A turbine runner measurement method based on fusion of multiple measurement devices

Abstract

A method for measuring a turbine runner based on the fusion of multiple measurement devices includes the following steps: S1. Designing a system for fusion measurement data from multiple measurement devices; S2. Deploying measurement accessories within the measurement system; S3. Establishing a primary, large-scale, high-precision positioning network to obtain a high-precision distance scale; S4. Establishing a secondary measurement distribution map to obtain the three-dimensional coordinates of all circular target points in a panoramic image of the entire workpiece; and S5. Scanning a local point cloud and stitching the data in real time to obtain complete workpiece point cloud measurement data. This measurement method can improve the measurement efficiency and accuracy of large-scale equipment.

Description

Technical Field

[0001] The present invention belongs to the technical field of large-scale high-precision measurement, and in particular relates to a turbine runner measurement method based on the fusion of multiple measurement devices. Background Art

[0002] Measuring the geometric dimensions and form and position tolerances of large hydropower unit components is a crucial task during unit maintenance. As the need for hydropower unit condition assessment and energy efficiency indicators gradually increase, the requirements for the dimensional measurement accuracy of large components are becoming increasingly stringent, placing new demands on in-situ form and position tolerance measurement. The gaps, deformations, and conditions of large equipment assemblies cannot be predicted in advance, and the need to measure wear and tear after years of operation is gradually emerging.

[0003] Traditional measurement relies primarily on manual measurement, which often makes it difficult to achieve large-scale on-site measurements and cannot guarantee high-precision global measurement requirements. Furthermore, manual measurement can only detect simple dimensions and lacks precise quantitative methods for geometric tolerances. Furthermore, manual measurement suffers from long measurement times and low efficiency, resulting in a significant waste of human resources. Summary of the Invention

[0004] The present invention provides a turbine runner measurement method based on the fusion of multiple measurement devices to solve the problem of low measurement efficiency of large-scale equipment.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A method for measuring a turbine runner based on fusion of multiple measuring devices comprises the following steps:

[0007] S1. Design of measurement data fusion system for multiple measurement devices;

[0008] S2. Layout of measurement accessories in the measurement system;

[0009] S3. Establish a large-scale, high-precision positioning network to obtain a high-precision distance scale;

[0010] S4. Establish a secondary measurement distribution map to obtain the three-dimensional coordinates of all circular target points in the entire workpiece panoramic image;

[0011] S5: Local point cloud scanning and real-time data stitching to obtain complete workpiece point cloud measurement data.

[0012] Furthermore, the step S1 further includes the following steps:

[0013] S11: Prepare measurement equipment, including laser tracker, industrial photogrammetry and handheld laser scanner;

[0014] S12: Prepare measurement accessories in the measurement system, including a magnetic base, a measurement target sphere for a laser tracker, a photogrammetry target sphere, photogrammetry coding points, and circular target points. Each photogrammetry coding point has a unique pattern and a unique number.

[0015] Furthermore, the step S2 further includes the following steps:

[0016] S21: Arrange the magnetic base. When planning the layout of the magnetic base, it needs to be distributed in three-dimensional space, including up and down, left and right, and front and back directions, to enclose the object to be measured;

[0017] S22: Paste photographic coding points on the surface of the object to be measured. When arranging photographic coding points, ensure that when subsequent images are taken, there are at least 6 overlapping photographic coding points between every two images. During the entire project, photographic coding points are arranged according to the size of the workpiece, and the total number of photographic coding points is at least 6;

[0018] S23: Paste circular target points on the surface of the object to be measured, and calculate the position and posture of the handheld laser scanner in real time by scanning the circular target points.

[0019] Furthermore, in step S21, considering the laser tracker station transfer, the common points between two adjacent stations are no less than 4 points, which are used to unify the measurement coordinate systems of different stations.

[0020] Furthermore, in step S22, the photographic coding points are evenly distributed in the area to be measured, and the layout positions should cover the boundaries of the area to be measured, and should not be laid out on a single plane; when pasting the photographic coding points, they should be pasted to places where the curvature changes little; all photographic coding points are laid out in positions that can be photographed from multiple angles.

[0021] Furthermore, in step S23, the layout of circular target points is determined according to the scanning area of ​​the handheld laser scanner, the number of circular target points in a single area is not less than 6, the layout spacing is 30-80mm, and the circular target points should not be arranged near the photographic coding points.

[0022] Furthermore, the step S3 further includes the following steps:

[0023] S31: Place the measuring target ball on the magnetic base and use the laser tracker to perform point measurement;

[0024] S32: Move the laser tracker to the next location and perform position measurement on the magnetic base point in the same way;

[0025] S33: The magnetic base point coordinates of the final adjustment are used as a first-level large-scale high-precision positioning network to provide an accurate scale for high-precision measurement of turbine runner blades.

[0026] Furthermore, the step S4 further includes the following steps:

[0027] S41: Install the photographic target sphere on the magnetic base;

[0028] S42: Use the industrial photogrammetry system to collect images of all the photographic target balls, photographic coding points and circular target points on the workpiece from multiple angles and positions;

[0029] S43: Using the coordinates of the magnetic base points measured by the laser tracker as a scale, scale compensation is performed on the calculated three-dimensional coordinate values ​​of the photographic target sphere, photographic coding points, and circular target points to establish a secondary measurement distribution map.

[0030] Furthermore, in step S42, when capturing an image, the effective area of ​​the object is distributed in the center of the image as much as possible; the shooting angle for the same point is between 30° and 150°; and the number of photographic coding points with the same number in adjacent images is not less than 6.

[0031] Furthermore, the step S5 further includes the following steps:

[0032] S51: Use a handheld laser scanner to scan and measure the local circular target point to obtain the three-dimensional coordinates of the local circular target point;

[0033] S52: The three-dimensional coordinates of the local circular target point are matched in real time with the secondary measurement distribution map in step S43 to obtain the position and posture information of the local handheld laser scanner;

[0034] S53: Based on the acquired position and posture information, point cloud data of the local workpiece surface is collected to finally obtain complete point cloud data of the workpiece.

[0035] The present invention can achieve the following beneficial effects:

[0036] 1. Leveraging the large-scale and high-precision distance measurement capabilities of the laser tracker measurement system, the volumetric accuracy control capabilities of the industrial photogrammetry system, and the high-resolution point cloud scanning capabilities of the handheld laser scanner measurement system, we leverage the advantages of each device to perform high-precision, high-resolution point cloud scanning of the turbine runner, providing high-precision data support for data processing such as repair, simulation, and testing of the turbine runner.

[0037] 2. Use industrial photogrammetry to capture photographic coding points and circular target points, and use the first-level large-scale high-precision positioning network as the global scale to provide high-precision scaling for the second-level measurement distribution map. The calculated three-dimensional coordinates of the circular target points provide a scanning measurement control network for the handheld scanner. This can avoid large-scale splicing errors of the handheld scanner and improve the spatial volume accuracy of the scanner; setting a second-level measurement distribution map can improve the volume accuracy of the scanner's large-scale measurement and reduce the problem of cumulative amplification of scanning splicing errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The present invention will be further described below with reference to the accompanying drawings and examples:

[0039] Figure 1 This is a flow chart of a high-precision measurement method for a turbine runner based on the fusion of multiple measurement devices;

[0040] Figure 2 The measuring accessories used in the measurement process of the present invention are: the first row from left to right is a 1.5-inch magnetic base, a 1.5-inch laser tracker measurement target sphere, and a 1.5-inch photogrammetry target sphere; the second row from left to right is a 6mm scanning target point and a 6mm photogrammetry encoding point;

[0041] Figure 3 This is a site diagram of the turbine runner of the present invention;

[0042] Figure 4 A schematic diagram of the layout of the magnetic base of the present invention;

[0043] Figure 5 Schematic diagram of a magnetic base for multi-station measurement of a laser tracker according to the present invention;

[0044] Figure 6 A schematic diagram of the shooting position of the industrial photogrammetry camera of the present invention;

[0045] Figure 7 A schematic diagram of the industrial photogrammetry method for calculating the spatial coordinates of a scanning target point according to the present invention;

[0046] Figure 8 Schematic diagram of the point cloud measured by the handheld laser scanner of the present invention. DETAILED DESCRIPTION

[0047] To facilitate understanding of the present application, the present application will be described more fully below with reference to the accompanying drawings. The accompanying drawings provide embodiments of the present application. However, the present application may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to make the disclosure of the present application more thorough and comprehensive.

[0048] A turbine runner measurement method based on the fusion of multiple measurement devices, referring to Figure 1 , including the following steps:

[0049] S1. Design of measurement data fusion system for multiple measurement devices.

[0050] S11: Prepare measurement equipment, including laser tracker, industrial photogrammetry and handheld laser scanner.

[0051] S12: Prepare the measuring accessories in the measuring system, refer to Figure 2 , including a magnetic base; a measuring target ball for the laser tracker, hereinafter referred to as the measuring target ball; a photogrammetry target ball, hereinafter referred to as the photographic target ball; photogrammetry coding points, and circular target points, which can be automatically identified by a handheld laser scanner.

[0052] Among them, the method of supporting the sphere by three points on the magnetic base ensures that the center coordinates of the measurement target sphere and the photographic target sphere of the same diameter are consistent, which is used for the fusion of laser tracker and industrial photogrammetry data.

[0053] Each photogrammetric code point has a unique pattern and a unique number. In the same project file, industrial photogrammetry can identify and match the same code points in multiple images, accurately calculate the relative position and posture between images, and thus calculate the three-dimensional coordinates of points on a two-dimensional image.

[0054] The circular target point serves as the reference positioning point for the handheld laser scanner at different scanning positions. By identifying the circular target point in a single scanning area, the relative position and posture between each scan are calculated, and the data of multiple scans are seamlessly spliced ​​together to form a complete 3D point cloud measurement data.

[0055] S2, the arrangement of measuring accessories in the measuring system. Figure 3 For the measurement of the shape of a turbine runner with a diameter of 10 meters and a height of 5 meters, a 1.5-inch magnetic base, a 6mm photographic coding point, and a 6mm circular target point are first laid out.

[0056] S21: Arrange the magnetic base, refer to Figure 4, magnetic bases are laid out on the upper crown, blades, lower ring and ground of the turbine runner. When planning the position, it is necessary to distribute it in three-dimensional space, including up and down, left and right, front and back directions, to enclose the object to be measured. Taking into account the laser tracker station transfer, there are no less than 4 common points between two adjacent stations, which are used to unify the measurement coordinate systems of different stations. Among them, the measurement station refers to the placement of the laser tracker, because in large-scale measurements, the first-level large-scale high-precision positioning network is critical. The size of the entire workpiece is determined, so the position of the magnetic base needs to be measured at multiple stations, and then the unified spatial network (USMN) adjustment algorithm is used to improve the uncertainty of the laser tracker itself, thereby improving the accuracy and reliability of the data.

[0057] S22: Paste photographic coding points on the surface of the object to be measured. In the embodiment of the present application, a 6mm photographic coding point is pasted on the outer surface of the turbine runner at intervals of 0.5 meters. The photographic coding points are arranged to ensure that when subsequent images are taken, there are no less than 6 overlapping photographic coding points between every two images. In the entire project, the photographic coding points are arranged according to the size of the workpiece, and the total number of photographic coding points cannot be less than 6.

[0058] The distribution of points at the 90° corners of the workpiece shape should ensure that the camera stations for corner shooting have more than 6 photography coding points. If necessary, some 45° corner points should be added or 45° corner tooling should be used. The density of photography coding points should also be increased at the 90° corners.

[0059] Photographic code points should be evenly distributed across the area to be measured. They should be placed as close to the boundaries of the area as possible and should not be placed on a single plane. When attaching photographic code points, place them where the curvature is minimal. Attaching them to surfaces with large curvatures can cause deformation and lead to recognition errors. All points should be placed in locations that can be captured from multiple angles. In particular, photographic code points should be placed where they are not obstructed during photography.

[0060] S23: Paste circular target points on the surface of the object to be measured, and calculate the position and posture of the handheld laser scanner in real time by scanning the circular target points. In this way, the point cloud data presented will be in a unified coordinate system.

[0061] The placement of circular scanning targets is determined by the handheld laser scanner's scanning area. Each frame should contain at least six targets, typically spaced 30-80 mm apart, depending on the workpiece's actual conditions. If the surface curvature varies slightly, the spacing can be larger, with a maximum of 80 mm. If the workpiece has numerous features and significant curvature variations, the spacing can be reduced, with a minimum of 30 mm. Furthermore, circular targets should not be placed near photographic encoding points.

[0062] The circular target points should be randomly distributed, avoiding regular patterns. They should not be placed on the edge of the workpiece. To ensure data quality and accuracy, the location where the scanning target points are placed on the workpiece will be deleted when the point cloud data is output, forming a hole. The algorithm then fills the hole with curvature. The curvature of the edge hole varies greatly, making it prone to bulging. Therefore, when placing the points, the markers must be at least 3mm away from the edge to facilitate later data patching. In addition, when placing the scanning markers, care should be taken to avoid soiling, hiding, or damaging the scanning markers.

[0063] S3. Reference Figure 5 ,Use the laser tracker measurement system to establish a first-level large-scale high-precision positioning network and obtain a high-precision distance scale.

[0064] S31: Place the measuring target ball on the magnetic base and use the laser tracker to perform point measurement.

[0065] S32: Move the laser tracker to the next location and perform position measurement on the magnetic base points in the same manner. Ensure that there are at least four common points between two adjacent locations.

[0066] Due to the wide range of measurement targets, a single laser tracker station cannot measure all magnetic base points, necessitating station rotation. More than three station rotations introduce cumulative station errors. Therefore, a global optimization using the Unified Spatial Metrology Network (USMN) adjustment method was used to obtain the final coordinates of all magnetic base points.

[0067] S33: The magnetic base point coordinates of the final adjustment are used as a first-level large-scale high-precision positioning network to provide an accurate scale for high-precision measurement of turbine runner blades.

[0068] Specifically, the Unified Spatial Metrological Network (USMN) adjustment method was used to integrate and adjust data from multiple measurement sources through a global optimization algorithm. This method solves the multi-station measurement network, produces an ideal network of common points, and provides uncertainty for all measurements. This minimizes the systematic and random errors of the primary industrial measurement control network, improves overall measurement accuracy and reliability, and simplifies the data processing process. The optimized USMN points are called "USMN composite points." Using the USMN composite points as a primary large-scale, high-precision positioning network provides an accurate scale for high-precision measurements of turbine runner blades.

[0069] S4. Based on the first-level large-scale, high-precision positioning network, industrial photogrammetry is used to establish a second-level measurement distribution map to obtain the 3D coordinates of all circular target points in the entire workpiece panoramic image. Among them, industrial photogrammetry using the domestically produced Xingyao I3 photogrammetry system is more stable.

[0070] S41: Mount the photographic target on the magnetic base.

[0071] S42: Reference Figure 6 , using an industrial photogrammetry system to capture images of all photographic target spheres, photographic coding points, and circular target points on the workpiece from multiple angles and positions. During image capture, since this embodiment uses 6mm photographic coding points, the shooting distance should not exceed 6m; otherwise, the image percentage of the point will be very small, affecting point extraction accuracy. During the capture process, the effective area of ​​the object should be distributed as close to the center of the image as possible to reduce image distortion errors. The shooting angle for the same point should be between 30° and 150° to reduce center extraction errors caused by excessive angles. The camera should be rotated 90° for shooting at the same location in a project at least 10 times to calibrate the camera's internal parameters. The number of photographic coding points with the same number in adjacent images should be no less than 6.

[0072] The relative position relationship between images is established through the unique coding points in the images. After steps such as image extraction, image stitching, front intersection, rear intersection, orientation, and bundle adjustment, multiple images are stitched together into a complete panoramic image.

[0073] By using the collinear equation as a mathematical model, the image plane coordinate observation value of the image point is a nonlinear function of the unknown number. After linearization, it is calculated according to the least squares principle and iterated repeatedly to reach the optimal value, thereby obtaining the three-dimensional coordinate values ​​of all photographic target balls, photographic coding points, and circular target points in the panoramic image of the entire workpiece.

[0074] S43: Reference Figure 7 , using the coordinates of the magnetic base points measured by the laser tracker as the scale, the scale compensation is performed on the calculated three-dimensional coordinate values ​​of the photographic target sphere, photographic coding points, and circular target points to establish a secondary measurement distribution map.

[0075] S5: Local point cloud scanning and real-time data stitching to obtain complete workpiece point cloud measurement data.

[0076] S51: Use a handheld laser scanner to scan and measure the local circular target point to obtain the three-dimensional coordinates of the local circular target point.

[0077] S52: The three-dimensional coordinates of the local circular target point are matched with the secondary measurement distribution map in step S43 in real time to obtain the position and posture information of the local handheld laser scanner.

[0078] S53: Reference Figure 8 ,According to the acquired position and posture information, the point cloud data of the local workpiece surface is collected, and finally the complete point cloud data of the workpiece is obtained.

[0079] 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, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A turbine runner measurement method based on the fusion of multiple measurement devices, characterized in that: The following steps are involved: S1. Design of measurement data fusion system for multiple measurement devices; S11: Prepare measurement equipment, including laser tracker, industrial photogrammetry and handheld laser scanner; S12: Prepare the measurement accessories in the measurement system, including the magnetic base, the measurement target ball for the laser tracker, the photogrammetry target ball, the photogrammetry coding points, and the circular target points. Each photogrammetry coding point has a unique pattern and a unique number. S2. Layout of measurement accessories in the measurement system; S3. Establish a large-scale, high-precision positioning network to obtain a high-precision distance scale; S31: Place the measuring target ball on the magnetic base and use the laser tracker to perform point measurement; S32: Move the laser tracker to the next location and perform position measurement on the magnetic base point in the same way; S33: The magnetic base point coordinates of the final adjustment are used as a first-level large-scale high-precision positioning network to provide an accurate scale for high-precision measurement of turbine runner blades; S4. Establish a secondary measurement distribution map to obtain the three-dimensional coordinates of all circular target points in the entire workpiece panoramic image; S41: Install the photographic target sphere on the magnetic base; S42: Use the industrial photogrammetry system to collect images of all the photographic target balls, photographic coding points and circular target points on the workpiece from multiple angles and positions; S43: Using the coordinates of the magnetic base point measured by the laser tracker as a scale, scale compensation is performed on the calculated three-dimensional coordinate values ​​of the photographic target sphere, photographic coding points, and circular target points to establish a secondary measurement distribution map; S5, local point cloud scanning, real-time data stitching, to obtain complete workpiece point cloud measurement data; S51: Use a handheld laser scanner to scan and measure the local circular target point to obtain the three-dimensional coordinates of the local circular target point; S52: The three-dimensional coordinates of the local circular target point are matched in real time with the secondary measurement distribution map in step S43 to obtain the position and posture information of the local handheld laser scanner; S53: Based on the acquired position and posture information, point cloud data of the local workpiece surface is collected to finally obtain complete point cloud data of the workpiece.

2. The method for measuring a turbine runner based on fusion of multiple measuring devices according to claim 1, characterized in that: The step S2 further includes the following steps: S21: Arrange the magnetic base. When planning the layout of the magnetic base, it needs to be distributed in three-dimensional space, including up and down, left and right, and front and back directions, to enclose the object to be measured; S22: Paste photographic coding points on the surface of the object to be measured. When arranging photographic coding points, ensure that when subsequent images are taken, there are at least 6 overlapping photographic coding points between every two images. During the entire project, photographic coding points are arranged according to the size of the workpiece, and the total number of photographic coding points is at least 6; S23: Paste circular target points on the surface of the object to be measured, and calculate the position and posture of the handheld laser scanner in real time by scanning the circular target points.

3. The method for measuring a hydraulic turbine runner based on fusion of multiple measuring devices according to claim 2, characterized in that: In step S21, taking into account the laser tracker station transfer, the common points between two adjacent stations are no less than 4 points, which are used to unify the measurement coordinate systems of different stations.

4. The method for measuring a turbine runner based on fusion of multiple measuring devices according to claim 2, characterized in that: In step S22, the photographic coding points are evenly distributed in the area to be measured, and the layout positions should cover the boundaries of the area to be measured, and should not be laid out on a single plane; when pasting the photographic coding points, paste them to places with small curvature changes; all photographic coding points are laid out in positions that can be photographed from multiple angles.

5. The method for measuring a hydraulic turbine runner based on fusion of multiple measuring devices according to claim 2, characterized in that: In step S23, the layout of circular target points is determined according to the scanning area of ​​the handheld laser scanner. The number of circular target points in a single area is not less than 6, and the layout spacing is 30-80mm. The circular target points should not be arranged near the photographic coding points.

6. The method for measuring a turbine runner based on fusion of multiple measuring devices according to claim 1, characterized in that: In step S42, when capturing an image, the effective area of ​​the object is distributed in the center of the image as much as possible; the shooting angle for the same point is between 30° and 150°; and the number of photographic coding points with the same number in adjacent images is not less than 6.

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