Underwater Vehicle Positioning and Navigation Device and Method Based on Acoustic QR Code

Abstract

An underwater vehicle positioning and navigation device and method based on an acoustic QR code, which consists of two parts: an acoustic QR code identification plate and a sonar positioning device. The acoustic QR code identification plate is constructed by using the strong reflection of a corner reflector and the strong sound absorption characteristics of an underwater acoustic material. The sonar positioning device mounted on the underwater vehicle scans the waterway by emitting a beam and receives the echo of the acoustic QR code identification plate. Through real-time imaging and decoding processing, the longitude and latitude coordinate information is obtained, realizing precise underwater positioning and navigation. The two-dimensional coding of the present invention has flexible design, large storage capacity, and strong fault tolerance. The underwater coding device does not need to carry an active sound source, has a small space occupancy rate, is convenient for laying on the bottom of the water and long-term static placement, and has the characteristics of stable, persistent, and accurate positioning. By using the corner reflector echo enhancement technology, the echo is stable and easy to detect, and has the characteristics of high decoding success rate and good acoustic positioning reliability.

Description

Technical Field

[0001] The present invention belongs to the technical field of underwater vehicle underwater acoustic technology, and particularly relates to an underwater vehicle positioning and navigation device and method based on an acoustic QR code. Background Art

[0002] In recent years, underwater vehicles have developed rapidly. Driven by tasks such as marine resource development and utilization and the maintenance of marine rights and interests, they are applied to more and more complex environments, such as deeper and more fluctuating waters, and various underwater communication methods have been challenged to a certain extent. Underwater acoustic technology is an important tool for underwater communication. However, the current methods of underwater acoustic positioning and navigation are relatively single. The commonly used method is the active response mode that combines the use of an active sonar and a transponder. The transponder consumes a large amount of energy during long-term standby. It is difficult to ensure the performance stability of the equipment in a complex underwater environment and the cost is relatively high. It is difficult to be placed in water or on the water surface in large quantities for a long time as an underwater positioning and navigation tool. For passive methods, driven by the development of acoustic metasurfaces in the air, underwater metasurfaces have gradually found some applications, such as underwater acoustic invisibility cloaks and acoustic barcodes. However, the elastic effect of the underwater structure increases, and there are significant differences in the acoustic scattering effect, as well as in material and structure scales, compared with those in the air. Therefore, the actual underwater applications are relatively limited, and those for positioning and navigation are even rarer. By borrowing the design concepts and methods of land communication base station positioning, road signs, and commodity QR codes, a positioning and navigation method based on an underwater passive acoustic QR code sign is proposed, enabling an underwater vehicle to use the active sonar equipment carried to scan the underwater acoustic QR code sign at the bottom of the water, just like an aerial vehicle or a vehicle traveling on land locates and navigates based on land base stations or road signs, to obtain position information such as the absolute coordinates of the earth, achieve precise underwater positioning and navigation, and improve the diving operation ability in a complex underwater environment. Summary of the Invention

[0003] To overcome the deficiencies of the above-mentioned prior art, the present invention provides an underwater vehicle acoustic positioning and navigation device and method. Through underwater two-dimensional coding design using the strong echo generated by a corner reflector unit and the weak echo of an acoustic absorption covering layer unit, and by means of the side-scan sonar mounted on the underwater vehicle to perform beam scanning on the bottom of the water, extracting the characteristics and decoding the echo of the underwater acoustic QR code sign, the underwater position information is obtained, achieving the purpose of precise positioning and navigation of the underwater vehicle. The device is convenient and flexible to use. The underwater coding device does not need to carry an active sound source, has a large variety of coding types, and has the characteristics of stable, persistent, and accurate positioning, facilitating the navigation of the underwater vehicle.

[0004] The technical solution of the present invention is as follows:

[0005] An acoustic positioning and navigation system for an underwater vehicle, characterized in that the system consists of two parts: an acoustic QR code identification plate and a sonar positioning device. The sonar positioning device processes and analyzes the echoes received from the acoustic QR code identification plate by transmitting sound waves to obtain underwater positioning and navigation information.

[0006] The acoustic QR code identification plate is placed at the bottom of the water. This device consists of multiple black code and white code units, forming a planar, black-and-white, data symbol signal-recording pattern. When encoding, the black code represents "1" and the white code represents "0". The black codes and white codes are arranged in a certain form to form a matrix QR code, which is encoded by the different distributions of black and white pixels in a rectangular space. At the corresponding element positions of the matrix, the appearance of a dot represents binary "1", and the non-appearance of a dot represents binary "0". The arrangement and combination of the dots determine the meaning represented by the matrix QR code.

[0007] The surface of the acoustic QR code identification plate is divided into square grids representing black codes and white codes. The side length of each square is not less than the resolution in the along-track direction and the resolution in the cross-track direction of the side-scan sonar, so as to distinguish the black code and white code units. The resolution in the along-track direction and the resolution in the cross-track direction are determined by factors such as the speed, navigation depth, frequency, and beam width.

[0008] Each black code unit of the acoustic QR code identification plate consists of a two-dimensional array constructed by arranging multiple corner reflector units side by side. The corner reflector is a concave tetrahedron constructed by three titanium alloy faces, which has the advantages of high strength and corrosion resistance and is suitable for long-term placement in seawater. The vertically incident sound wave is scattered multiple times on the three faces of the corner reflector unit and then produces an echo enhancement effect through phase interference. Using the strong reflection characteristics of the corner reflector, the black code unit forms a strong reflection for the sound wave vertically incident by the side-scan sonar. The back surface between the corner reflector units is a foam backboard to increase the impedance mismatch of the vertically incident sound wave on the reflecting surface and fully enhance the reflection of each face of the corner reflector. The concave surface of the corner reflector unit is filled with silicone gel and covered with gauze, so that it neither affects the transmission and scattering of the incident sound wave nor allows external debris to accumulate in the corner reflector unit. Each white code unit of the acoustic QR code identification plate is composed of a composite stack of a sound-absorbing panel and a carbon fiber board. The sound-absorbing panel uses a rubber-like strong sound-absorbing material, so that the white board has both strong sound-absorbing and sound-transmitting characteristics and a certain strength to ensure the planar configuration of the identification plate.

[0009] The acoustic QR code is in the shape of a regular quadrilateral composed of small quadrilateral units. It is divided into a positioning area, a content area, and a verification area according to functions, and there are a total of n 2A grid unit. The positioning area is the larger black codes at the three corners of the QR code, with a total of 3 units. After imaging processing the sonar echo, the image position of the QR code can be determined using the three black code areas, and further adjust the QR code attitude according to the relative positions of the three black code areas, without being interfered by the seabed background, realizing fast and stable feature reading.

[0010] The content area is the non-diagonal units except for the positioning area, with a total of (n 2 -n - 2) units. According to the computer binary rule, the longitude and latitude coordinates of the vehicle or the underwater identification plate number are transformed into a binary indicator composed of 1s and 0s, and the QR code in the content area of the acoustic QR code is assigned the coordinate binary indicator in row and column order. After calculation according to the number of bits, the longitude and latitude coordinates of the vehicle are obtained, or the positioning station number is obtained, and the longitude and latitude coordinates of the vehicle are found accordingly. The QR code is symmetrically distributed and encoded repeatedly in the horizontal and vertical directions to improve the decoding error tolerance. The number of information units that can be encoded is (n 2 -n - 2) / 2. When the colors of the two sides of the code are the same, this position is considered correct; when the two sides of the code are different, the probability of it being a black code is considered greater than that of a white code, and its uncertainty is recorded. The binary symbol sorting on both sides of the diagonal corresponds one by one with the diagonal as the axis of symmetry.

[0011] The verification area is the units except for one black code in the positioning area at the diagonal, with a total of n - 1 units. After converting the binary at the diagonal to a decimal number, the sum of the last few decimal digits of the encoded content is verified and modified to further improve the error tolerance. According to the number of diagonal encoding units (n - 1), the maximum decimal number (2n - 1) that can be obtained from its binary is used to determine whether the mantissa of the decimal number of the encoded content is consistent. When the mantissas are inconsistent, the black and white situations of all uncertain units in the content area are statistically analyzed, and various results are compared with the results in the diagonal area to judge the decoding result with the highest probability.

[0012] The sonar positioning device consists of a side-scan sonar and a signal decoder. The side-scan sonar is installed at the bottom of the underwater vehicle, emits a sound wave beam downward and receives the bottom echo signal. After imaging processing, a sonar image is obtained, and then decoded by the signal decoder to realize the identification of the acoustic QR code identification plate and obtain underwater positioning and navigation information.

[0013] The side-scan sonar can adopt a relatively mature and stable micro-miniature externally suspended integrated side-scan sonar, which can be mounted on various underwater unmanned platforms such as AUV, UUV, ROV, underwater gliders, surface unmanned boats, and various small carriers. It emits high-frequency single-frequency or frequency-modulated signal narrow beams, scans the bottom during the navigation along the track direction, receives the bottom echo and clearly images the underwater acoustic QR code identification plate and the terrain through signal processing. It has the advantages of small size, light weight, and low power consumption. Its sonar image is transmitted to the signal decoder for secondary processing.

[0014] The signal decoder performs secondary processing on the sonar image obtained by the side-scan sonar. First, it locates the QR code image according to the positioning area of the QR code, adjusts the attitude of the QR code according to the relative positions of the three black code areas, and then constructs an indicator composed of 1s and 0s from the black and white codes in the content area of the QR code in row and column order, calculates the number of bits according to the computer binary rule to obtain the longitude and latitude coordinates of the vehicle, or obtains the underwater sign number and looks up the longitude and latitude coordinates of the vehicle correspondingly, so as to realize the positioning and navigation of the underwater vehicle.

[0015] A method for positioning and navigation using the above underwater vehicle positioning and navigation device, the method comprising the following steps:

[0016] 1) Design an acoustic QR code according to the positioning coordinates. The acoustic QR code is divided into a positioning area, a content area and a verification area. The longitude and latitude coordinates of the location to be positioned or the positioning station number are converted into a binary indicator composed of 1s and 0s according to the number of bits, and black and white codes are assigned to the content area of the acoustic QR code in row and column order, and encoded repeatedly in the horizontal and vertical directions to improve the decoding error tolerance rate. Three corner areas of the regular quadrilateral of the acoustic QR code are set as black codes, which are positioning areas, so as to use the three black code areas to determine the image position of the QR code.

[0017] 2) Design the unit size of the acoustic QR code sign. The acoustic QR code sign is composed of square grids representing black and white codes. The side length of each square is not less than the resolution in the track direction and the resolution in the direction perpendicular to the track of the side-scan sonar to distinguish black and white code units. The resolution in the track direction and the resolution in the direction perpendicular to the track are determined by factors such as the speed, navigation depth, frequency and beam width.

[0018] 3) Make an acoustic QR code sign according to the QR code and place it at the underwater sign at the bottom of the waterway. Each black code unit is composed of a two-dimensional array constructed by arranging multiple corner reflector units side by side. The corner reflector is a concave tetrahedron constructed by three titanium alloy faces, which has the advantages of high strength and corrosion resistance and is suitable for long-term placement in seawater. The vertically incident sound wave is scattered multiple times on the three faces of the corner reflector unit and then generates an echo enhancement effect through phase interference. Using the strong reflection characteristic of the corner reflector, the black code unit forms a strong reflection on the sound wave incident vertically by the side-scan sonar. The back tetrahedron gaps between the corner reflector units are filled with foam to improve the impedance mismatch of the vertically incident sound wave on the reflecting surface and fully enhance the reflection of each face of the corner reflector. The surface of the black code unit is covered with gauze to prevent external debris from accumulating in the corner reflector unit but does not affect the transmission and scattering of the incident sound wave. Each white code unit of the acoustic QR code sign is composed of a composite stack of a sound absorption panel and a carbon fiber board. The sound absorption panel uses a rubber-like strong sound absorption material, so that the white board has both strong sound absorption and sound transmission characteristics and a certain strength to ensure the planar configuration of the sign.

[0019] 4) Select a relatively mature and stable micro-miniature externally suspended integrated side-scan sonar, and mount it under the side of the underwater vehicle carrier that requires positioning and navigation, such as various underwater unmanned platforms AUV, UUV, ROV, underwater gliders, surface unmanned boats, and various small carriers. During the navigation of the underwater vehicle along the track direction, the bottom of the water is scanned, and high-frequency single-frequency or frequency-modulated signal narrow beams are continuously emitted to receive the bottom echo.

[0020] 5) Denoise and extract the edges of the narrow beam echo by methods such as median filtering, transform domain filtering, and image morphological filtering, and enhance the image of the target area to obtain a real-time clear image of the underwater acoustic QR code identification sign and the terrain, so as to perform QR code positioning and decoding processing.

[0021] 6) The signal decoder performs secondary processing on the sonar image obtained by the side-scan sonar. First, the QR code is image-located according to the positioning area of the QR code, and the attitude of the QR code is adjusted according to the relative positions of the three black code areas. Then, the black and white codes in the content area of the QR code are constructed into indicators composed of 1 and 0 in row and column order, and their bit numbers are calculated according to the computer binary rules to obtain the longitude and latitude coordinates of the vehicle, or obtain the underwater identification sign number, and find the longitude and latitude coordinates of the vehicle correspondingly, so as to realize the positioning and navigation of the underwater vehicle.

[0022] The present invention has the following advantages:

[0023] (1) The two-dimensional coding design of the present invention is flexible, has a large storage capacity, and strong fault tolerance ability;

[0024] (2) The present invention belongs to a passive identification device. The underwater coding device does not need to carry an active sound source, has a small space occupancy rate, is convenient for laying on the bottom of the water and can be static for a long time, and has the characteristics of stable, lasting and accurate positioning;

[0025] (3) The present invention uses the corner reflector echo enhancement technology, the echo is stable and easy to detect, the decoding success rate is high, and the acoustic positioning reliability is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is the schematic diagram of the acoustic positioning and navigation system of the underwater vehicle provided by the embodiment of the present invention;

[0027] Figure 2 It is the schematic diagram of the underwater acoustic QR code identification sign provided by the embodiment of the present invention;

[0028] Figure 3 It is the flowchart of the underwater vehicle positioning and navigation based on the underwater acoustic QR code identification sign provided by the embodiment of the present invention;

[0029] Figure 4The encoding result of the underwater acoustic QR code sign provided by the embodiment of the present invention. (a) is a full-grid acoustic QR code, and (b) is an example of an acoustic QR code;

[0030] Reference numerals in the figure: 1, acoustic QR code sign; 2, sonar positioning device; 3, underwater vehicle; 4, side-scan sonar; 5, signal decoder; 6, black code; 7, white code; 8, two-dimensional array of corner reflectors; 9, silicone gel; 10, foam backboard; 11, gauze; 12, sound-absorbing panel; 13, carbon fiber board. Specific embodiments

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0032] Please refer to Figure 1 , the present invention is an underwater vehicle positioning and navigation device based on an acoustic QR code. The device includes an acoustic QR code sign 1 and a sonar positioning device 2. The sonar positioning device 2 is mounted on the underwater vehicle 3 and processes and analyzes the received echo of the acoustic QR code sign 1 by emitting sound waves to obtain underwater positioning and navigation information.

[0033] The described acoustic QR code sign 1 is placed at the bottom of the water. The device is composed of a plurality of black code 6 and white code 7 units, forming a planar, black-and-white, graphic for recording data symbol signals. The black code represents "1" during encoding, and the white code represents "0" during encoding. The black code 6 and the white code 7 are arranged in a certain form to form a matrix QR code, which encodes by different distributions of black and white pixels in a rectangular space. At the corresponding element positions of the matrix, the appearance of a dot represents binary "1", and the non-appearance of a dot represents binary "0". The arrangement and combination of the dots determine the meaning represented by the matrix QR code.

[0034] The surface of the described acoustic QR code sign 1 is divided into square grids representing the black code 6 and the white code 7. The side length of each square is not less than the resolution in the track direction and the resolution in the direction perpendicular to the track of the side-scan sonar 4 to distinguish the black code and white code units. The resolution in the track direction and the resolution in the direction perpendicular to the track are determined by factors such as the speed, navigation depth, frequency, and beam width.

[0035] Each black code unit 6 of the acoustic QR code sign 1 is composed of a two-dimensional array constructed by arranging multiple corner reflector units side by side, that is, the corner reflector two-dimensional array 8. The corner reflector is a concave tetrahedron constructed by three titanium alloy surfaces, which has the advantages of high strength and corrosion resistance and is suitable for long-term deployment in seawater. The vertically incident sound wave is scattered multiple times on the three surfaces of the corner reflector unit and then produces an echo enhancement effect through phase interference. Using the strong reflection characteristics of the corner reflector, the black code unit strongly reflects the sound wave incident vertically by the side-scan sonar. The concave surface of the corner reflector unit is filled with silica gel 9, and the surface is covered with gauze 11, so that it does not affect the transmission and scattering of the incident sound wave and also prevents external sundries from accumulating in the corner reflector unit. The back of the corner reflector unit includes a foam backboard 10 at the tetrahedral void to increase the impedance mismatch of the vertically incident sound wave on the reflection surface and fully enhance the reflection of each surface of the corner reflector. Each white code unit 7 of the acoustic QR code sign 1 is composed of a composite superposition of a sound absorption panel 12 and a carbon fiber board 13. The sound absorption panel uses a rubber-like strong sound absorption material, so that the white board 7 has both strong sound absorption and sound transmission characteristics and a certain strength to ensure the planar configuration of the sign, such as Figure 2 shown.

[0036] Figure 4 This is the encoding result of the underwater acoustic QR code sign provided by the embodiment of the present invention. As shown in the figure, the acoustic QR code sign 1 is divided into a positioning area, a content area, and a verification area according to functions, and there are a total of n 2 grid units. In this embodiment, n = 5 is taken as an example, that is, 25 grid units. The positioning area is the larger black codes at the three corners of the QR code, with a total of 3 units. By processing the sonar image, the image position of the QR code can be determined by using the three black code areas. Further, the attitude of the QR code can be adjusted according to the relative positions of the three black code areas, without being interfered by the seabed background, and fast and stable feature reading can be realized. The content area is the non-diagonal units except the positioning area, with a total of (n 2 -n-2) units. The longitude and latitude coordinates of the vehicle can be directly obtained by decoding, or the vehicle longitude and latitude coordinates can be obtained by corresponding to the positioning station number. The verification area is the units except one black code in the positioning area at the diagonal, with a total of n-1 units, which verifies and modifies the encoded content to further improve the error tolerance rate.

[0037] The described sonar positioning device 2 is composed of a side-scan sonar 4 and a signal decoder 5. The side-scan sonar 4 is installed at the bottom of the underwater vehicle 3, emits sound pulses downward and receives the bottom echo signal. After signal processing, a sonar image is obtained, and then decoded by the signal decoder to realize the identification of the acoustic QR code sign 1 and obtain underwater positioning and navigation information.

[0038] The side-scan sonar 4 can adopt a relatively mature and stable micro-miniature externally suspended integrated side-scan sonar, which can be mounted on various underwater unmanned platforms such as AUVs, UUVs, ROVs, underwater gliders, surface unmanned vessels, and various small carriers. It emits high-frequency single-frequency or frequency-modulated signal narrow beams, scans the bottom of the water during the navigation along the track direction, receives the bottom echo, and clearly images the underwater acoustic QR code identification plate and the terrain through signal processing. It has the advantages of small size, light weight, and low power consumption. Its sonar image is transmitted to the signal decoder for secondary processing.

[0039] The signal decoder 5 performs secondary processing on the sonar image obtained by the side-scan sonar. First, it locates the QR code image according to the positioning area of the QR code, adjusts the posture of the QR code according to the relative positions of the three black code areas, and then constructs an indicator composed of 1 and 0 from the black and white codes in the content area of the QR code in row and column order, calculates the number of bits according to the computer binary rule, obtains the longitude and latitude coordinates of the vehicle, or obtains the underwater identification plate number, and looks up the longitude and latitude coordinates of the vehicle correspondingly to achieve the positioning and navigation of the underwater vehicle.

[0040] A method for positioning and navigation using the above-mentioned underwater vehicle positioning and navigation device based on acoustic QR codes, the method comprising the following steps:

[0041] 1) Design an acoustic QR code according to the positioning coordinates. The acoustic QR code is divided into a positioning area, a content area, and a verification area. The positioning area is the larger black codes at the three corners of the acoustic QR code, a total of 3 units, which are used to determine the image position of the QR code by using the three large black code areas. The content area is the remaining non-diagonal units except the positioning area, a total of (n 2 -n-2) units, which are used to record the positioning information of the underwater vehicle. The verification area is the units at the diagonal except one black code in the positioning area, a total of n-1 units, which are used to verify and modify the content area to further improve the error tolerance rate.

[0042] 2) Convert the longitude and latitude coordinates or the positioning station number at the location to be positioned into a binary indicator composed of 1 and 0 according to the number of bits, assign the black and white codes to the content area of the acoustic QR code in row and column order, and repeat the encoding in the horizontal and vertical directions to improve the decoding error tolerance rate. Convert the sum of the last few decimal digits of the encoded content into binary and assign it to the verification area unit at the diagonal. Assume that the positioning station number is 370, its binary code is 101110010, a total of 9 bits. According to the number of encodable information units in the content area (n 2-(n - 2) / 2, the scale of the QR code n≥5 is obtained. Therefore, the QR code n = 5 can be designed. The total number of units in the content area is 18, the number of units that can be encoded with information is 9, and the total number of units in the verification area is 4. The content area is designed with symmetric coding as 101110010. Since the sum of the last two digits of the positioning station number is 7, the coding of the verification area is designed as 0111.

[0043] 3) Design the unit size of the acoustic QR code sign. The acoustic QR code sign is composed of a small square grid representing black and white codes. The side length of each square is not less than the resolution in the along-track direction and the resolution in the cross-track direction of the side-scan sonar to distinguish black and white code units. The resolution in the along-track direction and the resolution in the cross-track direction are determined by factors such as the speed, navigation depth, frequency, and beam width.

[0044] 4) Produce the acoustic QR code sign according to the QR code and place it at the underwater sign position of the waterway. Each black code unit is composed of a two-dimensional array constructed by arranging multiple corner reflector units side by side. The corner reflector is a concave tetrahedron constructed by three titanium alloy faces, which has the advantages of high strength and corrosion resistance and is suitable for long-term deployment in seawater. The vertically incident sound wave is scattered multiple times on the three faces of the corner reflector unit and then produces an echo enhancement effect through phase interference. Using the strong reflection characteristic of the corner reflector, the black code unit forms a strong reflection on the sound wave vertically incident by the side-scan sonar. The concave surface of the corner reflector unit is filled with silicone gel, and the surface is covered with gauze 11, so that it does not affect the transmission and scattering of the incident sound wave and also avoids the accumulation of external debris in the corner reflector unit. The back surface between the corner reflector units includes a tetrahedral void filled with a foam backboard to improve the impedance mismatch of the vertically incident sound wave on the reflecting surface and fully enhance the reflection of each face of the corner reflector. Each white code unit of the acoustic QR code sign is composed of a composite stack of an acoustic absorption panel and a carbon fiber board. The acoustic absorption panel uses a rubber-like strong acoustic absorption material, so that the white board has both strong acoustic absorption and sound transmission characteristics and a certain strength to ensure the planar configuration of the sign.

[0045] 5) Select a relatively mature and stable micro-miniature externally suspended integrated side-scan sonar and mount it under the side of the underwater vehicle carrier that needs positioning and navigation, such as various types of underwater unmanned platforms AUV, UUV, ROV, underwater gliders, surface unmanned ships, and various small carriers. During the underwater vehicle's navigation along the track direction, it scans the water bottom and continuously emits high-frequency single-frequency or frequency-modulated signal narrow beams and receives the water bottom echo.

[0046] 6) The signal decoder performs denoising and edge extraction on the narrow beam echo through methods such as median filtering, transform domain filtering, and image morphological filtering, and performs image enhancement on the target area to obtain a real-time clear image of the underwater acoustic QR code sign and the terrain for QR code positioning and decoding processing.

[0047] 7) The signal decoder performs secondary processing on the sonar image obtained by the side-scan sonar. First, it finds the QR code area and adjusts its posture. The black codes in the located area have a larger unit area than ordinary black code units. It performs image positioning on the QR code and adjusts the posture of the QR code according to the relative positions of the three black code areas.

[0048] 8) Then, it identifies the black and white codes in the content area of the QR code, constructs an indicator composed of 1s and 0s in row and column order. The binary symbols on both sides of the diagonal are sorted in one-to-one correspondence with the diagonal as the axis of symmetry, obtains its binary number (101110010), and compares the binary numbers on both sides of the diagonal bit by bit. When the binary symbols are the same, the bit symbol is considered correct; when the symbols on both sides are different, the probability of it being 1 is greater than 0, and its uncertainty is recorded. It calculates the number of bits according to the computer binary rule to obtain the longitude and latitude coordinates of the vehicle, or obtains the underwater identification plate number, and correspondingly looks up the longitude and latitude coordinates of the vehicle to achieve the positioning and navigation of the underwater vehicle.

[0049] 9) It identifies the QR code in the verification area, converts the binary number (0111) at the diagonal to a decimal number (7), verifies and modifies the sum of the last two digits of the decimal number (370) of the encoded content to further improve the error tolerance rate. According to the number of diagonal encoding units 4, the maximum decimal number 15 that can be obtained from its binary is used to determine whether the mantissa of the decimal number of the encoded content is consistent. When the mantissas are inconsistent, it statistically analyzes the black and white situations of all uncertain units in the content area, compares various results with the results in the diagonal area to determine the decoding result with the highest probability. It verifies or corrects the decoding result information in the content area, gives the probability statistics of the longitude and latitude coordinates of the vehicle or the positioning station number, and realizes the positioning and navigation of the underwater vehicle.

[0050] Experiments show that the two-dimensional coding of the present invention has flexible design, large information storage capacity, and strong error tolerance. The underwater coding device does not need to carry an active sound source, has a small space occupancy rate, is convenient for laying on the bottom of the water and staying static for a long time, has the characteristics of stable, lasting, and accurate positioning, uses the corner reflector echo enhancement technology, the echo is stable and easy to detect, and has the advantages of high decoding success rate and good acoustic positioning reliability.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. An underwater vehicle positioning and navigation device based on an acoustic QR code, characterized in that, Including: An acoustic QR code identification plate placed at the bottom of the water and a sonar positioning device mounted on an underwater vehicle; The acoustic QR code identification plate is a pattern structure of alternating black and white square grids composed of multiple black code units and white code units. The black code units are formed by arranging multiple corner reflector units side by side. Each corner reflector unit produces an echo enhancement effect on the incident sound wave in the vertical direction and carries position information, positioning station number information, and / or the longitude and latitude coordinates of the vehicle; The sonar positioning device is used to emit a beam to scan the waterway, receive the echo of the acoustic QR code identification plate, and perform processing and analysis to obtain the longitude and latitude coordinate information of the underwater vehicle; The sonar positioning device includes a side-scan sonar and a signal decoder. The side-scan sonar is installed at the bottom of the underwater vehicle, emits a sound wave beam downward, and receives the bottom echo signal. After imaging processing, a sonar image is obtained. The signal decoder decodes the sonar image to identify the acoustic QR code identification plate and obtain underwater positioning and navigation information; The acoustic QR code identification plate is composed of multiple black code units and white code units, forming a planar, black-and-white, graphic that records data symbol signals. The black code units and white code units are arranged in a certain form to form a matrix acoustic QR code, which is encoded by the different distributions of black and white pixels in the matrix in a rectangular space. The black code represents "1" during encoding, and the white code represents "0" during encoding. At the corresponding element positions in the matrix, the appearance of a dot represents binary "1", and the non-appearance of a dot represents binary "0"; The side lengths of the black code units and white code units are not less than the resolution in the track direction and the resolution in the direction perpendicular to the track of the side-scan sonar to distinguish the black code units and white code units.

2. The underwater vehicle positioning and navigation device based on an acoustic QR code according to claim 1, characterized in that, The black code unit is formed by arranging multiple corner reflector units into a two-dimensional array, that is, a corner reflector two-dimensional array. The corner reflector is a concave tetrahedron constructed by three titanium alloy surfaces, with silicon gel filled in the concave surface, gauze covered on the surface, and a foam backboard provided on the back and in the gaps of the tetrahedron.

3. The underwater vehicle positioning and navigation device based on an acoustic QR code according to claim 1, characterized in that, The white code unit is composed of a composite superposition of an acoustic absorption panel and a carbon fiber board. The acoustic absorption panel is made of a rubber-like strong acoustic absorption material.

4. The underwater vehicle positioning and navigation device based on an acoustic QR code according to claim 1, characterized in that, The acoustic QR code is a regular quadrilateral composed of n 2 black code units and white code units. Three corner units of the regular quadrilateral are black code units, and their unit areas are larger than those of all other units, serving as a positioning area for determining the image position of the acoustic QR code; The non-diagonal cells outside the positioning area serve as the content area, that is, (n 2 - n - 2) black code cells and white code cells are used to record the positioning information of the underwater vehicle; The diagonal units except the positioning area are used as verification areas, that is, n - 1 black code units and white code units, for verifying and modifying the content area.

5. The underwater vehicle positioning and navigation device based on an acoustic QR code according to claim 4, characterized in that, The number of encodable information units in the content area, i.e., the number of black code units, is (n 2 - n - 2) / 2, and the black code units are symmetrically distributed with the diagonal as the axis.

6. An underwater vehicle positioning and navigation method based on an acoustic QR code, characterized in that, Including the following steps: S1. Design an acoustic QR code: S1.1 Convert the longitude and latitude coordinates or the positioning station number at the location to be positioned into a binary indicator composed of 1s and 0s according to the number of bits, determine the number of bits m of the binary indicator, and obtain the scale n of the acoustic QR code, that is, n ≥ m / 2; S1.2 Use n 2 grid cells to form a regular quadrilateral, where three corner cells are black code cells, and their cell areas are larger than all other cells, serving as a positioning area for identifying the position of the acoustic QR code for further decoding; Use non-diagonal cells outside the positioning area as the content area, where the number of black code cells is (n 2 - n-2) / 2, and the black code cells are symmetrically distributed with the diagonal as the axis. Convert the longitude and latitude coordinates or the positioning station number at the location to be positioned into a binary indicator composed of 1s and 0s according to the number of bits, and assign black and white codes to the content area in row and column order for encoding in the horizontal and vertical directions; Use the diagonal units except the positioning area as verification areas, convert the sum of the last few decimal digits of the encoded content into binary, and assign it to the verification area units at the diagonal; S2. Design and manufacture an acoustic QR code identification plate: S2.1 The side length of the grid cell is not less than the resolution in the track direction and the resolution in the direction perpendicular to the track of the side-scan sonar to distinguish the black code cells and the white code cells. The resolution in the track direction and the resolution in the direction perpendicular to the track are determined by the ship speed, the navigation depth, the frequency, and the beam width. S2.2 Each black code cell consists of a two-dimensional array constructed by arranging multiple corner reflector units side by side. The corner reflector is a concave tetrahedron constructed by three titanium alloy faces. The concave surface of the corner reflector unit is filled with silicone gel, and the surface is covered with gauze. The back surface between the corner reflector units includes a tetrahedral gap filled with a foam backboard. Each white code cell is composed of a composite stack of an acoustic absorption panel and a carbon fiber board. The acoustic absorption panel is made of a rubber-like strong acoustic absorption material. S2.3 Place the acoustic QR code sign at the bottom of the water. S3 Obtain the echo signal and process it to obtain a sonar image: S3.1 Mount the side-scan sonar under the side of the underwater vehicle that needs to be positioned and navigated. During the underwater vehicle's navigation along the track direction, the side-scan sonar of the sonar positioning device scans the bottom of the water and continuously emits high-frequency single-frequency or frequency-modulated signal narrow beams to receive the echo of the acoustic QR code sign at the bottom of the water. S3.2 The side-scan sonar denoises and extracts the edges of the echo, and enhances the image of the target area to obtain a real-time clear image of the underwater acoustic QR code sign and the terrain. S4. Locate and decode the acoustic QR code to achieve positioning and navigation: S4.1 Locate the acoustic QR code. According to the positioning area of the acoustic QR code, perform image positioning on the acoustic QR code, and adjust the attitude of the acoustic QR code according to the relative positions of the three black code cells in the positioning area. S4.2 Identify the black code cells and white code cells in the content area of the acoustic QR code, and construct an indicator composed of 1s and 0s in row and column order. S4.3 Calculate the number of bits according to the computer binary rule to obtain the longitude and latitude coordinates of the underwater vehicle, or obtain the number of the underwater acoustic QR code sign, and look up the longitude and latitude coordinates of the underwater vehicle correspondingly to achieve the positioning and navigation of the underwater vehicle.

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