基于压电陶瓷的风机叶片模型覆冰主动监测

南方山区高湿低温严酷环境易导致冰灾,风机叶片覆冰会导致发电效率降低甚至停机,因此发展高效可靠的风机叶片覆冰监测技术对防冰、除冰具有重要意义。该文提出了一种基于压电陶瓷应力波测量的风机叶片覆冰主动监测方法。开展叶片模型进行模拟覆冰试验,在叶片表面布置伸缩型和剪切型两种压电陶瓷片,根据波动法原理对驱动器输入正弦扫频电压信号作为激励,记录不同传感器在不同结冰厚度下的响应信号,并对测量信号进行小波包能量分析。结果表明,同一压电陶瓷片接收信号的小波包能量与结冰厚度存在明显关系。     

基于压电波动测量的套筒灌浆缺陷检测试验

套筒灌浆连接是当前装配式建筑中受力钢筋的主要连接方式,其灌浆质量是影响装配式混凝土结构性能的关键因素之一。运用压电陶瓷材料的驱动和传感功能,该文提出了一种基于波动分析的套筒灌浆缺陷主动检测方法,并通过试验验证其可行性,通过数值模拟分析其机理。在套筒连接钢筋表面粘贴压电片,测量健康试件和设置有不同尺寸缺陷试件上压电陶瓷传感器的输出信号,并对小波包能量进行分析和比较。结果表明,灌浆缺陷导致压电陶瓷传感器输出信号的电压幅值增大,小波包能量指标与套筒灌浆缺陷尺寸大小相关。该法能对套筒内灌浆缺陷进行有效检测。     

基于压电陶瓷的混凝土裂缝损伤监测

压电陶瓷的正逆压电效应决定其既可作传感器又可作驱动器.将压电陶瓷埋于混凝土中并对其施加激励,可在混凝土中产生应力波.根据该波动法原理.应用自行研制封装的压电陶瓷传感器对混凝土中裂缝损伤的产生过程进行监测.采用基于小波包分析法定义的损伤指标对不同工况下的损伤进行计算,结果表明,损伤指标的变化趋势与相应的应变片监测信号和荷载位移曲线的发展趋势吻合良好,实现了对混凝土中微小裂缝损伤的监测和识别.     

基于压电材料的钢筋砼-钢组合塔筒损伤监测

钢筋混凝土-钢组合塔筒作为一种新型的风电塔架形式,其混凝土段的开裂对其使用寿命具有重要影响,对其混凝土段的开裂进行监测具有重要意义。该文提出了一种基于压电陶瓷激励的应力波测量的钢筋混凝土塔段的开裂监测方法,以某钢筋混凝土-钢塔筒缩尺模型为对象,以布置在钢筋混凝土塔筒表面的压电陶瓷片为激励器,利用布置在钢筋混凝土塔筒不同高度位置的压电陶瓷片作为传感器,实现在不同水平往复加载下的应力波的测量。对混凝土塔段从裂缝开始出现直至构件最终破坏整个过程各压电陶瓷片的响应进行分析,并定义损伤指标。结果表明,定义的指标不仅可较好反应裂缝实际出现位置,且与加载等级相关,所提出的监测方法可对钢筋混凝土塔段裂缝的发生和发展过程进行有效监测。     

基于嵌入压电技术的钢管核心混凝土缺陷检测

钢管混凝土构件核心混凝土缺陷影响到其延性和承载力。利用自制的嵌入式压电功能元,该文提出了基于压电陶瓷应力波测量与分析的核心混凝土缺陷监测方法。通过对比在不同状态的简谐激励下测量信号幅值和扫频激励下小波包能量的差异,定义了基于测量信号幅值和小波包能量的损伤指标。结果表明,利用提出的嵌入式压电技术和定义的损伤指标,有效地识别了钢管混凝土构件的核心混凝土损伤,损伤指标对损伤程度敏感。     

基于嵌入压电技术的钢管核心混凝土缺陷检测

钢管混凝土构件核心混凝土缺陷影响到其延性和承载力。利用自制的嵌入式压电功能元,该文提出了基于压电陶瓷应力波测量与分析的核心混凝土缺陷监测方法。通过对比不同状态简谐激励下测量信号幅值和扫频激励下小波包能量的差异,定义了基于测量信号幅值和小波包能量的损伤指标。结果表明,利用所提出的嵌入式压电技术和所定义的损伤指标,有效地识别了钢管混凝土构件的核心混凝土损伤,损伤指标对损伤程度敏感。     

基于压电陶瓷的销轴连接受力状态监测

销轴连接作为工程中一种常用的连接构件,实时监测其在荷载下的健康状态,对结构的整体稳定性至关重要。该文研究了一种基于压电理论的销轴连接受力状态的实时监测方法,并对其展开了理论和实验研究。同时基于小波包理论分析接收信号的能量,从而识别销轴连接的受力状态。研究结果表明,接收信号的能量与销轴连接的受力状态相关,随着接触面的法向压力增大,接收信号的能量增大,但当法向压力增大到一定值后,接收信号能量达到饱和。因此,该文提出的基于压电理论的销轴连接受力状态监测方法在一定的荷载范围内具有良好的可行性和应用意义。     

冲击下钢筋混凝土桥墩损伤监测试验研究

钢筋混凝土桥墩受船舶等撞击后损伤状况的监测对其安全性评估具有重要意义。该文提出一种基于压电应力波传播的钢筋混凝土桥墩损伤状况监测方法,对表面布置有压电陶瓷传感器阵列的钢筋混凝土桥墩缩尺模型进行落锤冲击试验,对比冲击前后简谐激励下测量信号幅值和扫频激励下测量信号小波包能量值,实现试件裂缝损伤监测。监测结果与试件实际开裂情况吻合。结果表明,所提方法能有效地监测桥墩结构在冲击作用后的裂缝损伤状况。     

基于压电陶瓷光相位调制器的光纤微分干涉仪

基于压电陶瓷的逆压电效应,采用压电陶瓷作为光相位调制器设计了光纤微分干涉仪。理论分析和实验结果表明,干涉仪输出光强的幅度和频率与施加在压电陶瓷上的交变信号电压的幅度和频率有关,且在一定的条件范围内呈良好的线性关系。这种采用压电陶瓷作为光相位调制器的干涉仪具有线性范围广,灵敏度高等特点,可应用于对外界环境振动源的监测或用于检测压电陶瓷自身的动态特性。     

基于压电波动测量的竹梁界面剥离监测试验

作为天然绿色材料胶合竹材在建筑和土木工程上的应用引起广泛关注,对外荷载作用下竹结构的状态进行监测具有重要应用价值。该文对一竹梁构件模型进行分级加载直至破坏,基于压电应力波传播与测量对其各受力状态下的状态进行监测。通过对比不同荷载等级时简谐激励信号下压电传感器的测量信号的幅值和扫频激励下小波包能量的差异,定义相应的损伤指标,实现了对竹梁构件在加载过程中损伤状态的有效监测。     

风轮机叶片电磁散射特性的占比分析与解析模型的建立

针对风轮机叶片雷达散射截面积的变化特性,分析了风轮机叶片雷达散射截面积（Radar Cross Section, RCS）对其整体雷达散射特性占比情况,实现对叶片解析模型适用范围的选取。考虑了风轮机叶片旋转平面与雷达视线（Line of Sight, LOS）夹角、叶片材料、叶片几何形状等因素对风轮机散射特性的影响,运用UG软件对风轮机叶片进行三维建模,利用真实叶片与相应简化圆柱叶片电磁散射特性的差异构建高保真的风轮机真实叶片电磁散射特性的解析模型,实现风轮机叶片RCS的快速计算。最后将解析模型计算结果与实测数据进行对比,验证了论文给出的真实叶片电磁散射特性解析模型的有效性。      

Health assessment and management of wind turbine blade based on the fatigue test data

With the quality problem becoming increasingly prominent, it is necessary to assess and manage the health condition of the wind turbine blade. The health degree is defined and calculated by the Grey Relation (GR) model to assess the health condition of the wind turbine blade quantitatively. The availability, reliability and artificial test result are taken as three indexes of the health degree. The availability is defined according to the stiffness degradation affected by the environmental temperature. Based on the health assessment results, after determining the decision objectives and the management strategies, the weights of the decision objectives and the health management decision are determined by the Analytic Hierarchy Process and Fuzzy (AHP-Fuzzy) decision method. This process is shown in a practical example of the 3 MW wind turbine blade. As a result, an approach and a certain theoretical guidance for the health assessment and management of wind turbine blade are proposed.     

Experience with bicoherence of electrical power for conditionmonitoring of wind turbine blades

The authors explore the application of the normalised bispectrum or bicoherence to the problem of condition monitoring of wind turbine blades. Background information is provided on this type of condition monitoring, how it differs from more conventional condition monitoring of turbo machinery, and the motivation for selecting bicoherence. Bicoherence is defined and compared with the power spectral density. Complications in collecting suitable data, and estimating the bicoherence from that data are investigated; including the requirements of very long stationary data sets for consistent estimates, and computational difficulties in handling such large data sets. Bicoherence is then applied to electrical power output data obtained from a 45 kW wind turbine. The turbine is operated in three configurations to represent normal and fault conditions. A blade with less flapwise stiffness but identical outer dimensions to the matched set of blades was fitted to simulate a damaged blade. Comparison of the results from the power spectral density and bicoherence indicates how the bicoherence might be employed for condition monitoring purposes. Slices of the bicoherence with one frequency fixed at the rate of rotation show clear differences between the configurations and substantially reduce the computational effort required to calculate the estimate     

风轮机雷达散射特性仿真及微多普勒特征分析

风轮机复杂的电磁散射特性,会对其附近的空管通信、导航和监视等电子设备产生严重影响.研究风轮机的电磁散射特性,可为风轮机杂波检测和抑制提供理论依据,对保证空中交通安全具有重要的意义.论文首先基于风轮机散射点叠加的理论,考虑了雷达入射波到风轮机叶片和桅杆的初始相位以及入射波方位角和俯仰角对回波的影响,将单基地回波模型扩展到双基地模型.同时,在散射点叠加模型的基础上,提出了基于混合模型的风轮机散射特性分析.混合模型结合了散射点叠加模型和电磁仿真软件FEKO的优点,考虑了电磁波在叶片和桅杆上的反射系数等因素对回波的影响,可以实现任意观测点处的电磁散射特性计算及其微多普勒特征的分析.最后,分别对散射点叠加模型、FEKO以及混合模型的风轮机电磁散射特性分析方法进行了对比分析,给出了各自的优缺点及其适用场合.     

Pitch controller for wind turbine load mitigation through consideration of yaw misalignment

Recent developments in sensor and actuator technologies have promoted the design and implementation of individual pitch controllers (IPCs) to mitigate fatigue loads on turbine blades caused by vertical wind shear. So far, IPCs have been designed assuming perpendicularity of the oncoming wind with respect to the turbine rotor plane as an independent yaw controller is dedicated to eliminate any misalignments. In this paper, a multi-input-multi-output (MIMO) IPC is designed based on the knowledge of mitigated blade load at a yawed inflow condition (i.e., yaw misalignment at certain angular position). Nonetheless, the proposed IPC is still to operate in the typical turbine configuration, in which the turbine is aligned with the wind direction. Performance of the proposed IPC is compared with that of the baseline collective pitch controller (CPC) and baseline IPC on simulations of the NREL 5 MW reference turbine at various turbulent wind conditions. Compared with the baseline CPC, the proposed controller is shown to contribute at least a 31.54% reduction in the blade out-of-plane fatigue load, a 35.32% reduction in the tower fore-aft fatigue load, and a 29.80% reduction in the tower side-to-side fatigue load.     

基于散射中心的风电机叶片散射电场求解

为降低雷达系统的数据处理量及实现风电机实时目标特征识别,必须寻求风电机叶片散射电场的快速求解方法。针对传统电磁求解算法需处理巨量风电机叶片散射电场数据的问题,突破传统以超大电尺寸目标实体为基本单元进行广域空间电磁散射积分计算的思想,提出了一种基于散射中心的风电机叶片散射电场求解方法。基于非衰减指数和散射中心模型,通过距离-多普勒算法构建风电机叶片的雷达逆合成孔径图像,采用CLEAN 算法并结合相关系数提取风电机叶片的散射中心参数集,最终以散射中心产生的散射电场数据等效替代叶片本体的全部散射数据,实现了叶片散射电场的快速求解。以Vestas V82-1.65MW 型风电机为例,以矩量法计算结果为基准,文中所提方法计算准确度为93.20%,数据的压缩比达76.81,计算量的数量级比矩量法降低了106。     

大型风电叶片动态摄影测量网络优化

在大型风电叶片动态摄影测量中,为了对相机的站位进行优化,采用一种变异操作改进型遗传算法作为摄影测量网络优化方法,通过光线束前方交会的误差传递建立测量误差模型,以空间坐标测量误差的标准差为网络优化的目标,同时根据被测风电叶片几何结构和实际环境确定了相应的约束条件进行仿真实验,得到了最优的相机站位。结果表明,在以叶片长度为40m的风机为被测物的仿真实验中,最优站位的空间坐标测量误差标准差为2.7mm;通过对叶片长度为3.5m的风机模型进行实测实验验证,最优站位的相对测量误差为0.009%,最大误差为0.617mm。该研究为风电叶片摄影测量的网络优化提供了参考。     

Data-driven design of robust fault detection system for wind turbines

In this paper, a robust data-driven fault detection approach is proposed with application to a wind turbine benchmark. The main challenges of the wind turbine fault detection lie in its nonlinearity, unknown disturbances as well as significant measurement noise. To overcome these difficulties, a data-driven fault detection scheme is proposed with robust residual generators directly constructed from available process data. A performance index and an optimization criterion are proposed to achieve the robustness of the residual signals related to the disturbances. For the residual evaluation, a proper evaluation approach as well as a suitable decision logic is given to make a correct final decision. The effectiveness of the proposed approach is finally illustrated by simulations on the wind turbine benchmark model.