Conformal self-adaptive cladding repair method based on curved surface vector outer product of runner blade of large mixed-flow water turbine

Abstract

The invention provides a large mixed-flow water turbine runner blade curved surface vector outer product-based shape follow-up self-adaptive cladding repair method, which aims at large mixed-flow water turbine runner blade curved surface shape follow-up cladding repair, generates fringes through a projection device, projects the fringes to a measured object, and shoots the bending degree of the fringes modulated by the object by using a 3D camera; and demodulating the curved fringes to obtain a phase, and converting the phase into depth to obtain 3D coordinate information of the measured object, thereby realizing blade curved surface feature imaging detection. In combination with curved surface features obtained by a 3D streak camera, obtaining 3D coordinate information of two curves intersecting at a track processing point on a curved surface, obtaining a blade contour curved surface mathematical model defined by vector expression, obtaining curves mapped in D according to a mapping relation between a parameter domain D and a curved surface domain E3, obtaining tangent vectors of the two curves, and obtaining a blade contour curved surface model; and a normal vector is obtained by an outer product of the two and is fed back to an executing mechanism for laser cladding head angle adjustment, and the laser cladding shape-following self-adaptive repairing effect is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of laser cladding, and in particular to a conformal adaptive cladding repair method based on the outer product of the surface vectors of a large-scale Francis turbine runner blade. Background Art

[0002] After a certain period of operation, large-scale mixed-flow turbine units at home and abroad will frequently develop general linear cracks or through-cracks in the runners, as well as other defects that potentially endanger normal operation. Cracks in the runners of large-scale mixed-flow turbines have become a frequent problem in the hydropower industry, posing huge hidden dangers to the operation of mixed-flow turbines and seriously threatening the safe and stable operation of the units.

[0003] At present, the surfaces of the runner blades of large-scale mixed-flow turbines and after crack removal are irregular local curved surfaces. The angle change between the surface and the laser cladding head during laser cladding stacking greatly affects the energy distribution and intensity of the laser focused spot, and the consistency and repair quality of the laser cladding process on the irregular curved surface of the blade cannot be guaranteed. Summary of the invention

[0004] The present invention provides a conformal adaptive cladding repair method based on the outer product of the surface vector of a large-scale Francis turbine runner blade, which realizes the repair processing of irregular surfaces while the laser cladding head always remains perpendicular to the processing surface or at any angle, thereby ensuring the energy distribution and intensity of the laser focus spot and the consistency and quality of the repair process, and solving the technical problems described in the background technology.

[0005] In order to realize the above technical features, the object of the present invention is achieved as follows: a conformal adaptive cladding repair method based on the outer product of the surface vector of a large-scale Francis turbine runner blade comprises the following steps: Step 1: Fix the projection device and project the line laser onto the curved surface of the large Francis turbine runner blade to be processed; Step 2: Collect and analyze the blade surface feature information of the projected surface area through a 3D streak camera; Step 3: Surface 3D coordinate information integration and data extraction; Step 4: Obtain the normal vector information at the processing point by obtaining the tangent vectors of any two curves and calculating the outer product of the two tangent vectors; Step 5: Feedback the normal vector information to the actuator to adjust the precise angle of the laser cladding head.

[0006] The step 1 specifically includes: Step 1.1: Calibrate a set of 3D coordinate systems and fix the relative position and posture of the projection device; Step 1.2: The projection device projects a line laser array onto the curved surface. The projected line laser can be represented by multiple plane equations in the 3D coordinate system. The plane equations are as shown in formula (1): (1) Where: X , Y , Z is the plane equation variable; A , B , C , D are the coefficients of the plane equation.

[0007] The step 2 specifically includes: Step 2.1: Use a camera to capture the degree of bending of the stripe line modulated by the object, demodulate the bent stripe line to obtain the phase, and then convert the phase into depth information. The camera saves the depth information through pixel points; Step 2.2: Reconstruct the ray between the optical center and the pixel by finding the corresponding pixel of the line laser in the image. The intersection of the ray and the laser plane is the three-dimensional space point to be determined. The three-dimensional space point formula (3) is obtained from the pinhole imaging model formula (2), which enables the camera to collect the 3D coordinate information of the surface feature. (2) (3) Where: x , y is the two-dimensional coordinate value of the image plane point; f The focal length of the camera.

[0008] The step 3 specifically includes: Step 3.1: Based on the surface feature information vector obtained by 3D camera analysis, define the surface contour mathematical model formula (4) in the form of vector expression; (4) Where: is a mapping from parameter domain to surface domain; D is the parameter domain; is the surface domain; Two parameter variables for parameter domain respectively; is the object surface in binary parametric coordinates; They are binary functions of the three-dimensional coordinates of the surface and the parameter domain variables; Step 3.2: During the laser cladding process, the laser cladding head moves each processing point on the corresponding surface along the trajectory, and obtains the 3D coordinate information of two curves C0 and C1 on the surface that intersect at the corresponding processing point. D For the surface domain E 3The mapping relationship of the curves C0 and C1 is obtained by mapping the curves in D. The parameter expression of C0 is expressed as formula (5). Similarly, the corresponding parameter expression of C1 is expressed as formula (6): (5) (6) Where: is the parameter expression of curve C0; is the parameter expression of curve C1; t For the curve u and v Parameter variables; The step 4 specifically includes: Step 4.1: Use formula (7) (8) to obtain the tangent vector of the two curves: (7) (8) Where: , are the tangent vectors of curve C0 and curve C1 respectively; , The intersection of the two curves is the object surface in binary parametric coordinates. u , v The guide; are the parameter domain coordinate values ​​of the intersection points of the two curves; Step 4.2: Take the outer product of the two tangent vectors to get the normal vector. The calculation formula (9) is as follows; (9) Where: is the normal vector.

[0009] Beneficial effects of the present invention: 1. The method of the present invention performs cladding processing, which effectively solves the influence of angle change on the energy distribution size of the light spot during laser cladding on the irregular curved surface path of the runner blade of a large-scale Francis turbine.

[0010] 2. The cladding process performed by the method of the present invention ensures the consistency and repair quality of the laser cladding process on the irregular curved surface of a large Francis turbine. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0012] Figure 1 It is a flow chart of the steps of the laser cladding conformal adaptive repair method according to an embodiment of the present invention.

[0013] Figure 2 It is a schematic diagram of the processing principle of an embodiment of the present invention. DETAILED DESCRIPTION

[0014] The following is combined with Figure 1 The principles and features of the present invention are described, and the embodiments are only used to explain the present invention and are not used to limit the scope of the present invention. The characteristics and features of the present invention will become clearer according to the following description and claims. It should be noted that the drawings are all in a very simplified form and are not in precise proportions, which are only used to facilitate and clearly assist in explaining the purpose of the embodiments of the present invention.

[0015] At present, the surfaces of the runner blades of large-scale mixed-flow turbines and after crack removal are irregular local curved surfaces. The angle change between the surface and the laser cladding head during laser cladding stacking greatly affects the energy distribution and intensity of the laser focused spot, and the consistency and repair quality of the laser cladding process on the irregular curved surface of the blade cannot be guaranteed.

[0016] The present invention provides a conformal adaptive cladding repair method based on the outer product of the surface vector of a large-scale Francis turbine runner blade, which realizes the repair processing of irregular surfaces while the laser cladding head always remains perpendicular to the processing surface or at any angle, thereby ensuring the energy distribution and intensity of the laser focus spot and the consistency and quality of the repair process, and solving the technical problems described in the background technology.

[0017] To achieve the above purpose, the following steps are included: Step 1: Fix the projection device and project the line laser onto the curved surface of the large Francis turbine runner blade to be processed; A set of 3D coordinate systems is calibrated, and the relative position and posture of the projection device is fixed; the projection device projects a line laser array onto the curved surface. The projected line laser can be represented by multiple plane equations in the 3D coordinate system. The plane equations are as shown in formula (1): (1) Where: X , Y , Z is the plane equation variable; A , B , C , D are the coefficients of the plane equation.

[0018] Step 2: The 3D streak camera collects and analyzes the surface feature information of the projected surface area: The camera is used to capture the degree of bending of the stripe line modulated by the object, and the phase is obtained by demodulating the bent stripe line. The phase is then converted into depth information, and the camera saves the depth information through pixel points. By finding the corresponding pixel of the line laser in the image, the ray between the optical center and the pixel is reconstructed. The intersection of the ray and the laser plane is the desired three-dimensional space point. The three-dimensional space point formula (3) can be obtained from the pinhole imaging model formula (2), which enables the camera to collect 3D coordinate information of surface features; (2) (3) Where: x , y is the two-dimensional coordinate value of the image plane point; f The focal length of the camera.

[0019] Step 3: Surface 3D coordinate information integration and data extraction; Based on the surface feature information vector obtained by 3D camera analysis, the surface contour mathematical model formula (4) is defined in a vector expression; (4) Where: is a mapping from parameter domain to surface domain; D is the parameter domain; is the surface domain; Two parameter variables for parameter domain respectively; is the object surface in binary parametric coordinates; They are binary functions of the three-dimensional coordinates of the surface and the parameter domain variables; During the laser cladding process, the laser cladding head moves along the trajectory to each processing point on the corresponding surface. By obtaining the 3D coordinate information of two curves (denoted as C0 and C1) intersecting at the corresponding processing point on the surface, the surface domain E is calibrated according to the parameter domain D. 3 The mapping relationship of the curves C0 and C1 is obtained by mapping the curves in D. The parameter expression of C0 is expressed as formula (5). Similarly, the corresponding parameter expression of C1 is expressed as formula (6): (5) (6) Where: is the parameter expression of curve C0; is the parameter expression of curve C1; t are the parameter variables of u and v on the curve; Step 4: Obtain the normal vector information at the processing point by finding the tangent vectors of any two curves and calculating the outer product of the two tangent vectors. By using formulas (7) and (8), we can obtain the tangent vectors of the two curves: (7) (8) Where: , are the tangent vectors of curve C0 and curve C1 respectively; , The derivatives of the intersection of the two curves with respect to u and v on the object surface in binary parametric coordinates respectively; are the parameter domain coordinate values ​​of the intersection points of the two curves; The outer product of the two tangent vectors is used to obtain the normal vector. The calculation formula (9) is as follows: (9) Where: is the normal vector.

[0020] Step 5: Feedback the normal vector information to the actuator to adjust the precise angle of the laser cladding head.

[0021] In summary, the principles of the present invention are: The present invention relates to a conformal adaptive cladding repair method based on the outer product of the curved surface vector of a large Francis turbine runner blade; for the conformal cladding repair of the curved surface of a large Francis turbine runner blade, a projection device is used to generate stripes and project them onto the object to be measured, a 3D camera is used to shoot the bending degree of the stripes modulated by the object, the curved stripes are demodulated to obtain the phase, and then the phase is converted into the depth to obtain the 3D coordinate information of the object to be measured, so as to realize the imaging detection of the blade surface features. Combined with the surface features obtained by the 3D stripe camera, the 3D coordinate information of two curves (recorded as C0 and C1) intersecting at the trajectory processing point on the surface is obtained, and the mathematical model of the blade contour surface defined by the vector expression is obtained. According to the mapping relationship between the parameter domain D and the surface domain E3, the curves mapped in D of the two curves are obtained, and the tangent vectors of the two curves are obtained. The normal vector is obtained by the outer product of the two curves and then fed back to the actuator for adjusting the angle of the laser cladding head, so as to realize the conformal adaptive repair effect of laser cladding. The effect of angle change on the energy distribution of the light spot during laser cladding on the curved surface of large Francis turbine runner blades is effectively solved, ensuring the process consistency of laser cladding on the curved surface processing of large Francis turbine runner blades.

Claims

1. A conformal adaptive cladding repair method based on the outer product of the surface vector of a large Francis turbine runner blade, characterized in that: The following steps are involved: Step 1: Fix the projection device and project the line laser onto the curved surface of the large Francis turbine runner blade to be processed; Step 2: Collect and analyze the blade surface feature information of the projected surface area through a 3D streak camera; Step 3: Surface 3D coordinate information integration and data extraction; Step 4: Obtain the normal vector information at the processing point by obtaining the tangent vectors of any two curves and calculating the outer product of the two tangent vectors; Step 5: Feedback the normal vector information to the actuator to adjust the precise angle of the laser cladding head.

2. According to claim 1, a conformal adaptive cladding repair method based on the outer product of the surface vector of a large Francis turbine runner blade is characterized in that: The step 1 specifically includes: Step 1.1: Calibrate a set of 3D coordinate systems and fix the relative position and posture of the projection device; Step 1.2: The projection device projects a line laser array onto the curved surface. The projected line laser can be represented by multiple plane equations in the 3D coordinate system. The plane equations are as shown in formula (1): （1） Where: X , Y , Z is the plane equation variable; A , B , C , D are the coefficients of the plane equation.

3. According to claim 1, a conformal adaptive cladding repair method based on the outer product of the surface vector of a large Francis turbine runner blade is characterized in that: The step 2 specifically includes: Step 2.1: Use a camera to capture the degree of bending of the stripe line modulated by the object, demodulate the bent stripe line to obtain the phase, and then convert the phase into depth information. The camera saves the depth information through pixel points; Step 2.2: Reconstruct the ray between the optical center and the pixel by finding the corresponding pixel of the line laser in the image. The intersection of the ray and the laser plane is the three-dimensional space point to be determined. The three-dimensional space point formula (3) is obtained from the pinhole imaging model formula (2), which enables the camera to collect the 3D coordinate information of the surface feature. （2） （3） Where: x , y is the two-dimensional coordinate value of the image plane point; f The focal length of the camera.

4. According to claim 1, a conformal adaptive cladding repair method based on the outer product of the surface vector of a large Francis turbine runner blade is characterized in that: The step 3 specifically includes: Step 3.1: Based on the surface feature information vector obtained by 3D camera analysis, define the surface contour mathematical model formula (4) in the form of vector expression; （4） Where: is a mapping from parameter domain to surface domain; D is the parameter domain; is the surface domain; Two parameter variables for parameter domain respectively; is the object surface in binary parametric coordinates; They are binary functions of the three-dimensional coordinates of the surface and the parameter domain variables; Step 3.2: During the laser cladding process, the laser cladding head moves each processing point on the corresponding surface along the trajectory, and obtains the 3D coordinate information of two curves C0 and C1 on the surface that intersect at the corresponding processing point. D For the surface domain E 3 The mapping relationship of the curves C0 and C1 is obtained by mapping the curves in D. The parameter expression of C0 is expressed as formula (5). Similarly, the corresponding parameter expression of C1 is expressed as formula (6): （5） （6） Where: is the parameter expression of curve C0; is the parameter expression of curve C1; t For the curve u and v Parameter variables.

5. According to claim 1, a conformal adaptive cladding repair method based on the outer product of the surface vector of a large Francis turbine runner blade is characterized in that: The step 4 specifically includes: Step 4.1: Use formula (7) (8) to obtain the tangent vector of the two curves: （7） （8） Where: , are the tangent vectors of curve C0 and curve C1 respectively; , The intersection of the two curves is the object surface in binary parametric coordinates. u , v The guide; are the parameter domain coordinate values ​​of the intersection points of the two curves; Step 4.2: Take the outer product of the two tangent vectors to get the normal vector. The calculation formula (9) is as follows; （9） Where: is the normal vector.

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