WO2016023843A1 - Method of characterizing a system disposed in a medium allowing the propagation of a wave emitted by an object of said system - Google Patents

Method of characterizing a system disposed in a medium allowing the propagation of a wave emitted by an object of said system

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Publication number
WO2016023843A1
WO2016023843A1 PCT/EP2015/068309 EP2015068309W WO2016023843A1 WO 2016023843 A1 WO2016023843 A1 WO 2016023843A1 EP 2015068309 W EP2015068309 W EP 2015068309W WO 2016023843 A1 WO2016023843 A1 WO 2016023843A1
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objects
object
wave
recorded
signal
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PCT/EP2015/068309
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French (fr)
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Mikaël Carmona
Jean-Louis Lacoume
Olivier Michel
Rémy Vincent
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Commissariat A L'energie Atomique Et Aux Energies Alternatives
Institut Polytechnique De Grenoble
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/14Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object using acoustic emission techniques

Abstract

The method of characterizing a system disposed in a medium (1), said system (100) comprising at least one first object (101) able to emit a wave to be propagated in the medium (1), and a plurality of second objects (102) each able to record, at the level of said second object (102), a signal representative of the propagation of the wave emitted in the medium (1), comprises: - a step of emission (E1) of the wave in the medium (1) by said at least one first object (101), and - a step of location (E2) of said second objects (102) and of said at least one first object (101) using signals recorded by said second objects (102), said recorded signals each being representative of the propagation of the same emitted wave.

Description

A method of characterizing a system arranged in a medium allowing the propagation of a wave emitted by an object of said system Technical field of the invention

The invention relates to the field of object detection. The concept of detection is in the broad sense, it allows specifically locate objects.

The invention more particularly relates to a method for characterizing a system arranged in a medium.

State of the art

In the field of detection of objects, it has already been used techniques using acoustic signals propagating in a liquid.

The document "Using Ocean Ambient Noise for Array Self-Localization and Self-Synchronization" Karim Sabra G. et al. derived from IEEE Journal of Oceanic Engineering, Vol. 30, No. 2, April 2005 describes how to evaluate flight time from the elements located at the bottom of the ocean. However, such a study is very long (several recordings recorded signals continuously for 2.5 weeks) and focuses only the location of the signal sensor elements.

It follows a need to develop a more complete characterization process and allowing in particular to accelerate the characterization. The invention

The purpose of the present invention is to provide a solution which overcomes all or part of the disadvantages listed above.

Tends towards this goal through a method for characterizing a system arranged in an environment, said system comprising at least a first object able to emit a wave propagating in the medium, and a plurality of second objects each capable of recording, at said second object, a signal representative of the propagation of the transmitted wave in the medium, said method comprising:

- a wave transmitting step in the medium by the at least one first object, and - a step of locating said second object and said at least one first object using signals stored by said second objects, said signals being recorded each representative of the propagation of the transmitted wave.

Advantageously, the locating step comprises the following steps: - recording by each of the second objects of a corresponding signal representative of the propagation of the transmitted wave, each of the recorded signals including at least one resulting coda of the spread wave emitted in the medium, - an estimate of the position of said second objects using Endings signals recorded by said second objects,

- an estimate of the positioning of said at least one first object from at least two of the recorded signals.

In addition, the method may comprise a step of forming at least a pair of second items or a plurality of pairs of second objects, so that each second object belongs to at least one pair, and step estimating positioning said second objects may comprise, for each pair, a step of determining the distance separating the two objects of said second couple using Endings signals recorded by said two second objects of said couple.

According to one embodiment, the distance determination step separating the two second objects in the same pair comprises the following steps:

- extracting a first coda from the signal recorded by one of said two objects of said second pair,

- an extraction of a second coda from the signal recorded by the other of said two objects of said second pair,

- correlating the first and second coda, a use of said correlation to determine the distance between said two second objects of the same couple.

According to an improvement, the step of using said correlation comprises the following steps: - applying a third derivative in said correlation,

- using the result of said third derivative for determining the distance of separation between said two second objects of the same pair.

Advantageously, the step of using the result of said third derivative is to isolate a maximum argument based on the result of said third derivative, in particular from an application of a Ward identity to said result of said third derivative, this argument maximum being equal to the distance between said two second objects of the same torque divided by the wave propagation velocity emitted in the medium.

For example, the separation distances of the second objects of each pair being determined, the step of estimating the positioning of said second objects using each of said separation distances determined for estimating said positioning. Advantageously, the method comprises an initialization step wherein two second calibration objects are arranged in the middle so that the distance between them is known, and it includes a step of determining the speed of propagation of the transmitted wave in the medium using the result of the third derivative associated with said two second calibration objects so as to isolate the maximum argument according to said result of said third derivative, the propagation speed to be determined being equal to the known distance between said two second divided objects stallions by said maximum point.

Preferably, the step of forming the plurality of pairs is such that it results in the formation of C% distinct pairs with n the number of second objects in the plurality of second objects.

The step of positioning said at least one first object may comprise determining at least one representative of a hyperboloid surface in which said at least one first object is located from said at least two of the recorded signals.

In particular, the method may comprise, for each recorded signal, a step of processing said signal recorded simultaneously for extracting on the one hand the coda, and secondly a signal portion devoid of the coda, so that coda extracted participates in estimating the position of the second objects and said signal portion devoid of the coda participates in estimating the position of said at least one first object. The step of transmitting (E1) by said at least a first subject of the wave in the medium may be such that the transmitted wave is an acoustic or seismic wave.

The invention also relates to a system intended to be arranged in an environment, said system comprising at least a first object configured to emit a wave, and a plurality of second objects configured to record, in their level, a signal representative of the propagation of the transmitted wave in the medium. This system further comprises a module configured so as to locate said second object and said at least one first object using signals recorded by said second objects, said recorded signal being representative of each of the wave emitted by said at least one first object .

Brief description of drawings

Other advantages and features will become more apparent from the following description of specific embodiments of the invention given as non-limiting examples and shown in the accompanying drawings, wherein:

- Figure 1 schematically illustrates a system to characterize placed in a medium,

- Figure 2 schematically shows steps of a characterization process according to a particular embodiment of the invention,

- Figure 3 illustrates various components of a wave propagating in a medium,

- Figure 4 shows two superposed time signals, the first signal, the upper one, represents the amplitude of the signal recorded in volts versus time, and the second signal, the bottom, represents the translation of the above signal instant power in dB versus time,

- Figure 5 is a particular example of a signal representative of the propagation of the wave emitted and recorded by a second object, - Figure 6 shows a particular use of the result of the third derivative of the correlation of two signals recorded by two second separate objects, one can see by the variation of the normalized amplitude versus time.

Description of preferred embodiments of the invention

The method described below differs from the prior art in that it proposes to use a same wavelength, in particular after an impulse source for determining the sensor position and the position of an emission source said same wave.

In particular, as illustrated in Figure 1, the method allows to characterize a system 100 arranged in a middle one. The medium 1 is such that it allows the propagation of a wave, in particular an acoustic or seismic wave (or more generally mechanical). The medium 1 can be linear, homogeneous, dissipative, solid, fluid or weakly heterogeneous. The wave propagating in the medium 1 is characterized by a propagation speed in the said medium 1.

The system 100 comprises at least a first object 101 capable of emitting a wave propagating in the medium 1. The first object is also called source. In addition, system 100 includes a plurality of second objects 102 each capable of recording, at said second object 102, a signal representative of the propagation of the transmitted wave in the medium 1. This signal representative of the propagation of the wave may for example be a measure of the amplitude of a pressure field at the measuring point of an acoustic propagation medium. Every second object 1 02 is also referred to sensor. The signal recorded by each second object 1 02 corresponds to the propagation of the wave emitted by said first object and said second object view. The second objects January 02 are disposed at separate locations from each other so as not to record the same. Furthermore, for a source location (that is to say, the first object) in a space of n dimension (s) it will be n + 1 second non-coplanar objects.

The second the objects 1 02 can each be vector sensors (e.g., a triaxial accelerometer for measuring seismic waves), in this case the orientation of the different second objects 102 is different.

The characterization method comprises, as illustrated in Figure 1, a transmitting step E1 of the wave in the medium 1 by the at least one first object 1 01 and a locating step E2 of said second objects 1 02 and said at least one first object 1 01 using signals stored by said second products 1 02 said recorded signals each being representative of the propagation of the transmitted wave.

It is therefore understood that from a single transmitted wave, one can determine / estimate the position of "preference relative or absolute" second objects January 02 then the position of said at least one first object 1 01 On respect to said second objects 102. "relative position" means that the positions of the second object and the first object are known from each other without a fixed reference (eg terrestrial reference) is known. By "absolute position" is meant that the location is used to position the second object and the first object in a predetermined reference frame (e.g., ground reference). Preferably, there is a causal link between the location of the second objects and the first object. In this sense, it is preferable that the location of the first object does so only when a condition is verified. This condition can, for example, correspond to a validation that all second objects were located. This condition may be related to the fact that if we place ourselves in an absolute coordinate system (ie not on the sensor network) so we can not determine the position of a source without having previously determined the position of the sensors.

Preferably, this wave is emitted by a pulsed source (in time) and punctual (space - means point whose dimensions are negligible compared to those of the medium), that is to say, it is of very limited short over time, preferably in the range of a few milliseconds. In fact, the time depends on the acquisition rate (that is to say, recording) of the second objects. For example, for an acquisition frequency of 44.1 kHz, the pulse should preferably have a bandwidth of 44.1 / 2 kHz therefore a duration of at most 45 με.

A pulse wave may, for example, be a clapping the impact of an object on the floor, etc. It follows from the use of the same wave emitted a characterization of speed, especially in consuming very little power source. The process of characterization can therefore easily be picked up, particularly in the context of second and first autonomous objects. The step of transmitting E1 by said at least one first object 101 of the wave in the medium 1 is such that the transmitted wave, in particular pulse may be a seismic wave (or more generally a mechanical wave), or an acoustic wave.

In the case where the medium is solid and homogeneous, the transmitted wave is preferably seismic and one is interested in primary or secondary waves.

If the medium is weakly heterogeneous, the process described in this description is still valid but will be less accurate. The concept of "slightly heterogeneous" can be specified by considering the propagation velocity v in the medium that normally depends on the space v (x) where x path space. Weakly heterogeneous is formalized by v (x) ~ v for all x in space.

According to a particular embodiment, the E2 locating step comprises the following steps:

- a recording E2-1 by each of the second objects 102 of a corresponding signal representative of the propagation of the transmitted wave, each of the recorded signals including at least one resulting coda of the propagation of the transmitted wave in the medium 1,

- an estimate of E2-2 positioning said second objects 102 using Endings signals recorded by said second object 102, an estimate E2-3 positioning said at least one first object from at least two of the recorded signals, of each preferably free of its coda. Each second object 102 may continuously record, in this case an upstream phase will detect the presence of the desired signal to extract the recording. In fact, the wave propagates between a first source point (here the first object 101) and each sensor mark (here one of the second objects 102). When at a first point pulse is emitted (e.g. an acoustic wave), the wave will propagate in the medium 1. The emitted wave will reflect off the walls and spread via the heterogeneities. As illustrated in Figure 3, the propagation seen by the second point may result in a signal comprising three components. The first component td represents the time of flight between the two points, the second component tp rec represents the early reflections of the wave in the medium, and the third component tdift represents a phase where all the instants of arrival is no longer separable . The coda is this third component tdi f t. Note the existence of a fourth component corresponding to the return to ambient noise and not shown in Figure 2. It is understood that the result of step using said coda a need to extract the coda of a recorded signal if we want later limited computational resources. The extraction of a coda can be done as illustrated in Figure 4 from the power thresholds based on the recorded signal. In Figure 4, the upper graph represents the signal amplitude in volts versus time as recorded, and the lower graph represents the amplitude of the same signal in terms of instantaneous power (dB) versus time. The instantaneous power of said recorded signal has a maximum instantaneous power Pmax at a determined instant after this instant TDET determined TDET the instantaneous power will gradually decrease, then one chooses to isolate a first time ti associated with said recorded signal whose instantaneous power is preferably substantially equal to 2/3 of the maximum instantaneous power and a second time t2 associated with said recorded signal whose instantaneous power is preferably equal to substantially 1/3 of the maximum instantaneous power. The times t1 and t2 are after the given time described above. Then just resume signal as recorded and to extract the signal portion between t1 and t2, which corresponds to the coda.

Although the method using the powers to extract a coda of a signal has been described, the skilled person may use any other method. According to an improvement, the method comprises a step of forming at least one pair of second objects 102, or a plurality of pairs of second objects 102, such that each second object 102 belongs to at least one pair. The E2-2 estimating step of positioning said second object 102 includes, for each pair, a distance determining step of separating the two second objects 102 using said torque Endings signals recorded by said two second objects 102 of said pair .

We now understand that when we know the distances between each pair of second objects, one is able to easily navigate to a relative positioning of the second object 102 to each other. Preferably, if it has already located second objects (called anchors or tags) in a predetermined mark, then we can locate the second objects 102 in absolute I said predetermined mark which is the tags. More particularly, the step of determining the distance separating the two second objects 102 in the same pair may comprise a step of extracting a first coda Sa from the signal recorded by one of said two of said second objects 102 torque, and a step of extracting a second coda Sb from the signal recorded by the other of said two second objects 102 of said couple. 5 illustrates the amplitude of the signal recorded by one of the second objects over time. Using the method of power described above, it will look for values ti and t 2 to be applied to the two recorded signals associated with said couple. One can then apply the method of the powers on one of the saved and the instants t1 and t2 signals determined from this recorded signal are applied to both signals recorded torque. Alternatively, the method is applied powers on the two signals recorded and t1 and t2 correspond to selected terminals of a time range covering a first range defined by t1 and t2 associated with one of the recorded signals and a second range defined by t1 and t2 associated with the other of the recorded signals. After extracted the first and second coda Sa, Sb, it is implemented a step of correlating the first and second coda, in particular by using the following formula:

Figure imgf000015_0001

With Ca, b () the result of the correlation. It is therefore understandable interest in the extraction of codas to limit calculations when the correlation.

Generally, the calculations in the context of the present invention were used to validate that the odd part of the impulse response between two second objects 102 of a torque was proportional to the third derivative of the result of the correlation. Specifically, the theory experimentally verified shows that we find the odd part of IR - Impulse response - (defined by IMP_RI (t) = 1/2 * (RI (t) - R (t)) and not IR itself. for a causal RI (ie zero at negative time) can easily be retrieved RI from its odd part. in another case (rare), the odd part of IR is not enough to rebuild IR.

Thus, the distance determination step separating the two second objects 102 in the same pair may comprise use of said correlation to determine said distance, in particular the use comprises a step of applying a third derivative in said correlation , followed by a use of the result of said derived third step for determining the distance of separation between said two second objects 102 of the same pair. 6 illustrates a signal depending on the result of the correlation of two recorded signals. The maximum argument of Figure 6 signal is preferably equal to the distance separating the two second objects 102 of the torque divided by the wave propagation velocity emitted in the medium. If the medium is known, then the propagation speed is and therefore it is easy to trace the value of the distance between the two second objects of the same couple. In other words, the use of the result of said derived third step consists of isolating a maximum argument based on the result of said third derivative, in particular from an application of a Ward identity to said result of said third derivative, this maximum argument being equal to the distance between said two second objects of the same torque divided by the wave propagation velocity emitted in the medium. In particular, from the result of the third derivative, there is provided a reconstruction of the impulse response between the two second objects 102 of said torque, in particular using a Ward identity, and the maximum point is determined from said reconstruction . The identity of Ward was given by way of example, the skilled person can also use the wheel with a maximum on the flight time.

The use of the third derivative is a preferred example. In this sense, it is possible to use any estimator, applied to the correlation to estimate the flight time. More generally, it is then understood that the method may comprise use of said correlation to determine the distance between said two second objects 102 of the same pair, and the use of correlation can be used the third derivative.

It will be understood from what has been said above that it is desired to determine the distance between two second objects 102 preferably using the impulse response between said two second objects 102, typically, this response can be written:

Figure imgf000017_0001
where 0 indicates a proportionality relation, the invention does not in fact need the amplitude factor δ to the distribution indicating a pure delay equal to d {A, B) I i where d {A, B) is the Euclidean distance between points a and B (the two second objects 102 in the same pair, respectively). R function is zero for times less than d {A, B) I v. It is often representative of reflections on the obstacles and the interfaces of the propagation medium.

Equation (1) may be an approximation, the necessary condition is that the maximum argument of h (A, B, t) is located in d {A, B) I v.

Therefore, the method for which the impulse response satisfies (1) makes it possible, in known propagation speed or estimated to determine the distance d (A, B) forming the product between the maximum argument of h (A, B, t) and v.

Once the distance of separation of second objects 102 of each pair are determined, the positioning of the estimating step E2-2 said second objects 102 uses each of said separation distances determined for estimating said position of said second objects. Positioning is on if no absolute position of the second object 102 is known. If some second objects 102 have a known position relative to a fixed reference (e.g., ground reference) then it is possible to estimate the position of other second objects 102 in the same defined reference.

In the present specification, for each pair of second objects, the separation distance determined between said two second objects said pair is preferably a Euclidean distance. Those skilled in the art will know perfectly from separation distances, up to the estimated position of each of the second objects of the system. This point will therefore not be described in detail.

We used above in the particular case where the wave propagation speed is emitted in the environment known. If it does not, it will have to determine. In this case, the method comprises an initialization step wherein two second calibration objects (belonging to the plurality of second objects defined above) are disposed in the middle so that the distance between them is known. Accordingly, the method comprises a step of determining the wave propagation speed sent into the medium using the result of the third derivative associated with said two second calibration objects so as to isolate the maximum argument according to said result of said derivative third (in particular from an impulse response between said two second calibration objects reconstructed from said result of said third derivative), the propagation velocity to be determined being equal to the known distance between said two second calibration objects divided by said maximum argument . Then, the propagation speed has been determined, the separation distance associated with each pair of second non-standard objects may be used as described above to estimate the distance of separation between said second objects of each pair of second non standard items.

According to a refinement, the plurality of the pairs forming step is such that it results in the formation of C% distinct pairs with n the number of second objects 102 contained in the plurality of second objects 1 02. With such an assembly torques, it is possible to ensure proper positioning of each of the second objects 1 02. above was treated the step of estimating the position of each of the second objects, turn now to the step of estimating of E2-3 positioning said at least one first object 101. This last step E2-3 comprises determining at least one representative of a hyperboloid surface in which said at least one first object

101 is located from said at least two of the recorded signals. The use of a hyperboloid used to determine the positioning of said at least one first object 101 in a particular area. To that effect, to refine the positioning of said at least a first object to a local precise position, one will look to the data (the recorded signals) of a plurality of second objects couples

102 so as to generate a plurality of hyperboloids localization. The intersection of the hyperboloids of the plurality of hyperboloids then allows a precise location of said at least one first object 101. More particularly, for estimating the position of said at least a first object 101, we will try to estimate the difference of the wave arrival time emitted from said at least one first object 101 between each pair of second objects 102 System listening to the first object. This estimated difference in arrival time is established mainly by calculating the maximum argument of the cross-correlation of the signals recorded by the second objects 102 in the same pair. This method is the most used, but there are other methods to estimate the flight time difference. These differences in time of arrival differences are converted into distance through multiplication by v assumed known propagation speed. For a couple of second objects 102, the difference in distances (Euclidean) specify on which is located the first hyperboloid corresponding object. Merging all the differences in distances can be traced back to the absolute position of said at least one first object, relative to the coordinate system in which the positions of the second objects 102 are known.

To determine the position of the at least one first object from hyperboloid (s), the skilled person can, besides what has been said above, use the teachings of "A Simple and Efficient Estimator for Hyperbolic Rental "YT Chan et al published in IEEE Transactions on signal processing, vol. 42, NO. 8 August 1994.

It is understood from what has been said above that the method may include, for each recorded signal, a step of processing said signal recorded simultaneously for extracting on the one hand the coda, and secondly a portion of signal devoid of the coda, so that the coda extracted (preferably only the extracted coda) participates in estimating the position of second objects 102 and said signal portion devoid of the coda (preferably only said signal portion devoid of the coda ) participates in estimating the position of said at least one first object 101.

This treatment step intended to limit the size of the signal components to be analyzed to estimate the one hand the positioning of each of the second objects 102 and secondly each first object 101. Indeed, it is to remove parts of the signal that are not useful to limit the operations thereafter.

The location by hyperboloid from signals recorded by a pair of second objects 102 generally implements a correlating step of the two recorded signals of the same pair. In this sense, given that the coda contributes nothing to the determination of the position of the first object, using only the parts of the recorded upstream coda signals limit the calculation time due to the correlation.

This can be quantified in the worst case. The location of the first object is achieved by using the time of flight difference between the useful signals correlated. Correlation between two signals of N points costs about N * log (N) operations. Therefore, if there is N the total number of samples of the signal and the number of samples N∞da coda then the number of samples of the useful signal and the reduction factor of the computing time is: J _ NN cod .a lo o * (> NN cod, a)

N log (N)

If the correlated signal is sampled at 44.1 kHz. There are N 1 = 10250 and N - Ncoda = 22050, the computation time then has a reduction factor G of about 17%.

It has been mentioned several times calculations or processing performed on the recorded signals. For example, each second object 102 transmits the registered signal and a unique identifier within the system to an external master unit that will process said signals recorded in the manner as described herein for estimating the position of second objects 102 and 101 of each first object. It follows from this example that the system comprises the master unit and a communication system for exchanging data (recorded signal and ID) between each second object 102 and the master unit.

Alternatively the master unit described above may be the first object 101 or one of the second objects 102. According to a particular implementation, each pair of second objects 102 is configured such that one of the two objects torque receiving data from the other object of said pair so as to determine itself the separation distance between said two objects of said second torque.

We now understand that the skilled person, depending on the resources available will encourage where are carried out the various stages of the process.

The invention also relates to a system 100 to be disposed in a medium 1, said system comprising at least a first object 101 configured to emit a wave, and a plurality of second objects 102 configured to register, each at their level, a signal representative of the propagation of the transmitted wave in the medium 1. The system further comprises a module configured so as to locate said second objects 102 and said at least one first object 101 using signals recorded by said second objects 102, said recorded signal being representative of each of the wave emitted by said at least a first object.

Generally, it will be understood that the present invention is to use the same signal (the same wave) emitted by at least one first object, preferably forming an impulse source in a propagation medium for which the traveling wave is composed of a coda.

In a first example, two second objects 102 and a first object 101 are arranged in a variety of dimension 1 of known kind (for example a straight line). In this case, it is possible to trace a precise positioning of the first and second objects 101, 102 from only two signals recorded by said second object 102. In a second example, the second objects 102 are arranged in a curved variety. Therefore, the separation distances determined are no longer Euclidean but geodetic. In this case we can have:

- three second objects 102 not aligned if the latter and the first object 101 are a variety of known dimension 2 (a plane for example),

- four non-coplanar second objects 102 if the second objects 102 and the first object 101 are placed in a three-dimensional space.

The process of characterization can run on any variety in which an impulse source creates a coda and this variety is a linear propagation medium. The case of a three-dimensional environment is an example of planar Euclidean variety. The case of a three-dimensional sphere is an example of 2D variety. Formally, this process can be operated when the geometry of the variety is known (3D space, sphere, cylinder, etc.). More formally, knowing the geometry is to know the Riemannian metric associated with this variety.

Generally applicable to all that has been said above, a second object 102 may comprise all or some of the following:

- an on-board intelligence (e.g., a microcontroller),

- a diet,

- passive components, an electronic management and power conditioning elements of said second object,

a communication module (for a wireless node, for example),

a packaging to facilitate integration in the environment and withstand the associated constraints,

a sensitive measuring element (e.g., a sensor) to the wave emitted by the or the first such pulse source objects (e.g., a particular microphone type OMNI PRO SIGNAL to an emitted acoustic wave, or for example an accelerometer to a transmitted seismic wave).

The process of characterization described above can be used in the context of monitoring of structures on the one hand, abnormalities that generate pulsed sources: water leakage in industrial plumbing, falling objects, rupture a cable, etc. and, secondly, structures whose geometry is scalable (bridge wire, beam, plate of an aircraft wing, etc.). In this context, it is both necessary to relocate the network (second objects), in particular over time, and locate the abnormality (treated as the first item).

Once located the network (the second objects located) allows the location of the source (first object), but also capture the context: temperature, pressure and in the detection part of a rupture for example this method detects and locates the source but also clarifies what the state of the environment when it happened.

Claims

1. A method of characterizing a system disposed in a medium (1), said system (100) comprising at least a first object (101) capable of emitting a wave propagating in the medium (1), and a plurality of second objects ( 102) each capable of recording, at said second object (102), a signal representative of the propagation of the transmitted wave in the medium (1), said method comprising: - a transmission step (E1) of the wave in the medium (1) by said at least one first item (101), and
- a locating step (E2) of said second object (102) and said at least one first object (101) using signals stored by said second object (102), said recorded signal being representative of each of the propagation of the transmitted wave .
2. Method according to the preceding claim, characterized in that the locating step (E2) comprises the following steps:
- a recording (E2-1) by each of the second objects (102) of a corresponding signal representative of the propagation of the transmitted wave, each of the recorded signals including at least one resulting coda of the propagation of the transmitted wave in the medium (1), - an estimate (E2-2) positioning said second object (102) using the coda signals recorded by said second object (102);
- an estimate (E2-3) positioning said at least one first object (101) from at least two of the recorded signals.
3. Method according to the preceding claim, characterized in that it comprises at least a step of forming a pair of second items (102), or a plurality of pairs of second objects (102), such that each second item (102) belongs to at least one pair, and in that the positioning estimation step (E2-2) of said second object (102) comprises, for each pair, a step of determining the distance between the two second objects using said torque Endings signals recorded by said two second objects (102) of said pair.
4. Method according to the preceding claim, characterized in that the step of determining the distance separating the two second objects (102) in the same pair comprises the following steps:
- extracting a first coda from the signal recorded by one of said two objects of said second pair,
- an extraction of a second coda from the signal recorded by the other of said two second objects (102) of said pair, a correlation of the first and second coda, a use of said correlation to determine the distance between said two second objects ( 102) of the same pair.
5. Method according to the preceding claim, characterized in that the step of using said correlation comprises the following steps: - applying a third derivative in said correlation,
- using the result of said third derivative to determine the separation distance between said two second objects (102) of the same pair.
6. Method according to the preceding claim, characterized in that the step of using the result of said third derivative is to isolate a maximum argument based on the result of said third derivative, in particular from an application to an identity of Ward said result of said third derivative, the maximum point being equal to the distance between said two second objects (102) of the torque divided by the wave propagation velocity emitted in the medium.
7. A method according to one of claims 3, 4, 5 or 6, characterized in that the distances of separation of second objects (102) of each pair being determined, the positioning of estimating step (E2-2) said second objects (102) uses each of said separation distances determined for estimating said positioning.
8. Method according to one of Claims 6 or 7, characterized in that it comprises an initialization step wherein two second calibration objects are arranged in the middle so that the distance between them is known, and in that it comprises a step for determining the wave propagation speed sent into the medium using the result of the third derivative associated with said two second calibration objects so as to isolate the maximum argument according to said result of said third derivative, the propagation speed to be determined being equal to the known distance between said two second calibration objects divided by said maximum point.
9. A method according to any one of claims 3 to 8, characterized in that the plurality of pairs forming step is such that it results in the formation of C% distinct pairs with n the number of second objects ( 1 02) contained in the plurality of second objects (1 02).
1 0. A process according to any one of claims 2 to 9, characterized in that said positioning step (E2-3) of said at least one first object (1 01) comprises determining at least one representative of hyperboloid a surface wherein said at least one first object (1 01) is located from said at least two of the recorded signals.
January 1. Method according to one of claims 2-1 characterized in 0 that it comprises, for each recorded signal, a step of processing said signal recorded simultaneously for extracting on the one hand the coda, and secondly a part signal devoid of the coda, so that the coda extracted participates in estimating the position of the second object (102) and that said portion of lacking the coda signal participates in estimating the position of said at least one first object.
12. A method according to any one of the preceding claims, characterized in that the step of transmitting (E1) by said at least a first subject of the wave in the medium is such that the transmitted wave is a seismic wave or acoustic.
13. The system (100) to be disposed in a medium (1), said system (100) comprising at least a first object (101) configured to emit a wave, and a plurality of second objects (102) configured so as to record, at their respective levels, a signal representative of the propagation of the transmitted wave in the medium (1), characterized in that it comprises a module configured to locate said second objects (102) and said at least one first object (101) using signals recorded by said second object (102), said recorded signal being representative each of the wave emitted by said at least one first item (101).
PCT/EP2015/068309 2014-08-11 2015-08-07 Method of characterizing a system disposed in a medium allowing the propagation of a wave emitted by an object of said system WO2016023843A1 (en)

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