A suspended search and rescue sonar device, system and azimuth measurement method

Abstract

The present invention discloses a suspended search and rescue sonar device, system and azimuth measurement method, which can be used for searching and positioning shipwreck beacons and aircraft black box beacons. It includes a vector hydrophone array, a watertight electronic cabin, a load-bearing optical and electrical composite cable, an optical and electrical modem, a portable processor, and a GPS locator. It uses the direction-finding principle of the vector hydrophone to measure the direction of the black box beacon of a crashed ship or aircraft, and then combines the multiple direction-finding results from different locations and the position of the measurement point output by the GPS locator, and adopts the multi-point intersection and coordinate transformation method to estimate the absolute position of the acoustic beacon, which is a prerequisite for rescuing crashed ships and crashed aircraft. This search and rescue sonar has a low cost and a simple system structure, and can be suspended and used on helicopters or ships participating in the rescue.

Description

Technical Field

[0001] The present invention relates to the technical field of underwater sonar, and specifically to a suspended search and rescue sonar device, system and azimuth measurement method. Background Art

[0002] As an information recording device, the "black box" can record data before an accident and provide a basis for analyzing the cause of the accident. After the "black box" sinks to the bottom of the sea, the working time of the acoustic beacon in the "black box" generally does not exceed 30 days. For underwater search and rescue operations, positioning the acoustic beacon of the "black box" is a prerequisite for maritime search and rescue operations. If the "black box" has not been found 30 days after the accident, it will be very difficult to find the crashed aircraft or ship. Therefore, searching for the acoustic beacon of the "black box" is an extremely urgent problem that needs to be solved currently.

[0003] In this context, the present invention proposes a suspended search and rescue sonar that can be suspended and used on helicopters and ships, adding a means for underwater search and rescue to locate the black box beacon. Summary of the Invention

[0004] To solve the deficiencies and problems existing in the above-mentioned prior art, the inventor provides an effective, efficient, and highly accurate underwater rapid search and rescue sonar technology. Specifically, the present invention is implemented as follows: A suspended search and rescue sonar device includes a wet-end device, a dry-end device, and a load-bearing optoelectronic composite cable connecting the two. The wet-end device includes a vector hydrophone array and a watertight electronic cabin connected to each other. The dry-end device includes an optoelectronic modem connected to the other end of the load-bearing optoelectronic composite cable, which is network-connected to a portable processor, and a GPS locator connected to the portable processor.

[0005] Further, the vector hydrophone array is composed of a plurality of hydrophones arranged longitudinally one above the other in a group array.

[0006] Further, the two hydrophones at the upper and lower poles of the vector hydrophone array are both pressure hydrophones, and several hydrophones in the middle section are all differential pressure vector hydrophones. The differential pressure vector hydrophone array has passed a consistency test before being grouped, and is composed of array elements with a high receiving directivity matching degree, and the direction of each array element is the same when being grouped.

[0007] Further, the watertight electronic cabin includes a hardware circuit, an attitude sensor, and an uninterruptible power supply component; among them, the hardware circuit includes a power supply circuit, a pre-amplifier circuit, a signal conditioning circuit, a controllable gain amplifier circuit, an AD acquisition circuit, an isolation circuit, an optoelectronic conversion circuit, a main control circuit, and upper and lower bottom plate circuits. Among them, the other circuits except the upper and lower bottom plate circuits are in a disk shape, and are connected to the upper and lower ends through connectors to the upper and lower bottom plate circuits in sequence. The upper and lower bottom plate circuits supply power to them and provide signal traces between these circuit boards.

[0008] On the other hand of the present invention, a suspended search and rescue sonar system includes a wet end module, a dry end module, and a load-bearing optical and electrical composite cable connecting the two. The wet end module is used to measure acoustic signals in the underwater sound field, obtain vector information of the sound field, and convert the vector information into network data packets after processing and transmit them to the dry end device through the load-bearing optical and electrical composite cable; the dry end module is used to obtain the azimuth information of each frequency point from the FFT measurement results of the sound pressure channel and the vector channel in the network data packet, and process the absolute azimuth result through the time-frequency point of the beacon pulse signal and the azimuth result at the effective pulse signal.

[0009] Furthermore, the wet end module is also used to obtain the three-axis attitude data in the wet end module, and the FPGA is used to implement the main control circuit to complete gain control, power supply control, addition of multi-channel vector array element signals, FFT operation of multi-channel signals, asynchronous serial communication, data packing, and network communication.

[0010] Furthermore, the dry end module is also used to obtain the three-axis attitude data and convert the relative azimuth information of the vector information of the obtained sound field into the north-pointing absolute azimuth information based on it.

[0011] Furthermore, the dry end module is also used to capture the network data packet uploaded by the wet end module, parse the data packet to obtain the FFT results of the sound pressure channel and the vector channel and the attitude sensor data, use the sound pressure and particle velocity conjugate cross-spectrum method to obtain the azimuth information of each frequency point, then use the time spectrogram of the sound pressure channel to obtain the time-frequency point of the effective beacon pulse signal, perform statistical azimuth estimation on the azimuth result at the effective pulse signal using the threshold extraction method, and finally perform coordinate conversion in combination with the data of the attitude sensor to convert the relative measurement azimuth into the north-pointing absolute azimuth, and record the measurement point coordinate data and the absolute azimuth result of the current GPS locator.

[0012] On yet another aspect of the present invention: A method for measuring the azimuth of a suspended search and rescue sonar is provided, which is characterized by including the following steps:

[0013] S1. The vector hydrophone array placed underwater measures acoustic signals in the underwater sound field, obtains vector information and attitude information of the sound field, and converts the vector information and attitude information into network data packets after FFT operation processing and then sends them;

[0014] S2. Obtain the network data packet described in step 1, parse the data packet to obtain the FFT results of the sound pressure channel and the vector channel and the attitude sensor data, and use the sound pressure and particle velocity conjugate cross-spectrum method to obtain the azimuth information of each frequency point;

[0015] S3. Obtain the time-frequency points of the effective beacon pulse signal from the spectrogram of the sound pressure channel, and perform statistical azimuth estimation on the azimuth results at the effective pulse signal using the threshold extraction method to obtain azimuth estimation data;

[0016] S4. Combine the azimuth estimation data with the attitude information in step S1 for coordinate transformation, convert the relative measurement azimuth to the north-referenced absolute azimuth, and record the measurement point coordinate data and the absolute azimuth result of the current GPS locator.

[0017] Further, it further includes step S5. If there are two or more sets of measurement data from different locations with relatively large differences in the measurement point coordinate data and the absolute azimuth result, then calculate the estimated value of the absolute position of the beacon through the plane multi-point intersection method; and during measurement, add the signals of each array element to form a beam with a certain opening angle, so as to enhance the detected signal, and at the same time suppress the isotropic noise to obtain a signal with a higher signal-to-noise ratio.

[0018] Introduction to the working principle of the present invention:

[0019] In terms of hardware, a vector hydrophone array is formed. The receiving sensitivity fluctuation of the pressure hydrophone in the horizontal circumferential direction within the working frequency band is relatively small. After array formation, two pressure hydrophones are arranged at the upper and lower poles of the hydrophone array. The differential vector hydrophone needs to undergo a consistency test before array formation. Select array elements with a relatively high receiving directivity matching degree for array formation, and ensure that the direction of each array element is consistent during array formation. During measurement, add the signals of each array element to form a beam with a certain opening angle, so as to enhance the detected signal, and at the same time suppress the isotropic noise to obtain a signal with a higher signal-to-noise ratio, thereby improving the detection ability of the search and rescue sonar. And perform signal processing, communication transmission, and coordinate transformation in combination with the three-axis attitude data. The post-processing converts the relative azimuth result measured by the vector hydrophone array into the absolute north-referenced azimuth result, so as to obtain accurate measurement position data.

[0020] Beneficial effects of the present invention: The suspended search and rescue sonar device, system and azimuth measurement method provided by the present invention are scientifically reasonable, simple, low-cost and flexible in structure. At the system and measurement method levels, it achieves the effects of high positioning accuracy and wide search range. In terms of application, it can be suspended and used on helicopters or ships participating in search and rescue missions, and is a good supplement to underwater rescue equipment. Brief Description of the Drawings

[0021] Figure 1 It is the working block diagram of a suspended search and rescue sonar of the present invention;

[0022] Figure 2 It is the structural diagram of the vector hydrophone array;

[0023] Figure 3 It is the internal structure diagram of the watertight electronic cabin;

[0024] Figure 4 It is a flow chart for processing search and rescue sonar data.

[0025] Among them: 1 - wet-end equipment, 2 - dry-end equipment, 3 - load-bearing fiber optic composite cable, 4 - vector hydrophone array, 5 - watertight electronic cabin, 6 - portable processor, 7 - GPS locator, 8 - optoelectronic modem, 9 - pressure hydrophone, 10 - differential pressure vector hydrophone. Specific embodiments

[0026] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present invention.

[0027] Embodiment 1: A suspended search and rescue sonar device includes a wet-end equipment 1, a dry-end equipment 2 and a load-bearing fiber optic composite cable 3 connecting the two. The wet-end equipment 1 includes a vector hydrophone array 4 and a watertight electronic cabin 5 which are connected to each other. The dry-end equipment 2 includes an optoelectronic modem 8 connected to the other end of the load-bearing fiber optic composite cable 3 and is network-connected to a portable processor 6, and a GPS locator 7 connected to the portable processor 6. The vector hydrophone array 4 is formed by arranging a number of hydrophones vertically one above the other in a longitudinal array. The two hydrophones at the upper and lower poles of the vector hydrophone array 4 are both pressure hydrophones 9, and several hydrophones in the middle section are all differential pressure vector hydrophones 10. The differential pressure vector hydrophone array 10 has passed a consistency test before arraying and is formed by arraying elements with high receiving directivity matching degrees, and the direction of each element is the same when arraying. The watertight electronic cabin 5 includes a hardware circuit, an attitude sensor and an uninterruptible power supply component; among them, the hardware circuit includes a power supply circuit, a preamplifier circuit, a signal conditioning circuit, a controllable gain amplifier circuit, an AD acquisition circuit, an isolation circuit, an optoelectronic conversion circuit, and a main control circuit; because this device is used in a suspended manner, the wet-end equipment 1 is entirely supported by the fiber optic composite cable, so it is necessary to use a fiber optic composite cable containing high-tensile materials inside that can bear a certain weight, which is called a load-bearing fiber optic composite cable in this embodiment.

[0028] Describe the implementation examples of each key part: 1 as Figure 2As shown in the figure, in order to balance the size of the hydrophone array and the receiving sensitivity, the vector hydrophone array 4 is composed of 10 differential pressure vector hydrophones 10 and two pressure hydrophones 9. To avoid the influence of physical boundaries on the vector array elements, the 10 vector array elements are placed in the middle, and the two pressure hydrophones 9 are placed on both sides to form the hydrophone array. It is required that the receiving sensitivity fluctuation of the used pressure hydrophone 9 in the horizontal circumferential direction within the working frequency band is as small as possible, and it can be screened through pool tests. The differential pressure vector hydrophone 10 needs to undergo a consistency test before arraying. Select array elements with a higher receiving directivity matching degree for arraying, and ensure that the direction of each array element is consistent during arraying. During operation, the signals of the 10 array elements are added together to form a beam with a certain opening angle, enhancing the signal intensity. At the same time, it can suppress isotropic noise interference, enabling the sonar system to obtain signals with a higher signal-to-noise ratio, thereby improving the detection ability of the search and rescue sonar and expanding its detection range. 2 As Figure 3 As shown in the figure, the watertight electronic cabin 5 contains a hardware circuit, an attitude sensor, and an uninterruptible power supply component. The hardware circuit is composed of a power supply circuit, a preamplifier circuit, a signal conditioning circuit, a controllable gain amplifier circuit, an AD acquisition circuit, an isolation circuit, an optoelectronic conversion circuit, and a main control circuit. Due to the limited space of the watertight electronic cabin 5 and its cylindrical internal space, the appearance of these circuit boards is designed to be circular, and a structure is adopted in which the upper and lower bottom plates sandwich these circular circuit boards in the middle. The upper and lower bottom plates also provide power supply and signal routing for these circuit boards. Among them, the main control circuit is implemented with an FPGA, which mainly completes gain control, power supply control, addition of multi-channel vector array element signals, FFT operation of multi-channel signals, asynchronous serial communication to receive attitude sensor data, data packaging, and network communication. The network communication can be implemented at the data link layer; the attitude sensor needs to output three-axis attitude data, and the most important data is its north-pointing azimuth data, which is used to convert the relative azimuth result measured by the vector hydrophone array 4 into the absolute north-pointing azimuth during later processing; in order to meet both the long-term uninterrupted operation of the search and rescue sonar and the demand of the search and rescue sonar conditioning circuit for a low-noise power supply, an uninterruptible power supply component is added, which is composed of two groups of batteries, a step-down rectification circuit, and a relay switching circuit. By connecting to an external 220v AC power supply, seamless switching control of charging one group of batteries and powering the search and rescue sonar circuit with the other group of batteries is achieved using high-quality dual-power uninterruptible power supply technology, thereby realizing the provision of a long-term uninterrupted and low-noise power supply for the search and rescue sonar circuit.

[0029] Embodiment 2: A suspended search and rescue sonar system includes a wet-end module, a dry-end module, and a load-bearing optoelectronic composite cable connecting the two. The wet-end module is used to measure acoustic signals in the underwater sound field, obtain vector information of the sound field, and convert the processed vector information into network data packets for transmission to the dry-end device through the load-bearing optoelectronic composite cable. The dry-end module is used to obtain the azimuth information of each frequency point from the FFT measurement results of the sound pressure channel and the vector channel in the network data packet, and process the absolute azimuth result through the time-frequency point of the beacon pulse signal and the azimuth result at the effective pulse signal. The wet-end module is also used to obtain the three-axis attitude data inside the wet-end module, and implement the main control circuit by FPGA to complete gain control, power supply control, addition of multi-channel vector array element signals, FFT operation of multi-channel signals, asynchronous serial communication, data packaging, and network communication. The dry-end module is also used to obtain the three-axis attitude data and convert the relative azimuth information of the vector information of the obtained sound field into the north-referenced absolute azimuth information based on it. The dry-end device obtains the real and imaginary part data of the FFT operation of one sound pressure channel and two vector channels and the attitude sensor data from the network data packet, then uses the cross-spectrum conjugate algorithm to calculate the azimuth value at each frequency point within the beacon emission frequency range in the FFT result, and then combines the attitude sensor data corresponding to this moment to complete coordinate transformation and obtain the absolute azimuth value at each frequency point. By combining the frequency and period characteristics of the beacon pulse, effective pulses are found by the method of crossing the threshold in the FFT result of a specific duration, and the absolute azimuth result at the effective pulse is extracted as the measurement result. That is, grab the network data packet uploaded by the wet-end module, parse the data packet to obtain the FFT results of the sound pressure channel and the vector channel and the attitude sensor data, use the sound pressure-velocity conjugate cross-spectrum method to obtain the azimuth information of each frequency point, then use the spectrogram of the sound pressure channel to obtain the time-frequency point of the effective beacon pulse signal, perform statistical azimuth estimation on the azimuth result at the effective pulse signal using the threshold extraction method, and finally combine the data of the attitude sensor to perform coordinate transformation, convert the relative measurement azimuth into the north-referenced absolute azimuth, and record the measurement point coordinate data and the absolute azimuth result of the current GPS locator.

[0030] Embodiment 3: A method for measuring the position of a suspended search and rescue sonar, as Figure 4As shown, the vector hydrophone array placed underwater measures the acoustic signals in the underwater sound field, obtains the vector information of the sound field, adds the signals to form a fixed beam, performs FFT operations on the vector x, vector y, and sound pressure p, and then packs and sends the data to the host computer for processing after adding attitude information data; the host computer captures packets based on ShaipPcap, performs data parsing, and uses the sound pressure and particle velocity conjugate cross-spectrum method to obtain the azimuth information at each frequency point from the FFT results of the sound pressure channel and vector channel and the attitude sensor data; searches for pulses, uses the spectrogram of the sound pressure channel to obtain the time-frequency points of the effective beacon pulse signals, performs statistical azimuth estimation on the azimuth results at the effective pulse signals using the threshold extraction method, and performs coordinate conversion and calculates the absolute azimuth in combination with the attitude information data, records the current measurement point coordinates and the measurement absolute method. Specifically:

[0031] S1. The vector hydrophone array placed underwater measures the acoustic signals in the underwater sound field, obtains the vector information and attitude information of the sound field, and sends the data after processing the vector information and attitude information as network data packets.

[0032] S2. Obtain the network data packets described in step S1, parse the data packets to obtain the FFT results of the sound pressure channel and vector channel and the attitude sensor data, and use the sound pressure and particle velocity conjugate cross-spectrum method to obtain the azimuth information at each frequency point.

[0033] S3. Use the spectrogram of the sound pressure channel to obtain the time-frequency points of the effective beacon pulse signals, perform statistical azimuth estimation on the azimuth results at the effective pulse signals using the threshold extraction method to obtain azimuth estimation data.

[0034] S4. Perform coordinate conversion on the azimuth estimation data in combination with the attitude information described in step S1, convert the relative measurement azimuth to the north-referenced absolute azimuth, and record the measurement point coordinate data and the absolute azimuth result of the current GPS locator. During measurement, add the signals of each array element to form a beam with a certain opening angle, so as to enhance the detected signal, suppress isotropic noise at the same time, and obtain a signal with a higher signal-to-noise ratio. If there are two or more measurement data at different locations with a large difference in the measurement point coordinate data and the absolute azimuth result, then calculate the estimated value of the absolute position of the beacon by the plane multi-point intersection method.

[0035] In actual use, the portable processor consists of a general-purpose portable computer and the host computer software running on the portable computer. Here, it is the software that defines the functions of the components. The host computer software is written in Visual C# and borrows the network packet capture framework in the.NET environment. In the program, references to the dynamic link libraries SharpPcap.dll and PacketDotNet.dll are added. Based on the SharpPcap technology, the network data packets uploaded by the wet-end device are captured. After parsing the data packets according to the custom protocol, the real and imaginary parts of the FFT results of the sound pressure channel and the vector channel, as well as the attitude sensor data, are obtained. The sound pressure-velocity conjugate cross-spectrum method is used to obtain the azimuth at each time and frequency. Then, the effective beacon pulse signal time-frequency points are obtained by using the spectrogram of the sound pressure channel. When an effective beacon pulse signal is found, the threshold extraction method is used to perform long-term statistical estimation on the azimuth results at the effective pulse signal. Finally, coordinate transformation is performed in combination with the data of the attitude sensor to convert the relative measurement azimuth into the north-referenced absolute azimuth, and the measurement point coordinates and the absolute azimuth results of the current GPS locator are recorded. When there are two or more remotely different measurement data in the recorded data, the plane multi-point intersection algorithm is automatically called to calculate the estimated value of the absolute position of the beacon, and the position coordinates are displayed on the interface of the host computer software for users to use.

[0036] It should be understood that the above specific embodiments of the present invention are only used for exemplary illustration or explanation of the principle of the present invention, and do not constitute a limitation to the present invention. Therefore, any modifications, equivalent replacements, improvements, etc. made without departing from the spirit and scope of the present invention shall be included within the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all variations and modifications that fall within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A suspended search and rescue sonar system, characterized in that, It includes a wet-end module, a dry-end module, and a load-bearing optical and electrical composite cable connecting the two. The wet-end module is used to measure acoustic signals in the underwater sound field, obtain vector information of the sound field, and convert the processed vector information into network data packets for transmission to the dry-end device through the load-bearing optical and electrical composite cable. The dry-end module is used to obtain the azimuth information of each frequency point from the FFT measurement results of the sound pressure channel and the vector channel in the network data packet, and process the time-frequency points of the beacon pulse signal and the azimuth results at the effective pulse signal to obtain the absolute azimuth result. The wet-end module is also used to obtain the three-axis attitude data in the wet-end module, and the FPGA is used to implement the main control circuit to complete gain control, power supply control, addition of multi-channel vector array element signals, FFT operation of multi-channel signals, asynchronous serial communication, data packaging, and network communication. The dry-end module is also used to capture the network data packet uploaded by the wet-end module, parse the data packet to obtain the FFT results of the sound pressure channel and the vector channel and the attitude sensor data, use the sound pressure-velocity conjugate cross-spectrum method to obtain the azimuth information of each frequency point, then use the spectrogram of the sound pressure channel to obtain the effective time-frequency points of the beacon pulse signal, perform statistical azimuth estimation on the azimuth results at the effective pulse signal using the threshold extraction method, and finally perform coordinate transformation in combination with the data of the attitude sensor to convert the relative measurement azimuth into the north-pointing absolute azimuth, and record the measurement point coordinate data and the absolute azimuth result of the current GPS locator.

2. The suspended search and rescue sonar system according to claim 1, characterized in that, The dry-end module is also used to obtain the three-axis attitude data and convert the relative azimuth information of the obtained vector information of the sound field into the north-pointing absolute azimuth information based on it.

3. A method for measuring the azimuth of a suspended search and rescue sonar, characterized in that, It includes the following steps: S1. The vector hydrophone array placed underwater measures acoustic signals in the underwater sound field, obtains vector information and attitude information of the sound field, and converts the vector information and attitude information into network data packets after FFT operation processing and then sends them. S2. Obtain the network data packet described in step 1, parse the data packet to obtain the FFT results of the sound pressure channel and the vector channel and the attitude sensor data, and use the sound pressure-velocity conjugate cross-spectrum method to obtain the azimuth information of each frequency point. S3. Use the spectrogram of the sound pressure channel to obtain the effective time-frequency points of the beacon pulse signal, perform statistical azimuth estimation on the azimuth results at the effective pulse signal using the threshold extraction method to obtain the azimuth estimation data. S4. Combine the azimuth estimation data with the attitude information described in step S1 for coordinate transformation, convert the relative measurement azimuth into the north-pointing absolute azimuth, and record the measurement point coordinate data and the absolute azimuth result of the current GPS locator.

4. The azimuth measurement method of a suspended search and rescue sonar according to claim 3, characterized in that It also includes step S5. If there are two or more remotely measured data with large differences in the measurement point coordinate data and the absolute azimuth result, then calculate the estimated value of the absolute position of the beacon through the plane multi-point intersection method. During measurement, the signals of each array element are added to form a beam with a certain opening angle, so that the detection signal is enhanced, and at the same time, isotropic noise can be suppressed to obtain a signal with a higher signal-to-noise ratio.

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