Sonar localisation

(54) Title: Sonar location (56) Publications cited: - (47) Abstract:

Herein is disclosed a sonar localization device comprising a plurality of acoustic transducers (6) arranged to define at least two end-radiating sets (2, 4), each producing a sonar beam (10, 12) suitable for detecting objects. within the immediate area. The radiating sets form an angled gap between the longitudinal axes of the jets. The angled gap between the jets allows the angular position determination of objects located at a distance substantially smaller than the maximum width of the jets through the remote area.

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SUMMARY

Herein is disclosed a sonar localization device, which comprises a plurality of acoustic transducers (6) arranged to define at least two terminal radiation sets (2, 4), each producing a sonar beam (10, 12) suitable for detecting objects in the immediate area. The radiating sets form an angled gap between the longitudinal axes of the jets. The angled gap between the jets allows angle positioning of objects located at a distance substantially smaller than the maximum width of the jets given the remote area.

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The present invention relates to the sonar region and specifically to the use of endfire arrays for the location of objects immersed in a liquid.

Techniques for sonar localization according to the prior art usually rely on the ability of a converter to generate circular acoustic signals, the reflections of which are received and processed so as to provide the location of objects with respect to both direction and distance.

Typically, sets of transducers are used, and acoustic signals can, with the aid of what is known to those skilled in the art as electronic beam forming, which uses, for example, a phase-controlled set of transducers, be directed or directed to areas of interest. In terms of ship elites submarine sonar systems, the term latitude or plane set is used to define a set of transducer elements arranged on the side of the vessel in question.

When using sets of sonar converters, the ability to accurately determine received signals for directional and distance information depends on the configuration of the elements of the set itself, along with the processing capacity of the sonar system in question. However, as an object's distance from a sonar set decreases, the ability to determine information is significantly impaired due to the relationship of the interrelationship of the beam patterns formed by a latitude or plane set.

Normally, in a plane set, beam overlap occurs from a set of transducers in the order of 3 decibels downstream from the set of planes.

530 480 at which point the angle between the beams is approximately equal to the beam width.

In sonar applications where accurate location of objects at short distances is required, handheld systems according to the present state of the art are functionally limited to areas determined by what is known to those skilled in the art as near-field effects. Such effects limit the effective range of such devices to the order of a few meters from the object, and usually such devices are used as secondary locators, the primary accurate location being performed manually or visually.

A specific form of acoustic set known as end-emitting set has the ability to form beams of acoustic signals with in the vicinity, that is, up to and including the position of the last converter. A discussion of near-field effects of such a device can be found in the reference HO Berktay and JA Shooter: Nearfield Effects in Endfire Arrays, J.Acoust. Soc. Am., 53 (2), 550-556.

The invention described herein provides a device and method for using the properties of end-beam sets to form a sonar-based locating system, which allows the determination of distant objects substantially closer to the set than previously possible without any deterioration of the system. remote area.

According to one aspect of the present invention there is provided a device for locating objects immersed in a liquid, which device comprises a plurality of acoustic transducers which are arranged in relation to each other such that they define at least two radiating sets, the physical relationship of said at least two end-radiating sets form an angled gap between the longitudinal axes of the acoustic rays formed by said end-radiating sets; and the angled gap between said beams allows for angular positioning of objects located at a distance from the end of said radiant set, which distance is substantially smaller than the maximum width of said beams in the remote region.

In a preferred embodiment of the invention, said transducers comprise circular transducers.

In yet another embodiment of the invention, the characteristics of the radiation patterns from each of the end-radiation sets are essentially identical.

In yet another embodiment of the invention, the jets from each of the end-radiating sets are substantially symmetrical about the line of sight.

In another further embodiment of the invention, the angle between the jets of each of the end-beam sets is substantially equal to the width of the resulting beam.

In accordance with further aspects of the present invention, the disclosed device may be included in a waterborne vessel, an underwater vessel or a hand held device.

In accordance with another aspect of the present invention, there is provided a method for accomplishing the location of objects immersed in a liquid, comprising the steps of:

(a) arranging a plurality of acoustic transducers in relation to each other, defining at least two radiant sets, and

b) forming an angled gap between the longitudinal axes of the acoustic beams formed by said end-beam devices, in accordance with the physical ratio of said at least two end-beam sets, said angular gap between said beams permitting angular position determination of objects spaced from said beam the end of the radiant sets, which are substantially smaller than the maximum width of said rays through the remote region.

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The invention discussed herein uses the beam characteristics of two or more end-radiation sets to measure the location of a target object from very close to the set and through the remote region.

An example of a preferred embodiment of the invention is now given, by way of example only, with reference to the accompanying drawing, namely Fig. 1, which shows a schematic representation of a pair of end-beam sets, and their associated acoustic beam patterns used in the present invention. in accordance with the invention.

Fig. 1 shows a pair of end beam sets 2, 4, each consisting of a plurality of acoustic transducers 6, each of said acoustic transducers being arranged in a matrix material 8.

The function of the transducers is controlled by the control means 9, which can be used to control characteristics such as frequency, power and duration, together with the ability to process signals received by transducers used in reception mode and not transmission mode.

In order to provide the new ability to provide distance information in the vicinity of a pair of the ends of the sets 2, 4 of the invention used according to the invention, it is preferred that the angle between the rays 10, 12 of the respective sets 2, 4 is substantially equal to the width of the beam thus formed. This provides the ability to form a beam pattern that allows accurate, undisturbed determination of received sonar information regarding a target object.

Such a sonar device may be included in a hand-held system for underwater use in the vicinity of target objects, or alternatively as part of a remotely controlled or automated system for investigating objects underwater, including such objects lying on, or buried under the seabed.

The longitudinal axis along which the beams are directed within the sonar location range is referred to as line of sight 14, i.e., the direction of sight of the sonar beam.

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Other advantages and improvements over the prior art sisters will be apparent only to those skilled in the art, and such embodiments and alternative embodiments utilizing the inventive concept disclosed herein are considered to be within the scope of the invention as defined by the appended claims.

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