Experimental and theoretical study on vibration control of base-isolation with energy transducer

In order to evaluate the effects of structural control and energy transition for the base-isolation with energy transducer （BIET）, shaking table tests on a steel frame model （BIET system） with scale of 1：4 were conducted and the results were compared with the lead rubber beating （LRB） isolation system for the same model. Then numerical analysis of the system was carried out, in which the improved Wen analytic model was used to simulate the hysteretic law of transducers. The results show that the structural system can transform the partial earthquake energy to hydraulic energy ; furthermore, the effect of structural control can reach or be close to that of the LRB isolation system. The agreements between numerical analysis results and those of shaking table tests demonstrate the accuracy of the numerical model.

ACOUSTICAL TRANSMISSION LINE MODEL FOR ULTRASONIC TRANSDUCERS FOR WIDE-BANDWIDTH APPLICATION

An improved model for ultrasonic transducers is proposed. By considering only the first symmetric mode, each layer is represented as an acoustical transmission line in modeling of bulk wave transducers. In imaging applications, wide bandwidth and short time duration are required. The approach we have used consists of impedance matching the front face of the piezoelectric transducer to the propagating medium with a quarter wavelength impedance matching layer and inserting an nnmatching quarter wavelength acoustical layer between the rear face and backing material. A heavy backing would degrade the wide-band phenomena, but show a time duration shorter than 0.5 μs for imaging applications. PSPICE code of the controlled source model is implemented to precisely predict the performance of the matched transducers such as impedance, insertion loss, bandwidth and duration of the impulse response. Good agreement between the simulation and experimental results has been achieved.

Quiet Zone Design in Diffuse Fields Using Ultrasonic Transducers

This paper presents quiet zone design using ultrasonic transducers for local active control in pure tone diffuse fields. Most of researches in local active noise control used conventional loudspeakers for the secondary sources to produce quiet zones. Recently ultrasonic transducers have been used for the secondary sources to control the plane wave in active noise control. However there is no research related to active noise control in diffuse fields using ultrasonic transducers. Therefore this study uses ultrasonic transducers for the secondary sources to control the diffuse fields. The quiet zone produced using ultrasonic transducers in single tone diffuse fields has been analyzed through simulations in this work. The results showed that quiet zones created using ultrasonic transducers were larger than those created using conventional loudspeakers. This is due to the fact that the audible sound pressure produced by the ultrasonic transducers decays slowly with the distance. Therefore the secondary field created by an ultrasonic transducer could fit the primary field better and the larger zone of quiet could be obtained using the ultrasonic transducer. Also the audible sound produced by the ultrasonic transducers is directional;therefore the sound pressure amplification outside the quiet zones was lower.

Principle of adaptive optical current transducer on independent variables and its test

In order to improve the measurement precision of the optical current transducer （ OCT）, the adaptive optical transducing principle on independent variables is presented in this paper. And one of the adaptive optical current transducer（AOCT） on the independent variables of the output of the electricmegnet current transducer is introduced. According to IEC660044-8, the performance of AOCT was examined roundly applying the standard testing system authenticated by the state authority. The results indicate that the measurement precision of the AOCT has already reached 0. 2 class under the temperature from -40℃ to 60℃ ,which proves the feasibility of the method.

CONTROL OF ROBOT DRIVEN BY MULTIPLE ULTRASONIC MOTORS BASED ON ROBUST PARAMETER DESIGN

An ultrasonic motor （USM） is difficlt to be mathematically described because of its complex energy conversion and nonlinear parameters from increasing temperature and changing operating conditions. To achieve good performance of a three-joint robot directly driven by USM, according to the operating characteristics of USM, a new position-velocity feedback control strategy is proposed. In the control strategy, there are a total of 18 controller gains to he tuned. Through a series of ＂Design of Experiments＂ by the robust parameter design, an optimal and robust set of proportional integral derivative （PID） controller gains is obtained. Results show that the control strategy can achieve the best performance of the robot and the robust parameter design is effective and convenient to USMs.

PSPICE controlled-source models of analogous circuit for Langevin type piezoelectric transducer

The design and construction of wide-band and high efficiency acoustical projector has long been considered an art beyond the capabilities of many smaller groups. Langevin type piezoelectric transducers have been the most candidate of sonar array system applied in underwater communication. The transducers are fabricated, by bolting head mass and tail mass on both ends of stacked piezoelectric ceramic, to satisfy the multiple, conflicting design for high power transmitting capability. The aim of this research is to study the characteristics of Langevin type piezoelectric transducer that depend on different metal loading. First, the Mason equivalent circuit is used to model the segmented piezoelectric ceramic, then, the impedance network of tail and head masses is deduced by the Newton's theory. To obtain the optimal solution to a specific design formulation, PSPICE controlled-source programming techniques can be applied. A valid example of the application of PSPICE models for Langevin type transducer analysis is presented and the simulation results are in good agreement with the experimental measurements.

基于PROFIBUS-DP控制网络型船舶电站的控制实现

结合当前船舶电站控制所采用的现场总线组网技术介绍某三机组电站的控制实现。其控制核心是由主站可编程序控制器(PLC)与三台发电机同步保护装置(PPU)的从站构成的控制网络;主站PLC实现电站的逻辑控制,从站PPU监测三相电参数及控制发电机运行。主、从站通过PROFIBUS-DP协议实现数据共享。其中网络组态和电站控制逻辑的实现均在Step7V5.4中完成。实践证明其控制方式灵活、可靠、可移植性强,是目前船舶电站控制的主流之一。

Error Control Strategy in Ultrasonic Body Area Networks

Recently,ultrasonic waves had been introduced as the transmission medium in Body Area Networks(BANs) to reduce the incalculable damage caused by radio waves. However,the communications based on ultrasonic waves suffer from poor propagation of signals in air and consume too much energy. To address these limitations,firstly,we make the theoretical analysis to ensure ultrasonic waves could be used in BANs(UBANs). Then,we propose an error control strategy in UBANs to dynamically adjust the error control scheme and the Max-Retries based on the current channel state,which is called UECS. The UECS is based on IEEE 802.15.6 standards and considering the characteristics of ultrasonic waves in BANs. Simulation results show that UECS achieves better performance in terms of packet delivery ratio and energy consumption compared with the traditional strategies.

Comparison of smart panels for tonal and broadband vibration and sound transmission active control

This paper presents a comprehensive overview of the principal features of smart panels equipped with feed-forward and feedback systems for the control of the flexural response and sound transmission due respectively to tonal and to stochastic broadband disturbances.The smart panels are equipped with two types of actuators:first,distributed piezoelectric actuators formed either by small piezoelectric patches or large piezoelectric films bonded on the panels and second,point actuators formed by proof-mass electromagnetic transducers.Also,the panels encompass three types of sensors:first,small capacitive microphone sensors placed in front of the panels;second,distributed piezoelectric sensors formed by large piezoelectric films bonded on the panels and third point sensors formed by miniaturized accelerometers.The proposed systems implement both single-channel and multi-channel feed-forward and feedback control architectures.The study shows that,the vibration and sound radiation control performance of both feed-forward and feedback systems critically depends on the sensor-actuator configurations.

超声导波目标模式的激励方法研究

超声导波检测过程中不同模态导波信号与各类损伤之间的相互作用存在差异性,直接影响了损伤检测及定位成像结果的可靠性。因此,系统研究导波目标模式的激励方法从而获得理想的导波信号,有助于实现多类型损伤的精准检出以及获得高分辨率定位成像结果。该研究基于理论分析、有限元仿真和试验测量开展了超声导波目标模式的激励方法研究。理论分析导波目标模式激励的条件,并且构建二维多物理场仿真模型进行导波目标模式激励方法的验证。试验过程中将梳状换能器与锆钛酸铅压电陶瓷(piezoelectric ceramic, PZT)进行比较分析,结果表明,梳状换能器相较于PZT压电片具有良好的模式选择能力。另外,设计制作四分之一全向和全向梳状换能器,使其进行目标模式导波信号激励的同时实现传播方向的调控。

单向L(0,2)超声导波EMAT结构设计

超声导波在管道中传播时双向传播的特性以及端面反射回波的影响导致检测回波信号复杂难以分辨。依据电磁声换能器(EMAT)激发机理和纵向超声导波的波结构特性,设计了一种周期性永磁铁增强径向偏置磁场,从而增大洛伦兹力轴向分量、减小径向分量来控制激发单一L(0,2)导波;同时依据波叠加原理,通过控制相邻线圈线间距、激励电流方向和延迟时间等来选择纵向超声导波的激发方向。研究结果表明:当相邻激励线圈电流相反、线间距为λ/4,且延迟时间为T/4时,采用优化设计的周期性永磁铁可以实现管道中超声导波的方向控制,使得回波信号容易分辨,提高了管道的检测效率。

基于BP神经网络算法的超声电源频率追踪技术

超声振动系统主要由超声换能器和超声复合加工电源组成。其中超声换能器在加工过程中受到多种因素影响,会发生谐振频率漂移现象;超声复合加工电源需要输出对应频率的电信号,保证超声振动系统的稳定工作。为避免超声换能器损坏,设计一种基于BP神经网络算法的控制模型,通过分析超声电源运行历史数据来实现对超声电源输出频率的控制。利用Multisim对电路进行仿真,并通过试验采集理论谐振频率在25 kHz的超声换能器稳定工作时超声复合加工电源的输出信号,通过Matlab建模仿真来验证BP神经网络模型的控制精度和可靠性。结果表明,产生的模拟输出与实际输出频率最大误差不超过5%,有助于超声复合加工电源的稳定工作。

一种环链电动葫芦同步控制方法的研究与实现

本文对起重行业中常用的电动葫芦进行了介绍,分析了电动葫芦中常用的手电门控制和通过变频器控制方法的优点和缺点,针对实际舰船应用中舱室作业空间小、起吊高度低、被起吊物尺寸长重心不规则的特点,采用了一种对两台环链电动葫芦手电门进行改造的方式,实现了通过手操盒对两台电动葫芦进行双吊点同步起吊控制的目的。通过改造应用达到了理想的使用效果,节约了采购成本,为电动葫芦在小空间内作业的同步起吊控制应用提供了一定的参考。

基于超声相控技术的船舶吃水测量方法

为了解决内河船舶因超吃水引起的通航阻塞以及船舶安全问题,提出一种基于超声相控技术的船舶吃水测量方法。以超声相控技术为理论基础,通过控制一维线型超声相控阵列换能器发射聚焦声波,实现对目标船舶的相控扫描,获取各扫描点的回波信号;利用匹配滤波算法对回波信号进行滤波,改善信噪比;利用阈值法提取回波信号的时延;利用渡越时间法,计算出扫描点到各发射振元中心的距离,利用双曲交汇法计算出扫描点的空间坐标;分析回波信号幅值和扫描点位置坐标即可得到船舶吃水深度。为验证方法的可靠性,搭建了小比尺船模吃水测量实验系统,分析了110~140 mm不同吃水深度下的实验结果,计算了实际吃水与测量吃水间的相对误差。实验结果表明,使用匹配滤波法处理后的回波信号信噪比从15.26 dB提高至36.39 dB,实验时,最大相对误差出现在船舶实际吃水130 mm时,绝对误差为2.3 mm,相对误差为1.7%。

经颅超声刺激人脑海马的数值仿真研究

颞叶癫痫、阿尔兹海默症等神经系统疾病与大脑海马的异常放电相关。近年兴起的经颅超声刺激治疗脑疾病具有无创、能深入脑组织和可调控海马神经元放电的特点。该文基于128阵元相控阵换能器、人头颅CT数据、水体建立超声经颅刺激海马数值仿真模型,数值仿真优选适应于海马刺激的换能器结构参数,并结合电容模型,探究超声声学参数对海马神经元放电的影响。结果表明曲率半径90 mm、开口半径56 mm、阵元半径2.0 mm、频率0.9 MHz的128阵元相控超声换能器可形成适应于刺激人脑海马大小的焦域;且在超声频率为0.9 MHz时对海马神经元放电有较好的抑制作用;在较小的占空比和较低的空间峰值时间平均声强条件下对神经元放电有较好的抑制作用。

可控冲击波震源在地震勘探中的试验

近年来,国家对安全生产和环境保护的新要求越来越严格,尤其是炸药震源的使用限制条件越来越多。在安全生产形势严峻,火工品使用受限,现有的其他类型震源又无法满足地震勘探施工要求的区域,很大程度上限制了地震勘探方法的应用。可控冲击波技术是以脉冲功率技术为基础的新技术,该技术具有幅值和冲量可控,作业区域不受限制,可重复使用的特点。本文对可控冲击波技术及其发展历程进行简要介绍,并将现有可控冲击波设备改进后作为震源进行了激发地震波试验,对获取的地震资料进行定量分析,结果表明可控冲击波技术可以应用到地震勘探领域,同时提出了当前可控冲击波设备需要改进的技术问题。

基于三种通讯方式的纸张恒张力卷绕系统设计

针对高校实训要求,采用西门子S7-300系列PLC与变频器MM440,设计了具备Profibus-DP总线、USS串行总线和模拟量3种通讯方式的教学型纸张恒张力卷绕控制系统。描述了系统的结构,阐述了系统的控制方案,给出了针对3种通讯方式的系统硬件设计,采用编程组态软件Step7完成了系统的软件设计,并利用触摸屏对系统进行人机界面组态,实现了系统的人机信息交互。最后对系统进行调试,给出了系统运行时张力监控界面,证实了该设计的可行性。

Computer Technology in Modeling and Experiment Problems with Powerful Ultrasound in Air

The article presents an example of a device for focusing ultrasound through the air with the use of computer modeling technology and experimental data processing. The device is a matrix of 172 emitters operating at a frequency of 40 kHz, and the formation of the electronic unit of the ultrasound beam. Beam control on the software from your PC. Radiation pressure at the focal point was 57 Pa, and allows you to move light objects and feel the tactile effect of ultrasound. Present calculations the characteristics of the focused field and results of computer visualization of theoretical and experimental research.

基于ZigBee的智能照明控制系统设计与实现

现有的智能照明控制系统大多采用有线网络,不仅施工复杂,灵活性不够,而且影响了智能照明的应用。为此,提出了采用ZigBee协议设计智能照明控制系统,它不仅能降低系统成本,还能大幅度提升系统的性能。在深入分析现有智能照明系统的基础上,给出了相应的软硬件设计和组网算法。

基于PLC的种子包衣机自动控制系统设计与实现

为提高种子包衣质量,满足现代农业生产用种需求,研发了5BY-5型新一代种子包衣设备,并设计了以PLC为控制核心,液晶触摸屏为人机交流窗口,集编程、变频、液流监测、传感器等技术为一体的自动化控制系统。介绍了设备的主要结构、工作原理、控制系统硬件选型及抗干扰措施。采用Pro Tool/ProCS编制人机交流软件,在Step 7-Micro/WIN环境下采用梯形图方法编制系统监控软件,实现包衣作业的部件保护、精确计量、自动控制和人性化操作。检测结果表明,包衣合格率为99.2%,均匀性变异系数为0.6%,证明该设备能有效提高包衣质量。