Random vortex induced vibration response of suspended flexible cable to fluctuating wind

A popular dynamical model for the vortex induced vibration(VIV)of a suspended flexible cable consists of two coupled equations.The first equation is a partial differential equation governing the cable vibration.The second equation is a wake oscillator that models the lift coefficient acting on the cable.The incoming wind acting on the cable is usually assumed as the uniform wind with a constant velocity,which makes the VIV model be a deterministic one.In the real world,however,the wind velocity is randomly fluctuant and makes the VIV of a suspended flexible cable be treated as a random vibration.In the present paper,the deterministic VIV model of a suspended flexible cable is modified to a random one by introducing the fluctuating wind.Using the normal mode approach,the random VIV system is transformed into an infinite-dimensional modal vibration system.Depending on whether a modal frequency is close to the aeolian frequency or not,the corresponding modal vibration is characterized as a resonant vibration or a non-resonant vibration.By applying the stochastic averaging method of quasi Hamiltonian systems,the response of modal vibrations in the case of resonance or non-resonance can be analytically predicted.Then,the random VIV response of the whole cable can be approximately calculated by superimposing the response of the most influential modal vibrations.Some numerical simulation results confirm the obtained analytical results.It is found that the intensity of the resonant modal vibration is much higher than that of the non-resonant modal vibration.Thus,the analytical results of the resonant modal vibration can be used as a rough estimation for the whole response of a cable.

Analysis and Experimental Study on the Friction Force at the Binding Point of Flexible Cable on Satellite

Mainly for the problem that the friction force generated by the existing process of bind-ing,fixing and fastening the flexible cable on the satellite is unknown,the friction force analysis and experimental research on the binding point of the flexible cable are carried out.The equivalent model of the cable bundle bound by nylon cable ties is established,the force on the binding point is analyzed,and the empirical formula for calculating the friction force at the binding point is estab-lished.The formula shows that the friction force is related to the cable bundle diameter,the number of winding cycles of silicone rubber tape,the width of nylon cable ties,and the binding force.The friction force tests of the cable diameter of 5.06 mm,8.02 mm,24.02 mm,38.04 mm under different winding turns of tape were carried out,which was compared with the theoretical calculation value.It is concluded that the calculation accuracy of the theoretical model is more than 95%,which can estimate the actual friction force value accurately.This provides a reference and basis for the theoretical and experimental research on the friction force of the flexible cable binding point on satellite.

Study on the Configuration of Towed Flexible Cables

Based on the fundamental equation of flexible cable dynamics for a towed system, an easily solved mathematical model is set up in this paper by means of appropriate simplification. Several regular patterns of spatial motion of towed flexible cables in water are obtained through numerical simulation with the finite difference method, and then modification and verification by trial results at sea. A technical support is provided for the towing ship to maneuver properly when a flexible cable is towed. Furthermore, the relations between two towed flexible cables, which are towed simultaneously by a ship, are investigated. The results show that the ship towing two flexible cables is safe under the suggested arrangement of two winches for the towing system, and the coiling/uncoiling sequences of the cables as well as the suggested way of maneuvering.

An Overview of Structural Design,Analysis and Common Monitoring Technologies for Floating Platform and Flexible Cable and Riser

Offshore oil and gas development plays an important part in the global energy sector.Offshore platforms and flexible pipes are the key equipments in the whole offshore oil and gas development system.Because of the randomness and uncertainty of wave and current loads in the ocean environment,the structural design and mechanical analysis of the marine equipment can be highly complicated.Therefore,this paper reviews the recent works of the theoretical model,numerical simulation,and experimental test in three research areas:hydrodynamic analysis of offshore platforms,structural mechanics analysis of flexible pipe and cable,and monitoring technology of offshore floating structures under marine loads.By analyzing their main research methods and key technical difficulties,this paper provides theoretical basis and technical support for the reliability engineering application of offshore platforms and flexible pipelines.Also,China is relatively backward in the design of marine floating platform,the design,analysis and testing of flexible pipeline and cable,as well as the marine equipment prototype monitoring technology research.Calling for breakthroughs at the earliest possible stage in the above fields,prime research should be focused on and strategic planning should be made to deal with“key areas and stranglehold problems”.It is of great significance for the development of China's deep-sea energy and resource development of independent technology and on time to achieve the“carbon peak”national strategic objectives.

DYNAMIC MODELING AND SIMULATION OF FLEXIBLE CABLE WITH LARGE SAG

Discrete model of flexible cable with large sag is established by using multiple rigid body-spherical hinge model, and dynamic equation of that discrete model is derived according to dynamics theory of multiple rigid body system. Displacement and velocity of system are revised to eliminate violation phenomenon of the differential-algebra equation in numerical simulation based of the theory of generalized inverse of matrices. Numerical simulation proves the validity of our method.

STUDY ON MINE FIRE-RESISTANT OPTICAL FIBER CABLE KL5004

This paper introduces a new-developed mine fire-resistant optical fiber cable (OFC)KL5004,its structural characteristics, main feature, the theory about fire resistance and its application in high output and efficiency mine.

Flexible Bio-tensegrity Manipulator with Multi-degree of Freedom and Variable Structure

Conventional manipulators with rigid structures and sti ness actuators have poor flexibility,limited obstacle avoidance capability,and constrained workspace.Some developed flexible or soft manipulators in recent years have the characteristics of infinite degrees of freedom,high flexibility,environmental adaptability,and extended manipulation capability.However,these existing manipulators still cannot achieve the shrinking motion and independent control of specified segments like the animals,which hinders their applications.In this paper,a flexible bio-tensegrity manipulator,inspired by the longitudinal and transversal muscles of octopus tentacles,was proposed to mimic the shrinking behavior and achieve the variable motion patterns of each segment.Such proposed manipulator uses the elastic spring as the backbone,which is driven by four cables and has one variable structure mechanism in each segment to achieve the independent control of each segment.The variable structure mechanism innovatively contains seven lock-release states to independently control the bending and shrinking motion of each segment.After the kinematic modeling and analysis,one prototype of such bionic flexible manipulator was built and the open-loop control method was proposed.Some proof-of-concept experiments,including the shrinking motion,bending motion,and variable structure motion,were carried out by controlling the length of four cables and changing the lock-release states of the variable structure mechanism,which validate the feasibility and validity of our proposed prototype.Meanwhile,the experimental results show the flexible manipulator can accomplish the bending and shrinking motion with the relative error less than 6.8%through the simple independent control of each segment using the variable structure mechanism.This proposed manipulator has the features of controllable degree-of-freedom in each segment,which extend their environmental adaptability,and manipulation capability.

Cosserat Dynamic Modeling and Simulation of Mobile Cable on Satellite

Mainly for the problems that the configuration of the mobile cable on the satellite is very easy to change,the motion trajectory and dynamic characteristics of the cable can not be accu-rately predicted,which affects the laying quality seriously,the dynamic modeling and simulation of mobile cable on the satellite are carried out.On the basis of referring to the previous papers,the existing mathematical model is improved.The equations of the base vector of the cable section principal axis coordinate system with respect to the arc coordinate s,the distribution force of cable balance equation,the matrix expression of the base vector after the rotation motion transformation in the section principal axis coordinate system,the angular velocity of cable,the section elastic strain and velocity calculation equations are given,and the Cosserat dynamic modeling of the mobile cable is established.Finally,the dynamic simulation model of the mobile cable assembly of the kinematic mechanism is established,and the changes of the force and torque on the cable con-straint end are obtained,which provides a reference for the dynamic modeling and simulation of the mobile cable on satellite.

海洋复合管缆设计关键技术与挑战

海洋复合管缆是海洋资源开发的重要装备之一,广泛应用于海上油气开发、深海采矿、海上风电等。海洋复合管缆具有弯曲性能好、质量轻、强度高、耐腐蚀和耐高低温等优点,能满足海洋资源开发不断向深水进发的需求。然而,海洋复合管缆相较于传统均质管道结构设计更加复杂,力学特性和使用寿命的准确预测更加困难。结合相关规范对海洋复合管缆设计的常规方法进行介绍,并归纳总结海洋复合管缆设计中需要进一步考虑的结构优化技术、材料非线性问题、几何非线性问题和界面非线性问题(界面强度、界面疲劳、界面摩擦)等关键技术。研究结果可为海洋复合管缆的设计研究提供指导。

双层索系柔性光伏支架结构受力性能研究

目的研究双层索系柔性光伏支架结构在风荷载作用下的静力性能与动力响应。方法采用ABAQUS有限元软件开展双层索系柔性光伏支架结构的静力性能、动力特性、动力响应和风振系数分析,探究了跨度、横向连接系间距以及挠度限值等影响因素对支架结构受力性能的影响。结果结构的风振响应随着跨度的增加而增大;结构跨中挠度及上层索索力随横向连接系间距的增大而增大;增大上层索预应力可以减小结构的动力响应,而下层索预应力过大会导致结构的风振响应增大。结论通过研究给出了双层索系柔性光伏支架结构的风振系数取值范围以及上、下层索的初始预拉力设置建议,可以为其结构抗风设计提供参考。

多排大跨度光伏柔性索桁架结构设计的差异化

山地光伏电站建设的发展势头迅猛,光伏柔性索桁架结构应运而生。这种结构在原有单层悬索的柔性支架基础上增加了防风结构,能更好地适应复杂地形。但索桁架结构和受力更为复杂,目前缺少统一的设计规范,为研究光伏柔性索桁架两种典型结构的结构性能,采用有限元的方法对不同拱形矢高多排大跨度光伏柔性索桁架进行仿真分析,从结构模态、风振系数以及极限工况多角度开展研究。结果表明,增大防风索拱形的矢高,有利于抑制倒拱和正拱两种结构的风致振动;分析四种极限工况,矢高每增加100 mm,倒拱Z向位移平均减小率最小为10.07%,正拱最小为2.79%。同时倒拱结构的挠度变形和轴力等力学性能优于正拱结构,更具市场应用价值。

一种柔性太阳电池阵电传输解决方案

柔性太阳电池阵由于其质量轻、收拢体积小、可重复展收等特点,具有极大的创新性和前瞻性,是目前和今后极具竞争力的太阳电池阵构型。针对目前柔性太阳电池阵收拢和折叠特性,传统电缆束和电连接器已经不再适用,急需寻找一种新型薄型结构电传输解决方案。提出了一种柔性电缆电传输方案,这种柔性电缆具有传输功率大、质量轻、收拢体积小、可折叠等特点,非常适合作为大面积、大功率的柔性太阳阵电传输的主方式,可为未来新型太阳电池阵的设计提供新方向、设计参考和技术支撑。

基于柔性传感器的绳驱动连续体机器人反馈控制

鉴于绳驱动连续体机器人独特的柔顺性使得其骨架变形难以通过传统的刚性传感器测量,另一方面,基于分段常曲率假设建立的运动学模型开环控制存在位置精度低的问题。本文以模块化设计的绳驱动连续体机器人为研究对象,利用了一种弹性磁电应变传感器并建立了多元回归模型实现机器人形状感知。通过一种运动空间映射方法实现了机器人柔性臂在三维空间内的闭环反馈控制。最终搭建了机器人样机平台并进行实验验证。结果有力地证明了基于柔性传感器的反馈控制方法的可行性和准确性。

单电机线驱动多指柔性外骨骼机械手设计

为使外骨骼机械手的作用更加柔顺、灵活、轻量和低成本,设计了一款基于柔索传递驱动的外骨骼手,整手有10条驱动线,只采用了1台伺服电机做动力源(单驱),通过传动结构和电磁线圈的通断产生的止停作用,使单一动力源的运动输出能合理分配给5根手指的驱动线,并实时控制每根手指上的两条驱动线,生成符合要求的行程运动,缩减了外骨骼手动力装置的体积和重量,降低了生产成本。

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。

柔性光伏支架结构布置形式分析研究

对包括索布置、梁布置、柱布置以及各类支撑布置的各种柔性光伏支架形式进行归类整理,将柔性支架结构布置形式划分为索—梁形式以及索—柱形式。利用有限元模型对比索—梁形式、索—柱形式以及联合布置形式的经济合理性,并进行跨度影响性分析。结果表明,索—柱形式在经济上优于索—梁形式;当布置为小跨度时,只设置2道主索即能满足应力和变形的要求,当跨度较大时需要设置防风体系;连续多跨布置较单跨土地利用率高且经济性优。

绳驱动刚-柔-软耦合机器人的设计与分析

狭窄空间、复杂结构环境等应用场景要求机器人具有较高的柔顺性、灵活性、适应性、安全性,传统机器人难以满足这些要求。对此,设计了一种绳驱动刚-柔-软耦合机器人。这一机器人由连续型关节和刚性离散型关节串联而成,既具有连续型机器人的柔顺性和适应性,又通过末端离散型关节弥补连续型关节转弯半径大等不足,提高机器人末端灵活性。这一机器人具有刚-柔-软耦合、串并联混合的特点,机器人逆运动学分析较为复杂,难以获得解析解。对此,提出一种基于复合形优化算法的逆运动学求解方法,具有较高的计算效率。在运动学建模分析的基础上,对这一机器人的工作空间进行了分析。

冲喷式柔性管缆挖沟机在海底管缆铺设挖沟施工中的应用

深水水下管缆的铺设是开发深水油气资源的关键施工作业项目。深水水下挖沟作业具有技术难度大、施工复杂、投资巨大等特点。在深水海域油气开发工程中冲喷式柔性管缆挖沟机应用广泛,因此对其产品性能、实际深水功能测试、挖沟作业工序、挖沟沟型、挖沟效果等关键技术问题进行分析,经过实践验证,该设备能够独立完成千米级深水域水下挖沟施工。

某型号导引头电子组件柔性互连技术研究

导引头系列产品中,非规则线缆的广泛应用、大批量需求及纯手工制作的生产特点,已满足不了导引头生产装配的自动化发展需求。针对导引头系列产品的小型化、轻量化、集成化发展趋势,需要一种新型电气互连方式来解决产品生产过程中非规则线缆制作这一瓶颈问题。利用电子组件柔性互连技术,采用刚柔结合印制板制造形式,实现了电信号在导引头内的稳定传输与可靠连接,经过抗载验证,满足了导引头抗载应用需求,达到了导引头非规则线缆自动化、批量化制作的目的。

消防配电线路在受火条件下的可靠性研究

通过5次燃烧试验,将普通电力电缆、相同云母带不同层数绝缘的有机绝缘类耐火电缆、氧化镁绝缘耐火电缆、柔性矿物绝缘类耐火电缆和同结构不同规格型号的电缆等在火灾升温条件下对比试验后的线路完整性,分析、探讨建筑物中消防设备供电线路在带实载受火条件下电缆类型与供电时间的规律及运行数据。