A three-dimensional coordinate measurement method for conformal underwater acoustic equipment

Abstract

The present application relates to the field of ship technology, and more specifically, to a method for measuring the three-dimensional coordinates of a conformal hydroacoustic device. The present application provides a method for measuring the three-dimensional coordinates of a conformal hydroacoustic device. A photographing device is used to photograph the conformal hydroacoustic device to obtain an image of the conformal hydroacoustic device, and a measuring instrument at a reference point is used to obtain the three-dimensional coordinates of the photographing device. The three-dimensional coordinates of the marked target and the characteristic points used for calculation on the hydroacoustic device are calculated using photogrammetry technology, and an observation device is used to measure the actual three-dimensional coordinates of the marked target to verify whether the three-dimensional coordinates of the marked target calculated by the photogrammetry technology meet the requirements, thereby ensuring the measurement accuracy. By using photographing equipment and photogrammetry technology, the number of hydroacoustic devices that need to be observed by measuring instruments is reduced, thereby greatly improving the measurement speed of the three-dimensional coordinates of the hydroacoustic device, and solving the technical problem of low efficiency in measuring the three-dimensional coordinates of the center of the hydroacoustic device in the current conformal hydroacoustic device.

Description

Technical Field

[0001] The present application relates to the field of ship technology, and in particular to a three-dimensional coordinate measurement method for a conformal hydroacoustic device. Background Art

[0002] Conformal hydroacoustic equipment is an important component of ships, which can detect, classify, locate and track targets. Conformal hydroacoustic equipment includes hydrophones and arrays. The hydrophones are arranged in a certain geometric pattern on the array, and the installation accuracy is at the millimeter level. In order to give full play to the detection capability of conformal hydroacoustic equipment and improve the recognition accuracy, after all hydrophones are installed, it is necessary to measure the three-dimensional coordinates of the center of each hydrophone, that is, to measure the center position of each hydrophone and the normal vector of each hydrophone surface, as the initial parameters for the sonar system to solve. The commonly used three-dimensional coordinate measurement method is to place a total station in front of the conformal hydroacoustic equipment, and use the total station to measure the position of each hydrophone to obtain the three-dimensional coordinates of the center of each hydrophone.

[0003] For large conformal hydroacoustic equipment, the base array weighs more than 20 tons. The array frame is usually made up of three sections. The front end of the array frame is 5 meters long, the widest part is 7 meters, and the height is 3 meters. The entire shape is arc-shaped. More than 2,000 hydrophones need to be arranged on the arc surface of the entire array frame. The number of hydrophones is large, and the traditional measurement method takes a long time and has low measurement efficiency. Summary of the invention

[0004] The purpose of the embodiments of the present application is to provide a method for measuring the three-dimensional coordinates of a conformal hydroacoustic device, so as to improve the measurement efficiency of the three-dimensional coordinates of the center of a hydrophone of the conformal hydroacoustic device.

[0005] In a first aspect, a method for measuring three-dimensional coordinates of a conformal hydroacoustic device is provided, comprising the following steps:

[0006] 1) Setting marking targets on multiple hydroacoustic devices of the conformal hydroacoustic device and arranging multiple reference points on the front side of the conformal hydroacoustic device;

[0007] 2) Establish a three-dimensional coordinate system, determine the relative position of each reference point through a measuring instrument, and then determine the three-dimensional coordinates of each reference point;

[0008] 3) measuring the three-dimensional coordinates of the marked target point by a measuring instrument at the reference point; using a shooting device to obtain an image of the conformal hydroacoustic device, and measuring the shooting device by a measuring instrument at the reference point to obtain the three-dimensional coordinates of the shooting device at the shooting position; using photogrammetry technology to calculate the three-dimensional coordinates of the feature points used for coordinate calculation on each hydroacoustic device in the conformal hydroacoustic device and the marked target point according to the three-dimensional coordinate position of the shooting device, the posture parameters of the shooting device when taking pictures, and the conformal hydroacoustic device image taken by the shooting device;

[0009] 4) Use a measuring instrument to measure the three-dimensional coordinates of the marked target point, and verify the three-dimensional coordinates of the marked target point calculated by photogrammetry. If the accuracy of the three-dimensional coordinates of the marked target point meets the requirements, the accuracy of the three-dimensional coordinates of the feature points used for coordinate calculation of each hydrophone calculated by photogrammetry meets the requirements;

[0010] 5) According to the positional relationship between the characteristic points used for coordinate calculation on the hydrophone and the center point of the hydrophone, the three-dimensional coordinates of the center point of the hydrophone are calculated.

[0011] In a possible implementation, a total station is used as a measuring instrument, and in step 1), each reference point is arranged in an arc shape at intervals on the front side of the conformal hydroacoustic device;

[0012] The reference points are a1, a2, ... a from left to right in the horizontal direction perpendicular to the centerline of the ship. n ;

[0013] Divide the hydroacoustic devices on the conformal hydroacoustic device into n groups according to the positions of the reference points, with each group arranged left and right and at least one hydroacoustic device in each group having a marked target point;

[0014] The measuring instruments at each reference point are used to observe the groups of hydrophones on the conformal hydroacoustic device, and the measuring instruments at two adjacent reference points observe the intersection angles of the marked targets on the same group of hydrophones.

[0015] In a possible implementation scheme, a total station is used as a measuring instrument, and the relative position of each reference point is determined by:

[0016] Measuring instruments are set at each reference point at the same time, and the mutual angles and distances between the reference points are determined by the measuring instruments, thereby determining the three-dimensional coordinates of each reference point.

[0017] In a possible implementation, when determining the relative positions of the reference points, the method for determining the distance l0 between two reference points is:

[0018] Assume that the two reference points of the distance to be measured are reference point A and reference point B, set up measuring instruments at reference point A and reference point B, the on-site measurement distance between AB is l, set up a standard ruler on the horizontal side of reference point A and reference point B, the line connecting reference point A and reference point B is parallel to the standard ruler, select the left point on the standard ruler as L, the right point as R, and the distance LR is known as S;

[0019] The included angle ∠LAB=L is measured and calculated at the reference point A and the reference point B respectively. A ∠RAB=R A , ∠LBA=L B ∠RBA=R B, based on the similarity relationship and the intersection formula, we can get the following relationship:

[0020]

[0021]

[0022] LR's distance calculation value S':

[0023]

[0024] according to:

[0025]

[0026] The AB distance is calculated to be l0.

[0027] In a possible implementation, in step 3), the center of the screw on the hydrophone is selected as a feature point for coordinate calculation, and then the coordinates of the center of the hydrophone are calculated based on the coordinates of the center of the screw. The position of the screw on the hydrophone is relatively obvious and easy to identify.

[0028] In a possible implementation, in step 1), a color mark is applied to the center of the screw for identification of feature points for coordinate calculation. The color mark further facilitates subsequent feature point extraction.

[0029] In a possible implementation, the centers of multiple screws on the hydrophone are used as feature points for coordinate calculation. According to the coordinates of the centers of multiple screws on the hydrophone, the normal vector (a, b, c) of the hydrophone is calculated by the least square method and normalized:

[0030]

[0031]

[0032] In a possible implementation, the coordinate conversion formula between the center of the screw and the center of the hydroacoustic device is:

[0033]

[0034] Where x and y are the coordinates of the image after centering required for calculation; I and J are the coordinates measured directly on the image; W and H are the image width and height; pixel is the size of a single pixel, x0 and y0 are the principal point coordinates of the camera; Δx and Δy are constants obtained by camera calibration.

[0035] In a possible implementation, when taking images by a shooting device in step 3), multiple images are overlapped in the left-right direction at a ratio of a% and in the up-down direction at a ratio of b% to obtain an overall image of the conformal hydroacoustic device, where a is greater than b.

[0036] In a possible implementation, the hydrophones are numbered before setting the marked targets in step 1).

[0037] The three-dimensional coordinate measurement method of a conformal hydroacoustic device in the present application has the beneficial effect that the three-dimensional coordinate measurement method of a conformal hydroacoustic device in the present application uses a shooting device to take a photo of the conformal hydroacoustic device to obtain an image of the conformal hydroacoustic device, and uses a measuring instrument at a reference point to obtain the three-dimensional coordinates of the shooting device, uses photogrammetry technology to calculate the three-dimensional coordinates of the marked target and the characteristic points used for calculation on the hydroacoustic device, and uses an observation device to measure the actual three-dimensional coordinates of the marked target, verifies whether the three-dimensional coordinates of the marked target calculated by the photogrammetry technology meet the requirements, and ensures the measurement accuracy. By using the shooting device and photogrammetry technology, the number of hydroacoustic devices that need to be observed by measuring instruments is reduced, thereby greatly improving the measurement speed of the three-dimensional coordinates of the hydroacoustic device, and solves the technical problem of low efficiency in measuring the three-dimensional coordinates of the center of the hydroacoustic device in the current conformal hydroacoustic device. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0039] Figure 1 A layout diagram of a hydroacoustic device showing a method for measuring three-dimensional coordinates of a conformal hydroacoustic device according to an embodiment of the present application;

[0040] Figure 2 A diagram showing a layout of reference points in a three-dimensional coordinate measurement method for a conformal hydroacoustic device according to an embodiment of the present application;

[0041] Figure 3 A schematic diagram of calculating the distance between a reference point A and a reference point B in a three-dimensional coordinate measurement method of a conformal hydroacoustic device according to an embodiment of the present application;

[0042] Figure 4 A schematic diagram of measuring a marked target point in a three-dimensional coordinate measurement method of a conformal hydroacoustic device according to an embodiment of the present application;

[0043] Figure 5 A schematic diagram of the principle of directional observation in a three-dimensional coordinate measurement method of a conformal hydroacoustic device according to an embodiment of the present application;

[0044] Figure 6A schematic diagram of marking a target point in a three-dimensional coordinate measurement method of a conformal hydroacoustic device according to an embodiment of the present application;

[0045] Figure 7 A schematic diagram of a single hydroacoustic device in a three-dimensional coordinate measurement method of a conformal hydroacoustic device according to an embodiment of the present application;

[0046] Figure 8 A three-dimensional schematic diagram of the center of each hydroacoustic device obtained by simulating the measured data using computer software in a three-dimensional coordinate measurement method of a conformal hydroacoustic device according to an embodiment of the present application;

[0047] Fig. 9 A three-dimensional schematic diagram of obtaining the center normal vector of each hydroacoustic device by simulating the measured data using computer software in a three-dimensional coordinate measurement method of a conformal hydroacoustic device according to an embodiment of the present application;

[0048] In the figure: 1. Hydroacoustic device; 2. Target mark; 3. Screw. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0050] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0051] According to one aspect of the present application, a method for measuring the three-dimensional coordinates of a conformal hydroacoustic device is provided. Figures 1 to 4 , Figure 6 , including the following steps:

[0052] 1) Setting marking targets 2 on a plurality of hydroacoustic devices 1 of a conformal hydroacoustic device, and arranging a plurality of reference points on the front side of the conformal hydroacoustic device;

[0053] 2) Establish a three-dimensional coordinate system, determine the relative position of each reference point through a measuring instrument, and then determine the three-dimensional coordinates of each reference point;

[0054] 3) Measure the three-dimensional coordinates of the marked target point 2 by using a measuring instrument at the reference point; Use a shooting device to obtain an image of the conformal hydroacoustic device, and measure the shooting device by using a measuring instrument at the reference point to obtain the three-dimensional coordinates of the shooting device at the shooting position; According to the three-dimensional coordinate position of the shooting device, the posture parameters of the shooting device when taking pictures, and the conformal hydroacoustic device image taken by the shooting device, use photogrammetry technology to calculate the feature points for coordinate calculation on each hydroacoustic device 1 in the conformal hydroacoustic device and the three-dimensional coordinates of the marked target point 2;

[0055] 4) Using a measuring instrument to measure the three-dimensional coordinates of the marked target point 2, and verifying the three-dimensional coordinates of the marked target point 2 calculated by the photogrammetry technique. If the accuracy of the three-dimensional coordinates of the marked target point meets the requirements, the accuracy of the three-dimensional coordinates of the feature points used for coordinate calculation of each hydrophone calculated by the photogrammetry technique meets the requirements;

[0056] 5) According to the positional relationship between the characteristic points used for coordinate calculation on the hydrophone and the center point of the hydrophone, the three-dimensional coordinates of the center point of the hydrophone are calculated.

[0057] The three-dimensional coordinate measurement method of the conformal hydroacoustic device of the present application adopts a photographing device to take a photo of the conformal hydroacoustic device to obtain the conformal hydroacoustic device image, and uses a measuring instrument at a reference point to obtain the three-dimensional coordinates of the photographing device, and uses a photogrammetry technique to calculate the three-dimensional coordinates of the marking target 2 and the characteristic points used for calculation on the hydroacoustic device 1, and uses an observation device to measure the actual three-dimensional coordinates of the marking target 2, and verifies whether the three-dimensional coordinates of the marking target 2 calculated by the photogrammetry technique meet the requirements, thereby ensuring the measurement accuracy. By adopting the photographing device and the photogrammetry technique, the number of hydroacoustic devices 1 that need to be observed by the measuring instrument is reduced, thereby greatly improving the measurement speed of the three-dimensional coordinates of the hydroacoustic device 1, and solving the technical problem of low efficiency in measuring the three-dimensional coordinates of the hydroacoustic device 1 in the current conformal hydroacoustic device.

[0058] In one embodiment, the photographing device includes a camera, and the camera is used to take a picture of the conformal hydroacoustic device.

[0059] In one embodiment, in step 1), the reference points are arranged in an arc shape at intervals on the front side of the conformal hydroacoustic device; the reference points are respectively a1, a2, ..., a from left to right in the horizontal direction perpendicular to the centerline of the ship. n ;

[0060] The hydroacoustic devices 1 on the conformal hydroacoustic device are divided into n groups according to the positions of the reference points, and the groups are arranged left and right, and at least one of the hydroacoustic devices 1 in each group has a marked target point 2;

[0061] The measuring instruments at each reference point are used to observe the hydroacoustic devices 1 on the conformal hydroacoustic device in groups, and the measuring instruments at two adjacent reference points observe the intersection angles of the marker targets in the same group.

[0062] In one embodiment, the relative position of each reference point is determined by setting a measuring instrument at each reference point, using the measuring instrument to determine the mutual angle and distance between each reference point, and then determining the three-dimensional coordinates of each reference point. In one embodiment, the distance between the reference points can also be measured by a length measuring instrument.

[0063] In one embodiment, the entire reference point uses the extension direction of the bow and stern line as the extension direction of the X coordinate axis, the horizontal direction perpendicular to the bow and stern line is the extension direction of the Y coordinate axis, and the elevation is based on the horizontal plane. In one embodiment, the establishment of the coordinate system is set as needed, and the extension direction of the X coordinate axis can be any direction.

[0064] In one embodiment, five measurement forced centering frames are fixed in front of the conformal hydroacoustic device. The five forced centering frames serve as five reference points for the entire measurement operation. During installation, the five reference points are ensured to be able to see each other. The hydroacoustic device 1 on the conformal hydroacoustic device is divided into five groups according to the positions of the reference points for observation, and observation is performed by two adjacent reference points respectively to avoid the situation where the target cannot be observed. In one embodiment, three reference points are set. Of course, according to actual needs, any number of reference points more than three can be set.

[0065] In one embodiment, the reference point is the reference for the entire measurement work. The coordinates of all targets are calculated based on the reference point. The error in the reference point has a great impact on the entire measurement work. In this embodiment, the measuring instrument is a total station. Figure 2 As shown, they are A, B, C, D, and E. Use the total station to observe the five benchmarks set up earlier and determine the angles between the five benchmarks. At any benchmark point, the remaining four benchmarks can be observed.

[0066] When observing, observe two rounds for each angle. For example, take the observation of ∠BAE at reference point A as an example. First, place the total station at the left position of the disk, aim at the fixed mark pasted near B, and record the current reading B. 左 , aim at target E clockwise and record the reading E 左 , complete the first half of the survey, then rotate the total station 180°, place the total station at the right position, observe target E, and record the reading E 右 , rotate counterclockwise to the fixed mark near B, and record the reading B 右 , that is, one round of observation is completed. The final observation angle is calculated as:

[0067]

[0068] Repeat the above process to complete the second round of measurement and take the average of the angles calculated from the two rounds of measurement.

[0069] When measuring the coordinates of the marked target point by the total station, in the forward intersection observation calculation formula, the distance between the reference points, i.e. the baseline length, directly affects the calculation accuracy of the coordinates. Therefore, the measurement accuracy of the baseline length has a direct impact on the overall accuracy. The baseline length can be obtained by measuring the station with a steel ruler, but since the center position of the total station cannot be known, even if the center position of the total station is known, the measurement with a steel ruler is only an approximate value, and the measurement accuracy is low, which cannot meet the accuracy requirements of the control field.

[0070] In one embodiment, when determining the relative positions of the reference points, the method for determining the distance l0 between two reference points is:

[0071] Assume that the two reference points of the distance to be measured are reference point A and reference point B, set up measuring instruments at reference point A and reference point B, the on-site measurement distance between AB is l, set up a standard ruler on the horizontal side of reference point A and reference point B, the line connecting reference point A and reference point B is parallel to the standard ruler, select the left point on the standard ruler as L, the right point as R, and the distance LR is known as S;

[0072] The included angle ∠LAB=L is measured and calculated at the reference point A and the reference point B respectively. A ∠RAB=R A , ∠LBA=L B ∠RBA=R B , based on the similarity relationship and the intersection formula, we can get the following relationship:

[0073]

[0074]

[0075] LR's distance calculation value S':

[0076]

[0077] according to:

[0078]

[0079] The AB distance is calculated to be l0.

[0080] In one embodiment, the distance between AB is l without on-site measurement, and a measuring instrument is set up at the reference point A and the reference point B, and a standard ruler is set up on the horizontal side of the reference point A and the reference point B, and the line connecting the reference point A and the reference point B is parallel to the standard ruler. Two points are selected on the standard ruler, the left point is L, and the right point is R, and the distance LR is known to be S; the baseline length AB is preset between AB as l0;

[0081] The included angle ∠LAB=L is measured and calculated at the reference point A and the reference point B respectively. A ∠RAB=R A , ∠LBA=L B ∠RBA=R B , based on the similarity relationship and the intersection formula, we can get the following relationship:

[0082]

[0083]

[0084] Calculate S:

[0085]

[0086] Then l0 can be calculated.

[0087] In one embodiment, if Figure 7 As shown, in step 3), the center of the screw 3 on the hydrophone 1 is selected as a feature point for coordinate calculation, and then the coordinates of the center of the hydrophone 1 are calculated based on the coordinates of the center of the screw 3.

[0088] In one embodiment, if Figure 7 As shown, in step 1), a red mark is applied to the center of the screw 3 for identification of feature points for coordinate calculation. The red mark facilitates feature extraction on subsequent images.

[0089] In one embodiment, the centers of the plurality of screws 3 on the hydrophone 1 are used as feature points for coordinate calculation. According to the coordinates of the centers of the plurality of screws 3 on the hydrophone 1, according to the least square method, according to the equation ax+by+cz=-1,

[0090] Calculate the normal vector (a, b, c) of hydrophone 1 and normalize it:

[0091]

[0092]

[0093] In one embodiment, when the image is captured by the shooting device in step 3), the multiple images are overlapped in the left-right direction at a ratio of a% and in the up-down direction at a ratio of b% to obtain an overall image of the conformal hydroacoustic device, where a is greater than b. In one embodiment, the image is acquired at an overlap of 80% in the left-right direction and at an overlap of 60% in the up-down direction.

[0094] In one embodiment, the hydrophone 1 is numbered before setting the marking target 2 in step 1) to facilitate the determination of the position of the hydrophone 1 and the installation of the marking target 2. Specifically, the row and column numbers are pasted on the hydrophone 1. Since there are many measurement targets, in order to quickly identify the targets, a number is printed every 5 columns and 5 rows, and the printed labels are pasted on the corresponding positions. In one embodiment, the row and column numbers are directly written on the hydrophone 1.

[0095] In one embodiment, the marking target point 2 is a cross target point pasted on the hydrophone 1. In order to control the absolute position of the hydrophone 1 and ensure that the measurement results can be in the same coordinates, the cross target point is pasted on part of the hydrophone 1 as a control point, and the control point is set according to 5 rows × 10 columns. The cross target point is used as a control point to ensure the accuracy of the final measurement structure.

[0096] In one embodiment, the measuring instrument is a total station, and the intersection angle of the marking target point 2 is observed in the following manner:

[0097] After establishing the reference point, measure the three-dimensional coordinates of the pasted marker target 2 by the intersection angle, such as Figure 4 As shown, due to the large arc of the observed target, it is observed in five sections, with the AB reference point intersecting the right target, the BC reference point intersecting the lower right target, the CD reference point intersecting the lower left target, and the DE reference point intersecting the left target.

[0098] When observing the angle of the marked target 2, it is necessary to observe the horizontal angle and the vertical angle respectively. In order to eliminate various errors of the instrument, the angle observation is carried out on both the left and right sides of the disk. The left disk is also called the positive mirror, which means that when the observer faces the eyepiece of the telescope, the vertical disk is on the left side of the telescope; the right disk is also called the inverted mirror, which means that when the observer faces the eyepiece of the telescope, the vertical disk is on the right side of the telescope.

[0099] There are two commonly used horizontal angle observation methods: the backsight method and the direction observation method. The backsight method is only applicable to the observation of a single angle formed by two directions. When a station needs to observe more than two directions, the direction observation method should be used to observe the horizontal direction value. For the entire observation target, since there are many points to be observed, the direction observation method is used for observation, and the zero direction is returned every 5-10 targets.

[0100] like Figure 5 As shown in the figure, the station is set up at O, and the observation targets are in the four directions of T0, T1, T2, and T3. The observation sequence of the directional method is:

[0101] 1) Set up the total station at point O of the measuring station. The base needs to be strictly leveled to observe the horizontal angles between T0, T1, T2, and T3 in each direction.

[0102] 2) Observation on the left side of the disk: Align the zeroing mark, set the instrument to zero, first observe the selected starting direction T0, then observe the directions T1, T2, and T3 in a clockwise direction, and finally return to the starting direction. This is called the first half of the measurement. The starting direction is observed twice in one measurement, and its purpose is to check whether the horizontal disk changes during the measurement process. If there is no significant change, take the average of the two measured values ​​as the zero direction value of the first half of the measurement;

[0103] 3) Face 2 observation: Set the total station to face 2, aim at T0 first, then aim at T3, T2, T1 counterclockwise, and finally return to T0. The calculated face 2 zero direction value is the same as face 1.

[0104] In one embodiment, the elevation angle of the marked target 2 is observed as follows:

[0105] The calculation of the elevation of the marked target 2 is based on the plane coordinate calculation and the trigonometric elevation method. To this end, it is only necessary to observe the angle between the line connecting the reference point to the marked target 2 and the horizontal direction through the total station. The observation of the elevation angle this time adopts the back-measurement method. First, use the telescope cross wire to record the reading M at the left position of the disk, then rotate the telescope 180°, and use the telescope cross wire to record the reading N at the right position of the disk. The difference between the two readings is averaged as the final observation result. The calculation formula for the elevation angle α is:

[0106] α 左 =90-M

[0107] α 右 =N-270

[0108] The mean is:

[0109]

[0110] In one embodiment, the method of acquiring an image through a shooting device is as follows:

[0111] Acquire multiple images with a certain degree of overlap, and acquire images with an overlap of 80% in the left-right direction and 60% in the up-down direction. Considering that the conformal hydroacoustic equipment has an arc, including a certain curvature from left to right and from top to bottom, select 3 different heights to photograph the target, and each height has an overlap of 60% from left to right. Because it is directly in front of the target, the shooting distance is limited. In order to ensure the overlap, the target can only be photographed from different directions. At the beginning of shooting, according to the lighting conditions on site, set the camera aperture f=10, the exposure time to 2 seconds, the ISO value to 100, and no flash. A total of 3 groups of images were taken, and 40 images were selected for the observation of the target point through screening. For example, Figure 6 shown.

[0112] In one embodiment, accurately measuring the target point on the image is the key to calculating the three-dimensional coordinates, which is called feature point extraction in image processing. For multiple images, the feature points are matched to automatically establish the correspondence between the images of the same spatial point in different images. The corresponding points of the same spatial point in different images are called image points of the same name. In the absence of any markings, the feature points cannot be distinguished, and matching technology is required to establish points of the same name. Image feature matching is the basis for solving the initial value of the three-dimensional coordinates of the measured point, establishing the correspondence between the three-dimensional space points and the two-dimensional space points in the adjustment optimization model, and ensuring the robust operation of the bundle adjustment.

[0113] In this embodiment, feature extraction is mainly to obtain the edge or center point of the component, and then obtain the coordinates of the corner point of the component. Since the edge of the component is an arc, it is impossible to show a clear edge on the image. Therefore, four screws are used to observe and fix the component. The top surface of the screw is a regular circle, and the center of the circle has been marked with red paint. When measuring, just take the red mark as the center of the circle as the target to be observed. In this embodiment, the center point of the screw and the marked target point are both feature extraction points, and the center point of the screw is the feature point for coordinate calculation. The marked target point is a verification feature point used to verify the accuracy of photogrammetry.

[0114] In one embodiment, the three-dimensional coordinates of the center of the hydrophone and the normal vector are calculated as follows:

[0115] 1) Image coordinate centering

[0116] The coordinates obtained directly on the image are row and column coordinates with the upper left corner of the image as the origin. In photogrammetry, the coordinates are converted using the following formula:

[0117]

[0118] Among them, x, y are the image coordinates after centering required for calculation; I, J are the coordinates measured directly on the image; W, H are the image width and height; pixel is the size of a single pixel, x0, y0 are the principal point coordinates of the camera; Δx, Δy are the distortion of the camera, and the corresponding parameters are obtained by camera calibration.

[0119]

[0120] k1, k2——radial distortion parameters;

[0121] p1, p2——tangential distortion parameters;

[0122] r is the distance from a point on the image to the principal point.

[0123] 2) Image coordinate adjustment calculation

[0124] Photogrammetry is a mature existing technology and is only briefly introduced in this application. According to the basic principle of photogrammetry, to measure the three-dimensional coordinates of the center of the hydrophone 1 from the image, the absolute position and posture of the center of each image must be known first. In photogrammetry, it is called the exterior orientation element of the photo, including the three-dimensional position (X S , Y S , Z S ) and three postures Assume that the coordinates of any target point in the object space are (X, Y, Z), and the coordinates of the image point M1 on a certain photo after imaging are (x, y). If the principal distance of the camera is f, and the position of the principal point O1 at the center of the photo is (x0, y0), then the auxiliary coordinates of the principal point in the center of the photo during measurement are (x, y, -f), and the image space auxiliary coordinates (X A , Y A , Z A ) satisfies the relationship:

[0125]

[0126] The attitude angle The rotation torque is expressed as:

[0127]

[0128] According to the collinear equation, the photographic center (X S , Y S , Z S ), any point M(X, Y, Z) on the object, and the corresponding point M1(X A , Y A , Z A ) should be on a straight line and should satisfy the relationship:

[0129]

[0130] Then the corresponding actual object point M (X, Y, Z) satisfies the relationship:

[0131]

[0132] Considering the principal point O1 at the center of the photo, the absolute coordinates of the actual object point M (X, Y, Z) can be expressed as:

[0133]

[0134] By linearizing the above equation and using a bundle adjustment method, the exterior orientation elements of each image and the precise coordinates of the center of the hydrophone 1 can be obtained. This is the most rigorous solution method in photogrammetry technology.

[0135] After processing the original observation data obtained on site, the final result is the coordinates of the center of each conformal array element and its corresponding normal vector. The calculated coordinates and normal vectors are plotted in AutoCAD, and the top view is as follows: Figure 8 As shown, it is also displayed in three-dimensional form. The three-dimensional display after drawing the normal vector is as follows Fig. 9 shown.

[0136] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A three-dimensional coordinate measurement method for a conformal hydroacoustic device, characterized in that: The following steps are involved: 1) Setting marking targets on multiple hydroacoustic devices of the conformal hydroacoustic device and arranging multiple reference points on the front side of the conformal hydroacoustic device; 2) Establish a three-dimensional coordinate system, determine the relative position of each reference point through a measuring instrument, and then determine the three-dimensional coordinates of each reference point; 3) Measure the three-dimensional coordinates of the marked target point by using a measuring instrument at the reference point; use a shooting device to obtain an image of the conformal hydroacoustic device, and measure the shooting device by using a measuring instrument at the reference point to obtain the three-dimensional coordinates of the shooting device at the shooting position; according to the three-dimensional coordinate position of the shooting device, the posture parameters of the shooting device when taking pictures, and the conformal hydroacoustic device image taken by the shooting device, use photogrammetry technology to calculate the three-dimensional coordinates of the feature points for coordinate calculation and the marked target point on each hydroacoustic device in the conformal hydroacoustic device; wherein, the center of the screw on the hydroacoustic device is selected as the feature point for coordinate calculation, and then the coordinates of the center of the hydroacoustic device are calculated according to the coordinates of the center of the screw; 4) Use a measuring instrument to measure the three-dimensional coordinates of the marked target point, and verify the three-dimensional coordinates of the marked target point calculated by photogrammetry. If the accuracy of the three-dimensional coordinates of the marked target point meets the requirements, the accuracy of the three-dimensional coordinates of the feature points used for coordinate calculation of each hydrophone calculated by photogrammetry meets the requirements; 5) According to the positional relationship between the characteristic points used for coordinate calculation on the hydrophone and the center point of the hydrophone, the three-dimensional coordinates of the center point of the hydrophone are calculated.

2. The three-dimensional coordinate measurement method of conformal hydroacoustic equipment according to claim 1, characterized in that: In step 1), a total station is used as a measuring instrument, and each reference point is arranged in an arc shape at intervals on the front side of the conformal hydroacoustic device; The reference points are a1, a2, ... a from left to right in the horizontal direction perpendicular to the centerline of the ship. n ; Divide the hydroacoustic devices on the conformal hydroacoustic device into n groups according to the positions of the reference points, with each group arranged left and right and at least one hydroacoustic device in each group having a marked target point; The measuring instruments at each reference point are used to observe the groups of hydrophones on the conformal hydroacoustic device, and the measuring instruments at two adjacent reference points observe the intersection angles of the marked targets on the same group of hydrophones.

3. The three-dimensional coordinate measurement method of conformal hydroacoustic equipment according to claim 1, characterized in that: Using a total station as a measuring instrument, the relative position of each reference point is determined by: Measuring instruments are set at each reference point at the same time, and the mutual angles and distances between the reference points are determined by the measuring instruments, thereby determining the three-dimensional coordinates of each reference point.

4. The three-dimensional coordinate measurement method of conformal hydroacoustic equipment according to claim 3, characterized in that: When determining the relative positions of the reference points, the method for determining the spacing l0 between two reference points is: Assume that the two reference points of the distance to be measured are reference point A and reference point B, set up measuring instruments at reference point A and reference point B, the on-site measurement distance between AB is l, set up a standard ruler on the horizontal side of reference point A and reference point B, the line connecting reference point A and reference point B is parallel to the standard ruler, select the left point on the standard ruler as L, the right point as R, and the distance LR is known as S; The included angle ∠LAB=L is measured and calculated at the reference point A and the reference point B respectively. A ∠RAB=R A , ∠LBA=L B , ∠RBA=R B , based on the similarity relationship and the intersection formula, we can get the following relationship: LR's distance calculation value S': according to: The AB distance is calculated to be l0.

5. The three-dimensional coordinate measurement method of conformal hydroacoustic equipment according to claim 1, characterized in that: In step 1), a color mark is applied to the center of the screw for identification of feature points for coordinate calculation.

6. The three-dimensional coordinate measurement method of conformal hydroacoustic equipment according to claim 1, characterized in that: The centers of multiple screws on the hydrophone are used as feature points for coordinate calculation. According to the coordinates of the centers of multiple screws on the hydrophone, the normal vector (a, b, c) of the hydrophone is calculated according to the least squares method and normalized:

7. The three-dimensional coordinate measurement method of conformal hydroacoustic equipment according to claim 1, characterized in that: The coordinate conversion formula between the screw center and the hydrophone center is: Where x and y are the coordinates of the image after centering required for calculation; I and J are the coordinates measured directly on the image; W and H are the image width and height; pixel is the size of a single pixel, x0 and y0 are the principal point coordinates of the camera; Δx and Δy are constants obtained by camera calibration.

8. The three-dimensional coordinate measurement method of a conformal hydroacoustic device according to any one of claims 1 to 4, characterized in that: When taking images by the shooting device in step 3), multiple images are overlapped in the left-right direction at a ratio of a% and in the up-down direction at a ratio of b% to obtain an overall image of the conformal hydroacoustic device, where a is greater than b.

9. The three-dimensional coordinate measurement method of a conformal hydroacoustic device according to any one of claims 1 to 4, characterized in that: The hydrophones are numbered before setting the marking targets in step 1).

Images