PT/PZT/PT薄膜微力传感器

提出了一种基于PT/PZT/PT压电薄膜微悬臂梁结构的微力传感器.运用Sol-Gel(溶胶-凝胶)法制作了PT和PZT薄膜,采用X射线衍射技术表征了PZT和PT/PZT/PT两种薄膜的成相特征,用阻抗分析仪测试了PZT和PT/PZT/PT薄膜的介电常数.结果表明,在PZT薄膜退火温度同为600℃时,PZT和PT/PZT/PT薄膜均为完整的钙钛矿结构,而且PT/PZT/PT薄膜沿(100)晶向强烈取向;在测试频率为1 kHz时,经600℃热处理条件下制备的PZT和PT/PZT/PT薄膜的相对介电常数分别为525和981.最后应用MEMS工艺制作了基于PT/PZT/PT压电薄膜微悬臂梁结构的微力传感器.在静态和准静态下对微力传感器的传感特性进行了测试.测试结果表明,力与位移或电荷具有良好的线性关系.两种尺寸微力传感器的灵敏度分别为0.045 mV/μN和0.007 mV/μN,力分辨率分别为3.7 μN和16.9μN,满足了微牛顿量级微小力的测量.     

Interfacial reactions in PZT/Pd/PZT sandwich structures

The interfacial reactions of palladium foil and lead zirconate-titanate (PZT) were studied using samples with a sandwich structure in the temperature range 1373–1523 K and under conditions where no lead is lost to the environment. The interfacial reactions were analysed using scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction and wavelength-dispersive X-ray spectroscopy analysis. The density of the PZT powder phase increased with increasing temperature and, when sintered above 1373 K, reached over 95% of the theoretical density of PZT. The weight loss of pellets was less than 0·8% when sintered below 1523 K. The degree of interfacial reactions became more severe with increasing temperature, as indicated by an expanding reacted region. The reaction at the PZT side of the Pd/PZT interface involved the decomposition of PZT into a monoclinic ZrO₂ phase, PbO and a lower x-value Pb(Zr_xTi₁__x)O₃ composition. Three distinguishable microstructures exist on the Pd side when sintered below 1473 K: a thin layer of PbPd₃ phase, a Pd–Pb solid solution zone and an unreacted region. Only the cubic PbPd₃ eutectic structure was found when sintered above 1473 K. The oxidation of palladium occurred during interfacial reactions, expedited by increasing temperature and resulting in the formation of the tetragonal PdO phase and the hexagonal PbPdO₂ phase. A model for the overall reaction is proposed involving decomposition of the PZT, migration of PbO and diffusion of Pb into Pd foil.     

基于分形维数的复合材料结构损伤成像

提出了一种基于分形维数的损伤成像算法,对复合材料结构的健康状况进行在线的连续监测.利用盒计算维数法来计算传感器阵列所采集信号的分形维数,对比复合材料结构损伤前与损伤后信号分形维数的差异,提取损伤指标;然后基于一种改进的损伤存在概率成像算法,以直观的形式对复合材料结构中的损伤进行成像.对复合材料平板结构以及复合材料加筋板结构中的损伤监测进行了实验研究,研究结果不仅显示了所提出的算法能克服复合材料各向异性以及复杂结构中Lamb波的多次反射给损伤监测带来的困难,较为准确地识别2种结构中损伤的位置和大小,还验证了所提出算法在识别复合材料结构中的多个损伤时的可行性和有效性.     

Damage localisation in composite and metallic structures using a structural neural system and simulated acoustic emissions

Detecting and locating damage in structural components and joints that have high feature densities and complex geometry is a difficult problem in the field of structural health monitoring (SHM). Active propagation of diagnostic waves is one approach that is used to detect damage. But small cracks and damage are difficult to detect because they have a small effect on the propagating waves as compared to the effects the complex geometry itself which causes dispersion and reflection of waves. Another limitation of active wave propagation is that pre-damage data is required for every sensor–actuator combination, and a large number of sensors might be needed to detect small cracks on large structures. Overall, the problem of detecting damage in complex geometries is not well investigated in the field of SHM. Nevertheless, the problem is important because damage often initiates at joints and locations where section properties change.Recently there have been advances in the development of a passive structural neural system (SNS) for damage detection. The SNS uses electronic logic circuits to mimic the signal processing in the biological neural system. The advantage of the SNS is that highly distributed continuous sensors provide high sensitivity to damage, and the biomimetic signal processing and passive sensing tremendously simplify the instrumentation and wiring of the monitoring system. Also, the SNS operates continuously during operation of the structure to detect ambient Lamb waves or bulk waves that are produced by cracking, delamination, bearing damage, rotor imbalance, flow instabilities, impacts, or other material failure modes.In this paper, asymmetric Lamb wave propagation representing acoustic emissions (AE) is modelled based on a superposition of plate bending vibration modes. The simulation demonstrates that the SNS with four channels of data acquisition can localize damage within a grid of sensors irrespective of the number of sensors in the network. To experimentally validate the analysis results, a two-neuron prototype of the SNS was built and tested using a simulated AE source (a pencil lead break) on a riveted aluminium joint and on a composite plate. In both experiments, the SNS was able to localize simulated damages. These results indicate the feasibility of expanding the SNS to a large number of neurons.     

A cooperative robotic system based on multiple sensors to construct metallic structures

This paper describes a multisensorial robotic system to automatically construct metallic structures. Two robots must work cooperatively in the same workspace to perform the task. The robots are automatically guided using visual and force sensor information. A new time-independent visual force control system which guarantees the adequate robot behaviour during the construction of the structure is described. During the construction of the structure, a human operator works cooperatively with the robots in order to perform some tasks which cannot be automatically developed by the robots. To do so, a new human–robot cooperation approach is described in order to guarantee the human safety. The correct behaviour of the different subsystems proposed in the paper is demonstrated in Section 6 by the construction of a real structure composed of several metallic tubes and different types of pieces to join them.     

Damage detection of truss structures using two-stage optimization based on micro genetic algorithm

A simple and efficient two-stage optimization procedure is proposed to properly identify the sites and the extent of multiple damages in truss structures. In the first stage, the most potentially damaged elements are identified using an anti-optimization (AO) technique. In the second stage, a micro genetic algorithm (MGA) is performed to accurately determine the actual damage extents based on a priori knowledge from the first stage. The correctness and effectiveness of the proposed algorithm are proved by two illustrated test examples: the planar and space truss models with the numerically simulated data. The numerical results show the computational advantages of the proposed method to precisely determine the sites and the extent of multiple damages of truss structures.     

基于单激发端多接收端压电阵列的板内损伤检测

基于超声导波技术研究了板状结构的损伤检测。理论分析了平板中Lamb波的传播特点;利用有限元耦合场模拟方法模拟了平板中Lamb波的传播及裂纹对Lamb波的影响;根据有限元模拟结果,分析了裂纹尺寸对Lamb波传播的影响;为检测损伤的位置,建立了单激发端多接收端的压电阵列;结合概率成像算法,建立了损伤分布场,该分布场的成像结果直观地反映了损伤的位置和严重程度。     

Application of soft-thresholding on the decomposed Lamb wave signals for damage detection of plate-like structures

Effective application of the Lamb waves for structural health monitoring and damage identification intensively relies on the accurate damage-related feature extraction in the received signals. Most of existing signal processing methods extract the damage-related features from the time–frequency joint spectrum which requires a quite amount of effort. In this paper, the soft-thresholding process, based on different signal decomposition methods, is introduced to damage identification so that the damage-related signal features can be manifested more distinctively. By applying two popular signal decomposition methods (i.e., the discrete wavelet transform (DWT) and the empirical mode decomposition (EMD)), the signal of interest can be represented by a series of components with different frequencies. Since most noises exist in the high frequency range, it is feasible to alleviate noise by restricting the energy of high-frequency components. Finally, a denoised signal is synthesized using the corresponding reconstruction method. As an application, the soft-thresholding process is performed to detect a small crack on an isotropic aluminum plate under the white Gaussian noise contamination. The results, from both the numerical finite element simulation and experimental test, indicate that the soft-thresholding process is capable of effectively reducing the effect of noise, convincingly improving the sensitivity of damage identification, and discriminating relatively small damage.     

Estimation for bolt fastening conditions of thin aluminum structure using PZT sensors

This work presents a study on PZT impedance-based method, it is one of the NDT(Non-Destructive Technique). We study about assessment of the square-structure health condition by impedance-based technique using PZT patches, associated with longitudinal wave propagation. Health conditions of the square-structure controlled by bolt fastening condition is adjusted by torque wrench. In order to estimate the damage condition numerically, we suggest the evaluation method of impedance peak frequency shift.     

基于PZT的微驱动定位系统及控制方法的研究

介绍了基于PZT驱动的一维微动工作台.该微动台采用柔性平行板铰链机构,对其进行了出力和位移关系的分析,并且进行了ANSYS的有限元分析设计,求得了系统的固有频率和最大位移.其理论分析、有限元计算和试验测试结果的对比分析的一致性说明了理论分析的正确性和数值分析的可靠性.使用精密光栅进行微位移闭环检测,使用哈工大博实精密测控公司研制的压电陶瓷驱动电源.采用单神经元自适应PID控制算法对系统进行控制,单神经元具有自学习和自适应能力,而且结构简单易于计算;而传统的PID调节器也具有结构简单、调整方便和参数整定与工程指标联系密切等特点.推导了单神经元自适应PID控制器,并进行了实验,微位移为20μm时的响应时间为12ms,实验证明了该方法的有效性.     

Acoustic emission source localization in plate-like structures using least-squares support vector machines with delta t feature

To deal with the difficulties of current acoustic emission (AE) source location methods, such as classical approaches based on times of arrival and artificial neural networks based on AE signal features, the least squares support vector machines (LS-SVM) approach was attempted in acoustic emission (AE) source location of plate-like structures. The AE events were produced by pencil lead breaks, and the response wave was received by piezoelectric sensors. The time of arrival, determined through the conventional threshold-crossing technique, was used to prepare delta t feature for the input to LS-SVM. Training and testing data sets were generated for the case of plates monitored by four transducers and were adopted to validate the source location methodology using LS-SVM with delta t feature. Experimental tests were carried out, with the source positioned at predetermined points evenly distributed within the plate area. A satisfactory correlation was found between the actual source locations and those predicted by the trained LS-SVM model. The results of the experiments show that the LS-SVM-based location method, with delta t feature, permits an alternative effective positioning in plate-like structures.     

非线性模型的压电元件复合控制方法

研究了压电元件的非线性及其复合控制问题。依据压电元件全程及局部伸长和缩短的实验数据,提出了一种根据外环曲线参数及当前坐标值确定比例系数,进而确定内环伸长曲线的数学模型。实验表明,这种全面反映内、外环曲线的非线性数学模型对上升和下降过程的最大拟合误差在全程范围内分别为1.2%和2.0%。利用此模型,可在压电元件非线性外环曲线及目前电压-伸长量已知的情况下,求出其下一时刻上升或下降的路径。以此模型为基础,构造了一种压电元件前馈复合控制算法,在输入峰-峰值为4 μm位移的情况下,得到了280 Hz的闭环带宽。同普通PID控制算法相比,带宽提高了30%以上。     

微光学自适应技术中基于PZT薄膜的微反射镜工艺研究

介绍了微光学自适应技术中基于PZT(PbZrxT i1-xO3)薄膜的微反射镜单元及其制作工艺。该制作过程中用重掺杂硅片作为基底和下电极,采用了钛酸丁脂[(C4H9O)4T i]、乙酸铅[Pb(CH3COO2).3H2O]以及异丙醇锆[Zr(OCH(CH3)2 4.(CH3)2CHOH]为原料,通过溶胶-凝胶法(so l-gel)制作薄膜,薄膜厚度为纳米级。制成的PZT薄膜通过逆压电效应产生形变,对反射镜面局部进行微调,实现波前位相控制。     

方向性损伤的Lamb波压电线阵扫描成像与评估

对方向性损伤的Lamb波定量监测与评估方法进行了研究,采用了线性压电阵列布置方法,基于传感阵列各阵元捕获到的Lamb波损伤散射信号之间的相位情况,扫描方向性损伤反射信号的相位延迟信息,实现损伤和方向中心位置的判定。根据判定损伤方向,通过线阵旋转处理,研究改进了时间反转损伤成像评估方法,实现对方向性损伤的成像和评估。在铝板结构上的实验研究表明,该方法可以实现对损伤方位和尺寸的定量评估,较现有成像方法具有更好的抗干扰性和准确性。     

Magnetic-field sensors based on lead-doped lanthanum manganites

The possibility of using lead-doped lanthanum manganites as materials for magnetically sensitive elements of sensors is considered. Measurements of the penetration coefficient of a radio-frequency electromagnetic field as a function of the strength of a stationary magnetic field have been performed. Two variants of using cores made from lanthanum manganites are analyzed. It is shown that cores made from lead-doped lanthanum manganites allow measurements of magnetic fields to be performed in the range 80?4 × 10⁶ A/m. A sensitivity of up to 2.5 × 10^?2%/A/m can be achieved for fields of 80?8 × 10³ A/m.     

基于SVM的传感器非线性特性校正新方法

介绍了一种基于支持向量机的解决传感器系统非线性特性问题的新方法。支持向量机是Vapnik教授提出的基于统计学习理论的新一代机器学习技术，它有效地解决了小样本学习问题，因此该方法对样本数量没有特殊的要求。实验证明该方法有效，同时研究表明该方法也能用于其他系统的非线性校正。     

基于555多谐振荡器检测的碳纳米管湿敏传感器

针对使用仪器检测电容型碳纳米管湿度传感器的电容信号不利于传感器的使用与推广问题,提出了一种基于555多谐振荡式电路检测的电容型碳纳米管湿度传感器.首先,分析了传感器工作原理以及检测电路的检测原理,设计并制作了电容型碳纳米管湿度传感器;然后,分别使用仪器及检测电路对传感器进行测试;最后,对传感器响应时间进行了测试与分析....     

基于模板匹配算法的压电微位移器位移量原位测量技术

针对压电微位移器的位移量高精度测量需要,基于模板匹配算法提出了一种新颖的位移量原位测量方法。利用改进型的Twyman-Green干涉系统对压电微位移器的电压——位移特性曲线进行原位测量,根据模板匹配算法实时计算干涉条纹的移动量,进而得到对应的压电微位移量,并对相关实验测量结果进行了分析与验证。结果表明,该测量技术具有较高的测量效率以及较好的随机噪声抑制能力,其测量精度和分辨率均可达到纳米量级。该方法属于非接触式测量,具有较高的可靠性,在微位移的高精度原位自动测量中具有较好的实用性。     

Damage tolerance of cargo aircraft structures

The article reviews the main results of studying the area of the aircraft structure survivability conducted in the Research Organization “Central Aerohydrodynamic Institute-18” (TsAGI) during 1970–2012.     

微驱动定位系统及其在误差补偿机器人中的应用

介绍了基于偏摆误差补偿的高速高精度机器人系统组成及偏摆误差补偿原理,利用有限元分析软件ANSYS,设计了双层平行板弹性铰链结构、压电陶瓷(PZT)直接驱动的微位移工作台。采用模糊PI控制算法对微动工作台进行闭环控制,既利用模糊控制灵活、适应性强的优点,又利用PI控制精度高的优点。实验结果验证了模糊PI控制算法的有效性,采用微动工作台补偿偏摆误差,机器人的运动性能得到较大提高。