磁致伸缩换能器应用研究进展

文章介绍了磁致伸缩材料的最新研究方向,阐述了磁致伸缩换能器的应用及近年来所取得的最新成果,分析了磁致伸缩换能器与压电陶瓷换能器相比所具有的优点,展望了其未来发展趋势。     

一种磁致伸缩微位移器机械结构设计探讨

以提高磁致伸缩换能器的电机转换效率为出发点,分析了影响磁致伸缩换能器工作性能的主要因素,讨论了在换能器机械结构设计中应考虑的主要问题和遵循的原则,提出了相应结构参数的确定思路和方法。研究结果对磁致伸缩换能器机械结构的合理设计具有一定的理论指导意义。     

超磁致伸缩稀土换能器测量系统

本文介绍了一种超磁致伸缩稀土换能器测量系统，并应用此系统对超磁致伸缩稀土换能器进行了测试，得到了满意的结果。     

PMN基电致伸缩材料的研究

在常规电子陶瓷制作方法的基础上,根据相容因子的考虑,结合热力学和动力学理论,通过不同掺杂离子的引入调节性能,优化工艺条件,制备出良好性能的电致伸缩材料,并仿真计算了相应的换能器。研究表明,碱土金属的添加,可以有效避免焦绿石相的出现,而不同的原料、温度、时间等工艺条件也影响PMN基电致伸缩材料性能。在反复多次实验的基础上,优化出性能较为优良的材料,测试表明,PMN电致伸缩材料的相对介电常数高达10000以上,介电损耗3%左右,电致回线的测试表明,PMN基电致伸缩材料的电致应变量大,偏场电压在2000V/mm时,应变量到达0.8×10-3,远高于PZT压电材料的应变量,为研制高性能的换能器打下了良好条件。     

静水压力对超磁致伸缩纵向换能器性能的影响

以超磁致伸缩纵向换能器为对象,开展了静水压力下换能器的性能实验研究,给出了研究结果,并指出了今后工作方向.     

稀土超磁致伸缩换能器的研制及其在桥梁检测中的应用

稀土超磁致伸缩材料是在磁场的作用下能产生巨大伸缩变形的一种新型功能材料，它的应用越来越受到广泛的关注，针对目前大型工程质量检测对声波无损评价系统震源的新要求，研制了稀土超磁致伸缩换能器，该换能器以大功率稀土超磁致伸缩材料作能量转换部件，具有能量集中、发射声波传播距离远、发射频率适中，容易与采集系统集成而实现自动检测控制，显著提高工作效率．最后以某桥梁声波CT无损评价为例说明其广泛的应用。     

稀土IV型弯张换能器研究

IV型弯张换能器低频发射时具有尺寸小、重量轻的特点,是一种常用的水下低频大功率声源。稀土超磁致伸缩材料相较于压电陶瓷拥有更大的应变量和能量密度,并且杨氏模量较小,可以有效降低换能器谐振频率。利用稀土超磁致伸缩材料作为激励材料,设计了一种低频IV型弯张换能器,对其静态磁场和动态磁场进行了分析,构建出双棒式磁路,并使用有限元分析软件进行了换能器的结构建模与计算。根据计算结果制作了稀土IV型弯张换能器样机,测试结果表明所设计的换能器与仿真结果吻合较好,水中谐振频率为370 Hz,最大声源级为196 d B,能够实现低频、大功率发射。     

偏置磁场强度对交叉线圈式扭转导波换能器换能效率的影响

交叉线圈式带状磁致伸缩扭转导波换能器偏置磁场强度直接影响换能器换能效率,为获得较佳的检测效果,需要研究偏置磁场强度对该换能器换能效率的影响。首先,从磁致伸缩效应出发,分析交叉线圈式带状磁致伸缩扭转导波换能器的工作原理。其次,在模态验证实验的基础上,分别对激励和接收换能器换能过程中偏置磁场的作用进行研究。实验结果表明随着偏置磁场强度的增大激励端和接收端换能器换能效率均先增大后减小。最后进行缺陷检测实验,当激励端和接收端均选择最佳换能区域时,对比模态验证实验,缺陷信号明显增大。该研究结果可为换能器的现场应用提供技术支持。     

稀土超声换能器特性研究

换能器是功率超声最基本最重要的器件，寻找、开发新材料是发展新型换能器的重要途径。稀土超磁致伸缩材料Tcrfcnol-D具有优良性能，本文采用四端网络法和有限元ANSYS软件对稀土超声换能器进行了理论设计与分析，并制作了一种单独稀土超声换能器振子和带变幅杆的稀土超声换能器，其性能与压电换能器相比显示出了独特的优越性。     

制备方法对钴铁氧体的微观结构和磁性能的影响

钴铁氧体由于其独特的磁特性,如较大的饱和磁致伸缩应变、较高的电阻率、较高的应变和压力敏感度等,被广泛应用于换能器、传感器等领域,是一类重要的磁性功能材料,其中,饱和磁致伸缩系数 λS和压磁系数(dλ/dH)max是决定磁致伸缩材料在实际应用中器件性能的关键参数,其与化学成分和合成方法等多种因素密切相关.综述了钴铁氧体的...     

Large-scale remotely interrogated arrays of fiber-optic interferometric sensors for underwater acoustic applications

The fiber-optic interferometric acoustic sensor array has established itself as a potential alternative to the conventional sonar array based on electroceramic transducers. In this paper, we discuss all the aspects of a large-scale fiber-optic interferometric sensor array. We review the basic operating principles of the fiber-optic interferometric sensor, signal processing, and multiplexing techniques, we present results from a noise model for a full size system, and we determine the benefit of incorporating a remotely-pumped optical amplifier in the array. As a practical example we describe the design and construction of a prototype array with 96 hydrophones incorporating a remotely pumped erbium-doped fiber amplifier, called the fiber-optic bottom mounted array, which is based on a dense wavelength division and time division multiplexed architecture. These arrays have applications in military sonar and seismic surveying.     

Standard and reference hydrophones in the infrasonic and sonic frequency ranges

Conclusions As indicated by these studies, the proposed symmetrical piston-type piezoelectric transducers provide an answer to the question of how to make standard quartz and reference piezoelectric ceramic hydrophones for the sonic and infrasonic frequency ranges.The quartz hydrophones can also be used to investigate the sensitivity of piezoelectric ceramic hydrophones as a function of temperature and static pressure.The piezoelectric ceramic transducers of the proposed design operate very effectively in the radiation mode.Translated from Izmeritel'naya Tekhnika, No. 5, pp. 66–68, May, 1973.     

Characterization of high-frequency, single-element focused transducers with wire target and hydrophone

In this paper, a wire-target technique was used for lateral beam profile measurements for a single-element, focused transducers in the very high-frequency range (35-60 MHz). Two wire targets made from 9-cm long tungsten wires with diameters of 8 microm and 20 microm were used as the pulse-echo targets to measure the lateral beam profiles at the focal plane of two single-element, focused transducers, a spherically focused 40 MHz transducer and a lens-focused in-house lithium niobate (LiNbO3) 60 MHz transducer. For comparison, measurements on the same transducers were performed by three small-aperture hydrophones with geometrical diameters varying from 37 microm to 150 microm. Tomographic reconstruction of the acoustic field from the spherically focused transducer also was conducted. Results obtained with the wire-target technique are comparable to those obtained with small-aperture hydrophones in characterizing lateral radiation patterns of a single-element, focused transducer in the high-frequency range (35-60 MHz). However, the wire-target method may overestimate pulse length because of the additional attenuation caused by the return path. Compared to small-aperture hydrophones, the wire-target technique is simpler and more cost effective. Its major advantage, however, is in the frequency range above 100 MHz in which commercial hydrophones are not yet available.     

声纳基阵信号模拟器实时软件的开发

声纳基阵信号模拟器是一种实用的、可近似仿真实际监测目标及使用环境的阵元级信号发生器。声纳基阵信号模拟器的使用将有效缩短数字式声纳的研制周期，大大减少湖试和海试的次数。文章中以通用信号阵列处理系统为运行环境，详细介绍了一种声纳基阵信号模拟器实时多任务系统的软件设计与开发过程，分析了该软件系统中所有基本任务的功能以及多任务之间的通信关系，并且最后给出了该实时多任务软件在通用信号处理机上的实现拓扑图。实践证明，该套软件功能完备，且具有很好的实时性和稳定性，非常适用于现代声纳工程领域。     

固态拖线阵和液态拖线阵的试验分析

拖曳线列阵声纳以低频、大孔径等特点而受到关注。作为湿端的主要组成部分,拖线阵的发展也比较迅速。由于应用较早,液态拖线阵技术已经比较成熟。相比于液态拖线阵,固态拖线阵具有自身的特点,因此近年来对固态拖线阵的研究也逐渐增多。为了比较两种成阵工艺对拖曳线列阵性能的影响,进行了湖试,通过对湖试数据进行分析,比较两种拖线阵中阵元一致性和拖线阵波束形成性能的差异。结果表明,在阵元一致性方面,液态拖线阵和固态拖线阵的性能基本相似;在波束形成性能方面,静态时两者性能无明显的差别;在拖曳状态下,固态拖线阵对拖曳时产生的噪声敏感性低,因而具有更好的波束形成性能。     

一种用于多载波水声通信系统的频域均衡算法

自适应均衡器是水声通信克服信道多径衰退、消除码间干扰(ISI)的主要手段。为了在不减少数据传输速率的情况下,有效提高系统的抗多径能力,提出了一种用于水声多载波通信系统的多通道频域自适应均衡算法。利用频域LMS算法,按照最小化频域均方误差的准则调节均衡器,从而获得最优的频域权系数。该算法一方面解决了在频域求得估计误差的问题,另一方面,和采用信道编码的方式相比,在不降低数据传输速率的情况下,有效提高了系统的性能,通过仿真试验和湖试对其性能进行了验证。     

PVDF reference hydrophone development in the UK-from fabrication and lamination to use as secondary standards

During the last 30 yrs, PVDF has been used extensively as a sensor material. Over this period, the GEC-Marconi Research Centre has developed a wide range of devices based on PVDF as a piezoelectric transducer material. The ability to create laminated structures has led to an enhancement in performance and has allowed innovative designs to be realized. This paper describes the development of the laminated PVDF structure and its benefits, such as increased sensitivity and improved signal to noise ratio. Examples of devices utilizing the lamination process are given in the form of both a bilaminar-shielded membrane hydrophone and a PVDF sonar hydrophone. Performance properties of both types of hydrophones are presented along with a discussion of their use as secondary standard hydrophones at the National Physical Laboratory (NPL).     

基于稳健Capon波束形成的阵形校正

由于受地形、海流和布放方法等的影响,声阵在布放后通常会偏离原定阵形。若直接利用原定阵形作方位估计,则各种高分辨方位估计算法的性能通常会退化甚至失效。因此,为了在实际中应用这些算法,必须对阵元的位置进行校正。RCB(Robust Capon Beamforming)是最近提出的一种稳健自适应波束形成算法,该算法直接对导向矢量进行估计,并用估计的导向矢量作波束形成,从而有效避免了因阵列流形失配而导致的算法性能下降。借用RCB的思想,提出一种新的阵形校正方法,该方法对导向矢量进行估计,然后用估计的导向矢量推导出阵元的位置。湖试结果表明了该校正方法的有效性。     

Real-Time Noncrosstalk Sonar System by Short Optimized Pulse-Position Modulation Sequences

Ultrasonic crosstalk is one of the main causes of false distance measurements that reduce the work efficiency of sonar sensors in mobile robots. To enhance the real-time performance of sonar systems, short digital pulse-position modulation (PPM) sequences are used to trigger ultrasonic transducers. Due to their properties of sharp autocorrelation and flat cross correlation, chaotic and pseudorandom number series are used to modulate pulse positions. A genetic algorithm is adopted to optimize the range of duration between pulses. Real experiments using Polaroid 600 series instrument-grade electrostatic transducers validate the suitability of the proposed method.     

A review on the development of piezoelectric composites forunderwater acoustic transducer applications

For future sonar transducer applications that emphasize the detection of acoustical signals in a hydrostatic mode, new piezoelectric composite materials have been developed. Ceramic-polymer composites having `1-3' and `0-3' connectivity patterns are shown to exhibit much higher sensitivities than conventional PZT ceramics. Glass-ceramic composites are free of aging, and have potential applications in standard transducers