WO2013037880A1 - Procédé de mesure des propriétés dynamiques d'une structure mécanique - Google Patents
Procédé de mesure des propriétés dynamiques d'une structure mécanique Download PDFInfo
- Publication number
- WO2013037880A1 WO2013037880A1 PCT/EP2012/067930 EP2012067930W WO2013037880A1 WO 2013037880 A1 WO2013037880 A1 WO 2013037880A1 EP 2012067930 W EP2012067930 W EP 2012067930W WO 2013037880 A1 WO2013037880 A1 WO 2013037880A1
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- WO
- WIPO (PCT)
- Prior art keywords
- measurement signal
- frequency
- transient phase
- excitation
- profile
- Prior art date
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M5/00—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings
- G01M5/0066—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by exciting or detecting vibration or acceleration
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M7/00—Vibration-testing of structures; Shock-testing of structures
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H11/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by detecting changes in electric or magnetic properties
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H13/00—Measuring resonant frequency
Definitions
- the present invention belongs to the field of calculating structures.
- it relates to a method for measuring the dynamic properties of a mechanical structure, possibly associated with a method for detecting a modification of these properties greater than a given threshold.
- the invention relates to a method for measuring the dynamic properties of a mechanical structure, the method using an acceleration sensor transmitting acceleration (or speed or displacement) data at regular intervals to a computing device, in the form of a measurement signal transmitted through a network.
- the method for measuring dynamic properties preferably comprises:
- a step 320 of identifying the real transient phase profile with a reference transient phase profile extracted from a database the identification being carried out according to a determined distance criterion.
- a time-frequency map of the measurement signal is produced, then zones of interest are identified in the time-frequency map. which are the zones of maximum amplitude of the measurement signal and a frequency of interest is defined as the frequency of an area of interest.
- the filtering of the measurement signal around a frequency of interest is carried out so as to retain in the filtered measurement signal only the mode or the resonance around the frequency of interest.
- this filtering of the signal in the frequency domain is carried out by transforming the fourrier, then by multiplying the Fourier transform of the measurement signal by the Fourier transform of the filter to be applied, and then by the inverse Fourier transform of the product.
- the method comprises, prior to the step of calculating the real transient phase profile, steps in which:
- the dominant frequency of the filtered measurement signal is identified, advantageously by the search for a maximum of the Fourier transform of said filtered measurement signal,
- the local extremums of the filtered measurement signal (output of 130) are identified, this identification comprising a local extremum by half-oscillation of the filtered measurement signal,
- the phase of the filtered measurement signal is calculated:
- the method comprises a step in which:
- a basic model is chosen to carry out the simulations, which is, in a particular implementation, a harmonic oscillator model with a degree of freedom that represents either an oscillator with a degree of freedom or an isolated mode. of a more complex structure.
- the solution of the equation is simulated numerically at a degree of freedom (or isolated mode) at the excitation as defined by the equations defining the chosen base model.
- the simulation is done by numerically solving the differential equation of the oscillator with a damped degree of freedom subjected to a transient excitation.
- the identification of the real transient phase profile to a reference transient phase profile is by a least squares method by exploring the entire database.
- the identification of the real transient phase profile to a reference transient phase profile is done by a gradient method by generating the reference transient phase profiles on the fly.
- the method comprises a step in which:
- the basic model is a harmonic oscillator model with one degree of freedom (that is to say one seeks to identify a vibration mode or a system with a degree of freedom)
- these parameters are :
- the method comprises steps in which:
- FIG. 1 is a flowchart of the steps of an exemplary implementation of the method according to the invention. Detailed description of an embodiment of the invention
- the method is implemented using an acceleration sensor. Such a sensor is known per se, and is therefore not detailed further here. Alternatively, the method uses a speed or displacement sensor.
- This acceleration sensor transmits data at regular intervals to a computing device in the form of a measurement signal transmitted through a network known per se.
- the signal is acquired according to a sampling frequency at least twice that of the frequency of interest (Shannon rule).
- the measurement signal contains acceleration values. It can also contain values in time. If it does not contain time values, the sampling frequency must be known.
- This computing device is, in the present example in no way limiting, PC-type microcomputer. It has conventional user interfaces, as well as data storage means.
- the method for measuring dynamic properties comprises, firstly, in the present example, which is in no way limitative, after a preliminary step 50 of reception by the computing device of a measurement signal emitted by the sensor acceleration, a phase 100 of conditioning the measurement signal.
- This phase 100 of conditioning the measurement signal comprises several steps:
- Step 1 In the case where the excitation frequency, called the frequency of interest, around which we want to measure modal parameters of the structure is not known a priori, we realize a time-frequency map of the signal of measured. This operation can be performed in particular by calculating a sliding window Fourier transform, or by wavelet analysis. These two techniques are known per se.
- modal parameters that one wishes to identify for the structure are for example:
- Step 120 In a next step, areas of interest are identified in the time-frequency map. These are, in this example, the areas of maximum amplitude of the measurement signal. A frequency of interest is then defined as the frequency of an area of interest. Step 130 After determining a frequency of interest (previously known, or calculated in steps 1 10-120), the measurement signal is filtered around this frequency of interest.
- this filtering is performed to retain in the measurement signal, only the mode or the resonance around the frequency of interest.
- This filtering is done numerically. The simplest is to realize it in the frequency domain, that is to say by transform of fourrier, then by multiplication of the Fourier transform of the measurement signal by the Fourier transform of the filter to be applied, then by transform of Fourier inverse of the product. This example is a method among other digital filtering methods.
- the method of measuring dynamic properties here comprises a phase 200 for calculating the transient phase.
- This phase 200 for calculating the transient phase is subdivided into four stages.
- Step 210 the dominant frequency, denoted f, of the filtered measurement signal (output of step 130) is identified, generally by searching for a maximum of the Fourier transform of said filtered measurement signal.
- Step 220 In parallel, the local extremums of the filtered measurement signal (output of 130) are identified. This identification comprises a local extremum by half-oscillation of the filtered measurement signal. Step 230 Then, based on local extremums identified in step
- the phase of the filtered measurement signal which is pseudo-harmonic through the filtering step 130, is calculated by the following formula:
- Step 240 the difference between the phase of the filtered pseudo-harmonic measurement signal and the phase of a purely harmonic dummy signal which has the same frequency as the dominant frequency identified in step 210 is calculated. That is, subtracted from the phase calculated in step 230, 2 * ⁇ * f * time. This difference is called real transient phase profile.
- a third phase 300 of the method consists of an identification of the real transient phase profile.
- identification is meant the association of this real transient phase profile with a reference transient phase profile extracted from a previously generated database.
- Step 310 In a first step of this phase 300, responses of the structure whose modal parameters are to be determined are simulated to form a database of responses.
- a harmonic oscillator model with a degree of freedom that represents either an oscillator with one degree of freedom is an isolated mode of a more complex structure.
- This model makes it possible to generate reference curves (for example acceleration / time curves, speed / time, displacement / time or transient reference phase profile) used in the subsequent identification.
- the template can be written as follows:
- m is the mass (in the case of a system with one degree of freedom) or the modal mass (in the case of a more complex structure), the modal mass being defined as the partial mass of the structure associated with own mode considered, it is the damping (case with a degree of freedom) or the modal damping, k is the stiffness (case with a degree of freedom) or the modal stiffness,
- x is the position, x is the speed, x is the acceleration.
- x is the acceleration.
- a more complex model may be chosen, in particular with parameters of the model that vary over time.
- This step is performed independently of the measurement acquisition phase 50 and the measurement signal conditioning phase 100.
- the solution of the equation is simulated numerically at one degree of freedom (or isolated mode) at the excitation as defined by the three equations above.
- This simulation is done by a numerical resolution of the differential equation of the oscillator with a damped degree of freedom subjected to a transient excitation. This is for example carried out using a commercial digital calculation software. The number of responses to be simulated depends on the accuracy of the desired identification.
- Step 320 In the transient phase profile database thus created, a transient profile closest to that identified in step 240 ("real" transient phase profile) is identified according to a determined distance criterion.
- This identification can be done in different ways: least squares method by exploring the whole database, gradient method by generating transient phase profiles on the fly, genetic search algorithm, learning, etc. These different methods are known to those skilled in the art and are therefore not detailed further here.
- Step 330 This transient phase profile, identified as being closest to the transient phase profile of the measurement signal, is completely defined by a set of parameters, which are combinations of modal parameters to be identified and parameters of the excitation.
- the excitation frequency is actually the frequency of interest. It should be noted that the words pulsation and frequency are used interchangeably in the present description, even if there is a difference of 2 ⁇ between the 2.
- a fourth phase 400 of the method consists of an extension of the measurement. This phase, not always necessary according to the applications, has two stages.
- Step 420 With the data obtained in step 410, it is possible to simulate a response of the measured structure or mode with arbitrary amplitude excitation.
- modal mass by adjusting the amplitude of the arbitrary excitation so that the response of the simulated system is of the same amplitude as the signal studied.
- the adjustment is simply proportional between the output amplitude and the amplitude of the excitation.
- the aim is to measure the modal parameters obtained in the steps 320, 330, 410 and / or 420. These parameters are then compared to a specification, and according to the conformity or not In that specification, design changes are made to the structure or manufacturing process of the design.
- the goal is to follow the evolution of the parameters measured in steps 320, 330 and / or 410 (very rarely in step 420). We repeat the process several times and we follow the evolution of the measured parameters.
- the evolution of the parameters over time is then analyzed according to one or more criteria, so as to detect, for example, a passage of a parameter under a predetermined threshold, or a progressive drift of a slope greater than a predetermined slope. Such events then lead to further verification of the structure or maintenance action.
- This process allows, from the recordings of displacements, velocities or accelerations of a structure, to obtain a measurement of the properties of the structure (eigenfrequencies, modal damping, modal forms) as well as a measurement of the excitation that it has undergone (frequency of the excitation, amplitude and transitory character).
- the monitoring of structures (civil engineering, aeronautics, energy, railway) over time by a regular measurement of the properties of the structure thanks to the invention.
- the method then makes it possible to monitor the health of the structure, its compliance with standards of mechanical strength, and where appropriate to identify a degradation of the structure (or a modification of the properties of the structure).
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Aviation & Aerospace Engineering (AREA)
- Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)
Abstract
Description
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Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR1158151 | 2011-09-13 | ||
FR1158151A FR2980010B1 (fr) | 2011-09-13 | 2011-09-13 | Procede de mesure des proprietes dynamiques d'une structure mecanique |
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WO2013037880A1 true WO2013037880A1 (fr) | 2013-03-21 |
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PCT/EP2012/067930 WO2013037880A1 (fr) | 2011-09-13 | 2012-09-13 | Procédé de mesure des propriétés dynamiques d'une structure mécanique |
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FR (1) | FR2980010B1 (fr) |
WO (1) | WO2013037880A1 (fr) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US11660049B2 (en) | 2015-12-22 | 2023-05-30 | The University Of Sheffield | Apparatus and methods for determining force applied to the tip of a probe |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4164149A (en) * | 1978-05-09 | 1979-08-14 | Shigeo Okubo | Method and system for monitoring the angular deformation of structural elements |
WO1991019173A1 (fr) * | 1990-06-01 | 1991-12-12 | Technology Integration And Development Group Incorporated | Procede pour evaluer l'integrite structurale de structures composites |
US20080011091A1 (en) * | 2006-06-27 | 2008-01-17 | Abnaki Systems, Inc. | Method for measuring loading and temperature in structures and materials by measuring changes in natural frequencies |
US20110036180A1 (en) * | 2009-08-17 | 2011-02-17 | Fdh Engineering, Inc. | Method for Determining Tension in a Rod |
-
2011
- 2011-09-13 FR FR1158151A patent/FR2980010B1/fr active Active
-
2012
- 2012-09-13 WO PCT/EP2012/067930 patent/WO2013037880A1/fr active Application Filing
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4164149A (en) * | 1978-05-09 | 1979-08-14 | Shigeo Okubo | Method and system for monitoring the angular deformation of structural elements |
WO1991019173A1 (fr) * | 1990-06-01 | 1991-12-12 | Technology Integration And Development Group Incorporated | Procede pour evaluer l'integrite structurale de structures composites |
US20080011091A1 (en) * | 2006-06-27 | 2008-01-17 | Abnaki Systems, Inc. | Method for measuring loading and temperature in structures and materials by measuring changes in natural frequencies |
US20110036180A1 (en) * | 2009-08-17 | 2011-02-17 | Fdh Engineering, Inc. | Method for Determining Tension in a Rod |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US11660049B2 (en) | 2015-12-22 | 2023-05-30 | The University Of Sheffield | Apparatus and methods for determining force applied to the tip of a probe |
Also Published As
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FR2980010A1 (fr) | 2013-03-15 |
FR2980010B1 (fr) | 2013-11-22 |
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