EP3335806A1 - Procédé ainsi que dispositif de génération d'ondes ultrasoniques - Google Patents

Procédé ainsi que dispositif de génération d'ondes ultrasoniques Download PDF

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Publication number
EP3335806A1
EP3335806A1 EP17188290.5A EP17188290A EP3335806A1 EP 3335806 A1 EP3335806 A1 EP 3335806A1 EP 17188290 A EP17188290 A EP 17188290A EP 3335806 A1 EP3335806 A1 EP 3335806A1
Authority
EP
European Patent Office
Prior art keywords
transducer
signal
ultrasonic transducer
ultrasonic
function
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP17188290.5A
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German (de)
English (en)
Inventor
David BÖTTGER
Benjamin STRASS
Bernd Wolter
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Original Assignee
Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
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Filing date
Publication date
Application filed by Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV filed Critical Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Publication of EP3335806A1 publication Critical patent/EP3335806A1/fr
Withdrawn legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/0207—Driving circuits
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B2201/00—Indexing scheme associated with B06B1/0207 for details covered by B06B1/0207 but not provided for in any of its subgroups
    • B06B2201/30—Indexing scheme associated with B06B1/0207 for details covered by B06B1/0207 but not provided for in any of its subgroups with electronic damping
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B2201/00—Indexing scheme associated with B06B1/0207 for details covered by B06B1/0207 but not provided for in any of its subgroups
    • B06B2201/40—Indexing scheme associated with B06B1/0207 for details covered by B06B1/0207 but not provided for in any of its subgroups with testing, calibrating, safety devices, built-in protection, construction details
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B2201/00—Indexing scheme associated with B06B1/0207 for details covered by B06B1/0207 but not provided for in any of its subgroups
    • B06B2201/50—Application to a particular transducer type
    • B06B2201/55—Piezoelectric transducer

Definitions

  • ultrasonic transducers are often used for non-contact and non-destructive ultrasonic testing of materials and components and convert function of a transmitter or actuator electrical input signals Ultrasonic waves and in function of a receiver or sensor to minimal pressure fluctuations of ultrasonic waves mostly in air into electrical output signals.
  • thermo-acoustic transducer similar to the air ultrasonic signal.
  • an electrical drive signal on the basis of the determined transfer function G s (z) and a predetermined second location function or a temporal differentiation derived therefrom time-dependent function determined.
  • the ultrasonic transducer is activated with the determined drive signal.
  • the transfer function G s (z) to be determined in the first step determines the accuracy of the electroacoustic ultrasonic transducer with which the spatial and temporal deflection of the transducer surface for the purpose of sound generation deviates from the shape and the time profile of the initial electrical input signal.
  • the electroacoustic ultrasonic transducer were excited with an electrical input signal in the form of a single sine wave and then the transducer surface was likewise deflected in the form of a sine wave, i. each surface area or surface point of the transducer surface would make the deflection of a phase point of a sine wave substantially orthogonal to the transducer surface, without any ringing of the transducer surface, such an ultrasonic transducer would convert the electrical input signals into a sound wave identical at least to the shape and frequency of the input signal, i. the transfer function would correspond to a maximum accuracy.
  • the ultrasound transducer-specific transmission properties determined in the first step, which are reflected in the transfer function, are taken as a basis.
  • a second position function or a second time-dependent function derived therefrom by temporal differentiation is predetermined, which, for example, has the form of a sine, square, pulse or step function and is intended to describe a desired oscillation behavior of the transducer surface ultimately determines the ultrasound wave to be sounded by the ultrasonic transducer. If, for example, it is intended to emit a single sinusoidal ultrasonic wave from the ultrasonic transducer, then the second spatial function corresponds to a sinusoidal function defining a single sine wave.
  • the activation of the ultrasonic transducer can be done in two ways.
  • an output signal is generated by a signal generator unit, which is supplied as input to a filter unit.
  • the filter unit transforms the input signal on the basis of the determined transfer function in the electrical drive signal, which ultimately activates the electroacoustic ultrasonic transducer.
  • This case makes no special demands on the signal generator, especially as the generation of the electrical drive signal within the filter unit, which is connected between the signal generator and the ultrasonic transducer, is generated.
  • the solution according to the method can be carried out in a particularly advantageous manner with a device which provides a signal generator which generates an output signal which is an input signal of a filter unit, which transforms the input signal on the basis of a transfer function and generates a transformed output signal, which controls the electroacoustic Ultrasonic transducer activated.
  • the signal generator unit used is an arbitrary generator which, based on the transfer function, generates a drive signal which directly drives the ultrasonic transducer, the transfer function being selected such that the preferably piezoelectric ultrasonic transducer generates sinusoidal ultrasonic waves.
  • the device is suitable for non-destructive ultrasound examination of an object in which the ultrasonic transducer generates ultrasonic waves by means of electrical control signals, which are reflected at, for example, defects in the test object and received by the same or another ultrasonic transducer and in turn transformed into electrical reception signals ,
  • FIG. 1 an apparatus for generating ultrasonic waves 4 is shown, which comprises a signal generator 1 which generates an electrical drive signal which directly activates an electroacoustic ultrasonic transducer 2.
  • the electroacoustic ultrasonic transducer 2 is a piezoelectric ultrasonic transducer whose Transducer-specific signal transmission characteristics by a transfer function G s (z) are characterized, indicating the signal ratio of the prevailing at the output of the ultrasonic transducer output signal and the input of the ultrasonic transducer input signal.
  • a device for generating ultrasonic waves 4 which comprises a signal generator 1 and a filter unit 3, whose input signal is the output signal of the signal generator 1, and an electro-acoustic ultrasonic transducer 2, whose input signal is the output signal of the filter unit 3.
  • the signal generator unit 1 is conventional and only capable of generating electrical signals in the form of sine or square or pulse or step functions.
  • the filter unit 4 provides a transfer function which corresponds at least approximately to the inverse transfer function G s - 1 (z) of the ultrasonic transducer.
  • the inverse transfer function G s -1 (z) is for this purpose determined from the location-time function or the speed-time function of at least part of the sound-generating transducer surface 11 of the ultrasonic transducer 2 in response to the drive signal of the ultrasonic transducer 2.
  • the location-time signal, velocity-time signal, etc. are similarly suitable for determining G s (z).
  • the location-time signal, speed-time signal, etc. are the measurement signals of the location-time function, speed-time function, etc.
  • the invention returns the generated air ultrasonic wave to the surface vibration of the ultrasonic transducer and determines the correlation to the applied to the ultrasonic transducer electrical drive signal.
  • the correlation determined in this case is used for the modulation or filtering of the electrical control signal, so that the desired air ultrasonic wave originates from the control signal.
  • an air ultrasonic wave generated by an ultrasonic transducer has a course similar to the surface oscillation of the ultrasonic transducer.
  • the oscillation of the surface 11 of the ultrasonic transducer 2 can be measured, for example, with a laser Doppler vibrometer (LDV). Such a measurement confirms the direct relationship between the air ultrasonic wave of the ultrasonic transducer and the surface vibration of the sound generating transducer surface 11.
  • LDV laser Doppler vibrometer
  • ultrasound transducers upon excitation with one or more sinusoidal or square waves, form a transient and ringing process on the transducer surface.
  • the ultrasonic ultrasound field generated by the ultrasonic transducer follows the movement of the transducer surface.
  • the generated air ultrasonic wave can thus be attributed to the surface oscillation of the ultrasonic transducer and set in correlation to the drive signal, in particular a voltage applied to the ultrasonic transducer electrical voltage.
  • the surface-reflected signal then has a temporal separation of the fault-reflected signal and the drive signal.
  • the differential equation in the form of the transfer function of the ultrasound transducer used is determined in a first step.
  • a measurement setup which is preferably used to determine the transfer function is located in a vibration-dampened room in which both the floor slab of the room and the table tops of the electronic appliances are mounted in a vibration-damped manner.
  • a signal generator By a signal generator, the drive signal to the ultrasonic transducer, in particular a piezo-ultrasonic transducer is provided.
  • An oscilloscope is used to measure and store the drive signal.
  • the forming surface vibration at the ultrasonic transducer is quantified by means of a laser Doppler vibrometer.
  • the ultrasonic transducer is understood as a SISO system (single-input and single-output system).
  • SISO system single-input and single-output system
  • a piezoelectric ultrasonic transducer with focused piezoelectric ceramic is operated at a natural resonance frequency of 520 kHz.
  • the natural frequency is measured, for example, by means of FFT measurement of the laser Doppler vibrometer measuring signal during frequency sweep excitation of the piezoelectric ultrasonic transducer.
  • the drive signal for the single input of the SISO system is a sine wave voltage signal with a maximum frequency of 20 MHz.
  • the piezoelectric ultrasonic transducer is driven with a signal in burst mode, i. with periodic rest periods of at least 1 ms. As a result, the heat generation is kept as low as possible on the ultrasonic transducer.
  • the Laser Doppler Vibrometer consists of a laser vibrometer head, the so-called “scanning head", which acts as a transmitter and receiver of the laser light beams reflected on the piezoelectric ultrasonic transducer to be measured functions.
  • a “controller” of the LDV, the "junction box” and the “PC” process the measured signals of the LDV and enable their storage as well as visualization.
  • a measuring point 10a ... 10n from area 11 of the FIG. 3 selected.
  • This area is characterized by a relatively homogeneous decaying oscillation amplitude.
  • the area around the geometric center of gravity of the sound-generating surface differs only in the amplitude curve.
  • the edge areas swing the least, which is due to the vibration-damping clamping with the housing.
  • a voltage at the piezoelectric ultrasonic transducer leads to an introduced energy that corresponds to the integral area of the voltage over time (assuming current flow is constant).
  • FIG. 5 shows the voltage curve at the piezoelectric ultrasonic transducer when connecting a rectangle with the amplitudes 10 V, 5 V and signal lengths of the rectangle of 150 ns, 290 ns and 300 ns.
  • Table 1 Representation of the surface integrals and the relationships with respect to the voltage curve O1, 02, 03, 04, see FIG. 5.
  • the surface integral ratios are in linear relation to the signal length. It is obsolete whether the applied voltage or the signal length is varied to change the introduced energy. Both cases involve the same change of area integral ratios.
  • the signal length should not exceed half the period of the self-resonant frequency of the piezo-ultrasonic transducer when driving.
  • FIG. 6 In FIG. 6 are the forming vibrations G1, G2, G3 of the piezo surface at excitation O1, O2, O3 ( FIG. 5 ) shown.
  • the following table shows these in relation to each other.
  • Table 2 Representation of the speed and the ratios related to the course of the speed. Measurement Speed in m / s Speed ratio to G1 (GVG1) in% Deviation abs (GVG1-FVQ1) in% G1 0.05373 100 0 G2 0.04518 84.08 12.2 G3 0.03053 56.82 9.57
  • An applied AC voltage leads to the piezoelectric ultrasonic transducer to a harmonic sound pressure in the air, which is significantly influenced by the speed of the surface of the piezoelectric ultrasonic transducer.
  • a system description in the form of a transfer function for the piezoelectric ultrasonic transducer can be determined.
  • This transfer function contains all necessary mathematical relationships in frequency space for an LZI system (linear time invariant system) between the input and output signal. The fact that the transfer function can be used to calculate all relevant quantities of the system allows conclusions to be drawn about the amplitude response, the phase shift and the stability of the analyzed system.
  • the input of the searched system is determined by the applied voltage.
  • a selected measuring point of the sound-generating surface approximately halfway between clamping and geometric center of gravity of the surface has a relatively homogeneous compared to other measuring points of its surroundings exponentially decaying attenuation. This is going out FIG. 8 clearly showing the surface vibration as surface velocity at the measuring point of the piezoelectric ultrasonic transducer.
  • the two recorded data sets are then linked by the oscilloscope and the laser vibrometer. This is done by first identifying the start time of both beginning oscillations and shifting them to each other so that they start at the same time. Additionally, the sampling frequency of both data sets is different, thus downsampling of the higher scanned oscilloscope data (2.5 GHz) to the laser vibrometer data (102.4 MHz) is required.
  • the data are presented as filtered voltage and velocity signals for transfer function determination.
  • the records were in FIG. 9 normalized by a mean value filter which compensates for the slight offset shift of the voltage signal. Further, by applying a normalizing filter, the exciting voltage 40 and the surface speed signal 41 can be better compared with each other.
  • B (z) and F (z) are here polynomials, which are to be understood as a black box. This is to be determined with regard to the smallest possible disturbance e (k).
  • FIG. 10 is the pole-zero diagram of the detected transfer function of the piezoelectric ultrasonic transducer using LabVIEW in the complex z-plane. From this it can be seen that all poles and zeros are within the unit circle. The system can thus be called stable.
  • the transfer function can be described as sufficiently accurate because the later active Generation of short oscillations, the temporal deviation and amplitude deviation are marginal at 2 ⁇ 10 -5 s.
  • the inverse transfer function contains the same parameters A to O and z as the transfer function G (z). The only difference is that the numerator and denominator have been swapped. The previous poles are reset by inverting and vice versa. Subsequently, the inverse transfer function can be used to calculate the input signal to be applied to the piezoelectric ultrasonic transducer as a voltage in order to generate a defined output oscillation.
  • FIG. 12 shows the desired (predicted) output oscillation. If possible, the piezoelectric ultrasonic transducer should only perform a sinusoidal oscillation, measured on the basis of the surface velocity. The signal after FIG. 12 is then on the one hand, the input signal for the inverse transfer function and the desired piezo ultrasonic transducer surface speed.
  • FIG. 15 A more detailed comparison of the forming sinusoidal (51) and predicted surface velocities (50) is shown FIG. 15 .
  • the ringing time of an airborne sound transducer, an ultrasonic transducer can be minimized by active excitation.
  • the ultrasonic transducer is characterized by means of laser vibrometry, the surface oscillation of the piezoelectric ultrasonic transducer used is analyzed in detail, and the mathematical system-theoretical approaches determine the transfer function of the overall system. By calculating the inverse transfer function and continuing the input and output signals of these, it is possible to influence the forming surface vibration of a piezoelectric ultrasonic transducer targeted.
  • the findings allow for a defined control of the airborne sound transducer and allow the generation of a similar vibration behavior as that of a thermo-acoustic ultrasonic transmitter.
  • the generation of a single sine wave at the surface of an airborne sound transducer with greatly reduced ringing is achieved.
  • the air ultrasonic wave propagating from the ultrasonic transducer can be attributed to the surface movements of the piezoceramic surface.
  • the generation of any air ultrasonic signal waveforms is possible.
  • the ultrasonic transducer 2 for example, using a signal generator 1 and a filter unit 3 according to the in FIG. 1b explained arrangement, typically regulated voltage or voltage controlled.
  • the ultrasonic transducer 2 is charge controlled, see FIG. 16a , where the piezo actuator is connected between a regulator and a capacitor, or current-controlled, see FIG. 16b wherein the piezo actuator is connected between a regulator and an ohmic resistor, whereby the nonlinearity of, for example, a piezoelectric ultrasonic transducer is reduced.
  • the piezoelectric actuator of the ultrasonic transducer a parallel circuit of a capacitor C and a predominantly ohmic resistor R connected in series, see FIG. 16c .
  • This series-connected RC element is dimensioned so that in the frequency range f u of the ultrasound, the impedance of C is less than the impedance of R, but at the repetition frequency f w at intermittent (burst) operation of the piezo actuator, the impedance of R is smaller than the impedance of C.
  • the controller behaves in the frequency range of the ultrasound as a charge controller and in the frequency range of the repetition frequency as a current regulator.
  • Useful values for R and C satisfy the following system of equations: R ⁇ 1 j 2 ⁇ f u C and R > 1 j 2 ⁇ f w C

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
EP17188290.5A 2016-12-16 2017-08-29 Procédé ainsi que dispositif de génération d'ondes ultrasoniques Withdrawn EP3335806A1 (fr)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113499097A (zh) * 2021-07-09 2021-10-15 西安交通大学 一种无创三维经颅脑组织黏弹性和流性成像装置及方法
WO2023072486A1 (fr) * 2021-10-29 2023-05-04 Endress+Hauser Flowtec Ag Capteur à ultrason pour dispositif de mesure à ultrason, et dispositif de mesure à ultrason

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4156823A (en) * 1977-05-06 1979-05-29 Hideyuki Suzuki Method for damping an ultrasonic transducer
US5253530A (en) * 1991-08-12 1993-10-19 Letcher Iii John H Method and apparatus for reflective ultrasonic imaging
DE10136628A1 (de) * 2001-07-26 2003-02-20 Valeo Schalter & Sensoren Gmbh Verfahren zum Betrieb eines Ultraschallwandlers zum Aussenden und Empfangen von Ultraschallwellen mittels einer Membran
EP2004977B1 (fr) 2006-04-13 2011-01-19 Société Technique pour l'Energie Atomique TECHNICATOME Convertisseur thermo-acoustique et générateur d'énergie électrique comprenant un convertisseur thermo-acoustique.
WO2013023987A1 (fr) * 2011-08-17 2013-02-21 Empa, Eidgenössische Materialprüfungs- Und Forschungsanstalt Procédé par ultrasons sans contact, couplé à l'air, pour la détermination non destructrice des défauts dans des structures stratifiées
US20160315247A1 (en) * 2014-02-28 2016-10-27 The Regents Of The University Of California Variable thickness diaphragm for a wideband robust piezoelectric micromachined ultrasonic transducer (pmut)

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4156823A (en) * 1977-05-06 1979-05-29 Hideyuki Suzuki Method for damping an ultrasonic transducer
US5253530A (en) * 1991-08-12 1993-10-19 Letcher Iii John H Method and apparatus for reflective ultrasonic imaging
DE10136628A1 (de) * 2001-07-26 2003-02-20 Valeo Schalter & Sensoren Gmbh Verfahren zum Betrieb eines Ultraschallwandlers zum Aussenden und Empfangen von Ultraschallwellen mittels einer Membran
EP2004977B1 (fr) 2006-04-13 2011-01-19 Société Technique pour l'Energie Atomique TECHNICATOME Convertisseur thermo-acoustique et générateur d'énergie électrique comprenant un convertisseur thermo-acoustique.
WO2013023987A1 (fr) * 2011-08-17 2013-02-21 Empa, Eidgenössische Materialprüfungs- Und Forschungsanstalt Procédé par ultrasons sans contact, couplé à l'air, pour la détermination non destructrice des défauts dans des structures stratifiées
US20160315247A1 (en) * 2014-02-28 2016-10-27 The Regents Of The University Of California Variable thickness diaphragm for a wideband robust piezoelectric micromachined ultrasonic transducer (pmut)

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
M. DASCHEWSKI: "DE GRUYTER Oldenbourg", vol. 82, 2015, article "Resonanzfreie Messung und Anregung von Ultraschall", pages: 156 - 166
PIQUETTE J C: "METHOD FOR TRANSDUCER TRANSIENT SUPPRESSION.I: THEORY", THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA, AMERICAN INSTITUTE OF PHYSICS FOR THE ACOUSTICAL SOCIETY OF AMERICA, NEW YORK, NY, US, vol. 92, no. 3, September 1992 (1992-09-01), pages 1203 - 1213, XP000307190, ISSN: 0001-4966, DOI: 10.1121/1.403970 *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113499097A (zh) * 2021-07-09 2021-10-15 西安交通大学 一种无创三维经颅脑组织黏弹性和流性成像装置及方法
CN113499097B (zh) * 2021-07-09 2022-12-09 西安交通大学 一种无创三维经颅脑组织黏弹性和流性成像装置及方法
WO2023072486A1 (fr) * 2021-10-29 2023-05-04 Endress+Hauser Flowtec Ag Capteur à ultrason pour dispositif de mesure à ultrason, et dispositif de mesure à ultrason

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