A U-shaped linear ultrasonic motor using longitudinal vibration transducers with double feet

A U-shaped linear ultrasonic motor using longitudinal vibration transducers with double feet was proposed in this paper. The proposed motor contains a horizontal transducer and two vertical transducers. The horizontal transducer includes two exponential shape horns located at the leading ends, and each vertical transducer contains one exponential shape horn. The horns of the horizontal transducer and the vertical transducer intersect at the tip ends where the driving feet are located. Longitudinal vibrations are superimposed in the motor and generate elliptical motions at the driving feet. The two vibration modes of the motor are discussed, and the motion trajectories of driving feet are deduced. By adjusting the structural parameters, the resonance frequencies of two vibration modes were degenerated. A prototype motor was fabricated and measured. Typical output of the prototype is no-load speed of 854 mm/s and maximum thrust force of 40 N at a voltage of 200 V(rms).     

表面弹性波马达的工作机理和优化设计研究

探讨了表面弹性波马达的工作机理和优化设计。采用具有能量循环功能的表现弹性波换能器结构，提高了表面弹性波马达效率，将马达的驱动电压阈值从100V降到了10V以下。在频率10MHz，峰峰值为10V的正弦的电压激励下，获得振动幅度为20nm的表面性波，马达的无负载速度达到0．34m/s，最大推动力输出达到0．06N。     

A flex-compressive-mode piezoelectric transducer for mechanical vibration/strain energy harvesting

A piezoelectric transducer for harvesting energy from ambient mechanical vibrations/strains under pressure condition was developed. The proposed transducer was made of two ring-type piezoelectric stacks, one pair of bow-shaped elastic plates, and one shaft that pre-compresses them. This transducer works in flex-compressive (F-C) mode, which is different from a conventional flex-tensional (F-T) one, to transfer a transversely applied force F into an amplified longitudinal force N pressing against the two piezo-stacks via the two bowshaped elastic plates, generating a large electric voltage output via piezoelectric effect. Our experimental results show that without an electric load, an F-C mode piezo-transducer could generate a maximum electric voltage output of up to 110 Vpp, and with an electric load of 40 κΩ, it a maximum power output of 14.6 mW under an acceleration excitation of 1 g peak-peak at the resonance frequency of 87 Hz.     

Improvement of the longitudinal vibration system for the hybrid transducer ultrasonic motor

This paper presents a symmetric hybrid transducer ultrasonic motor designed to produce large longitudinal vibration stress in the rotor/stator contact interface for high-torque operation. The nodal plane of the longitudinal vibration mode was adjusted to match the rotor/stator contact interface, and the piezoelectric ceramic disks for the longitudinal vibration were installed at the nodal plane of the longitudinal vibration mode for effective excitation. An experimental motor, 20 mm in diameter, using the first torsional vibration mode and the second longitudinal vibration mode was manufactured. A maximum torque of 0.8 N.m was achieved in the prototype, an improvement over previous versions.     

Orientation dependence of electromechanical coupling factors in KNbO(3)

This paper is concerned with the electromechanical coupling factors for bulk waves in KNbO(3) crystal. The dependence of coupling factors on the orientation of vibrators for various types of vibration modes has been calculated. As a result, it has been found that most of these coupling factors are very large at certain orientations of vibrators. Especially, the maximum coupling factor of the thickness-extensional mode excited with a perpendicular field, k(t ), is as high as 69% for the rotated X-cut by an angle 49.5 degrees about the Y-axis; that of the thickness-shear mode, k(s), is 88% for the X-cut. To the best of our knowledge, these coupling factors are the highest among those of known piezoelectrics. It has also been found that the coupling factor of the width-extensional mode of a thin finite-width plate with electrodes on its edges, k(ww)', is 82% for the rotated Z-cut by an angle 43.5 degrees about the Y-axis. This vibrator would be promising as elements of phased array ultrasonic probes.     

Dynamics of an ultrasonic transducer used for wire bonding

The vibration displacement distributions along a transducer used in ultrasonic wire bonding were measured using a heterodyne interferometer, and many nodes and anti-nodes were found. A mechanical finite element method (FEM) was used to compute the resonant frequencies and vibration mode shapes. The displacement distributions of the dominant 2nd axial mode agreed well with the measured values. Undesirable nonaxial modes, including the higher order flexural and torsional modes, also were excited at frequencies very close to the working frequency (2nd axial mode) of the transducer. Hence, the measured displacements were the resultant of all the allowable modes being excited. However, the excitation of these nonaxial modes were small enough not to affect the formation of consistent and high quality wire bonds. Results of the present study were used to determine a suitable location for installing a piezoelectric sensor to monitor the bond quality.     

A cylindrical traveling wave ultrasonic motor using a circumferential composite transducer

This paper intends to present and verify a new idea for constructing traveling wave ultrasonic motors that may effectively avoid the drawbacks of conventional traveling wave motors using bonded PZT plates as the exciting elements. In the configuration of the motor's stator, a composite sandwich type transducer is used to excite a traveling wave in a cylinder with two cantilevers as the coupling bridges between the transducer and the cylinder. The design process of the stator is described using the FEM modal analysis method, and the establishment of traveling wave on the cylindrical stator was simulated by FEM transient analysis. To verify the theoretical analysis results, a laser Doppler scanner was employed to test the mode shapes of a prototype stator excited by the longitudinal and bending vibrations respectively. Finally, to validate the design idea, a prototype motor was fabricated and tested; the typical output features are no-load speed of 156 rpm and maximum torque of 0.75 N·m under exciting voltages of 70 V(rms) applied to excite the longitudinal vibration of the transducer and 200 V(rms) applied to excite the bending vibration.     

Elastic contact conditions to optimize friction drive of surface acoustic wave motor

The optimum pressing force, namely the preload, for a slider to obtain superior operation conditions in a surface acoustic wave motor have been examined. We used steel balls as sliders. The preload was controlled using a permanent magnet. The steel balls were 0.5, 1, and 2 mm diameter, with the differences in diameter making it possible to change contact conditions, such as the contact pressure, contact area, and deformation of the stator and the slider. The stator transducer was lithium niobate, 128 degrees rotated, y-cut x-propagation substrate. The driving frequency of the Rayleigh wave was about 10 MHz. Hence, the particle vibration amplitude at the surface is as small as 10 nm. For superior friction drive conditions, a high contact pressure was required. For example, in the case of the 1 mm diameter steel ball at the sinusoidal driving voltage of 180 V(peak), the slider speed was 43 cm/sec, the thrust output force was 1 mN, and the acceleration was 23 times as large as the gravitational acceleration at a contact pressure of 390 MPa. From the Hertz theory of contact stress, the contact area radius was only 3 mum. The estimation of the friction drive performance was carried out from the transient traveling distance of the slider in a 3 msec burst drive. As a result, the deformation of the stator and the slider by the preload should be half of the vibration amplitude. This condition was independent of the ball diameter and the vibration amplitude. The output thrust per square millimeter was 50 N, and the maximum speed was 0.7 m/sec. From these results, we conclude that it is possible for the surface acoustic wave motor to have a large output force, high speed, quick response, long traveling distance, and a thin micro linear actuator.     

Modelling the transverse-mode response of a two-port SAW resonator

An equation is derived for the transverse-mode frequencies of a two-port surface-acoustic-wave (SAW) resonator with uniform reflection gratings. It is postulated that only odd-order (symmetric) transverse modes should be excited in such a grating, due to its symmetrical placement with respect to the interdigital transducer (IDT). Frequency response modeling involves a summation of one-dimensional transmission-matrix computations for the fundamental mode and participating transverse ones. Excellent agreement is obtained between theory and experiment for a 360-MHz resonator with three close-in transverse modes, attributed to symmetric modes of odd order m=3, 5, 7.     

Compact piezoelectric stacked actuators for high power applications

Small, hollow, multilayer actuators with a diameter of 3 mm were fabricated by the stacking method from piezoelectric hard lead zirconate titanate (PZT) ceramics. Langevin vibrators were also constructed with the hollow multilayer actuators. The performance capabilities of the actuator and Langevin vibrator samples were examined under high-power conditions. The high-power vibration level at a given sinusoidal drive voltage was significantly enhanced by using a multilayer structure under either a nonresonance or resonance condition. A maximum vibration velocity of 0.17 m/sec was obtained for the 9-layer actuator sample under nonresonance conditions. The vibration velocity was further improved with the Langevin vibrator driven at the resonance frequency. The temperature rise due to heat generation under high-power conditions was the immediate limitation on the maximum accessible vibration velocity for the stacked actuators.     

三角形状压电振子压电特性分析与仿真

(压电振子的几何形状是影响其振动发电的重要因素之一。在相同压电材料体积下,三角形压电振子相比于矩形和梯形压电振子具有更大的发电能力。选用悬臂梁式三角形状压电振子作为研究对象,利用有限元分析软件ANSYS进行仿真研究。建立有限元模型;通过静力学和模态分析,研究压电振子的几何形状对其输出电压、固有频率的影响规律,然后在满足原来输出电压不下降的前提下对其进行尺寸优化,提高单位体积的发电能力。在相同边界条件和外力作用下,优化尺寸模型的体积是原来的0.94倍,输出电压是原来的1.03倍,取得了很好的优化效果。     

Vibration maps of capacitive micromachined ultrasonic transducers by laser interferometry

A 1.8-mm × 1.8-mm capacitive micromachined ultrasonic transducer (CMUT) element is experimentally characterized by means of optical measurements. Optical displacement measurements provide information on the resonant behavior of the single membranes and also allow us to investigate the dispersion in the frequency spectrum of adjacent membranes. In addition, higher order mode shapes are observed, showing that either symmetrical or asymmetrical modes are excited in CMUT membranes. Laser interferometry vibration maps, combined with quantitative displacement measurements, provide information about the quality and repeatability of the fabrication process, which is a basic requirement for 2D array fabrication for ultrasound imaging     

High power single mode output CO2 laser

Abstract

While attempting to reach TEMoo single mode high output power, the transverse discharge method was adopted. The optic axis, the direction of glow discharge and gas flow velocity are all mutually orthogonal. The discharge region has a 2.3 liter medium volume, and 100 m/sec gas flow. This small signal gain exceeds 0.8/m in the local region. We also adopted a stable multi‐path cavity for coordinating the larger volume laser medium. Under auxiliary discharge, the maximum output power can reach 1500W, at an efficiency of 9%.     

L-shaped piezoelectric motor--part I: design and experimental analysis

This paper proposes an L-shaped piezoelectric motor consisting of two piezoelectric bimorphs of different lengths arranged perpendicularly to each other. The coupling of the bending vibration mode of the bimorphs results in an elliptical motion at the tip. A detailed finite element model was developed to optimize the dimensions of bimorph to achieve an effective coupling at the resonance frequency of 246 Hz. The motor was characterized by developing rotational and linear stages. The linear stage was tested with different friction contact surfaces and the maximum velocity was measured to be 12 mm/s. The rotational stage was used to obtain additional performance characteristics from the motor: maximum velocity of 120 rad/s, mechanical torque of 4.7 × 10-(5) N·m, and efficiency of 8.55%.     

Ultrasonic motors using piezoelectric ceramic multimode vibrators

The development is reported of an ultrasonic motor using piezoelectric ceramic multimode vibrators consisting of circular or annular plates in which degenerate horizontal vibration modes of the same or different form are used. Two orthogonal nonaxisymmetric vibration modes were used in the same-form case, and the combination of a nonaxisymmetric vibration mode and a radial vibration mode was used in the different-forms case. Some details of the motor design and its experimental characteristics are presented. The ultrasonic motor presented here has a special advantage in its thin construction.     

Investigation of cross-coupling in 1-3 piezocomposite arrays

Plate waves inside the piezoelectric layer are much involved in the element cross-coupling in transducer arrays for medical imaging. In this work, such waves are analyzed in 1-3 piezocomposite materials on the basis of conventional guided modes formalism in which the piezocomposite is considered as a homogeneous medium. Cross-coupling measurements have been made on two different transducer arrays using a network analyzer and a laser interferometric probe. It is shown how the analysis in terms of symmetrical Lamb waves gives an interesting qualitative interpretation, explaining most of the cross-coupling amplitude variations with frequency. Results show that the 0th and 3rd symmetrical Lamb waves are mainly involved in coupling inside composite plates. The S₀ mode is responsible for the inter-element coupling, whereas the S₃ mode widens the effective width of the excited element     

Hybrid transducer type ultrasonic motor

A type of ultrasonic motor whose stator is composed of a torsional vibrator and multilayered piezoelectric actuators is proposed and has been fabricated for trial. The stator is operated at the resonance frequency of the torsional vibration. The vibrator generates the mechanical output force and the actuators control the frictional force. The construction provides for arbitrary Lissajous's figures at the contacting surface and contributes to large mechanical output power with high efficiency and bidirectional motion. It also gives greater freedom of design. The prototype motor produced a maximum torque of 7 kg-cm and a maximum efficiency of 33%     

Modeling and fabrication of a piezoelectric vibration‐induced micro power generator

Abstract

In this paper, theoretical and experimental study on a piezoelectric vibration‐induced micro power generator that can convert mechanical vibration energy into electrical energy is presented. The mechanical‐electrical energy conversion mechanism is a voltage between two capacitors, which belong to the mechanical and the piezoelectric equivalent circuits, respectively. To verify the theoretical analysis, two clusters of transducer structures are fabricated. Piezoelectric lead zirconate titanate (PZT) material is chosen to make the energy conversion transducer. The desired shape of the piezoelectric generator with its resonance frequency in accordance with the ambient vibration source is designed by finite element analysis (FEA).

Experimental results show that the maximum output voltages are generated at the first mode resonance frequencies of the structure. The overall conversion efficiency is measured to be 33%. The experimental results coincide with the theoretical analysis.     

Broadband tonpilz underwater acoustic transducers based onmultimode optimization

Head flapping has often been considered to be deleterious for obtaining a tonpilz transducer with broadband, high power performance. In the present work, broadband, high power tonpilz transducers have been designed using the finite element (FE) method. Optimized vibrational modes including the flapping mode of the head are effectively used to achieve the broadband performance. The behavior of the transducer in its longitudinal piston mode and in its flapping mode is analysed for in-air and in-water situations. For the 37.8% bandwidth of the center frequency from 28.5 to 41.8 kHz, the amplitude variation of the transmitting voltage response (TVR) does not exceed ±2 dB and a maximum TVR of 146.8 dB (ref. 1 μPa/volt at 1 meter) is obtained. Reasonable agreement between the experimental results and the numerical results is achieved. A maximum sound pressure level of 214.8 dB can be expected. Further numerical calculation indicates that there is potential for increasing the bandwidth by varying other parameters in the design     

电液疲劳试验系统的变谐振控制技术研究

随着激振频率的增加,电液疲劳试验机激振输出幅值急剧衰减,激振频率和激振输出幅值两者之间存在相互矛盾的关系,因此提出了利用谐振能量来提高激振输出幅值的方案。该方案通过改变阀控单出杆液压缸无杆腔容积的方法来改变系统的谐振频率,使得谐振频率与激振频率重合,在谐振点进行激振。在对液压动力机构的运动过程进行分析的基础上,建立系统的数学模型,运用四阶龙格库塔的数值方法对其进行求解,并对仿真结果进行理论分析;理论分析表明可以通过改变无杆腔容积来改变系统的谐振频率,且在谐振点处的激振输出幅值有较大幅度的提升;从负载流量曲线上看,由于谐振能量的输出使得在谐振点处的负载流量急剧降低。最后建立实验系统对以上仿真结果进行实验验证。实验结果表明：在谐振点出的激振输出幅值为饱和输出幅值的25%左右,负载流量反而减小了90%左右;通过改变无杆腔的容积能有效改变谐振频率,拓宽电液疲劳试验机应用范围。