Modifed Pre-stretching Assembly Method for Cable-Driven Systems

Soft cable-driven systems have been employed in many assembled mechanisms, such as industrial robots, parallel kinematic mechanism machines, medical devices, and humaniform hands. A pre-stretching process is necessary to guarantee the quality of cable-driven systems during the assembly process. However, the stress relaxation of cables becomes a critical concern during long-term operation. This study investigates the effects of non-uniform deformation and long-term stress relaxation of the driven cables owing to moving parts in the system. A simple closed-loop cable-driven system is built and an alternating load is applied to it to replicate the operation of transmission cables. Under different experimental conditions, the cable tension is recorded and the boundary data are selected to be curve-fitted. Based on the fitted results, a formula is presented to estimate the stress relaxation of cables to evaluate the assembly performance. Further experimental results show that the stress relaxation is mainly caused by cable creep and the assembly procedure. To remove the influence of the assembly procedure, a modified pre-stretching assembly method based on the stress relaxation theory is proposed and verification experiments are performed. Finally, the assembly performance is optimized using a cable-driven surgical robot as an example. This paper proposes a dual stretching method instead of the pre-stretching method to assemble the cable-driven system to improve its performance and prolong its service life.

A smart assistance system for cable assembly by combining wearable augmented reality with portable visual inspection

Background Assembly guided by paper documents is the most widespread type used in the process of aircraft cable assembly.This process is very complicated and requires assembly workers with high-level skills.The technologies of wearable Augmented Reality(AR)and portable visual inspection can be exploited to improve the efficiency and the quality of cable assembly.Methods In this study,we propose a smart assistance system for cable assembly that combines wearable AR with portable visual inspection.Specifically,a portable visual device based on binocular vision and deep learning is developed to realize fast detection and recognition of cable brackets that are installed on aircraft airframes.A Convolutional Neural Network(CNN)is then developed to read the texts on cables after images are acquired from the camera of the wearable AR device.An authoring tool that was developed to create and manage the assembly process is proposed to realize visual guidance of the cable assembly process based on a wearable AR device.The system is applied to cable assembly on an aircraft bulkhead prototype.Results The results show that this system can recognize the number,types,and locations of brackets,and can correctly read the text of aircraft cables.The authoring tool can assist users who lack professional programming experience in establishing a process plan,i.e.,assembly outline based on AR for cable assembly.Conclusions The system can provide quick assembly guidance for aircraft cable with texts,images,and a 3 D model.It is beneficial for reducing the dependency on paper documents,labor intensity,and the error rate.

A review of cable layout design and assembly simulation in virtual environments

The layout and assembly of flexible cables play important roles in the design and development of complex electromechanical products.The rationality of cable layout design and the reliability of cable assembly greatly affect product quality.In this paper,we review the methods of cable layout design,cable assembly process planning,and cable assembly simulation.We first review research on flexible cable layout design(both interactive and automatic).Then,research on the cable assembly process planning,including cable assembly path and manipulation planning,is reviewed.Finally,cable assembly simulation is introduced,which includes general cable information,cable collision detection data,and cable assembly process modeling.Current problems and future research directions are summarized at the end of the paper.

Cable Harness Assembly Planning in Virtual Environment

Based on the analysis of characteristic of cable harness planning in virtual environment,a discrete control node modeling (DCNM) method of cable harness in virtual environment and the cable harness assembly routing technique based on it are proposed. DCNM converts a cable harness into continuous flexed line segments connected by a series of section center points,and the design can realize cable harness planning through controlling those control nodes. This method of cable harness routing in the virtual environment breaks the status that virtual assembly process planning is just suitable for the rigid components at present,and impulse the virtual assembly process planning to be more practical. Relation algorithms have been verified in a self-developed system named virtual cable harness assembly planning (VCHAP) system,and this VCHAP system has been applied in assembly process planning of aerospace-related products.

Integrated Virtual Assembly Process Planning System

Assembly process planning（APP） for complicated products is a time-consuming and difficult work with conventional method. Virtual assembly process planning（VAPP） provides engineers a new and efficiency way. Previous studies in VAPP are almost isolated and dispersive, and have not established a whole understanding and discussed key realization techniques of VAPP from a systemic and integrated view. The integrated virtual assembly process planning（IVAPP） system is a new virtual reality based engineering application, which offers engineers an efficient, intuitive, immersive and integrated method for assembly process planning in a virtual environment. Based on analysis the information integration requirement of VAPP, the architecture of IVAPP is proposed. Through the integrated structure, IVAPP system can realize information integration and workflow controlling. In order to mode/the assembly process in IVAPP, a hierarchical assembly task list（HATL） is presented, in which different assembly tasks for assembling different components are organized into a hierarchical list. A process-oriented automatic geometrical constraint recognition algorithm（AGCR） is proposed, so that geometrical constraints between components can be automatically recognized during the process of interactive assembling. At the same time, a progressive hierarchical reasoning（PHR） model is discussed. AGCR and PHR will greatly reduce the interactive workload. A discrete control node model（DCNM） for cable harness assembly planning in IVAPP is detailed. DCNM converts a cable harness into continuous flexed line segments connected by a series of section center points, and designs can realize cable harness planning through controlling those control nodes. Mechanical assemblies （such as transmission case and engine of automobile） are used to illustrate the feasibility of the proposed method and algorithms. The application of IVAPP system reveals advantages over the traditional assembly process planning method in shortening the time-consumed in assembly planning and in minimizing the handling difficulty, excessive reorientation and dissimilarity of assembly operations.

Developments and Prospects of Long-Span High-Speed Railway Bridge Technologies in China

With the rapid developments of the high-speed railway in China, a great number of long-span bridges have been constructed in order to cross rivers and gorges. At present, the longest main span of a constructed high-speed railway bridge is only 630 m. The main span of Hutong Yangtze River Bridge and of Wufengshan Yangtze River Bridge, which are under construction, will be much longer, at 1092 m each. In order to overcome the technical issues that originate from the extremely large dead loading and the relatively small structural stiffness of long-span high-speed railway bridges, many new technologies in bridge construction, design, materials, and so forth have been developed. This paper carefully reviews progress in the construction technologies of multi-function combined bridges in China, including com- bined highway and railway bridges and multi-track railway bridges. Innovations and practices regarding new types of bridge and composite bridge structures, such as bridges with three cable planes and three main trusses, inclined main trusses, slab-truss composite sections, and steel-concrete composite sections, are introduced. In addition, investigations into high-performance materials and integral fabrication and erection techniques for long-span railway bridges are summarized. At the end of the paper, prospects for the future development of long-span high-speed railwav bridges are provided.

斜拉桥长大节段组合式主梁悬臂施工技术研究

鲁巴跨海大桥主航道桥为双塔双索面混凝土斜拉桥,大桥主梁为π形混凝土组合式主梁,标准节段长10.2m、宽17.3m、中心高2.5m;主梁斜拉索锚固块及横向横梁为预制装配式构件,边主梁及桥面板为现浇混凝土构件,各主要构件通过横向预应力连为一体。以该桥主梁悬臂施工为工程背景,从质量控制、施工计划、施工成本3个方面对主梁2种施工方案进行对比,最终确定适合本桥主梁施工的挂篮方案,可有效降低临时结构自重对已浇筑节段混凝土产生的附加应力影响,降低工程造价;同时,通过对2~15号主梁节段采用新型桁架式牵索挂篮施工进行专项设计,解决了主梁节段长、自重大、预制装配式构件安装精度要求高、节段施工周期长的难题。

武汉青山长江公路大桥宽幅钢箱梁悬臂拼装横向线形匹配技术

武汉青山长江公路大桥主桥为主跨938 m的双塔双索面全飘浮体系斜拉桥,主跨整体式钢箱梁高4.5 m、全宽48 m,采用500 t架梁吊机分节段悬臂拼装架设。钢箱梁悬臂拼装时,架梁吊机站位节段、待架节段由于荷载及约束不同,横截面变形呈现出不同的趋势,线形匹配难度大。为解决该问题,主跨钢箱梁悬臂拼装时选择上、下游分体式架梁吊机,减少架梁吊机自重;经比选选择横桥向27.7 m间距的架梁吊机站位,减小了架梁吊机荷载对横向线形匹配的影响;通过设置顶压装置(由顶压牛腿、支承底座组成),在架梁吊机站位节段、待架节段钢箱梁边腹板处施加1500 kN顶压力,配合少量马板,一次加载完成对接口竖向变形匹配调整。施工后,钢箱梁横向线形匹配精度均满足要求。

模块化组合结构斜拉桥工业化智能建造关键技术

德州—上饶高速公路合肥—枞阳段孔城河特大桥主桥设计为(85+165)m大悬臂脊骨梁两跨独塔斜拉桥,采用模块化组合结构斜拉桥结构形式,主梁及索塔均设计成模块化标准单元件,为国内首次。为提高施工效率,推进桥梁工业化建造,针对模块化组合结构斜拉桥的特点,形成了模块化组合结构斜拉桥的工厂预制和现场施工建造技术,提出了基于自平衡架设的模块化组合结构斜拉桥快速安装技术。实践证明,与传统同规模独塔斜拉桥相比,该模块化组合结构斜拉桥施工工效显著提高,缩短工期约6个月,更有利于施工组织及质量管控。

新型装配式可调电缆支架的承载力特性试验研究

为解决圆形隧道内电缆支架安装困难的问题,提出一种新型的装配式可调电缆支架形式,并对该新型支架的承载力特性展开试验。研究不同角度工况下(0°、-45°和45°)支架的承载力特性分析,考虑支架长度、横担高度和宽度、斜撑直径和水平螺栓规格等对支架承载力特性的影响,研究其变形特征、荷载位移曲线特征和典型部位应变发展规律,同时开展新型支架承载力特性的非线性数值模拟分析,在此基础上提出该新型支架的承载力计算理论及设计方法。结果表明:支架的典型失效模式为斜撑整体失稳破坏,并伴随横担受压侧弯扭变形;支架的竖向刚度和极限承载力随调节角度的增加而下降,在45°工况下达到最小,而支架横向承载力特性受调节角度的影响较小,因此45°工况被视为最不利工况;新型电缆支架体系受力合理,具有足够的强度、刚度和稳定承载力,可应用于工程实践。

面向微小软排线装配的阵列触觉状态感知技术

针对微小软排线装配操作中器件体积小且存在视觉遮挡的问题,提出一种基于电容式阵列触觉传感器的机器人软排线装配状态感知技术。首先,对电容式三维触觉感知机理进行分析,并针对软排线装配的小尺寸空间感知需求,设计了一种基于垂直拓扑网状介质层的高灵敏阵列触觉传感器,实现微小软排线装配状态的高灵敏感知。其次,为突破布线复杂度与阵列扫描周期的限制,基于电容数字芯片拓展实现高动态三维阵列信息扫描系统的设计与微小软排线装配状态的高动态感知,并完成小型化电容式阵列触觉传感器的一体化制备。最后,搭建机器人软排线装配操作系统并实时采集和分析软排线装配过程中的阵列触觉信息特征,以验证所提出技术的准确性和有效性。

宜宾临港长江公铁大桥主桥超宽钢箱梁施工关键技术

宜宾临港长江公铁大桥主桥为主跨522 m的公铁同层双塔双索面钢箱梁斜拉桥,主桥钢箱梁宽63.9 m、高5 m,节段最大重量519.6 t。钢箱梁采用分部件加工、节段整体制作、场内预拼装方案制造。南岸钢箱梁采用边跨顶推+中跨单悬臂施工;北岸钢箱梁采用边跨存梁+双悬臂施工;中跨合龙段采用配切+顶推合龙。采用钢箱梁顶板与底板单元两拼工艺、钢箱梁锚固块体多工序组拼、预设反变形量的长线法总拼等制造技术,有效解决了超宽钢箱梁焊接变形量大的问题,大大提高了钢箱梁制造精度;南岸边跨钢箱梁利用中跨侧来梁进行顶推施工,解决了边跨运梁、吊梁施工难的问题,且避免了占用既有道路;北岸边跨钢箱梁利用枯水期预先存梁,解决了浅滩区钢箱梁施工受季节性水文影响大的问题,为双悬臂施工提供了先决条件;中跨合龙段采用现场配切+顶推施工,实现主跨钢箱梁精确合龙。

赤壁长江公路大桥主桥4号桥塔墩结合梁墩顶节段施工技术

赤壁长江公路大桥主桥为(90+240+720+240+90)m钢-混结合梁斜拉桥,主梁分为121个节段,由双边箱截面钢主梁、横梁、小纵梁等组成,4号桥塔墩墩顶钢梁共3个节段,考虑枯水期施工边跨侧滩地外露,采用浮吊拼装+墩顶拖拉法施工。桥塔墩设置墩旁支架辅助钢梁架设,墩旁支架采用简易支架,设计为分离直立柱结构,避免了传统斜立柱支架体系结构复杂且受限于围堰尺寸的影响;墩旁支架设置钢梁拖拉系统及钢梁姿态调节装置,以实现钢梁的拼装、纵移和姿态调整。墩顶钢梁利用浮吊在中跨侧依次拼装单节段钢梁杆件后向边跨侧分次拖拉,墩顶钢梁全部就位后,采用竖向调节装置通过“顶落梁”工艺精调钢梁高程和横向调节装置对钢梁横向偏位进行纠偏,保证墩顶节段姿态满足设计要求。借助主梁永久结构简化塔区临时约束设计,抵抗风荷载、施工不平衡荷载和不平衡索力造成的钢梁平动和转动,确保主梁悬臂节段施工安全。

高功率同轴电缆组件疲劳寿命分析及维护探讨

长线高功率同轴电缆组件主要应用于发射机和天线距离较远的系统,其敷设环境和高功率使用环境使其频繁处于热胀冷缩的状态,内导体由于受约束,会承受较大的内应力作用。由于内导体为整体,且束缚力较小,内应力会在内导体强度相对薄弱的位置积聚,促使该位置首先产生疲劳效应并最终发生故障,影响系统使用。文中就长线高功率同轴电缆组件长期工作后的失效进行分析,对长线高功率同轴电缆组件的使用寿命进行了理论分析及软件仿真,并通过试验验证了电缆组件内导体从出现开裂到发生故障所能承受的内应力冲击的极限次数,给出了不同长度高功率同轴电缆组件在不同加载功率下的寿命评估以及在寿命周期内的维护保障建议。

大跨梁桁组合结构高铁斜拉桥主梁施工方案比选

西十高铁汉江特大桥主桥为(67+70+73+420+73+70+67) m斜拉桥,主梁采用预应力混凝土箱梁和加劲钢桁架组成的梁桁组合结构,钢桁架下节点与预应力混凝土箱梁采用PBL键连接。边跨及塔区混凝土主梁采用支架现浇施工,为选择合理的中跨混凝土主梁施工方案,提出5 m节段悬浇施工、10 m节段悬浇施工、5 m节段预制悬拼施工3种方案,从建设条件、结构受力、行车动力性能、桥面线形、施工工期和投资等方面对3种方案进行对比。结果表明:5 m节段预制悬拼施工方案的工期最短,但投资最高,且受建设场地和运输条件的制约;节段悬浇施工技术成熟,技术风险及质量风险低,相比5 m节段,10 m节段悬浇施工方案虽然投资略高,但能够有效节省工期达5个月,且结构受力性能、行车安全性及舒适性、桥面线形均满足相关要求,在保证施工监控精度的前提下,成桥线形也在可控范围内,该桥最终选择10 m节段悬浇施工中跨混凝土主梁。

基于随机振动的线束装配拉力计算方法

为了提高飞机线束在机上装配的可靠性,确保用电设备之间正常的互联作用,设计一种检验线束装配牢固的拉力计算方法。通过3个正交方向上的随机振动试验获取线束的响应加速度特征,结合线束在振动过程中的受力模型提出一种基于加速度方均根值的拉力计算方法,并利用搭建的线束拉脱力试验平台,验证了该方法的可行性。

丹江口水库特大桥跨中无轴力连接装置施工关键技术

丹江口水库特大桥为主跨760 m的双塔双索面部分地锚式混合梁斜拉桥,边中跨比为0.2,采用梁塔分离、梁台固结的结构体系。根据主桥结构体系受力需要,主梁在跨中位置断开,设置跨中无轴力连接装置+伸缩装置构造。无轴力连接装置由导梁、外部大箱梁(H梁段和H′梁段)、竖向及横向支座系统组成,导梁长13.68 m。无轴力连接装置现场安装采用导梁跨中分段(2×6.84 m)拼装、外部大箱梁逐缝合龙的施工方法。首先在总拼场地进行无轴力连接装置工厂化预拼装,并安装竖向及横向支座系统,拼装完成后将导梁断开,回位至H梁段和H′梁段进行转运;然后现场吊装匹配连接H梁段,并将H梁段内部导梁向岸侧拖动固定;之后起吊H′梁段并与前置G梁段软连接;再进行H梁段和H′梁段导梁匹配连接;导梁匹配连接完成后进行H′梁段匹配连接;最后进行斜拉索放张、桥面吊机拆除。

面向复杂电子设备线缆数字化集成设计制造

文中针对传统三维建模软件用于线缆设计时效率低、设计一致性差的问题,开展了基于CATIA定制开发平台的线缆数字化集成设计平台研究。通过建立连接器、线材、辅料等的数据库和基于知识的线缆物料匹配性映射规则,开发了针对柔性线缆和半刚性线缆的线缆路径快速设计模块;通过快速编辑控制点实现线缆路径的高频次快速迭代优化;最后采用自动输出模块实现线缆图纸和制造数据的快速生成,并将成型数据自动导入线缆成型系统和基于混合现实的线缆引导装配系统,实现线缆从设计到制造的模型贯通。通过上述研究实现了线缆组件从路径规划到详细设计和制造一体化的集成应用,使线缆设计效率提升了3倍以上。

兰江特大桥双壁钢围堰施工关键技术研究

桥梁基础是整个桥梁施工建造过程中的重点并且存在相应的难度,论文以兰江特大桥为工程实例,阐述深水薄覆盖层河床双壁钢围堰施工工艺的优势。以圆形围堰结构为代表,从围堰设计、围堰拼装、平台搭设及下沉等复杂条件下探讨钢围堰的设计优化及施工。结果表明,双壁钢围堰加工及现场拼装可较好控制其质量,双壁钢围堰施工浮运和下沉施工技术对精度的控制较好,钢围堰接高及下沉技术避免了下沉过程中钢围堰受力过大的问题。所实施的施工关键技术减少了材料的浪费,降低成本,有效避免围堰位置偏移,避免污染河水,满足绿色施工要求。

陡峭山区大跨度钢管拱桥悬臂拼装抗风性能及稳定性分析

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