Diamond liquid tank volume measurement and calculation method
Through three-dimensional laser scanning and segmentation algorithms, accurate volume measurements are performed on the cargo hold of the liquefied natural gas transport ship, solving the problems of low accuracy, complex operation and high cost in the existing technology, and achieving more efficient and accurate volume measurements.
Patent Information
- Application Number
- CN202510305135.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-14
- Publication Date
- 2025-06-17
AI Technical Summary
When measuring the volume of the cargo hold of the liquefied natural gas transport ship, the prior art has problems of low accuracy, complex operation and high cost, which cannot meet the actual needs of the natural gas ship.
A three-dimensional laser scanner is used to scan the diamond tank in all directions, obtain point cloud data, extract three-dimensional coordinate data of 16 corner points, and divide the diamond tank into multiple tetrahedrons through a grid-based point acquisition and segmentation algorithm, calculate its volume, and correct the volume difference between the equivalent plane and the actual surface through the wall grid.
Improves the accuracy of volume measurement, simplifies operational processes, reduces costs, and enables more accurate measurement of the volume of the cargo hold of the LNG transport ship.
Smart Images
Figure CN120160693A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of ship engineering, and particularly relates to a method for measuring and calculating the volume of a rhombic liquid tank, such as the cargo tank of a liquefied natural gas carrier and similar rhombic liquid tanks used as fuel tanks in other ship types. Background Art
[0002] With the continuous growth of global energy demand and increasingly strict environmental protection requirements, natural gas, as a clean and efficient energy source, has seen a continuous increase in its transportation demand. As the main tool for transporting natural gas, liquefied natural gas carriers, the accurate measurement and calculation of the volume of their liquid cargo tanks are crucial for the operation and safety of the ships.
[0003] The cargo tanks of liquefied natural gas carriers (LNG) operate under low temperature and high pressure conditions, and the accuracy requirements for volume measurement are higher than those of ordinary oil tanker cargo tanks. Generally, the maximum allowable error is required to be controlled within 0.1%. In the calculation of the volume of liquefied natural gas carrier cargo tanks, the methods of shape measurement, hull modeling, and volume calculation all have their particularities. Currently, the commonly used methods for measuring and calculating the volume of liquid cargo tanks have problems such as low accuracy, complex operation, and high cost, and cannot meet the actual needs of natural gas carriers. Therefore, it is necessary to invent a new measurement and calculation method to improve measurement accuracy, simplify the operation process, and reduce costs. Summary of the Invention
[0004] In view of the above-mentioned disadvantages of the prior art, the present invention provides a method for measuring and calculating the volume of a rhombic liquid tank, including the following steps:
[0005] S1: Use a three-dimensional laser scanner to perform a full-range scan of the interior of the rhombic liquid tank to obtain point cloud data, extract the three-dimensional coordinate data of 16 corner points of the rhombic liquid tank, and perform grid sampling on each surface of the rhombic liquid tank to obtain the wall grid and the true corner point coordinates of each wall grid; the rhombic liquid tank is a lying octagonal prism, including two end faces and eight side faces, the two end faces are the bow face and the stern face and are both octagons, and the eight side faces are rectangular faces;
[0006] S2: Cut and divide the 16 corner points of the rhombic liquid tank. For the 8 corner points of the end face, select one corner point as the common point, and connect this common point with the other 5 non-adjacent corner points to form 5 first dividing lines, thereby dividing the end face into 6 triangles. The connection line of the common points of the bow face and the stern face is parallel to the bow-stern direction; each of the eight side faces has 4 corner points, and the eight side faces are respectively connected along their diagonals to form 1 second dividing line, thereby dividing each side face into 2 triangles. Finally, the cabin wall of the rhombic liquid tank is divided into 28 triangular faces, becoming an icosahedron, and each triangular face is an equivalent plane formed by connecting three corner points;
[0007] S3: Divide the icosahedron of the rhombic liquid tank into 6 triangular prisms. Divide a single triangular prism into 3 tetrahedrons. Calculate the volume of each tetrahedron based on the coordinates of the tetrahedron's corner points and sum them up to obtain the volume Va of the icosahedron.
[0008] Optionally, step S3 specifically includes:
[0009] The first dividing line extends in the fore-and-aft direction to form a first dividing surface. 5 first dividing surfaces divide the rhombic liquid tank into 6 triangular prisms; adjacent triangular prisms have rectangular interfaces. For the interface, draw 1 third dividing line along the diagonal connection. A single triangular prism is divided into an octahedron by the second cutting line and the third cutting line;
[0010] For a single triangular prism, there are a total of three dividing lines, including at least 1 second dividing line and at least 1 third dividing line. The three dividing lines form two intersection points at the corner points of the triangular prism. The three dividing lines form 2 second dividing surfaces. Divide the triangular prism into 3 tetrahedrons along the second dividing surfaces; the corner points of the divided tetrahedrons are the corner points of the original rhombic liquid tank. Calculate the volume of each tetrahedron by the vector method based on the coordinates of the tetrahedron's corner points.
[0011] Optionally, the size of a single wall grid is 1m * 1m.
[0012] Optionally, it further includes:
[0013] S4: Set the reference plane as the X-Y plane. Draw auxiliary lines along the Z direction perpendicular to the reference plane. The auxiliary lines pass through the 4 true corner points of each wall grid. The auxiliary lines intersect with the equivalent plane formed during the division of the rhombic liquid tank to form 4 mapping points. The 4 mapping points enclose a mapping surface. The volume of the polyhedron formed by the wall grid, its corresponding mapping surface, and the 4 auxiliary lines is the correction amount V C ; if the mapping point is closer to the center of the rhombic liquid tank than the true corner point, it means the actual volume of the liquid tank is larger than the modeled icosahedron, and V C is a positive value; otherwise, V C is a negative value. The final volume of the rhombic liquid tank obtained is Va + V C .
[0014] Optionally, in step S4, the solution process of V C includes:
[0015] Determine the offset plane. The wall grid and the mapping surface are located between the reference plane and the offset plane. The offset plane is parallel to the reference plane and is separated by a preset distance. The volume of the polyhedron formed by the wall grid, its corresponding offset plane, and the 4 auxiliary lines is V2. The volume of the polyhedron formed by the mapping surface, its corresponding offset plane, and the 4 auxiliary lines is V3. |V C | = |V2 - V3|.
[0016] Optionally, the preset distance is 1000 mm.
[0017] Optionally, the four real corner points of the wall grid are obtained by measurement in step S1 and are known quantities; while the X and Y values of the coordinates of the mapping points are the same as those of the real corner points, and the Z value needs to be solved. The solving process is as follows: The equivalent plane is the plane formed by connecting three corner points of the rhombic liquid tank. First, determine which equivalent plane the mapping point is located in, then obtain the plane equation of the equivalent plane where it is located according to the coordinates of the three corner points, and then substitute the X and Y values of the mapping point into the plane equation of the equivalent plane to finally obtain the Z value.
[0018] Optionally, for the volume calculation of V2, set the 4 corner points of the wall grid as K2L2M2N2. Since the wall grid is not a plane, the wall grid is fitted into multiple sub-planes by the approximation method to finally obtain a volume value approaching the true value; specifically including:
[0019] Establish two diagonals L2N2 and K2M2. The diagonal L2N2 extends along the Z direction to form a first cutting plane, and the first cutting plane divides the polyhedron represented by V2 into two triangular prisms V21 and V22 along the Z direction; the diagonal K2M2 extends along the Z direction to form a second cutting plane, and the second cutting plane divides the polyhedron represented by V2 into two triangular prisms V23 and V24. Then V2 = (V21 + V22 + V23 + V24) / 2.
[0020] Optionally, the values of V21, V22, V23, V24, and V3 are solved by the method of decomposing the triangular prism into tetrahedrons in step S3.
[0021] Optionally, the method for determining which equivalent plane the mapping point is located in includes the area method; set the mapping point as P, and the 3 corner points of the equivalent plane as A, B, and C. Calculate the area S△ of triangle ABC and the areas S1, S2, and S3 of the 3 small triangles formed by point P and the three vertices of the triangle respectively. If S△ = S1 + S2 + S3, it means that point P is inside triangle ABC, otherwise, it is outside.
[0022] As described above, the present invention provides a method for measuring and calculating the volume of a rhombic liquid tank. This volume measurement and calculation method uses a three-dimensional laser scanner to perform an all-round scan of the interior of the rhombic liquid tank, obtaining a large amount of point cloud data. Grid points are taken for each surface, and the three-dimensional coordinate data of 16 corner points are extracted. Due to construction deviations, the actual rhombic liquid tank is not a standard decahedron, and each corner point is not strictly in the same plane according to the design drawings. Therefore, the entire rhombic liquid tank is divided into multiple tetrahedrons to make it closer to the actual liquid tank condition. For a single tetrahedron obtained by segmentation, there is still a certain deviation from the actual liquid tank. Since the construction of the tetrahedron model is based on four corner points, the surfaces of the constructed tetrahedron model are all equivalent planes connected by corner points and cannot present the concave and convex state of the actual surface. Therefore, the volume difference between the equivalent plane and the actual surface is calculated through the grid of each wall surface for correction. Through the volume segmentation and grid correction of the present invention, errors can be eliminated as much as possible, the measurement accuracy can be improved, and finally a volume value approaching the actual liquid tank can be obtained. Description of the Drawings
[0023] Figure 1 It shows a schematic structural diagram of the rhombic liquid tank in the first embodiment of the present invention.
[0024] Figure 2 It shows a schematic diagram of the surface point cloud of the rhombic liquid tank in the first embodiment of the present invention.
[0025] Figure 3 It shows a schematic diagram of grid point selection of the rhombic liquid tank in the first embodiment of the present invention.
[0026] Figure 4 It shows a cutting schematic diagram of the rhombic liquid tank in the first embodiment of the present invention.
[0027] Figure 5 It shows a cutting schematic diagram of an octahedron cut into 3 tetrahedrons in the first embodiment of the present invention.
[0028] Figure 6 It shows a schematic diagram of the grid and dividing lines in the first embodiment of the present invention.
[0029] Figure 7 It shows a schematic structural diagram of the mapping surface and the offset surface in the first embodiment of the present invention;
[0030] Figure 8 It shows a schematic diagram of judging whether a point is inside a triangle in the first embodiment of the present invention;
[0031] Figure 9 It shows a schematic diagram of the fitting plane of the actual grid in the first embodiment of the present invention; Detailed Embodiment
[0032] The following describes the implementation manners of the present invention through specific specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.
[0033] When detailing the embodiments of the present invention, for the convenience of description, the cross-sectional views showing the device structure will be enlarged locally in a non-general proportion, and the schematic diagrams are only examples and should not limit the scope of protection of the present invention here. In addition, in actual production, three-dimensional spatial dimensions including length, width, and depth should be included.
[0034] For the convenience of description, spatial relationship terms such as "below", "beneath", "lower than", "under", "above", "on" may be used herein to describe the relationship between an element or feature shown in the drawings and other elements or features. It will be understood that these spatial relationship terms are intended to encompass other directions of the device in use or operation in addition to the directions depicted in the drawings. In addition, when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or there can also be one or more intervening layers. As used herein, "between... and..." means including the endpoint values.
[0035] In the context of the present application, the structure in which the first feature is "above" the second feature described may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.
[0036] It should be noted that the diagrams provided in this embodiment only illustrate the basic concept of the present invention in a schematic manner. Therefore, only the components related to the present invention are shown in the diagrams, rather than being drawn according to the number, shape, and size of the components in actual implementation. The types, quantities, and proportions of the components in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.
[0037] Embodiment 1
[0038] As Figures 1 to 9 shown, this embodiment provides a method for measuring and calculating the volume of a rhombic liquid tank, including the following steps:
[0039] Step S1: Use a three-dimensional laser scanner to perform a full-range scan of the interior of the rhombic liquid tank to obtain a large amount of point cloud data. Then process these data through professional software. As Figure 1As shown, the rhomboid liquid tank is in the shape of a horizontal octagonal prism, including two end faces and eight side faces. The two end faces are the bow face and the stern face, both of which are octagons and each includes 8 corner points; the eight side faces are rectangular faces.
[0040] First, utilize the function of the intersection of three planes to generate the corner points of the liquid cargo tank, and extract the three-dimensional coordinate data of 16 corner points.
[0041] Secondly, utilize the function of taking points by single-sided meshing, as Figure 2 、 Figure 3 shown, perform meshing and point taking on each face to obtain the wall grid, and the grid size is 1m * 1m or any other size. Obtain the true corner point coordinates of each wall grid. The wall grid is used to generate the flatness data of the cabin wall surface, and its geometric information is a continuous triangular or quadrilateral grid.
[0042] Due to construction deviations, the actual rhomboid liquid tank is not a standard decahedron. For example, the eight corner points of its bow face are not in the same vertical plane, but there is a certain front-back dislocation. This application takes into account these dislocation situations and divides the entire rhomboid liquid tank into multiple tetrahedrons to make it closer to the actual liquid tank condition. For a single tetrahedron divided, there is still a certain deviation from the actual liquid tank. Since the construction of the tetrahedron model is based on four corner points, the surfaces of the constructed tetrahedron models are all planes connected by corner points, which are equivalent planes and cannot present the true surface state. For example, there may be some concave and convex parts on the surface, and this also needs to be corrected and compensated to finally obtain the most accurate volume value.
[0043] Specifically, clean the liquid cargo tank before scanning to ensure the stability of the scanning environment and avoid the influence of environmental interference and instrument errors on the collected point cloud data. Use a three-dimensional laser scanner to perform a full-range scan of the interior of the liquid cargo tank. During the scanning process, noise points will be generated due to factors such as the boundary of the scanned cabin and the scanning environment. The noise points will affect the accuracy of the original scanning data during the subsequent data analysis process, resulting in unclear scanned point cloud data, and even obscuring the graphic features, increasing the analysis difficulty. In order to improve the quality of the scanning data and facilitate subsequent higher-level processing, the scanning data must be used after removing the noise points. To improve the accuracy data, manual pre-stitching needs to be performed on each station of the scanning data in advance to establish the association between each station. After the point cloud is stitched, an overall cabin point cloud set is formed, and the accuracy deviation range of the overall scanned point cloud needs to be controlled within 3mm.
[0044] Step S2: As Figure 4As shown in the figure, the 16 corner points of the rhombic liquid tank are cut and divided. For the 8 corner points on the end face, one corner point is selected as the common point, and 5 first dividing lines are formed by connecting this common point with the other 5 non - adjacent corner points, thereby dividing the end face into 6 triangles. The connection line of the common points on the bow face and the stern face is parallel to the bow - stern direction; each of the eight side faces has 4 corner points, and 1 second dividing line is formed by connecting the respective diagonals of the eight side faces, thereby dividing each side face into 2 triangles. Finally, the bulkhead of the rhombic liquid tank is divided into 28 triangular faces, becoming an icosahedron.
[0045] It should be noted that each of these triangular faces is an equivalent plane formed by connecting three corner points. Since there may be some concave and convex regions on the actual surface, the initial approximate result is obtained by calculating through the equivalent plane first, and then the volume difference between the equivalent plane and the actual surface is calculated through the grid of each wall surface for correction.
[0046] Step S3: Divide the icosahedron of the rhombic liquid tank into 6 triangular prisms. Specifically, the first dividing line extends along the bow - stern direction to form a first dividing surface, and the 5 first dividing surfaces divide the rhombic liquid tank into 6 triangular prisms; the adjacent triangular prisms have a rectangular interface, and 1 third dividing line is formed by connecting the diagonals of the interface. A single triangular prism is divided into an octahedron by the second cutting line and the third cutting line.
[0047] For a single triangular prism, there are a total of three dividing lines, including at least 1 second dividing line and at least 1 third dividing line. The three dividing lines form two intersection points at the corner points of the triangular prism, and the 3 dividing lines form 2 second dividing surfaces. The triangular prism is divided into 3 tetrahedrons along the second dividing surfaces.
[0048] The corner points of the tetrahedron after division are still the corner points of the original rhombic liquid tank. Calculate the volume of each tetrahedron according to the coordinates of the corner points of the tetrahedron and sum them up to obtain the volume Va of the icosahedron. Here, the vector method is used for calculation.
[0049] The following specifically illustrates step S2 by way of example. For example, Figure 4 the rhombic liquid tank shown in the figure includes 16 corner points (a, b, c, d, e, f, g, h, p, q, r, s, t, u, v, w), and 10 faces (face A, face B, face C, face D, face E, face F, face G, face H, face J, face K. Face D is the bow face, face B is the stern face, face D and face B are octagonal faces, and the other faces are rectangular faces). Its surface is divided into 28 triangular faces to form an icosahedron, as shown in Figure 4 where the bow face and the stern face each have 8 corner points, and each 8 corner points form 6 triangular faces, and the other faces each have 4 corner points, and each 4 corner points form 2 triangular faces.
[0050] The twenty-eight faces are as follows: Face A: abp, bpq; Face B: wvu, wup, put, ptq, qts, qsr; Face C: fet, fut; Face D: hgf, hfa, afe, aeb, bed, bdc; Face E: ahw, awp; Face F: ghw, gwv; Face G: gfu, guv; Face H: bcq, cqr; Face J: cdr, drs; Face K: des, est. Among them, fw, fp, ep, eq, dq are the third cutting lines of the internal interface, thus determining that the 10 internal triangular faces are: hfw, fuw, afp, fpu, aep, ept, beq, eqt, bdq, dqs. Finally, 6 triangular prisms, namely 6 octahedrons, are generated, which are octahedrons hgfwvu, hfawup, afeput, aebptq, bedqts, bdcqsr respectively.
[0051] Next, calculate the volumes of the 6 octahedrons respectively, and then add them up to calculate the volume of the liquid cargo tank after cutting and modeling. See Figure 5 , now take the octahedron ABCDEF as an example (the points A, B, C, D, E, F are only for the example calculation method, and the octahedron structure in step 2 is calculated using this method).
[0052] Let its volume be V6(ABCDEF), (where "V" represents volume and "6" means the 6 corner points are A, B, C, D, E, F respectively). V6 takes point B as the vertex and is cut into 3 tetrahedrons V4(BDEF), V4(ABCD), V4(BCDF) by BD, BF, CD.
[0053] Now calculate the volume of a tetrahedron. Suppose the four vertex coordinates of the tetrahedron are P(x1,y1,z1), Q(x2,y2,z2), R(x3,y3,z3), S(x4,y4,z4).
[0054] First, calculate the vector The value of is:
[0055] Then calculate the volume of the tetrahedron where "×" represents vector cross product, "·" represents vector dot product, and "|···|" represents taking the absolute value.
[0056] Calculate the cross product and dot product of the vectors, and finally substitute them into the above formula to find that the volume of the tetrahedron is:
[0057]
[0058] Now, calculate using the volume formula of a tetrahedron V4(PQRS): V6(ABCDEF) = V4(BDEF) + V4(ABCD) + V4(BCDF), where the parameters ABCDEF have an order requirement, which is related to the cutting method of each octahedron. The cutting lines of V6(ABCDEF) are BD, BF, and CD. The cutting lines of V6(hgfwvu) are gw, gu, and fw. The cutting lines of V6(hfawup) are fw, fp, and aw. The cutting lines of V6(afeput) are fp, ft, and ep. The cutting lines of V6(aebptq) are ep, eq, and bp. The cutting lines of V6(bedqts) are eq, es, and dq. The cutting lines of V6(bdcqsr) are dq, dr, and cq. Among them, fw, fp, ep, eq, and dq are the common intersection lines of the 6 octahedrons. Therefore, the above 6 octahedrons exactly form the 28-faced polyhedron of the liquid cargo tank, and then it can be calculated
[0059] V 16 (abcdefghpqrstuvw) = V6(hgfwvu) + V6(hfawup) + V6(afeput) + V6(aebptq) + V6(bedqts)
[0060] + V6(bdcqsr). V 16 (abcdefghpqrstuvw) is the volume Va after the liquid cargo tank is cut and modeled.
[0061] Next, perform step S4: Set the reference plane as the X-Y plane, and draw auxiliary lines along the Z direction perpendicular to the reference plane. The auxiliary lines pass through the 4 real corner points of each wall grid. The auxiliary lines intersect with the equivalent plane formed during the division of the rhombic liquid tank to form 4 mapping points. The 4 mapping points enclose a mapping surface. The volume of the polyhedron formed by the wall grid, its corresponding mapping surface, and the 4 auxiliary lines is the correction volume V C (where "C" means the volume difference). Set the offset plane. The wall grid and the mapping surface are located between the reference plane and the offset plane. The offset plane is parallel to the reference plane and is 1000 mm apart. By setting offset points at positions 1000 mm away from the reference plane on the auxiliary lines, multiple offset points are connected to enclose the offset plane. The volume of the polyhedron formed by the wall grid, its corresponding offset plane, and the 4 auxiliary lines is V2. The volume of the polyhedron formed by the mapping surface, its corresponding offset plane, and the 4 auxiliary lines is V3, |V C | = |V2 - V3|. If the mapping points are closer to the center of the rhombic liquid tank than the real corner points, it means that the actual volume of the liquid tank is larger than the modeled 28-faced polyhedron, and V C is a positive value; otherwise, V C is a negative value, and the final actual volume is Va + V C .
[0062] For example, as Figure 6 shown, the C surface includes two equivalent planar fets, futs. The red solid square in the figure is the mapped surface corresponding to a wall grid. The wall grid, mapped surface, reference plane, and offset plane are drawn in the same three-dimensional figure, as Figure 7 shown. K1L1M1N1 is the reference plane, K2L2M2N2 is the actual wall grid, K3L3M3N3 is the mapped surface, and K4L4M4N4 is the offset plane. The volume of the figure formed by the actual wall grid and the offset plane is denoted as V2, and the volume of the figure formed by the mapped surface and the offset plane is denoted as V3.
[0063] The four true corner points of the wall grid are obtained by measurement in step S1 and are known quantities; while the X and Y values of the coordinates of the mapped points are the same as those of the true corner points, and the Z value needs to be solved. The equivalent plane is the plane formed by connecting three corner points of the rhombic liquid tank. The plane equation can be obtained according to the coordinates of the three corner points, and then according to the plane equation of the equivalent plane, substituting the X and Y values of the mapped points, the Z value can be finally obtained.
[0064] Specifically, since there are 28 equivalent planes in total, it is necessary to first determine which equivalent plane the mapped point is located in. It can be determined whether the mapped point is within the range according to the boundary coordinate values of the equivalent plane; it can also be determined using the area method, as shown in Figure 8 , to determine whether a point P is within the plane of a triangle ABC, calculate the area S△ of the triangle ABC, and the areas S1, S2, and S3 of the 3 small triangles formed by the point P and the three vertices of the triangle respectively. If S△ = S1 + S2 + S3, it means that the point P is inside the triangle ABC, otherwise, it is outside. Calculate the area of the triangle using the vector method. Let the coordinates of the three points be A(x1, y1), B(x2, y2), and C(x3, y3). First, find the vector vector Then, calculate the cross product of the vector and the vector and the modulus of the cross product Calculation of the cross product: Area of the triangle S1 = S(PAB), S2 = S(PBC), S3 = S(PAC), S △ = S(ABC). If S △ = S1 + S2 + S3, then the point P is within the range of the plane ABC. If not, calculate the relationship between the point P and other planes.
[0065] If the point P is within the range of the plane ABC, the Z value of the P point can be calculated. Let the coordinates of the three points be A(x1, y1, z1), B(x2, y2, z2), and C(x3, y3, z3). First, find the vector: Then calculate the vector and cross product That is, the normal vector. Let Then:
[0066] a = (y2 - y1) * (z3 - z1) - (y3 - y1) * (z2 - z1),
[0067] b = (z2 - z1) * (x3 - x1) - (z3 - z1) * (x2 - x1),
[0068] c = (x2 - x1) * (y3 - y1) - (x3 - x1) * (y2 - y1).
[0069] Given a point A(x1, y1, z1) on a plane and the normal vector Then the plane equation is
[0070] a(x - x1) + b(y - y1) + c(z - z1) = 0, and after arrangement, the general equation of the plane can be obtained: ax + by + cz + d = 0, where d =
[0071] -(ax1 + by1 + cz1). Substitute the x and y values of point P, then the z value of point P is z = -(a * x + b * y + d) / c. Obtain the Z values of each mapped point according to the above process.
[0072] For the volume calculation of V2, since the corresponding wall grid K2L2M2N2 is not a plane, the wall grid is approximated and fitted into multiple sub - planes, and finally a volume value approaching the true value is obtained.
[0073] As Figure 9 shown, establish two diagonals L2N2 and K2M2. The diagonal L2N2 extends along the Z - direction to form the first cutting plane, and the first cutting plane divides the polyhedron represented by V2 into two triangular prisms V21 and V22 along the Z - direction; the diagonal K2M2 extends along the Z - direction to form the second cutting plane, and the second cutting plane divides the polyhedron represented by V2 into two triangular prisms V23 and V24. Then V2 = (V21 + V22 + V23 + V24) / 2. That is, the wall grid is approximated and fitted into different combinations of planes by the approximation method, and then the average value of different combinations is calculated as the volume value approaching the true value.
[0074] Connect the mid - points P and Q of the diagonals L2N2 and K2M2 to obtain the line segment PQ, and the mid - point O of PQ is used as the fitting center of the wall grid K2L2M2N2. It should be understood that in this step, the smaller the grid size, the closer the volume value obtained by the approximation method is to the true value. The grid size is not limited to 1m, and can also be values such as 0.5m and 0.8m.
[0075] For the volume calculation of V3, since its mapping surface K3L3M3N3 is a plane itself, there is no need to resort to the approximation method. It can be directly divided into two triangular prisms for solution. For the volume calculation of the triangular prism in this step, the same solution idea in step S3 above can be used, which will not be elaborated here.
[0076] In summary, the present invention provides a method for measuring and calculating the volume of a rhombic liquid tank. This volume measurement and calculation method uses a three-dimensional laser scanner to perform an all-round scan of the interior of the rhombic liquid tank, obtaining a large amount of point cloud data. Points are taken for each surface through grid division, and the three-dimensional coordinate data of 16 corner points are extracted. Due to construction deviations, the actual rhombic liquid tank is not a standard decahedron, and each corner point is not strictly in the same plane according to the design drawings. Therefore, the entire rhombic liquid tank is divided into multiple tetrahedrons to make it closer to the actual liquid tank condition. For a single tetrahedron obtained by division, there is still a certain deviation from the actual liquid tank. Since the construction of the tetrahedron model is based on four corner points, the surfaces of the constructed tetrahedron model are all equivalent planes connected by corner points and cannot present the concave and convex state of the actual surface. Therefore, the volume difference between the equivalent plane and the actual surface is calculated through the grid of each wall surface for correction. Through the volume division and grid correction of the present invention, errors can be eliminated as much as possible, the measurement accuracy can be improved, and finally a volume value approaching the actual liquid tank can be obtained.
[0077] The above embodiments are only illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.
Claims
1. A method for measuring and calculating the volume of a rhombus tank, characterized in that: The steps include: S1: Use a 3D laser scanner to perform an all-round scan of the interior of the diamond-shaped liquid tank to obtain point cloud data, extract the 3D coordinate data of the 16 corner points of the diamond-shaped liquid tank, and perform grid point selection on each surface of the diamond-shaped liquid tank to obtain the wall grid and the real corner point coordinates of each wall grid; the diamond-shaped liquid tank is a horizontal octagonal prism, including two end faces and eight side faces, the two end faces are the bow face and the stern face and are both octagonal, and the eight side faces are rectangular faces; S2: Cut and divide the 16 corner points of the rhombus tank. For the 8 corner points of the end face, select one corner point as the common point. Connect the common point with the other 5 non-adjacent corner points to form 5 first dividing lines, so that the end face is divided into 6 triangles. The line connecting the common points of the bow and stern is parallel to the bow and stern directions. Each of the eight side faces has 4 corner points. Connect the eight side faces along their respective diagonals to form a second dividing line, so that each side face is divided into 2 triangles. Finally, the bulkhead of the rhombus tank is divided into 28 triangular faces, which become a 28-sided polygon. Each triangular face is an equivalent plane formed by connecting three corner points. S3: Divide the icosahedron of the rhombus tank into six triangular prisms, and divide a single triangular prism into three tetrahedrons. Calculate the volume of each tetrahedron according to the coordinates of the tetrahedron corner points and sum them up to obtain the volume of the icosahedron as Va.
2. The method for measuring and calculating the volume of a diamond tank according to claim 1, characterized in that: Step S3 specifically includes: The first dividing line extends along the bow and stern direction to form a first dividing plane, and the five first dividing planes divide the rhombus tank into six triangular prisms; adjacent triangular prisms have a rectangular interface, and a third dividing line is formed along the diagonal line of the interface, and a single triangular prism is divided into an octahedron by the second cutting line and the third cutting line; For a single triangular prism, there are three dividing lines, including at least one second dividing line and at least one third dividing line. The three dividing lines form two intersection points at the corner points of the triangular prism. The three dividing lines form two second dividing planes. The second dividing plane divides the triangular prism into three tetrahedrons; the corner points of the divided tetrahedrons are the corner points of the original rhombus liquid tank, and the volume of each tetrahedron is calculated by the vector method according to the coordinates of the tetrahedron corner points.
3. The method for measuring and calculating the volume of a diamond tank according to claim 1, characterized in that: The size of a single wall grid is 1m*1m.
4. The method for measuring and calculating the volume of a diamond tank according to claim 1, characterized in that: Also includes: S4: Set the reference plane as the XY plane, and draw auxiliary lines along the Z direction perpendicular to the reference plane. The auxiliary lines pass through the four real corner points of each wall grid. The auxiliary lines intersect with the equivalent plane formed when the rhombus tank is divided to form four mapping points. The four mapping points form a mapping surface. The volume of the polyhedron surrounded by the wall grid, its corresponding mapping surface, and the four auxiliary lines is the correction value V. C ; If the mapping point is closer to the center of the rhombus tank than the real corner point, it means that the real tank volume is larger than the modeled 28-hedron, V C is positive; otherwise, V C is a negative value, and the final volume of the diamond tank is Va+V C .
5. The method for measuring and calculating the volume of a diamond tank according to claim 4, characterized in that: In step S4, V C The solution process includes: Determine the offset surface. The wall mesh and the mapping surface are located between the reference surface and the offset surface. The offset surface is parallel to the reference surface and is at a preset distance. The volume of the polyhedron enclosed by the wall mesh, its corresponding offset surface, and the four auxiliary lines is V2. The volume of the polyhedron enclosed by the mapping surface, its corresponding offset surface, and the four auxiliary lines is V3. C |=|V2-V3|.
6. The method for measuring and calculating the volume of a diamond tank according to claim 5, characterized in that: The preset distance is 1000mm.
7. The method for measuring and calculating the volume of a diamond tank according to claim 5, characterized in that: The four real corner points of the wall grid are measured and obtained in step S1 and are known quantities. The coordinate X and Y values of the mapping point are the same as the coordinate X and Y values of the real corner points, and the Z value needs to be solved. The solution process is: the equivalent plane is the plane formed by connecting the three corner points of the rhombus liquid tank. First, determine which equivalent plane the mapping point is located in, and then obtain the plane equation of the equivalent plane based on the coordinates of the three corner points. Then, according to the plane equation of the equivalent plane, substitute the X and Y values of the mapping point to finally obtain the Z value.
8. The method for measuring and calculating the volume of a diamond tank according to claim 6, characterized in that: For the volume calculation of V2, the four corner points of the wall grid are set to K2L2M2N2. Since the wall grid is not a plane, the wall grid is fitted into multiple sub-planes through the approximation method, and finally a volume value close to the true value is obtained; specifically, it includes: Two diagonal lines L2N2 and K2M2 are established. The diagonal line L2N2 extends along the Z direction to form a first cross-sectional plane, which divides the polyhedron represented by V2 into two triangular prisms V21 and V22 along the Z direction. The diagonal line K2M2 extends along the Z direction to form a second cross-sectional plane, which divides the polyhedron represented by V2 into two triangular prisms V23 and V24 along the Z direction. Then V2 = (V21 + V22 + V23 + V24) / 2.
9. The method for measuring and calculating the volume of a diamond tank according to claim 8, characterized in that: The values of V21, V22, V23, V24, and V3 are obtained by decomposing the triangular prism into tetrahedrons in step S3.
10. The method for measuring and calculating the volume of a diamond tank according to claim 8, characterized in that: Methods for determining in which equivalent plane a mapping point lies include the area method; Set the mapping point as P and the three corner points of the equivalent plane as ABC, calculate the area S△ of triangle ABC, and the areas S1, S2, and S3 of the three small triangles formed by point P and the three vertices of the triangle. If S△=S1+S2+S3, it means that the point P is inside the triangle ABC, otherwise, it is outside.