Dynamic wireless passive strain measurement in CNC turning using surface acoustic wave sensors

Wireless, passive and dynamic surface acoustic wave (SAW) strain sensors are especially advantageous in applications with harsh environments where complex force measurements are required. High frequency multiple axis force measurement during machining processes typically requires state-of-the-art piezoelectric dynamometer technologies. Integrating dynamometers and their associated measurement chains into the machining environment typically requires significant modification to the machine structure. In this paper, SAW sensors were developed for process monitoring operations. Single-axis continuous and interrupted cutting investigations were carried out using the SAW technology installed on cutting tool holders demonstrating high dynamic bandwidth strain measurement. SAW dual-axis oblique cutting measurements were carried out where four SAW sensors were set up as two differential pairs each measuring a single axis of applied force. Improvements in sensitivity and cross-talk compensation has been realised. High-frequency wireless passive realtime process signals are presented from a passive wireless SAW force measurement system successfully integrated into an LT15 Okuma machining centre. The paper aims to present wireless passive SAW technology as a potentially platform changing approach for process and tool condition monitoring applications in the future.     

基于声表面波器件的无源传感器的研究

利用声表面波器件的高频压电转换特性,研究设计了一种可实现无线访问的时间延迟型无源传感器,为提高回波信号的信噪比,在ＳＡＷ器件的设计中,采用了一种并联式的新型结构以替代传统的共线式结构。利用一套射频访问系统,本文重点针对器件的力敏特性进行了实验研究。实验表明,合理地设计器件中ＩＤ－Ｔａｇ与反射栅的参数,可稳定地测出器件上ＳＡＷ的传播参数,测量结果不受器件与访问系统间距离的影响,利用这一原理,可进上步     

声表面波器件在无线传感系统中的应用

有许多应用场合,无法实现传感器信息的有线传输;在某些特殊场合,迫切需要降低安装传感器的配线总量,降低成本。无线传感系统是传感器的一个研究热点,与基于调制解调的无线传感器相比,基于声表面波的无线传感器在许多特殊场合日益显示出其必要性和重要性。简要介绍了目前国际上的各种无线无源式声表面波传感器的国内外发展现状,具体讨论了无线谐振型声表面波传感器的原理以及在传感器设计、制作过程中提高传感器灵敏度的一些措施,以及声表面波器件用于目标辨识以及常规变阻抗型传感器信息无线传输中的原理和应用。     

A new method for wideband characterization of resonator-based sensing platforms

A new approach to the electronic instrumentation for extracting data from resonator-based sensing devices (e.g., microelectromechanical, piezoelectric, electrochemical, and acoustic) is suggested and demonstrated here. Traditionally, oscillator-based circuitry is employed to monitor shift in the resonance frequency of the resonator. These circuits give a single point measurement at the frequency where the oscillation criterion is met. However, the resonator response itself is broadband and contains much more information than a single point measurement. Here, we present a method for the broadband characterization of a resonator using white noise as an excitation signal. The resonator is used in a two-port filter configuration, and the resonator output is subjected to frequency spectrum analysis. The result is a wideband spectral map analogous to the magnitude of the S21 parameters of a conventional filter. Compared to other sources for broadband excitation (e.g., frequency chirp, multisine, or narrow time domain pulse), the white noise source requires no design of the input signal and is readily available for very wide bandwidths (1 MHz-3 GHz). Moreover, it offers simplicity in circuit design as it does not require precise impedance matching; whereas such requirements are very strict for oscillator-based circuit systems, and can be difficult to fulfill. This results in a measurement system that does not require calibration, which is a significant advantage over oscillator circuits. Simulation results are first presented for verification of the proposed system, followed by measurement results with a prototype implementation. A 434 MHz surface acoustic wave (SAW) resonator and a 5 MHz quartz crystal microbalance (QCM) are measured using the proposed method, and the results are compared to measurements taken by a conventional bench-top network analyzer. Maximum relative differences in the measured resonance frequencies of the SAW and QCM resonators are 0.0004% and 0.002%, respectively. The ability to track a changing sensor response is demonstrated by inducing temperature variations and measuring resonance frequency simultaneously using the proposed technique in parallel with a network analyzer. The relative difference between the two measurements is about 5.53 ppm, highlighting the impressive accuracy of the proposed system. Using commercially available digital signal processors (DSPs), we believe that this technique can be implemented as a system-on-a-chip solution resulting in a very low cost, easy to use, portable, and customizable sensing system. In addition, given the simplicity of the signal and circuit design, and its immunity to other common interface concerns (injection locking, oscillator interference, and drift, etc.), this method is better suited to accommodating array-based systems.     

基于声表面波谐振器和延迟线的编码型无源无线阵列传感器

提出了一种新型延迟编码式谐振声表面波无源无线传感系统。该传感单元由单端口谐振器和延迟线组成，激励信号采用间歇正弦脉冲串信号。响应为一变化的振荡波形，该信号的频率与声表面波器件固有频率相等。该传感阵列系统利用不同延迟线构成编码器不仅有谐振式无源无线传感器距离远的优点，而且，还具有延迟型大规模编码的优势。该方法提高了传感系统遥感测量的距离、灵敏度和信噪化，也为该声表面波阵列传感器的广泛应用提供了保证。     

基于自适应Kalman滤波的SAW测温数据纠错方法

在无源无线SAW测温系统实际应用中,阅读器接收到的信号往往受到其所处环境电磁波的干扰。这些干扰将会使阅读器得到错误的测量数据。温度变化趋势和测量噪声时变的特点也给系统建模以及噪声估计带来了困难。针对实际应用中存在的问题,在Kalman滤波的基础之上,提出了一种新的自适应算法。该算法采用多项式预测的方法建立温度测量的时变系统模型,根据当前及历史测量值,自行调整预测模型参数,避免因模型不准确造成Kalman滤波效果严重下降的问题;通过对测量数据小波变换的方法,实时估计测量数据噪声方差,克服未知观测噪声的条件下精度下降的问题;当测量数据受到干扰时,测量值与纠错值之间的差值不满足高斯分布,通过对差值统计特性的分析,对测量数据进行错误数据判别与剔除,有效地抑制干扰对温度测量的影响。将这种自适应Kalman滤波算法应用到无源无线SAW测温系统中,无源无线SAW温度传感器测温实验的结果验证了该算法能有效地纠正粗大误差,提高测量系统的精度。     

可调谐F-P腔进行锥形光栅反射带宽解调的应力测量方法

理论分析和实验验证了通过对锥形光栅反射谱进行带宽解调来获得环境应力/应变的可行性,提出了对锥形光栅反射谱采用可调谐F-P腔进行带宽解调的方法,通过应力加载实验对该带宽解调方法进行了验证,并取得了较好的反射带宽解调和应力测量效果。实验证明,该测量系统实现了对温度变化不敏感的应力测量,同时具有较高的灵敏度,应力测量精度为0.060 N。在进一步进行锥形光栅中心反射波长解调的基础上,该方案可实现温度和应力的同时测量。     

Wireless sensor marking and temperature measurement with SAW-identification tags

A wireless sensor marking system based on surface acoustic wave (SAW) identification tags is presented. The proposed solution is compatible with existing measurement systems and can be applied directly in the sensor or by means of a unique sensor identification cable (SIC). The SAW tag operates completely passive, and withstands temperatures up to 400 °C as well as shocks up to 35 000 m/s². It contains a unique serial identification number, which is encoded on the high-temperature stable SAW device by means of metallic reflector gratings. The interrogation unit uses the sensor cable for transmission but is not directly connected to it, thus the identification system can be even used with high impedance measurement equipment, e.g. charge amplifiers. Interrogation is done in frequency-domain based on well-known radar principles and is realized in a low-cost add-on circuit to the existing sensor evaluation circuitry. Furthermore, by simply enhancing the evaluation software, a temperature measurement of the SAW tag itself, and thus often of the sensor or the sensor environment can be done without additional hardware requirements.     

基于声表面波原理的切削力测量智能刀具研究

切削力的测量对于监测加工过程以及获得高精度的零部件具有重要作用,为实现自适应加工提供切削状态参数。研究了一种基于声表面波原理的切削力测量智能刀具。能在切削加工中实现主切削力的实时测量,并具有无线、无源的测量优势,能够适应复杂的加工环境。建立了切削力与声表面波谐振器石英基片应变的关系模型,分析了声表面波谐振器谐振频率,得到了切削力与声表面波谐振频率偏移量的关系。实验结果表明,基于声表面波原理的切削力测量智能刀具能够实现切削力的实时测量。     

微机械氮化硅梁谐振式压力传感器

报导一种新型的电热激励、压阻拾振的氮化硅梁谐振式压力传感器。器件采用微电子机械加工技术和键合技术研制。谐振频率85kHz,空气中品质因素Q值接近1000,在真空中达到40000。采用闭环自激振荡方式测定压力传感器的压力特性,压力测试范围0－400kPa,灵敏度23．8Hz/kPa。     

Effects of wireless packet loss in industrial process control systems

Timely and reliable sensing and actuation control are essential in networked control. This depends on not only the precision/quality of the sensors and actuators used but also on how well the communications links between the field instruments and the controller have been designed. Wireless networking offers simple deployment, reconfigurability, scalability, and reduced operational expenditure, and is easier to upgrade than wired solutions. However, the adoption of wireless networking has been slow in industrial process control due to the stochastic and less than 100% reliable nature of wireless communications and lack of a model to evaluate the effects of such communications imperfections on the overall control performance. In this paper, we study how control performance is affected by wireless link quality, which in turn is adversely affected by severe propagation loss in harsh industrial environments, co-channel interference, and unintended interference from other devices. We select the Tennessee Eastman Challenge Model (TE) for our study. A decentralized process control system, first proposed by N. Ricker, is adopted that employs 41 sensors and 12 actuators to manage the production process in the TE plant. We consider the scenario where wireless links are used to periodically transmit essential sensor measurement data, such as pressure, temperature and chemical composition to the controller as well as control commands to manipulate the actuators according to predetermined setpoints. We consider two models for packet loss in the wireless links, namely, an independent and identically distributed (IID) packet loss model and the two-state Gilbert-Elliot (GE) channel model. While the former is a random loss model, the latter can model bursty losses. With each channel model, the performance of the simulated decentralized controller using wireless links is compared with the one using wired links providing instant and 100% reliable communications. The sensitivity of the controller to the burstiness of packet loss is also characterized in different process stages. The performance results indicate that wireless links with redundant bandwidth reservation can meet the requirements of the TE process model under normal operational conditions. When disturbances are introduced in the TE plant model, wireless packet loss during transitions between process stages need further protection in severely impaired links. Techniques such as retransmission scheduling, multipath routing and enhanced physical layer design are discussed and the latest industrial wireless protocols are compared.     

编码式谐振SAW无源无线温度传感阵列系统

提出了一种新型编码式谐振声表面波无源无线温度传感系统。该传感系统采用间歇正弦脉冲串信号作为无线激励信号，而经谐振式声表面波器件延迟后的反射波是一瞬时变化的振荡波形，该反射信号的频率与声表面波器件固有频率相关。温度改变，其反射信号的频率也发生变化。该传感阵列系统利用不同延迟线构成编码器，可实现大规模的传感器构造。该方法不仅有谐振式无源无线传感器距离远的优点，而且，还具有延迟型大规模编码的优点。该法还可用于无源无线的目标识别。     

新型驻波模式的声表面波MEMS-IDT陀螺仪

文中提出了一种新型基于驻波模式的声表面波(SAW)MEMS-IDT陀螺仪,包括一个谐振腔内驻波反节点位置分布金属点阵的两端SAW谐振器和一组平行于谐振器设置的双延迟线型SAW振荡器.SAW谐振器形成稳定的驻波,由于旋转利用分布的金属点阵产生Coriolis力并激发垂直于旋转方向的二次SAW,并与SAW延迟线上传播的SAW产生相干效应,以此改变声波速度,从而导致延迟线型振荡器的频率输出发生变化.双延迟线振荡器结构有效地降低由于外围温度等干扰的影响.单相单向换能器(SPUDT)以及梳状换能器结构用于构建SAW延迟线,以改善振荡器的频率稳定性.所研制的用于构建陀螺仪的80 MHz两端谐振器以及延迟线器件的测试结果表现出低损耗等特点.利用旋转台对所研制的SAW陀螺仪进行性能评价,在0～1 000 deg/s范围内表现出良好的灵敏度(119 Hz/(deg·s))以及线性度性能.     

Data compression in wireless sensors network using MDCT and embedded harmonic coding

One of the major applications of wireless sensors networks (WSNs) is vibration measurement for the purpose of structural health monitoring and machinery fault diagnosis. WSNs have many advantages over the wired networks such as low cost and reduced setup time. However, the useful bandwidth is limited, as compared to wired networks, resulting in relatively low sampling. One solution to this problem is data compression which, in addition to enhancing sampling rate, saves valuable power of the wireless nodes. In this work, a data compression scheme, based on Modified Discrete Cosine Transform (MDCT) followed by Embedded Harmonic Components Coding (EHCC) is proposed to compress vibration signals. The EHCC is applied to exploit harmonic redundancy present is most vibration signals resulting in improved compression ratio. This scheme is made suitable for the tiny hardware of wireless nodes and it is proved to be fast and effective. The efficiency of the proposed scheme is investigated by conducting several experimental tests.     

A feasibility study of damage tracking through the diffusive communication of wireless sensors

The objective of this paper is to investigate the feasibility of wireless sensors in the development of an autonomous structural health monitoring system. A collaborative searching algorithm is developed such that massively deployed wireless sensor nodes in a structure conveniently comprise a group and constitute a damage-surveillance perimeter. Wireless sensors in this perimeter spontaneously activate themselves for damage-tracking tasks by networking with neighboring sensors. When the damage-sensitive parameter that is measured by a sensor node exceeds a certain threshold, the process of damage-tracking begins. The proposed damage-tracking algorithm does not require any type of global control. Instead, sensor-networking and a pairwise-comparison algorithm that is implemented at each sensor node allows collaborative decision-making for tracking the changes, such as local strain, in structural properties. The extant autonomous, damage-tracking algorithms have been demonstrated through only numerical simulations for a single-damage case. Here, the study is further expanded to address the problem of simultaneously tracking multiple instances of damage in three-dimensional space by using improved algorithms for sensor networking. An event-based task-executing functionality of individual sensor nodes is successfully implemented and verified using four wireless strain sensors that are mounted on a cantilevered beam structure. Experimental results reveal that the overall capability of wireless sensor nodes is functional enough to enable a wireless-based autonomous structural health monitoring system.     

激光在机测量系统的实现

为了能在加工航空发动机关键零部件(如叶片)等复杂曲面零件的过程中实现快速在机测量,研制了非接触式激光在机测量系统。分别介绍了测量系统的工作原理,机械结构和电控系统。该系统主要由激光测头、无线传输电路、可充电锂电池、转接基座、刀柄和外壳等部分组成。为了实现机床的加工模式与测量模式之间的快速切换,其采用刀柄式的安装方式,从加工叶片切换到在机测量时,机床只要运行换刀程序,即可实现叶片加工到叶片测量的转换。此外文中还针对在机测量系统的电控部分研制了通过无线传输的数据采集系统。为了验证所研制的在机测量系统的实用性和有效性,在五轴叶片加工中心上进行了叶片截面测量实验,结果显示其测量精度为20μm,测量时间为10min。验证结果表明所研制的激光在机测量系统能够高效精确地完成叶片型面的测量任务。     

基于声表面波技术的无线测量系统研究

本文分析了目前传感器发展的现状和声表面技术的应用状况,介绍了声表面波传感器的两种工作模式的工作原理以及在研究过程中所采用的延迟线型声表面波测量系统的工作原理。同时利用这个系统进行了测量应变实验,理论和实验取得了较好的一致性。且具有较高的灵敏度。     

Experimental study on a noncontact method using laser displacement sensors to measure vibration stress in piping systems

This study presents a noncontact measurement method of vibration induced stress (vibration stress) using multiple laser displacement sensors and clarifies its applicability to piping vibration. In the beam structures such as piping, the stress due to bending deformation can be caused by vibration. In the presented method, the vibration displacement in the beam structures induced by the bending deformation is measured at three different locations using laser displacement sensors in a noncontact manner and the vibration stress is estimated by a simple calculation based on the beam theory. First, an applicability validation of the presented method was done by a vibration test using a cantilevered beam plate. This validation was done by comparing measurements by the presented method and the conventional method using strain gauges. Next, an experimental validation was conducted by the vibration test using a pipe specimen, and the applicability to the piping vibration was confirmed.     

A technique to measure hydrogen absorption in isolated nanometer structures

We describe an apparatus assembled to measure hydrogen absorption on a monolayer of isolated nanometer scale entities. Utilizing inexpensive and readily available high frequency surface acoustic wave (SAW) sensors we achieve a sensitivity of 4 pg, sufficient to detect hydrogen uptake at less than 1% in nanogram level samples of such entities at room temperature. Results of hydriding rare earth metal nanoparticles and a transition metal-carbon complex measured with 315 MHz SAW resonators are presented. However, the design of our apparatus is general and can be used with a wide variety of commercial SAW sensors.     

基于LVDT的光学器件相对位姿检测方法

针对光学精密装配工艺特点,提出一种基于LVDT的三维相对位姿检测方法.采用4个对称分布的LVDT检测光学装配过程中球面镜与谐振腔体的位姿关系,根据LVDT的读数推导得出球面镜与谐振腔体的相对位姿.设计采用集成信号调理芯片AD598的LVDT处理电路作为位姿检测的控制系统,通过实验得出LVDT微位移检测的分辨率为0.1 μm,重复检测精度为±0.3μm,并能较好地跟踪方波及正弦波信号.采用PID算法实现球面镜的快速位姿定位.实验结果表明:当球面镜的加工及安装误差在允许范围内时,位姿检测系统可以在25 s内完成球面镜相对于谐振腔体的位姿调整,最大距离误差为0.5 μn,最大角度误差为8″,充分验证了基于LVDT相对位姿检测方法的可行性.