新模型YOLO-2MCS用于输电线路走廊隐患目标检测。使用混合数据增强策略对数据集进行有效扩充,以提高模型在复杂场景下的泛化性和鲁棒性;在EfficientRep骨干网络引入卷积注意力机制模块,有效提升模型对多尺度目标的检测能力;构建使用softplus激活函数的双向特征金字塔结构加强模型特征学习能力;在检测头使用SIoU损失函数进一步提升模型检测精度。实验结果表明,相较于原YOLOv6网络,该模型在0.5:0.95的严苛阈值下平均精度均值提升4.4%;将该模型与主流的检测模型FasterR-CNN、YOLOX、YOLOv5和YOLOv7分别进行对比评估,该模型的检测精度、检测速度、模型复杂度均获得最优性能,其平均检测速度高达约300帧/s,且内存仅为40.7 MB,同时满足在边缘计算设备上部署的要求。

高能脉冲磁弹仪器研制及其索力表征实验研究

针对在役桥梁钢索的索力检测需求,基于磁弹效应检测机理,首先,设计了便携式脉冲磁弹索力检测仪器,其可输出0~600 V电压可调、电流峰值高达60 A的高能尖峰脉冲信号,实现了对不同直径钢索的充分磁化,仪器主要包括上位机(含软件)、具有反馈控制的脉冲磁弹仪下位机和基于多芯线缆的改进磁弹传感器;其次,对公称直径17.8 mm的七芯钢绞线进行加载和卸载索力检测实验,实现了钢绞线的饱和磁化,磁弹传感器绕制效率是传统方法的8倍,分析了传统索力表征参量与索力之间的线性相关性;最后,在此基础上,提出一种索力表征参量--饱和磁导率μs,其线性拟合优度大于95%,且灵敏度(0.05)高于传统参量。通过对索力表征误差分析,该参量相较于传统参量在索力表征方面显示出较低的预测误差(3.7%)和迟滞误差(±1.54%)。该研究提出的参量可为脉冲磁弹法检测索力提供新的表征方法。