A method and device for positioning parts of a ship cutting platform

Abstract

The present invention discloses a method and device for part positioning of a ship cutting platform, which relates to the technical field of ship equipment manufacturing. The method is characterized in that the method comprises the following steps: Step 1, install a part positioning device for the ship cutting platform, scan an image with a vision system, and match a positioning block in the image; Step 2, calculate gradients and perform edge detection to obtain two edges; Step 3, calculate the origin of the positioning coordinate system; Step 4, fit the plane of the positioning block; Step 5, calculate the homogeneous matrix of the positioning coordinate system; Step 6, position the part according to the application scenario; Step 7, record the conversion relationship between the positioning coordinate system and the spatial coordinate system; Step 8, calculate the spatial positioning result. The present invention can realize the spatial positioning of the target part under the conditions of insufficient mechanism movement accuracy and difficult calibration of the ship cutting platform, reduce the equipment cost. In addition, the part positioning device has strong flexibility, obvious features and is easy to deploy and transplant.

Description

Technical Field

[0001] The present invention relates to the technical field of ship equipment manufacturing, and particularly to a part positioning method and device for a ship cutting platform. Background Art

[0002] Hull plate cutting parts are an important part of the hull structure. During the production process, steel plates are cut on a cutting platform dozens of meters long by a cutting machine to generate plate parts. After cutting, the parts need to be sorted into different flows. Currently, the material handling operations of mainstream shipbuilding enterprises still rely entirely on manual labor, and there is an urgent need to develop intelligent material handling equipment. When applying intelligent material handling equipment on a ship cutting platform, it is first necessary to complete part positioning, and then perform material handling operations on the parts at the target positions. To achieve part positioning on the cutting platform, it is necessary to convert the positioning results of the parts in the visual coordinate system to the spatial coordinate system.

[0003] Currently, the conversion methods between the visual coordinate system and the spatial coordinate system mainly include nine-point calibration and hand-eye calibration. For hand-eye calibration, first, the positioning results of the parts in the visual coordinate system need to be converted to the tool coordinate system through the hand-eye matrix, and then converted to the spatial coordinate system through the transformation matrix between the tool coordinate system and the spatial coordinate system to complete part positioning in space.

[0004] However, these conversion algorithms depend on the motion accuracy of the equipment and require a calibration board that matches the size of the working space. When the scene reaches the ten-meter level, applying equipment with high repeat accuracy and positioning accuracy will result in too high costs, and it is also difficult to find a calibration board for such a large scene. Therefore, due to space cost and cost factors, the above algorithms are difficult to be implemented in large scenes.

[0005] Therefore, the technical personnel in this field are committed to developing a part positioning device and method for a ship cutting platform that can complete part positioning in a large scene, effectively solving the problem of inaccurate visual positioning of parts under the condition of insufficient motion accuracy of large equipment on the ship cutting platform. Summary of the Invention

[0006] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is the problem of inaccurate visual positioning of parts under the condition of insufficient motion accuracy of large equipment on the ship cutting platform.

[0007] To achieve the above object, the present invention provides a part positioning method for a ship cutting platform, characterized in that the method includes the following steps:

[0008] Step 1: Install the part positioning device for the ship cutting platform. The part positioning device for the ship cutting platform includes a mounting plate, a connecting bracket, and a positioning block. The positioning block has corner points, vertical edges, and a planar area. Use a vision system to scan the scene to obtain an image, and match the coordinates of the positioning block in the vision coordinate system in the image. Both the positioning block and the target part are within the image.

[0009] Step 2: Perform image gradient detection in the area where the position of the positioning block is greater than the motion error range of the vision system to obtain a gradient image. Apply line detection to the detected edge points to obtain the starting and ending points of two vertical edges.

[0010] Step 3: Calculate the intersection point of the two vertical edges in the vision coordinate system.

[0011] Step 4: Extract the height point cloud in the planar area and use plane fitting to obtain the parametric equation of the planar area.

[0012] Step 5: Substitute the intersection point into the parametric equation of the planar area, calculate the origin of the positioning coordinate system, and establish the conversion relationship from the positioning coordinate system to the vision coordinate system.

[0013] Step 6: Use the vision method to position the target part.

[0014] Step 7: Record the conversion relationship between the positioning coordinate system and the spatial coordinate system.

[0015] Step 8: Calculate and convert the vision positioning result of the target part to the positioning coordinate system, and then convert it to the spatial coordinate system to obtain the spatial positioning result.

[0016] Further, Step 1 further includes leveling the positioning block.

[0017] Further, in Step 1, the vision system is a three-dimensional vision sorting equipment equipped with a vision mechanism.

[0018] Further, in Step 2, the image gradient detection uses the Laplace gradient detection algorithm.

[0019] Further, in Step 4, the parametric equation of the planar area uses the least squares solution of the homogeneous equation.

[0020] Further, the positioning coordinate system takes the corner point of the positioning block as the origin, the edge of the positioning block as the X-axis, and the planar area of the positioning block as the 0 plane.

[0021] The present invention also provides a part positioning device for a ship cutting platform, which is characterized by comprising a mounting plate, a connecting bracket and a positioning block. Among them, the mounting plate is installed on the ground, the connecting bracket is connected to the mounting plate, the positioning block is connected to the connecting bracket, and the positioning block has a corner point, a vertical edge and a planar area.

[0022] Further, the mounting plate is installed on the ground by expansion screws, the connecting bracket is installed on the mounting plate by positioning bolts, and the positioning block is installed on the connecting bracket by leveling bolts.

[0023] Further, the corner point is used to establish the origin of the positioning coordinate system, the vertical edge is used to establish the coordinate axes of the positioning coordinate system, and the planar area is used to establish the 0 plane of the positioning coordinate system.

[0024] Further, the connection between the connecting bracket and the mounting plate is detachable.

[0025] In a preferred embodiment of the present invention, the present invention provides a part positioning method for a ship cutting platform. The method includes:

[0026] Step 1: Install a part positioning device for a ship cutting platform, scan the scene with a vision system to obtain an image. Both the positioning block and the target part are within this image. Apply template matching within the allowable range of image error to obtain the coordinates of the positioning block in the vision coordinate system.

[0027] Step 2: Perform image gradient detection within an area near the position of the positioning block that is larger than the motion error range of the vision system to obtain a gradient image. As shown in Formula 1-1 which is the Laplace gradient formula, apply line detection to the detected edge points to obtain the starting and ending points of two vertical edges, denoted as the X-axis vector as vector V1.

[0028]

[0029] Step 3: Obtain the intersection point of the two edges in the vision coordinate system, denoted as P(x, y).

[0030] Step 4: Extract point clouds from the planar area of the positioning block, and use plane fitting to obtain the parametric equation of this plane, such as αβγδ in Formula 1-2. To avoid the situation where this plane passes through the origin, the least squares solution of the homogeneous equation is adopted here. If the point set matrix is defined as A, then the least squares solution of Formula 1-3 is A T The eigenvector corresponding to the minimum eigenvalue of A. Here, take the eigenvector with δ greater than 0;

[0031]

[0032] AX = 0 (1-3)

[0033] Step 5: Substitute P into Formula 1-3 to obtain O(x, y, z) as the origin of the positioning coordinate system. Normalize V1 to get V11 as the X-axis vector of the positioning coordinate system. Normalize the vector (α, β, γ) to get the vector V13, and calculate the cross product of the vector V13 and the vector V11 to obtain the vector V12. The conversion relationship H1 from the positioning coordinate system to the vision coordinate system is shown in Formula 1-4. Thus, the establishment of the positioning coordinate system is completed.

[0034]

[0035] Step 6: Apply the vision method to position the target part. Let the results of the position positioning feature points of the target part be T1(tx1, ty1, tz1) and T2(tx2, ty2, tz2).

[0036] Step 7: Record that when the positioning block is installed, the conversion relationship between the positioning coordinate system with the corner point of the positioning block as the origin, the edge of the positioning block as the X-axis, and the 0 plane as the plane area of the positioning block and the space coordinate system is H2.

[0037] Step 8: In the process of part positioning, the vision positioning result is calculated to the positioning coordinate system and then converted to the space coordinate system. As shown in Formula 2-1, the calculated point T12 is the coordinate of the target point in the space coordinate system. Similarly, the point T22 can be obtained. Then the length measurement can be defined as the distance between T22 and T12, and the angle measurement can be defined as the angle between the vector (T22 - T12) and the X-axis.

[0038]

[0039] In the process of positioning the target part by applying the positioning method provided by the present invention, the part positioning result is converted to the positioning coordinate system and then to the space coordinate system. According to the above positioning process, the positioning transfer error of the target part only depends on the installation error of the positioning block and the feature recognition error of the positioning block. Therefore, it can be considered that the positioning accuracy when the mechanism takes pictures and the repetition accuracy when the mechanism operates repeatedly have no influence on this positioning scheme. The beneficial effect of the present invention is that it can realize the spatial positioning of the target part under the conditions of insufficient movement accuracy of the mechanism and difficult calibration of the ship cutting platform, reduce the equipment cost. In addition, the part positioning device has strong flexibility, obvious features and is easy to deploy and transplant.

[0040] The following will further illustrate the concept, specific structure and technical effects generated by the present invention with reference to the drawings, so as to fully understand the purpose, features and effects of the present invention. Description of the Drawings

[0041] Figure 1 is a flowchart of a part positioning method for a ship cutting platform according to a preferred embodiment of the present invention;

[0042] Figure 2 It is a schematic diagram of the working platform part positioning scenario of a part positioning method for a ship cutting platform according to a preferred embodiment of the present invention;

[0043] Figure 3 It is a picture of the working platform collected by the vision system of a part positioning device for a ship cutting platform according to a preferred embodiment of the present invention;

[0044] Figure 4 It is a schematic structural diagram of a part positioning device for a ship cutting platform according to a preferred embodiment of the present invention;

[0045] Wherein, 1 - positioning block, 2 - connecting bracket, 3 - mounting plate, 4 - target part, 5 - working platform, 6 - vision mechanism, 7 - three-dimensional vision sorting equipment carrying the vision mechanism. Detailed implementation manners

[0046] The following introduces multiple preferred embodiments of the present invention with reference to the accompanying drawings of the specification to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the protection scope of the present invention is not limited to the embodiments mentioned in the text.

[0047] In the drawings, components with the same structure are denoted by the same numerical labels, and components with similar structures or functions everywhere are denoted by similar numerical labels. The size and thickness of each component shown in the drawings are arbitrarily shown, and the present invention does not limit the size and thickness of each component. In order to make the illustration clearer, the thickness of some parts in the drawings is appropriately exaggerated.

[0048] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present application.

[0049] As Figure 4 shown, the present invention provides a part positioning device for a ship cutting platform, and the device includes: a mounting plate 3 for ensuring that the position of the positioning device remains unchanged after being disassembled and reassembled, and having little impact on the working environment; a connecting bracket 2 for ensuring a certain height between the positioning block and the ground; a positioning block 1 for extracting the edge and plane by a vision algorithm and calculating a transformation matrix. The mounting plate 3 is fixedly installed on the ground by expansion bolts, the connecting bracket 2 is installed on the mounting plate 3 by positioning bolts, and the positioning block 1 is installed on the connecting bracket 2 by leveling bolts.

[0050] A part positioning device is arranged within the visual field of the vision system of the present invention. The part positioning device is composed of a mounting plate 3, a connecting bracket 2, and a positioning block 1. The part positioning device is detachable and can be installed back to its original position after disassembly. The positioning block 1 has a corner point for establishing the origin of the positioning coordinate system, two perpendicular edges for establishing the coordinate axes of the positioning coordinate system, and a plane for establishing the 0-plane of the positioning coordinate system. After the positioning block 1 is installed, it has a fixed transformation relationship with the space coordinate system.

[0051] As Figure 2 shown, the three-dimensional vision sorting equipment 7 equipped with a vision mechanism can complete the sorting of parts within its working range and can perform three-dimensional vision shooting on the area of the working platform 5. In this embodiment, the vision mechanism 6 of the sorting equipment can simultaneously scan the target part 4 and the positioning block 1.

[0052] When installing the positioning device for the first time, first fix the mounting plate 3 on the ground. Then, it is necessary to level the surface of the positioning block 1 and ensure that the X-edge of the positioning block 1 is parallel to the track. Based on this installation, record the homogeneous transformation matrix H2 between the positioning block 1 and the space coordinate system. During normal operation, the positioning device is installed on one side of the working platform 5. When there is an operation on the working platform 5 that may cause displacement of the positioning device, the positioning block 1 can be disassembled together with the connecting bracket 2.

[0053] The large-scene positioning solution in this embodiment is as Figure 1 shown:

[0054] Step 1: As shown in the image obtained by the three-dimensional vision sorting equipment equipped with a vision mechanism scanning the scene, match the positioning block within the area larger than the gantry motion error range near the positioning block in Figure 3 to ensure the positioning speed of the large scene; Figure 3

[0055] Step 2: Perform image gradient detection within the area larger than the motion error range of the vision system near the positioning block to obtain a gradient image. As shown in Equation 3-1, it is the Laplacian gradient detection algorithm, where src is the original image and Gx is the gradient map. Apply line detection to the edge points detected by Gx to obtain the starting and ending points of two perpendicular edges. For example, record the X-axis vector V1(0.005, 0.1790, 0.0006).

[0056]

[0057] Step 3: Calculate the intersection point of the two edges in the vision coordinate system, recorded as P(-3.076, 2.8299);

[0058] Step 4: As Figure 4As shown in the figure, height point clouds are extracted from the planar region of the positioning block, and the parametric equation of this plane is obtained by plane fitting as αβγδ in Formula 3-2. To avoid the situation where this plane passes through the origin, the least squares solution of the homogeneous equation is adopted here. If the point set matrix is defined as A, the least squares solution of Formula 3-3 is A T The eigenvector corresponding to the minimum eigenvalue of A, here the eigenvector with δ greater than 0 is taken; for example, finally α = -0.003567, β = -0.003160, γ = -0.9999, δ = 0.453186.

[0059]

[0060] AX = 0 (3-3)

[0061] Step 5: Substitute P into Formula 3-3 to obtain O(-3.076, 2.8299, -0.451163) as the origin of the positioning coordinate system. Normalize V1 to obtain V11(-0.003068, -0.9999, -0.003573) as the X-axis vector of the positioning coordinate system. Normalize the vector (α, β, γ) to obtain the vector V13(0.003573, 0.00316, 0.9999). Calculate the cross product of the vector V13 and the vector V11 to obtain the vector V12(0.003079, -0.9999, 0.003149). The homogeneous transformation matrix from the positioning coordinate system to the vision coordinate system is as shown in Formula 3-4.

[0062]

[0063] Step 6: Locate the target part. Let the positioning results of the target part positions be T1(-2.856, 5.036, -0.50968) and T2(-2.8901, 10.6417, -0.4976).

[0064] Step 7: When installing the positioning block, with the corner point of the positioning block as the origin, the vertical edge of the positioning block as the X-axis, the coordinates of the corner point of the positioning block in space are (13.073, 4.136, 0), and the conversion relationship between the positioning coordinate system with the planar region of the positioning block as the 0 plane and the space coordinate system is H2, as shown in Formula 4-1.

[0065]

[0066] Step 8: The visual positioning of the part is first transformed into the positioning coordinate system, and then the positioning result in the space coordinate system is calculated according to the transformation relationship between the positioning coordinate system and the space coordinate system. The part positioning result is shown in Formula 4-2, and the obtained point T12 is the coordinate of the target point in the space coordinate system. Similarly, T22 is obtained. Then the length measurement result is shown in Formula 4-3, where L is the measurement result, and the angle measurement result is shown in Formula 4-4. Here, V21 is the vector in the X direction of the space coordinate system, which is parallel to V11 in this example.

[0067]

[0068] L = ‖T22 - T11‖2 = 5.606 (4-3)

[0069]

[0070] A part positioning scheme and device for a ship cutting platform according to the present invention, aiming at the problems of insufficient positioning accuracy of large-range motion mechanisms and difficulty in large-scene calibration, fully considering the positioning requirements, realizes the spatial coordinates of the target part through coordinate transfer, and can avoid the situation of positioning errors caused by insufficient accuracy of the shooting position and insufficient accuracy of repeated shooting work. In the present invention, first, an image of the cutting platform is obtained by taking a photo; the template matching method is applied to locate the positioning block in the image; the straight line detection is applied to obtain two edge information on the positioning block and calculate the origin; the regional plane fitting is applied to obtain the space plane on the positioning block; the coordinate system is established according to the edge vector and the coordinate origin to generate a homogeneous transformation matrix; after obtaining the part positioning information, it is transformed into the positioning coordinate system through the homogeneous transformation matrix, and then into the space coordinate system, and finally the position, angle, length and other information of the target part are obtained. The present invention also provides a positioning device using the above positioning method. The device has little impact on the environment, obvious self-characteristics, and can be disassembled under harsh conditions. Applying the positioning method provided by the present invention can achieve spatial positioning of the target part on the cutting platform in the case of insufficient mechanism positioning accuracy and repeated accuracy.

[0071] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations according to the concept of the present invention without creative labor. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art should be within the protection scope determined by the claims.

Claims

1. A method for positioning parts of a ship cutting platform, characterized in that, The method includes the following steps: Step 1: Install a part positioning device for a ship cutting platform. The part positioning device for the ship cutting platform includes a mounting plate, a connecting bracket, and a positioning block. The positioning block has corner points, vertical edges, and a planar area. Scan the scene with a vision system to obtain an image, and match the coordinates of the positioning block in the vision coordinate system in the image. Both the positioning block and the target part are within the image; Step 2: Perform image gradient detection in the area where the position of the positioning block is greater than the motion error range of the vision system to obtain a gradient image. Apply line detection to the detected edge points to obtain the starting and ending points of two vertical edges; Step 3: Obtain the intersection point of the two vertical edges in the vision coordinate system; Step 4: Extract the height point cloud in the planar area and use plane fitting to obtain the parametric equation of the planar area; Step 5: Substitute the intersection point into the parametric equation of the planar area, calculate the origin of the positioning coordinate system, and establish the conversion relationship between the positioning coordinate system and the vision coordinate system. The positioning coordinate system takes the corner point of the positioning block as the origin, the edge of the positioning block as the X-axis, and the planar area of the positioning block as the 0 plane. The points from the positioning coordinate system to the vision coordinate system are converted through a homogeneous transformation matrix; Step 6: Use a vision method to position the target part; Step 7: Record the conversion relationship between the positioning coordinate system and the spatial coordinate system; Step 8: Calculate and convert the visual positioning result of the target part to the positioning coordinate system, and then convert it to the spatial coordinate system to obtain the spatial positioning result.

2. The method for positioning parts of a ship cutting platform according to claim 1, characterized in that, Step 1 further includes leveling the positioning block.

3. A part positioning method for a ship cutting platform according to claim 1, characterized in that, In Step 1, the vision system is a three-dimensional vision sorting equipment equipped with a vision mechanism.

4. A method for positioning parts of a ship cutting platform according to claim 1, characterized in that, In Step 2, the image gradient detection uses the Laplace gradient detection algorithm.

5. A method for positioning parts of a ship cutting platform according to claim 1, characterized in that, In Step 4, the parametric equation of the planar area uses the least squares solution of the homogeneous equation.

6. A part positioning device for a ship cutting platform, the part positioning device being used to implement a part positioning method for a ship cutting platform as described in claim 1, characterized in that, It includes a mounting plate, a connecting bracket, and a positioning block. Among them, the mounting plate is installed on the ground, the connecting bracket is connected to the mounting plate, the positioning block is connected to the connecting bracket. The positioning block has corner points, vertical edges, and a planar area. The corner points are used to establish the origin of the positioning coordinate system, the vertical edges are used to establish the coordinate axes of the positioning coordinate system, the planar area is used to establish the 0 plane of the positioning coordinate system, and the X-axis edge of the positioning block is parallel to the track of the working platform.

7. The part positioning device for a ship cutting platform according to claim 6, characterized in that, The mounting plate is installed on the ground through expansion bolts, the connecting bracket is installed on the mounting plate through positioning bolts, and the positioning block is installed on the connecting bracket through leveling bolts.

8. The part positioning device for a ship cutting platform according to claim 6, characterized in that, The connection between the connecting bracket and the mounting plate is detachable.

Images