A visual reconstruction method was proposed based on fiber Bragg grating (FBG) sensors and an intelligent algorithm, aiming to solve the problems of low accuracy and complex reconstruction process in conventional reconstruction methods of flexible structures. Firstly, the wavelength data containing structural strain information was captured by FBG sensors, together with deformation displacement information. Subsequently, a predicted model was built based on an extreme learning machine (ELM) and further optimized by the particle swarm optimization (PSO) algorithm. Different deformation patterns were tested on an aluminum alloy plate, indicating the ability of the predicted model to produce the deformation displacement for reconstruction. The experimental results show that the maximum error can be as low as 0.050 mm, which verifies that the proposed method is feasible and satisfied with the deformation monitoring of the spacecraft structure.

In this paper, a plate shape perception technique based on quasi-distributed fiber Bragg grating (FBG) array and space surface reconstruction algorithm is proposed. Firstly, in order to make curvature continuous, the bicubic plane interpolation algorithm is studied. Then, taking the simulated satellite bulkhead structure as the research object, we research the space surface reconstruction algorithm based on orthogonal curvature and coordinate transformation (translation and rotation). Finally, a four-sided fixed plate deformation monitoring system based on quasi-distributed FBG sensors network and surface reconstruction algorithm is built. Many experiments are conducted to verify the reliability and accuracy of the algorithm. The proposed algorithm provides a new method for three-dimensional reconstruction of spacecraft structure.

围绕工字钢梁损伤识别问题,研制了一种新型双端固定梁结构光纤布拉格光栅(FBG)振动传感器,实现了工字钢梁振动响应的有效获取。在此基础上,研究了工字钢梁损伤自动识别方法,利用其对FBG振动传感器获取的振动响应进行处理。该方法采用小波包能量比变化偏差(ERVD)作为损伤特征,进而基于极限学习机(ELM)算法实现工字钢梁损伤状态识别。传感器仿真模拟和实验测试结果表明:设计的FBG振动传感器频率响应范围为10~350 Hz,在加速度响应范围为0.2g~3.0g时,灵敏度为6.7 pm/g,具有良好的线性度和横向抗干扰能力。工字钢梁损伤识别实验结果表明:所提方法对工字钢梁的损伤状态识别准确率达到96.7%,与常规的基于back propagation(BP)神经网络的损伤识别方法相比,准确率提高了3.4个百分点。

针对铝合金结构服役过程中的疲劳裂纹监测问题,提出了一种基于光纤光栅传感阵列的疲劳裂纹实时监测方法。首先,结合扩展有限元技术获得裂纹扩展过程的应变场分布特征,进行传感器布局设计;其次,通过疲劳加载实验获取加载次数、裂纹长度对波长峰峰值的响应特征,采用三参数指数法进行疲劳扩展a-N(其中N为加载次数,a为裂纹长度)曲线拟合;在实验数据基础上,采用梯度提升回归树算法搭建疲劳损伤预测模型,并将其与线性回归、支持向量两种方法进行对比,选取可释方差、平均绝对误差、平均方差、决定系数和五折交叉验证等多种指标进行模型评估。结果表明,梯度提升回归树算法对疲劳裂纹长度的预测效果最佳。

建立一种能够快速、定量检测掺假普洱茶中香豆素、香兰素、乙基麦芽酚三种常见香精的方法。利用傅里叶变换近红外光谱技术结合偏最小二乘法对香精掺假普洱茶进行定量分析。分别建立三种掺假香精成分的定量分析模型,并对比基于不同预处理方法和未经光谱预处理的定量分析模型的预测能力。结果表明:结合不同光谱预处理方法实现的针对香豆素、香兰素和乙基麦芽酚三种香精的预测均方根误差分别为0.1461,0.1678,0.1800,预测决定系数分别为0.7989,0.7350,0.6938,三种香精的检测限为0.2 mg/g。近红外光谱技术结合偏最小二乘定量分析方法可以实现掺假普洱茶中三种香精成分的快速检测分析。

以航天器中结构的形态感知与可视化重构为研究背景,提出了一种基于准分布光纤光栅传感器网络的板状结构变形监测系统和坐标转换曲面重构算法。首先利用ABAQUS有限元分析软件对四边固支平板结构中心点加载的变形状态进行仿真分析,确定了光纤光栅传感器的位置;研究并分析了光纤光栅的应变检测原理以及基于坐标变换的三维曲面重构算法;最终搭建了一套变形检测系统并进行了相关实验。结果表明,测量点变形量的均方根误差≤0.04 mm,相对误差≤3.5%,该系统可用于航天器板状结构的变形监测。

通过建立校正集样本不同的模型Ⅰ与模型Ⅱ来研究温度对水泥生料近红外光谱模型的影响,其中模型Ⅰ中的建模样本为温度一致的样本,模型Ⅱ中的建模样本为温度变化的样本,建模方法采用偏最小二乘法。对比两组模型的预测结果可知,模型Ⅱ中SiO2、Al2O3、Fe2O3、CaCO3的预测方均根误差与模型Ⅰ相比分别减小了78.3%、26.4%、42.9%、60.4%。实验结果表明:温度变化会导致预测结果产生一定的误差。在校正集中加入温度不同的样本进行建模,可以降低预测误差,使近红外光谱模型更好地应用于生产现场。

A damage identification system of carbon fiber reinforced plastics (CFRP) structures is investigated using fiber Bragg grating (FBG) sensors and back propagation (BP) neural network. FBG sensors are applied to construct the sensing network to detect the structural dynamic response signals generated by active actuation. The damage identification model is built based on the BP neural network. The dynamic signal characteristics extracted by the Fourier transform are the inputs, and the damage states are the outputs of the model. Besides, damages are simulated by placing lumped masses with different weights instead of inducing real damages, which is confirmed to be feasible by finite element analysis (FEA). At last, the damage identification system is verified on a CFRP plate with 300 mm × 300 mm experimental area, with the accurate identification of varied damage states. The system provides a practical way for CFRP structural damage identification.

In order to achieve rotation angle measurement, one novel type of miniaturization fiber Bragg grating (FBG) rotation angle sensor with high measurement precision and temperature self-compensation is proposed and studied in this paper. The FBG rotation angle sensor mainly contains two core sensitivity elements (FBG1 and FBG2), triangular cantilever beam, and rotation angle transfer element. In theory, the proposed sensor can achieve temperature self-compensation by complementation of the two core sensitivity elements (FBG1 and FBG2), and it has a boundless angel measurement range with 2πrad period duo to the function of the rotation angle transfer element. Based on introducing the joint working processes, the theory calculation model of the FBG rotation angel sensor is established, and the calibration experiment on one prototype is also carried out to obtain its measurement performance. After experimental data analyses, the measurement precision of the FBG rotation angle sensor prototype is 0.2. with excellent linearity, and the temperature sensitivities of FBG1 and FBG2 are 10 pm/℃ and 10.1 pm/℃, correspondingly. All these experimental results confirm that the FBG rotation angle sensor can achieve large-range angle measurement with high precision and temperature self-compensation.

In some applications in structural health monitoring (SHM), the acoustic emission (AE) detection technology is used in the high temperature environment. In this paper, a high-temperature-resistant AE sensing system is developed based on the fiber Bragg grating (FBG) sensor. A novel high temperature FBG AE sensor is designed with a high signal-to-noise ratio (SNR) compared with the traditional FBG AE sensor. The output responses of the designed sensors with different sensing fiber lengths also are investigated both theoretically and experimentally. Excellent AE detection results are obtained using the proposed FBG AE sensing system over a temperature range from 25℃ to 200℃. The experimental results indicate that this FBG AE sensing system can well meet the application requirement in AE detecting areas at high temperature.