Laser radar positioning method using tank wall reflection sign in tank

Abstract

The application is suitable for the technical field of laser radar measurement, and provides a laser radar positioning method for a storage tank by using a tank wall reflection mark; high reflection material is fixed on the tank wall in the storage tank as the reflection mark, and then the laser radar is scanned; the reflection signal strength of the scanned object is used to find the reflection mark fixed on the inner wall of the storage tank; the position of the laser radar relative to the reflection mark is calculated according to the data information obtained by scanning, including the angle and distance information of the reflection mark; and then the position of the laser radar in the whole storage tank is obtained through multiple coordinate system transformations. Therefore, the position of the laser radar in the storage tank can be accurately calculated, and the method has high accuracy and is convenient to operate.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of laser radar measurement, and particularly relates to a laser radar positioning method using tank wall reflection marks in a storage tank. BACKGROUND

[0002] In petrochemical storage tanks, various liquids, including petroleum, chemicals, etc., are usually stored. The internal structure of these storage tanks is complex, containing multiple key components such as floating roof rods, heating coils, sacrificial anodes, etc. These components are crucial to the safety, functionality, and reliability of the storage tank during long-term use. Therefore, accurate positioning is particularly important in the maintenance and detection of storage tanks. In the past measurement work, the commonly used measurement means mainly relies on manual operation. For example, using a steel ruler, tape measure or laser range finder and other tools for positioning measurement. These methods can achieve preliminary positioning of a single steel plate or a single area in some cases, but they have significant limitations. Especially in the complex environment inside the storage tank, manual measurement depends on the experience and technical level of the operator, and is easily disturbed by human factors, resulting in measurement errors.

[0003] Through these manual ranging methods, only positioning in a single steel plate or a single area can be achieved, and the detailed position in the entire storage tank cannot be accurately positioned. For example, when multiple positioning measurements are performed, measurement errors will accumulate due to inconsistent operation or limitations of equipment precision, thereby affecting the accuracy of positioning. This not only makes the repeatability and reliability of the positioning results poor, but also increases the workload and time cost of manual measurement. More seriously, in a large storage tank, manual measurement cannot guarantee accurate tracking of each component or position, especially when switching between different areas of the storage tank, measurement errors are often difficult to effectively control, resulting in the final positioning result may deviate from the actual position.

[0004] In addition, manual measurement usually cannot consider the positional relationship of multiple components in the storage tank, resulting in only partial and limited completion of the task, and cannot provide a comprehensive and detailed positioning information. This traditional manual measurement method, although can temporarily meet the demand in some simple application scenarios, its limitations become more and more obvious under the requirements of complex internal structure of the storage tank and long-time high-precision positioning. SUMMARY

[0005] In view of the above problems, the purpose of the present application is to provide a laser radar positioning method using tank wall reflection marks in a storage tank, aiming to solve the technical problems of large error and inability to adapt to the measurement of complex internal structure of the storage tank under the existing manual measurement method.

[0006] The present application adopts the following technical solutions:

[0007] A kind of tank inside laser radar positioning method using tank wall reflection sign, comprising the following steps:

[0008] Step S1, at least three reflection signs are vertically pasted in the inner wall of the storage tank;

[0009] Step S2, the laser radar in the storage tank scans the peripheral object in horizontal plane, determines the reflection sign according to signal strength, at least selects the distance and angle information of three reflection signs;

[0010] Step S3, the first coordinate system of the three reflection signs is established, the position of the laser radar in the first coordinate system is calculated according to the data information of the three reflection signs obtained by laser radar scanning;

[0011] Step S4, the second coordinate system is established by parallel to the horizontal and vertical axis direction of the first coordinate system and circumscribed to the storage tank, the position of the laser radar in the first coordinate system is converted into the position in the second coordinate system;

[0012] Step S5, according to the direction of the steel plate of the tank bottom plate, the second coordinate system is rotated until the horizontal axis is parallel to the steel plate weld, the third coordinate system circumscribed to the storage tank is obtained, the position of the laser radar in the second coordinate system is converted into the position in the third coordinate system, that is, the position of the laser radar in the storage tank is positioned.

[0013] Further, in step S1, the reflection sign is high-reflective material, and is vertically pasted on the tank wall.

[0014] Further, in step S2, an intensity threshold is set, and when the laser radar scans the periphery, the object with the signal strength greater than the intensity threshold is the reflection sign, and the distance and angle information of the reflection sign are obtained.

[0015] Further, in step S3, the three reflection signs are marked as three points in the tank, and the straight line of the optional two points is the horizontal axis, and the vertical line passing through one of the points is the vertical axis, to form the first coordinate system, the laser radar is marked as point A, and the optional two points are point B and point C, point B is the origin of the first coordinate system, and the circumscribed circle of ΔBCD is the cross section of the storage tank, and the position coordinates (x1, y1) of the laser radar in the first coordinate system are x1=ABcos ∠ABC and y1=ABsin ∠ABC, wherein AB represents the distance between the laser radar and point B.

[0016] Further, in step S4, the circumradius R of triangle ABC is calculated according to the distances between any two of the three reflection markers, and the center of the circumcircle is denoted as point P. A second coordinate system is obtained by translating the first coordinate system, specifically, the first coordinate system is translated by a distance of R-Rcos∠PBC in the horizontal direction and a distance of R-Rsin∠PBC in the vertical direction. After the coordinate transformation, the position coordinates of the laser radar in the second coordinate system are (x2, y2) = (x1+R-Rcos∠PBC, y1+R-Rsin∠PBC).

[0017] Further, in step S5, the angle θ between the weld of the steel plate and the horizontal axis of the second coordinate system is first obtained, and then the second coordinate system is translated to obtain an intermediate coordinate system. The intermediate coordinate system is rotated by an angle θ about the origin of the intermediate coordinate system to obtain a third coordinate system. The third coordinate system is tangent to the storage tank, and the horizontal axis is parallel to the weld of the steel plate.

[0018] Further, the translation distance of the second coordinate system in the horizontal direction is D X =OO”sin∠OO”Y”, and the translation distance of the second coordinate system in the vertical direction is D Y =OO”cos∠OO”Y”, where OO” is the distance between the origins of the second coordinate system and the intermediate coordinate system, OO”=2R(1-cosθ), The position coordinates of the laser radar in the intermediate coordinate system are (x3, y3) = (x2+D X , y2-D Y ), and the intermediate coordinate system is rotated by an angle θ about the origin. The position coordinates of the laser radar in the third coordinate system are (x R , y R ) = (x3cosθ+y3sinθ, x3sinθ-y3cosθ).

[0019]

[0020] Further, the orientation angle of the laser radar in the third coordinate system is ∠1-∠ACB+θ, where ∠1 is the angle between the forward direction of the laser radar and point C.

[0021] Further, a straight line passing through different two points is selected as the horizontal axis to establish the first coordinate system each time. The position coordinates of the laser radar in the third coordinate system calculated each time are averaged to obtain the final position coordinates of the laser radar in the third coordinate system.

[0022] The beneficial effects of the present application are: the present application pastes a plurality of reflective markers in the storage tank, scans the peripheral object in the storage tank through the laser radar, calculates and changes the coordinates multiple times according to the scanning data, and finally can accurately locate the position and direction of the laser radar in the storage tank. Compared with the current manual measurement, the laser radar positioning has the advantages of high accuracy, convenient operation and the like. At the same time, the laser radar positioning has the advantages of eliminating human measurement error and eliminating cumulative error caused by multiple measurements. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a flow chart of the laser radar positioning method in the storage tank using the tank wall reflective marker provided by the embodiment of the present application;

[0024] Figure 2 is a positioning schematic diagram of the laser radar in the first coordinate system;

[0025] Figure 3 is a positioning schematic diagram of the laser radar in the third coordinate system;

[0026] Figure 4 is a schematic diagram of the first coordinate system transformed to the second coordinate system;

[0027] Figure 5 is a schematic diagram of the second coordinate system transformed to the third coordinate system. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0029] In order to accurately locate the position in the entire storage tank and eliminate the human measurement error, the present application provides a laser radar positioning method in the storage tank using the tank wall reflective marker, which is a positioning method assisted by high-reflective material, and can locate the accurate coordinates and direction in the entire storage tank by using the laser radar. In order to explain the technical scheme of the present application, the specific embodiments are described below.

[0030] As shown in Figure 1 , the laser radar positioning method in the storage tank using the tank wall reflective marker provided by the embodiment of the present application includes a laser radar positioning method in the storage tank using the tank wall reflective marker, which includes the following steps:

[0031] Step S1, vertically paste at least three reflective markers on the inner wall of the storage tank.

[0032] The reflective markers are high-reflective materials. In order to obtain detailed diameter data of the whole storage tank, at least three high-reflective materials are needed to be pasted on the tank wall as reflective markers. The high-reflective materials should be pasted vertically on the tank wall so that the high-reflective material information scanned by the laser radar at different positions and different heights is consistent.

[0033] For the convenience of description, as shown in the drawings, three reflective markers are taken as examples, which are divided into object B, object C and object D, and are sequentially point B, point C and point D. Figure 2

[0034] Step S2, the laser radar in the storage tank scans the peripheral object in the horizontal plane, and determines the reflective markers according to the signal strength, and at least selects the distance and angle information of three reflective markers.

[0035] Since the reflectivity of the high-reflective material is very high, when the laser beam of the laser radar is scanned, very strong signal strength data will be received. By scanning the peripheral object by the laser radar, the distance, angle and intensity information between the laser radar and the peripheral object can be obtained. In this step, by setting an intensity threshold, the object whose returned signal strength is greater than the intensity threshold is the reflective marker when the laser radar is scanned, so the reflective marker data meeting the intensity requirement can be filtered out, and the distance and angle information of the reflective marker is obtained.

[0036] Step S3, a first coordinate system of the three reflective markers is established, and the position of the laser radar in the first coordinate system is calculated according to the data information of the three reflective markers obtained by the laser radar scanning.

[0037] The three reflective markers are marked as three points in the tank, and a straight line between any two points is the horizontal axis, and a vertical line passing through one of the points is the vertical axis, to form the first coordinate system, and the laser radar is marked as point A. As shown in the drawings, the object B, the object C and the object D, and any two points are point B and point C, and the point B is the origin (0, 0) of the first coordinate system, and the direction of BC is the positive direction of the horizontal axis to establish a plane rectangular coordinate system, that is, the first coordinate system X'BY', which is the reflective marker coordinate system. Figure 2

[0038] In step S2, the distance AB between the laser radar A and the object B and the angle ∠2 between the positive direction of the laser radar and the object B, the distance AC between the laser radar A and the object C and the angle ∠1 between the positive direction of the laser radar and the object C are obtained. ∠BAC = ∠2- ∠1 is obtained, and the distance between the object B and the object C can be calculated. The circumcircle of ΔBCD is the cross section of the storage tank, and after the three side lengths and one vertex angle of the known triangle are obtained, the angles of the other two vertex angles, that is, ∠ABC and ∠ACB, can be calculated.

[0039] For example, for the angle ∠ABC,​​ The angle ABC can be calculated. The angle ABC can be calculated.

[0040] The position coordinates (x1, y1) of the laser radar in the first coordinate system and the orientation angle (with the X' axis as 0° and the counterclockwise direction as the positive direction) can be obtained. x1 = ABcos∠ABC, y1 = ABsin∠ABC, and the orientation angle of the laser radar is ∠1-∠ACB.

[0041] Therefore, (x1, y1) = (ABcos∠ABC, ABsin∠ABC) can be obtained by the above steps, and the distances BC, CD, and BD between the three high-reflective material reflection markers and the angle ∠1-∠ACB of the laser radar in the first coordinate system X'BY' can be obtained.

[0042] Step S4: A second coordinate system is established by externally tangent to the storage tank in the direction parallel to the horizontal and vertical axes of the first coordinate system, and the position of the laser radar in the first coordinate system is converted into the position in the second coordinate system.

[0043] The present application needs to determine the position of the laser radar in the coordinate system of the storage tank. As shown in Figure 3 The straight line L is the steel plate weld on the bottom plate of the storage tank, and the coordinate system of the storage tank is defined as the third coordinate system XOY. The X axis of the third coordinate system is parallel to the steel plate weld L, and the XY axes are both externally tangent to the storage tank. Therefore, after the position of the laser radar in the first coordinate system is calculated, a series of calculations and coordinate transformations are needed to convert the position coordinates of the laser radar to the third coordinate system.

[0044] The scheme of the present embodiment is as shown in Figure 3 The first coordinate system X'BY' is transformed to the second coordinate system X"O"Y" as shown. The second coordinate system is obtained by translation of the first coordinate system, and the horizontal and vertical axes are both parallel. The horizontal and vertical axes of the second coordinate system are both externally tangent to the storage tank, that is, the coordinate axis O"X" and the coordinate axis O"Y" are tangent to the circle formed by the entire storage tank. The coordinate system X"O"Y" is obtained by translation of the coordinate system X'BY'.

[0045] After obtaining the distances between the three reflection markers on the tank wall, that is, the distances between the objects B, C, and D, the circle formed by the storage tank is the circumscribed circle of triangle ABCD, and the center is point P. The radius R of the entire storage tank can be obtained by knowing the three sides, and the specific calculation process is not described.

[0046] The second coordinate system is obtained by translating the first coordinate system. The distance to be translated in the horizontal direction (O"X" axis) of the first coordinate system is R - Rcos∠PBC, and the distance to be translated in the vertical direction (O"Y" axis) is R - Rsin∠PBC. The lengths of the three sides BC, PB = R, and PC = R in ΔPBC are known, so ∠PBC can be calculated by taking any vertex. The coordinates (x1, y1) in the first coordinate system X'BY' can be converted to coordinates (x2, y2) in the second coordinate system X"O"Y". That is, after coordinate transformation, the position coordinates of the lidar in the second coordinate system are: (x2, y2) = (x1 + R - Rcos∠PBC, y1 + R - Rsin∠PBC).

[0047] Step S5: Based on the direction of the steel plate of the tank bottom plate, rotate the second coordinate system until the horizontal axis is parallel to the weld of the steel plate to obtain the third coordinate system tangent to the tank. Convert the position of the lidar in the second coordinate system to the position in the third coordinate system, which is the position positioning of the lidar inside the tank.

[0048] like Figure 5 As shown, taking the steel plate weld in the direction of the bottom plate of the storage tank as a reference, a transverse weld line L parallel to the direction of the steel plate is selected. Points K and G on the weld line L are located once using a lidar to obtain the coordinates of point K and point G, that is, the position of the weld line L. Then, the angle between the weld line L and the straight line BC can be obtained, that is, the angle θ between the steel plate weld and the horizontal axis of the second coordinate system X”O”Y”.

[0049] exist Figure 5 In the process, an intermediate coordinate system X1”OY1 is established. The second coordinate system X”O”Y” is translated and transformed to obtain the intermediate coordinate system X1”OY1. The origin of the intermediate coordinate system X1”OY1” is rotated by an angle θ to obtain the third coordinate system OXY. The third coordinate system is externally tangent to the storage tank, and its horizontal axis is parallel to the weld seam of the steel plate.

[0050] In the specific calculation, point P is the center of the storage tank, then The result can be obtained by calculating in ΔOO”P. To transform the second coordinate system X”O”Y”- into the third coordinate system XOY, we can first perform a translation transformation to obtain the intermediate coordinate system X1”OY1, and then perform a rotation transformation to obtain the third coordinate system OXY.

[0051] The coordinate system X”O”Y” translation transformation requires shifting it to the left by a distance D in the O”X” direction. X Translate upwards by a distance D in the O"Y" direction. Y Calculations show that the translation distance of the second coordinate system along the horizontal axis is D. X =OO”sin∠OO”Y”, the translation distance along the vertical axis is D. Y= OO"cos ∠OO"Y", wherein OO" is the distance between the origins of the second coordinate system and the intermediate coordinate system, OO" = 2R(1-cosθ), The position coordinates of the laser radar in the intermediate coordinate system are (x3, y3) = (x2+D X ,y2-D Y ), The intermediate coordinate system X1"OY1" is rotated by an angle θ to obtain a third coordinate system XOY, and the position coordinates of the laser radar in the third coordinate system are (x R ,y R ) = (x3cosθ+y3sinθ, x3sinθ-y3cosθ).

[0052]

[0053] Meanwhile, it can be obtained that the orientation angle of the laser radar in the third coordinate system is ∠1-∠ACB+θ, and ∠1 is the angle between the forward direction of the laser radar and point C.

[0054] In addition, it should be noted that since the data obtained by the laser radar has a certain error value from the actual value, the embodiment can reduce the error by averaging multiple calculations. Specifically, a straight line passing through different two points is selected as the horizontal axis to establish a first coordinate system, and the position coordinates of the laser radar in the third coordinate system calculated each time are averaged according to the above method to obtain the final position coordinates of the laser radar in the third coordinate system. For example, the above embodiment selects the high-reflective material object B and object C as the reference for calculating the first coordinate system, and in order to obtain more accurate results, the high-reflective material object B, object C and object D can be combined in pairs to calculate and average according to the above method. Further, more than three reflective markers can be set, and three of them can be selected for calculation, and the more accurate results can be obtained by averaging multiple calculations. In addition, more reflective markers can also be used for calculation in the case that some reflective markers are blocked, thereby improving the adaptability.

[0055] In summary, the high-reflective material is fixed on the tank wall in the storage tank as a reflective marker and scanned by the laser radar, and then the reflective signal strength of the scanned object is used to find the reflective marker fixed on the inner wall of the storage tank. According to the data information obtained by scanning, including the angle and distance information of the reflective marker, the position of the laser radar relative to the reflective marker is calculated, and then through multiple coordinate system transformations, the position of the laser radar in the entire storage tank is finally obtained. Therefore, this method can accurately calculate the position of the laser radar in the storage tank, and this method has high accuracy and is convenient to operate.

[0056] The above merely describes preferred embodiments of the present application, and is not used to limit the present application, any modification, equivalent replacement and improvement within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for positioning a LIDAR using a tank wall reflective sign inside a storage tank, characterized by, The laser radar positioning method comprises the following steps: Step S1, vertically paste at least three reflective markers on the inner wall of the storage tank; Step S2, the laser radar in the storage tank scans the peripheral object in the horizontal plane, determines the reflective marker according to the signal strength, and at least selects to record the distance and angle information of three reflective markers; Step S3, establishing the first coordinate system of the three reflection marks, calculating the position of the laser radar in the first coordinate system according to the data information of the three reflection marks obtained by the laser radar scanning; wherein the three reflection marks are marked as three points in the tank, which are point B, point C and point D in turn, the straight line of the two points B and C is the horizontal axis, and the vertical line passing through one of the points is the vertical axis, to form the first coordinate system, and the laser radar is marked as point A, and point B is the origin of the first coordinate system, The circumcircle of the three reflection marks is the cross section of the tank, and the position coordinates of the laser radar in the first coordinate system are : , AB represents the distance between the laser radar and point B; Step S4, in the direction of the horizontal and vertical axes of the first coordinate system, a second coordinate system is established outside the storage tank, and the position of the laser radar in the first coordinate system is converted into the position in the second coordinate system; Step S5, according to the direction of the steel plate of the tank bottom plate, the second coordinate system is rotated until the horizontal axis is parallel to the steel plate weld, a third coordinate system is obtained outside the storage tank, and the position of the laser radar in the second coordinate system is converted into the position in the third coordinate system, that is, the position of the laser radar in the storage tank is positioned.

2. The method of claim 1, wherein the laser radar positioning method using the tank wall reflection sign in the tank is characterized by, In step S1, the reflective marker is a high-reflective material and is vertically pasted on the tank wall.

3. The method of claim 1, wherein the laser radar positioning method using the reflection of the tank wall sign in the tank is characterized by, In step S2, a strength threshold is set, when the laser radar scans the periphery, the object with the signal strength greater than the strength threshold is the reflective marker, and the distance and angle information of the reflective marker are obtained.

4. The method of claim 3, wherein the laser radar positioning method using the tank wall reflection sign in the tank is characterized by, In step S4, the distance between any two of the three reflection markers is calculated The radius of the circumscribed circle , the center of the circle is denoted as point P, and the second coordinate system is obtained by translating the first coordinate system, specifically: the translation distance of the first coordinate system in the horizontal axis direction is , and the translation distance in the vertical axis direction is After coordinate transformation, the position coordinates of the laser radar in the second coordinate system are: .

5. The method of claim 4, wherein the laser radar positioning method using the tank wall reflection sign in the tank is characterized by, In step S5, the angle between the steel plate weld and the horizontal axis of the second coordinate system is first acquired The second coordinate system is translated to obtain an intermediate coordinate system, and the origin of the intermediate coordinate system is rotated by the angle to obtain a third coordinate system, the third coordinate system circumscribes the storage tank, and the horizontal axis is parallel to the steel plate weld.

6. The method of claim 5, wherein the laser radar positioning method using the tank wall reflection sign in the tank is characterized by, The translation distance of the second coordinate system in the horizontal axis direction is The translation distance in the vertical axis direction is Wherein is the distance between the origin of the second coordinate system and the intermediate coordinate system, is the vertical axis of the second coordinate system, , The position coordinates of the laser radar in the intermediate coordinate system are: The intermediate coordinate system rotates an angle The position coordinates of the laser radar in the third coordinate system are: ; ； 。 7. The method of claim 6, wherein the laser radar positioning method using the tank wall reflection sign in the tank is characterized by, The angle of orientation of the lidar in the third coordinate system is , is the angle between the positive direction of the lidar and point C.

8. The method of claim 1-7, wherein the tank is characterized by, Each time, a straight line of different two points is selected as the horizontal axis to establish the first coordinate system, the position coordinates of the laser radar in the third coordinate system calculated each time are averaged, and the final position coordinates of the laser radar in the third coordinate system are obtained.

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