热超声键合换能系统动力学特性的非线性检验

根据实际超声换能系统的振动测试，提出了热超声键合换能系统动力学特性的非线性检验方法，利用基于相空间重构的替代数据法，通过对换能杆末端的实测数据进行正确替代，并用非线性动力学的理论来检验其是否具有非线性.通过实验对超声换能杆末端轴向、俯仰、横向的振动时间序列的关联维数进行了准确的计算，从而清晰地描述了上述三个方向的动力学特性.所提出的方法有利于更好地认识超声键合换能系统，为建立更加合理的非线性动力学模型奠定良好的理论基础，有很好的应用价值. 关键词： 超声键合 时间序列 相位随机化 替代数据     

Modeling of lamb waves generated by integrated transducers in composite plates using a coupled finite element-normal modes expansion method

Thin piezoelectric transducers attached to or embedded within composite structures could be used for in situ structural health monitoring. For plate-shaped structures, the useful ultrasonic vibration modes are Lamb waves. Preliminary testing has already demonstrated the suitability and practical feasibility of such integrated transducers, but better control of the generation of Lamb modes seems to be necessary. Therefore, an original modeling approach has been developed, which can be used to design and optimize these "sensitive materials." This modeling technique allows the determination of the amplitude of each Lamb mode excited in a composite plate with surface-bonded or bulk-embedded piezoelectric elements. The method consists of a coupling of the finite element method (FEM) and the normal modes expansion method. The limited finite element mesh of the transducer and its vicinity enables the computation of the mechanical field created by the transducer, which is then introduced as a forcing function into the normal modes equations. The adequacy and accuracy of this modeling method have been numerically and experimentally verified.     

Rare earth ultrasonic transducer technique research

Transducer is the necessary and most important part in the maxonics. New applications demand for new transducer, and the renovation of the transducer will open a new field for the application of the maxonics. The important method to develop new transducer is to find and develop new material. The rare earth giant magnetostrictive material Terfenol-D is a new functional material with good performance. In this paper, the rare earth ultrasonic transducer was analyzed theoretically and devised in four-port method and FEM software ANSYS. A rare earth ultrasonic transducer and the transducer with the half wave horn are developed, whose performance has shown unique advantage compared with the piezoelectric transducer.     

Development of non-destructive bond monitoring techniques for ultrasonic bonders

Simulation of an ultrasonic bonding tool was performed to formulate and analyse the relationships between the boundary conditions due to loading at the bond-tool interface and the measured parameters, such as the ultrasonic frequency and the input impedance variations during the bonding process. It is believed that improved process monitoring techniques can be developed based on the functional dependence between the ultrasonic frequency, input impedance variations and the boundary conditions at the bond-tool interface. Both experimental and simulation results obtained indicate that a strong dependence exists between the load, resonant frequency and the input impedance in an ultrasonic bonder. Resonant frequency was observed to increase as the loading on the bond surface increases.     

Investigations of the barbell ultrasonic transducer operated in the full-wave vibrational mode

In this paper, the resonance frequency equation and expression of displacement amplitude magnifications of a full-wave barber ultrasonic horn are obtained. By discussing the relationships between the displacement amplitude magnifications and the geometrical dimensions, the optimized design of the horn for the largest magnification is proposed, which is helpful to improve the radiation power and the transfer efficiency of the acoustic energy of the ultrasonic oscillatory system. Based on the optimized design of the horn, we introduced a barbell ultrasonic transducer operated in the longitudinal full-wave vibrational model and obtained the resonance frequency equations. For comparison, the resonance frequencies of the full-wave barbell horn and the full-wave barbell transducer are also analyzed by finite element method (FEM). It is shown that the values obtained by theoretical analysis and FEM are in good agreement with experimental observations. We hope that the research of this paper is helpful for the use of the barbell horn and transducer in the applications such as ultrasonic liquid processing.     

Autoresonant control of nonlinear mode in ultrasonic transducer for machining applications

Experiments conducted in several countries have shown that the improvement of machining quality can be promoted through conversion of the cutting process into one involving controllable high-frequency vibration at the cutting zone. This is achieved through the generation and maintenance of ultrasonic vibration of the cutting tool to alter the fracture process of work-piece material cutting to one in which loading of the materials at the tool tip is incremental, repetitive and controlled. It was shown that excitation of the high-frequency vibro-impact mode of the tool-workpiece interaction is the most effective way of ultrasonic influence on the dynamic characteristics of machining. The exploitation of this nonlinear mode needs a new method of adaptive control for excitation and stabilisation of ultrasonic vibration known as autoresonance. An approach has been developed to design an autoresonant ultrasonic cutting unit as an oscillating system with an intelligent electronic feedback controlling self-excitation in the entire mechatronic system. The feedback produces the exciting force by means of transformation and amplification of the motion signal. This allows realisation for robust control of fine resonant tuning to bring the nonlinear high Q-factor systems into technological application. The autoresonant control provides the possibility of self-tuning and self-adaptation mechanisms for the system to keep the nonlinear resonant mode of oscillation under unpredictable variation of load, structure and parameters. This allows simple regulation of intensity of the process whilst keeping maximum efficiency at all times. An autoresonant system with supervisory computer control was developed, tested and used for the control of the piezoelectric transducer during ultrasonically assisted cutting. The system has been developed as combined analog-digital, where analog devices process the control signal, and parameters of the devices are controlled digitally by computer. The system was applied for advanced machining of aviation materials.     

An ultrasonic instrument for rapid B-scanning of the heart

A rapid ultrasonic B-scan instrument has been constructed for scanning the heart. An important factor in its design has been the need to make the maximum use of the points on the chect from which ultrasound can be transmitted into the heart avoiding bone and lung. A high degree of flexibility in the manipulation of the direction of the ultrasound beam allows the cardiac structures to be thoroughly scanned. Finally, since the system operates by rapidly moving a standard transducer, it is possible to use it to perform the more established ultrasonic techniques for heart examination such as time-motion scanning.     

Design and development of a multi-hole broadband-based ultrasonic transducer

In order to improve the efficiency of ultrasonic energy transformed from electricity for an ultrasonic transducer array, a novel 1/2 wavelength multi-hole broadband-based transducer was designed, developed and evaluated. The low equivalent mass of the transducer is realized in this work through drilling holes on the output end of the horn. In comparison with a traditional transducer, the developed transducer has demonstrated a lower mechanical quality coefficient and a wider broadband. As a result, an ultrasound treatment system for crude oil has been developed based on the new transducer design. Furthermore, we have demonstrated the effectiveness of the ultrasound treatment system on viscosity reduction of crude oil and paraffin.     

K-space Prony’s method for generating the basis functions of multi-Gaussian beam models

The expansion coefficients of a multi-Gaussian ultrasonic beam model are obtained by a new approach that applies Prony´s method in a K-space domain. This method allows the fitting of the Gaussian beam directly at the face of the transducer with very high computational efficiency. It is demonstrated that the K-space Prony’s method can be used to accurately model the transducer field of planar and focused piston transducers, as well as probes that do not act as pistons. The choice of parameters appearing in the method and their influence on performance are discussed.     

Design and Construction of an Autonomous Control System for Mössbauer Spectrometry

An autonomous control system for Mössbauer spectrometry based on two modules has been designed and built. The first module operates as a multichannel analyzer for the acquisition and storage of spectra, and the second one is a driver unit which controls and supplies the power for the velocity transducer. A microcontroller executes the digital control algorithm for the velocity transducer motion and manages the data acquisition and storage tasks. The user can monitor the system from an external PC through the serial port. A graphic interface made with the LabVIEW software allows the user to adjust digitally the control parameters for the velocity transducer motion, the channels number, to visualize as well as save spectra in a file. The microcontroller can be reprogrammed from the PC through the same serial port without intervention of a universal programmer, which allows the user to make proper software for different applications of the system. The system has been tested for linearity with several standard absorbers yielding satisfactory results. The low cost of its design, construction and maintenance make this equipment to be an attractive choice when assembling a Mössbauer spectrometer.     

Multiobjective optimization of an ultrasonic transducer using NIMBUS

The optimal design of an ultrasonic transducer is a multiobjective optimization problem since the final outcome needs to satisfy several conflicting criteria. Simulation tools are often used to avoid expensive and time-consuming experiments, but even simulations may be inefficient and lead to inadequate results if they are based only on trial and error. In this work, the interactive multiobjective optimization method NIMBUS is applied in designing a high-power ultrasonic transducer. The performance of the transducer is simulated with a finite element model, and three design goals are formulated as objective functions to be minimized. To find an appropriate compromise solution, additional preference information is needed from a decision maker, who in our case is an expert in transducer design. A realistic design problem is formulated, and an interactive solution process is described. Our findings demonstrate that interactive multiobjective optimization methods, combined with numerical simulation models, can efficiently help in finding new solution approaches and possibilities as well as new understanding of real-life problems as entirenesses. In this case, the decision maker found a solution that was better with respect to all three objectives than the conventional unoptimized design.     

超声手术刀声学系统设计和实验*

为兼顾阶梯型变幅杆的高放大系数以及曲线过渡变幅杆突变截面处的高疲劳强度,本文提出了一种最速曲线过渡段的超声刀换能器。首先,基于等效电路法,设计了夹心式压电换能器的基本结构。在此基础上,结合超声刀的工作条件和材料特性,对换能器基本结构进行精确设计;然后,利用FEM法和实验法获取了换能器纵振频率以及频率响应曲线,进一步证明了本文所设计换能器的有效性;最后,对所设计的换能器进行了一系列测试,结果表明：测定了无负载换能器谐振频率与输出端振幅,与设计目标、仿真结果相吻合;连接负载后凝血,切割效果良好。     

A new beamforming technique for ultrasonic imaging systems

We propose a simple, versatile and inexpensive beamforming method that performs the aperture windowing of an ultrasonic transducer array in the transmit mode, without modifying the driver voltage, but simply controlling the length of the electric pulse driving the array elements. A conversion formula has been determined that permits us to compute, for a desired emitted pulse amplitude, the corresponding driving pulse length to be applied. Any shading function can be implemented over any type of transducer array, using very low-cost hardware. Computer simulations and experimental measurements, with a 3.8 MHz convex array, confirm the effectiveness of this approach in enhancing the contrast resolution, since the off-axis intensity in the radiated beam pattern is largely reduced.     

Ultrasonic phased array controller for hyperthermia applications

Multiple and mechanically scanned ultrasound transducer systems have demonstrated the efficacy of using ultrasound to produce deep localized hyperthermia. The use of ultrasonic phased arrays has been proposed as an alternative to these systems. A phased array offers a more flexible approach to heating tumours in that the size, shape, and position of its focal region can be altered during the course of treatment in order to achieve the desired temperature distribution. This added flexibility comes at the cost of increased complexity of the hardware necessary to drive the transducer because each element requires its own amplifer with both phase and amplitude control. In order for phased arrays with large numbers of elements to be feasible for hyperthermia applications, the complexity of this circuitry must be minimized. This paper describes a circuit design which simplifies the electronics required to control a phased array transducer system for hyperthermia applications. The design is capable of controlling virtually any type of phased array transducer operating at frequencies less than 2 MHz. The system performance was verified through beam profile measurements using a 48-element tapered phased array transducer.     

Recent developments in vibrating-plate macrosonic transducers

As is known, the stepped-plate transducer [Ultrasonics 16 (6) (1978) 267] represents an optimum system for the efficient generation of high-intensity sonic and ultrasonic radiation in fluid media. Nevertheless, the design of this transducer may be difficult to adapt to some specific problems. Such is the case of the treatment of large volumes in industrial installations. A solution is the enlargement of the surface of the radiating plate. However, that means to work at high-order vibration modes which implies numerous practical problems. Another case is the application of the stepped-plate transducer for the generation at sonic frequencies where the height of the steps of the radiating plate, which has to be half a wavelength of the radiation, becomes too high and it makes the transducer construction impractical. To face these specific situations a series of new designs in transducer development have been recently carried out. This paper presents the characteristics of two new transducer devices, one for the treatment of large industrial volumes and the other for low-frequency sonic applications. Both devices are based on vibrating-plate radiators and represent a novel approach to practical existing problems.     

自由端盖Ⅲ型宽带弯张换能器的设计

提出了一种利用多模耦合实现低频、宽带、大功率特性的新结构Ⅲ型弯张换能器。通过在压电陶瓷堆内部嵌入与凹型弯张壳体相连的弹性辅助弯曲梁结构,并用弯曲圆盘作为顶部自由端盖,增加有效工作模态。利用有限元方法对换能器进行了设计优化,分析结果显示换能器在低频段存在4个主要工作模态。根据优化结果,加工制作了换能器样机,水池实验的测试结果表明:在1.5～5.5 kHz范围内,换能器样机的发送电压响应均大于135 dB;1.5～4 kHz内的最大发送电压响应大于142 dB,响应起伏小于6 dB。研究结果表明自由端盖Ⅲ型弯张换能器不仅能够在小尺寸设计下实现大功率工作,还能获得低频宽带发射性能。      

Air-coupled MUMPs capacitive micromachined ultrasonic transducers with resonant cavities

This work reports performance improvements of air-coupled capacitive micromachined ultrasonic transducers (CMUTs) using resonant cavities. In order to perform this work, we have designed and manufactured a CMUT employing multi-user microelectromechanical systems (MEMS) processes (MUMPs). The transducer was designed using Helmholtz resonator principles. This was characterised by the dimensions of the cavity and several acoustic ports, which had the form of holes in the CMUT plate. The MUMPs process has the advantage of being low cost which allows the manufacture of economic prototypes. In this paper we show the effects of the resonant cavities and acoustic ports in CMUTs using laser Doppler vibrometry and acoustical measurements. We also use Finite Element (FE) simulations in order to support experimental measurements. The results show that it is possible to enhance the output pressure and bandwidth in air by tuning the resonance frequency of the plate (f_p) with that of the Helmholtz resonator (f_H). The experimental measurements show the plate resonance along with an additional resonance in the output pressure spectrum. This appears due to the effect of the new resonant cavities in the transducer. FE simulations show an increase of 11 dB in the output pressure with respect to that of a theoretical vacuum-sealed cavity MUMPs CMUT by properly tuning the transducer. The bandwidth has been also analyzed by calculating the mechanical Q factor of the tuned CMUT. This has been estimated as 4.5 compared with 7.75 for the vacuum-sealed cavity MUMPs CMUT.     

Microelectronics mounted on a piezoelectric transducer: method, simulations, and measurements

This paper describes the design of a highly integrated ultrasound sensor where the piezoelectric ceramic transducer is used as the carrier for the driver electronics. Intended as one part in a complete portable, battery operated ultrasound sensor system, focus has been to achieve small size and low power consumption. An optimized ASIC driver stage is mounted directly on the piezoelectric transducer and connected using wire bond technology. The absence of wiring between driver and transducer provides excellent pulse control possibilities and eliminates the need for broad band matching networks. Estimates of the sensor power consumption are made based on the capacitive behavior of the piezoelectric transducer. System behavior and power consumption are simulated using SPICE models of the ultrasound transducer together with transistor level modelling of the driver stage. Measurements and simulations are presented of system power consumption and echo energy in a pulse echo setup. It is shown that the power consumption varies with the excitation pulse width, which also affects the received ultrasound energy in a pulse echo setup. The measured power consumption for a 16 mm diameter 4.4 MHz piezoelectric transducer varies between 95 microW and 130 microW at a repetition frequency of 1 kHz. As a lower repetition frequency gives a linearly lower power consumption, very long battery operating times can be achieved. The measured results come very close to simulations as well as estimated ideal minimum power consumption.     

电容式微超声波换能器的设计与电容值测试*

本文设计的微电容超声波换能器(CMUT)是由电容阵列组成的超声波传感器,主要是利用电容的改变来实现能量的转换。是基于硅硅键合技术的MEMS电容式超声传感器,制作的传感器误差小,并且工艺流程简单且能进行量产。在利用E4990A阻抗分析仪对传感器进行C—V测试分析而得出其电容的实际值与理论值的误差仅为1.6%。并且利用该仪器测试传感器电容在工作电压下随频率的变化,得出其在工作电压下,频率为400K的时候电容值为617.67PF,为对传感器进行理论计算提供了重要支撑,并且为后续转换电路的设计提供了数据支撑。     

A method of improving overall resolution in ultrasonic array imaging using spatio-temporal deconvolution

In this paper a beamforming method for ultrasonic array imaging is presented that performs both spatial and temporal deconvolution based on a minimum mean square error (MMSE) criteria. The presented MMSE receive mode beamformer performs a regularized inversion of the propagation operator for the ultrasonic array system at hand. The MMSE beamformer accounts for the transmit and receive processes, defined in terms of finite array element sizes, transmit focusing laws and electrical transducer characteristics. The MMSE beamformer is compared to the traditional delay-and-sum (DAS) beamformer with respect to both resolution and signal-to-noise ratio. The two algorithms are compared using both simulated and measured data. The simulated data was obtained using ultrasonic field simulations and the measured data was acquired using a linear phased array imaging wire targets in water. The results show that the MMSE beamformer has superior temporal and lateral resolution compared to DAS. It is also shown that the MMSE beamformer can be expressed as a filter bank, which enables parallel processing at high frame rates.