System for detecting and locating submerged objects having neutral buoyancy such as moored mines and associated method

Patent metadata

Field	Value
Publication number	US-10353059-B2
Application number	US-201415021636-A
Country	US
Kind code	B2
Filing date	Sep 10, 2014
Priority date	Sep 13, 2013
Publication date	Jul 16, 2019
Grant date	Jul 16, 2019

Abstract

A system for detecting and locating submerged underwater objects having neutral buoyancy comprising mechanically steered sonar to image the water column comprises mechanically steered sonar with a single emission channel, to perform the insonification of a first individual sector in a first pointing direction by a single first acoustic pulse, the sonar forming a single reception channel suitable for acquiring a first acoustic signal resulting from insonification, the mechanically steered sonar being mounted on a carrier to advance in a main direction, the first pointing direction substantially lateral to the carrier and the first individual sector exhibits a wide relative bearing aperture and a narrow elevation aperture, the mechanically steered sonar comprising a mechanical pointing device to tilt the first pointing direction about an axis of rotation substantially parallel to the main direction allowing the sonar to acquire first acoustic signals resulting from insonifications performed in different pointing directions.

First claim

The invention claimed is:

1. An imaging system comprising:
an assembly comprising at least one mechanically steered sonar mounted on a carrier, such that a pointing direction of the at least one mechanically steered sonar is substantially lateral to a main direction of the carrier, the main direction of the carrier being a longitudinal direction of the carrier along which the carrier is intended to advance, and such that the at least one mechanically steered sonar is configured to conduct sonar acquisition of an individual sector having a first bearing aperture and a first elevation aperture, the first elevation aperture being narrower than the first bearing aperture, wherein
the at least one mechanically steered sonar comprising:
a mechanical pointing device configured to tilt the pointing direction of the at least one mechanically steered sonar about an axis of rotation, the axis of rotation being substantially parallel to the main direction of the carrier,
a single emission channel to emit acoustic pulses in the pointing direction of the at least one mechanically steered sonar, and
a single reception channel to acquire acoustic signals resulting from some of the acoustic pulses.

2. The imaging system of claim 1 , further comprising a processing unit configured to locate underwater objects having neutral buoyancy from at least one of the acoustic signals.

3. The imaging system of claim 1 , wherein
the at least one mechanically steered sonar of the assembly comprising a plurality of mechanically steered sonars, and
the plurality of mechanically steered sonars are spaced apart in the main direction of the carrier and are mounted on the carrier such that the pointing direction of each mechanically steered sonar of the plurality of mechanically steered sonars of the assembly is directed toward a same side of a vertical plane passing through the main direction of the carrier.

4. The imaging system of claim 1 , further comprising:
at least one side-scan sonar to image a seabed in a pointing direction of the side-scan sonar in an individual sector, the individual sector including a second bearing aperture and a second elevation aperture, the second elevation aperture being narrower than the second bearing aperture, the at least one side-scan sonar comprising a plurality of relative bearing reception channels mounted on the carrier such that the pointing direction of the side-scan sonar is oriented substantially laterally to the main direction of the carrier on a same side of a vertical plane passing through the main direction of the carrier as the pointing direction of the at least one mechanically steered sonar and as the pointing direction of the side-scan sonar, and
a human-machine interface comprising a display device to simultaneously display a first sonar image, representing the acoustic signals, and a second sonar image, representing other acoustic signals acquired by the at least one side-scan sonar during a same period of acquisition as the acoustic signals, to enable visual identification, on the first sonar image of a first echo generated by a submerged object having neutral buoyancy, and on the second sonar image, a second echo, generated by an object placed on the seabed substantially directly below the submerged object.

5. The imaging system of claim 4 , wherein the display device is configured such that the first sonar image and the second sonar image displayed have substantially identical sizes and such that a first echo included in the first sonar image and a second echo included in the second sonar image reflected by respective objects situated at a same distance from the at least one mechanically steered sonar and respectively from the side-scan sonar and resulting from acoustic pulses emitted simultaneously by the at least one mechanically steered sonar and by the at least one side sonar are represented substantially at a same abscissa and at a same ordinate on the first sonar image and on the second sonar image.

6. The imaging system of claim 4 , wherein the human-machine interface comprises a tracker allowing an operator to simultaneously move two cursors displayed by the display device, one on the first sonar image and the other on the second sonar image, the display device being configured such that the two cursors occupy, on the first and the second sonar image, positions corresponding to a same geographic position in a terrestrial reference frame.

7. The imaging system of claim 6 , wherein the cursor displayed on the first sonar image is provided with a curve representing a set of the possible positions on the first sonar image of echoes originating from an object having created an echo represented at the position pointed to by the cursor.

8. The imaging system of claim 4 , wherein the first sonar image and the second sonar image echoes in an instant mode of emission of acoustic pulse originating the acoustic signals and respectively the other acoustic signals/distance separating a fixed point in the horizontal plane, from objects originating the echoes, and being included in said acoustic signals and respectively other acoustic signals.

9. The imaging system of claim 4 , comprising a processing unit configured to identify a first echo originating from a submerged object having neutral buoyancy using at least one of the acoustic signals, the display device being configured so as to display, superimposed with the first sonar image and/or the second sonar image, symbols at positions occupied by the submerged object.

10. The imaging system of claim 4 , wherein said human-machine interface comprises a classification unit configured so as to allow an operator to classify first echoes visible on the first sonar image or symbols visible on the first sonar image and representative of echoes detected by a processing unit in classes comprising a moored mine class and a free floating object class.

11. The imaging system as claimed in claim 1 , said system being configured to realize a plurality of scanning steps while the carrier advances along the main direction, each scanning step comprising:
pointing the pointing direction, substantially lateral to the main direction, in successive elementary directions included in a sector to be imaged, via the at least one mechanical pointing device,
emitting an acoustic pulse in each of the elementary directions via the single emission channel; and
acquiring an acoustic signal, resulting from the acoustic pulse, via the single reception channel.

12. The imaging system of claim 11 , wherein the scanning step further comprises acquiring a plurality of acoustic signals generated by an object and resulting from a plurality of the acoustic pulses, the object being fixed in the terrestrial reference frame and located at a depth lying between a predetermined minimum depth and a predetermined maximum depth, and located at right angles to the main direction D in a horizontal plane at a distance from the at least one mechanically steered sonar greater than a predetermined minimum range and less than a predetermined maximum range.

13. The imaging system of claim 11 , wherein said system is configured to:
detect echoes created by submerged objects having neutral buoyancy via first signals, comprising verifying if the acoustic signal satisfies a predetermined selection criterion; and
locate submerged objects having neutral buoyancy from the first acoustic signals acquired in the scanning step and from detected echoes.

14. The imaging system according to claim 1 , further comprising the carrier.

15. A imaging method comprising a plurality of scanning steps while a carrier advanc

Assignees

• Thales Sa

Inventors

• Mandelert Nicolas
• Guthmann Pierre

Classifications

• G01S15/8902

  Side-looking sonar · CPC title

• B63G2007/005

  Unmanned autonomously operating mine sweeping vessels · CPC title

• B63G7/08

  of acoustic type · CPC title

• G01S15/42

  Simultaneous measurement of distance and other co-ordinates (indirect measurement G01S15/46) · CPC title

• G01S7/6281

  Composite displays, e.g. split-screen, multiple images · CPC title