Langevin Transducer Research Articles

Considerations in designing piezocomposite transducers and arrays for broadband sonar systems

The term broadband is commonly used to refer to the capability of a sonar system. Recent advances in signal processing and system electronics have re-defined capabilities for these systems and introduced new complex broadband pulse requirements for the sonar transducer. Advances in 1-3 piezocomposite technology have addressed this need through optimization of materials and innovative electroacoustic designs to provide high performance broadband solutions. Taking full advantage of this transducer technology requires careful consideration of the total system performance including dynamic range of receiver electronics, available transmit voltage/current/power, directivity and array configuration. This generalized study considers the design options available for optimizing transducers and arrays for broadband operation. Several Langevin or sandwich style Piezocomposite transducer configurations will be presented for both monostatic (two-way) and bistatic (separate receive and transmit) transducer systems and ...

Numerical analysis and noise detection for design optimisation of an ultrasonic transducer

The characteristics of a Langevin transducer are studied using a combination of numerical and experimental techniques, which reveal the effect of minor design changes on its performance. The experiments were performed using a microphone and voice-recording software capable of measuring frequencies up to 41 kHz; the obtained signal was analysed in MATLAB. A three-dimensional finite element model of the analysed transducer was also developed in a commercial finite element software ABAQUS/Standard and used for numerical simulations of its response to different excitation conditions. The transducer system was optimised using the results of noise detection and FEA.

Estimation of absolute sound pressure in a small-sized sonochemical reactor

A small-sized sonochemical reactor in which the absolute value of the sound pressure amplitude can be estimated from the vibration velocity of the transducer was investigated. The sound pressure distribution in the reactor and the relationship between the vibration velocity and the sound pressure amplitude were derived through Helmholtz wave equation. The reactor consists of a bolt-clamped Langevin transducer and a rectangular cell with a tungsten reflector. A 3λ/4-standing-wave-field was generated in the reactor to simplify the sound pressure distribution. The sound pressure distribution was measured from the optical refractive index change of water using a laser interferometer. The experimental and theoretical results showed a good agreement in the absolute value of the sound pressure amplitude, and it was confirmed that the sound pressure in the sonochemical reactor can be estimated from the input current of the vibrator.

Resonant-Type Smooth Impact Drive Mechanism Actuator with Two Langevin Transducers

A smooth impact drive mechanism (SIDM) is a unique piezoelectric actuator that is widely used as a camera focusing mechanism, cell phone lens movement mechanism, etc. This principle enables a compact driving mechanism; however, it cannot generate high-speed movement because a soft-type multilayered piezoelectric transducer (PZT) is utilized at off-resonant movement. This paper proposes a resonant-type SIDM actuator driven with hard-type PZTs to realize high-speed and powerful operation. The fundamental principle is also based on the conventional SIDM; therefore, a saw-shaped movement is required. To generate a high-power ultrasonic output, two Langevin transducers are adopted instead of a soft-type multilayered PZT. One Langevin transducer was a stator and the other was slider whose tip was adhered to a carbon fiber reinforced plastic (CFRP) rod. The CFRP rod was connected to the stator transducer with the frictional force. To obtain quasi-saw-shaped vibration, the longitudinal vibration for each Langevin transducer was excited and these movements were added at the connection point at the CFRP rod. In order to combine these vibration modes, the lengths of the stator and slider Langevin transducers were designed to make the resonant frequencies ratio to be 1:2. By using the proposed principle, the slider Langevin transducer was successfully driven with the speed of 0.11 m/s and the output force was 1.8 N with no load.

A travelling wave rotary motor driven by three pairs of langevin transducers

In this work, numerical simulations and experimental measurements carried out on a high-power ultrasonic motor are presented. The proposed motor is composed of an annular shaped stator and two cone-shaped rotors. The rotors are pressed into contact with the edges of the inner surface of the stator by means of a pre-stress system. A traveling rotating wave is generated in the stator by three pairs of Langevin transducers suitably shifted both in space and time. Each transducer is designed to excite radial nonaxisymmetric modes in the ring. The motor has been effectively clamped to the housing by using two flanges passing through the middle plane of 2 transducers. Finite element analysis was employed to evaluate two different configurations of the motor, both using 6 driving transducers, and to analyze the effect of the flange on the design and on the performance of the transducer. Experimental measurements carried out on a manufactured prototype show that the proposed motor exhibits greatly improved performance in terms of output torque and mechanical power compared with similar previous prototypes which use fewer driving transducers and a different clamping system. The motor weighed 0.67 kg, and had a working frequency of 23.6 kHz, maximum rotational speed of 116 rpm, and static torque of 0.94 Nm.

Stepped-plate transducer as an energy transmitter

Power transmission through acoustic energy may be useful in such cases as supplying power to wireless small sensors. In the case, the radiation and reception power efficiency is important. Even in ultrasonic frequency bands, the power efficiency of most acoustic radiators in air is not high enough. The stepped-plate ultrasonic transducers, introduced by Gallego-Juarez etal. [Ultrasonics 16, 267–271(1978)], may be a good candidate for the radiator for this purpose because it can effectively generate highly directive, large-amplitude, ultrasonic sounds in air. The transducer consists of langevin transducer that causes wave generation, mechanical amplifier, and stepped radiation plate. Although it is reported to achieve 80% of power efficiency, it is not reported how to achieve maximum power efficiency. For design of large-amplitude, high-efficiency stepped-plate transducer, the design of not only individual parts but also system integration of entire transducer is important. In this research, we developed an analytical model for the whole transducer by combining continuum models of each parts and found proper design parameters for the radiation power and the power transmitting efficiencies. Then, we seek the optimal design for maximizing power efficiency through parametric analyses, and the results are confirmed through finite element method analysis. [Work supported by ETRI (South Korea).]

A Strategy for Delivering High Torsionality in Longitudinal-Torsional Ultrasonic Devices

A composite longitudinal-torsional vibration mode has applications in ultrasonic motors, ultrasonic welding and ultrasonic drilling. There are two ways to obtain this vibration behaviour using a single transducer, namely (i) coupling of a longitudinal and a torsional mode, which is known to be difficult; and (ii) degenerating a longitudinal mode to deliver longitudinal-torsional behaviour at the horn tip. A mode-degenerating horn is achieved by incorporating helical or diagonal slits in an otherwise traditional exponential horn driven by a Langevin transducer. However, it is often difficult with this configuration to avoid coupling of unwanted bending modes, low responsiveness, and loss of ultrasonic energy due to boundaries between tuned components. Therefore, in this study the mode-degenerating characteristics are achieved by incorporating the helical slits and exponential geometry features in the front mass of the transducer itself. Finite element analysis and vibration experimental analysis show that this strategy prevents coupling of bending modes, increases responsiveness, and reduces energy losses. Most importantly the transducer delivers a very high torsionality.

Modeling characterization and optimization design for PZT transducer used in Near Field Acoustic Levitation

An acoustic actuator with large radiation surface has been used in a non-contact levitation system. The actuator is composed of a Langevin transducer and a disk-shape radiator. A comprehensive modeling approach has been developed to simulate electrical and mechanical characterization. A coupled-field finite element analysis has been performed considering the vibrator with flexural mode. Identical experimental conditions were used in the simulation to investigate size effect and optimize the transducer design. The stimulated results show good agreement with experimental measurements. This model may be employed to facilitate the analysis and optimization of Near Field Acoustic Levitation transducer assemblies. Moreover, this paper demonstrated the important role that modeling plays in the design, fabrication and optimization of coupled transducers.

Resonant-type Smooth Impact Drive Mechanism (SIDM) actuator using a bolt-clamped Langevin transducer

The Smooth Impact Drive Mechanism (SIDM) is a linear piezoelectric actuator that has seen practically applied to camera lens modules. Although previous SIDM actuators are easily miniaturized and enable accurate positioning, these actuators cannot actuate at high speed and cannot provide powerful driving because they are driven at an off-resonant frequency using a soft-type PZT. In the present study, we propose a resonant-type SIDM using a bolt-clamped Langevin transducer (BLT) with a hard-type PZT. The resonant-type SIDM overcomes the above-mentioned problems and high-power operation becomes possible with a very simple structure. As a result, we confirmed the operation of resonant-type SIDM by designing a bolt-clamped Langevin transducer. The properties of no-load maximum speed was 0.28 m/s at driving voltages of 80 V p-p for 44.9 kHz and 48 V p-p for 22.45 kHz with a pre-load of 3.1 N

High nonlinearities in Langevin transducer: A comprehensive model

The design and simulation of power transducers are difficult since piezoelectric, dielectric and elastic properties of ferroelectric materials differ from linear behavior when driven at large levels. This paper is devoted to modeling of a resonant power transducer at a high level of dynamic mechanical stress. The power transducer is subjected to a sine electrical field E of varying frequency which was considered as the excitation of the transducer. The mechanical equation of the piezoelectric element is written using electrostriction. The dielectric part is written as a nonlinear function of an equivalent electric field including stress influence (scaling relationship between electric field and mechanical stress). Using various simulations, we show then that typical resonance nonlinearities are obtained, such as jump phenomenon of transducer speed amplitude and phase, resonance peak that become asymmetric, and diminution of mechanical quality factor. As a consequence, we state that those typical nonlinearities are only due to dielectric nonlinearities, in good correlation with typical ferroelectric behavior. Moreover, this demonstrates the usefulness of scaling relationships in ferroelectrics, which explain static depoling under stress and butterfly strain hysteresis loop. The same scaling law gives here several nonlinearities for resonant transducers as well.

Dynamic modeling of thickness-mode piezoelectric transducer using the block diagram approach

This paper aims to provide an alternative method to determine the characteristics of a piezoelectric transducer from measurement. A block diagram approach is proposed to analyze the dynamic characteristics of a thickness-mode piezoelectric transducer at its resonance frequency. Based on the feedback loop framework, the input–output relations of the electromechanical interaction of the transducer are described in terms of linear block diagram models. Furthermore, the closed-loop relations from external force to vibration velocity and electric current from generated voltage are easily found by Mason’s rule to characterize the equivalent mechanical admittance and electrical impedance, respectively. An example of a Langevin transducer with 28.15 kHz resonance frequency is illustrated for dynamics analysis. The frequency responses of the piezoelectric transducer, resulting from a force and current input, are respectively measured to identify the system parameters of the feedback model. The experimental results demonstrate the effectiveness of the proposed method.

A Novel L-B Hybrid Langevin Transducer Type Linear Ultrasonic Motor With Modal Coupling Reducing Configuration

For most longitudinal and bending hybrid linear ultrasonic motor, there exists an inherent coupling effect between two modals due to the structure defect, which shows the phenomenon of one phase piezoceramic exciting the other phase vibration or vice versa. A new modal decoupling motor was proposed with the longitudinal piezoceramics positioned in the middle part of Langevin transducer and the bending piezoceramics at longitudinal antinodal plane. The prototype, designed with frequency tuning method, showed obvious modal coupling reduction in impedance characteristics and laser vibrometer measurement, and also surpass previous motor in output performance.

Modeling of Piezoelectric Langevin Transducers by Using Mixed Transfer Matrix Methods

In the modeling of piezoelectric Langevin transducers using usual transfer matrix methods, some simplifications have been adopted. This leads to reduction of the model quality. A mixed transfer matrix method is employed in the modeling of Langevin transducers, where the pre-stressed bolt is modeled as a separate four-pole element, which is connected to other elements in parallel. Based on the mixed transfer matrix method, the four (six)-pole element description of the piezoelectric Langevin transducer is built up and the total transfer matrix relation is derived. The resonance frequencies of the transducer are calculated and then measured using the impedance analyzer (HP4192). Experimental result shows that the mixed transfer matrix method has better modeling quality than the usual transfer matrix method for the vibration analysis of piezoelectric Langevin transducers.

Various Aspects of the Placement of a Piezoelectric Material in Composite Actuators, Motors, and Transducers

Piezoelectric materials find wide application in technical systems. Most often, a combination of piezoelectric and other materials is advantageous. The position and the amount of the piezoelectric material within the overall system depends on various aspects like maximum mechanical output to the load, maximum electromechanical efficiency of the system, maximum utilization of the piezoelectric material, minimum self-heating of the piezoelectric material, and controllability of the system, which might be key aspects for the optimisation of the system design. For a composite longitudinal vibrator (bolted Langevin transducer), which is a base for many technical applications, this contribution shows in detail, how above mentioned aspects depend on the position and volume of the piezoelectric material related to the mode shape.

Designing a Hollow Langevin Transducer for Ultrasonic Coring

A number of architectures for a hollow Langevin ultrasonic transducer are proposed and evaluated. One of these is optimised by finite element modelling and is then manufactured and analysed experimentally. The preload on the transducer ceramics is increased and the effect on the performance is measured. At maximum preload the results of an experimental modal analysis are used to determine the natural frequency and response of both the operating longitudinal mode and unwanted bending modes. The performance of the hollow transducer is compared to a solid commercial transducer containing the same volume of piezoceramic material. The efficiency is shown to be comparable. Higher ultrasonic displacement amplitudes are achieved with the hollow transducer although a lower Q-factor is found.

Noncontact ultrasonic transportation of small objects over long distances in air using a bending vibrator and a reflector

Ultrasonic manipulation of small particles, including liquid droplets, over long distances is discussed. It is well known that particles can be trapped at the nodal points of an acoustic standing wave if the particles are much smaller than the wavelength of the standing wave. We used an experimental setup consisting of a 3-mm-thick, 605-mm-long duralumin bending vibrating plate and a reflector. A bolt-clamped Langevin transducer with horn was attached to each end of the vibrating plate to generate flexural vibrations along the plate. A plane reflector with the same dimensions as the vibrating plate was installed parallel to the plate at a distance of approximately 17 mm to generate an ultrasonic standing wave between them and to trap the small particles at the nodal lines. The acoustic field and acoustic radiation force between the vibrator and reflector were calculated by finite element analysis to predict the positions of the trapped particles. The sound pressure distribution was measured experimentally using a scanning laser Doppler vibrometer. By controlling the driving phase difference between the two transducers, a flexural traveling wave can be generated along the vibrating plate, and the vertical nodal lines of the standing wave and the trapped particles can be moved. The flexural wave was excited along the vibrator at 22.5 kHz. A lattice standing wave with a wavelength of 35 mm in the length direction could be excited between the vibrator and the reflector, and polystyrene spheres with diameters of several millimeters could be trapped at the nodal lines of the standing wave. The experimental and calculated results showed good agreement for the relationship between the driving phase difference and the positions of the trapped particles. Noncontact transportation of the trapped particles over long distances could be achieved by changing the driving phase difference. The position of the trapped particles could be controlled to an accuracy of 0.046 mm/deg. An ethanol droplet could also be trapped and moved.

FE analysis and experimental evaluation of the performance of a travelling wave rotary motor driven by high power ultrasonic transducers

Ultrasonic motors have been exploited mainly in low power and low duty cycle applications. In aerospace and automotive applications, there is also the need for motors able to provide high torque but employed at very low duty cycle. In this work numerical simulations and experimental measurements carried out on a high power ultrasonic motor are presented. The proposed motor is composed of a annular shaped stator and two light cone shaped rotors. The rotors are pressed in contact to the borders of the inner surface of the stator by means of an opportune pre-stress system. A travelling rotating wave is generated in the stator by two and four Bolted Langevin Transducers, opportunely placed on the lateral surface of the stator. Each transducer is designed to excite in the ring radial nonaxisymmetric modes. The effective generation of the travelling wave in the stator, with both two and four driving transducers, has been accurately simulated with a FEM software. A prototype of the motor has been constructed and experimentally characterized. Comparisons between simulation and measurements have shown a satisfactory agreement. The improvement of motor performances achieved by increasing the number of driving transducers is analyzed and discussed.

Oscillation propagating in non-contact linear piezoelectric ultrasonic levitation transporting system---from solid state to fluid media

Non-contact ultrasonic motors (USM) show potential for future use, especially in the industrial fields because of its simple structure and quick response. It is therefore important to comprehensively understand their theoretical background so as to push this research forward. In this study, we shall fully explain and deduce the driving mechanism of a linear ultrasonic levitation transporting system. Oscillation equations from the initial exciting Langevin transducer and flexural traveling wave propagation on the linear guide were first established. Then the squeezing fluid movement between the linear guide and the levitating slider was analyzed. Next, after being excited by the progressing wave under corresponding boundary conditions, the related tangential velocity of the middle flow field was obtained. Finally, the validated experiment was set up to test slider velocity.

1A2-B05 超音波振動を利用した基板の非接触搬送技術(第三報) : ガラス基板の非接触搬送特性

In recent years, various boards such as glass substrate and semiconductor wafers have become larger. Therefore, fracture of substrates under conventional contact transportation is unavoidable. In order to solve these problems, a new non-contact transportation technology is proposed. The board is levitated by aerostatic force and held by the holding unit constructed by oscillating plate actuated by bolted Langevin transducer. In this paper, two oscillating plates are proposed. One is 7 times wider than conventional oscillating plate. The other, which is called comb type has 6 slits to define individual oscillation. The comb type has holding performance with spring constant of 17mN/mm. The dynamic spring constant, which was verified by undamped natural frequency for step response, was comparable to static spring constant.

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.