EP2126897A1

EP2126897A1 - Mast-mounted sonar

Info

Publication number: EP2126897A1
Application number: EP08708941A
Authority: EP
Inventors: Hervé LE GRAS; Christian Bergogne
Original assignee: Thales SA
Current assignee: Thales SA
Priority date: 2007-02-23
Filing date: 2008-02-13
Publication date: 2009-12-02
Anticipated expiration: 2028-02-13
Also published as: EP2126897B1; FR2913147A1; FR2913147B1; WO2008107270A1; US20100322033A1

Abstract

The present invention relates to the general field of coastal protection and the surveillance of ports. It consists of a deployment device, for a sonar surveillance system, comprising chiefly: an anchoring structure (11), - a support mast (12) designed to be mounted on the structure (11) and arranged on the latter in such a way as to adopt a substantially vertical position, - a platform (13) mounted on the top of the mast (12) and receiving a sonar head (16), - a float (14) fixed to the mast, in proximity to the top, the buoyancy of which is sufficient to keep the mast (12) in the vertical position, when the latter is subjected to the action of movement of the water masses in which it is immersed, the length of the mast (12) is determined in such a way as to position the sonar head (16) at a depth for which the latter exhibits maximum performance in terms of detection range. It applies more particularly to the formulation and deployment of sonar systems, intended to be installed in a fixed position to carry out such protection.

Description

SONAR MONTE ON MAT

FIELD OF THE INVENTION

The present invention relates to the general field of sonar protection of coastal areas and the monitoring of ports. It relates more particularly to a means to ensure, with greater efficiency, the deployment and implementation of sonar systems, installed immersed fixed position, so as to achieve such protection.

BACKGROUND OF THE INVENTION - PRIOR ART

In the problem of coastal surveillance and / or protection of ports, the underwater environment to be monitored generally corresponds to shallow water, although this depth can reach several tens of meters. But it is known that the propagation of sound waves is not rectilinear: their path has a curvature that depends in particular on variations in the speed of sound with depth. Since the sea is not a homogeneous medium, but rather a medium that can present different superimposed layers presenting sudden differences in temperature, the sound waves undergo at the level of the interfaces separating the different layers a modification of their trajectory, which results in a curvature this one.

The intensity of the deviation of the sound wave paths depends on the velocity of the sound in the propagation medium, itself varying with the depth, so that a sound emitted by a sound source will travel a different path depending on the depth at which this source is located. This variation is also different depending on the climatic conditions and in particular the seasons.

The range performance of a sonar is the maximum distance a target can reach so that the sonar that emits an acoustic wave can detect the signal reflected by that target. To determine these performances, performance prediction software tools, parameterized using bathythermic data, are generally used.

The knowledge of the bathythermic readings characteristic of the geographical area makes it possible to determine the temperature gradient in the water column and consequently the sound velocity gradient. This gradient varies mainly according to the geographical position of the measurement and the climatic conditions, in particular the seasons. These readings thus make it possible to determine, for the measurement sites considered, the variation profile, according to the depth, of the propagation velocity of the sound. They also make it possible to establish curves describing, for a given geographical area and as a function of the depth, the paths that can follow the acoustic wave emitted by a source located at a point of the zone. Consequently, if one wishes to set up a sonar monitoring system covering a given area of the seabed, the knowledge of the bathythermic data makes it possible to determine the optimal position of the system.

With regard to permanent installations, the equipment is, in the vast majority of cases, fixed on the sea floor, on a massive support which serves as ballast. Such an implementation obviously does not allow to obtain a maximum range in all geographical / climatic cases and for the different types of sonar (frequency, antenna, ...). In addition, in cases of shallow bottoms, which are those encountered in coastal surveillance, the reverberation, especially that from the bottom, is often preponderant and limits the detection range of the sonar. The latter is strongly related to the position of the transmitter in the water column, optimizing the position of the transmitter in the water column is an effective way to improve the sonar detection range.

PRESENTATION OF THE INVENTION

An object of the invention is to propose a solution making it possible to make better use of bathythermal data, when implementing fixed sonar monitoring systems, intended to provide a safety function. monitoring, in order to maximize the scope of the system, taking into account the propagation of sound.

An advantageous solution for taking advantage of the bathymetric data, and therefore of the more or less advantageous propagation characteristics that the immersion medium can present at a given depth, is to use a sonar placed at a certain distance from the bottom. say placed between two waters at a depth allowing it to offer the best range characteristics.

For this purpose the invention relates to a deployment device for a sonar monitoring system, comprising mainly:

- a massive and heavy anchoring structure intended to be immersed permanently on the bottom

- a mast designed to be mounted on the structure and arranged to adopt a substantially vertical position when mounted thereon,

a platform designed to be mounted on the top of the mast and configured to receive sonar equipment,

a float arranged to be fixed on the mast, close to the top, whose buoyancy is sufficient to maintain the mast in a vertical position, when it is subjected to the action of movements of the water masses in which it is immersed, the length of the mast being determined to position the sonar at a depth at which it provides maximum coverage and range performance.

According to a preferred embodiment, the mast is a telescopic mast whose length is adjustable and comprises remotely controllable adjustment means.

According to another preferred embodiment, which can be combined with the preceding form, the mast comprises means for releasably attaching to the anchoring structure. According to this preferred embodiment, the float has sufficient buoyancy to float the assembly constituted by the mast, the platform and the sonar when the mast is disengaged from the anchoring structure.

According to this preferred embodiment, the system comprises means for towing the disengaged system from the anchoring structure to a selected site having another anchoring structure.

According to a particular embodiment, the float is designed to have variable buoyancy.

The deployment device according to the invention has the advantage of making possible the use of a sonar system having no particular compensation of roll and pitch, but also that of a sonar system having these functions. A sonar intended to be placed on the bottom can therefore be used without modifications.

It also has the advantage of allowing a simple way to move the sonar from one site to another.

It still advantageously makes it possible to simplify the maintenance of the assembly.

The invention also relates to a surveillance system comprising a local sonar transceiver and a remote processing and management system, comprising:

a deployment device according to the invention

a sonar transceiver installed on the platform of the installation device, connecting means for connecting the sonar transceiver to the rest of the monitoring system and supplying the necessary electrical energy to the assembly and the control commands intended for the mast of the device. Such a system has the advantage of providing long-term monitoring (port or coast protection) which remains effective over time, while bathymetric variations with the seasons have a significant impact on the performance of the system. sonar detection

In addition, by making it possible to arrange the sonar heads so as to maximize their range, that is to say between 2 waters and off the coast, the invention also has an interest in terms of overall area coverage. In fact, in order to cover a given area, the implementation of the invention makes it possible to minimize the number of sonar heads by using an omnidirectional coverage in azimuth (see the example illustrated in FIGS. 4 and 5).

DESCRIPTION OF THE FIGURES

The features and advantages of the invention will be better appreciated thanks to the description which follows, description which sets forth the invention through a particular embodiment taken as a non-limiting example and which is based on the appended figures, figures which represent:

FIG. 1, the schematic diagram of the structure of the device according to the invention,

FIG. 2, the block diagram of the structure of a preferred embodiment of the device according to the invention,

FIG. 3, an illustration of a phase of the deployment of a surveillance system comprising the device according to the invention in its preferred embodiment,

- Figures 4 and 5, illustrations relating to an advantageous application of the invention.

DETAILED DESCRIPTION

In its generic form, the device according to the invention comprises, as illustrated in FIG. 1, the following elements:

an anchoring structure 1 1,

a support mast 12, a platform 13, - a float 14

connecting means 15.

The anchoring structure 1 1 has the main characteristic of being a massive element capable of staying at the bottom despite possible movements of water bodies. It is also able to keep all the elements of the device immersed. As such, this structure can have a shape and a constitution variable depending on the case. It can thus, as illustrated in Figure 1, take the form of a concrete block, or any other dense material, placed or anchored on the bottom. It can also for certain particular applications take the form of a metal structure planted at the bottom. In the case of a permanent monitoring system, the support structure is generally installed irremovably.

The support mast 12 has for its function to allow the positioning of the platform 13 at a given depth. Its length h is therefore determined accordingly. It is attached to the anchoring structure substantially vertically. Rigid structure, it is designed and realized, in a known manner, to have a resistance adapted to the bending stresses that may be imposed on it, by the movement of water masses in which it is immersed. Its hydrodynamics and masses are determined in order to maintain a vertical position with an acceptable pitch and roll amplitude for the sonar equipment in terms of mechanical stress, as well as in terms of degradation of sonar detection distance performance, degradation due to pitch and roll of the antenna at the top of the mast. It may for example be constituted by a cylindrical pylon made of composite material or metal. In addition, the mast may be designed to limit its own vibrations due to currents, for example by being equipped with a fairing.

The platform 13 serves to host the sonar head 16 consisting mainly of the antenna, and, depending on the sonar equipment considered, all or part of the electronics of the sonar transceiver of the system. The sonar head is fixed on the platform, preferably removably, by appropriate means, not described herein. The platform 13 is fixedly mounted at the top of the mast 12.

According to the invention, the length h of the support mast 12 is determined from the bathythermic data so that the sonar head 16 placed on the platform 13 is immersed to a depth such that the sonar head has maximum performance in terms of range. detection.

The float 14, in turn has the role of limiting as much as possible the movements of the platform, movements mainly consecutive movements of water bodies such as wave movements or currents. For this purpose, the size (volume and weight) and the material constituting the float are determined in a known manner according to the worst weather conditions that can be encountered on the site. Its buoyancy is determined in particular so that the force that tends to bring it up to the surface advantageously opposes any bending movement of the mast while not exerting excessive force on the fastening means which ensures the fixing of the mast 12 to the anchoring structure. Typically, the buoyancy of the float 14 is calculated so that the angle α taken by the mast, under the action of the external constraints imposed by the movement of the water bodies, can not exceed a few degrees, compared to the vertical, this limit being variable according to the type of sonar used (antenna size, frequency, ...). In this way, compensation of the movements of the platform is not essential for processing the sonar data.

The mast 12 is fixed to the anchoring structure so as to limit the variations of orientation of the sonar head, so that no correction is imperatively required. Nevertheless, it should be noted that, since the mast is free in its pitching and rolling movements, the use of position sensors can improve the overall performance of the system. It makes it possible to evaluate in real time the impact of the variations of the positioning of the sonar head on its detection performances and possibly to correct this impact. The transmission of the sonar information from the sonar head placed on the platform 13 to the deported processing and management organs, for example on the ground, as well as that of the operating commands sent from these same management organs to the sonar head, is This means, of varied nature, may for example consist of an electrical connection cable or an optical cable.

Depending on the applications, these connection means can also be used to supply power to the sonar head 1 6 as well as to the entire device. A cable then provides two-way data links and power from the shore.

The device thus described advantageously makes it possible to position the sonar head at a chosen depth, while ensuring a sufficiently stable position for it so that no particular compensation of the sonar information is necessary because of the movements of the water masses.

In the foregoing description, the device according to the invention is provided with a platform for installing the sonar head. However, in a particular embodiment, the sonar head can be installed at the top of the mast, directly above the float 14 or if it is designed to include an inner housing, inside this float.

The device according to the invention, as described above is an advantageous deployment solution compared to that of placing the sonar head directly on the bottom. This solution advantageously makes it possible to position the sonar head at a depth making it possible, to a certain extent, to optimize the reach of the sonar, the compensation of the movements of the mast by the float 14 making it possible moreover to use an identical sonar head, without any particular system of motion compensation.

This solution can however be improved to obtain the preferred embodiment described in the following document. This preferred embodiment differs from the generic structure illustrated in FIG. 1, in that the device has, as illustrated in FIG. 2, the following characteristics:

a) The support mast is a telescopic mast 21 having means for varying its length.

b) Its attachment to the anchoring structure 1 1 is a removable attachment.

In this preferred embodiment the support mast is constituted by a telescopic tubular structure 21. This structure is set in motion by means for controlling the elongation or contraction. These means not shown in the figure may, in known manner, be mechanical, hydraulic or electrical. They can also be operated remotely from the shore. For this purpose the connecting cable 15 is designed to transmit the corresponding commands of elongation or retraction. Its configuration is further adapted to take these variations into account.

A mast 21 of variable length h is thus available making it possible to position the sonar head 16, fixed at its top, to a depth d that can vary on command, as a function, for example, of climatic or meteorological conditions. For example, the bathythermic conditions being variable over time, particularly according to the seasons, it is advantageously possible with this preferred form of the device according to the invention, to position the sonar head at a depth which allows the moment considered get the maximum reach.

In addition and independently of any bathythermic condition, the implementation of a telescopic mast 21 also makes it possible to arbitrarily position the sonar head 16 at a given depth. This possibility can for example advantageously find its usefulness when the positioning of the sonar head below or beyond a given depth is for example impossible (or otherwise necessary) because of the presence of temporary natural obstacles (schools of fish, algae, etc.).

In this preferred embodiment, the telescopic support mast 21 has the characteristic of being fixed to the anchoring structure removably, by fastening means 22, a universal joint and shackles for example, allowing the mast to pass from a locked state in which it is fixed to the anchoring structure January 1, in an unlocked state where it is completely separated from the anchoring structure January 1.

In an alternative embodiment, these locking means 22 are advantageously remote-operable so that the separation of the support mast 21 from the anchoring structure 11 can be achieved without the intervention of divers on the bottom. This configuration is particularly advantageous when the anchoring structure January 1 is located at a depth unfavorable to human interventions (typically from 30m), which is quite often the case.

In addition to positioning the sonar head at the desired depth, this preferred embodiment has great advantages in terms of maintenance and operation.

As regards the maintenance, and in particular the maintenance of the sonar head, the operations relating to this task can advantageously be simplified by controlling a maximum extension of the telescopic mast 21. In this way, the depth d at which the platform is located 13 supporting the sonar head 16 is decreased, which facilitates for example the intervention of divers responsible for disassembly and possibly replacement of the sonar head. In a particular case, with a mast 21 that can be extended to an appropriate length, it is even conceivable to emerge the platform 13 and make possible a surface intervention.

As regards the exploitation, this preferred form of implementation of the device according to the invention makes it possible to facilitate the deployment of the sonar surveillance system of which the device is a part. Indeed, the fact that the support mast 12 and the elements attached thereto (platform, float and sonar head) can be detached from the anchoring structure 1 1, allows to consider a variable deployment around the area to monitor. To do this, it is sufficient, for example, to position anchoring structures 1 1 by differing selected locations, then to position the sonar head fixed on its support mast vertically to the anchoring structure chosen at a given instant, and finally to immerse the mast and lock it to the anchor structure considered. Then, to achieve a different positioning, it suffices, as shown in Figure 3, to separate the mast 21 of the anchor structure 1 1 considered and let the mast up to the surface on the action of the float 14, then to transport this mast up to the vertical of the point where the anchoring structure is located corresponding to the new positioning of the surveillance system. Thanks to the float 14 which ensures the flotation of the assembly, the mast 21 and the elements attached thereto can be conveyed from one point to another by means of a tow line 31 moored to a means of appropriate mooring 32 built-in device. This mooring means is for example fixed on the platform 13.

To facilitate immersion and emergence operations of the mast, the float of the device according to the invention may also advantageously consist of a variable buoyancy structure, comprising for example ballasts. In this way, the buoyancy of the float 14 can be lowered to facilitate the immersion of the mast for securing, after which it can be reduced to its nominal value, a value sufficient to ensure the rectilinearity and verticality of the mast 21 in operational phase and the floatation of the whole during the transfer phase from one point to another.

Whatever the embodiment implemented, the device according to the invention offers particularly advantageous possibilities in terms of deployment of monitoring systems. Figures 4 and 5 illustrate the advantage of using a device according to the invention to achieve for example a coastal surveillance sonar system. Figure 4 illustrates how one generally deploys a conventional sonar detection system within a bay or harbor. Conventionally the detection system comprises several sonars immersed on the seabed. Each sonar 42 covers an area of the submarine space materialized by an arc 44 more or less complete depending on the surrounding submarine relief. In the measure the depth generally grows from the coast towards the center of the bay one is here forced, the sonars being placed on the bottom, to arrange several sonar close to the coast 41, sonars whose number must be sufficient for that together these sonars can cover the entire bay. We thus obtain a relatively expensive and complex infrastructure to order. The control center 43, generally placed on the ground, thus communicates with the various equipment 42 by means of a network of links 45 all the more important as the number of sonar equipment necessary is greater.

Figure 5 for its part, shows how with the device according to the invention it is advantageously possible to reduce the number of sonar equipment necessary to perform the same monitoring task. As illustrated in FIG. 5, with sonar equipment 51 according to the invention, the sonar head can be immersed between the surface and the bottom, at a depth which makes it possible at the same time not to be hindered by the relief and to pull the best of the bathythermic conditions and to obtain a maximum range materialized by the circle 52 in the figure. In the optimum configuration illustrated in FIG. 5, it is thus possible to cover the zone to be monitored with a single sonar equipment 51 placed no longer on the bottom along the coast 41, but at the bay and at the depth of the more conducive to achieve maximum reach. Advantageously with respect to a solution implementing conventional equipment known from the prior art, the number of equipment deployed (and therefore the maintenance operations) and the quantity of connections 45 needed to connect the deployed at the Center 43. Finally, a simpler, more reliable and more economical structure is obtained. In the preceding paragraphs, the deployment device according to the invention is described in the context of the implementation with a sonar head. It is obvious that such an implementation context is neither exhaustive nor limiting. The device according to the invention can be implemented in any other neighboring area where it is necessary or at least advantageous to maintain a submerged equipment at a given depth.

Claims

Deployment device, for a sonar monitoring system, comprising mainly:

- A massive and heavy anchoring structure (1 1) intended to be immersed permanently on the bottom - a support mast (12) designed to be mounted on the structure

(1 1) and arranged to adopt a substantially vertical position when mounted thereon,

- A platform (13) designed to be mounted on the top of the mast (12) and configured to receive a sonar head (16), characterized in that it further comprises a float (14) arranged to be fixed on the mast , close to the summit, whose buoyancy is sufficient to maintain the mast (12) in a vertical position, when it is subjected to the action of movements of the bodies of water in which it is immersed, the length of the mast ( 12) being determined so as to position the sonar head (16) at a defined depth.

2. Device according to claim 1, wherein the support mast (12) comprises a fairing for limiting vibration.

3. Device according to one of claims 1 or 2, wherein the support mast is a telescopic mast (21) whose length h is adjustable and comprises remotely controllable adjustment means.

4. Device according to one of claims 1 to 3, wherein the support mast (21) comprises means (22) for releasably attaching to the anchoring structure (1 1).

5. Device according to claim 4, wherein the float (14) has a buoyancy sufficient to float the assembly constituted by the support mast (21), the platform (13) and sonar (1 6) when the mast (21). ) is disengaged from the anchoring structure (1 1).

6. Device according to claim 5 further comprising means (32) allowing when the mast (12) is disengaged from the anchoring structure (1 1) to tow the assembly constituted by the support mast (12), the platform (13) and the sonar head (1 6) to a selected site having another anchor structure.

7. Device according to any one of claims 4 to 6, wherein the float (14) is designed to have a variable buoyancy.

8. Sonar monitoring system characterized in that it comprises:

a deployment device according to any one of claims 1 to 7,

a sonar head (1 6) mounted on the deployment device,

- a remote processing and management system,

the deployment device comprising connecting means (15) for connecting the sonar head to the rest of the monitoring system, supplying the necessary electrical energy to the assembly and sending the control commands for the mast (12, 21) of the device.