A hardening load transfer function for rock bolts and its calibration using distributed fiber optic sensing

Confinement of rock bolts by the surrounding rock formation has long been recognized as a positive contributor to the pull-out behavior,yet only a few experimental works and analytical models have been reported,most of which are based on the global rock bolt response evaluated in pull-out tests.This paper presents a laboratory experimental setup aiming to capture the rock formation effect,while using distributed fiber optic sensing to quantify the effect of the confinement and the reinforcement pull-out behavior on a more local level.It is shown that the behavior along the sample itself varies,with certain points exhibiting stress drops with crack formation.Some edge effects related to the kinematic freedom of the grout to dilate are also observed.Regardless,it was found that the mid-level response is quite similar to the average response along the sample.The ability to characterize the variation of the response along the sample is one of the many advantages high-resolution fiber optic sensing allows in such investigations.The paper also offers a plasticity-based hardening load transfer function,representing a"slice"of the anchor.The paper describes in detail the development of the model and the calibration/determination of its parameters.The suggested model captures well the coupled behavior in which the pull-out process leads to an increase in the confining stress due to dilative behavior.

Transfer function measurement for the SSRF SRF system

A digital transfer function measurement system has been embedded in the low-level radio frequency (LLRF) system of the storage ring of the Shanghai Synchrotron Radiation Facility. The measurement results indicate that the decreased control accuracy at high current is primarily owing to ripples from the high-voltage power supply, the transient beam loading effect, and the digital aliasing effect. The current LLRF algorithm is not able to suppress these disturbances.

Design Method Based on Normalized Functions for a Toroidal Inductor Applied to Power-Quality Evaluation

The design method for a low-cost toroidal inductor is proposed as an alternative to power-quality evaluation. The method is based on well-known tools by the engineers in which is presented the relationships that exist between equivalent circuit and transfer function of a toroidal inductor. The proposed design method has been explained with normalized functions based on physical parameters of a toroidal inductor. This work presents the main arguments of the suggested methodology and as demonstration of the design method as function of normalized parameters, is developed a current-signal sensor which has been validated in the laboratory by the EN-50160-2-2 standard to evaluate the power quality in home use loads.

The Effects of Fatigue Cracks on Fastener Loads during Cyclic Loading and on the Stresses Used for Crack Growth Analysis in Classical Linear Elastic Fracture Mechanics Approaches

High strength threaded fasteners are widely used in the aircraft industry, and service experience shows that for structures where shear loading of the joints is significant, like skin splices, fuselage joints or spar caps-web attachments, more cracks are initiated and grow from the edges of the fastener holes than from features like fillets radii and corners or from large access holes. The main causes of this cracking are the stress concentrations introduced by the fastener holes and by the threaded fasteners themselves, with the most common damage site being at the edge of the fastener holes. Intuitively, it is easy to visualize that after the crack initiation, during the growth stages, some of the load transferred initially by the fastener at the cracked hole will decrease, and it will be shed to the adjacent fasteners that will carry higher loads than in uncracked condition. Using currently available computer software, the method presented in this paper provides a relatively quick and quantitatively defined solution to account for the effects of crack length on the fastener loads transfer, and on the far field and bypass loads at each fastener adjacent to the crack. At each location, these variations are determined from the 3-dimensional distribution of stresses in the joint, and accounting for secondary bending effects and fastener tilt. Two cases of a typical skins lap splice with eight fasteners in a two rows configuration loaded in tension are presented and discussed, one representative for wing or fuselage skins configurations, and the second case representative for cost effective laboratory testing. Each case presents five cracking scenarios, with the cracks growing from approx. 0.03 inch to either the free edge, next hole or both simultaneously.

桩顶荷载及温度循环对黄土地基中能量桩承载性状影响研究

为对比分析未经过温度循环的普通桩与能量桩竖向承载变形性状,开展黄土地基中能量桩温度循环试验。模型桩为现浇钢筋混凝土灌注桩,黄土为人工配制重塑黄土。研究结果表明:温度循环弱化黄土地基中能量桩桩身侧阻、增强能量桩桩底端阻,温度循环过程中桩顶工作荷载越大,桩侧阻的弱化作用及桩端阻的增强作用越大,这导致能量桩的竖向抗压承载力比普通桩有明显的提高。另外,根据模型试验结果,通过数据拟合建立桩土界面摩阻力-桩土相对位移及桩端土反力-桩端沉降双曲线函数模型,并确定模型参数,其函数计算结果与试验结果对比表明本文模型能合理反映温度循环及桩顶工作荷载大小对桩基承载力的影响。研究结果可为黄土地区能量桩的安全设计提供一定参考。

基于隐式Lyapunov函数的弹药传输机械臂变增益超螺旋滑模控制

为提高某弹药传输机械臂在传输弹药过程中受到负载不确定性影响下的定位控制鲁棒性,提出一种新型的基于隐式Lyapunov函数变增益超螺旋滑模控制方法。建立弹药传输机械臂系统的动力学方程,并对方程中摩擦力矩及支反力矩的重要参数进行辨识,减少系统不确定性。构造隐式Lyapunov函数并设计出一种新型的变增益超螺旋滑模控制策略,通过Lyapunov稳定性理论证明闭环系统全局稳定。超螺旋滑模控制增益的变化取决于系统的Lyapunov函数,是滑模变量的可微函数,具有控制参数易调节的优势。实验结果表明:摩擦力矩及支反力矩补偿可使系统定位时间由补偿前2.659 s缩短到1.157 s,提高了系统定位性能。在不同工况下,控制方法可有效地抑制系统负载不确定性的影响,保证系统的定位稳定性。

双馈风力发电机组变流器控制参数分步辨识方法

该文通过构建双馈风力发电机组转子侧与网侧控制系统包含8个PI控制器待辨识参数的内、外环传递函数作为参数辨识模型,基于此提出内外环施加不同扰动源的激励方法和基于改进灰狼算法的分步参数辨识方法。为避免内外环PI控制器之间的级联问题,特别选出3个合理的内外环观测量。最后,建立双馈风力发电机组仿真模型,测试所提分步辨识方法可行性,对比扰动下实际模型与辨识模型的观测量输出,证明辨识方法的准确性。

基于LSTM与迁移学习的配电网负荷频率控制PI参数整定方法

在整定配电网络负荷频率过程中,控制器PI参数会受到局部控制迭代影响,在控制层与反馈层形成时间差量,进而造成频率里程偏差。对此,提出基于LSTM与迁移学习的配电网负荷频率控制PI参数整定方法。采用LSTM模型对调频(FM)里程参数进行模型量化,配合迁移学习对负荷频率控制相关参量进行差分更新,构建配电网负荷频率的LSTM模型,进行频率控制的迁移学习优化、PI参数控制约束及PI参数整定输出。实验结果表明,不论是在控制精度上还是在控制稳定性上,均具有良好的性能表现,整定结果满足预期。

具有LC串联补偿拓扑结构的无线充电系统的约束效率优化

开发基于感应功率传输的无线充电系统是一个很有前途的研究领域。本研究的目的在于,在给定谐振频率和给定发射线圈和接收线圈之间距离的情况下,优化具有LC串联补偿拓扑结构的无线充电系统的约束效率。这些约束反映了线圈的尺寸限制、输入电压限制下所需的传输功率,以及部件上的过电压。为了达到目标,制定了优化标准。已经为频域中优化标准的每个组件建立了对无线充电系统谐振电路参数的依赖性。由于这些依赖关系看起来非常复杂,在给定的情况下利用参数之间的联系,并采用最小二乘法的切比雪夫多项式近似,它们在优化任务中被简化为一个变量。因此,理论上已经获得了指示优化标准满足的谐振电路参数。利用为电动卡车ET-20132专门制造的无线充电系统对所提出的约束效率优化方法进行了实验验证。实验和理论的比较表明,它们在谐振频率上具有良好的收敛性,由数学模型中的假设引起的谐振频率偏差是可接受的。经实验证明,无线充电系统的效率为91%。

Design method of multivariable PI controller for turboprop engine based on equivalent transfer function

Traditional centralized Proportional Integral(PI)controller design methods based on Equivalent Transfer Functions(ETFs)have poor decoupling effect in turboprop engines.In this paper,a centralized PI design method based on dynamic imaginary matrix and equivalent transfer function is proposed.Firstly,a method for solving equivalent transfer functions based on the dynamic imaginary matrix is proposed,which adopts dynamic imaginary matrix to describe the dynamic characteristics of the system,and obtains the equivalent transfer function based on the dynamic imaginary matrix characteristics.Secondly,for the equivalent transfer function,a central-ized PI control gain is designed using the Taylor expansion method.Meanwhile,this paper further proves that the centralized PI design method proposed in this paper has integral stability.Consid-ering the impact of altitude and Mach number on turboprop engines,a linear feedforward control method based on the transfer function matrix is further proposed based on the centralized PI con-troller,and the stability of the entire comprehensive control method is proved.Finally,to ensure the safe and effective operation of the turboprop engine,a temperature and torque limiting protection controller is designed for the turboprop engine.Simulation results show that the centralized PI con-troller design method and linear feedforward control method proposed can effectively improve the control quality of turboprop engine control systems.

冷链运输车空调冷风机运行自适应PID控制方法研究

冷链运输车空调冷风机运行环境复杂,导致传统的比例积分微分(PID)控制过程难以准确设定控制参数。为解决这一问题,设计冷链运输车空调冷风机运行自适应PID控制方法。首先,通过分析冷链运输车空调冷风机工作过程,选取多个控制参数,以降低复杂度。然后,设计基于自适应PID控制器的控制模型,以送风温度和送风压力作为控制量,将冷、热水流量及风机转速作为被控制量,求解控制量和被控制量的传递函数。最后,根据传递函数与期望值间的耦合关系,对控制分量的增减进行调整,以实现冷链运输车空调冷风机运行的自适应PID控制。试验结果表明,该方法能够使冷链运输车内温度保持稳定。该方法控制精准度高、鲁棒性强、实用价值高,可以确保货物在整个冷链运输过程中的质量和安全。

某型电液伺服阀仿真与参数影响分析

对某型双喷嘴挡板力反馈式两级电液伺服阀进行了数学建模,对其动态特性进行了分析,推算出了模型的传递函数,然后对其的时域和频域曲线进行分析验证了系统的稳定性,最后通过改变伺服阀结构参数对阀芯位移以及响应时间的影响,得出了结构参数对伺服阀动态特性的影响。结果表明,改变力矩马达力矩系数Kv、喷嘴中心线到弹簧回转中心的距离r以及滑阀阀芯面积Ac对伺服阀的动态特性都会产生影响,为伺服阀的设计与改进提供了参考。

建筑内热源滞后冷负荷监测模型研究

准确获取内热源实时冷负荷对于制定供暖空调系统节能调控策略及降低建筑运行能耗具有重要意义,而辐射热传递过程产生的滞后冷负荷是内热源冷负荷计算的难点,为此,基于围护结构蓄放热规律、热传递特性及传递函数原理等建立内热源滞后冷负荷监测模型,该模型为10阶传递函数。为了简化计算过程、提高计算精度,利用辐射时间系数对该模型进行参数辨识及降阶分析,最终得到2阶传递函数。建立试验系统对模型进行验证,结果显示,模型的平均绝对百分比误差为8.19%。内热源滞后冷负荷监测模型可依托能耗监测平台实现负荷的在线监测,对描述滞后冷负荷的时间延迟规律及幅度衰减特性具有理论意义,为制定供暖空调系统节能调控策略提供理论依据。

带执行机构的恒压差控制系统稳定性研究

基于某型航空发动机加力燃油调节器的恒压差控制系统,推导出带执行机构的恒压差控制装置的动态数学模型(状态空间形式),得到其传递函数,并利用Simulink建立仿真模型,根据模型求取闭环零极点图,提取了影响压差控制系统稳定性的6个参数,包括节流嘴直径、压差控制活门和压差执行活门节流孔面积梯度、压差控制活门和压差执行活门阀芯面积,并研究了其对系统稳定性的影响。通过合理的元件试验方案进行试验验证,最终确定此恒压差控制装置的数学模型仿真结果可以作为恒压差控制装置动态稳定性分析以及设计的依据。

基于S参数的GIS特高频传感器现场校验方法研究

特高频法通过传感器检测GIS设备故障条件下特高频电磁波信号,若传感器灵敏性出现异常,将导致GIS运行稳定性下降。针对此问题,研究基于S参数的GIS特高频传感器现场校验方法。以一个双端口网络描述GIS设备内两个特高频传感器及其间的GIS结构,嵌入S参数网络,通过测量相邻两传感器间的传递函数,检测GIS设备内相同结构位置处特高频传感器的原始单端插入损耗曲线、初始单端插入损耗均值、初始单端插入横向相对误差等,能够获取GIS特高频传感器性能及其布置方式,高精度检测GIS内置特高频传感器在安装条件下与运行条件下的运行态势。实验结果显示:该方法不受注入脉冲宽度影响,可准确校验传感器灵敏性,提升GIS运行稳定性。

计及分布式光伏接入的配电网脆弱性评估研究

分布式光伏的接入会对配电网脆弱性水平造成较大的影响,继而影响配电网的安全稳定运行。在分析分布式光伏功率特性的基础上,结合配电网节点静态能量函数模型和负荷转移系数相关理论,提出一种可反映配电网节点状态和结构的脆弱性评估模型。建立含分布式光伏接入的配电网仿真计算模型,对光伏不同并网容量和多个光伏不同并网位置对配电网脆弱性的影响规律进行研究。结果表明,随着光伏并网容量的增大,其对配电网脆弱性的影响呈现先逐渐增大后趋于稳定的态势,稳定后脆弱性最小值降低了约24%、最大值增大了约31%,且多个分布式光伏的并网节点越靠近配电网末端,并网距离越小,配电网脆弱性受到的影响越大。

黄河下游冲积平原试验区土壤水分特征曲线的传递函数研究

黄河下游冲积平原区是我国重要的粮食生产基地和工业集聚地,该地区土壤水力学参数的获取,对于保障用水安全和指导农业生产具有重要意义。为建立黄河下游冲积平原区的土壤水分特征曲线传递函数(PTFs),以河南省兰考县闫楼乡作为黄河下游冲积平原试验区,基于多元非线性逐步回归和单因素扰动方法,建立了包气带土壤水分特征曲线的PTFs,并分析了影响因素敏感性。研究结果显示,实测土壤水分特征曲线以及土壤理化性质参数呈现较强变异性,所建立的PTFs精度良好,具备应用推广价值。多元回归结果表明,土壤颗粒组成是本文PTFs的主要影响因素,其中黏粒含量对PTFs最为敏感,砂粒含量次之,粉粒含量最弱。在其余5个土壤理化特性中,对PTFs的相对敏感的因素是pH值和分形维数。研究表明,土壤物理化学性质与土壤水分特征曲线模型参数的关系复杂,并非一般线性或单调关系。尽管土壤物理化学性质参数可以提高PTFs精度,但土壤颗粒组成是影响土壤水分运动的根本原因,其作为构建PTFs的关键因素不可忽略。在实际应用中,PTFs使用者可根据所掌握数据的实际情况,结合影响因素敏感性,决定影响因素的取舍。

并联负荷分配控制系统设计研究

多个储能装置并联时,如何提高储能装置剩余容量的利用率,完成每个储能装置能量按需分配,并保证系统平稳安全运行的问题受到研究人员的关注。对多个储能装置并联系统的能量管理策略进行研究,基于输出电流和储能装置的剩余容量引出负荷系数的概念,并提出了中间负荷系数控制模式,同时基于此控制模式进行了建模和三环控制系统传递函数的推导。通过3个储能装置并联系统进行仿真和实验,验证了所提负荷分配控制策略的稳定性与合理性,避免了储能装置因过度放电或过度充电提前退出运行,并达到了按照剩余容量进行负荷分配的目标。

深圳某实验楼空调冷热源选型分析

本文以深圳某实验楼空调冷热源选型为例,结合项目功能、建筑场地、室内参数控制精度、负荷特性、使用方要求及节能高效等因素,对冷热源方案进行对比分析,选择合适的冷热源。

频域传递路径分析方法(TPA)的研究进展

传递路径分析方法(Transfer Path analysis,TPA)是当前诊断机械系统振动和噪声最通用的手段。本文介绍了传统TPA、工况TPA、OPAX、快速TPA、多级TPA以及混合TPA的基本原理和优缺点,结合实例说明实现过程,并进行综合比较得出各种方法的应用场合,最后对TPA方法的未来发展作了展望。