High-resolution underwater target exploration system

Abstract

The utility model relates to a high-resolution underwater target exploration system which comprises a workboat and a tow fish. The workboat is used for dragging the towed fish; transducer arrays are respectively mounted on the left and right sides of the tow fish; the transducer array comprises a transmitting array, a plurality of preamplifiers and a receiving array; the transmitting array is arranged on the front side of the sailing direction, the receiving arrays are arranged on the rear side of the sailing direction, and the receiving arrays and the transmitting array are arranged on the same axis; the number of the pre-amplifiers is matched with that of the receiving arrays, and the pre-amplifiers are arranged beside the receiving arrays of the corresponding channels. According to the high-resolution underwater target exploration system provided by the utility model, because the size of the towfish is small, the towfish can be manually laid, and a winch, a large A-shaped frame or a gantry crane is not needed; as the tow fish adopts a tow mode, the tow fish is not influenced by the posture of the ship; as the aperture of the sonar is smaller, the imaging resolution is higher.

Description

Technical Field

[0001] This utility model relates to the field of underwater exploration technology, and in particular to a high-resolution underwater target detection system. Background Technology

[0002] Underwater target detection is widely used in port inspection, waterway dredging, and subsea pipeline inspection. Different detection methods are employed depending on the specific application requirements. Underwater target imaging, with its ability to acquire rich target information, is the primary means of underwater target detection. The richer the target information, the easier it is for target identification and analysis. The most commonly used underwater target imaging method is imaging sonar. Traditional imaging sonar is mainly side-scan sonar, and the main factor determining the image quality of side-scan sonar is the resolution along the navigation direction. This resolution is determined by the width of the horizontal beamwidth; as the detection distance increases, the directional resolution decreases, which is detrimental to image analysis of distant targets.

[0003] Synthetic aperture sonar technology has an azimuth spatial resolution that is independent of the detection range and can maintain a constant resolution within the detection range. Compared with traditional side-scan sonar imaging technology, it is more suitable for high-resolution underwater target and seabed topography detection.

[0004] There are two main operational modes for existing synthetic aperture sonar: towed and side-mounted. Due to the large size and weight of existing synthetic aperture sonars, towed operation requires a winch for deploying and retrieving the towed body, and the vessel must have an A-frame for easy hoisting. This operational mode places high demands on the vessel used for underwater target and terrain detection, making it unsuitable for small boats or unmanned surface vessels (USVs). Side-mounted operation requires a pylon fixed to the ship's side and reinforced. While this reduces the requirements for the vessel, the rigid structure of the sonar and vessel means that in rough seas or when the vessel is under significant sway, the sonar cannot maintain a uniform linear motion, resulting in a deterioration in aperture synthesis performance. Utility Model Content

[0005] This utility model provides a high-resolution underwater target detection system, which includes a work vessel and a towed fish;

[0006] The work vessel is used to tow the trawler;

[0007] The towed fish is equipped with transducer arrays on its left and right sides respectively; the transducer array includes a transmitter array, multiple preamplifiers and a receiver array;

[0008] The transmitting array is positioned forward of the navigation direction, and multiple receiving arrays are positioned rearward of the navigation direction and are arranged on the same axis as the transmitting array.

[0009] The number of preamplifiers matches the number of receiver arrays and is arranged beside the receiver arrays of the corresponding channels.

[0010] Furthermore, the transmitting array and the receiving array have the same orientation, and the angle between the normals of the transmitting array and the receiving array surfaces and the horizontal plane is 25°.

[0011] The vertical beam radiated by the transmitting array is obliquely irradiated onto the bottom of the water and underwater targets on both sides of the towed fish, generating corresponding acoustic echoes, which are received by the receiving array on the transducer array.

[0012] Furthermore, the high-resolution underwater target detection system also includes a positioning device, which includes a positioning device main unit and a positioning device antenna;

[0013] The locator antenna is used to acquire positioning information, and the locator host calculates the position of the towed fish through offset correction.

[0014] Furthermore, the high-resolution underwater target detection system also includes a positioning device; the positioning device includes a positioning device main unit and a positioning device antenna, the positioning device antenna is fixed to the top of the cabin of the working vessel to acquire positioning information, and the positioning device main unit acquires the position of the towed fish.

[0015] Furthermore, the transducer array has a -3dB beam angle of 40° in the vertical track direction and a -3dB beam angle of 4.8° in the track direction.

[0016] The transducer array is set to operate at a frequency of 400 kHz and a bandwidth of 50 kHz.

[0017] Furthermore, the vertical track length of the transmitting array or receiving array is 4.75 mm, the track length is 39.6 mm, the track aperture resolution is 19.8 mm, and the vertical track spatial resolution is 15 mm.

[0018] The center distance between the transmitting array and the adjacent receiving array is 43mm, the center distance between two adjacent receiving arrays is 40mm, the number of receiving arrays on one side is 20, the preamplifier is arranged next to the receiving array of the corresponding channel, and the effective length of the transducer array is about 850mm.

[0019] Furthermore, the work vessel and the trawler are connected by a watertight towing cable 500;

[0020] The watertight towing cable is filled with Kevlar material to increase its working tensile strength. The watertight towing cable is connected to the towing point on the top of the towed fish through a cable net or towing head, applying an upward towing force to the towed fish so that the towed fish can maintain a constant speed and straight-line movement at a fixed depth in the water.

[0021] Furthermore, the watertight towing cable also integrates two armored optical fibers and two power lines for supplying power to the towed fish and transmitting signals.

[0022] Furthermore, the towed fish is a cylindrical watertight compartment, consisting of a cylindrical body and end caps at both ends, with the end caps sealed to the body via watertight sealing rings.

[0023] Furthermore, the towed fish also includes an attitude sensor; the attitude sensor is used to collect the attitude information of the towed fish, including heading angle, pitch angle, and roll angle.

[0024] The beneficial effects achieved by this utility model are:

[0025] Because this invention uses a high operating frequency, the size of the transducer array can be designed to be very small. At the same time, by optimizing the size of the electronic system, the volume of the towed fish can be significantly reduced, enabling manual deployment without the need for winches, large A-frames or gantry cranes, thus broadening the application scenarios.

[0026] In existing technologies, the detection system moves forward during operation. From the moment the sound wave leaves the transmitting array until it is backscattered back to the receiving array by the target, the receiving array is constantly moving forward. Because the receiving array has a small -3dB beam opening angle in the flight path, if the movement distance is too large, the echo signal cannot be received, making synthetic aperture imaging of the target impossible. This invention uses multiple receiving arrays, ensuring that more than half of the arrays can receive the target's echo signal at any given time.

[0027] This invention employs synthetic aperture technology, which is more suitable for high-resolution imaging of small underwater targets. This technology utilizes the movement of a small-aperture array to virtually replicate the imaging effect of a large-aperture array tens of times its length, thereby achieving extremely high resolution in the azimuth direction. Since synthetic aperture technology has imaging resolution independent of imaging distance, it can achieve constant high resolution across the entire imaging area, resulting in high efficiency and accuracy in the detection of small underwater targets. Attached Figure Description

[0028] Figure 1 This is a block diagram of a high-resolution underwater target detection system according to an embodiment of the present invention;

[0029] Figure 2 This is a schematic diagram of the installation layout of a high-resolution underwater target detection system according to an embodiment of the present invention;

[0030] Figure 3 This is a block diagram of the watertight electronic compartment in a high-resolution underwater target detection system according to an embodiment of the present invention.

[0031] Figure 4This is a block diagram of the transducer array in a high-resolution underwater target detection system according to an embodiment of the present invention.

[0032] Figure 5 This is a schematic diagram illustrating the operation of a transducer array in a high-resolution underwater target detection system according to an embodiment of the present invention. Detailed Implementation

[0033] The technical solution of this utility model will be described in more detail below with reference to the accompanying drawings. This utility model includes, but is not limited to, the following embodiments.

[0034] As attached Figure 1 As shown, this utility model provides a high-resolution underwater target detection system, including a towed fish 10, a positioning device 20, a signal processing unit 30, and a display and control unit 40. The towed fish 10 mainly transmits acoustic signals and collects, processes, and uploads target-scattered echoes. The positioning device 20 includes a positioning host 201 and a positioning antenna 202, mainly realizing the product's positioning function. The signal processing unit 30 mainly realizes the functions of power supply, data processing, acoustic image generation, and conversion of positioning coordinate information for the towed fish 10. The display and control unit 40 mainly realizes the functions of system parameter download, system start / stop control, image display, data storage, target management, and identification.

[0035] like Figure 2 The diagram shows the installation layout of the various parts of the high-resolution underwater target detection system of this invention on 600 working vessels.

[0036] The display and control unit 40, the integrated processor 30, and the positioning host 201 are arranged on the deck or in the cabin of the work vessel.

[0037] The display and control unit 40 and the signal processing unit are connected via a Cat5e network cable to transmit instructions issued by the display and control unit 40 and image and sensor data uploaded by the signal processing unit.

[0038] The signal processing unit 30 and the positioning device 20 are connected by a serial cable for transmitting positioning information.

[0039] The display and control unit 40 can input the position offset of the positioning device and the towed fish 10, thereby accurately obtaining the position of the towed fish 10 and locating the precise position of the underwater target.

[0040] The positioning antenna 202 is fixed to the top of the cabin of the working vessel to obtain positioning information. The positioning host 201 calculates the position of the towed fish 10 through offset correction.

[0041] A custom-designed watertight towing cable 500 connects the signal processing unit 30 and the towed fish 10. The end of the watertight towing cable connected to the towed fish 10 uses a 2-optical-2-electric watertight connector, while the end connected to the signal processing unit 30 uses either a 2-optical-2-electric navigation connector or a watertight connector. The watertight towing cable integrates two armored optical fibers and two power cables. The optical fibers transmit commands issued by the signal processing unit 30 and raw data and optical synchronization signals uploaded by the towed fish 10. The power cables supply power to the towed fish 10. The watertight towing cable is also filled with Kevlar material to increase its working tensile strength. The watertight cable can be connected to the towing point on the top of the towed fish 10 via a cable net or a towing head, applying an upward-sloping towing force to the towed fish 10, allowing it to maintain a constant speed and straight-line motion at a fixed depth in the water.

[0042] like Figure 3 As shown, the towed fish 10 mainly consists of a power conversion circuit 101, a transmission drive circuit 104, a receiving acquisition circuit 105, a control center 102, a transducer array 110, a depth gauge 103, an attitude sensor 106, and a structural platform 107.

[0043] The structural platform 107 is used to carry the electronic components of the towed fish 10, ensuring that the electronic components can move smoothly, at a constant speed and depth in the water, ultimately achieving clear imaging of the target. It mainly consists of a head, a main hull, and a tail.

[0044] The main body is a cylindrical watertight compartment, mainly composed of a cylindrical body and end caps at both ends. The end caps are sealed to the body through watertight sealing rings.

[0045] The main cabin houses the power conversion circuit 101, control center 102, transmission drive circuit 104, receiving and acquisition circuit 105, and attitude sensor 106. A small hole is provided on the end cap at one end of the main cabin, through which the depth gauge passes. The pressure sensing surface is outside the watertight electronic cabin, and the data transmission line is inside the watertight electronic cabin. The depth gauge body is sealed to the end cap by a watertight sealing ring.

[0046] like Figure 4 As shown, a transducer array is installed on each side of the main hull. The transducer array mainly consists of a transmitter array 1101, a receiver array 1104, a preamplifier 1103, a tail cable 1102, and an array housing 1105. The transmitter array 1101 is positioned forward of the navigation direction, and the receiver array 1104 is positioned aft of the navigation direction. The transmitter array 1101 and the receiver array 1104 are on the same axis, and the transducer array axis is parallel to the axis of the towed fish 10.

[0047] Both the transmitting array 1101 and the receiving array 1104 of the synthetic aperture sonar are directional. For the transmitting array 1101, directionality means that the transmitted energy can be concentrated in a certain direction, thus allowing for the detection of targets at greater distances with lower transmission power. The directional nature of the receiving array 1104 enables the system to receive signals in a directional manner, thereby suppressing signals and interference from other directions.

[0048] like Figure 5 As shown, during normal underwater navigation of the towed fish 10, the angle between the transducer array's array surface normal and the horizontal plane is α = 25°. The vertical beam radiated by the transmitting array 1101 in the transducer array obliquely illuminates the bottom of the towed fish 10 on both sides and small underwater targets, generating corresponding acoustic echoes, which are received by the receiving array 1104 on the transducer array. The figure shows that the transducer array has a -3dB beam opening angle θ in the vertical trajectory direction. v The larger the beam opening angle, the larger the area illuminated by the sound waves, and the higher the scanning efficiency. However, with the total transmit power of the transducer remaining constant, a larger beam opening angle results in a shorter detection range. Based on engineering application experience, the vertical track of the synthetic aperture is generally set to a -3dB beam opening angle θ. v Set it to around 40°.

[0049] At a beam opening angle of -3dB θ v When fixed, the length L of the transducer array is inversely proportional to the acoustic frequency f. To reduce the length L of the transducer array and decrease the volume of the transducer array 110, the acoustic frequency f needs to be increased. Traditional synthetic aperture sonars operate at relatively low frequencies, resulting in a large size for the transducer array 110. In this invention, the frequency is set to 400kHz, so the vertical track length L of the transducer array is 4.75mm.

[0050] The track length D of the transmitting array 1101 or the receiving array 1104 and the track-direction -3dB beam opening angle θ y It is related to the sound wave frequency f. Based on engineering application experience, the beam opening angle of the -3dB beam towards the flight path is generally set to θ. y = Approximately 4.8°. Increasing the operating frequency can also reduce the transducer array track length D, thus improving the track spatial resolution ρ. y When the operating frequency is set to 400kHz, the track length D of the transmitter array 1101 or receiver array 1104 is 39.6mm, and the track aperture resolution is ρ. y =19.8mm.

[0051] Synthetic aperture sonar employs pulse compression technology to improve vertical trajectory spatial resolution, and this resolution is only related to the bandwidth of the transmitted signal; the larger the operating bandwidth of the device, the higher the vertical trajectory spatial resolution ρ. x The better.

[0052] In designing the transmitter array 1101, to achieve the maximum transmit voltage response, the resonant frequency of the transmitter array 1101 was set to 400kHz, while the transmit voltage response at the resonant frequency is generally narrow. After actual testing, the operating bandwidth was set to 50kHz. In this embodiment, the vertical trajectory spatial resolution ρ... x =15mm.

[0053] During normal operation, the detection system moves forward. From the moment the sound wave leaves the transmitting array 1101 until it is backscattered back to the receiving array 1104 by the target, the receiving array 1104 is constantly moving forward. Because the receiving array 1104 has a small -3dB beam opening angle in the track direction, if the moving distance is too large, the echo signal cannot be received, and synthetic aperture imaging of the target cannot be performed. Therefore, to solve this problem, multiple receiving arrays 1104 are usually set up to ensure that more than half of the receiving arrays 1104 can receive the target's echo signal at any given time.

[0054] The maximum speed is determined by the total length of the receiver array 1104 and the single-sided detection range. Taking all factors into consideration, the center distance between the transmitter array 1101 and the adjacent receiver array 1104 is set at 43mm, the center distance between two adjacent receiver arrays 1104 is 40mm, the number of receiver arrays 1104 on one side is 20, the preamplifier is arranged beside the receiver array 1104 in the corresponding channel, and the effective length of the transducer array is approximately 850mm. Figure 4 As shown.

[0055] The transmitter array 1101, receiver array 1104, and preamplifier are arranged within a long, narrow groove made of 316L stainless steel, and are watertight using a fully encapsulated polyurethane potting compound. A cable hole is pre-drilled at one end of the groove for the tail cables of the transmitter array 1101 and receiver array 1104. The groove can be directly excavated outside the watertight electronics compartment, or it can be excavated from a separate 316L stainless steel structure to form an independent transducer array. This transducer array is connected to the watertight electronics compartment via a watertight connection.

[0056] The main workflow of the towed fish 10 is as follows: After receiving the configuration and start instructions from the signal processing unit 30, the control center 102 sends the configuration and start instructions to the transmission drive circuit 101; the transmission drive circuit generates a pulsed linear frequency modulated high voltage electrical signal to drive the transmission array 1101 in the transducer array 110; the transmission array 1101 converts the linear frequency modulated high voltage electrical signal into an acoustic signal, which radiates towards the target area with a sound beam at a specific opening angle. The acoustic signal reflected back by the target is then received by the receiving array 1104 in the transducer array 110 and converted into an echo analog electrical signal; the preamplifier 1103 in the transducer array 110 converts the echo analog electrical signal output by the receiving array 1104 into an echo analog electrical signal. After initial amplification, the signal is output to the receiving and acquisition circuit 105. The receiving and acquisition circuit 105 then performs hardware amplification and filtering on the pre-amplified echo analog electrical signal and converts it into an echo digital electrical signal, which is then sent to the control center 102. The depth gauge 103 is used to acquire the depth information of the towed fish 10 from the water surface and sends the depth information to the control center 102. The attitude sensor 106 is used to acquire the attitude information of the towed fish 10, including heading angle, pitch angle, roll angle, etc., and sends the attitude information to the control center 102. The control center 102 packages the received echo digital electrical signal, depth information, and attitude information into data and uploads it to the signal processing unit 30 via Ethernet.

[0057] During the exploration operation, the vessel 600 travels at a constant speed in a straight line, and the towed fish 10 also maintains a constant speed and a straight line underwater. The high-resolution underwater target detection system emits sound waves into the seabed through the towed fish 10 at fixed intervals and collects the echo signals, which are then uploaded to the signal processing unit 30. The signal processing unit 30 performs synthetic aperture processing on the echo signals collected from different locations of the towed fish 10 to obtain real-time acoustic images of small underwater targets and underwater topography, which are then displayed on the display and control software of the display and control unit in a waterfall diagram format.

[0058] The target recognition function of the display and control software can automatically identify small underwater targets and save or send the images and location information of the small underwater targets to the next level system, thereby realizing the detection and positioning of small underwater targets.

[0059] This invention employs synthetic aperture technology, which is more suitable for high-resolution imaging of small underwater targets. This technology utilizes the movement of a small-aperture array to virtually replicate the imaging effect of a large-aperture array tens of times its length, thereby achieving extremely high resolution in the azimuth direction. Since synthetic aperture technology has imaging resolution independent of imaging distance, it can achieve constant high resolution across the entire imaging area, resulting in high efficiency and accuracy in the detection of small underwater targets.

[0060] Because this invention uses a high operating frequency, the size of the transducer array can be designed to be very small. By optimizing the size of the electronic system, the volume of the towed fish 10 can be significantly reduced, enabling manual deployment without the need for winches, large A-frames, or gantry cranes, thus broadening the application scenarios.

[0061] This utility model is not limited to the specific embodiments described above. Those skilled in the art can implement this utility model using other specific embodiments based on the disclosed content of the embodiments and drawings. Therefore, any design that adopts the design structure and concept of this utility model and makes some simple changes or modifications falls within the protection scope of this utility model.

Claims

1. A high-resolution underwater target detection system, characterized in that, The high-resolution underwater target detection system includes a work vessel (600) and a towed fish (10); The work vessel (600) is used to tow the trawler (10); The towed fish (10) is equipped with transducer arrays (110) on its left and right sides respectively; the transducer array (110) includes a transmitter array (1101), multiple preamplifiers (1103) and a receiver array (1104); The transmitting array (1101) is located on the front side of the navigation direction, and the plurality of receiving arrays (1104) are located on the rear side of the navigation direction and are arranged on the same axis as the transmitting array (1101). The number of preamplifiers (1103) matches the number of receiver arrays (1104), and they are arranged beside the receiver arrays (1104) of the corresponding channels.

2. The high-resolution underwater target detection system according to claim 1, characterized in that, The transmitting array (1101) and the receiving array (1104) have the same orientation, and the angle between the normal of the transmitting array (1101) and the receiving array (1104) and the horizontal plane is 25°. The vertical beam radiated by the transmitting array (1101) is obliquely irradiated onto the bottom of the water and underwater targets on both sides of the towed fish (10), generating corresponding acoustic echoes, which are received by the receiving array (1104) on the transducer array.

3. The high-resolution underwater target detection system according to claim 1, characterized in that, The high-resolution underwater target detection system also includes a positioning device (20), which includes a positioning device host (201) and a positioning device antenna (202); The locator antenna (202) is used to acquire positioning information, and the locator host (201) calculates the position of the towed fish (10) through offset correction.

4. The high-resolution underwater target detection system according to claim 1, characterized in that, The high-resolution underwater target detection system also includes a locator (20); the locator (20) includes a locator host (201) and a locator antenna (202), the locator antenna (202) is fixed on the top of the cabin of the work vessel to obtain positioning information, and the locator host (201) obtains the position of the towed fish (10).

5. The high-resolution underwater target detection system according to claim 1, characterized in that, The transducer array (110) has a -3dB beam opening angle of 40° in the vertical track direction and is generally set to 4.8° in the track direction. The transducer array (110) is set to operate at a frequency of 400 kHz and a bandwidth of 50 kHz.

6. The high-resolution underwater target detection system according to claim 5, characterized in that, The transmitting array (1101) or receiving array (1104) has a vertical track length of 4.75 mm, a track length of 39.6 mm, a track aperture resolution of 19.8 mm, and a vertical track spatial resolution of 15 mm. The center distance between the transmitting array (1101) and the adjacent receiving array (1104) is 43mm, the center distance between two adjacent receiving arrays (1104) is 40mm, the number of receiving arrays (1104) on one side is 20, the preamplifier is arranged on the side of the receiving array (1104) of the corresponding channel, and the effective length of the transducer array is about 850mm.

7. The high-resolution underwater target detection system according to claim 1, characterized in that, The work vessel (600) and the towed fish (10) are connected by a watertight towing cable 500; The watertight towing cable (500) is filled with Kevlar material to increase the working tensile strength of the watertight cable. The watertight towing cable (500) is connected to the towing point on the top of the towed fish (10) through a cable net sleeve or towing head, applying an upward towing force to the towed fish (10), so that the towed fish (10) can maintain a constant speed and straight-line navigation at a fixed depth in the water.

8. The high-resolution underwater target detection system according to claim 7, characterized in that, The watertight towing cable (500) also integrates two armored optical fibers and two power lines for supplying power to the towed fish (10) and transmitting signals.

9. The high-resolution underwater target detection system according to claim 1, characterized in that, The towed fish (10) is a cylindrical watertight compartment, consisting of a cylindrical body and end caps at both ends. The end caps at both ends are sealed to the body through watertight sealing rings.

10. The high-resolution underwater target detection system according to claim 1, characterized in that, The towed fish (10) also includes an attitude sensor (106); the attitude sensor (106) is used to collect attitude information of the towed fish (10), including heading angle, pitch angle and roll angle.

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