FR3103572A1 - PROCESS FOR SURVEILLANCE OF A MARITIME ZONE - Google Patents

Abstract

The invention relates to a method for monitoring a maritime area comprising a cycle of the following successive steps: - acquiring (100) acoustic measurements by means of a set of acoustic reception antennas, the reception antennas of the all being each in a reception configuration, - detecting (200) a set of noisemaker of interest by forming sonar channels from the acoustic measurements, each noisemaker of interest being characterized by a set of at least one primary characteristic comprising a noisemaker positioning zone defined in a global frame of reference common to all the noisemakers of interest, and, when the set of noisemakers of interest is not empty: - determine (300), from the set of d 'at least one primary characteristic, an optimum configuration set comprising an optimum reception configuration for each antenna of a subset of the reception antennas of the set of reception antennas, so that each antenna that the receiving antenna of the sub-assembly are capable of detecting, in the next cycle, acoustic signals originating from a noisemaker of interest of the set of noisemaker of interest, - reconfigure (400) each reception antenna of the sub- together according to the optimal reception configuration defined for this reception antenna, the cycle of processing steps being repeated at least once. Figure for the abstract: Fig 2.

Description

METHOD FOR MONITORING A MARITIME AREA

The invention lies in the field of sonars and more particularly of the surveillance of maritime areas. It relates, more particularly, to systems for monitoring underwater areas. These monitoring systems include submerged acoustic receiving antennas.

These systems conventionally comprise a set of sonar devices, for example buoys drifting at sea, each comprising one of the acoustic reception antennas making it possible to acquire acoustic measurements and processing means configured to process the acoustic measurements in order to detect, and classify maritime area noisemakers. By noisemaker, we mean any underwater or surface sound source.

An object of the invention is to improve the detection and/or localization and/or classification performance of this type of system.

To this end, the subject of the invention is a method for monitoring a maritime area from a set of acoustic reception antennas, the acoustic reception antennas of the set each comprising several acoustic transducers, the antennas of reception being reconfigurable so as to be able to be in several reception configurations in which they are immersed, the method comprising a cycle of the following successive steps:
- acquiring acoustic measurements by means of the set of acoustic reception antennas, the reception antennas of the set each being in a reception configuration,
- detect a set of noise generators of interest by forming sonar channels from the acoustic measurements, each noise generator of interest being characterized by a set of at least one primary characteristic comprising a positioning zone of the noise generator defined in a common global reference frame to all noisemakers of interest,
and, when the set of noisemakers of interest includes at least one noisemaker of interest:
- determining from the set of at least one primary characteristic, a set of optimal configuration comprising an optimal reception configuration for each antenna of a subset of the reception antennas of the set of reception antennas, so that each reception antenna of the subset is capable of detecting, in the next cycle, acoustic signals coming from a noisemaker of interest of the set of noisemakers of interest,
- reconfiguring each acoustic reception antenna of the subset according to the optimal reception configuration defined for this reception antenna,
the cycle of processing steps being repeated at least once.

Advantageously, the determination step comprises the following steps:
- form sonar channels from acoustic measurements acquired by the set of acoustic reception antennas during the acquisition step,
- from the channels formed, detecting, according to a predetermined detection criterion, a set of local noisemakers, each local noisemaker of the set of local noisemakers being characterized by a set of at least one local noisemaker characteristic comprising a local noisemaker positioning zone in a reference frame linked to the reception antenna,
- merging local noisemakers in order to obtain a set of at least one noisemaker of interest, each noisemaker of interest being characterized by a set of noisemaker characteristics of interest comprising a positioning zone in a global reference frame common to all local noisemakers.

Advantageously, the cycle of steps includes a step for determining the kinetic characteristics of the set of at least noise generators of interest.

Advantageously, the cycle of steps comprises a step of classifying the set of at least one noisemaker of interest from the kinetic characteristics of the set of at least one noisemaker of interest and from the set at least one primary characteristic.

Advantageously, the cycle of steps comprises a step of estimating an evolution of the set of at least one noisemaker of interest in a following cycle from the set of at least one primary characteristic, of the characteristics kinetics and from the classification of the set of at least one noisemaker of interest.

Advantageously, the step of determining the set of optimal configuration comprises, when the set of at least one noisemakers of interest comprises several noisemakers of interest, a step of determining an order of priority of the noisemakers of interest, from the characteristics of the noisemakers of interest, and a step of determining the optimal configuration set from characteristics of the noisemakers of interest and from the order of priority.

Advantageously, a first antenna of the subassembly is linear and comprises an elongated body from a first end to a second end, the determination of the optimal configuration of the reception antenna of the first sonar device comprising the determination of an angle of the second end elevation and/or the determination of a second end azimuth in a reference frame connected to a negatively buoyant support connected to the first end of the first receiving antenna, the reconfiguration of the first receiving antenna comprising the adjustment of the elevation angle and/or the azimuth.

Advantageously, the determination of the set of optimal configuration comprises the determination of a relative positioning of the acoustic transducers of at least one second reception antenna of the subset, the reconfiguration comprising the adjustment of the relative positioning of the acoustic transducers of the second receiving antenna.

Advantageously, the determination of the optimal configuration comprises the determination of an immersion of a third antenna of the subassembly, the adjustment of the configuration of the third sonar device comprising the adjustment of the immersion of the antenna.

The invention also relates to a sonar system comprising:
- a set of acoustic reception antennas, the reception antennas each comprising several acoustic transducers, the reception antennas of the set being reconfigurable so as to be able to be in several reception configurations, the set of antennas being capable of acquiring acoustic measurements,
- adjustment means capable of reconfiguring the reception antennas according to the optimal configuration set,
- a processing device suitable for performing the steps of detecting and determining the optimal configuration set of the method according to the invention,
the sonar system being configured to implement the method according to the invention.

Advantageously, the sonar system comprises a set of sonar devices comprising a first sonar device comprising a support with negative buoyancy and a first acoustic reception antenna of the set of antennas, the first reception antenna being linear and comprising a body elongated from a first end to a second end, the elongated body being connected by the first end at a fixed connection point with respect to the support, the sonar device being able to be in a plurality of reception configurations in which the body of the the antenna and the support are completely submerged, the antenna body extending substantially vertically from the first end to the second end towards the seabed in at least one reception configuration, the first sonar device comprising adjustment means orientation making it possible to adjust, when the first sonar device is in the operational configuration and the support is fixed with respect to the terrestrial reference, a elevation angle and an azimuth of the second end in the reference frame linked to the support centered on the point of connection. The first acoustic reception antenna is one of the antennas of the set.

Advantageously, the system comprises means for adjusting the relative positioning of acoustic transducers of a second reception antenna of the set of antennas.

Advantageously, the system comprises a device for adjusting an immersion of a third reception antenna of the set of antennas.

Other characteristics and advantages of the invention will appear on reading the following detailed description, given by way of non-limiting example and with reference to the appended drawings in which:

FIG. 1 schematically represents a sonar system according to the invention,

FIG. 2 schematically represents the main steps of the monitoring method according to the invention,

FIG. 3 schematically represents in more detail the steps of the monitoring method according to the invention,

FIG. 4 schematically represents a conical surface obtained from channel formations from signals measured by a linear acoustic reception antenna,

FIG. 5 schematically represents a sonar device according to a first embodiment in two reception configurations,

FIG. 6 schematically represents part of the sonar device according to a second embodiment in a low vertical orientation, and two other reception configurations,

FIG. 7 schematically represents an example of a buoyancy modification device.

From one figure to another, the same elements are identified by the same references.

The invention relates to a method for monitoring a maritime area. The sonar system SYS according to the invention comprising a plurality of sonar devices. Each of the sonar devices includes a reconfigurable acoustic receiving antenna. The monitoring method according to the invention uses the possibility of reconfiguring the acoustic reception antennas to improve the monitoring performance of noise emitters located in the maritime area. It increases the spatial coverage area of the sonar system.

The invention applies in particular to the underwater surveillance of private or military installations, to the surveillance of maritime surface and underwater traffic, and to the study of the flow of underwater animals.

An example of a sonar system according to the invention is represented in FIG. 1. It comprises several sonar devices DS_k with k=1 to K where K is the number of sonar devices, K being greater than 1. The integer K is equal to 4 in the non-limiting embodiment of FIG. 1.

Each sonar device comprises an acoustic reception antenna A _k comprising several acoustic transducers TA _kj with j=1 to Nk where Nk is the number of acoustic transducers TA _kj of the acoustic reception antenna A _{k .} Nk is greater than 1. The antennas each comprise 3 transducers in the non-limiting example of FIG. 1.

By acoustic transducer TA _j is meant a transducer able to transform an acoustic wave into an acoustic measurement, that is to say to acquire an acoustic measurement. Acoustic measurement means a signal representative of an acoustic intensity and an acoustic frequency as a function of time over an acquisition period.

An acoustic transducer TA _j is, for example, an electro-acoustic transducer, for example a hydrophone, transforming an acoustic wave into an electrical signal representative of an intensity and a frequency of the acoustic wave detected by the transducer, in as a function of time over an acquisition period or else an opto-acoustic transducer, transforming an acoustic wave into an optical signal representative of an intensity and a frequency of the acoustic wave detected by the transducer, as a function of time over a vesting period/

Each sonar device comprises, for example, an acoustic reception antenna A_k, a floating main support F_{k ,} an LP dive line_k and a support S_k negative buoyancy. Antenna A_kis connected to the main floating support F_k (i.e. positive buoyancy) via the LP dive line_kconnecting support S_kto the main support F_k.

It should be noted that each sonar device comprises one or more acoustic reception antennas.

Each acoustic reception antenna Ak is capable of being in different acoustic signal reception configurations in which it is intended to acquire acoustic measurements. In other words, the acoustic reception antenna is reconfigurable. In these reception configurations, the acoustic reception antenna is totally immersed.

Each reception configuration of the antenna Ak is characterized by a set of at least one configuration parameter representative of a position of the antenna and/or of at least one configuration parameter representative of an orientation of the antenna and/or at least one configuration parameter representative of a reception characteristic of the antenna.

The set of at least one reception parameter comprises, for example, a parameter representative of an acoustic reception frequency of the antenna, such as, for example, a relative arrangement of the acoustic transducers of the antenna, such as for example a DI distance_kbetween the acoustic transducers TA_{K J}and your_kj+1 adjacent to antenna A_kand/or a minimum frequency from which the acoustic reception antenna is sensitive and/or a maximum frequency from which the acoustic reception antenna is insensitive and/or a reception threshold comprising, for example, an intensity minimum sound from which the acoustic reception antenna is sensitive and/or a processing characteristic linked to the processing chain of the antenna, such as for example a characteristic of a filter.

The set of at least one configuration parameter representative of a position of the antenna comprises, for example, an immersion corresponding to the depth of the reception antenna and/or a horizontal position of the reception antenna in a frame of reference common to all the receiving antennas, such as the terrestrial frame of reference, for example.

The set of at least one configuration parameter representative of an orientation of the reception antenna in a predetermined frame of reference comprises, for example, a elevation angle αa _k of a part of the antenna and/or an azimuth βa _k of the part of the antenna, these angles being defined in a predetermined frame of reference, for example a frame of reference linked to a support belonging to the sonar device DS _k .

In the case of several configuration parameters, the latter can be adjusted independently by configuration parameter adjustment means comprising elementary adjustment means REG _k .

These parameters are referenced, in FIG. 1, only for the antenna A ₁ for greater clarity, but it is clear that, in this figure, the antennas are represented in different reception configurations.

The adjustment means comprise elementary adjustment means REG _k distributed over the various sonar devices DS _k .

The sonar system according to the invention also comprises TRC processing and control means configured to:
- process acoustic measurements J_k with k = 1 to K acquired by the acoustic reception antennas, to monitor the maritime area and, in particular, to detect and locate noise emitters in the maritime area,
- generate OR reconfiguration orders_kintended for the adjustment means so that they reconfigure the antennas of the assembly by adjusting the parameters of the reception configurations of these antennas A_{k ,}
- and possibly, generate OA acquisition orders_kso that the acoustic receiving antennas A_kDS sonar devices_kacquire acoustic measurements.

The TRC processing and control means are, for example, remote, that is to say not included in the sonar devices. They are, for example, installed in a TER processing plant, located on land or on a seagoing vessel (“seagoing vessel” in Anglo-Saxon terminology) which may be a surface vessel (“surface ship” in Anglo-Saxon terminology) or a submarine, and are linked in communication, for example by satellite, with the sonar devices DS_k to be able to receive the acoustic measurements J_kand send OR setting commands_kand, possibly, OA acquisition orders_kDS sonar devices_k. As a variant, the processing means are, for example, distributed over sonar devices, that is to say mechanically connected to acoustic reception antennas of the sonar system.

The invention relates to a method for monitoring a maritime area from a sonar system according to the invention. The method according to the invention is implemented while the acoustic reception antennas are totally immersed and each, in a reception configuration of the reception antenna, defined by a set of reception characteristics.

Sonar devices are, for example, free in the water so that they drift under the effect of sea currents. This solution is light and has a certain discretion with respect to a threat due to the unpredictable nature of the positions of the sonar devices. As a variant, the receiving antennas are connected to a fixed support, for example to the seabed or to a sea vessel or to an adjustment device making it possible to adjust the relative positions of the receiving antennas in a horizontal plane substantially parallel to the surface of the vessel. water by calm sea state. This solution is more cumbersome and costly, but it does allow some control of the positions of the antennas and is suitable for monitoring port areas in which maritime traffic must not be disturbed.

Each receiving antenna is intended to cover a spatial coverage area. Acoustic noises generated by noisemakers in this spatial coverage area are likely to be measured by the acoustic antenna. The reception antennas are arranged so as to cover respective spatial coverage zones, at least some of which are capable of partially overlapping. Thus, acoustic reception antennas of the assembly, the spatial coverage areas of which partially overlap, are able to acquire acoustic measurements originating from the same noise emitters in the overlapping area of the spatial coverage areas, which makes it possible to obtain measurements complementary acoustics coming from the same noisemakers.

The steps of the method according to the invention are shown in Figure 2.

It includes a cycle of the following successive processing steps:
- in a first step 100, acquire acoustic measurements by the set of acoustic reception antennas A_kk = 1 to K, the antennas each being in a predetermined reception configuration,
- in a second step 200, detecting a number NB greater than or equal to 0 of noisemakers of interest B_b; each B_bis characterized by a set of noisemaker characteristics of interest comprising, in particular, a positioning zone PO_b of the noisemaker of interest B_bdefined in a global frame of reference common to all noisemakers of interest B_b, the noisemakers of interest B_bbeing detected, in particular, by forming sonar channels from the acoustic measurements J_k,
- in a third step 300, determining optimal reception configurations of a subset of reception antennas of the set of reception antennas from the characteristics of the NB noisemakers of interest Bb with b=1 to NB , NB being the number of noisemakers of interest detected, this step being implemented when the number NB of noisemakers of interest is non-zero,
- in a fourth step 400, reconfiguring the reception antennas of the subset of antennas so that the antennas of the subset acquire the acoustic measurements in these respective optimal reception configurations during the following cycle of steps.

The cycle of steps is repeated at least once. The repetition of the step cycle is stopped when a stop criterion is met. The stop criterion is, for example, a time criterion or a reception, by the processing and control means TRC, of a stop command. The stopping criterion is, for example, respected when the monitoring duration has reached a predetermined duration threshold.

Consequently, the method according to the invention uses the possibility of reconfiguring the reception antennas to optimize the reception configurations of a subset of reception antennas, so that each of the reconfigured antennas can obtain acoustic measurements from one of the noisemakers detected. This makes it possible to obtain, in the following cycle, from the measurements acquired during the following cycle, new characteristics of this noisemaker and/or to improve the accuracy of the characteristics of this noisemaker. The method according to the invention thus makes it possible to obtain better monitoring performance such as, for example, detection and/or location and/or classification and/or tracking performance of noise emitters than by using reception antennas of configuration fixed reception or whose variation is not controlled.

We will describe more precisely the method according to the invention with reference to Figure 3.

The acquisition step 100 consists in generating, by each antenna A_k of the set of acoustic receiving antennas, a set of acoustic measurements J_k, the acoustic receiving antenna A_kbeing in a predetermined receiving configuration. Each set of acoustic measurements J_k includes a number Nk greater than 1 of elementary acoustic measurements. Each elementary acoustic measurement is delivered by one of the acoustic transducers TA_{K J}of receiving antenna A_k.

Each acoustic transducer TA _kj of the antenna A _k implements, at each acquisition step, an elementary acquisition step during which it measures an acoustic signal for a non-zero acquisition time, the antenna A _k being in a predetermined reception configuration throughout the acquisition period.

Advantageously, the acquisition times are the same for all the acoustic transducers.

Advantageously, during the same acquisition step, the elementary acquisition steps of the different transducers of the same antenna are implemented substantially simultaneously or simultaneously. In other words, they start substantially at the same initial instant and end at substantially the same final instant. Advantageously, the elementary acquisition steps of the acoustic transducers of the different reception antennas of the same acquisition step are also implemented simultaneously. This simultaneity is, for example, managed by the processing and control means TRC generating acquisition commands sent to the various reception antennas A_k. As a variant, this simultaneity is, for example, obtained by internal clocks of the various reception antennas so, for example, that each acoustic transducer implements an elementary acquisition step at identical regular time intervals for all the transducers, for an identical acquisition time for all the transducers.

Each acoustic transducer TA _kj delivers, during each elementary acquisition step, an acoustic measurement M _kj representative of an acoustic intensity and an acoustic frequency as a function of time over the acquisition duration.

The acoustic measurement M _kj delivered by an acoustic transducer comprises, for example, several series of elementary intensity measurements taken during different elementary durations of the acquisition duration. Each series of elementary measurements is carried out at a predetermined acoustic frequency or in a predetermined acoustic frequency band distinct from the other frequencies/frequency bands of the other elementary series. The acoustic measurement delivered by a transducer is, for example, in the form of a series of intensity-time matrices produced at different frequencies. Each matrix or elementary measurement comprises intensity values measured for different elementary durations at a determined frequency or in a determined frequency band. The different elementary measurements are obtained at different frequencies or in different frequency bands.

The acoustic measurements J _k with k = 1 to K are transmitted to the processing and control means TRC.

These acoustic measurements can undergo at least one pre-processing step by elementary pre-processing means included in the sonar devices before being transmitted to the processing and control means TRC and/or at least one pre-processing step by the processing and before being used to implement step 200. The pre-processing steps may, for example, include filtering, coherent processing to correlate a received signal with a transmitted signal in the case of a sonar system active or a normalization for the detection of noisemakers.

The sonar system SYS comprises localization means LOC_k with k = 1 to K visible in figure 1, making it possible to locate each sonar antenna in the same global frame of reference, for example a terrestrial frame of reference, that is to say a frame of reference linked to the earth, or a frame of reference linked to one of the sonar devices or to the processing and control device TRC, at each cycle for the duration of acquisition of the transducers of the antenna. The location means are, for example, satellite location means comprising LOC receivers_kof satellite signals installed on the floating supports. This example is absolutely not limiting, other means of location can be used. Inertial units linked to the main supports F_k, can for example be provided.

In one embodiment, the processing and control means TRC are configured to generate, at each cycle, acquisition commands OA _k sent to the reception antennas A _k so that the transducers of the acoustic reception antennas A _k implement, at each acquisition step, the acoustic measurement step for an acquisition duration. As a variant, the antennas are configured to implement the measurement steps at regular time intervals as specified previously.

Step 200, for detecting NB noisemakers Bb with b=1 to NB from the acoustic measurements comprises the following steps described below. NB is a number of noisemakers detected during step 200. This number NB can be zero.

In a step 201, sonar channels are formed from acoustic measurements acquired during step 100. More precisely, for each antenna A_k, at least one sonar channel v is formed from the set of acoustic measurements J_kacquired by antenna A_k. A sonar channel is formed by applying a set of electronic delays to the different sets of acoustic measurements J_kdelivered by the various acoustic transducers A_k. The applied delay sets are different for the different sonar channels. This makes it possible to obtain, for each channel v, an acoustic signal S_kv. The acoustic signal S_kvformed by a channel v is representative of an acoustic intensity as a function of the acoustic frequency according to the listening direction representative of the corresponding channel. At the end of step 201, a set of acoustic signals S is obtained_kvwith v = 1 to Vk where Vk is an integer greater than or equal to 1 of channels formed for the antenna k. This set is, for example, in the form of a frequency matrix – channel directivity comprising different values of acoustic signal intensity S_k obtained for different frequency-channel directivity pairs.

In the particular case of a linear steerable receiving antenna, channels are formed in azimuth and/or elevation (site).

If the antenna extends substantially linearly and substantially along a vertical axis z, channels are formed only in elevation and if the antenna extends substantially linearly and substantially along a horizontal axis, channels are formed only in azimuth. If the antenna is in an intermediate orientation, azimuth and elevation paths are advantageously formed.

In a step 202, for each receiving antenna A _k , L _k local noisemakers B _kl , l = 1 to L _k are detected, when L _k is non-zero and is the number of local noisemakers detected, from the sonar channels formed for the reception antenna A _{k ,} according to a predetermined detection criterion. Alternatively, no local noisemaker is detected during step 202.

Each local noisemaker B_k.l. detected during step 202 is characterized by a set of characteristics CB_k.l.including:
- an SI acoustic signal_k.l.representative of an acoustic intensity as a function of the acoustic frequency defined for the corresponding channel directivity,
- a Z positioning zone_k.l.in which the local noise emitter is located, the positioning zone is defined (positioned and oriented) in a local reference frame linked to antenna A_k,
- an identification of the reception antenna A_kat its origin.

A linear antenna makes it possible to obtain different directions of listening by forming several pathways by applying different sets of delays to the same set of acoustic measurements acquired simultaneously by the various acoustic transducers of the antenna. It is possible to form different channels according to different respective channel directions (or channel directivities) forming different angles with the longitudinal axis l_kantenna A_k. On the other hand, in the absence of directivity of the acoustic transducers, it is not possible to form channels according to directions forming different angles around the longitudinal axis of the antenna. In other words, it is possible to deduce from the acoustic measurements acquired by the antenna, a first conical surface C_k.l.of axis corresponding to the longitudinal axis l_kantenna A_k, as visible in figure 4, on which the local noise generator B is located_lk. In other words, it is possible to deduce an angle γ_k.l.formed between the axis l_k and a direction passing through the top SO and including the noisemaker but it is not possible to deduce the direction in which it is located around the axis l_k, i.e. the angle ββ_k.l.formed by a projection of the axis t, comprising the vertex SO and the local noisemaker B_lk, with a reference direction r_kperpendicular to the_k, around the l-axis_k. There is an ambiguity on the position of the noisemaker.

In practice, the positioning zone defined for a local noisemaker B_k.l.detected from a channel with a direction (or channel directivity) forming an angle γ_k.l.with the longitudinal axis l_kantenna A_k corresponds to a globally conical local volume of axis l_kand with vertex SO, comprising the first local conical surface C_k.l. and having an angular opening around the local angle γ_k.l.. The angular opening decreases with the angle γ_kbfrom 0 to π/2 because the precision of angular positioning, due to the fineness of the track, increases in this direction.

The detection 202 of the local noise emitters B _k1 is carried out from the channels formed according to a detection criterion.

The detection criterion can be predetermined or depend on at least one reception configuration parameter of the antenna at the current cycle and/or at a previous cycle and/or on channels formed at a previous cycle for the same antenna and/ or characteristics of buzzers B_k.l. detected in a previous cycle and/or from the receiving antenna in the current cycle and/or in a previous cycle.

The detection criterion may comprise an intensity threshold beyond which a noisemaker is detected, which may be fixed or may depend on at least one of the aforementioned parameters and/or an acoustic frequency. The selection criterion may comprise a frequency criterion, which may comprise an acoustic frequency band within which the acoustic frequency must lie. This frequency criterion can be fixed or depend on at least one of the aforementioned parameters.

At the end of step 202, a set of local noisemakers B is obtained_k.l.may be empty. Each local noisemaker is characterized by a set of CB characteristics_k.l.including Z positioning area_k.l.in which the local noisemaker is detected. The Z positioning area_k.l.is defined in a local coordinate system linked to the reception antenna A_kcorresponding. The spatial coverage areas of the antennas overlap partially, certain local noise emitters detected by different antennas corresponding to the same noise emitter.

Step 203 is a merging step comprising a step 203a of changing the benchmark of the positioning zones Z _kl of the local noisemakers B _kl defined in the respective local repositories to define them in the global repository and a step 203b of merging the noisemakers premises B _kl respecting a predetermined merging criterion. At the end of step 203, a number NB of noisemakers of interest Bb is obtained with b=1 to NB where NB is the number of noisemakers of interest greater than or equal to 1. Alternatively, the number of noisemakers is zero. The set of noisemakers of interest Bb comprises a set of at least one noisemaker of interest resulting from the fusion of local noisemakers when the latter satisfy the fusion criterion and/or a set of at least one local noisemaker (when the latter is detected by a single antenna).

During step 203a, a positioning zone ZG _kl of each local noise emitter B _kl in the global frame of reference is determined from its positioning zone P _kl in the local frame of reference of the antenna A _k .

This step is carried out from the values of the parameters of the reception configurations of the reception antennas and from the positions of the reception antennas in the global reference frame, during the acquisition step, and more particularly during the elementary measurement steps. implemented by the various acoustic transducers.

This step is advantageously carried out on the basis of a probability of detection of the antenna or POD, in reference to the Anglo-Saxon expression “Performance of the Day”. The POD defines a probability of detection of a noise emitter by means of measurements obtained by the antenna in the spatial coverage area of the receiving antenna. The probability of detecting a noise emitter located outside the spatial coverage area, using acoustic measurements acquired by the antenna, is zero. The shapes of the spatial coverage areas obtained are relatively complex and non-uniform due to the non-linearity of sound propagation in water. They are defined (position, orientation) in a reference linked to the antenna.

The method can then comprise a step of determining the POD of the antenna. The POD is, for example, determined, by a method known to those skilled in the art, from:
- at least one technical characteristic of the antenna taken from a detection frequency band, a maximum range, a gain and an inherent noise,
- at least one environmental characteristic taken from a temperature or a temperature curve around the sensor, a depth of the seabed, a type of seabed, sea noise related to traffic and/or the state of the sea , a wave direction.

Alternatively, the POD is predetermined for the values of the receive antenna configuration parameters. The system includes for example a database storing POD values for different reception configurations of the antenna.

The merging step 203b consists in merging local noisemakers B _kl , when the number of local noisemakers detected during step 203a is greater than 1. This step consists in merging the local noisemakers B _kl respecting a predetermined merging criterion, from the positioning zones ZG _kl of the local noise emitters B _kl in the global frame of reference and from the other characteristics of the local noise emitters, such as the acoustic signals (intensity/frequency) SI _kl associated with the respective local noise emitters.

The merging criterion between local noisemakers B _k1 is a spatial and frequency concordance criterion. Two local noisemakers are merged to form a noisemaker of interest if there is sufficient spatial agreement of their respective positioning zones and possibly sufficient frequency matching of the signals associated with these local noisemakers in an overlapping zone of the spatial coverage zones of the antennae.

For example, step 203b comprises, for each pair of local noise emitters detected from different receiving antennas whose respective spatial coverage areas overlap at least partially :
- a step of verifying compliance with a criterion of spatial concordance between the two local noisemakers in the global frame of reference consisting in checking whether there is an intersection between the positioning zones of the two local noisemakers in a zone of overlapping zones of spatial coverage of the antennas from which the two local noisemakers were detected,
- and if the spatial concordance criterion is respected between these two local noise emitters, a possible step of verifying compliance with a frequency concordance criterion between these local noise emitters.

The step of verifying the spatial matching criterion consists, for example, in verifying whether the absolute value of the difference between the acoustic frequencies of the signals of the two local noise emitters is less than or equal to a predetermined frequency difference threshold.

Only the local noisemakers respecting the spatial concordance and the possible frequency concordance are merged.

During step 203b, when noisemakers are merged, a characterization CBIb of the noisemaker of interest is also constructed from the characteristics of local noisemakers from which the noisemaker of interest Bb originates.

The noisemaker of interest Bb is characterized by a set of primary characteristics CBb, when it is obtained from the fusion of several local noisemakers, by:
- a set ESb of at least one acoustic signal comprising the acoustic signal of each local noise generator B_k.l. from which the noisemaker of interest B comes_b,
- a positioning zone Zb of the noisemaker of interest Bb, defined in the global repository,
- the list of each reception antenna at the origin of the noise generator of interest.

The positioning zone Zb of a noisemaker of interest Bb resulting from the fusion of several local noisemakers is obtained by determining an overlapping zone of the positioning zones of the local noisemakers from which it comes.

The primary characteristics of the noisemakers of interest corresponding to local noisemakers (not merged) remain the characteristics of the local noisemakers.

The following steps are implemented when at least one noisemaker of interest is detected. When no noisemaker of interest is detected, we return, for example, directly to the acquisition step without going through the following steps.

The method advantageously, but not necessarily, comprises at least one of the following steps: determining 204 kinetic characteristics of the noisemakers of interest, classifying 205 the noisemakers of interest, estimating 206 an evolution of the noisemakers of interest, a construction step 207 a summary relating to the noisemakers of interest.

During step 204 of determining the kinetic characteristics CCb of the noisemakers of interest Bb, one calculates, for example, a direction of displacement and/or a speed of each noisemaker of interest Bb and/or an acceleration of the noisemaker of interest.

This step is performed, for each noisemaker of interest Bb, from the set of primary characteristics CBb of the noisemaker of interest Bb.

This step can be performed by a Doppler method or by comparison with the previous cycle.

The Doppler method can be used for noisemakers of interest obtained by fusion of local noisemakers detected by at least two acoustic reception antennas, that is to say, detected from channels formed for at least two acoustic reception antennas. This method is based on the frequency shift of the acoustic signals of the merged local noisemakers with respect to a reference frequency.

The "Doppler" effect tells us that an acoustic reception antenna having acquired, for the local noisemaker at the origin of the noisemaker of interest, a signal presenting a positive frequency offset with respect to a predetermined reference frequency, sees the noisemaker to approach it and that an acoustic reception antenna having acquired, for the local noisemaker at the origin of the noisemaker of interest, a signal having a negative frequency offset with respect to the reference frequency sees the noisemaker moving away from her.

The reference frequency is normally the emission frequency of the noisemaker of interest which is stationary with respect to the antenna. However, since this frequency is not known, a reference frequency is chosen arbitrarily. This is, for example, a frequency of an acoustic signal from a local noisemaker at the origin of the noisemaker of interest. This frequency is measured by one of the acoustic reception antennas. This antenna is identified in the characteristics of the noisemaker of interest.

Step 204 therefore includes:
- a step of determining a reference frequency taken from a frequency of an acoustic signal of one of the local noisemakers at the origin of the noisemaker of interest,
- a step of comparing each of the frequencies of the acoustic signals of the other local noisemakers at the origin of the noisemaker of interest with the reference frequency,
- A step of determining the orientation and the direction of the speed vector of the noisemaker from the results of these comparisons and the positions of the reception antennas having detected the local noisemakers at the origin of the noisemaker of interest.

The method "by comparison with the previous cycle" consists, from positioning zones of a noisemaker calculated at two cycles (current cycle and previous cycle) in the global frame of reference, in calculating the speed from the distance traveled between these cycles and the time elapsed between the acquisition steps of these two cycles. This step can be carried out before the classification step or after the classification step using the result of the classification step of the noisemaker of interest and possibly from a synthesis obtained in a cycle prior to the current cycle .

The step 205 of classifying each noisemaker of interest Bb is carried out on the basis of the primary characteristics CBb of the noisemaker of interest Bb concerned and possibly the kinetic characteristics CCb of the noisemaker of interest.

The classification step 205 consists in associating the noisemaker of interest Bb with a type of noisemaker Tb or in identifying the noisemaker, the noisemaker then being for example associated with an identity Ib.

The step 205 of classification of the noisemaker of interest Bb is advantageously implemented from known characteristics of noisemakers of different known types stored in a so-called CLAS classification database belonging to the system SYS. Each type of noisemaker is associated with different characteristics to which the characteristics of the noisemaker and possibly its kinetic characteristics are compared. The type of noisemaker associated with a noisemaker of interest is determined by a conventional comparison method, for example, by correlation or by a matching method.

For example, a noisemaker of interest Bb can be associated with a type of marine or carrier building according to its acoustic frequency (obtained from the frequency of the acoustic signal of at least one local noisemaker at the origin of the noisemaker d of interest) and its speed and frequency and speed characteristics of known carriers, such as a freighter and a speedboat. In particular, a speedboat will have a different frequency signature and speed than a freighter.

The acoustic intensity of the acoustic signal from an antenna originating the noisemaker of interest can be used for classification in combination with the positions of the antenna and the acoustic noisemaker and, optionally, a reception characteristic of the antenna.

The evolution of each noisemaker of interest is estimated in a step 206, from:
- at least one of the primary characteristics CBb of the noisemaker of interest Bb,
- the kinetic characteristics of the noisemaker of interest,
- and possibly the classification of the noisemaker of interest (type or identification).

This step consists in estimating an evolution of the behavior of a noise generator of interest Bb at one or more following cycles. It uses primary characteristics CBb and kinetic characteristics CCb of the noisemaker of interest Bb, and possibly the classification (type Tb or identity Ib) of the noisemaker of interest and/or possibly at least one primary characteristic CBb and/or one kinetic characteristic CCb of a noisemaker of the same type or of the noisemaker of interest obtained during at least one previous cycle, to estimate at least one primary characteristic of the noisemaker of interest and/or at least one kinetic characteristic of the noisemaker with one or more subsequent cycles. At the end of this step, we obtain an estimate of a set of characteristics of the noise generator ECIb at least one following cycle.

It is, for example, possible to estimate a position of the noisemaker of interest Bb at a following cycle from the positioning zone Zb of the noisemaker of interest Bb calculated at the current cycle, that is to say at the cycle in progress, and its estimated speed during step 204.

It is possible to estimate a frequency and an intensity of an acoustic signal received by a reception antenna at the origin of the detection of the noisemaker of interest in the next cycle from the current speed of the noisemaker of interest of its current position, the current position of the receiving antenna at its origin and possibly its position at one or more previous cycles. The estimation of the frequency can in particular be based on the Doppler effect. These calculations are standard for those skilled in the art.

The step cycle includes a step 207 of synthesis. This step makes it possible to build, for each noisemaker of interest Bb, a synthesis Sb of its characteristics according to the following inputs:
- at least one primary characteristic CBb of the noisemaker of interest Bb,
- a possible kinetic characteristic CCb of the noise generator of interest Bb,
- and/or the possible classification (Ib or Tb) of each noisemaker of interest Bb,
and/or a possible estimation of a position of each noisemaker of interest in the next cycle and/or of at least one other characteristic, for example of at least one other primary characteristic of the noisemaker of interest.

The synthesis Sb can, for example, be constructed to be viewable by a user. It can represent positions (positioning zones) of different noisemakers of interest on a three-dimensional map by associating, with each noisemaker of interest, a speed vector and/or a possible estimate of a position of the noisemaker of interest to the next cycle and/or type.

The syntheses determined at the different cycles are advantageously stored in a database of syntheses.

The method according to the invention comprises a third step 300, consisting in determining optimal reception configurations of reception antennas of a subset of antennas of the set from the characteristics of the noise generators Bb with b=1 to NB.

This step comprises a step 301 determining an order of priority of noisemakers of interest Bb from characteristics of the noisemakers of interest or from the synthesis when a synthesis is constructed. This order of priority is determined for a given mission.

This step consists in establishing a so-called order of priority of interest OP, of the noisemakers of interest, from a predetermined order of priority and from at least one characteristic of the set of characteristics CBIb calculated for each noisemaker . This predetermined order of priority is, for example, stored in a so-called PRIO priority database.

This characteristic presents, for example, an order of priority according to the type of noise generator. The step therefore consists in establishing an order of priority of interest of the noisemakers of interest according to the types of noisemakers (obtained during the classification step) and the predetermined order of priority.

For example, in the case of a drug trafficking detection mission, outboard-type noisemakers will have priority over cargo ships, which will have priority over whales. A priority noisemaker is, for example, a speedboat heading towards a predetermined zone, for example a coast, and/or exhibiting a speed comprised within a predetermined speed interval.

For the prioritization of noisemakers, different weights can be associated with different characteristics of noisemakers to prioritize these noisemakers.

Step 300 then comprises a step 302 of determining optimal reception configurations of a subset of reception antennas from the characteristics of the noisemakers of interest or from the synthesis, when a synthesis is constructed, and from the order of priority of interest of the noisemakers of interest. It is also carried out, from the adjustable configuration parameters, of the various reception antennas of the sub-assembly. More precisely, this step is carried out from sets of possible reception configurations for each reception antenna of the subset. Each receive configuration is defined by a set of adjustable configuration parameter values. The set of possible reception configurations of an antenna corresponds to a set of possible sets of values of the possible adjustable configuration parameters.

The antenna subset may comprise all or part of the antennas of the set.

The method may include a step 302a for determining the subset of antennas of the set of antennas to be reconfigured. This subset can be empty or include one or more antennas. The subset of antennas to be reconfigured is determined from at least one characteristic of at least one noisemaker of interest, for example the noisemaker of interest having the highest priority, or from several noisemakers of interest , and optionally at least one other characteristic of the noisemaker of interest. The subset is also determined from at least one technical characteristic of the reception antennas of the set, taken from the antenna technical characteristics listed above, from the current configurations of the reception antennas, from the positions of the various receiving antennas at the time of the measurement.

This step 302a may consist in determining, among the antennas of the set, the antennas capable of measuring acoustic signals coming from the noisemaker of priority interest or from at least one of the noisemakers of interest of the set in the current cycle or the next cycle.

This step 302a of determining the subset may include:
- a step of selecting reception antennas capable of measuring acoustic signals having frequency and/or intensity characteristics representative of the noise generator of interest. Indeed, it is not useful to reconfigure antennas unsuitable for detecting a frequency emitted by the noise generator of interest. In other words, only the antennas of the set capable of detecting at least part of the signal emitted by the noise generator of interest are selected,
- and/or a selection step, of the reception antennas of the set of which at least one of the possible PODs comprises an estimated position of the noise generator of interest at a following cycle. Indeed, it is not useful to reconfigure reception antennas unsuitable for detecting the noisemaker of interest in the next cycle.

An antenna is selected if it satisfies one and/or the other of these selection criteria.

This method can therefore comprise a step of determining a set of possible PODs for each reception antenna from a set of possible configurations of the antenna, that is to say for different sets of values of the parameters of antenna configuration.

As a variant, the method does not include the step of selecting the subset of antennas to be reconfigured. The antenna subset to be reconfigured is then the receive antenna set. However, this solution is more computationally expensive.

The method then comprises a step 302b of determining, for each reception antenna of the subset, an optimal set of values of the adjustable configuration parameters described previously. This optimal set of parameters defines the optimal configuration of the reception antenna considered in order to follow the noisemaker of interest in the following cycle and/or to improve the precision of at least one characteristic of the noisemaker of interest (for example, its positioning zone).

This step includes for example, for each reception antenna of the subset, the following sequence of steps:
- check if the antenna is likely to detect the noisemaker of priority interest in the next cycle, and,
if so, determining an optimal configuration of the reception antenna, taken from among a subset of configurations of the reception antenna, in which the antenna follows the noisemaker of interest at the next cycle and/or makes it possible to improve the precision of at least one characteristic of the noisemaker of interest (for example on its positioning zone),
if not, the next priority noisemaker of interest becomes the priority noisemaker.

Step 302b uses the POD of a receive antenna of the subset to determine the optimal configuration for that receive antenna.

The step of determining the optimal configuration consists, for example, in determining the configuration of the antenna in which the antenna has a maximum probability of detecting the noisemaker of interest at one or more following cycles, among the subset of configurations. This step uses antenna PODs determined for a set of reception configuration the antenna, an antenna position at the current cycle, an estimate of the antenna position, an antenna position at the current cycle or several cycles, for example in the horizontal plane, and a position of the noisemaker of interest in the current cycle and/or an estimate of a position of the noisemaker in this or these following cycles.

A BPOD database advantageously stores PODs of the antennas defined for different possible configurations of the antenna.

The optimal configuration is, for example, the one in which the probability of detection of the noisemaker of interest, at a following cycle or during several following cycles, is maximum. As a variant, the optimum configuration is that in which the probability of detection of the noisemaker is non-zero during a maximum of following cycles. The optimal configuration is, for example, determined by simulation.

If there are several antenna configurations of the subset of configurations presenting the same maximum probability of detection of the noise maker of interest, then the noise maker of interest becomes the next priority noise maker and the subset of configurations contains only the configurations with the same maximum probability of detection.

By choosing a configuration in which the reception antenna has a non-zero probability of detecting the noisemaker of interest according to the estimation of the evolution of the noisemaker, this makes it possible to obtain information on the noisemaker by the antenna of reception in the next cycle and therefore to improve the precision on the characteristics of the noise generator of interest and/or to validate the characteristics determined in the previous cycle (confirmation of frequency/classification/positioning; and/or to improve the positioning precision and/or to obtain an additional characteristic of the noisemaker (for example the classification) and possibly to complete the kinetic characteristics of the noisemaker of interest by completing the path taken by the noisemaker of interest during the following cycles.

In the case of an application to the surveillance of drug trafficking, a speedboat going towards the coast and moving only at night can potentially be representative of the presence of drug trafficking.

The subset of configurations of a reception antenna, among which the optimal configuration is determined, comprises for example a set of configurations verifying a proximity criterion with the current configuration. Alternatively, the subset of configurations includes all possible configurations of the receiving antenna. The latter solution is more computationally expensive. Furthermore, it may take a long time to modify the configuration of the antenna if the current configuration and the following configuration are far from each other, which may limit the performance of the system in terms of monitoring by lengthening latency times. between the acquisitions of two consecutive cycles. In addition, a significant modification of the configuration of the antenna can be costly in terms of energy.

The step 302 consisting in determining, for each reception antenna, an optimal configuration, advantageously uses at least one environmental characteristic taken from among the environmental parameters listed above.

In addition, the synthesis determined at a cycle is for example compared to a previous cycle in order to allow learning with respect to the technical (capacity, failure) and strategic (mission) device of the system and thus improve the cycles following the syntheses and hypotheses made. during the process (for example during the estimation of the evolution).

The comparison can be a calculation of the difference, for example between the position that was predicted for a noisemaker against the refined position obtained in the following cycle. If there is too big a difference it may be due to:
- poor anticipation due to false hypotheses (example: speeds of the noisemaker or direction) because lack of information on this noisemaker;
- a malfunction of an antenna for example which therefore does not detect the noisemaker well.

The reconfiguration step 400 is then implemented by the adjustment means REG _k so that during the next implementation of the cycle of steps the antennas of the subset acquire acoustic measurements in these optimal reception configurations during of the next cycle of steps. In other words, each of the reception antennas of the subset is in its optimum reception configuration during the acquisition step of the following cycle.

The summaries determined during the various cycles are, for example transmitted to an operator, to help him make a decision, or used by the processing and control means TRC to construct an overall synthesis of the behavior of the noisemaker of interest over several cycles. and possibly trigger an alarm in case of detection of suspicious behavior of a noisemaker of interest.

The system according to the invention constitutes an autonomous reconfigurable permanent or semi-permanent sonar surveillance system to improve its capabilities of detection, location of possible classification and/or tracking in a given maritime zone where the set of antennas is located. independent reception.

An example of a sonar device comprising one of the reconfigurable acoustic reception antennas is represented in figure 5.

The sonar device D comprises a float F and a dive line LP connecting the float F to a support S. The support S has negative buoyancy. The support S connects the dive line LP to an acoustic receiving antenna A.

The antenna A being one of the antennas A _k comprises a plurality of acoustic transducers TAj , j=1 to N where N is an integer greater than 1 corresponding to the acoustic transducers TA _kj .

The antenna A comprises an antenna body C integrating the acoustic transducers TAj of the antenna A _k . The antenna body C is an elongated body, extending longitudinally, from a first end E1 to a second end E2.

The antenna body C is connected to the support S.

As visible in figure 5, the antenna A is linear. It comprises a plurality of acoustic transducers distributed along a line of transducers which may be straight, that is to say rectilinear. The antenna body C is elongated along the line of transducers.

The acoustic transducers TA _j are arranged at different curvilinear abscissae along the line of transducers d. The antenna of the embodiment of FIG. 1 comprises a single acoustic transducer at each curvilinear abscissa. As a variant, the antenna comprises several acoustic transducers at each curvilinear abscissa. Acoustic transducers are, for example around a line of transducers.

In the non-limiting embodiment of FIG. 5, this line of transducers is a straight line d.

The elongated body C is connected by the first end E1 to the support S and, more particularly, to a fixed connection point with respect to the support PL.

In the non-limiting embodiment of Figure 5, the antenna is in ball joint with the support S. Thus, the first longitudinal end E1 is fixed in translation relative to the support S along three axes of an orthogonal reference linked to the support S The connection point PL is the center of the patella in this embodiment.

The second end E2 of the antenna body C is free.

The sonar device D is configured to operate, that is to say to perform acoustic measurements and locate noisemakers, when it is in a reception configuration. The sonar device D according to the invention is capable of being in several reception configurations.

In each reception configuration, as represented in FIG. 5, the body of the antenna C and the support S are totally immersed and the antenna is in a reception configuration.

In the non-limiting case of the device of FIG. 5, the float F floats on the surface of the water and the diving line LP extends substantially vertically under the effect of the positive buoyancy of the float F and of the negative buoyancy of the support S. A vertical direction or a vertical axis is substantially perpendicular to the surface of the sea in a calm sea state.

The acoustic reception antenna is connected to the support S and configured in such a way as to be capable of occupying several orientations in a frame linked to the support centered on the point of connection PL.

The antenna is likely to be in a low vertical orientation OVB visible in Figure 5, in which the antenna body C is suspended from the support S and extends substantially vertically from the first end E1 to the second end E2 towards the seabed.

The antenna body C is configured and connected to the connection point PL so that the second end E2 is movable relative to the support S and relative to the first end E1 and more particularly so that a elevation angle and an azimuth of the second end E2 in an orthogonal reference (r; x1; z) linked to the support S and centered on the point of connection PL are variable.

Each antenna reception configuration is characterized by an elevation angle and an azimuth (when it exists).

The sonar device D according to the invention also comprises means for adjusting the orientation of the antenna A, making it possible to adjust an elevation angle and an azimuth of the second end E2 with respect to the support, i.e. say in a reference linked to the support S centered on the point of connection PL. These orientation adjustment means make it possible to adjust the orientation of the antenna when the sonar device D is in a reception configuration or the antenna is in a reception configuration and the support S is fixed with respect to the terrestrial reference. In other words, the orientation adjustment means make it possible to adjust a position of the second end E2 of the antenna body C relative to the support S according to the three directions of a three-dimensional reference linked to the support S when the support S occupies a fixed position in the terrestrial frame of reference.

The orientation adjustment means making it possible to ensure this adjustment when the sonar device D is in a reception configuration and the support S is fixed with respect to the terrestrial reference.

This makes it possible to modify an orientation of the antenna in a reference linked to the support S, that is to say an orientation of the line of transducers when it is straight or more generally a straight line connecting the two ends E1 and E2 or the point of connection PL and E2.

The angle of elevation of the second end E2 is the angle formed between a horizontal plane (r; x1) passing through the connection point PL and the straight line connecting the connection point PL to the end E2 and the azimuth of the second end E2 is the angle formed around a vertical axis z of the reference (r; x1; z) linked to the support S between a horizontal axis of reference r of this reference and the straight line connecting the point of connection PL to l end E2. The elevation angle is positive when the second end is above the horizontal plane (r; x1) and negative when it is below.

The orientation adjustment means, belonging to the elementary adjustment means REG _k , comprise drive means ENT making it possible, when the support S is fixed, to move the second end E2 of the antenna body C relative to the support S according to the three directions of the reference linked to the support. These drive means ENT make it possible to move the second end E2 with respect to the support S so as to vary its elevation angle and its azimuth in the reference frame linked to the support. This displacement of the second end E2 relative to the support causes a displacement of the second end E2 relative to the first end E1.

Thus the drive means ENT make it possible to move the end E2, even when the support S is fixed in the terrestrial reference frame, relative to the support S, from the position it occupies when the antenna body C is in the low vertical orientation OVB to an inclined orientation OI, as shown in dotted lines in FIG. 5. In the low vertical orientation OVB, the second end has a site angle α1 of -π/2, the azimuth n' being undefined, i.e. does not exist, for this elevation angle.

The azimuth exists and is adjustable when the elevation angle is different from -π/2 or π/2.

In the tilted orientation of Figure 5, the second end has a negative site angle α2 greater than -π/2 and an azimuth β2.

Advantageously, the drive means ENT make it possible to continuously vary the elevation angle of the second end E2 between −π/2 and a maximum elevation angle. The maximum elevation angle is greater than -π/2. It can be negative, zero or positive. It can, for example, be equal to π/2.

Advantageously, the drive means ENT make it possible to continuously vary the azimuth of the second end E2 between 0 and 2π excluded when the elevation angle is different from −π/2 and π/2.

The orientation setting means also comprises control means for controlling the drive means so that the drive means ENT sets the elevation angle of the second end E2 to a target elevation angle and the azimuth of the second end E2 on a target azimuth, when the support S is fixed in the terrestrial frame of reference, that is to say with respect to the earth.

The antenna A of the sonar device D according to the invention is thus dynamically orientable in space, even if the support S is fixed.

The possible adjustment of the angle of elevation and of the angle of elevation of the second end E2 allows a reconfiguration of the antenna A according to the characteristics of the noisemakers of interest, which makes it possible to improve the detection capabilities , location and classification of the sonar system according to the invention. It is, for example, possible to improve the positioning accuracy of the noisemaker of interest by modifying the orientation of the antenna for the following cycle and therefore the conical surface C1, during the following cycle, which makes it possible to improve the accuracy of the positioning zone of a noisemaker of interest detected at a previous cycle by the same antenna or by another antenna. This reorientation capability also makes it possible to modify the orientation of the antenna for the next cycle, depending on the movement of the noisemaker of interest to follow it to the next cycle.

The system according to the invention makes it possible to obtain good performance in terms of detection, location, classification and tracking of noisemakers of interest from sonar devices having a linear antenna of simple geometry and economical in terms of acoustic transducers. It is not necessary to provide directional acoustic transducers allowing the ambiguity to be resolved.

The sonar device according to the invention is capable of being implemented from a static support. It does not require the towing of the antenna by a marine vessel, which makes it economical and likely to be used in an area of limited size. He is also discreet.

In addition, this sonar device is easily deployable from a single attachment point (buoy).

In the particular embodiment of FIG. 5, the transducer line d is a straight line. The antenna is configured so that the line of transducers has this linear shape in the receive configuration, regardless of the position of the end E2.

In other words, the drive means ENT make it possible, as represented in FIG. 5, to vary an inclination of the antenna A, in particular of the straight line of transducers with respect to a horizontal plane linked to the support S and with respect to a vertical plane linked to the support S and containing the axis r.

In a variant represented in FIG. 6, the antenna AA differs from the antenna of FIG. 5 in that it is flexible. In other words, the transducers are distributed along a line of transducers capable of being straight or rectilinear and capable of bending under the effect of a displacement of the end E2 relative to the support S. This is permitted by the flexibility of the DC antenna body.

The acoustic transducers are arranged at different curvilinear abscissae along the line of transducers. The antenna of the embodiment of FIG. 6 comprises a single acoustic transducer at each curvilinear abscissa. As a variant, the antenna comprises several acoustic transducers at each curvilinear abscissa, the acoustic transducers being distributed around a line of transducers.

The antenna AA is, for example, configured to extend in a substantially vertical straight line in the low vertical orientation OVB represented in FIG. 6 on the left and to be curved in inclined configurations such as represented in FIGS. 6 in the middle and at LAW. The antenna undergoes bending when the drive means ENT move the second end E2 away from its equilibrium position shown in Figure 6 on the left.

The end E2 is, for example, capable of occupying the points of a globally semi-spherical or spherical SURF surface or globally in ellipsoid or half-ellipsoid as represented in FIG. 6.

Antenna A can be connected to support S by a ball joint as shown in figure 5.

More generally, the antenna can be connected to the support S by a connection with three degrees of freedom in rotation. A certain displacement can, for example, be authorized along one or more axes of translation.

For this purpose, the first end E1 of the flexible antenna AA or straight linear A, is, for example, connected to the support S by a connecting body capable of deforming under the effect of the displacement of the second end E2 by the ENT drive means with respect to its equilibrium position.

Alternatively, the antenna body CC is flexible and fixed directly to the support S, in other words the first end E1 and the connection point PL occupy the same position.

The drive means ENT comprise, for example, as represented in FIG. 5, a thruster PROP making it possible to move the second end E2 relative to the support S (when the support is fixed in the terrestrial frame of reference) at least in two orthogonal directions in a horizontal plane, and preferably, but not necessarily, along a vertical axis z.

In the non-limiting example of the figures, the thruster PROP comprises turboprops configured and arranged around the second end E2 so as to allow the second end to be moved relative to the support S in three orthogonal directions, when the support is fixed in the terrestrial reference.

Advantageously, the drive means ENT comprise a buoyancy modification device MF mounted on the second end E2. This makes it possible to limit the energy consumed by the PROP thruster to modify its elevation angle, then to maintain it at a predetermined elevation angle without using the thruster and therefore to limit the energy consumed. Furthermore, the fact of not having to use the drive means ENT to maintain the elevation angle fixed makes it possible to avoid pollution of the measurements acquired by the antenna by acoustic, electrical or magnetic noise, liable to be generated by the drive means ENT.

To this end, the drive means ENT are configured to make it possible to maintain the site angle constant over the entire site angle range extending from the minimum site angle to the maximum site angle .

The buoyancy modification device makes it possible to accelerate the reconfiguration of the antenna and therefore to limit the latency time between two successive acquisitions.

Advantageously but not necessarily, the low vertical orientation OVB is a rest or equilibrium orientation of the antenna body C. This is, for example, the rest orientation of the antenna when variation means MF buoyancy exhibit minimal buoyancy while a PROP thruster, linked to the antenna, is stationary.

Advantageously, the antenna body C can have neutral buoyancy. Alternatively, the antenna body has negative or positive buoyancy.

As represented in FIG. 7, the device for modifying the buoyancy MF comprises, for example, a ballast BAL with variable density, that is to say with fixed volume and variable mass or with fixed mass and variable volume and controllable means making it possible to vary this mass or this volume.

For example, the BAL ballast has a fixed volume and a variable mass. It comprises a housing BOIT containing a gas and a liquid and a piston PS sealingly separating a first sealed compartment CE1 of the housing BOIT containing the gas G and a second compartment CE2 of the housing BOIT containing the liquid L and fluidly communicating with the marine environment exterior via an OR orifice. The buoyancy modification device MF comprises an actuator ACT making it possible to move the piston PS in translation so as to modify the volumes of the compartments CE1 and CE2, the volume of the compartment CE1 increasing when the volume of the compartment CE2 decreases. The displacement of the piston PS in translation thus modifies the quantity of liquid in the second compartment CE2 which modifies the buoyancy of the ballast BAL also causes the modification of the volume occupied by the gas G in the first compartment CE1.

Advantageously, the drive means ENT are arranged at the level of the second end of the antenna A. This position is advantageous from the point of view of the length of the lever arm. In the case of a flexible antenna, it is also advantageous from the point of view of controlling the shape of the antenna during its movement and makes it possible to obtain a continuous evolution of the radius of curvature of the antenna over its entire length. length.

As a variant, the drive means ENT are arranged between the ends E1 and E2 or distributed along the antenna.

In the previous examples, the drive means ENT are mounted on the antenna.

As a variant, the drive means ENT comprise, for example, a cable of adjustable length connected to the antenna, for example at the second end, and a winch making it possible to adjust the length of the cable so as to make it possible to adjust the elevation angle of the second end E2 and a rotary actuator for adjusting the azimuth of the second end E2.

As a variant, the sonar device comprises drive means ENT comprising an independent thruster capable of cooperating transiently with the antenna to move the second end of the antenna. The thruster is for example of the underwater drone type.

Advantageously, the sonar device comprises immersion adjustment means or an immersion adjustment device making it possible to adjust the depth or the immersion IM of the antenna A. These means are then included in the elementary adjustment means of the sonar device. The immersion adjustment means make it possible, when the antenna is at a certain depth, to obtain acoustic measurements from an area which is a shadow area for the antenna when the latter is at another depth. A shadow zone is created by the underwater acoustic propagation defined by the bathycelerimetry profile of the acoustic waves as a function of the depth. Lowering the second antenna therefore makes it possible to move a gray area and to confirm or clarify the detection and/or the position of a noise emitter. These means therefore make it possible to improve the capacities for detecting noise emitters and therefore the capacities for locating noise emitters. Varying the immersion of the antenna can also improve the "signal to noise" level of a noisemaker detected by the antenna.

These immersion adjustment means include, for example, in a non-limiting way, a winch T making it possible to adjust the length of the diving line LP and therefore the depth of the support S. The winch T can be integrated into the float F as in figure 5 or support S.

Advantageously, the sonar device comprises relative positioning adjustment means making it possible to adjust a relative positioning of the acoustic transducers TA _j of the antenna A, when the antenna body C is fixed relative to the support S. In terms of detection, the variation of the relative positioning of the transducers conditions the performances linked to the frequency ranges detected and to the range of the antenna. A long antenna detects noise emitters emitting at very low frequency at very long distances, conversely a smaller antenna has a shorter range and makes it possible to detect noise emitters emitting at medium and high frequency. This advantage of relative positioning adjustment of the transducers therefore makes it possible to provide additional clues on the near/far location of the noisemakers. The positioning adjustment means comprise, for example, linear actuators capable of linearly moving the various transducers on the same straight line and position sensors making it possible to detect the positions of the various sensors on the straight line, the sensors sending the detected positions to transducer control means. As a variant, the transducers are kept spaced apart in pairs by compression springs, end stops allow the springs to be kept in compression. Linear actuators are provided to vary the distance between the end stops so as to vary the spacing between the transducers. Other solutions are of course possible. The immersion adjustment means are then included in the elementary adjustment means.

Thus, in the particular embodiment of FIGS. 5 and 6, each reception configuration of the reception antenna is characterized by a set of configuration parameters comprising a elevation angle, an azimuth (when it exists), an immersion of the receiving antenna and a relative position between the sensors. These configuration parameters can be adjusted independently by the elementary adjustment means.

The elementary adjustment means associated with the antenna Ak of a sonar device as described above therefore comprise the means for adjusting the orientation of the antenna, the positioning adjustment device and the immersion adjustment means .

The sonar system according to the invention may comprise a plurality of sonar devices with reconfigurable reception antenna, as represented in FIG.

More generally, the sonar system according to the invention comprises a plurality of sonar devices with reconfigurable acoustic reception antenna each comprising at least one adjustment configuration parameter taken from: an immersion (depth) of the reception antenna and/or an angle of elevation of the adjustable second end, and/or an azimuth of the adjustable second end, and/or an adjustable relative positioning between the transducers when the orientation and the immersion of the antenna are fixed, and the means of related settings.

In the embodiment of Figure 5, the antenna is linear. As a variant, the antenna is a two-dimensional antenna, the transducers being distributed in a plane, or a three-dimensional antenna, the transducers being distributed over three dimensions.

The sonar system includes sonar devices comprising at least one linear acoustic detection antenna and/or at least one two-dimensional acoustic detection antenna and/or at least one three-dimensional acoustic detection antenna.

In Figure 5, the float F or main support is located above the support S along a vertical axis.

Alternatively, the main support is located above the surface of the water, such as a platform of a helicopter, or any partially submerged or totally submerged support located above the support S along a vertical axis in operational configuration. .

The buoy to be substantially fixed relative to the terrestrial reference or to be free at sea.

More generally, the sonar system according to the invention comprises a plurality of sonar devices each comprising an antenna connected to a main support. The main supports are, for example, free buoys at sea or buoys substantially fixed with respect to land or of the helicopter type (the sonar devices are then dipped sonars). The system can include sonar devices of the different types listed above.

The sonar system according to the invention is for example passive, which gives it a certain discretion and a certain energy autonomy which makes it possible to carry out long-term monitoring, or active, it then has a greater range but is then more expensive and more energy consuming.

Advantageously, the sonar system comprises means for determining an orientation and/or a position of the support in the terrestrial reference frame. These means include, for example, an inertial unit or MEMS, making it possible to integrate the movements of the support (acceleration and angular velocity) to estimate its position and/or its orientation (roll, pitch and heading angles) and/or its speed. The support may comprise a GPS receiver making it possible to geo-locate the support by satellite. The orientation and/or position measurements of the support are advantageously used when detecting noisemakers of interest (change of frame of reference and/or fusion) and/or when determining the optimal configurations.

Advantageously, but not necessarily, the means for adjusting the orientation of the antenna comprise means for monitoring the position of the second end. These means can for example comprise MEMS making it possible to integrate the movements of the second end of the antenna. They can also use the measurements coming from the means for determining an orientation and/or a position of the support in the terrestrial reference frame to monitor the position of the second end E2.

The antenna may comprise sensors making it possible to determine a curvature of the reception antenna. This curvature is advantageously used when forming channels. This makes it possible to digitally compensate for the deformation of the antenna.

Advantageously, the reception antennas are configured so as to make it possible to detect acoustic waves having a frequency comprised between 1 kHz to 10 kHz.

The TRC processing and control means and the control means may comprise one or more dedicated electronic circuits or a general-purpose circuit. Each electronic circuit can include a reprogrammable calculation machine (a processor or a microcontroller for example) and/or a computer executing a program comprising a sequence of instructions and/or a dedicated calculation machine (for example a set of logic gates such as an FPGA, a DSP or an ASIC, or any other hardware module).

Claims (13)

Method for monitoring a maritime area from a set of acoustic reception antennas, the reception antennas of the set each comprising several acoustic transducers, the reception antennas being reconfigurable so as to be capable of being in several reception configurations in which they are immersed, the method comprising a cycle of the following successive steps:
- acquiring (100) acoustic measurements by means of the set of acoustic reception antennas, the reception antennas of the set each being in a reception configuration,
- detecting (200) a set of noise generators of interest by forming sonar channels from the acoustic measurements, each noise generator of interest being characterized by a set of at least one primary characteristic comprising a positioning zone of the noise generator defined in a global reference common to all noisemakers of interest,
and, when the set of noisemakers of interest includes at least one noisemaker of interest:
- determining (300), from the set of at least one primary characteristic, a set of optimal configuration comprising an optimal reception configuration for each antenna of a subset of the reception antennas of the set of reception antennas, so that each reception antenna of the subset is capable of detecting, in the following cycle, acoustic signals coming from a noisemaker of interest of the set of noisemakers of interest,
- reconfiguring (400) each reception antenna of the subset according to the optimal reception configuration defined for this reception antenna,
the cycle of processing steps being repeated at least once. Method according to the preceding claim, in which the step of determining (300) comprises the following steps:
- forming (201) sonar channels from acoustic measurements acquired by the set of acoustic reception antennas,
- from the channels formed, detect (202), according to a predetermined detection criterion, a set of local noisemakers, each local noisemaker of the set of local noisemakers being characterized by a set of at least one characteristic of local noisemaker comprising a zone for positioning the local noisemaker in a reference frame linked to the reception antenna,
- merging (203) local noisemakers in order to obtain a set of at least one noisemaker of interest, each noisemaker of interest being characterized by a set of noisemaker characteristics of interest comprising a positioning zone in a global reference frame common to all local noisemakers. Method according to any one of the preceding claims, in which the cycle of steps comprises a step of determining kinetic characteristics of the set of at least noisemakers of interest. Method according to the preceding claim, in which the cycle of steps comprises a step of classifying the set of at least one noisemaker of interest from the kinetic characteristics of the set of at least one noisemaker of interest and from the set of at least one primary characteristic. Method according to the preceding claim, in which the cycle of steps comprises a step of estimating an evolution of the set of at least one noisemaker of interest at a following cycle from the set of at least a primary characteristic, kinetic characteristics and from the classification of the set of at least one noisemaker of interest. Method according to the preceding claim, in which the step (300) of determining the set of optimal configuration comprises, when the set of at least one noisemaker of interest comprises several noisemakers of interest, a step (301) determining an order of priority of the noisemakers of interest, from the characteristics of the noisemakers of interest, and a step (302) of determining the set of optimal configuration from characteristics of the noisemakers of interest and from the order of priority. A method according to any preceding claim, wherein a first antenna of the subassembly is linear and comprises a body elongated from a first end (E1) to a second end (E2), determining the optimum configuration of the reception antenna of the first sonar device comprising the determination of a second end elevation angle and/or the determination of a second end azimuth (E2) in a reference frame connected to a negatively buoyant support connected to the first end of the first receive antenna, the reconfiguration of the first receive antenna including adjusting the elevation angle and/or the azimuth. A method according to any preceding claim, wherein determining the set of optimal configuration includes determining a relative positioning of the acoustic transducers of at least one second receive antenna of the subset, the reconfiguration comprising the adjustment of the relative positioning of the acoustic transducers of the second reception antenna. A method according to any preceding claim, wherein determining the optimum configuration includes determining a depth of a third antenna of the subassembly, adjusting the configuration of the third sonar device including adjusting antenna immersion. Sonar system including:
- a set of acoustic reception antennas, the reception antennas each comprising several acoustic transducers, the reception antennas being reconfigurable so as to be able to be in several reception configurations, the set of antennas being able to acquire acoustic measurements,
- adjustment means capable of reconfiguring the reception antennas according to the optimal configuration set,
- a processing device suitable for performing the steps of detecting and determining the optimal configuration set of the method according to any one of claims 1 to 9,
the sonar system being configured to implement the method according to any preceding claim. Sonar system according to the preceding claim, comprising a set of sonar devices comprising a first sonar device comprising a support (S) with negative buoyancy and a first acoustic reception antenna of the set of antennas, the first reception antenna being linear ( A) and comprising an elongated body from a first end (E1) to a second end (E2), the elongated body (C) being connected by the first end (E1) at a connection point (PL) fixed relative to the support (S), the sonar device (D) being capable of being in a plurality of reception configurations in which the body of the antenna (C) and the support (S) are totally immersed, the antenna body ( C) extending substantially vertically from the first end (E1) to the second end (E2) towards the seabed in at least one reception configuration, the first sonar device comprising orientation adjustment means making it possible to adjust , when the first sonar device (D) is in the operational configuration and the support (S) is fixed with respect to the terrestrial reference, a elevation angle and an azimuth of the second end (E2) in the reference frame linked to the support (S ) centered on the tie point (PL). Sonar system according to any one of Claims 10 to 11, comprising means for adjusting the relative positioning of acoustic transducers of a second reception antenna of the set of antennas. Sonar system according to any one of Claims 10 to 12, comprising a device for adjusting a depth of a third reception antenna of the set of antennas.