GB2620480A

GB2620480A - A hull-mounted sonar assembly

Info

Publication number: GB2620480A
Application number: GB2306613.7A
Authority: GB
Inventors: Wood Trevor; Cleaver Samuel; Stubbs Paul
Original assignee: Ultra Electronics Ltd
Current assignee: Ultra Electronics Ltd
Priority date: 2022-05-04
Filing date: 2023-05-04
Publication date: 2024-01-10
Also published as: GB202306613D0; GB202206512D0

Abstract

A hull-mounted sonar assembly 5 comprising a central housing 20 and a sonar array 10, the sonar array 10 comprising a plurality of digital array modules 12 arranged around a perimeter of the central housing 20, each digital array module 12 comprising a plurality of active transducer block modules 22, each active transducer block module 22 comprising a plurality of active transducers 16 arranged in multiple vertical columns 11, the active transducers 16 configured to receive a signal reflected from an underwater object. The transducer modules 22 and transducers 16 preferably being independently sampleable. The arrangement preferably including passive transducers which are also independently sampleable, the transducers preferably provided between adjacent active transducer block modules.

Description

A Hull-Mounted Sonar Assembly The present invention relates to hull-mounted sonar assembly, and a sonar system including a ship and a sonar assembly, and a method of determining information about an underwater object using a hull-mounted sonar assembly.

Sonar assemblies include arrays which comprise sonar equipment, typically active and/or passive transducers, which once activated, either remotely or after a predetermined time, receive acoustic signals which are sent to a processor on a ship for further processing, for example, to determine information such as positional or classification information of underwater objects such as submarines. Active transducers transmit signals which are then received after reflecting off the underwater object, whereas passive transducers receive the signals generated by the underwater object itself, typically sound.

Sonar arrays can be incorporated into buoys (sonobuoys), towed behind ships (towed arrays), or in the case of the present invention, mounted on the hulls of ships (hull-mounted sonar arrays).

In known hull-mounted sonar arrays, the transducers are arranged in vertical columns. The sonar array itself comprises multiple vertical columns arranged circumferentially around a barrel-like housing. In each column, the transducers are either individually electrically connected to a processor inboard the ship or connected to each other and then electrically connected to a processor inboard the ship. The processor inboard the ship processes the acoustic signals received to determine information about the underwater object.

One disadvantage of known hull-mounted sonar arrays is that the transducer electronics including power amplifiers can require substantial space and cooling capacity within the ship to drive and acquire from the sonar array transducers. Further, the significant amount of wiring to either each vertical column of the sonar array or individual transducers presents electromagnetic compatibility, weight and maintainability challenges.

An object of the present invention is to provide a hull-mounted sonar assembly which overcomes or at least mitigates the disadvantages of known hull-mounted sonar assemblies.

According to the present invention there is provided a hull-mounted sonar assembly comprising a central housing and a sonar array, the sonar array comprising a plurality of digital array modules (DAMs) arranged around a perimeter of the central housing, each digital array module comprising a plurality of active transducer block modules, each active transducer block module comprising a plurality of active transducers arranged in multiple vertical columns, the active transducers configured to receive a signal reflected from an underwater object.

Providing the transducers within a DAM enables easier assembly, and in contrast to prior art hull-mounted sonar assemblies in which the transducers are electrically connected to each other, the use of the DAM enables fewer connections.

Preferably, each active transducer block module is independently sampleable. Preferably, each active transducer is independently sampleable.

Preferably, the multiple vertical columns are parallel to each other.

Preferably, each active transducer block module comprises four active transducers arranged in a two-by-two matrix. By arranging the active transducers in such blocks, the acoustic efficiency is increased as the two-by-two matrix tends to look like a transducer of double the size, thereby moving the reactive mass loading to below the useful band, such that the power is radiated rather than expended in accelerating a larger slug of water attached to the piston face of the transducer. This arrangement is counter to known hull-mounted sonar arrays and achieves higher performance for a given size, whilst allowing for space between the active transducer block modules.

Preferably, each digital array module comprises multiple, for example, three active transducer block modules.

Preferably, each digital array module comprises two vertical columns of the multiple vertical columns.

Preferably, the plurality of digital array modules further comprises a plurality of passive transducers, in which each passive transducer is independently sampleable.

Preferably, at least one transducer, more preferably two transducers of the plurality of passive transducers is provided vertically between adjacent active transducer block modules in at least one, preferably all of the multiple vertical columns.

Preferably, each of the plurality of digital array modules further comprises transducer electronics configured to control the transmission and/or reception of signals to and from the active and/or passive transducers Advantageously, sampling the received signal from each transducer near the transducer improves the signal-to-noise ratio. Further, aggregating sample data from the transducers into a combined data stream significantly reduces external cabling overhead.

Preferably, the transducer electronics includes at least one power amplifier.

Preferably, each active transducer block module is driven by a single power amplifier of the at least one power amplifier. Advantageously this allows considerably more flexibility in the transmission control for the sonar array as the power amplifiers can be controlled individually to steer the acoustic beams vertically. A typical hull-mounted sonar would have one power amplifier driving multiple vertical columns or staves, which would not provide for vertical steering capability.

Preferably, each power amplifier associated with each active transducer block module is configured to be independently controllable relative to the other power amplifiers associated with each active transducer block module.

Preferably, each digital array module comprises a main body with an oil filled internal cavity within which the transducer electronics are housed.

Preferably, the main body comprises openings within which the active and passive transducers are at least partially housed.

Preferably, each of the plurality of digital array modules is individually connected to a ship-housed processing electronics by a single cable assembly, in which the cable conduit includes data and power cables, preferably the data cable is a fibre optic cable.

Preferably, the digital array modules are distributed substantially evenly horizontally and/or substantially evenly vertically around the perimeter of the central housing.

Preferably, the passive transducers are substantially evenly horizontally and/or substantially evenly vertically distributed around the perimeter of the central housing.

Preferably, the active transducer block modules are substantially evenly horizontally and/or substantially evenly vertically distributed around the perimeter of the central housing.

The performance of the active transducers is maximised by placing them as close as possible to each other, most preferably vertically and horizontally. For the best passive performance, the passive transducers need to be distributed evenly around the central housing, both vertically and horizontally. To optimise both active and passive transducer performance, the passive transducers are provided vertically between the active transducer block modules. This arrangement enables even vertical and horizontal distribution of the passive transducers whilst maintaining the active transducers as close as possible to each other in their active transducer block module arrangement.

Preferably, the sonar assembly is part of a sonar system which includes a ship comprising an inboard processor and the sonar assembly is mounted on a hull of the ship.

Preferably, the inboard processor is configured to process signals received by the transducers to determine information about the underwater object.

Preferably, the transducer electronics are remote from the ship.

The inclusion of the transmit and receive electronics within the DAM significantly reduces the footprint of the electronics required on the ship, compared to a traditional sonar array where additional cabinets are required for transmit and receive functions. The modularisation of the sonar assembly into DAMs enables a single connection for each DAM to be made, rather than individual connections for each transducer, reducing the number of connections by a factor of approximately thirty and increasing the reliability of the system. The use of a fibre optic cable minimises the potential for electro-magnetic interference.

Oil filling the cavity of the DAM allows for efficient transfer of heat from the electronics to the body of the DAM and then to the sea water. The oil also facilitates the survival of the electronics to a high level in-water shock pulses from underwater explosions, as it eliminates any material-to-air boundaries where the accelerating forces from the shock pulse would be amplified to a level that the electronics would likely be damaged. As a result of the oil filling, the DAM is fully pressure-balanced so that volume changes in the oil due to variations in temperature do not induce any pressure on the DAM seals, thereby minimising the potential for any leaks.

The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a side schematic view of a sonar system including a ship and a hull-mounted sonar assembly according to the present invention, Figure 2 is a perspective view of the hull-mounted sonar assembly of Figure 1, Figure 3 is an exploded perspective view of a digital array module of the hull-mounted sonar assembly of Figure 1, Figures 4 and 5 are front views of part of the stave of the hull-mounted sonar assembly of Figure 1, Figures 6 is a schematic view of the hull-mounted sonar assembly transmit and receive architecture, Figure 7 is a simplified view of the digital array module receive circuitry, and Figure 8 is a simplified view of the digital array module transmit circuitry.

In Figure 1, a sonar system 200 comprises a ship 100 including a sonar dome 90, inside which, a sonar assembly 5 is housed. The sonar dome 90 is acoustically transparent so as to enable the transmission and reception of acoustic signals as will be described below.

The ship 100 further includes inboard processing electronics 130 comprising an interface cabinet which includes an array interface module (AIM)140, a sonar console 120, processing software 150 and a remote panel 125.

In Figures 2 to 5, the sonar assembly 5 comprises a sonar array 10 and a cylindrical central housing 20 onto which are mounted multiple, in this embodiment, twenty-two digital array modules (DAMs) 12. The DAMs 12 are distributed substantially equally around a circumference of the cylindrical central housing 20.

In Figure 3, each DAM 12 comprises a main body 26 with cylindrical openings 28 and rectangular openings 29 located therein. A rear cover 30 seals against the main body 26 to provide a cavity 32. An oil-tight seal 34 is provided between the rear cover 30 and the main body 26.

Each DAM 12 further includes transducer electronics 36 which includes power amplifiers 24, a main circuit board 38 comprising the electronics to operate the DAM, matching assemblies 40 and an electromagnetic compatibility (EMC) filter assembly 42.

The cavity 32 comprises a bladder assembly 44 and a baffle 46 which prevents the bladder assembly 44 from coming into contact with the main circuit board 38.

In Figures 4 and 5, each DAM 12 comprises multiple, in this embodiment, two vertical columns or staves 11 of active 16 and passive 14 transducers. The active transducers 16 are of the Tonpilz type and are provided in groups of four in an active transducer block module 22.

Each DAM 12 includes, for example, five active transducer block modules 22 arranged vertically. Optionally, a pair of passive transducers 14 are provided between each of the active transducer block modules 22 with one passive transducer 14 of each pair arranged in each column 11. Where passive transducers are provided as part of the array, additional passive transducers are provided above the uppermost active transducer block module 22, and below the lower active transducer block module. The passive transducers 14 are not shown in Figure 2.

It can be seen from Figure 3 that each active transducer 16 locates partially inside each cylindrical opening 28. It can be further seen that each pair of transducers 14 locates partially inside each rectangular opening 29 such that the passive transducers 14 are arranged between each active transducer block module 22.

An underwater connector 48 is provided at one end of each DAM 12. Copper power and fibre-optic data lines (not shown) are connected to the underwater connector 48 of each DAM 12, with each DAM 12 connected to the ship 100 via a single cable assembly 160. In one embodiment, the single cable assembly comprises three cables bundled together, two of which include the copper power lines to each DAM, the other includes fibre optic lines to transmit data to and from each DAM 12.

It can be seen from Figure 3 that in this embodiment there are five power amplifiers 24 and five active transducer block modules 22, that is, each active transducer block module 22 is associated with, and driven by, a single power amplifier 24. In alternative embodiments, the number of power amplifiers and active transducer block modules need not be five.

In Figures 7 to 8, the architecture of the sonar array 10 is shown, and will be referenced in the operation discussion below.

In Figure 7, further detail of the transducer electronics 36 is provided from a receive perspective. In addition to details provided in support of Figure 6, it can be seen that two optical transceivers are used per digital array module 12. The optical transceivers each connect to a transmit (Tx) and receive (Rx) buffer which then connect into either FPGA A or C. It can be seen that FPGA B and D connect to a Ferroelectric RAM (FRAM) module, which provides storage for auxiliary data. FPGA B and D also connect to an Inertial Measurement Unit (IMU), which provides 6-axis accelerometer and gyroscopic data which can be used by the inboard processing electronics 30 to stabilise the acoustic data. It can be seen that multiple temperature sensors in the unit are sampled by an ADC which can be used for reliability monitoring.

In Figure 8, further detail of the transducer electronics 36 is provided from a transmit perspective. In addition to the details provided in support of Figure 6 and Figure 7, it can be seen that each FPGA on the main circuit board 38 connects to one or more power amplifiers 24. Each power amplifier 24 contains an FPGA which controls modulation of the output through the drive circuitry. The drive circuit then connects to a matching transformer 40 and finally, to the active transducer block module 22. A Tx/Rx switch is also connected to each FPGA to enable switching the active transducer block module 22 between transmit or receive configurations.

The sonar array 10 operates as follows: The principle of operation of the sonar array 10 of the present invention is similar to known sonar arrays in that the passive transducers 14 only receive acoustic signals generated from underwater objects (not shown) that are being detected, and the active transducers 16 both transmit an acoustic signal in the form of a sound pulse or ping, and then listen for reflections from the underwater objects.

The software 150 sends transmission data as a time series digitised representation of the actual waveform to be transmitted by each power amplifier 24, to an Array Interface Module 140 The Array Interface Module 140 takes the transmission data and creates the individual transmission data for each of the power amplifiers in each of the twenty two DAMs 12.

The Array Interface Module 140 synchronously transfers the transmission data to each DAM 12 via the fibre optic data connections.

The transducer electronics 36 distribute the transmission data between the five power amplifiers 24. The data sent to each power amplifier 24 is completely independent from all the other power amplifiers 24 and DAMs 12.

The power amplifiers 24, and as shown in Figure 8, drive each of the four active transducers 16 in their respective active transducer block modules 22, through matching circuitry and in phase using the high voltage power received from the Array Interface Module 140.

The transducers 16 then transform the electrical transmit signal into an underwater acoustic signal.

After transmission of the acoustic signal, the active 16 and passive 14 transducers receive the acoustic signal reflected from the underwater object and transform the received signal into an electrical signal. As shown in Figure 7, this electronic signal is then fed into a pre-amp circuit which includes band pass filtering (f).

Analogue to Digital converters (ADCs) in the DAMs 12 sample the electrical signals from each pre-amp and produce digital time series reception data.

This reception data is then aggregated by multiple field-programmable gate arrays (FPGAs A-D) into a single stream of data. FPGAs A and C, shown in Figure 7, transmit duplicate copies of the data stream to the Array Interface Module (140) via the fibre optic connections.

The Array Interface Module 140 receives synchronised transducer data from all twenty-two DAMs 12, collates the data and forwards to the software processing applications which then determine positional and classification information about the underwater object.

It will be appreciated that the sonar array of the present invention enables improved information to be determined about underwater objects, through improved signal-to-noise ratio, compared to prior art sonar arrays, as well as providing the arrays in a modular system which reduces the amount of physical space required on board the ship due to the fact some of the transmission and reception of signals previously process on board the ship is conducted at the array assembly.

It will be understood that the distribution of power amplifiers in the DAMs, with each power amplifier being able to be independently controlled, gives significantly more flexibility in the transmissions. Having each active transducer block module independently controllable allows the transmitted signals to be steered in either the vertical or horizontal plane and focused as required, or for multiple different signals to be transmitted from the array at the same time. This allows the transmission beam to be steered up or down to dynamically stabilise the beam patterns for ships motion, or to allow a focused beam to be directed at much higher level of precision compared to prior art sonar arrays.

It will be further understood that whilst each power amplifier drives a block of four active transducers in the active transducer block module, the received signals from each transducer are individually or independently received and sampled. By sampling each transducer individually, the resolution of the reception angles is improved compared to sampling a block of four transducers. It will be understood that the above described system utilises both passive and active transducers. In alternative embodiments, either passive or active transducers can be used depending on the type of information required.

Claims

CLAIMS1 A hull-mounted sonar assembly (5) comprising a central housing (20) and a sonar array (10), the sonar array (10) comprising a plurality of digital array modules (12) arranged around a perimeter of the central housing (20), each digital array module (12) comprising a plurality of active transducer block modules (22), each active transducer block module (22) comprising a plurality of active transducers (16) arranged in multiple vertical columns (11), the active transducers (16) configured to receive a signal reflected from an underwater object.
2. A hull-mounted sonar assembly (5) according to claim 1 in which each active transducer block module (22) is independently sampleable.
3. A hull-mounted sonar assembly (5) according to any claim 1 or 2 in which each active transducer (16) is independently sampleable.
4. A hull-mounted sonar assembly (5) according to any preceding claim in which the multiple vertical columns (11) are parallel to each other.
A hull-mounted sonar assembly (5) according to any preceding claim in which each active transducer block module (22) comprises four active transducers (16) arranged in a two-by-two matrix.
6. A hull-mounted sonar assembly (5) according to any preceding claim in which each digital array module (12) comprises multiple, preferably three active transducer block modules (22).
7. A hull-mounted sonar assembly (5) according to any preceding claim in which each digital array module (12) comprises two vertical columns of the multiple vertical columns (11).
8. A hull-mounted sonar assembly (105 according to any preceding claim in which the plurality of digital array modules (12) further comprises a plurality of passive transducers (14), in which each passive transducer (14) is independently sampleable.
9 A hull-mounted sonar assembly (5) according to claim 8 in which at least one transducer (14), preferably two transducers (14) of the plurality of passive transducers (14) is provided vertically between adjacent active transducer block modules (22) in at least one, preferably all of the multiple vertical columns (11).
10.A hull-mounted sonar assembly (5) according to any preceding claim in which each of the plurality of digital array modules (12) further comprises transducer electronics (36) configured to control the transmission and/or reception of signals to and from the active (16) and or passive (14) transducers.
11.A hull-mounted sonar assembly (5) according to claim 10 in which the transducer electronics (36) includes at least one power amplifier (24).
12.A hull-mounted sonar assembly (5) according to claim 11 in which each active transducer block module (22) is driven by a single power amplifier (24) of the at least one power amplifier (24).
13.A hull mounted sonar assembly (5) according to claim 12 in which each power amplifier (24) associated with each active transducer block module (22) can be controlled independently relative to the other power amplifiers (24) associated with other active transducer block modules (22).
14.A hull-mounted sonar assembly (5) according to any preceding claim in which each digital array module (12) comprises a main body (26) with an oil filled internal cavity within which a or the transducer electronics (36) are housed.
15.A hull-mounted sonar assembly (5) according to claim 14 in which the main body (26) comprises openings within which the active (16) and passive (14) transducers are at least partially housed.
16.A hull-mounted sonar assembly (10) according to any preceding claim, each of the plurality of digital array modules (12) is individually connected to a ship-housed processing electronics (130) by a connector (48), in which the connector (48) includes data and power lines, preferably the data line is fibre optic.
17. hull-mounted sonar assembly (10) according to claim 16 in which each connector (48) each of the plurality of digital array modules (12) is individually connected to a ship-housed processing electronics (130) by a single cable assembly (160).
18.A hull-mounted sonar assembly (5) according to any preceding claim in which each of the digital array modules (12) are distributed substantially evenly horizontally and/or substantially evenly vertically around the perimeter of the central housing (20).
19 A hull-mounted sonar assembly (5) according to any preceding claim in which a or the passive transducers (14) are substantially evenly horizontally and/or substantially evenly vertically distributed around the perimeter of the central housing (20).
20.A hull-mounted sonar assembly (5) according to any preceding claim in which the active transducer block modules (22) are substantially evenly horizontally and/or substantially evenly vertically distributed around the perimeter of the central housing (20).
21.A sonar system (200) including a ship (90) comprising inboard processing electronics (130) and a hull-mounted sonar assembly (5) according to any preceding claim, in which the inboard processing electronics (130) is configured to process signals received by the transducers (14,16) to determine information about the underwater object.
22.A sonar system (200) according to claim 21 when dependent on claim 10 in which the transducer electronics (36) are remote from the ship (90).
23.A sonar system (200) according to claim 22 in which the transducer electronics (36) and the inboard processing electronics (130) are separate.