基于激光回馈干涉系统的PZT迟滞特性测量

压电陶瓷迟滞特性对精密控制系统的精度具有重要影响,目前PZT迟滞特性的测量方法精度较低或者测量系统复杂,难以实现高精度测量。总结分析了目前测量压电陶瓷特性的方法,并使用基于激光回馈干涉原理的微片激光回馈干涉测量系统,利用物体表面的散射光对压电陶瓷的迟滞特性进行测量和分析。该方法不需靶镜,对被测对象要求较低,测量便捷,测量精度达到纳米量级,对精密控制系统中压电陶瓷的校准测量具有重要意义。     

Calibration of current measurement transducers in oversized calibration fixtures

A simple one-dimensional (1D) transmission line model has previously been used to derive improved estimates for the transfer impedance of current transducers at high frequencies by taking account of the finite reflections that occur at the ports of the calibration fixture. This approach is further extended to take account of the additional reflections that occur in the system when an oversized calibration fixture is used. The success of this method is also assessed, for frequencies up to 600 MHz, using measured and computed results for the current induced on a wire inside a cavity backed aperture illuminated by a nearby antenna.     

Calibration of current transducers at high frequencies

The transfer impedances of current transducers are estimated using a special calibration fixture, which is often assumed to be perfectly matched at its coaxial ports. However, the errors inherent in this approximation increase with frequency, making the measurement of cable currents increasingly inaccurate at higher frequencies. A one-dimensional (1-D) transmission line model is proposed to account for such errors in a calibration fixture of simple design by using additional measurements to quantify the mismatches in the system. This technique is validated using a numerical model of such a calibration fixture as well against experimental data and numerical predictions for the current induced on a wire inside a rectangular cavity due to an external source that is coupled into the interior via an aperture. It is concluded that the proposed approach provides improved results with a calibration fixture of simple design for frequencies up to at least 600 MHz     

On the Sensitivity Calibration of Implanted Pressure Transducers

A nonsurgical technique is described which permits the sensitivity calibration of implanted pressure transducers and associated telemetry links.     

Microfabricated cantilevers for measurement of subcellular andmolecular forces

We present two new microfabricated cantilever-beam force transducers. The transducers were fabricated from thin silicon-nitride films, and were used respectively to measure forces generated by two small-muscle preparations: the single myofibril, and the single actin filament in contact with a myosin-coated surface. A simple resonance method was developed to characterize the transducers. Because of the high reproducibility of lever dimensions and the consistency of the modulus of elasticity, few calibration measurements sufficed to characterize the stiffness of all the levers on a single wafer     

ADCP压电换能器及其校准方法研究进展

声学多普勒流速剖面仪(ADCP)在海洋学中应用广泛,是目前最主要的流速流量测量设备,其关键部件是压电换能器,用以发射和接收声学信号。该文结合ADCP仪器自身的发展,梳理了ADCP压电换能器及其阵列的研究进展,并对压电换能器及ADCP的校准方法进行简要概述。     

Sampled baseband correlators for in-air ultrasonic rangefinders

Conventional in-air ultrasonic rangefinders for robotic applications employ inexpensive analog signal processing techniques, based on threshold methods, to perform range measurements. Digital signal processing techniques using correlation methods can provide more accurate measurements, at the expense of greater system complexity and cost. The authors propose using a modified second-order bandwidth sampling technique for making data acquisition concomitant with frequency shift of the sampled narrow-band signals from in-air ultrasonic transducers to their equivalent baseband representations. The reduction of the frequency-analyzing interval allows one to conceive sampled baseband correlators for multiple receiving transducers with a complexity comparable to that of analog receivers. They develop a procedure of sensor calibration that is based on a stochastic model of time-of-flight noise; the effect of the receiver noise on the ranging accuracy is, thus, evaluated separately from the effect, due to environmental changes of the speed of sound. The simulation study and the experimental results obtained with their demonstration system offer promise for multichannel sampled baseband correlators, the time-of-flight estimation accuracy of which is close to the theoretical Cramer-Rao (CR) lower bound for signals in additive white Gaussian noise     

血管内超声换能器的研究现状与进展

血管内超声(IVUS)是通过心导管将微型化的超声换能器插入心血管腔内进行探测,再经电子成像系统显示心血管断面形态和血流图形的技术。面对商用IVUS换能器成像分辨率不足等问题,该文归纳并总结了近几年研究中多种提高IVUS换能器成像性能的方式,即增加换能器的频率、采用性能优越的压电材料以及改善换能器的结构等,并预测了IVUS换能器的发展方向。     

系统中传感器的一种模拟性能测试方法

为了测试多个传感器存在时系统运行稳定性的情况。基于已有的性能测试方法,模拟客户端与服务器端的交互操作来实现多个客户端的性能测试,提出了传感器的模拟性能测试方法,研究了一种方法为纯软件模拟传感器的测试,另外一种通过修改1个传感器的二次仪表程序,使其中与系统通信部分的数据参数化,根据服务器的请求反馈服务器需要的正确的结果。结果表明：对传感器二次仪表程序进行修改,能够实现模拟多个传感器在系统中运行的性能测试。     

Fitting transducer characteristics to measured data

There are no rules to select the best curve-fitting method for a given set of data. This problem is of great importance in measurement applications. Optimizing analog and digital methods for a transducer's characteristic interpolation or linearization is a field where constant research is being done, particularly since auto-calibration and self-test of intelligent transducers is a topic of major interest. We present an overview of classical methods for data interpolation and least mean squares regression. We make a comparative evaluation of the relative performance of polynomial and artificial neural networks approximations to measurement data with particular attention paid to the reduction of the required calibration set dimension to obtain a given accuracy     

Visualisation of ultrasonic waves launched by PVF2 piezofilm transducers

The single-cycle wavefront propagated into water by PVF2-film transducers is visualised by a stroboscopic Schlieren system, and is compared with that from conventional piezoceramic probes. For the film transducers, no edge waves can be observed, nor are they apparent in the transmit-receive impulse response.     

基于ARM的汽车防盗系统的设计

基于先进的ARM技术,采用无线通信网络以及全球定位系统提出了一种网络型智能汽车防盗系统.系统由三星公司的S3C44B0微处理器、MC55无线通信模块、GM-X205型GPS接收机以及防盗传感器组成.微处理器对采集到的传感器信号进行处理,当确认有盗贼分子盗车后,切断汽车油路的同时给车主手机和监控中心发送汽车被盗的信息以及定位信息,真正解决了汽车的安全问题.     

System level simulation of a micro resonant accelerometer with geometric nonlinear beams

Geometric nonlinear behaviors of micro resonators have attracted extensive attention of MEMS (microelectro-mechanical systems) researchers, and MEMS transducers utilizing these behaviors have been widely researched and used due to the advantages of essentially digital output.Currently, the design of transducers with nonlinear behaviors is mainly performed by numerical method and rarely by system level design method.In this paper, the geometric nonlinear beam structure was modeled and established as a reusable library component by system level modeling and simulation method MuPEN (multi port element network).A resonant accelerometer was constructed and simulated using this model together with MuPEN reusable library.The AC (alternating current) analysis results of MuPEN model agreed well with the results of architect model and the experiment results shown in the existing reference.Therefore, we are convinced that the beam component based on MuPEN method is valid, and MEMS system level design method and related libraries can effectively model and simulate transducers with geometric nonlinear behaviors if appropriate system level components are available.     

Liquid velocity measurement using interdigital transducers

A system for measuring the velocity of a flowing liquid is presented using three interdigital transducers, one of which is used for the radiation of the compressional wave into the liquid. The velocity is estimated from the measurement of the output voltage corresponding to the phase difference between two output signals detected at the output transducers, mounted on the same surface opposite to the surface with the input transducer.     

智能防丢车和车辆定位系统

基于高级RSIC微处理器（Advanced RSIC Machine,简称ARM）技术,采用无线通讯网络及GPS（Global Positioning System）全球定位系统提出了一种网络型汽车监控系统,该系统由Atmel的AT91RM9200微处理器、SIM300无线模块、GPS接收机及防盗传感器等组成。微处理器对收集到的信息进行处理,确认后可锁定汽车油箱阀门禁止漏油以迫使汽车安全停止,并同时向车主手机和网络服务器发送信息,以实现汽车监控,防止被盗。     

一种频率可调超声波发生器设计

不同清洗物所需的清洗频段不同,需要接入的超声波换能器也不同。为了提高超声波发生器对不同频段换能器的适应性,设计了一种由上位机进行频率给定、锁相环电路进行频率跟踪的闭环控制系统。整个系统由STM32主控制器产生脉冲宽度调制(PWM)脉冲信号,控制EXB841优化驱动电路,驱动高频全桥逆变电路;通过阻抗匹配和输出电流的检测,保证作用于换能器输出的功率值最大。同时对于不同频段的超声波换能器,需要调整给定输入,保持发生器在频率基准值的一定范围内进行频率跟踪。超声波换能器测试样机工作频率点为28.8 kHz,最大功率1 500 W,将本系统接入后谐振频率保持在28.8 kHz左右,输出功率近似为最大值。经测试,该系统对于工作频率点为20~40 kHz的超声波换能器都具有较好的适应性。     

A comparison of response characteristics of airflow and pressuretransducers commonly used in rhinomanometry

Although the ranges in which pneumotachographs evidence linear output to static flows are documented in the literature, measures of output reliability or the stability of calibration functions resulting from the input of dynamic nonsinusoidal flows (such as those which occur during nasal breathing) have not been investigated. Furthermore, it is not known whether the type of requisite pressure transducer used in conjunction with the pneumotachograph influences the pneumotachograph's linearity, output reliability, or dynamic response. To provide information on these points, we determined the dynamic and static responsiveness of three pneumotachographs commonly used in rhinomanometry, in combination with three requisite pressure transducers. In general, a) output reliability depended on the pneumotachograph/pressure transducer combination and was not readily predictable from the reliabilities of the individual components, b) heating increased pneumotachograph reliability, and c) differences in accuracy existed among transducer combinations at high, but not low, flow frequencies. In addition, results from the calibration syringe study (in which the pneumotachograph is calibrated with dynamic non-sinusoidal flows) suggested that: a) a single calibration factor, as supplied by most pneumotachograph manufacturers, is inadequate for accurately measuring the full range of flows produced in sniffing and breathing tasks; b) the measurement of complex waveforms, even when the dominate frequencies of such waveforms are low, requires pneumotachographs that accurately respond to relatively high frequencies; and c) the use of dynamic nonsinusoidal flows (as opposed to static flows) to calibrate pneumotachographs results in a calibration function with higher reliability.     

油水两相流电容层析成像系统传感器仿真分析

以12电极油水两相流电容层析成像系统为研究对象,分析了电容层析成像系统的工作原理及数学模型,针对油水两相流电容层析成像系统的特性,采用有限元方法对其传感器灵敏度分布(敏感场)进行仿真分析和计算,采用不等间距网格剖分提高了计算精度,并分析了各个传感器结构参数对传感器性能的影响,为传感器研制提供参考依据.     

基于环形相控阵的超声CT成像系统的设计

为了更好地实现乳腺癌的早期精确诊断,设计了一种基于聚焦环阵的新型超声CT成像系统。256个电容式微加工超声换能器(CMUT)环形分布于乳腺四周,采用64个换能器发射,对面64个换能器接收的方式进行,在COMSOL中依次进行256次仿真来实现环形扫描。根据超声相控阵原理进行发射聚焦后,采用滤波反投影算法进行图像重建。聚焦到乳腺外部时,重建偏差值小于0.05%,聚焦到4号肿瘤时,该区域重建偏差值仅为0.002%。实验结果表明,该系统可以用于乳腺癌的早期精确诊断,且能提高内部肿瘤的检测质量。     

30～1 000 MHz天线系数的校准

论述了30～1 000 MHz电磁兼容天线校准系统的建立和实际操作步骤,并给出了测试结果.通过试验,对双锥天线和对数周期天线进行了校准,其数据与原厂的校准数据非常接近,证明该校准系统完全符合天线校准的要求,并介绍了自动测试的方法.