Water turbine runner measuring method based on fusion of multiple measuring devices

Abstract

The invention discloses a water turbine runner measurement method based on fusion of multiple measurement devices. The method comprises the following steps: S1, designing a measurement data fusion system of the multiple measurement devices; s2, arranging measurement accessories in the measurement system; s3, establishing a first-level large-size high-precision positioning network, and obtaining a high-precision distance scale; s4, establishing a secondary measurement distribution diagram, and obtaining three-dimensional coordinate points of all circular target points in the panoramic image of the whole workpiece; and S5, carrying out local point cloud scanning, carrying out real-time data splicing, and obtaining complete workpiece point cloud measurement data. According to the measurement method, the measurement efficiency and precision of large-size equipment can be improved.

Description

Technical Field

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

[0002] The measurement of geometric dimensions and form and position tolerances of large hydropower unit parts is a crucial task in unit maintenance. With the gradual increase in the demand for hydropower unit status assessment and energy efficiency indicators, the requirements for the dimensional measurement accuracy of large parts are getting higher and higher, and new requirements are put forward for the in-situ measurement of form and position tolerances. The gap, deformation and state of large equipment assembly cannot be predicted in advance, and the measurement needs for wear and tear of equipment after years of operation are gradually emerging.

[0003] Traditional measurement is mainly done manually, which is often difficult to achieve large-scale on-site measurement and cannot guarantee high-precision global measurement requirements. In addition, manual measurement can only detect simple dimensions, lacks accurate quantitative detection methods for geometric tolerances, and faces problems such as long measurement time and low detection efficiency, resulting in a large waste of human resources. Summary of the invention

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

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: A method for measuring a turbine runner based on fusion of multiple measuring devices comprises the following steps: S1. Design of measurement data fusion system for multiple measurement devices; S2. Arrangement of measurement accessories in the measurement system; S3. Establish a large-scale, high-precision positioning network to obtain a high-precision distance scale; S4, establishing a secondary measurement distribution map, and obtaining the three-dimensional coordinate points of all circular target points in the entire workpiece panoramic image; S5, local point cloud scanning, real-time data stitching, to obtain complete workpiece point cloud measurement data. Furthermore, the step S1 further includes the following steps: S11: Prepare measurement equipment, including laser tracker, industrial photogrammetry and handheld laser scanner; S12: Prepare measurement accessories in the measurement system, including a magnetic base, a measurement target sphere for a laser tracker, a photogrammetric target sphere, photogrammetric coding points, and circular target points, each of which has a unique pattern and a unique number.

[0006] Furthermore, the step S2 further includes the following steps: S21: Arrange the magnetic base. When planning the layout of the magnetic base, it is necessary to distribute it in a three-dimensional space, including up and down, left and right, and front and back directions, to envelop the object to be measured; S22: Paste photographic coding points on the surface of the object to be measured. When arranging the photographic coding points, it is necessary to ensure that when subsequent images are taken, the overlapping photographic coding points of every two images are not less than 6. In the whole project, the photographic coding points are arranged according to the size of the workpiece, and the total number of photographic coding points is not less than 6 at least; S23: Paste a circular target point 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 point.

[0007] Furthermore, in step S21, considering the laser tracker station transfer, the common points of two adjacent stations are no less than 4 points, which are used to unify the measurement coordinate systems of different stations.

[0008] 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 plane; when pasting the photographic coding points, paste them to places where the curvature changes little; all photographic coding points are laid out in positions that can be photographed from multiple angles.

[0009] Furthermore, in step S23, the arrangement of circular target points is determined according to the scanning area of ​​the handheld laser scanner, the number of each frame is not less than 6, the arrangement spacing is 30-80mm, and the circular target points should not be arranged near the photographic coding points.

[0010] Furthermore, the step S3 also includes the following steps: S31: Place the measuring target ball on the magnetic base and use the laser tracker to perform point measurement; S32: The laser tracker is transferred to the next position, and the position measurement of the magnetic base point is performed in the same manner; S33: The coordinates of the magnetic base points 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.

[0011] Furthermore, the step S4 further includes the following steps: S41: Mounting a photographic target sphere on a 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 at multiple angles and positions; S43: Using the coordinates of the magnetic base points measured by the laser tracker as the scale, the calculated three-dimensional coordinate values ​​of the photographic target sphere, the photographic coding points, and the circular target points are scale-compensated to establish a secondary measurement distribution map.

[0012] 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.

[0013] Furthermore, the step S5 further includes the following steps: 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 is collected on the local workpiece surface to finally obtain complete point cloud data of the workpiece.

[0014] The present invention can achieve the following beneficial effects: 1. Utilize the large-range and high-precision distance measurement function of the laser tracker measurement system, the volume accuracy control function of the industrial photogrammetry system, and the high-resolution point cloud scanning function of the handheld laser scanner measurement system to give full play to the advantages of each device and perform high-precision and high-resolution point cloud scanning of the turbine runner to provide high-precision data support for data processing such as repair, simulation, and detection of the turbine runner.

[0015] 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, which 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

[0016] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: 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; Figure 2 The measuring accessories used in the measuring 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 measuring target ball, and a 1.5-inch photogrammetric target ball; the second row from left to right is a 6mm scanning target point and a 6mm photogrammetric coding point; Figure 3 It is a site diagram of the turbine runner of the present invention; Figure 4 A schematic diagram of the layout of the magnetic base of the present invention; Figure 5 It is a schematic diagram of a magnetic base for multi-station measurement of a laser tracker of the present invention; Figure 6 A schematic diagram of the shooting position of the industrial photogrammetry camera of the present invention; Figure 7 A schematic diagram of solving the spatial coordinates of the scanning target point by industrial photogrammetry of the present invention; Figure 8 Schematic diagram of point cloud measured by the handheld laser scanner of the present invention. DETAILED DESCRIPTION

[0017] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0018] A turbine runner measurement method based on the fusion of multiple measurement devices, referring to Figure 1 , including the following steps: S1. Design of measurement data fusion system for multiple measurement devices.

[0019] S11: Prepare measurement equipment, including laser tracker, industrial photogrammetry and handheld laser scanner.

[0020] S12: Prepare the measuring accessories in the measuring system, refer to Figure 2 , including a magnetic base; a measuring target ball for a laser tracker, hereinafter referred to as the measuring target ball; a photogrammetric target ball, hereinafter referred to as the photographic target ball; photogrammetric coding points, and circular target points, which can be automatically identified by a handheld laser scanner.

[0021] Among them, the method of supporting the sphere by three points of the magnetic base ensures that the center coordinates of the measuring 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.

[0022] 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 solve the three-dimensional point coordinates on the two-dimensional image.

[0023] The circular target point is used as the reference positioning point of 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.

[0024] S2. Arrangement of measuring accessories in the measuring system. Figure 3 For the measurement of the turbine runner shape 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.

[0025] 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 envelop 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 when measuring over a large range, the first-level large-size high-precision positioning network is critical to determine the size of the entire workpiece, so it is necessary to measure the position of the magnetic base at multiple stations, and then use the unified spatial network (USMN) adjustment algorithm to improve the uncertainty of the laser tracker itself, thereby improving the accuracy and reliability of the data.

[0026] 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 an interval 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.

[0027] The distribution of points at the 90° corners of the workpiece shape should ensure that all camera stations for corner shooting have more than 6 photography coding points. If necessary, add some 45° corner points or use 45° corner tooling. The density of photography coding points should also be increased at the 90° corners.

[0028] The photographic coding points are evenly distributed in the area to be tested. The layout positions should cover the boundaries of the area to be tested as much as possible, and should not be laid out on a single plane. When pasting photographic coding points, paste them to places with small curvature changes. Pasting them on a curved surface with large curvature will cause the photographic coding points to deform and lead to recognition errors. All points should be laid out in locations that can be photographed from multiple angles, especially photographic coding points should be laid out in locations that will not be blocked during shooting as much as possible.

[0029] 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, so that the presented point cloud data will be in a unified coordinate system.

[0030] The layout of scanning circular target points is determined according to the scanning area of ​​the handheld laser scanner. The number of single frames is not less than 6, and the layout spacing is usually 30-80mm, which should be determined according to the actual situation of the workpiece. If the surface curvature changes slightly, the distance can be larger, with a maximum distance of 80mm; if the workpiece has many features and the curvature changes greatly, the distance can be reduced, with a minimum distance of 30mm. In addition, circular target points should not be arranged near the photographic coding points.

[0031] The circular target points should be randomly distributed to avoid regular arrangement. The circular target points should not be pasted on the edge of the workpiece. In order to ensure the quality and accuracy of the data, the position of the scanning target points on the workpiece will be deleted when the point cloud data is finally output, forming a hole. The curvature of the hole is filled by the algorithm. The curvature of the edge hole changes greatly, and it is easy to bulge. Therefore, when pasting the points, the marking points must be more than 3mm away from the edge to facilitate the later data repair processing. In addition, when pasting the scanning marking points, you must also pay attention to avoid making the scanning marking points dirty, hidden or damaged.

[0032] 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.

[0033] S31: Place the measuring target ball on the magnetic base and use the laser tracker to perform point measurement.

[0034] S32: Move the laser tracker to the next location and measure the magnetic base points in the same way. Ensure that there are no less than 4 common points between two adjacent locations.

[0035] Due to the wide range of the measurement target sphere, the laser tracker cannot complete the measurement of all magnetic base points at a single station, so it is necessary to transfer the station. After more than three transfers, the problem of transfer error accumulation will be introduced. The unified spatial measurement network (USMN adjustment) method is used for global optimization to obtain the final coordinates of all magnetic base points.

[0036] S33: The coordinates of the magnetic base points 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.

[0037] Specifically, the unified spatial metrology network (USMN adjustment) method is used to integrate and adjust data from multiple measurement sources through a global optimization algorithm to solve the network of multi-station measurements, generate an ideal network of common points, provide uncertainty for all measurements, minimize the systematic error and random error of the primary industrial measurement control network, improve the overall measurement accuracy and reliability, and simplify the data processing process. The optimized USMN point is called the "USMN composite point". The USMN composite point is used as a primary large-scale high-precision positioning network to provide an accurate scale for high-precision measurement of turbine runner blades.

[0038] S4. On the basis of the first-level large-scale high-precision positioning network, industrial photogrammetry is used to establish a second-level measurement distribution map to obtain the three-dimensional coordinate points of all circular target points in the entire workpiece panoramic image. Among them, industrial photogrammetry using the domestic Xingyao I3 photogrammetry system will be more stable.

[0039] S41: Mount the photographic target sphere on the magnetic base.

[0040] S42: Reference Figure 6 , use the industrial photogrammetry system to collect images of all the photographic target balls, photographic coding points and circular target points on the workpiece at multiple angles and positions. When shooting images, since the 6mm photographic coding points are used in this embodiment, the shooting distance shall not exceed 6m, otherwise the image proportion of the points will be very small, affecting the extraction accuracy of the points; during the shooting process, the effective area of ​​the object shall be distributed in the center of the image as much as possible to reduce the image distortion error; the shooting angle of the same point shall be between 30°-150° to reduce the center extraction error caused by too large an angle; the camera needs to be rotated 90° for shooting at the same position in a project, and this position shall be no less than 10 to calibrate the internal parameters of the camera; the number of photographic coding points with the same number in adjacent images shall not be less than 6.

[0041] The relative position relationship between images is established through the unique coding points in the image. After steps such as image extraction, image stitching, front intersection, rear intersection, orientation, and bundle adjustment, multiple images are stitched into a complete panoramic image.

[0042] 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. 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.

[0043] S43: Reference Figure 7 , taking the coordinates of the magnetic base points measured by the laser tracker as the scale, the calculated three-dimensional coordinate values ​​of the photographic target sphere, photographic coding points, and circular target points are scale-compensated to establish a secondary measurement distribution map.

[0044] S5, local point cloud scanning, real-time data stitching, to obtain complete workpiece point cloud measurement data.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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 principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for measuring a turbine runner based on the fusion of multiple measuring devices, characterized in that: The following steps are involved: S1. Design of measurement data fusion system for multiple measurement devices; S2. Arrangement of measurement accessories in the measurement system; S3. Establish a large-scale, high-precision positioning network to obtain a high-precision distance scale; S4, establishing a secondary measurement distribution map, and obtaining the three-dimensional coordinate points of all circular target points in the entire workpiece panoramic image; S5, local point cloud scanning, real-time data stitching, to obtain complete workpiece point cloud measurement data.

2. The method for measuring a turbine runner based on fusion of multiple measuring devices according to claim 1, characterized in that: The step S1 also includes the following steps: S11: Prepare measurement equipment, including laser tracker, industrial photogrammetry and handheld laser scanner; S12: Prepare measurement accessories in the measurement system, including a magnetic base, a measurement target sphere for a laser tracker, a photogrammetric target sphere, photogrammetric coding points, and circular target points, each of which has a unique pattern and a unique number.

3. The method for measuring a turbine runner based on fusion of multiple measuring devices according to claim 2 is characterized in that: The step S2 also includes the following steps: S21: Arrange the magnetic base. When planning the layout of the magnetic base, it is necessary to distribute it in a three-dimensional space, including up and down, left and right, and front and back directions, to envelop the object to be measured; S22: Paste photographic coding points on the surface of the object to be measured. When arranging the photographic coding points, it is necessary to ensure that when subsequent images are taken, the overlapping photographic coding points of every two images are not less than 6. In the whole project, the photographic coding points are arranged according to the size of the workpiece, and the total number of photographic coding points is not less than 6 at least; S23: Paste a circular target point 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 point.

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

5. The method for measuring a turbine runner based on fusion of multiple measuring devices according to claim 3 is 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 plane; when pasting the photographic coding points, paste them to places with small curvature changes; all photographic coding points are laid out at positions that can be photographed from multiple angles.

6. The method for measuring a turbine runner based on fusion of multiple measuring devices according to claim 3 is 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 frame 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.

7. The method for measuring a turbine runner based on fusion of multiple measuring devices according to claim 2 is characterized in that: The step S3 also includes the following steps: S31: Place the measuring target ball on the magnetic base and use the laser tracker to perform point measurement; S32: The laser tracker is transferred to the next position, and the position measurement of the magnetic base point is performed in the same manner; S33: The coordinates of the magnetic base points 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.

8. The method for measuring a turbine runner based on fusion of multiple measuring devices according to claim 2 is characterized in that: The step S4 also includes the following steps: S41: Mounting a photographic target sphere on a 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 at multiple angles and positions; S43: Using the coordinates of the magnetic base points measured by the laser tracker as the scale, the calculated three-dimensional coordinate values ​​of the photographic target sphere, the photographic coding points, and the circular target points are scale-compensated to establish a secondary measurement distribution map.

9. The method for measuring a turbine runner based on fusion of multiple measuring devices according to claim 8, 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.

10. The method for measuring a turbine runner based on fusion of multiple measuring devices according to claim 2, characterized in that: The step S5 also includes the following steps: 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 is collected on the local workpiece surface to finally obtain complete point cloud data of the workpiece.

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