Water turbine runner blade crack repairing method

Abstract

A water turbine runner blade crack repairing method comprises the following steps that S1, a quick-change tool is designed at the tail end of a robot according to a runner crack repairing process; s2, a vision measurement device is installed at the tail end of the robot, and a hand-eye calibration method is adopted to complete unification of a vision measurement coordinate system and a robot tail end flange coordinate system; calibration of the robot and various end tools is completed at the same time; s3, performing deep flaw detection on the runner crack area by using an ultrasonic phased array, determining the depth of each position of the runner crack, and constructing a runner crack envelope in trajectory planning software; performing feature extraction on the standard ball to obtain a ball center coordinate; s4, constructing a workpiece coordinate system on the center of the standard ball subjected to feature extraction, generating robot machining point location data in track planning software by combining with the runner crack envelope body model, generating a robot machining track program by utilizing robot inverse kinematics and a track optimization strategy, and performing track simulation in track processing software to obtain a robot machining track program; and generating a robot processing track program. The water turbine runner crack repairing efficiency, quality and precision are effectively improved, and the manual repairing risk is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of robots, and in particular relates to a method for repairing cracks in turbine runner blades. Background Art

[0002] After a long period of service, the runner of a large hydropower unit will be impacted by water flow for a long time, and cracks, cavitation and other defects will appear in the joint area between the root of the runner blade and the lower ring of the runner. Currently, most of the repair methods for the above runner defects are manual repair. First, the defect detection is carried out by manually spraying the flaw detection agent, and then the defect area is cleaned, filled and polished by manual air gouging, welding and grinding to ensure that the profile of the runner before and after repair is consistent.

[0003] However, the manual repair method cannot guarantee the repair quality and shaping effect of the runner due to the different levels of manual skills. Summary of the invention

[0004] The present invention provides a method for repairing cracks in a turbine runner blade, so as to solve the problem that the quality of repairing defects of the runner is difficult to ensure.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: A method for repairing cracks in a turbine runner blade comprises the following steps: S1. According to the runner crack repair process, a quick-change tooling is designed at the end of the robot to facilitate the robot to replace the end tool in different processes and quickly perform the runner crack repair operation; S2. Install a visual measurement device at the end of the robot, and use the hand-eye calibration method to complete the conversion between the visual measurement coordinate system and the robot end flange coordinate system; at the same time, complete the calibration of the robot and various end tools to ensure that the planned robot processing trajectory can be accurately reached; S3. Use ultrasonic phased array to conduct deep flaw detection on the crack area of ​​the runner, determine the depth of each position of the runner crack, and construct the runner crack envelope in the trajectory planning software; at the same time, perform feature extraction on the standard ball to obtain the coordinates of the ball center; S4. Construct a workpiece coordinate system on the center of the feature-extracted standard ball, generate robot processing point data in the trajectory planning software in combination with the runner crack envelope model, generate a robot processing trajectory program using robot inverse kinematics and trajectory optimization strategy, and perform trajectory simulation in the trajectory processing software to generate a robot processing trajectory program.

[0006] Furthermore, in step S2, the hand-eye calibration algorithm specifically includes: installing a visual measurement device at the end of the robot, controlling the robot to drive the visual measurement device to shoot the calibration plate in different postures on the calibration plate, and recording the calibration plate data of the robot in different postures, as well as the posture data of the robot; The spatial pose transformation matrix of the visual measurement device relative to the robot end flange is obtained by processing in the data analysis software, and the spatial pose transformation between the visual measurement coordinate system and the robot flange coordinate system is realized through this matrix.

[0007] Furthermore, in step S2, the robot end tool calibration method includes: A plurality of second standard target balls are pasted on the end tool, and the position information of the second standard target balls on the end tool is recorded using a laser tracker. The surface point cloud data of the end tool and the second standard target ball are scanned using a handheld scanner. The center position data of the second standard target ball is extracted in the data processing software. The point registration function is used in the data analysis software to convert the reverse modeled tool model into the robot end flange coordinate system.

[0008] Furthermore, before the robot end tool calibration is performed in step S2, it also includes: fixing a laser tracker in an open area as the origin of the reference system, fixing a first standard target ball on the robot end flange, driving the robot to move linearly and spatially around the end flange coordinate system in the robot's initial tool coordinate system, and using a laser tracker to track and locate the position of the first standard target ball to complete the flange coordinate system calibration.

[0009] Furthermore, in step S3, the operation steps of creating the runner crack envelope include: Use PT flaw detection on the turbine runner blades to determine the direction of the cracks, paste reflective marking points on the blades to help the visual measurement device collect runner blade crack data, and paste standard balls on the surface of the turbine runner blades to envelop the runner crack direction; A handheld scanner is used to collect point clouds of the crack area of ​​the turbine runner blade with the marker points attached and the standard sphere, and the collected marker points and standard sphere of the blade crack area are processed in the point cloud processing software.

[0010] Furthermore, in step S3, when standard balls are pasted on the surface of the turbine runner blade, three standard balls of different specifications are used to envelop the crack direction of the runner.

[0011] Furthermore, in step S3, when processing the marker points, B-spline fitting is performed on the marker points to determine the crack direction, the B-spline fitting curve is offset along the surface normal direction, and the maximum spacing on the B-spline curve is used as the width of the envelope model to create a crack envelope surface model.

[0012] Furthermore, in step S3, when processing the standard sphere, feature extraction is performed on the standard sphere to construct a plane with the extracted sphere center as the reference point, and one of the sphere centers is selected to create a workpiece coordinate system, and the constructed impeller blade crack surface envelope model is converted to the workpiece coordinate system established by the standard sphere.

[0013] Furthermore, in step S4, the construction of the workpiece coordinate system includes: using a visual measurement device after robot hand-eye calibration to scan the standard sphere, performing feature extraction on the standard sphere point cloud data obtained by the scan in the software to obtain the center of the standard sphere, constructing a plane for the three standard spheres obtained by the scan through a coordinate system construction method, selecting a sphere center as the origin and taking the line connecting the sphere centers as the X-axis, taking the normal line perpendicular to the plane constructed by the sphere center and passing through the origin as the Z-axis, taking the normal line perpendicular to the XOZ plane and passing through the origin as the Y-axis to create a workpiece coordinate system, and outputting the position data of the current workpiece coordinate system.

[0014] Furthermore, in step S4, after the workpiece coordinate system component is completed, the transformation matrix from the workpiece coordinate system created by the standard sphere to the robot base coordinate system is solved, and the runner blade crack envelope model created in step three is spatially transformed to obtain the runner blade crack envelope model in the robot base coordinate system.

[0015] The present invention can achieve the following beneficial effects: 1. The present invention uses ultrasonic phased array and 3D vision to detect the cracks of the mixed flow impeller to determine the crack direction and crack depth, uses a handheld scanner to complete the scan of the impeller crack area and then reversely models and constructs a crack envelope model, and completes the coordinate system in the robot processing process through visual measurement, which reduces the difficulty of manually determining the crack depth and crack repair area and improves the efficiency of on-site repair.

[0016] 2. The present invention designs an end tool conversion tooling at the end of the robot to quickly replace the various repair processes and end tools involved in the crack repair process, and uses a robot to replace the repeated manual repair parts involved in the crack repair link of the mixed flow runner, thereby reducing the difficulty of on-site repair operations and ensuring the consistency of repair quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 It is a flow chart of a method for repairing cracks in a turbine runner blade according to the present invention; Figure 2 is a schematic diagram of the crack trend of the runner blade involved in the present invention; Figure 3 Schematic diagram of the crack trend of the runner blade according to the landmark point fitting of the present invention; Figure 4 It is a schematic diagram of a method of sticking a standard ball near a crack of a runner blade of the present invention; Figure 5 It is a schematic diagram of the method for creating the crack envelope model of the runner blade of the present invention; Figure 6It is a schematic diagram of the workpiece coordinate system construction method of the present invention; Figure 7 It is a schematic diagram of the conversion process of the crack envelope model of the present invention to the robot base coordinate system. DETAILED DESCRIPTION

[0018] 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.

[0019] The present application discloses a method for repairing cracks in a turbine runner blade, referring to Figure 1 , including the following steps: Step 1: According to the repair process of the turbine runner crack, i.e., the repair process of visual measurement, milling, cladding, grinding and polishing, the end tool changer of the crack repair robot is designed. Specifically, a quick-change tool is installed at the end of the robot used to repair the runner crack to facilitate the rapid replacement of visual measurement equipment, grinding and polishing, milling, and cladding tools. The purpose is to facilitate the robot to quickly replace the end tool when it reaches different processing requirements, ensure the robot's motion accuracy, and enable the robot to execute the processing trajectory faster.

[0020] The quick-change tooling should be an automatic quick-change with good air-tight performance and high positioning accuracy, so as to ensure that the quick-change tooling has good repeat positioning accuracy after installation. In order to ensure the stability of the quick-change tooling and the accuracy of the quick-change tooling after installation, a pneumatic locking structure is used to further clamp the quick-change tooling to ensure that the robot does not shake when performing milling.

[0021] Step 2: Use the hand-eye calibration algorithm and robot end-tool calibration to complete the calibration of the robot and various end-tools to ensure that the planned robot processing trajectory can be accurately reached.

[0022] Complete the robot end tool coordinate system calibration. The main steps are as follows: In an open area, a laser tracker is fixed as the origin of the reference system. A handheld scanner is used to scan the calibrated robot end flange and multiple connected and installed end tools for reverse modeling to create an end tool model. The first standard target ball is fixed on the robot end flange, and the robot is driven to move linearly and spatially around the end flange coordinate system. The laser tracker is used to track and locate the position of the first standard target ball to complete the calibration of the end flange coordinate system.

[0023] Paste multiple second standard target balls on the end tool, use a laser tracker to record the position information of the second standard target balls on the end tool, use a handheld scanner to scan the surface point cloud data of the end tool and the second standard target ball, extract the center position data of the second standard target ball in the data processing software, and use the point registration function in the data analysis software to convert the reverse modeled end tool model to the robot end flange coordinate system. Specifically, the end tool coordinate system is constructed in the software according to the actual contact points of the end tool, and the spatial transformation matrix of each end tool coordinate system of the robot relative to the robot end flange coordinate system is obtained through the spatial transformation of the software reference coordinate system, thereby completing the calibration of the robot end tool coordinate system.

[0024] To complete the robot hand-eye calibration, the main operating steps are as follows: install the visual measurement device on the end flange of the robot, control the robot to drive the visual measurement device to shoot the calibration plate in different postures on the calibration plate, record the calibration plate data and the robot's posture data in different postures, and process them in the data analysis software to obtain the spatial posture transformation matrix of the visual measurement device relative to the end flange of the robot.

[0025] The visual measurement coordinate system and the robot end flange coordinate system are unified through the spatial posture transformation matrix. According to the established homogeneous transformation matrix between the robot end flange and the end visual measurement equipment, the workpiece point cloud data in the visual measurement coordinate system is converted to the robot base coordinate system. It should be noted that the end flange coordinate system corresponds to the robot base coordinate system, and determining the robot base coordinate system determines the end flange coordinate system.

[0026] Step 3: Use ultrasonic phased array to conduct deep flaw detection on the crack area of ​​the runner, determine the depth of each position of the crack of the runner, and construct the crack envelope of the runner in the trajectory planning software; at the same time, perform feature extraction on the standard ball to obtain the coordinates of the sphere center.

[0027] The steps to create the runner crack envelope include: like Figure 2 The figure shows the crack direction of the runner blade. The crack direction is determined by using PT flaw detection on the turbine runner blade. Figure 3 As shown in Figure 1, reflective markings are pasted on the blades to help the visual measurement device collect the runner blade crack data. After the crack is determined, Figure 4 As shown, three standard balls of different specifications are pasted on the surface of the turbine runner blade to envelop the crack direction of the runner and reduce the magnification error caused by constructing the coordinate system with the standard balls.

[0028] Use a handheld scanner to collect point clouds of the turbine runner blade crack area and the standard sphere with the marker points attached, and process the collected marker points and the standard sphere in the blade crack area in the point cloud processing software. Perform B-spline fitting on the marker points to determine the crack direction, offset the B-spline fitting curve along the surface normal direction, and create a crack envelope surface model with the maximum spacing on the B-spline curve as the width of the envelope model. Figure 5 As shown, feature extraction is performed on the standard sphere to construct a plane using the extracted sphere center as a reference point, and one of the sphere centers is selected to create a workpiece coordinate system, and the constructed runner blade crack surface envelope model is converted to the workpiece coordinate system established by the standard sphere.

[0029] The ultrasonic phased array is used to detect the crack mark point area of ​​the runner blade to obtain the crack depth data and record the corresponding mark point data and depth data. The depth data of the mark point area is input into the above-mentioned point cloud processing software to construct a complete envelope model.

[0030] Step 4: Construct a workpiece coordinate system on the center of the feature-extracted standard ball, generate robot processing point data in the trajectory planning software in combination with the runner crack envelope model, generate the robot processing trajectory program using robot inverse kinematics and trajectory optimization strategy, and perform trajectory simulation in the trajectory processing software to generate the robot processing trajectory program.

[0031] The robot processing trajectory planning steps include: Construction of workpiece coordinate system under robot base coordinate system: Figure 6 As shown, the standard sphere is scanned using a visual measurement device after robot hand-eye calibration, and the center of the standard sphere is obtained by feature extraction of the scanned point cloud data in the software. A plane is constructed for the three standard spheres obtained by the scan by using the coordinate system construction method. A sphere center is selected as the origin, and the line connecting the sphere centers is used as the X-axis. The normal line perpendicular to the plane constructed by the sphere center and passing through the origin is used as the Z-axis, and the normal line perpendicular to the XOZ plane and passing through the origin is used as the Y-axis to create a workpiece coordinate system, and the position data of the current workpiece coordinate system is output.

[0032] Envelope model coordinate system conversion: Figure 7 As shown, the origin coordinate system of the runner blade crack envelope model created in step three is a reference coordinate system established by a standard sphere, and the transformation matrix from the workpiece coordinate system created by the standard sphere to the robot base coordinate system is solved; the runner blade crack envelope model created in step three is spatially transformed to obtain the runner blade crack envelope model in the robot base coordinate system.

[0033] Robot additive and subtractive material repair machining trajectory planning: Import the runner blade crack envelope model after spatial transformation into the trajectory planning software, and perform layered path planning on the envelope model in combination with robot milling, welding, cladding, grinding and polishing process parameters in the software to generate envelope machining path point data relative to the workpiece coordinate system. In the software, the robot additive and subtractive material repair machining trajectory is planned according to the robot inverse kinematics and robot collision interference detection algorithm modules, and the trajectory motion simulation is performed in the trajectory processing software to verify the accuracy and reliability of the generated robot machining trajectory program. After the simulated motion detection is correct, the robot machining program is generated.

[0034] By adopting the mixed flow impeller blade crack robot additive and subtractive material repair processing of the present application, the robot can quickly repair the crack area of ​​the turbine impeller blade with accuracy and efficiency requirements.

[0035] 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 repairing cracks in a turbine runner blade, characterized in that: The following steps are involved: S1. According to the runner crack repair process, a quick-change tooling is designed at the end of the robot to facilitate the robot to replace the end tool in different processes and quickly perform the runner crack repair operation; S2. Install a visual measurement device at the end of the robot, and use the hand-eye calibration method to complete the conversion between the visual measurement coordinate system and the robot end flange coordinate system; at the same time, complete the calibration of the robot and various end tools to ensure that the planned robot processing trajectory can be accurately reached; S3. Use ultrasonic phased array to conduct deep flaw detection on the crack area of ​​the runner, determine the depth of each position of the runner crack, and construct the runner crack envelope in the trajectory planning software; at the same time, perform feature extraction on the standard ball to obtain the coordinates of the ball center; S4. Construct a workpiece coordinate system on the center of the feature-extracted standard ball, generate robot processing point data in the trajectory planning software in combination with the runner crack envelope model, generate a robot processing trajectory program using robot inverse kinematics and trajectory optimization strategy, and perform trajectory simulation in the trajectory processing software to generate a robot processing trajectory program.

2. A method for repairing cracks in a turbine runner blade according to claim 1, characterized in that: In step S2, the hand-eye calibration algorithm specifically includes: installing a visual measurement device at the end of the robot, controlling the robot to drive the visual measurement device to shoot the calibration plate in different postures on the calibration plate, and recording the calibration plate data of the robot in different postures, as well as the posture data of the robot; The spatial pose transformation matrix of the visual measurement device relative to the robot end flange is obtained by processing in the data analysis software, and the spatial pose transformation between the visual measurement coordinate system and the robot flange coordinate system is realized through this matrix.

3. A method for repairing cracks in a turbine runner blade according to claim 1, characterized in that: In step S2, the robot end tool calibration method includes: A plurality of second standard target balls are pasted on the end tool, and the position information of the second standard target balls on the end tool is recorded using a laser tracker. The surface point cloud data of the end tool and the second standard target ball are scanned using a handheld scanner. The center position data of the second standard target ball is extracted in the data processing software. The point registration function is used in the data analysis software to convert the reverse modeled tool model into the robot end flange coordinate system.

4. A method for repairing cracks in a turbine runner blade according to claim 3, characterized in that: Before the robot end tool calibration is performed in step S2, it also includes: fixing a laser tracker in an open area as the origin of the reference system, fixing a first standard target ball on the robot end flange, driving the robot to move linearly and spatially around the end flange coordinate system in the robot initial tool coordinate system, and using a laser tracker to track and locate the position of the first standard target ball to complete the flange coordinate system calibration.

5. A method for repairing cracks in a turbine runner blade according to claim 1, characterized in that: In step S3, the operation steps of creating the runner crack envelope include: Use PT flaw detection on the turbine runner blades to determine the direction of the cracks, paste reflective marking points on the blades to help the visual measurement device collect runner blade crack data, and paste standard balls on the surface of the turbine runner blades to envelop the runner crack direction; A handheld scanner is used to collect point clouds of the crack area of ​​the turbine runner blade with the marker points attached and the standard sphere, and the collected marker points and standard sphere of the blade crack area are processed in the point cloud processing software.

6. A method for repairing cracks in a turbine runner blade according to claim 5, characterized in that: In step S3, when standard balls are attached to the surface of the turbine runner blade, three standard balls of different specifications are used to envelop the crack direction of the runner.

7. A method for repairing cracks in a turbine runner blade according to claim 5, characterized in that: In step S3, when processing the marker points, B-spline fitting is performed on the marker points to determine the crack direction, the B-spline fitting curve is offset along the surface normal direction, and the maximum spacing on the B-spline curve is used as the width of the envelope model to create a crack envelope surface model.

8. A method for repairing cracks in a turbine runner blade according to claim 5, characterized in that: In step S3, when processing the standard sphere, feature extraction is performed on the standard sphere to construct a plane with the extracted sphere center as the reference point, and one of the sphere centers is selected to create a workpiece coordinate system, and the constructed runner blade crack surface envelope model is converted to the workpiece coordinate system established by the standard sphere.

9. A method for repairing cracks in a turbine runner blade according to claim 1, characterized in that: In step S4, the construction of the workpiece coordinate system includes: using a visual measurement device after robot hand-eye calibration to scan the standard sphere, performing feature extraction on the scanned standard sphere point cloud data in the software to obtain the center of the standard sphere, constructing a plane for the three standard spheres obtained by the scan through the coordinate system construction method, selecting a sphere center as the origin and taking the line connecting the sphere centers as the X-axis, taking the normal line perpendicular to the plane constructed by the sphere center and passing through the origin as the Z-axis, taking the normal line perpendicular to the XOZ plane and passing through the origin as the Y-axis to create a workpiece coordinate system, and outputting the position data of the current workpiece coordinate system.

10. A method for repairing cracks in a turbine runner blade according to claim 9, characterized in that: In step S4, after the workpiece coordinate system component is completed, the transformation matrix from the workpiece coordinate system created by the standard sphere to the robot base coordinate system is solved, and the runner blade crack envelope model created in step three is spatially transformed to obtain the runner blade crack envelope model in the robot base coordinate system.

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