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。

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 Analysis of Steel Catenary Risers Based on a Plasticity Model

The most critical issue in the steel catenary riser design is to evaluate the fatigue damage in the touchdown zone accurately. Appropriate modeling of the riser-soil resistance in the touchdown zone can lead to significant cost reduction by optimizing design. This paper presents a plasticity model that can be applied to numerically simulate riser-soil interaction and evaluate dynamic responses and the fatigue damage of a steel catenary riser in the touchdown zone. Utilizing the model, numerous riser-soil elements are attached to the steel catenary riser finite elements, in which each simulates local foundation restraint along the riser touchdown zone. The riser-soil interaction plasticity model accounts for the behavior within an allowable combined loading surface. The model will be represented in this paper, allowing simple numerical implementation. More importantly, it can be incorporated within the structural analysis of a steel catenary riser with the finite element method. The applicability of the model is interpreted theoretically and the results are shown through application to an offshore 8.625 steel catenary riser example. The fatigue analysis results of the liner elastic riser-soil model are also shown. According to the comparison results of the two models, the fatigue life analysis results of the plasticity framework are reasonable and the horizontal effects of the riser-soil interaction can be included.

Steel Catenary Riser Fatigue Life Prediction Using Linearized Hydrodynamic Models

Steel catenary risers, (SCR) usually installed between seabed wellhead and floating platform are subjected to vortex shedding. These impose direct forces, hence cyclic stresses, and fatigue damage on the SCR. Riser failure has both economic and environmental consequences;hence the design life is usually greater than the field life, which is significantly reduced by vortex induced vibration (VIV). In this study, SCR and metOcean data from a field in Offshore Nigeria were substituted into linearized hydrodynamic models for simulations. The results showed that the hang off and touchdown regions were most susceptible to fatigue failure. Further analysis using Miner-Palm green models revealed that the fatigue life reduced from a design value of 20-years to 17.04-years, shortened by 2.96-years due to VIV. Furthermore, a maximum wave load of 5.154 kN was observed. The wave loads results corroborated with those obtained from finite element Orca Flex software, yielding a correlation coefficient of 0.975.

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.

Nonlinear Analysis of Flexible and Steel Catenary Risers with Internal Flow and Seabed Interaction Effects

Flexible risers and steel catenary risers often provide unique riser solutions for today’s deepwater field development. Accurate analysis of these slender structures, in which there are high-speed HP/HT internal flows, is critical to ensure personnel and asset safety. In this study, a special global coordinate-based FEM rod model was adopted to identify and quantify the effects of internal flow and hydrostatic pressure on both flexible and deepwater steel catenary risers, with emphasis on the latter. By incorporating internal flow induced forces into the model, it was found that the internal flow contributes a new term to the effective tension expression. For flexible risers in shallow water, internal flow and hydrostatic pressure made virtually no change to effective tension by merely altering the riser wall tension. In deep water the internal pressure wielded a dominant role in governing the riser effective tension and furthering the static configuration, while the effect of inflow velocity was negligible. With respect to the riser seabed interaction, both the seabed support and friction effect were considered, with the former modeled by a nonlinear quadratic spring, allowing for a consistent derivation of the tangent stiffness matrix. The presented application examples show that the nonlinear quadratic spring is, when using the catenary solution as an initial static profile, an efficient way to model the quasi-Winkler-type elastic seabed foundation in this finite element scheme.

Experimental and Computational Investigations on Severe Slugging in A Catenary Riser

Severe slugging can occur in a pipeline-riser system at relatively low liquid and gas flow rates during gas-oil transportation, possibly causing unexpected damage to the production facilities. Experiments with air and water are conducted in a horizontal and downward inclined pipeline followed by a catenary riser in order to investigate the mechanism and characteristics of severe slugging. A theoretical model is introduced to compare with the experiments. The results show that the formation mechanism of severe slugging in a catenary riser is different from that in a vertical riser due to the riser geometry and five flow patterns are obtained and analyzed. A gas-liquid mixture slug stage is observed at the beginning of one cycle of severe slugging, which is seldom noticed in previous studies. Based on both experiments and computations, the time period and variation of pressure amplitude of severe slugging are found closely related to the superficial gas velocity, implying that the gas velocity significantly influences the flow patterns in our experiments. Moreover, good agreements between the experimental data and the numerical results are shown in the stability curve and flow regime map, which can be a possible reference for design in an offshore oil-production system.

电气化铁路弓网系统摩擦磨损性能研究进展

针对电气化铁路弓网正常和异常状态的接触副,分析受电弓滑板磨耗周期内的摩擦磨损性能差异性,特别是受电弓滑板的磨耗率和磨耗型面的差异性,包括:发生异常磨损时受电弓滑板磨损率数倍甚至数十倍的增长差异,以及局部偏磨、波浪型磨耗和贯穿性凹坑等磨耗型面差异;着重归纳不同弓网系统载流摩擦磨损试验台的特点及异同,总结磨耗检测接触式测量方法与非接触式测量方法的优劣;分析弓网系统结构及参数、列车运行参数、弓网系统载流参数及外界环境等因素的影响,归纳总结弓网载流摩擦磨损特性的演变规律.在此基础上,综合分析弓网系统磨耗机理分析模型和数据拟合模型的研究现状和进展,并给出弓网系统载流摩擦磨损性能在后续研究中所需重点关注的研究方向和发展趋势,包括:弓网摩擦副的真实服役工况在实验室条件下的等效模拟;弓网磨耗性能的在线高精度检测;复杂气候条件及多物理场耦合作用下弓网磨耗性能的仿真和优化;结合大数据和智能算法的弓网磨耗预测,以及智能运维策略和全生命周期的能力保持技术等.

城市轨道交通车体垂向振动对弓网受流性能的影响

[目的]既有对接触网系统动力学仿真的研究大多基于受电弓底座仅有纵向自由度的假设,忽略了轮轨激励引起的车体垂向振动对弓网受流性能的影响,需要将车辆-受电弓-接触网(以下简称“车-弓-网”)作为一个整体予以研究。[方法]分别建立了刚性接触网、柔性接触网两种接触网类型下的弓网耦合动力学模型及车-弓-网多体动力学模型。在案例线路上进行了弓网动态受流试验,对所建的刚性接触网车-弓-网多体动力学模型的计算结果进行了可行性验证。基于列车运行速度为80 km/h、90 km/h、100 km/h、110 km/h及120 km/h五种速度工况,选取了其中两种速度工况对刚性接触网受电弓绝缘子底座处的垂向动态响应进行了分析,并在五种速度工况下分别对两种接触网类型下弓网模型、车-弓-网模型的各动态响应参数进行了对比分析。[结果及结论]所建车-弓-网多体动力学模型的模拟计算结果是合理的。车体振动会对弓网受流性能产生一定影响:柔性接触网下车体垂向振动对弓网受流性能影响很小,可不予考虑;刚性接触网下,与未考虑车体垂向振动的弓网模型相比,考虑了车体垂向振动的车-弓-网模型计算得到的弓网接触压力统计最小值、弓头最大抬升位移均随列车运行速度的增加而增加,弓网接触压力统计最小值变化率的最大值为24.7%,弓头最大抬升位移变化率的最大值为4.2%。

基于OrcaFlex的钢悬链立管疲劳损伤预报

涡激振动是钢悬链立管疲劳损伤的重要诱导因素之一,因此涡激振动分析在钢悬链立管设计中占据重要地位。OrcaFlex在海洋工程领域功能强大、应用广泛,能够提供两种涡激振动疲劳损伤预报方法,分别是基于模态叠加法的频域预报方法和基于Iwan-Blevins尾流振子模型的时域预报方法。OrcaFlex的涡激振动时域预报模型只考虑了横流向涡激振动造成的疲劳损伤,基于OrcaFlex的时域预报方法开发了双自由度涡激振动尾流振子模型的接口,考虑了浮式平台运动对钢悬链立管的涡激振动激励作用,实现了钢悬链立管双自由度涡激振动疲劳损伤预报。

基于BIM参数化建模的接触网吊弦计算在京张高速铁路的应用研究

随着我国电气化铁路建设的快速增长以及信息化、智能化要求的不断提高,工程设计人员对接触网悬挂的安装要求越来越高,其中吊弦长度计算是接触网悬挂的重中之重。针对基于BIM参数化建模的高速铁路接触网弹性链型悬挂吊弦长度的计算影响因素进行分析,从跨距、第一吊弦距离、结构高度、线材参数、曲线要素等影响吊弦长度计算的关键因素进行数据分析,找出影响吊弦长度的关键因素及变化规律,明确统一的现场测量标准,并通过BIM轻量化平台进行参数化应用,将测量、计算和BIM参数化3部分形成闭环控制,为现场测量和计算提供依据,有效提高吊弦计算的精度,实现施工安装模拟由二维到三维的转变,各环节间数据互联互通,最终为形成高品质的弓网关系提供坚实的基础。

基于蝴蝶结模型的高铁接触网安全风险管理

接触网设备是高铁基础设施的关键组成部分,对其进行有效的风险管理对于保障列车的安全运行具有重要意义。既有的接触网安全风险管理大多以纯文本形式呈现,不生动形象,难以被职工尤其是老职工所接纳。基于蝴蝶结模型的风险管理模式具备高度可视化、实操性强等特点,掌握蝴蝶结模型原理,以高铁整体吊弦损伤风险管理为参考样例,调研和分析其损伤原因,构造其安全屏障,进而搭建蝴蝶结模型,通过这样的方式,以期为构建接触网安全风险管理新模式提供参考。

浅海电缆弯曲刚度对电缆受力影响的试验研究

海缆敷设张力的确定是保证敷设工程质量的重要环节,目前对海缆张力的计算很少考虑弯曲刚度的影响。开展不同电缆弯曲刚度对电缆受力影响的水槽模型试验研究。研究结果表明,弯曲刚度对海缆顶部的水平张力影响不大,其主要影响的是海缆水中的姿态。

基于神经网络融合模型的铁路接触网异物智能检测

针对影响铁路接触网正常运行的异物问题,提出了一种基于神经网络融合模型的铁路接触网异物智能检测模型。以Faster R-CNN框架为基础,增加特征金字塔结构以学习图像不同尺度的特征;针对不同异物类型,将其分为鸟巢和轻质漂浮物,并运用ResNet50和ResNet101作为骨架网络,分别针对具有单一特征的鸟巢和特征复杂多变的轻质漂浮物进行识别;融合2个网络的识别框,得到精确的识别结果。对比实验表明,该模型的检测结果优于常规目标检测方法,可有效降低铁路接触网异物检测的人工成本,为铁路接触网的稳定运营提供了可行的解决方案。

基于马尔科夫链模型的特高压输电线路工频电磁场监测方法

针对当前方法的特高压输电线路电磁监测误差大问题,设计基于马尔科夫链模型的工频电磁场监测方法。结合特高压输电线路环境和最大导线弧垂点布置线路工频电磁场测点,然后采用超限学习机网络模型设计传感数据修正技术,去除数据中干扰信息,并引入有限长模拟线电荷法以及毕奥-萨瓦定律计算输电导线三维电磁场分布,最后运用马尔科夫链模型定义工频电磁场状态转移矩阵,得到准确的监测结果。实验结果显示:所提方法的电场监测相对误差降低了21%、25%,磁场监测相对误差降低了0.24%、0.27%。

基于公铁两用自行走车的电气化铁路限界检测装置设计

为解决铁路接触网施工人工复核测量带来的人工成本高、体力劳动繁重、检测效率低、测量精度差的痛点问题,设计了一种搭载三维激光雷达、接触网几何参数测量等模块的基于公铁两用自行走车的电气化铁路限界检测装置。实现了多控制方式、多施工环境下,铁路沿线接触网相关装备各项限界参数的实时测量、与理论值的复核分析以及沿线装备三维建模。该装置提升了测量效率、精度及限界参数可视化效果,可减少测量人员60%以上,提高整体测量效率70%。

弓网滑动电接触电磁热力耦合效应研究进展

为电力机车提供牵引动力的受电弓滑板与接触网导线是典型的滑动电接触摩擦副,二者在工作中存在电、磁、热、力多场耦合效应,复杂的多场耦合作用将影响弓网的受流质量和摩擦磨损性能,开展电气化铁路弓网接触多物理场耦合效应研究,对降低弓网运行维护成本,提高受电弓滑板和接触网导线使用寿命等具有重要意义。该文重点归纳总结了近些年来弓网系统在电、磁、热、力多场效应下的相关研究进展。结合列车实际运行工况,综述了弓网接触电阻、电弧、接触温度、电磁力和压力载荷等因素对弓网载流摩擦磨损性能的影响规律,针对多物理场作用下研究中存在的问题与不足,提出进一步研究和完善的意见。在此基础上,从提高弓网滑动电接触性能、保障列车安全稳定运行角度,采用弓网接触电阻、燃弧率及接触温度对电接触性能的评价进行阐述和探讨,以期对弓网电接触行为进行合理预测与评估,为进一步研究弓网滑动电接触多场耦合效应提供参考。

考虑接触网-钢轨耦合关系及再生制动能量的新型电缆贯通供电系统电气特性

针对新型电缆贯通供电系统模型未准确反映接触网与钢轨之间的耦合关系、未考虑再生制动能量利用及环网加单边供电方案等问题,采用电流控制的电压源解耦方法反映接触网和钢轨之间的耦合关系,建立基于二端口网络的新型电缆贯通供电系统模型;在计算系统牵引网阻抗、电压损失及馈线电流的基础上,结合实际线路数据,提出3种电缆贯通供电方案,在不同运行工况下仿真分析各供电方案下系统的电气特性,并考虑再生能量利用设计牵引变压器容量,以达到降低牵引变压器容量和运营维护费用的目的。结果表明:新型电缆贯通供电系统在各种供电方案下的再生能量利用率均较高,普遍达到90%以上;在相同牵引变压器数目下,环网加单边供电方案电压损失、牵引网损耗等性能指标均优于单纯的环网结构;再生制动能量能够作为牵引变压器容量设计的参考因素。

强电流下弓网滑动电接触磨损特性分析和建模

针对电气化铁路弓网滑动电接触的摩擦磨损问题,采用自制的弓网滑动电接触实验机,研究了受电弓滑板的磨损特性,获得了磨损率随接触电流、滑动速度、压力波动幅值及其波动频率的变化规律。以此为基础,利用Archard磨损模型,通过无载流磨损、压力载荷波动磨损、载流摩擦下的总磨损率与纯机械摩擦下磨损率的比例关系研究,构造出磨损率的数学表达式。将通用全局优化算法和麦夸特算法相结合,对磨损率模型的参数辨识寻优,并证明了磨损率模型的准确性。从磨损率的定性分析转化为磨损率的定量分析,对进一步研究弓网系统的磨损有一定的指导意义。

基于因果贝叶斯网络的接触网风险评估模型研究

针对接触网建设阶段风险管控研究相对薄弱的问题,在充分研析接触网施工过程风险因素的基础上,判断风险因素间因果关系,建立接触网建设阶段风险评估模型,从因果逻辑视角分析接触网建设阶段风险。首先,从建设阶段、参建部门及建设要素3个维度分析接触网建设过程风险因素的外生变量与内生变量;然后,利用结构方程式描述变量之间的因果关系,建立多层次接触网风险结构因果模型网络关系分析图,并引入专家评议确定外生变量的先验概率与内生变量的条件概率,构建基于贝叶斯网络的接触网建设阶段风险评估模型;最后,通过贝叶斯网络敏感性分析和逆向推理分析找到接触网建设风险的事故最大因果链以及重要风险节点,在施工过程薄弱环节制定相应的风险预防与控制措施,降低风险发生的概率及影响,保证接触网工程按期交付以及运维阶段的检修效率。研究结果表明:在接触网建设阶段,风险发生的概率为0.6,所构建的接触网建设过程风险评估模型中有敏感性较高的节点4个,事故致因链5条。在假设接触网风险发生的条件下,逆向推理的结果显示预装配阶段和安装阶段的后验概率较高,分别为0.74和0.67。通过严格执行提出的风险控制措施,有助于提升接触网建设效率,降低运维阶段的维护成本。