Laser radar positioning method using tank wall reflection mark in storage tank

Abstract

The invention is suitable for the technical field of laser radar measurement, and provides a laser radar positioning method using a tank wall reflection mark in a storage tank, and the method comprises the steps: taking a high-reflection material as a reflection mark, fixing the reflection mark on a tank wall in the storage tank, and carrying out the scanning through a laser radar; then finding a reflection mark fixed on the inner wall of the storage tank by using the reflection signal intensity of the scanned object, calculating the position positioning of the laser radar relative to the reflection mark according to the data information obtained by scanning, including the angle and distance information of the reflection mark, and then calculating the position of the laser radar through multiple coordinate system transformation. And finally obtaining the position positioning of the laser radar in the whole storage tank. Therefore, the method can accurately calculate the position of the laser radar in the storage tank, and the method is high in accuracy and convenient to operate.

Description

Technical Field

[0001] The invention belongs to the technical field of laser radar measurement, and in particular relates to a laser radar positioning method using tank wall reflection marks in a storage tank. Background Art

[0002] In petrochemical storage tanks, various liquids are usually stored, including oil, chemicals, etc. The internal structure of these tanks is complex and contains 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 tanks in long-term use. Therefore, accurate positioning is particularly important in the maintenance and inspection of storage tanks. In the past measurement work, the commonly used measurement methods mainly relied on manual operation. For example, positioning measurements are performed using tools such as steel rulers, tape measures or laser rangefinders. Although these methods can achieve preliminary positioning of a single steel plate or a single area in some cases, they have significant limitations. Especially in the complex environment inside the tank, manual measurement depends on the experience and technical level of the operator, and is easily interfered by human factors, resulting in measurement errors.

[0003] Through these manual distance measurement methods, positioning can only be achieved in a single steel plate or an area, but it is impossible to accurately locate the detailed position in the entire tank. For example, when multiple positioning measurements are performed, measurement errors will accumulate due to inconsistent operations or limited equipment accuracy, which will affect 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. What is more serious is that in large storage tanks, manual measurement cannot guarantee the accurate tracking of each component or position, especially when switching between various areas of the tank. The measurement error is often difficult to effectively control, resulting in the final positioning result may deviate from the actual position.

[0004] In addition, manual measurement usually cannot take into account the positional relationship of multiple components in the tank at the same time, which means that it can only complete the task locally and locally, and cannot provide a comprehensive and detailed positioning information. Although this traditional manual measurement method can temporarily meet the needs in some simple application scenarios, its limitations are becoming more and more obvious under the complex structure of the tank and the long-term high-precision positioning requirements. Summary of the invention

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

[0006] The present invention adopts the following technical solution:

[0007] A laser radar positioning method using tank wall reflection marks in a storage tank comprises the following steps:

[0008] Step S1, vertically attach at least three reflective marks to the inner wall of the storage tank;

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

[0010] Step S3, establishing a first coordinate system of the three reflection marks, and calculating the position of the laser radar in the first coordinate system according to the data information of the three reflection marks obtained by scanning the laser radar;

[0011] Step S4, establishing a second coordinate system parallel to the horizontal and vertical axes of the first coordinate system and circumscribing the storage tank, and converting the position of the laser radar in the first coordinate system into the position in the second coordinate system;

[0012] Step S5: According to the direction of the steel plate of the tank bottom plate, rotate the second coordinate system until the horizontal axis is parallel to the steel plate weld to obtain a third coordinate system tangential to the tank, and convert the position of the laser radar in the second coordinate system into the position in the third coordinate system, which is the position positioning of the laser radar in the tank.

[0013] Furthermore, in step S1, the reflective mark is made of a highly reflective material and is vertically attached to the tank wall.

[0014] Furthermore, in step S2, an intensity threshold is set. When the laser radar scans the periphery, an object whose returned signal intensity is greater than the intensity threshold is a reflection mark, and the distance and angle information of the reflection mark is obtained at the same time.

[0015] Furthermore, in step S3, three reflective marks are marked as three points in the tank, a straight line between any two points is used as the horizontal axis, and a perpendicular line through one of the points is used as the vertical axis to form the first coordinate system. The laser radar is recorded as point A, and any two points are point B and point C. Point B is the origin of the first coordinate system. The circumscribed circle of ΔBCD is the cross section of the tank. The position coordinates of the laser radar in the first coordinate system are (x1, y1): x1=ABcos∠ABC, y1=ABsin∠ABC, AB represents the distance between the laser radar and point B.

[0016] Furthermore, in step S4, the radius R of the circumscribed circle of ΔBCD is calculated according to the pairwise distances of the three reflective marks, the center of the circle is recorded 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 R-Rcos∠PBC, and the translation distance in the vertical axis direction is R-Rsin∠PBC. After coordinate conversion, the position coordinates of the laser radar in the second coordinate system are: (x2, y2) = (x1+R-Rcos∠PBC, y1+R-Rsin∠PBC).

[0017] Furthermore, in step S5, first obtain the angle θ between the steel plate weld and the horizontal axis of the second coordinate system, translate the second coordinate system to obtain the intermediate coordinate system, rotate the origin of the intermediate coordinate system by angle θ to obtain the third coordinate system, the third coordinate system is tangent to the storage tank, and the horizontal axis is parallel to the steel plate weld.

[0018] Furthermore, the translation distance of the second coordinate system in the horizontal direction is D X =OO”sin∠OO”Y”, the translation distance in the vertical axis direction is D Y =OO"cos∠OO"Y", where OO" is the distance between the origin 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: (x3, y3) = (x2 + D X ,y2-D Y ), the intermediate coordinate system rotates by angle θ with the origin, and the position coordinates of the laser radar in the third coordinate system are: (x R ,y R )=(x3cosθ+y3sinθ,x3sinθ-y3cosθ);

[0019]

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

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

[0022] The beneficial effects of the present invention are as follows: the present invention affixes multiple reflective marks in the storage tank, scans peripheral objects in the storage tank through the laser radar, performs calculations and multiple coordinate changes based on the scanned data, and finally accurately locates the position and direction of the laser radar in the storage tank. Compared with the current manual measurement, the use of laser radar for positioning has the advantages of high accuracy and convenient operation. At the same time, the use of laser radar for positioning has the advantages of eliminating human measurement errors and eliminating the cumulative errors caused by multiple measurements. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a flow chart of a laser radar positioning method using tank wall reflection marks in a storage tank provided by an embodiment of the present invention;

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

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

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

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

[0028] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0029] In order to accurately locate the position in the entire tank and eliminate manual measurement errors. The present invention provides a laser radar positioning method using tank wall reflection marks in a tank. This method is a positioning method assisted by high-reflective materials, which can achieve accurate coordinates and directions in the entire tank using laser radar. In order to illustrate the technical solution described in the present invention, it is described below through specific embodiments.

[0030] like Figure 1 As shown, the laser radar positioning method using the tank wall reflection mark in the storage tank provided in this embodiment includes a laser radar positioning method using the tank wall reflection mark in the storage tank, including the following steps:

[0031] Step S1, vertically attach at least three reflective marks to the inner wall of the storage tank.

[0032] The reflective marker is made of high-reflective material. In order to obtain detailed diameter data of the entire tank, at least three high-reflective materials need to be attached to the tank wall as reflective markers. These high-reflective material reflective markers should be attached vertically to the tank wall so that the high-reflective material information scanned by the laser radar at different positions and heights is consistent.

[0033] For the convenience of explanation, Figure 2 As shown, taking three reflective marks as an example, they are divided into object B, object C and object D, which are point B, point C and point D respectively in the figure.

[0034] Step S2: The laser radar in the storage tank scans peripheral objects in the horizontal plane, determines the reflection mark according to the signal strength, and selects to record the distance and angle information of at least three of the reflection marks.

[0035] Since the reflectivity of highly reflective materials is very high, the laser radar will receive very strong signal intensity data when scanning. By scanning the surrounding objects with the laser radar, the distance, angle, and intensity information between the laser radar and the surrounding objects can be obtained. In this step, by setting the intensity threshold, when the laser radar scans the periphery, the objects with the returned signal intensity greater than the intensity threshold are reflection marks. Therefore, the reflection mark data that meets the intensity requirements can be filtered out, and the distance and angle information of the reflection mark can be obtained at the same time.

[0036] Step S3, establish a first coordinate system for the three reflection marks, and calculate the position of the laser radar in the first coordinate system based on the data information of the three reflection marks obtained by scanning the laser radar.

[0037] The three reflective marks are marked as three points in the tank, and a straight line between two points is selected as the horizontal axis, and a vertical line through one point is selected as the vertical axis to form the first coordinate system, which is recorded as point A by the laser radar. Figure 2 Object B, object C, and object D are shown, and any two points are selected as point B and point C. 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 also the reflection mark coordinate system.

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

[0039] For example, for angle ∠ABC, we have It can be calculated Then ∠ABC can be calculated.

[0040] The position coordinates (x1, y1) and the orientation angle of the laser radar in the first coordinate system (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, through the above steps, we can obtain (x1, y1) = (ABcos∠ABC, ABsin∠ABC), as well as the distances BC, CD, BD between the three high-reflective material reflection marks and the angle ∠1-∠ACB of the laser radar in the first coordinate system X'BY'.

[0042] Step S4, establish a second coordinate system parallel to the horizontal and vertical axes of the first coordinate system and tangent to the storage tank, and convert the position of the laser radar in the first coordinate system into the position in the second coordinate system.

[0043] The present invention needs to determine the position of the laser radar in the coordinate system of the tank. Figure 3 As shown in the figure, the straight line L is the steel plate weld on the bottom plate of the tank. The coordinate system of the 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 axis is tangent to the tank. Therefore, after calculating the position of the laser radar in the first coordinate system, a series of calculations and coordinate transformations are required to transform the position coordinates of the laser radar to the third coordinate system.

[0044] The solution of this embodiment is as follows: Figure 3 As shown, first transform the first coordinate system X'BY' to the second coordinate system X"O"Y", the second coordinate system is obtained by translating the first coordinate system, the horizontal and vertical axes are parallel, and the horizontal and vertical axes of the second coordinate system are circumscribed 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, and the coordinate system X"O"Y" is obtained by translating the coordinate system X'BY'.

[0045] After obtaining the pairwise distances between the three reflective marks on the tank wall, that is, the distances between objects B, C and D, the circle formed by the tank is the circumscribed circle of ΔBCD, with the center of the circle being point P. The radius R of the entire tank can be calculated given the three sides, and the specific calculation process is not repeated here.

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

[0047] Step S5: According to the direction of the steel plate of the tank bottom plate, rotate the second coordinate system until the horizontal axis is parallel to the steel plate weld to obtain a third coordinate system tangential to the tank, and convert the position of the laser radar in the second coordinate system into the position in the third coordinate system, which is the position positioning of the laser radar in the tank.

[0048] like Figure 5 As shown in the figure, taking the steel plate weld in the steel plate direction of the tank bottom plate as a reference, a transverse weld line L parallel to the steel plate direction is selected, and the points K and G on the weld line L are positioned by laser radar to obtain the coordinates of point K and point G, i.e., the position of the weld line L. Then, the angle between the weld line L and the straight line BC can be obtained, i.e., the angle θ between the steel plate weld and the horizontal axis of the second coordinate system X”O”Y” can be obtained.

[0049] exist Figure 5 In the process, an intermediate coordinate system X1"OY1" is established, and the second coordinate system X"O"Y" is translated and transformed to obtain the intermediate coordinate system X1"OY1", and 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 tangent to the storage tank, and its horizontal axis is parallel to the steel plate weld.

[0050] In the specific calculation, point P is the center of the tank, then Calculation in ΔOO”P yields The second coordinate system X”O”Y”- is converted into the third coordinate system XOY by firstly transforming it into the intermediate coordinate system X1”OY1” through translation, and then transforming it into the third coordinate system OXY through rotation.

[0051] The coordinate system X”O”Y” translation transformation requires a translation distance D to the left in the O”X” direction X , move upward in the "Y" direction of O by a distance of D Y . It can be calculated that the translation distance of the second coordinate system in the horizontal direction is D X =OO”sin∠OO”Y”, the translation distance in the vertical axis direction is D Y=OO"cos∠OO"Y", where OO" is the distance between the origin 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: (x3, y3) = (x2 + D X ,y2-D Y ), the intermediate coordinate system X1”OY1” is rotated by angle θ from the origin O to obtain the third coordinate system XOY. The position coordinates of the laser radar in the third coordinate system are: (x R ,y R )=(x3cosθ+y3sinθ,x3sinθ-y3cosθ);

[0052]

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

[0054] It should also be noted that, since the data obtained by the laser radar will have a certain error value compared with the actual data, this embodiment can reduce the error by taking the average value through multiple calculations. Specifically, a straight line between two different points is selected as the horizontal axis each time to establish the first coordinate system, and the position coordinates of the laser radar in the third coordinate system calculated each time are averaged in the above manner to obtain the final position coordinates of the laser radar in the third coordinate system. For example, the above embodiment selects high-reflective material objects B and C as references for the first coordinate system for calculation. In order to obtain more accurate results, high-reflective material objects B, C and D can be used in pairs to calculate and take the average value in the above manner. Furthermore, more than 3 reflective marks can be set, and three of them can be selected for calculation. By taking the average value through multiple calculations, a more accurate result can be obtained. In addition, more reflective marks can also be attached to perform calculations when some reflective marks are blocked, which improves the adaptability range.

[0055] In summary, the present invention fixes the high-reflective material as a reflective mark on the tank wall inside the tank and scans it with a laser radar, and then uses the reflected signal intensity of the scanned object to find the reflective mark fixed on the inner wall of the tank, and calculates the position of the laser radar relative to the reflective mark based on the data information obtained by the scan, including the angle and distance information of the reflective mark, and then through multiple coordinate system transformations, finally obtains the position of the laser radar in the entire tank. Therefore, this method can accurately calculate the position of the laser radar in the tank, which is highly accurate and easy to operate.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A laser radar positioning method using tank wall reflection marks in a storage tank, characterized in that: The laser radar positioning method comprises the following steps: Step S1, vertically attach at least three reflective marks to the inner wall of the storage tank; Step S2, the laser radar in the storage tank scans the peripheral objects in the horizontal plane, determines the reflection mark according to the signal strength, and selects and records the distance and angle information of at least three of the reflection marks; Step S3, establishing a first coordinate system of the three reflection marks, and calculating the position of the laser radar in the first coordinate system according to the data information of the three reflection marks obtained by scanning the laser radar; Step S4, establishing a second coordinate system parallel to the horizontal and vertical axes of the first coordinate system and circumscribing the storage tank, and converting the position of the laser radar in the first coordinate system into the position in the second coordinate system; Step S5: According to the direction of the steel plate of the tank bottom plate, rotate the second coordinate system until the horizontal axis is parallel to the steel plate weld to obtain a third coordinate system tangential to the tank, and convert the position of the laser radar in the second coordinate system into the position in the third coordinate system, which is the position positioning of the laser radar in the tank.

2. The laser radar positioning method using tank wall reflection marks in a storage tank as claimed in claim 1 is characterized in that: In step S1, the reflective mark is made of highly reflective material and is vertically attached to the tank wall.

3. The laser radar positioning method using tank wall reflection marks in a storage tank as claimed in claim 1 is characterized in that: In step S2, an intensity threshold is set. When the laser radar scans the periphery, an object whose returned signal intensity is greater than the intensity threshold is a reflection mark, and the distance and angle information of the reflection mark is obtained at the same time.

4. The laser radar positioning method using tank wall reflection marks in a storage tank as claimed in claim 3 is characterized in that: In step S3, three reflective marks are marked as three points in the tank, a straight line through any two points is used as the horizontal axis, and a vertical line through one of the points is used as the vertical axis to form the first coordinate system. The laser radar is recorded as point A, and any two points are points B and C. Point B is the origin of the first coordinate system. The circumscribed circle of ΔBCD is the cross section of the tank. The position coordinates of the laser radar in the first coordinate system are (x1, y1): x1=ABcos∠ABC, y1=ABsin∠ABC, AB represents the distance between the laser radar and point B.

5. The laser radar positioning method using tank wall reflection marks in a storage tank as claimed in claim 4 is characterized in that: In step S4, the radius R of the circumscribed circle of ΔBCD is calculated according to the pairwise distances of the three reflective marks, and the center of the circle is recorded as point P. 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 R-Rcos∠PBC, and the translation distance in the vertical axis direction is R-Rsin∠PBC. After coordinate conversion, the position coordinates of the laser radar in the second coordinate system are: (x2, y2) = (x1+R-Rcos∠PBC, y1+R-Rsin∠PBC).

6. The laser radar positioning method using tank wall reflection marks in a storage tank as claimed in claim 5 is characterized in that: In step S5, first obtain the angle θ between the steel plate weld and the horizontal axis of the second coordinate system, translate the second coordinate system to obtain the intermediate coordinate system, rotate the origin of the intermediate coordinate system by angle θ to obtain the third coordinate system, the third coordinate system is tangent to the storage tank, and the horizontal axis is parallel to the steel plate weld.

7. The laser radar positioning method using tank wall reflection marks in a storage tank as claimed in claim 6 is characterized in that: The translation distance of the second coordinate system in the horizontal direction is D X =OO”sin∠OO”Y”, the translation distance in the vertical axis direction is D Y =OO"cos∠OO"Y", where OO" is the distance between the origin 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: (x3, y3) = (x2 + D X ,y2-D Y ), the intermediate coordinate system rotates by angle θ with the origin, and the position coordinates of the laser radar in the third coordinate system are: (x R ,y R )=(x3cosθ+y3sinθ,x3sinθ-y3cosθ); 8. The laser radar positioning method using tank wall reflection marks in a storage tank as claimed in claim 7 is characterized in that: The orientation angle of the laser radar in the third coordinate system is ∠1-∠ACB+θ, where ∠1 is the angle between the positive direction of the laser radar and point C.

9. The laser radar positioning method using tank wall reflection marks in a storage tank as claimed in any one of claims 4 to 8, characterized in that: Each time, a straight line between two different points is selected as the horizontal axis to establish the first coordinate system, and the position coordinates of the laser radar calculated each time in the third coordinate system are averaged to obtain the final position coordinates of the laser radar in the third coordinate system.

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