Vibration Transducer Research Articles

A new type of high power composite ultrasonic transducer

A new type of high power composite ultrasonic transducer was proposed and studied. The composite transducer consists of a sandwich longitudinal piezoelectric transducer, an isotropic metal hollow cylinder with large radial dimension, and the front and back metal radiation mass. By means of its special structure and Poisson’s effect, the composite transducer can produce vibrations both in its longitudinal and radial directions, and therefore, it can radiate sound waves in three-dimensional space. The electro-mechanical equivalent circuit of the composite transducer was derived and the resonance frequency equation was obtained analytically. Numerical methods were used to simulate the vibration of the composite transducer, and the vibrational displacement distribution, the resonance frequency and the radiation sound field are given. Some composite transducers are designed and manufactured; their resonance frequencies and the radiation acoustic field are measured and compared with the analytical and numerical results. It can be seen that the measured frequencies and acoustic field contour are in good agreement with the analytical and numerical results. It is expected that this kind of composite ultrasonic transducer can be used in more and more power ultrasonic applications, such as ultrasonic cleaning, ultrasonic extraction, ultrasonic sonochemistry and other ultrasonic liquid processing, where high ultrasonic power and large ultrasonic processing space are needed increasingly.

A rotary ultrasonic motor using bending vibration transducers

A rotary ultrasonic motor using bending vibration transducers is proposed. In each transducer, two orthogonal bending vibrations are superimposed and an elliptical trajectory is generated at the driving foot. Typical output of the prototype is a no-load speed of 58 rpm and maximum torque of 9·5 Nm under an exciting voltage of 200 V(rms).

A Linear Ultrasonic Motor Using Bending Vibration Transducer with Double Driving Feet

A linear ultrasonic motor using bending vibration transducer with double driving feet was proposed. The motor consists of two exponential shape horns located on the two leading ends. Two orthogonal bending vibrations are superimposed in the motor and generate elliptical trajectories at the driving feet. The motion trajectories of the driving feet were deduced. Transient analysis was developed to gain the vibration characteristics of motor. A prototype motor was fabricated and measured. Typical output of the prototype is no-load speed of 990 mm/s and maximum thrust force of 12 N at a voltage of 150 Vrms.

Design of A New Vibration Transducer for Implantable Middle Ear Hearing Devices

AbstractA new vibration transducer was developed for implantable middle ear hearing devices (IMEHDs). It comprises two permanent magnets positioned inside three coils. The transducer maximizes the interaction between the magnetic fields of the two magnets and the electrical current flowing through the coils. Further, the transducer is robust to external magnetic fields because the magnetic fields inside it are symmetrical. The frequency response was simulated by finite element analysis (FEA). The vibrational displacement of the proposed transducer is 6 dB greater than those of the differential floating mass transducer (DFMT) and the floating mass transducer (FMT). On the basis of these results, a prototype was fabricated and its frequency response was experimentally investigated and compared with simulation results. Finally, it is shown that the proposed transducer has a higher vibrational displacement than the older ones. © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

A high-power linear ultrasonic motor using longitudinal vibration transducers with single foot

A high-power linear ultrasonic motor using longitudinal vibration transducers with single foot was proposed in this paper. The stator of proposed motor contains a horizontal transducer and a vertical transducer. Longitudinal vibrations are superimposed in the stator and generate an elliptical trajectory at the driving foot. The sensitivity analysis of structural parameters to the resonance frequencies of two working modes of the stator was performed using the finite element method. The resonance frequencies of two working modes were degenerated by adjusting the structural parameters. The vibration characteristics of stator were studied and discussed. A prototype motor was fabricated and measured. Typical output of the prototype is a no-load speed of 1160 mm/s and maximum thrust force of 20 N at a voltage of 200 V(rms).

Study on the vibration characteristics of a finite-width corrugated cylindrical shell piezoelectric transducer

Coupled extensional and flexural vibrations of an ultrasonic piezoelectric transducer are studied in the paper. The ultrasonic piezoelectric transducer is made of piezoelectric polymer PVDF films and modeled as a corrugated cylindrical shell with a finite width in the ridge direction, which consists of multiple pieces of circular cylindrical surfaces smoothly connected along their ridges. The classical shell theory is used to obtain the theoretical solution. Effects of the edge constraints on vibrational characteristics of the resonant frequencies, mode shapes, and internal forces are investigated for a corrugated ultrasonic piezoelectric transducer consisting of a few circular pieces each with a thickness of about 40 microm, radius of 5 mm, and span angle of 120 degrees.

Actuating Mechanism and Design of a Double Driving Feet Linear Ultrasonic Motor Using Longitudinal Vibration Transducer

A double driving feet linear ultrasonic motor using longitudinal vibration transducer is proposed in this paper. The stator of 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 intersected at the tip ends where located the driving feet. The horizontal and vertical vibrations of driving feet are generated by the longitudinal vibrations of horizontal and vertical transducers, respectively. Longitudinal vibrations are superimposed in the stator and generated elliptical motions at the driving feet. The two vibration modals of stator are gained with FEM, and the resonant frequencies of two vibration modals are degenerated by adjusting the structural parameters. Transient analysis of piezoelectric coupling states the good and strong elliptical motions of driving feet, and verifies the theoretical feasibility of proposed motor.

Working Principle and Design of a Cylindrical Standing Wave Ultrasonic Motor Using Cantilever Type Bending Transducer

A cylindrical standing wave ultrasonic motor using cantilever type bending transducer is proposed in this paper. There are four cantilevers outside the cylinder, and four PZT ceramics are set on each end surface of cantilevers. The bending mode of cylinder is excited by the bending vibration of transducers. Thus, a linear simple harmonic motion is achieved at the particle on the tooth. The working principle of proposed motor is analyzed. The cylinder and transducer are designed with FEM. The bending vibration modals of transducer and cylinder are degenerated. The transient analysis is developed to gain the vibration characteristics of stator, and the results indicate the proposed motor has potential good output characteristics. The results of this paper verify the theoretical feasibility and provide instructions for the development of proposed motor.

Acoustic coupler for skin contact hearing enhancement devices

There is provided hearing device improvements using modulation techniques adapted to the characteristics of auditory and vestibular hearing. One embodiment provides for extending hearing to the infrasonic range by extracting sounds from the high ambient noise in this range and applying them to a carrier in the ultrasonic quiet zone. Further extension of hearing into the ultrasonic range is provided by a modulation scheme which uses a fluid conduction coupler to match impedance for a vibration transducer applied to the skin. A variation on this embodiment integrates this ultrasonic hearing extension with normal acoustic headphones. Another embodiment compensates for high frequency hearing loss by a modulation scheme which uses middle ear resonance as an amplifier. A further embodiment combines ultrasonic transposition with wireless modulation to obtain secure communication.

Vibration characteristics of a circular cylindrical ceramic tube piezoelectric transducer with helical electrodes

We develop a 1-D mechanics model for coupled extensional and torsional vibrations of a circular cylindrical ceramic tube piezoelectric transducer with helical electrodes. A theoretical analysis of the electrically forced vibration of the tube is performed. Basic vibration characteristics of resonant frequencies, modes, and admittance are calculated and examined. The optimal orientation of the electrodes for exciting torsional modes is determined.

Actuating Mechanism and Analysis of a Square-Type Rotary Ultrasonic Stator Using Longitudinal Vibration Transducers

A square-type rotary ultrasonic stator using longitudinal vibration transducers is proposed. The proposed stator contains four longitudinal vibration transducers, which are located in square-type. Every longitudinal transducer includes two exponential shape horns located on each end. And the horns of adjacent transducers intersected at tip ends where located the driving feet. The longitudinal vibrations of transducers are excited by the longitudinal vibrations of PZT ceramics. Longitudinal vibrations of adjacent transducers are superimposed in the driving foot and generated elliptical trajectory. The actuating mechanism is analyzed, and the motion trajectories of driving feet are deduced. The stator is designed and analyzed by using FEM method. The vibration characteristic of stator is gained by transient analysis. Results indicate that the motion trajectories of the four driving feet have good consistency, and the proposed motor has potential good output characteristics. The results of this paper verify the theoretical feasibility and provide instructions for the development of proposed stator.

Analysis of multifrequency langevin composite ultrasonic transducers

The multimode coupled vibration of Langevin composite ultrasonic transducers with conical metal mass of large cross-section is analyzed. The coupled resonance and anti-resonance frequency equations are derived and the effective electromechanical coupling coefficient is analyzed. The effect of the geometrical dimensions on the resonance frequency, the anti-resonance frequency, and the effective electromechanical coupling coefficient is studied. It is illustrated that when the radial dimension is large compared with the longitudinal dimension, the vibration of the Langevin transducer becomes a multifrequency multimode coupled vibration. Numerical methods are used to simulate the coupled vibration; the simulated results are in good agreement with those from the analytical results. Some Langevin transducers of large cross-section are designed and manufactured and their resonance frequencies are measured. It can be seen that the resonance frequencies obtained from the coupled resonance frequency equations are in good agreement with the measured results. It is expected that by properly choosing the dimensions, multifrequency Langevin transducers can be designed and used in ultrasonic cleaning, ultrasonic sonochemistry, and other applications.

Design and Analysis of a Ring Type Traveling Wave Ultrasonic Motor Using Cantilever Type Composite Transducer

To take advantage of merits of higher output-power and efficiency of bolt-clamped transducer, a ring type traveling wave ultrasonic motor using cantilever type composite transducer is proposed in this paper. In this new design, two cantilevers are set for the coupling between ring and transducer. Two standing bending waves (with phase difference of π/2 on time and space, respectively) are generated in the ring by the bending-longitudinal vibrations of transducer. Thus, a flexural traveling wave can be excited. The working principle of proposed motor is analyzed. The stator is designed and analyzed with FEM, and the motion trajectories of nodes on the teeth are analyzed. The results of transient analysis verify the theoretical feasibility of proposed design. The results of this paper could guide the development of this new type of motor.

Toward Optimal Design of Piezoelectric Transducers Based on Multifunctional and Smoothly Graded Hybrid Material Systems

This work explores the design of piezoelectric transducers based on functional material gradation, here named functionally graded piezoelectric transducer (FGPT). Depending on the applications, FGPTs must achieve several goals, which are essentially related to the transducer resonance frequency, vibration modes, and excitation strength at specific resonance frequencies. Several approaches can be used to achieve these goals; however, this work focuses on finding the optimal material gradation of FGPTs by means of topology optimization. Three objective functions are proposed: (i) to obtain the FGPT optimal material gradation for maximizing specified resonance frequencies; (ii) to design piezoelectric resonators, thus, the optimal material gradation is found for achieving desirable eigenvalues and eigenmodes; and (iii) to find the optimal material distribution of FGPTs, which maximizes specified excitation strength. To track the desirable vibration mode, a mode-tracking method utilizing the ‘modal assurance criterion’ is applied. The continuous change of piezoelectric, dielectric, and elastic properties is achieved by using the graded finite element concept. The optimization algorithm is constructed based on sequential linear programming, and the concept of continuum approximation of material distribution. To illustrate the method, 2D FGPTs are designed for each objective function. In addition, the FGPT performance is compared with the non-FGPT one.

Power transmission through an unbounded elastic plate using a finite piezoelectric actuator and a finite piezoelectric power harvester

Recently thickness vibrations of an unbounded elastic plate with an unbounded piezoelectric actuator and an unbounded piezoelectric power harvester have been studied for power transmission through an elastic wall with various potential applications. In this paper we analyze the more realistic geometric configuration of a structure with finite piezoelectric transducers on unbounded plates operating with slowly varying thickness modes via the first-order lamination theory for plates. In addition to the output voltage and transmitted power, confinement and localization of the vibration energy is also studied which is of practical importance and can only be understood from analyzing vibrations of finite transducers.

Coupled vibration analysis of the thin-walled cylindrical piezoelectric ceramic transducers

Analysis of electromechanical transducers employing axially symmetric vibrations of piezoelectric ceramic thin-walled tubes of arbitrary aspect ratio is presented based on application of the energy method [B. S. Aronov, J. Acoust. Soc. Am. 117, 210-220 (2005)]. The suggestion made by Giebe and Blechshmidt [Ann. Physik, Ser. 5 18, 417-485 (1933)] regarding representation of a tube vibration as a coupled vibration of two partial systems is used to choose the assumed modes of the piezoceramic tube vibration, and the energy of the flexural deformations accompanying the extensional vibration of a tube is also taken into consideration. The Lagrange type equations describing the transducer vibrations are derived, and the equivalent electromechanical circuit is introduced that conveniently represents the solution. The resonance frequencies, effective coupling coefficients, and velocity distributions for differently poled piezoceramic tubes as functions of their height-to-diameter aspect ratio are calculated. The validity of the equivalent circuit is extended to the case that a piezoceramic tube is mechanically and acoustically loaded on the ends and acoustically loaded on its outer surface. The results of calculations are in good agreement with the results of experimental investigations.

ECG-based wireless home infant apnoea monitor

A safe and wireless system for infant apnoea monitoring and treatment is proposed. It consists of two separate modules that detect apnoea based on a microcontroller processing and transmitting signals to the remote unit using wireless communication arrangement. Depending on the ECG signal, this system records the infant's heart and respiratory rates. Recognition of the consecutive QRS complexes within the ECG signal helps in calculating these vitals. Abnormal breathing rate or heart rate (apnoea) triggers both an alarm system on the remote unit to inform parents of this abnormality and a treatment device that stimulates the infant to breathe using vibration transducer. Different ECG signals from the MIT-Physionet database were used to test the prototype. The system successfully extracted, analysed and transmitted required vitals and decisions to the receiving unit. Finally, the system was bench tested on 25 adult volunteers and 12 young children; voluntarily cessations of breathing were detected successfully for all subjects.

Capacitive electric musical instrument vibration transducer

A capacitive electric musical instrument vibration transducer contains one or more parallel plate variable capacitors. Each variable capacitor contains one vibrating variable capacitor plate, an electrically conducting surface that comprises, covers, or is embedded within an acoustically emitting vibrating surface on a musical instrument (such as a drumhead or soundboard), and one fixed variable capacitor plate comprising a rigid electrically conducting surface held a fixed distance away. When the instrument is played, the vibrating surface causes vibrations directly (without using airborne sound as an intermediary) in the vibrating variable capacitor plates, thus causing time-varying voltage oscillations in the parallel plate variable capacitors reflecting the vibrational state, and therefore the sound, of the instrument. An electric circuit in the transducer converts these voltage oscillations into the same kinds of signals produced by microphones and magnetic pickups.

A novel traveling wave ultrasonic motor using a bar shaped transducer

A novel traveling wave ultrasonic motor was proposed. The structure of the motor is rather simple and different from the conventional traveling wave ultrasonic motors. Its production processes are very convenient. It is composed of a stator constituted with a ring and a bar shaped transducer and two cone shaped rotors. The rotors were pressed on inner surface of the ring by means of a pre-pressure system. The bar shaped transducer has a sandwich-like configuration, where two sets of piezoelectric element are bolted. One set excites a longitudinal vibration of the bar, and the other set excites a flexural vibration of the bar. The ring’s traveling wave excited with the longitudinal vibration and the bending vibration of the bar transducer was simulated with FEM (finite element method). The prototype of the motor was made and investigated experimentally for its performance. Its maximum torque and rotating speed are 0.25 N · m and 50 r/min, respectively.

Percutaneous Versus Transcutaneous Bone Conduction Implant System

Percutaneous bone-anchored hearing aid (BAHA) is an important rehabilitation alternative for patients who have conductive or mixed hearing loss. However, these devices use a percutaneous and bone-anchored implant that has some drawbacks reported. A transcutaneous bone conduction implant system (BCI) is proposed as an alternative to the percutaneous system because it leaves the skin intact. The BCI transmits the signal to a permanently implanted transducer with an induction loop system through the intact skin. The aim of this study was to compare the electroacoustic performance of the BAHA Classic-300 with a full-scale BCI on a cadaver head in a sound field. The BCI comprised the audio processor of the vibrant sound bridge connected to a balanced vibration transducer (balanced electromagnetic separation transducer). Implants with snap abutments were placed in the parietal bone (Classic-300) and 15-mm deep in the temporal bone (BCI). The vibration responses at the ipsilateral and contralateral cochlear promontories were measured with a laser Doppler vibrometer, with the beam aimed through the ear canal. Results show that the BCI produces approximately 5 dB higher maximum output level and has a slightly lower distortion than the Classic-300 at the ipsilateral promontorium at speech frequencies. At the contralateral promontorium, the maximum output level was considerably lower for the BCI than for the Classic-300 except in the 1-2 kHz range, where it was similar. Present results support the proposal that a BCI system can be a realistic alternative to a BAHA.