A method for repairing cracks in runner blades of a hydraulic turbine

Abstract

A method for repairing cracks in turbine runner blades includes the following steps: S1, designing a quick-change tooling at the end effector of a robot according to the runner crack repair process; S2, installing a vision measurement device at the end effector of the robot, and using a hand-eye calibration method to unify the vision measurement coordinate system with the robot end effector flange coordinate system; simultaneously, calibrating the robot and various end effector tools; S3, using an ultrasonic phased array to conduct depth testing on the runner crack area to determine the depth of each location of the runner crack, and constructing the runner crack envelope in trajectory planning software; simultaneously, extracting features from a standard sphere to obtain the coordinates of the sphere's center; S4, constructing a workpiece coordinate system on the center of the extracted standard sphere, generating robot machining point data in the trajectory planning software by combining the runner crack envelope model, generating a robot machining trajectory program using robot inverse kinematics and trajectory optimization strategies, and performing trajectory simulation in trajectory processing software to generate the robot machining trajectory program. This invention effectively improves the efficiency, quality, and accuracy of turbine runner crack repair, and reduces the risks of manual repair.

Description

Technical Field

[0001] This invention belongs to the technical field of robotics, and specifically relates to a method for repairing cracks in turbine runner blades. Background Technology

[0002] After long-term service, large hydroelectric generator units experience defects such as cracks and cavitation at the joint area between the blade roots and the lower ring of the turbine runner due to prolonged impact from water flow. Currently, most repair methods for these turbine defects involve manual repair. First, a flaw detection agent is manually sprayed to detect defects. Then, manual air gouging, welding, and grinding are used to clean the defective areas, fill the defects, and polish the surface to ensure consistency in the turbine's profile before and after repair.

[0003] However, manual repair methods cannot guarantee the quality and shaping effect of the wheel due to the varying skill levels of the repair personnel. Summary of the Invention

[0004] This invention provides a method for repairing cracks in turbine runner blades, in order to solve the problem of difficulty in ensuring the quality of runner defect repair.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A method for repairing cracks in turbine runner blades includes the following steps:

[0007] S1. Based on the wheel crack repair process, a quick-change tooling is designed at the end of the robot to facilitate the robot to quickly perform wheel crack repair operations by changing the end tool in different processes;

[0008] S2. Install a vision measurement device at the end of the robot and use the hand-eye calibration method to complete the conversion between the vision 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.

[0009] S3. Use an ultrasonic phased array to conduct depth testing on the cracked area of ​​the rotor to determine the depth of each location of the rotor crack, and construct the rotor crack envelope in the trajectory planning software; at the same time, extract features from the standard sphere to obtain the coordinates of the sphere center.

[0010] S4. Construct a workpiece coordinate system on the center of the standard sphere for feature extraction. In the trajectory planning software, combine the wheel crack envelope model to generate robot machining point data. Use robot inverse kinematics and trajectory optimization strategies to generate robot machining trajectory program. Perform trajectory simulation in trajectory processing software to generate robot machining trajectory program.

[0011] Furthermore, in step S2, the hand-eye calibration algorithm specifically includes: installing a vision measurement device at the end of the robot, controlling the robot to drive the vision measurement device to take pictures of the calibration board in different postures, recording the calibration board data of the robot in different postures, and the robot's posture data;

[0012] The spatial pose transformation matrix of the vision measurement device relative to the robot end flange is obtained by processing the data in the data analysis software. This matrix is ​​used to realize the spatial pose transformation between the vision measurement coordinate system and the robot flange coordinate system.

[0013] Furthermore, the robot end-effector calibration method in step S2 includes:

[0014] Multiple second standard target balls are attached to the end effector. The position information of the second standard target balls on the end effector is recorded using a laser tracker. The point cloud data of the end effector and the second standard target balls are scanned using a handheld scanner. The center position data of the second standard target balls is extracted in the data processing software. The point registration function is used in the data analysis software to convert the reverse modeling tool model to the coordinate system of the robot end effector flange.

[0015] Furthermore, before calibrating the robot end-effector in step S2, the following steps are also included: fixing a laser tracker as the origin of the reference system in an open area, fixing a first standard target ball on the robot end-effector flange, driving the robot to move in a straight line and around the space ball in the robot's initial tool coordinate system, and using the laser tracker to track and locate the position of the first standard target ball to complete the flange coordinate system calibration.

[0016] Furthermore, in step S3, the steps for creating the rotor crack envelope include:

[0017] PT flaw detection is used on turbine runner blades to determine the direction of cracks. Reflective markers are pasted on the blades to help the visual measurement device collect runner blade crack data. Standard spheres are pasted on the surface of turbine runner blades to envelop the direction of runner cracks.

[0018] A handheld scanner was used to collect point cloud data of the cracked area of ​​the turbine runner blades with affixed markers and a standard sphere. The collected markers and standard spheres in the blade cracked area were then processed in point cloud processing software.

[0019] Furthermore, in step S3, when attaching standard balls to the surface of the turbine runner blades, three standard balls of different specifications are used to envelop the direction of the runner crack.

[0020] Furthermore, in step S3, when processing the marker points, B-spline fitting is performed on the marker points to determine the crack direction. The curve fitted by the B-spline is offset along the normal direction of the surface, 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.

[0021] Furthermore, in step S3, when processing the standard sphere, feature extraction is performed on the standard sphere, and a plane is constructed using the extracted sphere center as the reference point. One of the sphere centers is selected to create a workpiece coordinate system, and the constructed turbine blade crack curved envelope model is transformed into the workpiece coordinate system established by the standard sphere.

[0022] Furthermore, in step S4, the construction of the workpiece coordinate system includes: scanning the standard sphere using a vision measurement device calibrated with the robot's hand and eye; extracting features from the scanned standard sphere point cloud data in the software to obtain the center of the standard sphere; constructing a plane for the three scanned standard spheres using a coordinate system construction method; selecting one sphere center as the origin; using the line connecting the sphere centers as the X-axis; using the normal line perpendicular to the plane constructed with the sphere centers and passing through the origin as the Z-axis; and using the normal line perpendicular to the XOZ plane and passing through the origin as the Y-axis to create the workpiece coordinate system; and outputting the current workpiece coordinate system position data.

[0023] 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 spatial position transformation of the rotor blade crack envelope model created in step three is performed to obtain the rotor blade crack envelope model in the robot base coordinate system.

[0024] The present invention can achieve the following beneficial effects:

[0025] 1. This invention uses ultrasonic phased array and 3D vision to detect and determine the crack direction and depth of the mixed-flow rotary wheel crack. A handheld scanner is used to scan the crack area of ​​the rotary wheel and then reverse model the crack envelope model. The coordinate system is completed 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.

[0026] 2. This invention designs an end-effector conversion fixture at the robot's end effector to quickly replace various repair processes and end-effector tools involved in crack repair. It replaces repetitive manual repairs in the mixed-flow rotary wheel crack repair process with robots, reducing the difficulty of on-site repair operations and ensuring consistent repair quality. Attached Figure Description

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0028] Figure 1This is a flowchart of a method for repairing cracks in turbine runner blades according to the present invention;

[0029] Figure 2 This is a schematic diagram of the crack path of the impeller blade involved in this invention;

[0030] Figure 3 A schematic diagram of the crack path of the impeller blade based on the marker point fitting of this invention;

[0031] Figure 4 This is a schematic diagram of the standard ball bonding method near the crack in the impeller blade of the present invention;

[0032] Figure 5 This is a schematic diagram illustrating the method for creating the crack envelope model of the impeller blade according to the present invention;

[0033] Figure 6 This is a schematic diagram of the workpiece coordinate system construction method of the present invention;

[0034] Figure 7 This is a schematic diagram of the process of converting the crack envelope model to the robot base coordinate system according to the present invention. Detailed Implementation

[0035] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0036] This application discloses a method for repairing cracks in turbine runner blades, referring to... Figure 1 This includes the following steps:

[0037] Step 1: Based on the turbine runner crack repair process, namely visual measurement, milling, cladding, and polishing, design the end-effector tool changer for the robot used for crack repair. Specifically, install a quick-change tooling on the end effector of the robot used to repair runner cracks. This facilitates rapid replacement of the visual measurement equipment, polishing, milling, and cladding tools. The aim is to enable the robot to quickly change end-effector tools under different processing requirements, ensuring robot motion accuracy and allowing the robot to execute processing trajectories more quickly.

[0038] The quick-change tooling is selected based on its excellent airtightness and high positioning accuracy, ensuring good repeatability after installation. To guarantee the stability and accuracy of the quick-change tooling after installation, a pneumatic locking structure is used to further clamp it, ensuring that the robot does not shake during milling.

[0039] Step 2: Use hand-eye calibration algorithms and robot end-effector calibration to complete the calibration of the robot with various end-effectors, ensuring that the planned robot processing trajectory can be accurately reached.

[0040] The main steps for calibrating the robot's end effector coordinate system are as follows:

[0041] 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 end tools for reverse modeling to create end tool models. A first standard target ball is fixed on the robot end flange, and the robot is driven to move in a straight line and in space 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.

[0042] Multiple second standard target spheres are attached to the end effector. A laser tracker is used to record the position information of these target spheres on the end effector. A handheld scanner is used to scan the point cloud data of the end effector and the target spheres. The center position data of the target spheres is extracted using data processing software. The point registration function in data analysis software is used to transform the reverse-modeled end effector model to the robot's end effector flange coordinate system. Specifically, the software constructs an end effector coordinate system based on the actual contact points of the end effector. Through spatial transformation of the software's reference coordinate system, the spatial transformation matrix of each end effector coordinate system relative to the robot's end effector flange coordinate system is obtained, thus completing the robot's end effector coordinate system calibration.

[0043] The main steps for completing robot hand-eye calibration are as follows: Install a vision measurement device on the robot's end flange, control the robot to drive the vision measurement device to take pictures of the calibration plate in different postures, record the calibration plate data and robot posture data in different postures, and process the data in the data analysis software to obtain the spatial posture transformation matrix of the vision measurement device relative to the robot's end flange.

[0044] The visual measurement coordinate system and the robot end-effector flange coordinate system are unified through a spatial pose transformation matrix. Based on the established homogeneous transformation matrix between the robot end-effector flange and the end-effector visual measurement equipment, the workpiece point cloud data in the visual measurement coordinate system is transformed to the robot base coordinate system. It should be noted that the end-effector flange coordinate system and the robot base coordinate system correspond; determining the robot base coordinate system determines the end-effector flange coordinate system.

[0045] Step 3: Use an ultrasonic phased array to conduct depth testing on the cracked area of ​​the rotor to determine the depth of each location of the rotor crack, and construct the rotor crack envelope in the trajectory planning software; at the same time, extract features from the standard sphere to obtain the coordinates of the sphere center.

[0046] The steps for creating a crack envelope in a rotating wheel include:

[0047] like Figure 2 The diagram shows the crack path of a turbine runner blade. PT (Potential Testing) is used on the turbine runner blade to determine the crack path. Figure 3 As shown, reflective markers are attached to the blades to help the vision measurement device collect data on the turbine blade cracks. After identifying the crack, as... Figure 4 As shown, three standard spheres of different sizes are attached to the surface of the turbine runner blades to envelop the direction of the runner crack, thereby reducing the amplification error caused by the coordinate system constructed by the standard spheres.

[0048] A handheld scanner was used to collect point cloud data of the cracked area of ​​the turbine runner blades with affixed markers and a standard sphere. The collected markers and standard spheres were then processed using point cloud processing software. B-spline fitting was performed on the markers to determine the crack orientation. The B-spline fitted curve was offset along the surface normal, and the width of the crack envelope model was created using the maximum spacing on the B-spline curve. For example... Figure 5 As shown, feature extraction is performed on the standard sphere, and a plane is constructed using the extracted sphere center as the reference point. One of the sphere centers is selected to create a workpiece coordinate system, and the constructed turbine blade crack curved envelope model is transformed into the workpiece coordinate system established by the standard sphere.

[0049] The ultrasonic phased array was used to detect the crack mark area of ​​the turbine blade and obtain crack depth data. The corresponding mark point data and depth data were recorded. The depth data of the area where the mark point is located was input into the point cloud processing software to construct a complete envelope model.

[0050] Step 4: Construct a workpiece coordinate system on the center of the standard sphere from feature extraction. In the trajectory planning software, combine the wheel crack envelope model to generate robot machining point data. Use robot inverse kinematics and trajectory optimization strategies to generate robot machining trajectory program. Perform trajectory simulation in trajectory processing software to generate robot machining trajectory program.

[0051] The steps of robot machining trajectory planning include:

[0052] Construction of the workpiece coordinate system in the robot base coordinate system: such as Figure 6 As shown, a visual measurement device with robot hand-eye calibration is used to scan a standard sphere. In the software, feature extraction is performed on the point cloud data of the standard sphere obtained by scanning to obtain the center of the standard sphere. A plane is constructed for the three standard spheres obtained by scanning using a coordinate system construction method. One sphere center is selected as the origin, the line connecting the centers of the spheres is used as the X-axis, the normal line perpendicular to the plane constructed by the sphere centers 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. The position data of the current workpiece coordinate system is output.

[0053] Coordinate system transformation of the envelope model: such as Figure 7 As shown, the origin coordinate system of the rotor crack envelope model created in step three is a reference coordinate system established by a standard sphere. Solve the transformation matrix from the workpiece coordinate system to the robot base coordinate system created by the standard sphere. Perform spatial position transformation on the rotor blade crack envelope model created in step three to obtain the rotor blade crack envelope model in the robot base coordinate system.

[0054] Robotic Additive / Subtractive Material Repair Machining Trajectory Planning: The spatially transformed rotor blade crack envelope model is imported into the trajectory planning software. The software then performs layered path planning on the envelope model, incorporating process parameters such as robot milling, welding, cladding, and polishing, to generate envelope machining path point data relative to the workpiece coordinate system. The robot's additive / subtractive material repair machining trajectory is planned using the robot's inverse kinematics and collision interference detection algorithm module. Trajectory motion simulation is then performed in the trajectory processing software to verify the accuracy and reliability of the generated robot machining trajectory program. After successful simulation and motion detection, the robot machining program is generated.

[0055] The robotic addition and subtraction repair process for cracked turbine runner blades using the method described in this application can achieve the required precision and efficiency for rapid robotic repair of cracked areas in turbine runner blades.

[0056] 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 within the protection scope of the present invention.

Claims

1. A method for repairing cracks in a runner blade of a hydraulic turbine, characterized in that: Includes the following steps: S1. Based on the wheel crack repair process, a quick-change tooling is designed at the end of the robot to facilitate the robot to quickly perform wheel crack repair operations by changing the end tool in different processes; S2. Install a vision measurement device at the end of the robot and use the hand-eye calibration method to complete the conversion between the vision measurement coordinate system and the robot end flange coordinate system; at the same time, complete the calibration of various end tools of the robot to ensure that the planned robot processing trajectory can be accurately reached. S3. Use an ultrasonic phased array to conduct depth testing on the cracked area of ​​the rotor to determine the depth of each location of the rotor crack, and construct the rotor crack envelope in the trajectory planning software; at the same time, extract features from the standard sphere to obtain the coordinates of the sphere center. S4. Construct a workpiece coordinate system on the center of the standard sphere for feature extraction, generate robot processing point data in trajectory planning software by combining the wheel crack envelope model, generate robot processing trajectory program by using robot inverse kinematics and trajectory optimization strategy, and perform trajectory simulation in trajectory processing software to generate robot processing trajectory program. In step S3, the steps for creating the rotor crack envelope include: PT flaw detection is used on turbine runner blades to determine the direction of cracks. Reflective markers are pasted on the blades to help the visual measurement device collect runner blade crack data. Standard spheres are pasted on the surface of turbine runner blades to envelop the direction of runner cracks. A handheld scanner was used to collect point cloud data of the cracked area of ​​the turbine runner blades with affixed markers and a standard sphere. The collected markers and standard spheres in the blade cracked area were then processed in point cloud processing software.

2. The method for repairing cracks in turbine runner blades according to claim 1, characterized in that: In step S2, the hand-eye calibration method specifically includes: installing a vision measurement device at the end of the robot, controlling the robot to drive the vision measurement device to take pictures of the calibration board in different postures, recording the calibration board data of the robot in different postures, and the robot's posture data; The spatial pose transformation matrix of the vision measurement device relative to the robot end flange is obtained by processing the data in the data analysis software. This matrix is ​​used to realize the spatial pose transformation between the vision measurement coordinate system and the robot end flange coordinate system.

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

4. The method for repairing cracks in turbine runner blades according to claim 3, characterized in that: Before calibrating the robot end-effector in step S2, the following steps are also included: fixing a laser tracker as the origin of the reference system in an open area, fixing a first standard target ball on the robot end flange, driving the robot to move in a straight line and around the end flange coordinate system, and using the laser tracker to track and locate the position of the first standard target ball to complete the end flange coordinate system calibration.

5. The method for repairing cracks in turbine runner blades according to claim 1, characterized in that: In step S3, when attaching standard balls to the surface of the turbine runner blades, three standard balls of different specifications are used to envelop the direction of the runner crack.

6. The method for repairing cracks in turbine runner blades according to claim 1, 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 curve fitted by the B-spline is offset along the normal direction of the surface. The maximum spacing on the B-spline curve is used as the width of the envelope model to create the crack envelope surface model.

7. The method for repairing cracks in turbine runner blades according to claim 1, characterized in that: In step S3, when processing the standard sphere, feature extraction is performed on the standard sphere, and a plane is constructed using the extracted sphere center as the reference point. One of the sphere centers is selected to create a workpiece coordinate system, and the constructed turbine blade crack curved envelope model is transformed into the workpiece coordinate system established by the standard sphere.

8. The method for repairing cracks in turbine runner blades according to claim 1, characterized in that: In step S4, the construction of the workpiece coordinate system includes: scanning the standard sphere using a vision measurement device after robot hand-eye calibration; extracting features from the scanned standard sphere point cloud data in the software to obtain the center of the standard sphere; constructing a plane for the three scanned standard spheres using a coordinate system construction method; selecting one sphere center as the origin; using the line connecting the sphere centers as the X-axis; using the normal line perpendicular to the plane constructed from the sphere centers and passing through the origin as the Z-axis; and using the normal line perpendicular to the XOZ plane and passing through the origin as the Y-axis to create the workpiece coordinate system; and outputting the current workpiece coordinate system position data.

9. A method for repairing cracks in turbine runner blades according to claim 8, 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 spatial position transformation of the rotor blade crack envelope model created in step S3 is performed to obtain the rotor blade crack envelope model in the robot base coordinate system.

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