An underwater wireless optical communication cooperative target pose measurement method

Abstract

The present invention discloses a method for measuring the pose of a cooperative target in underwater wireless optical communication, comprising: constructing a pose measurement system; keeping two underwater wireless optical communication terminals at a predetermined distance to obtain an identifier serving as the decision basis for the image of the underwater wireless optical communication light source; turning on the underwater light array, the underwater color camera, and the two underwater wireless optical communication terminals, using the underwater color camera to capture the image of the second underwater light array and performing interference filtering processing to obtain a filtered image; performing grayscale processing and Gaussian filtering on the filtered image; obtaining the centroid coordinates of each light spot in the filtered image; obtaining the central pose of the underwater light array according to the centroid coordinates of each light spot; and obtaining the relative pose of the two underwater wireless optical communication terminals according to the pose of the center of the underwater light array. By integrating the visual guidance measurement technology and the underwater wireless optical communication system, the present invention solves the problem of pose measurement of the cooperative target in underwater wireless optical communication, with low complexity.

Description

Technical Field

[0001] The present invention belongs to the technical field of underwater wireless communication, and particularly relates to a method for measuring the pose of a cooperative target in underwater wireless optical communication. Background Art

[0002] Underwater communication is crucial for ocean engineering applications. At present, the commonly used underwater data transmission means are mainly divided into two types: wired communication and underwater acoustic communication. Among them, wired communication uses cables or optical fibers laid on the seabed as the medium to transmit information, and has the advantage of high bandwidth; however, this communication method must rely on cables and has poor mobility. Underwater acoustic communication uses sound waves as the carrier and realizes information transmission through the transmission of acoustic signals in water, and has the characteristics of long transmission distance and strong mobility; however, limited by the acoustic wave bandwidth and background noise, the transmission rate of this communication method is relatively low, generally only in the order of Kbps, and there are limitations in the transmission of large-capacity information.

[0003] In recent years, underwater wireless optical communication with blue and green light as the information carrier has attracted extensive attention at home and abroad due to its outstanding advantages such as high transmission rate, low latency, light weight, small volume and low power consumption. Combining this technology with an underwater robot platform can solve engineering problems such as in-situ data recovery on the seabed, and has become an important development direction in the field of ocean communication. In engineering applications, due to the characteristics of local coverage and directional transmission of underwater wireless optical communication, a stable transmission link can only be established when the communication terminals enter each other's optical signal coverage area and are aligned with each other. Therefore, when an underwater wireless optical communication device is mounted on a robot platform, the robot must first swim near the cooperative target and sense information such as the distance and azimuth of the cooperative target in order to align with the communication terminal. This is a prerequisite for the underwater wireless optical communication system to achieve data transmission.

[0004] There are mainly two common ways to establish an underwater wireless optical communication link: one is to establish a transmission link based on a capture and tracking system, and the other is to establish a transmission link using visual guidance. When establishing a transmission link based on a capture and tracking system, a set of complex opto-mechanical devices must be installed in the communication terminal to be able to sense the orientation of the communication light in real time and adjust the pointing of the communication light. This communication method is relatively mature in the field of space laser communication. However, due to factors such as water quality environment and water sealing, it is currently difficult to apply underwater. Establishing a transmission link using visual guidance means installing an underwater camera on a mobile platform and installing lights with a certain pattern on the cooperative target terminal. During operation, the mobile platform first measures the orientation of the cooperative target through underwater acoustic positioning technology and swims near the cooperative target; then, within a short distance range, it takes pictures of the cooperative target's light pattern through the camera, senses the target orientation by analyzing the shape characteristics of the pattern captured by the camera, and adjusts its own posture so that the two communication terminals are within each other's communication range; finally, when designing the wireless optical communication system, the divergence angle of the light emitted by the transmitter and the receiving field of view of the receiver are increased to reduce the requirement for azimuth alignment of the communication link. During this process, taking pictures of the cooperative target's light pattern with the camera and calculating the orientation of the cooperative target are the key links in establishing the channel link.

[0005] Regarding the problem of taking pictures of the cooperative target's light pattern with the camera and calculating the orientation of the cooperative target, the related technologies mainly adopt the visual guidance method commonly used in the docking of underwater vehicles, that is, using a monocular or binocular camera to take pictures of the light pattern around the cooperative target and using the PNP (Perspective-n-Points) algorithm to calculate the target pose. During this process, since the wavelengths of the lights used by the cooperative target and the communication light source are both in the visible light band, there will be interference between them when the optical communication device and the visual guidance device work simultaneously. Regarding the influence of the visual guidance light on the wireless optical communication system, as long as the communication wavelength is different from the wavelength of the guidance light and an optical filter is added to the communication receiver, this interference can be effectively suppressed. However, for visual pose measurement, since the communication light wave is usually in a stroboscopic state, it will cause difficulties in image recognition and affect the pose measurement accuracy. Summary of the Invention

[0006] In order to solve the above problems existing in the prior art, the present invention provides a method for measuring the pose of a cooperative target in underwater wireless optical communication. The technical problems to be solved by the present invention are realized through the following technical solutions:

[0007] The present invention provides a method for measuring the pose of a cooperative target in underwater wireless optical communication, including:

[0008] S1: Construct an underwater wireless optical communication cooperative target pose measurement system, where the system includes an underwater robot and an underwater cooperative target support platform. Among them, the underwater robot is used to carry a first underwater wireless optical communication terminal, an underwater color camera, and an underwater image processing module, and the underwater cooperative target support platform is used to carry a second underwater wireless optical communication terminal and an underwater light array;

[0009] S2: Keep the first underwater wireless optical communication terminal and the second underwater wireless optical communication terminal at a predetermined distance, turn on the underwater light array and the underwater wireless optical communication light source respectively, and obtain the identifier of the decision basis for the underwater wireless optical communication light source image;

[0010] S3: Turn on the underwater light array, the underwater color camera, the first underwater wireless optical communication terminal, and the second underwater wireless optical communication terminal, and use the underwater color camera to capture the image of the second underwater light array.

[0011] S4: Process the image of the second underwater light array, filter out the underwater wireless optical communication light interference in the image of the second underwater light array, and obtain the filtered image;

[0012] S5: Perform gray processing and Gaussian filtering on the filtered image to obtain the filtered image;

[0013] S6: Obtain the centroid coordinates of each light spot in the filtered image;

[0014] S7: According to the centroid coordinates of each light spot, obtain the pose of the underwater light array relative to the underwater color camera;

[0015] S8: According to the pose of the center of the underwater light array, obtain the relative pose of the two underwater wireless optical communication terminals.

[0016] In an embodiment of the present invention, the first underwater wireless optical communication terminal includes a first underwater wireless optical communication transmitter and a first underwater wireless optical communication receiver, and the light emitting surface of the first underwater wireless optical communication transmitter, the receiving surface of the first underwater wireless optical communication receiver, and the receiving surface of the underwater color camera are located on the same plane;

[0017] The second underwater wireless optical communication terminal includes a second underwater wireless optical communication transmitter and a second underwater wireless optical communication receiver, and the light emitting surface of the second underwater wireless optical communication transmitter, the receiving surface of the second underwater wireless optical communication receiver, and the light emitting surface of the underwater light array are located on the same plane;

[0018] The first underwater wireless optical communication transmitter is used to send wireless optical communication signals into the water. The first underwater wireless optical communication receiver is used to receive underwater wireless optical communication signals. The second underwater wireless optical communication transmitter is used to send communication optical signals to the first underwater wireless optical communication receiver. The second underwater wireless optical communication receiver is used to receive communication optical signals from the first underwater wireless optical communication transmitter.

[0019] In an embodiment of the present invention, the first underwater wireless optical communication transmitter, the first underwater wireless optical communication receiver, the second underwater wireless optical communication transmitter, and the second underwater wireless optical communication receiver together constitute an underwater two-way wireless optical communication system. Moreover, the operating wavelength, spectral characteristics, and power used by the underwater light array and the underwater two-way wireless optical communication system are all different.

[0020] In an embodiment of the present invention, S2 includes:

[0021] S2.1: Only turn on the underwater light array, and use the underwater color camera to capture the first underwater light array image;

[0022] S2.2: Use the underwater image processing module to calculate the brightness R of each pixel in the RGB three color channels of the first underwater light array image 灯 (i, j), G 灯 (i, j), B 灯 (i, j), where i is the number of row pixels of the underwater color camera, and j is the number of column pixels of the underwater color camera;

[0023] S2.3: According to the brightness R of each pixel in the RGB three color channels 灯 (i, j), G 灯 (i, j), B 灯 (i, j), obtain the saturation S of each pixel in the first underwater light array image 灯 (i, j) and the average saturation s of all pixels 灯 ;

[0024] S2.4: Turn off the underwater light array and turn on the underwater wireless optical communication light source, and use the underwater color camera to capture the underwater wireless optical communication light source image. The underwater wireless optical communication light source includes the emission light sources of the first underwater wireless optical communication transmitter and the second underwater wireless optical communication transmitter;

[0025] S2.5: Use the underwater image processing module to calculate the brightness R of each pixel in the RGB three color channels of the underwater wireless optical communication light source image 通 (i, j), G 通 (i, j), B 通(i,j);

[0026] S2.6: Obtain the saturation S(i,j) of each pixel in the underwater wireless optical communication light source image according to the luminance R(i,j), G(i,j), and B(i,j); 通 (i,j), G 通 (i,j), B 通 and obtain the average saturation s of all pixels; 通 (i,j) and the average saturation s of all pixels; 通 ;

[0027] S2.7: Compare the average saturation s of all pixels in the first underwater light array image with the average saturation s of all pixels in the underwater wireless optical communication light source image to obtain the identifier B of the judgment basis: 灯 with the average saturation s of all pixels in the underwater wireless optical communication light source image 通 , and obtain the identifier B of the judgment basis:

[0028]

[0029] In an embodiment of the present invention, the S4 includes:

[0030] S4.1: The underwater image processing module acquires a second underwater light array image, and calculates the luminance R(i,j), G(i,j), and B(i,j) of each pixel in the RGB three color channels of the second underwater light array image, where i is the number of row pixels of the underwater color camera, and j is the number of column pixels of the underwater color camera;

[0031] S4.2: Calculate the saturation S(i,j) of each pixel in the second underwater light array image, the average saturation S of all pixels, avg and the maximum saturation S of all pixels according to the luminance R(i,j), G(i,j), and B(i,j) of each pixel in the RGB three color channels; max ;

[0032] S4.3: Calculate the threshold S using the average saturation S avg and the maximum saturation S max : th :

[0033]

[0034] S4.4: Clear the pixels according to the identifier B. If B = 0, clear all pixels with saturation S(i,j)>S th in the second underwater light array image; if B = 1, clear all pixels with saturation S(i,j)<S th in the second underwater light array image to obtain a filtered image.

[0035] In an embodiment of the present invention, S5 includes:

[0036] S5.1: Obtain the grayscale image g(i, j) of each pixel according to the brightnesses R'(i, j), G'(i, j), and B'(i, j) of the RGB three color channels of each pixel of the filtered image;

[0037] S5.2: Set the Gaussian filtering radius to n G , then the two-dimensional Gaussian kernel w G is a matrix with both length and width of 2 G + 1, and the element in the m-th row and n-th column is expressed as

[0038]

[0039] where m, n ∈ [1, 2n G + 1], and both m and n are integers;

[0040] S5.3: Normalize the two-dimensional Gaussian kernel w G to obtain the normalized two-dimensional Gaussian kernel W G :

[0041]

[0042] S5.4: Perform two-dimensional convolution on the grayscale image g(i, j) obtained in S5.1 and the normalized two-dimensional Gaussian kernel W G to obtain the grayscale image g1(, j) after Gaussian filtering:

[0043]

[0044] where p and q are both integers and satisfy

[0045]

[0046] In an embodiment of the present invention, S6 includes:

[0047] S6.1: Perform binarization processing on each pixel in the filtered image to obtain a binarized image;

[0048] S6.2: Use the connectivity algorithm to find all the light spots in the binarized image, and mark the coordinates of all the pixels included in the k-th light spot with (x ki , y ki ), where x ki represents the abscissa of the i-th pixel in the k-th light spot, and y ki represents the ordinate of the i-th pixel in the k-th light spot;

[0049] S6.3: Calculate the centroid coordinates of each light spot.

[0050] In one embodiment of the present invention, the S7 includes:

[0051] S7.1: An attitude estimation algorithm based on infinitesimal planes, using the centroid coordinates of all light spots, to obtain the rotation matrix R and the transformation vector t of the center of the underwater light array relative to the underwater color camera;

[0052] S7.2: Using the rotation matrix R and the transformation vector t to obtain the distance d, yaw angle θ Yaw , pitch angle θ Pitch and roll angle θ Roll .

[0053] Compared with the prior art, the beneficial effects of the present invention are:

[0054] 1. The underwater wireless optical communication cooperative target pose measurement method of the present invention solves the pose measurement problem of the underwater wireless optical communication cooperative target by integrating the visual guidance measurement technology and the underwater wireless optical communication system, with a simple structure, low complexity, easy combination with the underwater platform, and convenient for popularization and application.

[0055] 2. The underwater wireless optical communication cooperative target pose measurement method of the present invention suppresses the influence of communication lights on visual measurement through the saturation channel in the HSV color space, enabling the underwater wireless optical communication system and the pose measurement system to work simultaneously, and greatly improving the compatibility of the communication link establishment process and the two-way wireless optical communication process.

[0056] The following will further elaborate on the present invention in detail with reference to the drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 is a flowchart of an underwater wireless optical communication cooperative target pose measurement method provided by an embodiment of the present invention;

[0058] Figure 2 is a schematic diagram of an underwater wireless optical communication cooperative target pose measurement system provided by an embodiment of the present invention;

[0059] Figure 3 is a schematic diagram of a simulation experimental device of an underwater wireless optical communication cooperative target pose measurement method provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0060] In order to further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following provides a detailed description of an underwater wireless optical communication cooperative target pose measurement system and method according to the present invention with reference to the drawings and specific embodiments.

[0061] The foregoing and other technical contents, features and effects of the present invention will be clearly presented in the following detailed description of the specific embodiments in conjunction with the accompanying drawings. Through the description of the specific embodiments, a more in-depth and specific understanding of the technical means and effects adopted by the present invention to achieve the predetermined purpose can be obtained. However, the accompanying drawings are only for reference and illustration, and are not used to limit the technical solution of the present invention.

[0062] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant is intended to cover non-exclusive inclusion, so that an article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed. Without further limitation, an element defined by the statement "including a..." does not exclude the presence of another identical element in the article or device including the said element.

[0063] Please refer to Figure 1 , Figure 1 which is a flowchart of a method for measuring the pose of an underwater wireless optical communication cooperation target provided by an embodiment of the present invention. The pose measurement method includes:

[0064] S1: Construct an underwater wireless optical communication cooperation target pose measurement system, which includes an underwater robot and an underwater cooperation target support platform. Among them, the underwater robot is used to carry a first underwater wireless optical communication terminal, an underwater color camera and an underwater image processing module, and the underwater cooperation target support platform is used to carry a second underwater wireless optical communication terminal and an underwater light array.

[0065] Specifically, please refer to Figure 2 , Figure 2 which is a schematic diagram of an underwater wireless optical communication cooperation target pose measurement system provided by an embodiment of the present invention. The measurement system includes an underwater robot and an underwater cooperation target support platform.

[0066] The underwater robot is used to carry the first underwater wireless optical communication terminal, the underwater color camera and the underwater image processing module, enabling it to move in water. The underwater color camera operates in the visible light band and is used to capture images of underwater objects; the underwater image processing module is used to process the images captured by the underwater color camera to obtain the azimuth information of the second underwater wireless optical communication terminal. The first underwater wireless optical communication terminal includes a first underwater wireless optical communication transmitter and a first underwater wireless optical communication receiver. Among them, the first underwater wireless optical communication transmitter is used to send wireless optical communication signals into the water; the first underwater wireless optical communication receiver is used to receive underwater wireless optical communication signals.

[0067] As Figure 2 , the underwater cooperative target support platform is used to carry the second underwater wireless optical communication terminal. The underwater cooperative target support platform in this embodiment is formed by connecting a plurality of annular members with different diameters; an underwater light array is arranged on the largest annular member as the guiding light for the underwater color camera. The underwater light array is composed of no less than four underwater LED lights. The light-emitting surfaces of all LED lights are located on the same plane, and the centers of the light-emitting surfaces form a regular polygon. The second underwater wireless optical communication terminal includes a second underwater wireless optical communication transmitter and a second underwater wireless optical communication receiver. The second underwater wireless optical communication transmitter is used to send communication optical signals to the first underwater wireless optical communication receiver, and the second underwater wireless optical communication receiver is used to receive the communication optical signals from the first underwater wireless optical communication transmitter 6.

[0068] The first underwater wireless optical communication transmitter, the first underwater wireless optical communication receiver, the second underwater wireless optical communication transmitter, and the second underwater wireless optical communication receiver together constitute an underwater two-way wireless optical communication system, and the communication transmitted optical signal has a large divergence angle, and the communication receiver has a large receiving field of view. In this embodiment, the light-emitting surface of the first underwater wireless optical communication transmitter, the receiving surface of the first underwater wireless optical communication receiver, and the receiving surface of the underwater color camera are located on the same plane; the light-emitting surface of the second underwater wireless optical communication transmitter, the receiving surface of the second underwater wireless optical communication receiver, and the light-emitting surface of the underwater light array are located on the same plane.

[0069] During the actual operation process, the first underwater wireless optical communication transmitter, the first underwater wireless optical communication receiver, and the underwater color camera are installed according to the orientation when the first underwater wireless optical communication terminal actually works, so that the light-emitting surface of the first underwater wireless optical communication transmitter, the receiving surface of the first underwater wireless optical communication receiver, and the receiving surface of the underwater color camera are located on the same plane; the second underwater wireless optical communication transmitter, the second underwater wireless optical communication receiver, and the underwater light array are installed according to the orientation when the second underwater wireless optical communication terminal actually works, so that the light-emitting surface of the second underwater wireless optical communication transmitter, the receiving surface of the second underwater wireless optical communication receiver, and the light-emitting surface of the underwater light array are located on the same plane.

[0070] Furthermore, the underwater color camera in this embodiment can sense the brightness of the RGB (red, green, blue) three color channels of the image, and each of the RGB channels has 256 levels of brightness, which are respectively represented by the numbers 0, 1, 2... 255. The working wavelengths, spectral characteristics, and powers used by the underwater light array and the underwater two-way wireless optical communication system are different, resulting in an obvious difference in saturation in the underwater color camera between the two.

[0071] S2: Keep the first underwater wireless optical communication terminal and the second underwater wireless optical communication terminal at a predetermined distance, turn on the underwater light array and the underwater wireless optical communication light source respectively, and obtain the identifier of the judgment basis for the underwater wireless optical communication light source image.

[0072] Specifically, step S2 of this embodiment includes:

[0073] S2.1: Only turn on the underwater light array, and use the underwater color camera to take an image of the first underwater light array;

[0074] S2.2: Use the underwater image processing module to calculate the brightness R of each pixel in the RGB three color channels of the first underwater light array image 灯 (i, j), G 灯 (i, j), B 灯 (i, j), where i is the number of the row pixel of the underwater color camera, and the value is an integer within [1, M], j is the number of the column pixel of the underwater color camera, and the value is an integer within [1, N], M and N are the total number of pixel rows and columns respectively, and R 灯 (i, j), G 灯 (i, j), B 灯 (i, j) is an integer within the value range of [0, 255];

[0075] S2.3: According to the brightness R of each pixel in the RGB three color channels 灯 (i, j), G 灯 (i, j), B 灯(i, j), according to the definition of the HSV (hue (H), saturation (S), value (V)) color space, use formula (1) to calculate the saturation S of each pixel in the first underwater light array image 灯 (i, j):

[0076]

[0077] wherein, means taking the maximum value among the three values, means taking the minimum value among the three values.

[0078] Subsequently, calculate the average value s of the saturation of all pixels in the underwater light array image 灯 , and the calculation formula is:

[0079]

[0080] S2.4: Turn off the underwater light array and turn on the underwater wireless optical communication light source, and use the underwater color camera to capture the light-emitting image of the underwater wireless optical communication light source. The underwater wireless optical communication light source includes the emission light sources of the first underwater wireless optical communication transmitter and the second underwater wireless optical communication transmitter;

[0081] S2.5: Use the underwater image processing module to calculate the brightness R of the RGB three color channels of each pixel in the underwater wireless optical communication light source image 通 (i, j), G 通 (i, j), B 通 (i, j), where i is the number of the row pixels of the underwater color camera, and the value is an integer within [1, M], and j is the number of the column pixels of the underwater color camera, and the value is an integer within [1, N]. M and N are the total number of pixel rows and columns respectively. R 通 (i, j), G 通 (i, j), B 通 (i, j) is an integer within the value range of [0, 255];

[0082] S2.6: According to the brightness R of the RGB three color channels of each pixel 通 (i, j), G 通 (i, j), B 通 (i, j), according to the definition of the HSV color space, use formula (3) to calculate the saturation S of each pixel in the underwater wireless optical communication light source image 通 (i, j):

[0083]

[0084] wherein, means taking The maximum value among the three values indicates taking the minimum value among the three values.

[0085] Subsequently, obtain the average saturation value s of all pixels in the underwater wireless optical communication light source image 通 , and the calculation formula is:

[0086]

[0087] S2.7: Compare the average saturation value s of all pixels in the first underwater light array image 灯 with the average saturation value s of all pixels in the underwater wireless optical communication light source image 通 , calculate the identifier B of the decision basis, and store it in the underwater image processing module. The calculation formula is:

[0088]

[0089] S3: Turn on the underwater light array, the underwater color camera, the first underwater wireless optical communication terminal, and the second underwater wireless optical communication terminal, and use the underwater color camera to capture the pattern of the second underwater light array.

[0090] Specifically, turn on the first underwater wireless optical communication transmitter, the first underwater wireless optical communication receiver, the second underwater wireless optical communication transmitter, the second underwater wireless optical communication receiver, the underwater light array, and the underwater color camera, so that they are all in the working state, and use the underwater color camera to capture the pattern of the second underwater light array at this time.

[0091] In this embodiment, the LED lights in the selected underwater light array are different from the working wavelengths, spectral characteristics, and powers of the emitters and receivers in the underwater two-way wireless optical communication system, resulting in obvious differences in their saturations. The video images captured by the underwater color camera are mixed with underwater wireless optical communication light interference.

[0092] S4: Use the underwater image processing module to process the second underwater light array image and filter out the underwater wireless optical communication light interference in the second underwater light array image.

[0093] In this embodiment, step S4 specifically includes:

[0094] S4.1: The underwater image processing module acquires the second underwater light array image, and calculates the brightnesses R(i,j), G(i,j), and B(i,j) of each pixel in the RGB three color channels of the second underwater light array image, where i is the number of the row pixel of the underwater color camera, and the value range is an integer within [1, M], j is the number of the column pixel of the underwater color camera, and the value range is an integer within [1, N], M and N are the total number of pixel rows and columns respectively, and R(i,j), G(i,j), and B(i,j) are integers within the value range of [0, 255];

[0095] S4.2: According to the brightnesses R(i,j), G(i,j), and B(i,j) of each pixel in the RGB three color channels, and according to the definition of the HSV color space, use formula (6) to calculate the saturation S(i,j) of each pixel in the second underwater light array image:

[0096]

[0097] where, denotes taking the maximum value among the three values. denotes taking the minimum value among the three values.

[0098] Subsequently, according to the saturation S(i,j) of each pixel, use formula (7) to calculate the average saturation S avg of all pixels in the image:

[0099]

[0100] Furthermore, obtain the maximum saturation S max of all pixels.

[0101] S4.3: Use the average saturation S avg and the maximum saturation S max to calculate the threshold S th , and the calculation formula is:

[0102]

[0103] S4.4: Clear the pixels according to the identifier B of the judgment basis. If B = 0, then clear all pixels in the second underwater light array image where the saturation S(i,j)>S th ; if B = 1, then clear all pixels in the second underwater light array image where the saturation S(i,j)<S th , that is, filter out the underwater wireless optical communication light interference in the image to obtain the filtered image.

[0104] S5: Use the underwater image processing module to perform grayscale processing and Gaussian filtering on the filtered image obtained in S4 to obtain the filtered image.

[0105] In this embodiment, step S5 specifically includes:

[0106] S5.1: According to the brightness R'(i, j), G'(i, j), and B'(i, j) of each pixel in the RGB three color channels of the filtered image, use formula (9) to obtain the grayscale image g(i, j) of each pixel:

[0107] g(i, j) = 0.114 B'(i, j) + 0.587 G'(i, j) + 0.299 R'(i, j) (9)

[0108] S5.2: Let the Gaussian filter radius be n G , then the two-dimensional Gaussian kernel w G is a matrix with both length and width of 2 G + 1, and the element in the m-th row and n-th column can be expressed as:

[0109]

[0110] where m, n ∈ [1, 2n G + 1], and both m and n are integers. σ is the standard deviation of the Gaussian function. In applications, the most suitable σ value can be deduced through n G :

[0111] σ = 0.3 × [(n c - 1) × 0.5 - 1] + 0.8 (11)

[0112] S5.3: Normalize the two-dimensional Gaussian kernel w G to obtain W G :

[0113]

[0114] S5.4: Perform two-dimensional convolution on the grayscale image g(i, j) obtained in S61 and the normalized two-dimensional Gaussian kernel W G to obtain the grayscale image g1(i, j) after Gaussian filtering:

[0115]

[0116] where p and q are both integers and satisfy:

[0117]

[0118] S6: Obtain the coordinates corresponding to the center of each light spot in the filtered image.

[0119] This step is achieved through the following steps:

[0120] S6.1: Using formula (15), perform binarization on each pixel in the filtered image in S5 to obtain a binarized image g2(x, y):

[0121]

[0122] S6.2: Use the connectivity algorithm to find all the light spots in the binarized image, and mark the coordinates of all the pixels included in the k-th light spot with (x ki , y ki ), where x ki represents the abscissa of the i-th pixel in the k-th light spot, and y ki represents the ordinate of the i-th pixel in the k-th light spot. The total number of pixels in each light spot is n.

[0123] S6.3: Calculate the centroid coordinates of each light spot obtained in S6.2. The centroid (C kx , C ky ) of the k-th light spot is expressed as:

[0124]

[0125] S7: According to the coordinates of the center of each light spot obtained in S6, the pose of the underwater light array relative to the underwater color camera.

[0126] In this embodiment, step S7 specifically includes:

[0127] S7.1: Based on the infinitesimal plane pose estimation algorithm (IPPE pose solution algorithm), input the centroid coordinates of all the light spots obtained in S7 to obtain the rotation matrix R and the transformation vector t of the center of the underwater light array relative to the underwater color camera.

[0128] S7.2: Using the rotation matrix R and the transformation vector t obtained in S81, calculate the distance d, yaw angle θ Yaw , pitch angle θ Pitch and roll angle θ Roll of the center of the underwater light array relative to the underwater color camera using formula (17):

[0129]

[0130] Among them,

[0131] Among them, R mn represents the upper left m×n submatrix of E.

[0132] S8: Obtain the relative pose of the two underwater wireless optical communication terminals according to the pose of the center of the underwater light array.

[0133] Specifically, in the application, since the components on the underwater drone are fixed, the displacement vector t1 of the first underwater wireless optical communication terminal relative to the underwater color camera is known and fixed; since the components of the underwater cooperative target support platform are fixed, the displacement vector t2 of the second underwater wireless optical communication terminal relative to the center of the light array is known and fixed.

[0134] To calculate the relative pose of the two underwater wireless optical communication terminals, only the distance d needs to be corrected according to formula (18), while θ Yaw , θ Pitch , θ Roll remains unchanged. Therefore, the corrected distance d' of the underwater light array relative to the underwater color camera is:

[0135]

[0136] Embodiment 2

[0137] Based on Embodiment 1, in this embodiment, a simulation test system is used to simulate the underwater wireless optical communication cooperative target pose measurement system. Please refer to Figure 3 , Figure 3 which is a schematic structural diagram of an example provided by an embodiment of the present invention. The simulation test system mainly consists of two experimental brackets:

[0138] The first experimental bracket is used to simulate the first underwater wireless optical communication terminal, and includes a first underwater bracket, a first underwater wireless optical communication transmitter, a first underwater wireless optical communication receiver, an underwater color camera, and a computer. Among them, the first underwater bracket is used to simulate the underwater robot. There is a support platform at the lower end of the first underwater bracket that can rotate horizontally. The underwater color camera, the first underwater wireless optical communication transmitter, and the first underwater wireless optical communication receiver are all fixed on the bracket. The light-emitting surface or receiving surface of the three is in a plane and perpendicular to the rotation direction of the first underwater bracket. The computer is used to simulate the underwater image processing module. Among them, the power of the wireless optical communication light source of the first underwater wireless optical communication transmitter and the first underwater wireless optical communication receiver is about 3W when operating directly, the divergence angle is 120°, the central wavelength is 470nm, and the spectral width is 30nm.

[0139] The second experimental bracket is used to simulate the communication cooperative target, that is, the second underwater wireless optical communication terminal, and includes a second underwater bracket, a second underwater wireless optical communication transmitter, a second underwater wireless optical communication receiver, and an underwater light array composed of four LED lights. Among them, the underwater light array emits white light, and the output light power of each LED light is about 10W, and the divergence angle is 120°.

[0140] Conduct the experiment according to the following steps:

[0141] Step 1: Install the first underwater wireless optical communication transmitter, the first underwater wireless optical communication receiver, and the underwater color camera according to the orientation during the actual operation of the first underwater wireless optical communication terminal. Moreover, the light-emitting surface of the first underwater wireless optical communication transmitter, the receiving surface of the first underwater wireless optical communication receiver, and the receiving surface of the underwater color camera are located in the same plane;

[0142] Step 2: Install the second underwater wireless optical communication transmitter, the second underwater wireless optical communication receiver, and the underwater light array according to the orientation during the actual operation of the second underwater wireless optical communication terminal. Moreover, the light-emitting surface of the second underwater wireless optical communication transmitter, the receiving surface of the second underwater wireless optical communication receiver, and the light-emitting surface of the underwater light array are located in the same plane. The center of the light and the center of the underwater color camera are at the same height.

[0143] Step 3: Before using the wireless optical communication system and the optical communication cooperation target pose measurement system, keep the first underwater wireless optical communication terminal and the second underwater wireless optical communication terminal at a distance of about 2.5 meters, turn on the underwater light array and the underwater wireless optical communication light source respectively, and obtain the identifier of the decision basis for the underwater wireless optical communication light source image by using the underwater image processing module, and test to obtain s 灯 greater than s 通 , the identifier of the decision basis B = 1, and store it in the computer.

[0144] Step 4: Turn on the underwater light array, the underwater color camera, the emitter and receiver of the first underwater wireless optical communication terminal, and the emitter and receiver of the second underwater wireless optical communication terminal to make them all in the working state, and use the underwater color camera to capture the image of the second underwater light array;

[0145] Step 5: Use the underwater image processing module to process the image of the second underwater light array captured in Step 4, filter out the underwater wireless optical communication light interference in the image, and obtain the filtered image;

[0146] Step 6: Use the underwater image processing module to perform grayscale processing and Gaussian filtering on the filtered image obtained in Step 5 to obtain the Gaussian-filtered image;

[0147] Step 7: Calculate the coordinates corresponding to the center of each light spot in the Gaussian-filtered image obtained in Step 6;

[0148] Step 8: Calculate the pose of the center of the underwater light array according to the coordinates of the center of each light spot obtained in Step 7;

[0149] Step 9: Obtain the relative pose of the two underwater wireless optical communication terminals according to the pose of the center of the underwater lighting array obtained in Step 8.

[0150] During the experiment, the centers of the underwater color camera and the underwater lighting array are at the same height, and when the rotating bracket is at an angle of 0°, the center of the underwater lighting array is located on the optical axis of the underwater color camera. When the two communication terminals are at different distances, horizontally rotate the rotating platform in the first communication wireless optical communication terminal, and the test results are shown in Table 1. It can be seen that when testing between 2.10 m and 3.70 m and rotating within a range of 10°, the angular error is less than 1°, and the relative distance error is less than 1%. The feasibility of the method of this embodiment is verified.

[0151] Table 1. Test Results

[0152] Serial number Distance between two terminals Rotation angle Relative error of distance Absolute error of angle 1 2.10m 5° 0.18％ 0.55° 2 1.90m -5° 0.23％ 0.13° 3 3.20m 10° 0.26％ 0.12° 4 2.80m -10° 0.13％ 0.43° 5 3.70m 10° 0.19％ 0.68°

[0153] The method for measuring the pose of a cooperative target for underwater wireless optical communication of the present invention solves the problem of measuring the pose of a cooperative target for underwater wireless optical communication by integrating visual guidance measurement technology and an underwater wireless optical communication system. It has a simple structure, low complexity, is easy to combine with an underwater platform, and is convenient for popularization and application. The method for measuring the pose of a cooperative target for underwater wireless optical communication of the present invention suppresses the influence of communication lights on visual measurement through the saturation (S) channel in the HSV color space, enabling the underwater wireless optical communication system and the pose measurement system to work simultaneously, and greatly improving the compatibility of the communication link establishment process and the two-way wireless optical communication process.

[0154] In several embodiments provided by the present invention, it should be understood that the devices and methods disclosed by the present invention can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the modules is only a logical function division. In actual implementation, there may be other division methods. For example, multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed.

[0155] In addition, each functional module in each embodiment of the present invention can be integrated in a processing module, or each module can exist physically alone, or two or more modules can be integrated in one module. The above integrated modules can be implemented in the form of hardware, or in the form of a combination of hardware and software functional modules.

[0156] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. An underwater wireless optical communication cooperative target pose measurement method, characterized in that, Including: S1: Construct an underwater wireless optical communication cooperative target pose measurement system. The system includes an underwater robot and an underwater cooperative target support platform. Among them, the underwater robot is used to carry a first underwater wireless optical communication terminal, an underwater color camera, and an underwater image processing module, and the underwater cooperative target support platform is used to carry a second underwater wireless optical communication terminal and an underwater light array; S2: Keep the first underwater wireless optical communication terminal and the second underwater wireless optical communication terminal at a predetermined distance, turn on the underwater light array and the underwater wireless optical communication light source respectively, and obtain an identifier for judging the underwater wireless optical communication light source image; S3: Turn on the underwater light array, the underwater color camera, the first underwater wireless optical communication terminal and the second underwater wireless optical communication terminal, and use the underwater color camera to capture an image of the second underwater light array; S4: Process the image of the second underwater light array, filter out the underwater wireless optical communication light interference in the image of the second underwater light array, and obtain a filtered image; S5: Perform gray processing and Gaussian filtering on the filtered image to obtain a filtered image; S6: Obtain the centroid coordinates of each light spot in the filtered image; S7: Obtain the pose of the underwater light array relative to the underwater color camera according to the centroid coordinates of each light spot; S8: Obtain the relative pose of the two underwater wireless optical communication terminals according to the pose of the center of the underwater light array.

2. The underwater wireless optical communication cooperative target pose measurement method according to claim 1, characterized in that The first underwater wireless optical communication terminal includes a first underwater wireless optical communication transmitter and a first underwater wireless optical communication receiver, and the light emitting surface of the first underwater wireless optical communication transmitter, the receiving surface of the first underwater wireless optical communication receiver, and the receiving surface of the underwater color camera are located in the same plane; The second underwater wireless optical communication terminal includes a second underwater wireless optical communication transmitter and a second underwater wireless optical communication receiver, and the light emitting surface of the second underwater wireless optical communication transmitter, the receiving surface of the second underwater wireless optical communication receiver, and the light emitting surface of the underwater light array are located in the same plane; The first underwater wireless optical communication transmitter is used to send a wireless optical communication signal into the water, the first underwater wireless optical communication receiver is used to receive the underwater wireless optical communication signal, the second underwater wireless optical communication transmitter is used to send a communication optical signal to the first underwater wireless optical communication receiver, and the second underwater wireless optical communication receiver is used to receive the communication optical signal from the first underwater wireless optical communication transmitter.

3. The underwater wireless optical communication cooperative target pose measurement method according to claim 2, characterized in that The first underwater wireless optical communication transmitter, the first underwater wireless optical communication receiver, the second underwater wireless optical communication transmitter and the second underwater wireless optical communication receiver together constitute an underwater two-way wireless optical communication system, and the working wavelength, spectral characteristics, and power of the underwater light array and the underwater two-way wireless optical communication system are different.

4. The underwater wireless optical communication cooperative target pose measurement method according to claim 2, wherein The S2 includes: S2.1: Only turn on the underwater light array, and use the underwater color camera to capture an image of the first underwater light array; S2.2: Calculate the brightness R 灯 (i, j), G 灯 (i, j), B 灯 (i, j) of each pixel in the RGB three color channels of the first underwater light array image, where i is the number of row pixels of the underwater color camera, and j is the number of column pixels of the underwater color camera; S2.3: Obtain the saturation S 灯 (i, j), G 灯 (i, j), B 灯 (i, j) of each pixel in the first underwater light array image, and obtain the average saturation s of all pixels 灯 (i, j); 灯 ; S2.4: Turn off the underwater light array and turn on the underwater wireless optical communication light source. Use the underwater color camera to capture an image of the underwater wireless optical communication light source, where the underwater wireless optical communication light source includes the emission light sources of the first underwater wireless optical communication transmitter and the second underwater wireless optical communication transmitter; S2.5: Calculate the brightness values R 通 (i,j), G 通 (i,j), B 通 (i,j) of each pixel in the RGB three color channels of the underwater wireless optical communication light source image by using the underwater image processing module; S2.6: Obtain the saturation S 通 (i,j) and the saturation average value s of all pixels of the underwater wireless optical communication light source image according to the luminance R 通 (i,j), G 通 (i,j), B 通 (i,j) of each pixel in the underwater wireless optical communication light source image 通 ; S2.7: Compare the average saturation value s of all pixels in the first underwater light array image 灯 with the average saturation value s of all pixels in the underwater wireless optical communication light source image 通 , and obtain the identifier B for the judgment basis:

5. The underwater wireless optical communication cooperative target pose measurement method according to claim 2, characterized in that S4 includes: S4.1: The underwater image processing module acquires the second underwater light array image and calculates the brightness R(i,j), G(i,j), B(i,j) of each pixel in the RGB three color channels of the second underwater light array image, where i is the number of the row pixels of the underwater color camera and j is the number of the column pixels of the underwater color camera; S4.2: According to the brightness values R(i,j), G(i,j), and B(i,j) of the RGB three color channels of each pixel, calculate the saturation S(i,j) of each pixel in the second underwater light array image, the average saturation value S of all pixels avg and the maximum saturation value S of all pixels max ; S4.3: Calculate the threshold S using the average saturation value S avg and the maximum saturation value S max th :​ S4.4: Clear the pixels according to the identifier B. If B = 0, clear all pixels in the second underwater light array image where the saturation S(i,j) > S th ; if B = 1, clear all pixels in the second underwater light array image where the saturation S(i,j) < S th to obtain a filtered image.

6. The underwater wireless optical communication cooperative target pose measurement method according to claim 2, wherein S5 includes: S5.1: According to the brightness R'(i,j), G'(i,j), B'(i,j) of the RGB three color channels of each pixel of the filtered image, obtain the grayscale image g(i,j) of each pixel; S5.2: Set the Gaussian filter radius to n G , then the two-dimensional Gaussian kernel w G is a matrix with both length and width of 2 G +1, and the element in the m-th row and n-th column is expressed as where \(m,n\in[1,2n G + 1]\), and both \(m\) and \(n\) are integers, and \(\sigma\) is the standard deviation of the Gaussian function. S5.3: Normalize the two-dimensional Gaussian kernel w G to obtain the normalized two-dimensional Gaussian kernel W G : S5.4: Convolve the grayscale image g(i, j) obtained in S5.1 with the normalized two-dimensional Gaussian kernel W G to obtain the grayscale image g1(i, j) after Gaussian filtering: where both p and q are integers and satisfy 7. The underwater wireless optical communication cooperative target pose measurement method according to claim 2, characterized in that, S6 includes: S6.1: Perform binarization processing on each pixel in the filtered image to obtain a binarized image; S6.2: Use the connectivity algorithm to find all the light spots in the binary image, and mark the coordinates of all the pixels included in the k-th light spot with (x ki , y ki ), where x ki represents the abscissa of the i-th pixel in the k-th light spot, and y ki represents the ordinate of the i-th pixel in the k-th light spot; S6.3: Calculate the centroid coordinates of each light spot.

8. The underwater wireless optical communication cooperative target pose measurement method according to any one of claims 2 to 7, characterized in that, S7 includes: S7.1: Based on the attitude estimation algorithm of an infinitesimal plane, use the centroid coordinates of all light spots to obtain the rotation matrix R and the transformation vector t of the center of the underwater light array relative to the underwater color camera; S7.2: Obtain the distance d, yaw angle θ Yaw , pitch angle θ Pitch and roll angle θ Roll of the center of the underwater light array relative to the underwater color camera by using the rotation matrix R and the transformation vector t.

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