An approach to design a high power piezoelectric ultrasonic transducer

Application of ultrasonic waves has been considerably progressed during the last decade and piezoelectric ceramics have had a common use as the driving source of such waves. However, there is not enough documented information on design and technology of manufacturing a high power ultrasonic transducer. In this paper, an attempt has been made to analyze the stress produced along the oscillating PZT employed ultrasonic head by applying the principles of acoustic wave propagation. Then, based on such analysis, general principles of PZT transducer design, excited by a DC-biased alternating electrical source, has been derived and finally a typical such transducer has been designed, manufactured and tested. By employing finite element modal analysis, the resonance frequency of the transducer was determined and compared with the experimental results. It was concluded that, the constitutive piezoelectric equations referred to in most sources and books are not valid for analyzing the acoustical dynamic stress in ultrasonic transducers. Instead, the analysis should be done with considering the dynamic behavior (elastic, damping and Inertia factors) of the problem.

Fabrication,modelling and use of porous ceramics for ultrasonic transducer applications

Porous ceramics are of interest for ultrasonic transducer applications. Porosity allows to decrease acoustical impedance, thus improving transfer of acoustical energy to water or biological tissues. For underwater applications, the d_hg_h figure of merit can also be improved as compared to dense materials. In the case of high frequency transducers, namely for high resolution medical imaging, thick film technology can be used. The active films are generally porous and this porosity must be controlled. An unpoled porous PZT substrate is also shown to be an interesting solution since it can be used in a screen-printing process and as a backing for the transducer. This paper describes the fabrication process to obtain such materials, presents microstructure analysis as well as functional properties of materials. Modelling is also performed and results are compared to measurements. Finally, transducer issues are addressed through modelling and design of several configurations. The key parameters are identified and their effect on transducer performance is discussed. A comparison with dense materials is performed and results are discussed to highlight in which cases porous piezoceramics can improve transducer performance, and improvements are quantified.     

变频器在热轧除鳞泵控制系统中的应用

介绍了变频器在轧钢厂热轧除鳞泵控制系统中的应用,分析了冶金企业环境中变频器的选用要求,阐述了热轧除鳞泵控制系统的构成和工作模式,并对该系统的高效性和应用效果进行了分析说明。     

圆盘摩擦泵在水轮发电机轴承油封中的应用

针对立式水轮发电机轴承的漏油问题,分析了产生漏油的原因;结合理论计算,在挡油简体上加环形板,使之与轴领内壁形成圆盘摩擦泵。使简体上沿原先的泄漏流动变为由外向内的泵送流动。实践证明,所采取的措施得当,轴承漏油问题得以圆满解决。     

The design and characteristics of ring type linear ultrasonic motor for X-Y stage

In this paper, the linear ultrasonic motor is newly designed to apply for the actuator of X-Y stage, its vibration mode is analyzed by FEM software, and its characteristics are studied as a function of the inner diameter of the elastic body. As a result from FEM analysis, the stator simultaneously vibrates to radial and bending vibration mode. Based on the result, ring-type linear ultrasonic motors are fabricated according to its inner diameter and its resonant frequency is measured by impedance analyzer. As inner diameter increases, its resonant frequency and velocity decreases. When its inner diameter, input voltage and driving frequency are 10 mm, 20 Vpp and 68.6 kHz, the velocity of the moving body is about 100 mm/s.     

一种高频超声波换能器驱动电路的设计

本文设计了一种高频超声波驱动电路,此超声波换能器驱动电路的发射频率高达1MHz,而目前包括集成电路发射模块和分立元件组成的驱动电路发射频率多为40kHz。本电路主要用于对精度要求极高,如基于超声波的精确测量、美容器等领域。此电路为超声波应用于更多的领域提供了必要的准备。     

一种实用型继电保护用光学电流传感器的设计

论述了光学电流传感器的工作原理并通过实验对其可行性进行了验证 ,证明并指出有源型光学电流传感器以其光路简单、绝缘强度高、线性度好、反应速度快、无磁饱和、体积小、重量轻、实用性强等特点 ,有可能成为新一代数字化继电保护用电流传感器的发展方向     

基于正交试验理论的接地扁钢缺陷检测电磁超声换能器优化设计

接地网是保障电力系统运行的重要设施,需要及时地开展接地扁钢的缺陷检测。然而,目前的检测方法在准确性、效率等方面依然存在不足。电磁超声导波检测方法可以在不开挖的条件下,利用非接触的优势实现地网的检测,具有一定的优势。本文针对接地扁钢,设计简易有效的电磁超声SH导波换能器,并分析换能过程中的多物理场耦合机理,在COMSOL Multiphysics中开展有限元建模和仿真。为了优化换能器,根据正交试验理论,进行多因素多水平分析,获得5个参数对导波激励的影响规律以及最优参数组合。进一步,搭建扁钢检测系统,开展SH导波实验,结果表明：相比于正交试验表中的效果最好的前两个参数组合,最优参数组合的换能器性能在导波幅度上分别提升了14.0%和28.6%。     

Optimizing the design of a tactile display based on a capacitive micromachined ultrasonic transducer array

In this paper, the design and simulation of a tactile display that is based on a capacitive micromachined ultrasonic transducer (CMUT) array is presented. The array implements a ‘pixel’ of the display and is used to focus airborne ultrasound energy on the skin surface. The pressure field generated by the focused ultrasound waves excites the mechanoreceptors under the skin and transmits tactile information. The geometry of the individual transducer and the array are optimized so that the medium presents maximum impedance and the membrane oscillates with maximum deflection. Optimization is achieved using an electrical equivalent circuit model and the Berkeley Simulation Program with Integrated Circuit Emphasis (SPICE) code. Finite element analysis of the CMUT and the CMUT phased array is used to verify the SPICE results. The pressure at focal point is compared with the pressure threshold required for mechanoreceptor excitation in order to verify the feasibility of the design. Copyright © 2012 John Wiley & Sons, Ltd.     

半开式离心泵叶轮内部流场的DES模拟

本文采用DES模型分析了半开式离心泵内部流动,并与内部流动试验进行对比。结果证明本文采用的DES非定常流动模拟方法可以较为准确的预测半开式离心泵内的流动状况。然后,对DES计算结果进行了进一步分析,发现在半开式离心泵叶轮的出口边缘存在＂弱射流-尾迹＂流动结构。     

High‐bandwidth design of hard disk control system using H∞ control with feedback‐type uncertainty

In hard disk drives, it is important to enlarge the control bandwidth in order to shorten the track pitch for larger data capacity. However, it is difficult for the H_∞ control method to increase the control bandwidth if the mechanical resonance modes have uncertainty. This is because the robustness of the H_∞ control method is assured by the small‐gain theorem for additive or multiplicative perturbation and the control bandwidth is limited by the uncertainty. In this study, we propose an H_∞ control method for high‐bandwidth design by introducing a new uncertainty model with a feedforward and a feedback path in order to reduce the conservatism of robust design. The effectiveness is shown by numerical simulations. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 173(4): 54–62, 2010; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21025     

A new decentralized model reference adaptive control for a class of interconnected dynamic systems using variable structure design

This paper presents a new decentralized model reference adaptive control for a class of large-scale interconnected dynamic systems. Interconnections among subsystems may be time-invariant or time-varying and linear or non-linear. The scheme proposed here only takes input and output measurements from each subsystem for input synthesis. Using a variable structure design concept, we show that the tracking errors will converge to zero in finite time despite the interconnections with any possible strengths.