A method, system, device and medium for adaptive repair of free-form surface

Abstract

The present invention belongs to the field of surface repair technology, and discloses a method, system, equipment and medium for adaptive repair of free-form surfaces, including: discretizing the data of a worn workpiece to obtain a worn body to be repaired; adaptive segmentation to obtain an initial reference surface; wherein the initial reference surface includes a bottom surface of a wear model and a top surface of a standard model; constructing free-form surface slices based on the initial reference surface; calculating the surface curvature distribution data of the free-form surface slices, constructing a curvature-overlap spacing optimization model to adaptively fill the trajectory of the free-form surface slices to obtain a free-form surface scanning trajectory; topologically sorting the scanning trajectory points in the free-form surface scanning trajectory to obtain a processing trajectory, fitting the processing trajectory, and completing the adaptive repair of the free-form surface. The technical solution of the present invention eliminates the serious "staircase effect" existing in the traditional slicing method, and ensures the processing quality and efficiency of robot laser repair.

Description

Technical Field

[0001] The present invention belongs to the technical field of surface repair, and in particular relates to a self-adaptive repair method, system, equipment and medium for a free-form surface. Background Art

[0002] Free-form surfaces have smooth shapes and good aerodynamic properties, and are widely used as special functional surfaces in a variety of industries, such as the aerospace industry, the automotive industry, and the mold manufacturing industry. Such core functional components, such as turbine blades, engine crankshafts, and cold stamping dies, usually work in harsh environments with high temperature, high pressure, overload, high impact, vibration, and fatigue. They are prone to wear after long-term service, resulting in performance degradation or even scrapping of core equipment. Since the manufacture of such parts often requires the use of special engineering materials and relatively complex processing techniques, compared to remanufacturing new workpieces, remanufacturing the faulty parts to restore their functions and performance is energy-saving, material-saving, time-saving, economical, and environmentally friendly.

[0003] Since free-form surface parts are more complex than traditional plane and rotational body surfaces, there are many difficulties in their adaptive repair. On the one hand, traditional surface repair often adopts plane slicing. This method realizes the repair of defective bodies in the form of plane stacking. Its slicing method and trajectory filling method are relatively simple and widely used in the repair of traditional plane parts. However, the surface morphology of free-form surfaces is relatively complex. The traditional plane slicing method cannot achieve full conformal fusion with the free-form surface substrate. In addition, there is a serious "staircase effect". The continuity of layered slicing is poor, and small fragments of trajectories are prone to appear. There are serious deficiencies in repair quality and repair efficiency, and it is difficult to meet the requirements of free-form surface repair. On the other hand, the traditional repair trajectory filling method usually uses a fixed overlap spacing. This method is suitable for trajectory planning for surface repair of plane-type workpieces. However, the curvature of the free-form surface changes dynamically. The traditional fixed overlap spacing method will lead to serious problems of uneven thickness of the repair layer, which is specifically manifested as a thinner thickness of the cladding layer for convex cladding and a thicker thickness of the cladding layer for concave cladding, which will greatly reduce the surface quality and processing accuracy of the repair process.

[0004] Among the existing methods, a 3D printing path planning method and system based on free-form surface slicing is proposed. This method takes into account the problems of surface path planning technology, such as deformation of the surface model due to gravity extrusion, obvious deformation of the structure due to the lack of solidification of the material bundle, and low printing accuracy. However, the slicing method of fixed-direction equidistant offset adopted by this invention cannot adapt to the free-form surface wear repair scenario. When slicing the free-form surface wear defect entity, the final top surface still has a serious "staircase effect". On the one hand, the surface quality and accuracy of the top surface are poor, which cannot meet the requirements for the final repair top surface surface waviness in the free-form surface repair scenario. On the other hand, the large number of small fragment slicing trajectories will greatly reduce the work efficiency of the repair process.

[0005] In summary, facing the requirements of low waviness and high processing efficiency for the repaired surface in free-form surface repair scenarios, there is currently no good method for adaptive surface slicing and trajectory planning for laser repair. Summary of the invention

[0006] The purpose of the present invention is to provide a method, system, device and medium for adaptively repairing free-form surfaces to solve the problems existing in the above-mentioned prior art.

[0007] To achieve the above object, the present invention provides a method for adaptively repairing a free-form surface, comprising:

[0008] Step 1: discretize the data of the worn workpiece to obtain a worn body to be restored; adaptively segment the worn body to be restored to obtain an initial reference surface; wherein the initial reference surface includes the bottom surface of the worn model and the top surface of the standard model;

[0009] Step 2: constructing free-form surface slices based on the initial reference surface;

[0010] Step 3: Calculate the surface curvature distribution data of the free-form surface slice, construct a curvature-overlapping distance optimization model to perform trajectory adaptive filling on the free-form surface slice, and obtain a free-form surface scanning trajectory;

[0011] Step 4: topologically sorting the scanning trajectory points in the free-form surface scanning trajectory to obtain a processing trajectory, fitting the processing trajectory, and completing the adaptive repair of the free-form surface.

[0012] Optionally, the step 1 specifically includes:

[0013] Discretizing the data of the standard workpiece and the worn workpiece respectively to obtain a standard point cloud model and a worn object to be restored, and iteratively obtaining the gap value between the worn object to be restored and the standard point cloud model point by point;

[0014] The worn object to be restored is adaptively segmented based on the gap value to obtain an initial reference surface.

[0015] Optionally, the step 2 specifically includes:

[0016] The normal vector of each discrete point in the initial reference surface is calculated, a tangent sphere model corresponding to the discrete point is constructed based on each normal vector, and an envelope surface tangent to each tangent sphere model is constructed as a free surface slice.

[0017] Optionally, the step three specifically includes:

[0018] Constructing a curvature-overlap spacing optimization model based on the surface curvature distribution data according to an equal volume overlap model;

[0019] Setting an initial trajectory plane and a distance threshold, obtaining distance data from each discrete point in the free-form surface slice to the initial trajectory plane, judging the distance data of each discrete point based on the distance threshold, saving discrete points corresponding to distance data less than the distance threshold, and constructing an initial scanning trajectory based on the saved discrete points;

[0020] Iteratively calculating the overlap spacing optimization points corresponding to each point on the initial scanning trajectory, and generating adjacent overlap trajectories based on the overlap spacing optimization points;

[0021] The free-form surface slices are adaptively filled based on the adjacent overlapping trajectories to obtain a free-form surface scanning trajectory.

[0022] Optionally, the step 4 specifically includes:

[0023] The scanning trajectory points in the free-form surface scanning trajectory are topologically sorted, and the topologically sorted scanning trajectory points are used as processing points. Based on the processing points, safety points are inserted between different free-form surface scanning trajectories to obtain a processing trajectory. The processing trajectory is fitted based on the NURBS curve to complete the adaptive repair of the free-form surface.

[0024] An adaptive repair system for a free-form surface, comprising:

[0025] The module for constructing the object to be restored is used to discretize the data of the worn workpiece to obtain the worn object to be restored; adaptively segment the worn object to be restored to obtain an initial reference surface; wherein the initial reference surface includes the bottom surface of the worn model and the top surface of the standard model;

[0026] A trajectory adaptive filling module is used to construct a free-form surface slice according to the initial reference surface, calculate the surface curvature distribution data of the free-form surface slice, and construct a curvature-overlap spacing optimization model to perform trajectory adaptive filling on the free-form surface slice to obtain a free-form surface scanning trajectory;

[0027] The fitting module is used to topologically sort the scanning trajectory points in the free-form surface scanning trajectory to obtain a processing trajectory, fit the processing trajectory, and complete the adaptive repair of the free-form surface.

[0028] An electronic device comprises a memory and a processor, wherein the memory is used to store a computer program, and the processor runs the computer program to enable the electronic device to execute the self-adaptive repair method for a free-form surface.

[0029] A computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method for adaptively repairing a free-form surface is implemented.

[0030] The technical effects of the present invention are:

[0031] The present invention aims at the problem that the traditional plane slicing method has insufficient repair processing quality and efficiency in the free-form surface repair scenario. By performing surface decomposition on the wear body to be repaired, the wear body is decomposed into the bottom surface of the wear model and the top surface of the standard model. In order to ensure that the laser cladding layer is fully integrated with the bottom surface of the wear body, and at the same time to ensure the continuity and forming accuracy of the cladding layer, the bottom surface of the wear model and the top surface of the standard model are used as the initial reference surfaces, and the surface normal vector distribution of the free-form surface point cloud is calculated point by point, and a tangent sphere model of a given layer thickness is established, and then the envelope surface of the tangent sphere is obtained, and the generation of normal equidistant surfaces is realized. The normal equidistant surface generation method is repeatedly iterated to perform layer-by-layer adaptive surface slicing on the target body to be repaired. Furthermore, in order to ensure the uniformity of the cladding layer thickness and the final forming accuracy, considering the problem of uneven thickness in different curvature parts of the traditional fixed-spacing trajectory filling method, the optimal overlap spacing-curvature model is established by calculating the surface curvature distribution of the surface slice, and the overlap spacing is dynamically optimized to obtain the adjacent overlap trajectories of the initial scanning trajectory. By repeatedly iterating the above method, the growth of the free-form surface slice trajectory from the center to both sides is achieved, and finally the scanning trajectory of the free-form surface slice is completely filled. Furthermore, according to the needs of the robot laser cladding process, the generated free-form surface scanning trajectory is topologically sorted, and safety points are inserted between adjacent scanning trajectories. The processed discrete trajectory points are fitted with NURBS curves, and then the robot is driven to perform layered laser cladding deposition on the target free-form surface wear body to complete the adaptive repair of free-form surface wear.

[0032] The present invention decomposes the wear body and slices the free-form surface with equal spacing in the normal direction based on the decomposition result, so as to achieve a smooth transition from the wear base of the wear part to the target repair surface, ensure the full fusion of the cladding layer and the wear base surface, and at the same time, ensure the continuity of the cladding layer to the greatest extent, eliminate the serious "staircase effect" existing in the traditional slicing method, and ensure the processing quality and efficiency of the robot laser repair. At the same time, in view of the problem of uneven thickness of the repair layer in different curvature parts of the traditional equal-spacing overlap track, a method for optimizing the overlap spacing based on the equal-volume model is proposed. By dynamically optimizing the overlap spacing to adapt to the curvature change of the free-form surface, the thickness uniformity of the cladding layer is guaranteed to the greatest extent, and the processing accuracy of the laser repair surface is further guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0035] Figure 1 is a flow chart of adaptive repair in an embodiment of the present invention;

[0036] Figure 2 Schematic diagram of adaptive surface slicing strategy for worn solids in an embodiment of the present invention;

[0037] Figure 3 Schematic diagram of a method for generating an equidistant surface in an embodiment of the present invention;

[0038] Figure 4 Schematic diagram of overlapping effects of different curvatures in an embodiment of the present invention; wherein, Figure 4 (a) is a schematic diagram of the plane overlap effect in an embodiment of the present invention; Figure 4 (b) is a schematic diagram of the concave overlap effect in an embodiment of the present invention; Figure 4 (c) is a schematic diagram of the convex surface overlap effect in an embodiment of the present invention;

[0039] Figure 5 A schematic diagram of a curved track filling method with optimized overlap spacing in an embodiment of the present invention; Figure 5 (a) is a schematic diagram of obtaining the initial scanning trajectory in an embodiment of the present invention; Figure 5(b) is a schematic diagram of generating track points for optimizing the overlap spacing in an embodiment of the present invention; Figure 5 (c) is a schematic diagram of generating adjacent scanning trajectories in an embodiment of the present invention; Figure 5 (d) is a schematic diagram of free-form surface filling in an embodiment of the present invention;

[0040] Figure 6 A diagram showing a process of adaptive surface slicing of a blade wear body in an embodiment of the present invention;

[0041] Figure 7 This is a result diagram of adaptive surface slicing of a blade wear body in an embodiment of the present invention;

[0042] Figure 8 A diagram of a process of generating adjacent scanning trajectories in an embodiment of the present invention; Figure 8 (a) is a schematic diagram of curvature calculation in an embodiment of the present invention; Figure 8 (b) is a schematic diagram of generating track points for optimizing the overlap spacing in an embodiment of the present invention; Figure 8 (c) is a schematic diagram of generating adjacent scanning trajectories in an embodiment of the present invention;

[0043] Fig. 9 It is a result diagram of blade surface slice trajectory filling in the embodiment of the present invention; wherein, Fig. 9 (a) is a graph showing the trajectory filling result of the curved surface slice 1 in an embodiment of the present invention; Fig. 9 (b) is a graph showing the trajectory filling result of the curved surface slice 2 in an embodiment of the present invention; Fig. 9 (c) is a graph showing the trajectory filling result of the curved surface slice 3 in an embodiment of the present invention; Fig. 9 (d) is a graph showing the trajectory filling result of the curved surface slice 4 in an embodiment of the present invention; Fig. 9 (e) is a graph showing the trajectory filling result of the curved surface slice 5 in an embodiment of the present invention; Fig. 9 (f) is a graph showing the trajectory filling result of the curved surface slice 6 in an embodiment of the present invention;

[0044] Fig.10 It is a result diagram of the command position and feedback position of the blade repair experiment robot in the embodiment of the present invention; wherein, Fig.10 (a) is a diagram showing the command position and feedback position result of the robot for the cladding layer 1 in an embodiment of the present invention; Fig.10 (b) is a diagram showing the command position and feedback position result of the cladding layer 2 robot in an embodiment of the present invention; Fig.10 (c) is a diagram showing the command position and feedback position result of the cladding layer 3 robot in an embodiment of the present invention; Fig.10 (d) is a diagram showing the command position and feedback position result of the cladding layer 4 robot in an embodiment of the present invention; Fig.10(e) is a diagram showing the command position and feedback position result of the cladding layer 5 robot in an embodiment of the present invention; Fig.10 (f) is a diagram showing the command position and feedback position result of the cladding layer 6 robot in an embodiment of the present invention;

[0045] Fig.11 This is a graph showing the time consumption results of a blade repair experiment in an embodiment of the present invention. DETAILED DESCRIPTION

[0046] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0047] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0048] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those of ordinary skill in the art generally understood by the present invention. Although the present invention describes only preferred methods, any method similar or equivalent to that described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods related to the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0049] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present application description and examples are exemplary only.

[0050] The words “include,” “including,” “have,” “contain,” etc. used in this article are open-ended terms, meaning including but not limited to.

[0051] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0052] Embodiment 1

[0053] like Figure 1 - Fig.11As shown, this embodiment provides an adaptive repair method for a free-form surface, including: discretizing data of a worn workpiece to obtain a worn body to be repaired; adaptively segmenting the worn body to be repaired to obtain an initial reference surface; wherein the initial reference surface includes a bottom surface of a worn model and a top surface of a standard model; constructing free-form surface slices based on the initial reference surface; calculating surface curvature distribution data of the free-form surface slices, constructing a curvature-overlap spacing optimization model to adaptively fill the trajectory of the free-form surface slices to obtain a free-form surface scanning trajectory; topologically sorting the scanning trajectory points in the free-form surface scanning trajectory to obtain a processing trajectory, fitting the processing trajectory, and completing the adaptive repair of the free-form surface.

[0054] In view of the problem that the traditional plane slicing method has insufficient repair processing quality and efficiency in the free-form surface repair scenario, this embodiment decomposes the wear body to be repaired into the bottom surface of the wear model and the top surface of the standard model by performing surface decomposition on the wear body to be repaired. In order to ensure that the laser cladding layer is fully integrated with the bottom surface of the wear body, and at the same time to ensure the continuity and forming accuracy of the cladding layer, the bottom surface of the wear model and the top surface of the standard model are used as the initial reference surfaces, and a normal equidistant surface generation method based on three-dimensional point clouds is proposed. By calculating the surface normal vector distribution of the free-form surface point cloud point cloud point by point, a tangent sphere model of a given layer thickness is established, and then the envelope surface of the tangent sphere is obtained to achieve the generation of normal equidistant surfaces. The normal equidistant surface generation method is repeatedly iterated to perform layer-by-layer adaptive surface slicing on the target body to be repaired. Furthermore, in order to ensure the uniformity of the thickness of the cladding layer and the final forming accuracy, considering that the traditional fixed-spacing trajectory filling method has the problem of uneven thickness at different curvature locations, a free-form surface trajectory generation method with optimized overlap spacing is proposed. By calculating the surface curvature distribution of the surface slice, the optimal overlap spacing-curvature model is established, and the overlap spacing is dynamically optimized to obtain the adjacent overlap tracks of the initial scanning track. By repeatedly iterating the above method, the growth of the free-form surface slice track from the center to the sides is achieved, and finally the scanning track of the free-form surface slice is completely filled. Furthermore, according to the needs of the robot laser cladding process, the generated free-form surface scanning track is topologically sorted, and safety points are inserted between adjacent scanning tracks. The processed discrete track points are fitted with NURBS curves, and then the robot is driven to perform layered laser cladding deposition on the target free-form surface wear body to complete the adaptive repair of free-form surface wear.

[0055] Step 1: Reverse modeling of the worn part is performed, followed by wear analysis, to obtain the worn part to be repaired.

[0056] Step 2: Decompose the worn body to be restored into the bottom surface of the worn model and the top surface of the standard model. Based on the discrete point cloud data, calculate the normal distribution of the bottom surface of the worn model and the top surface of the standard model respectively, and obtain the normal equidistant surface by establishing a tangent sphere model. Then, with the generated normal equidistant surface as a reference, repeatedly iterate the above method to achieve layer-by-layer adaptive surface slicing of the worn body from the outside to the inside.

[0057] Step 3: Based on each surface slice of the wear body, by calculating the curvature distribution of the slice surface, according to the equal volume overlap model, a curvature-overlap spacing optimization model is established. Then, with the initial scanning trajectory as a reference, the overlap spacing optimization points corresponding to each point on the initial scanning trajectory are iteratively calculated to achieve the generation of adjacent scanning trajectories. Then, with the generated adjacent scanning trajectory as a reference, the above method is repeatedly iterated to achieve the growth of the surface slice scanning trajectory from the center to the surroundings, and finally complete the adaptive filling of the free surface slice with overlap optimization.

[0058] Step 4: According to the processing requirements, the generated free-form surface filling trajectory is topologically sorted, and then the discrete points on the sorted processing trajectory are used as working points, and safety points are inserted between adjacent scanning trajectories. The acquired processing trajectory is fitted with a NURBS curve. At the same time, according to the different types of working points and safety points on the processing trajectory, the laser working state is synchronously triggered to achieve coordinated control of robot movement and laser repair processing technology.

[0059] The present embodiment relates to a system for implementing the above method, including: a wear analysis module, an adaptive surface slicing module, a free-form surface scanning trajectory filling module, and a trajectory post-processing module. Among them, the wear analysis module performs wear measurement on the target worn workpiece and generates a model of the worn body to be repaired. The adaptive surface slicing module decomposes the worn body to be repaired, and then calculates the normal vector distribution of the decomposed surface, and realizes the generation of normal equidistant surfaces by establishing a tangent sphere model, and finally iterates to complete the adaptive surface slicing of the worn body to be repaired. The free-form surface scanning trajectory filling module calculates the surface curvature of the surface slice, establishes an isovolumetric curvature-lap joint model, iterates the given initial scanning trajectory, obtains the overlap spacing optimization point of the initial trajectory point, realizes the generation of adjacent optimized overlap joint trajectories, and finally iterates to complete the scanning trajectory filling of the free-form surface slice. The trajectory post-processing module topologically sorts the scanning trajectory of the free-form surface slice, and the discrete points on the sorted scanning trajectory are working points, and the safety points are inserted between adjacent trajectories. The final trajectory is fitted with a NURBS curve, the robot movement and process control are controlled, and the free-form surface wear adaptive repair processing is completed.

[0060] This embodiment solves the problem of severely low repair processing quality and efficiency caused by the "step effect" of the traditional plane slicing method in the free-form surface wear repair scenario. It also solves the problem of poor surface adaptability of traditional equally spaced overlapping tracks and uneven thickness of the repair layer in parts with different curvatures. It realizes adaptive repair of free-form surface wear and improves the surface quality and processing efficiency of the repair process.

[0061] Compared with the prior art, this embodiment decomposes the wear body and slices the free-form surface with equal spacing in the normal direction based on the decomposition result, so as to achieve a smooth transition from the wear base of the wear part to the target repair surface, ensure the full fusion of the cladding layer and the wear base surface, and at the same time, ensure the continuity of the cladding layer to the greatest extent, eliminate the serious "staircase effect" existing in the traditional slicing method, and ensure the processing quality and efficiency of the robot laser repair. At the same time, in view of the problem of uneven thickness of the repair layer in different curvature parts of the traditional equal-spacing overlap track, a method for optimizing the overlap spacing based on the equal-volume model is proposed. By dynamically optimizing the overlap spacing to adapt to the curvature change of the free-form surface, the thickness uniformity of the cladding layer is guaranteed to the greatest extent, and the processing accuracy of the laser repair surface is further guaranteed.

[0062] Aiming at the problems of adaptive surface slicing and spatial trajectory planning in free-form surface repair scenarios, an adaptive surface slicing and trajectory planning method for free-form surface robot laser repair is proposed. Figure 1As shown in the figure, the wear of the free-form surface workpiece is first measured and analyzed to obtain accurate workpiece wear quantification and positioning data. The wear body to be repaired is further decomposed into the bottom surface of the wear model and the top surface of the standard model by performing surface decomposition on the wear body to be repaired. In order to ensure that the laser cladding layer is fully integrated with the bottom surface of the wear body, and to ensure the continuity and forming accuracy of the cladding layer, the bottom surface of the wear model and the top surface of the standard model are used as the initial reference surfaces, respectively. A normal equidistant surface generation method based on three-dimensional point cloud is proposed. By calculating the surface normal vector distribution of the free-form surface point cloud point cloud point by point, a tangent sphere model of a given layer thickness is established, and then the envelope surface of the tangent sphere is obtained to achieve the generation of normal equidistant surfaces. The normal equidistant surface generation method is repeatedly iterated to perform layer-by-layer adaptive surface slicing on the target body to be repaired. Furthermore, in order to ensure the uniformity of the thickness of the cladding layer and the final forming accuracy, considering that the traditional fixed-spacing trajectory filling method has the problem of uneven thickness at different curvature parts, a free-form surface trajectory generation method with optimized overlap spacing is proposed. By calculating the surface curvature distribution of the surface slice, the optimal overlap spacing-curvature model is established, and the overlap spacing is dynamically optimized to obtain the adjacent overlap tracks of the initial scanning track. By repeatedly iterating the above method, the growth of the free-form surface slice track from the center to the sides is achieved, and finally the scanning track of the free-form surface slice is completely filled. Furthermore, according to the needs of the robot laser cladding process, the generated free-form surface scanning track is topologically sorted, and safety points are inserted between adjacent scanning tracks. The processed discrete track points are fitted with NURBS curves, and then the robot is driven to perform layered laser cladding deposition on the target free-form surface wear body to complete the adaptive repair of free-form surface wear.

[0063] The specific steps of the wear analysis described in step 1 are: error , respectively discretize the data of the actual worn workpiece model and the original standard workpiece model to obtain a detailed point cloud model, and then iterate point by point to find the difference between the actual model and the original standard model. The difference value d is the wear amount. By iteratively calculating the wear amount of all points on the model, specific information on error quantification and positioning can be obtained, providing the worn object D to be repaired for later repair trajectory planning.

[0064] The specific steps of the adaptive surface slicing in step 2 are as follows: according to the worn body D to be restored obtained in step 1, Figure 2 As shown in the figure, according to the distance relationship between each discrete point on the worn object and the surface of the worn workpiece model and the surface of the original standard workpiece model, the worn object to be restored can be adaptively segmented into two point cloud surfaces: the bottom surface P of the worn model d and the standard model top surface Q d .

[0065] The generation of traditional equidistant surfaces usually uses a fixed direction translation method. Since the curvature of the free-form surface is variable, the traditional method has the defect of uneven distribution of local normal thickness, which seriously affects the processing accuracy of layered cladding. Therefore, this embodiment proposes a method for generating surfaces with equidistant normals, which strictly guarantees the uniformity of the interlayer spacing of the slices. By calculating the local normal distribution of the free-form surface, a tangent sphere of a given thickness is established point by point. The tangent sphere envelope surface is fitted to achieve the generation of surfaces with equidistant local normals, which overcomes the uneven thickness problem of the traditional fixed direction translation method and provides a guarantee for the thickness control of the laser repair layer.

[0066] The wear model bottom surface P is obtained by decomposing the above model d and the standard model top surface Q d As the reference surface, R neighbor Select the current reference point p for the adjacent radius i The adjacent point set {N i}, calculate the adjacent point set {N i The covariance matrix E(N i ), as follows:

[0067]

[0068] Among them, p j =(x j ,y j ,z j )∈{N i};

[0069]

[0070] By the covariance matrix EN i Perform eigenvalue SVD decomposition to obtain the covariance matrix EN i The eigenvector corresponding to the minimum eigenvalue of is normalized to the normal vector v at the point. i , from which the distribution of the reference surface normal vector can be obtained.

[0071] Further, taking the current discrete point p i is the reference point, based on the calculated normal vector v i , with a given cladding thickness h as the diameter, make a tangent sphere g of the reference surface i ,like Figure 3 Traverse all discrete points on the reference surface U to obtain the tangent sphere envelope surface, which is the equidistant surface of a given thickness.

[0072] Furthermore, the bottom surface P of the wear model is d and the standard model top surface Q dAs the reference surface, the above isometric surface generation method is iterated until the final generated model bottom isometric surface And the generated standard model top surface isometric surface The maximum distance between them is less than the given cladding thickness h, and the wear model bottom surface generation group can be obtained. and the standard model top surface generation group According to the principle of from outside to inside and from bottom to top, the order of cladding layers is rearranged as the processing strategy for adaptive defect repair of free-form surfaces, that is, arrive Figure 2 shown.

[0073] The specific steps of filling the free-form surface scanning trajectory described in step 3 are: based on the free-form surface slices obtained above, the curvature distribution of the surface slice point cloud is obtained using the quadratic surface fitting method. Similarly, with the current reference point p i is the center of the sphere, R neighbor Select the current reference point p for the adjacent radius i The adjacent point set {N i}, and then use the least squares method to fit the current adjacent point set N i Perform quadratic surface fitting.

[0074] To simplify the calculation process, we may assume that the parametric equation of the fitted quadratic surface is

[0075]

[0076] Then the current adjacent point set N i (x i ,y i ,z i ) can be expressed as:

[0077]

[0078] Among them, p j =(x j ,y j ,z j )∈{N i}, take Q i 2 The minimum point of , that is, calculate the following system of partial differential equations:

[0079]

[0080] You can get the current adjacent point set N i The fitting quadratic surface parameters a, b, c.

[0081] Furthermore, based on the fitted quadratic surface parameters, the Gaussian curvature at the current point is calculated.

[0082] Assume that there is a curve r on the surface, which can be expressed parametrically as:

[0083] r=rxt,y(t)

[0084] From the arc length differential formula, we know that

[0085]

[0086] Furthermore, the unit normal vector n of the curve is expressed as:

[0087]

[0088] Further, by performing a second differentiation on the above formula, we can obtain:

[0089]

[0090] Further, the current reference point p can be calculated i The Gaussian curvature at is:

[0091]

[0092] By traversing all points on the free-form surface slice, the curvature distribution of the slice surface can be obtained.

[0093] Since the surface curvature of the free-form surface cladding layer changes dynamically, according to the equivalent volume assumption of laser cladding multi-pass overlap, the traditional fixed spacing will cause the problem of uneven cladding layer thickness when filling free-form surface slices, specifically, the cladding layer thickness of the convex surface cladding is thinner, and the cladding layer thickness of the concave surface cladding is thicker. In order to solve the effect of curvature change on the cladding layer thickness during the free-form surface multi-pass filling process. This embodiment proposes a free-form surface slice trajectory filling method with optimized spacing, such as Fig. 9 As shown in the figure, based on the equivalent volume assumption of multiple overlaps, a model of local curvature and overlap spacing is established. By dynamically optimizing the overlap spacing, the volume of multiple valleys at different curvature locations is ensured to be equal to the overlapping volume, so as to reduce the waviness of the cladding layer surface.

[0094] According to the equal volume assumption, when the volume of multiple valleys is equal to the overlapping volume, the waviness of the cladding surface is the smallest, that is:

[0095]

[0096] Among them, P a is the intersection of the single-pass cladding profile f1x1, y1 = 0 and the top profile of the multi-pass cladding layer f3x3, y3 = 0; P bIt is the intersection of the single-pass cladding profile f1x1, y1 = 0 and the cladding substrate surface profile f2x2, y2 = 0, which can be calculated by the following formula:

[0097]

[0098] Where ρ is the current reference point p i The radius of curvature at h is the thickness of the cladding layer at the current point, p' is the optimized overlap spacing on the convex surface, and p" is the optimized overlap spacing on the concave surface. In this way, the optimal overlap adaptation for different curvatures can be achieved, ensuring that the volume of multiple valleys is equal to the overlapping volume, and reducing the waviness of the cladding layer surface.

[0099] Furthermore, according to the optimal overlap model, the obtained free-form surface slice point cloud is filled with trajectories. First, according to the given initial trajectory plane M initial , obtain the discrete points p on the free surface through iteration i To the initial trajectory plane M initial When the distance is less than the given threshold δ error , then save the current reference point. After completing the iterative judgment of discrete points, the initial scanning trajectory L can be obtained. initial ,like Figure 5 (a) shown.

[0100] Further, with the initial trajectory L initial As a reference, take the initial trajectory L initial Any point p i As the reference point, take the current reference point tangent line V tangent_i is the normal vector, passing through the current reference point p i Draw an orthogonal plane M normal_i , and iterate again to get the discrete points on the free surface to the orthogonal plane M normal_i The distance, and then we can get the orthogonal secant line L cutting_i . Iterate the orthogonal secant line L cutting_i Previous point to current reference point p i When the arc length is equal to the optimal overlap distance, the point is recorded as the optimal overlap spacing point. like Figure 5 (b) shows the completion of the initial trajectory L initial By iterating point by point, the generation of adjacent overlapping trajectories can be obtained.

[0101] Furthermore, by taking the generated adjacent overlapped tracks as references and repeating the above operations, the scanning track can be completed from the center to both sides, and finally the filling of the free-form surface can be completed, such as Figure 5 As shown in (c)(d).

[0102] By establishing an equal volume overlap model, the overlap spacing is adaptively adjusted according to the curvature distribution of the free-form surface slices to achieve adaptive filling of the free-form surface slice trajectory, overcoming the problem of uneven thickness of the cladding layer when filling free-form surface slices with traditional fixed spacing, ensuring that the volume of the overlap valley at different curvatures is equal to the overlapping volume, and reducing the waviness of the cladding layer surface.

[0103] The specific steps of trajectory post-processing described in step 4 are as follows: according to the needs of the robot laser cladding process, the generated free-form surface scanning trajectory is topologically sorted. The sorted scanning trajectory points are used as processing points, and safety points are inserted between different scanning trajectories. Then, the overall processing trajectory is fitted using the NURBS curve to ensure the smoothness and accuracy of the processing trajectory and eliminate the processing jitter caused by the original discrete data. Then, according to the different types of processing points and safety points in the processing trajectory, the synchronous laser control signal is set to realize the coordinated triggering of the laser process parameters during the robot movement, and finally drive the robot to achieve target movement and process control, and complete the adaptive repair of the free-form surface.

[0104] To further illustrate the effectiveness and practicality of this embodiment, an application case of this embodiment - turbine guide blade repair is used for experimental verification. Due to long-term operation in a high temperature, high pressure, and high fatigue environment, irregular surface wear and deformation is likely to occur near the trailing edge of the blade basin.

[0105] The robot laser repair experimental platform used in this embodiment is composed of a Kawasaki robot, a line laser sensor, a laser, a water cooler, a powder feeder, a laser cladding head, and a coaxial powder feeding cladding nozzle, etc. In addition, by installing a laser tracker target ball on the laser cladding head, the robot position information is dynamically collected during the actual processing process to verify the effectiveness and practicality of the adaptive surface slicing and trajectory planning method proposed in this embodiment.

[0106] Figure 6 In the process of adaptive slicing of the blade wear body, the actual model of the worn blade collected online by the line laser is compared with the original standard model, and the blade wear condition is analyzed to obtain the blade wear body to be repaired. Then the blade wear body is divided into the wear model surface and the standard model surface. Then, the method described in this embodiment is applied to obtain normal equidistant surface slices, and the adaptive slicing of the blade wear body is achieved by repeatedly iterating the surface slice generation method. The final results of the 6 surface slices obtained are as follows: Figure 7The experimental results show that the free-form surface adaptive slicing method of this embodiment can overcome the serious "staircase effect" and poor bottom bonding strength problems of traditional plane slicing, realize conformal cladding of free-form surface wear, and ensure the full fusion of the cladding layer and the substrate surface. At the same time, the adaptive surface slicing ensures the continuity of the slice layer, eliminates the serious "staircase effect" of traditional plane slicing, and ensures the quality and efficiency of the repair.

[0107] Figure 8 The experimental diagram of the surface slice filling method for optimizing the optimal overlap spacing during the blade repair process. By establishing an equal volume overlap model, the optimal overlap point of the current reference trajectory is iteratively calculated point by point according to the distribution of the curvature of the free surface slice, and the adjacent overlap trajectory is obtained. Further, with the generated adjacent overlap trajectory as a reference, the above method is repeatedly iterated to achieve the growth of the scanning trajectory from the center to the sides, and finally the overlap trajectory filling of 6 surface slices is achieved, as shown in Fig. 9 The experimental results show that this embodiment dynamically optimizes the overlap spacing according to the curvature distribution of the blade surface slices, ensures that the volume of multiple valleys at different curvature locations is equal to the overlapping volume, and minimizes the waviness of the blade cladding layer surface.

[0108] Fig.10 The robot command position and feedback position information are collected during the blade cladding process. From the experimental results, it can be seen that the adaptive surface slicing and trajectory planning method proposed in this paper can achieve high-precision random repair of worn surfaces and impact-free trajectory control. Fig.11 The experimental results show that the adaptive surface slicing and trajectory planning method proposed in this embodiment can ensure the processing accuracy and efficiency of free-form surface repair.

[0109] An adaptive repair system for a free-form surface, comprising:

[0110] The module for constructing the object to be restored is used to discretize the data of the worn workpiece to obtain the worn object to be restored; adaptively segment the worn object to be restored to obtain an initial reference surface; wherein the initial reference surface includes the bottom surface of the worn model and the top surface of the standard model;

[0111] A trajectory adaptive filling module is used to construct a free-form surface slice according to the initial reference surface, calculate the surface curvature distribution data of the free-form surface slice, and construct a curvature-overlap spacing optimization model to perform trajectory adaptive filling on the free-form surface slice to obtain a free-form surface scanning trajectory;

[0112] The fitting module is used to topologically sort the scanning trajectory points in the free-form surface scanning trajectory to obtain a processing trajectory, fit the processing trajectory, and complete the adaptive repair of the free-form surface.

[0113] An electronic device comprises a memory and a processor, wherein the memory is used to store a computer program, and the processor runs the computer program to enable the electronic device to execute the self-adaptive repair method for a free-form surface.

[0114] A computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method for adaptively repairing a free-form surface is implemented.

[0115] The above is only a preferred specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for adaptive repair of free-form surfaces, characterized in that: include: Step 1: discretize the data of the worn workpiece to obtain the worn workpiece to be repaired; Adaptively segmenting the worn object to be restored to obtain an initial reference surface; wherein the initial reference surface includes a bottom surface of a worn model and a top surface of a standard model; Step 2: Calculate the normal vector of each discrete point in the initial reference surface, construct a tangent sphere model corresponding to the discrete point based on each normal vector, and construct an envelope surface tangent to each tangent sphere model as a free surface slice; Step 3: Calculate the surface curvature distribution data of the free-form surface slice, construct a curvature-overlapping distance optimization model to perform trajectory adaptive filling on the free-form surface slice, and obtain a free-form surface scanning trajectory; Step 4: topologically sorting the scanning trajectory points in the free-form surface scanning trajectory to obtain a processing trajectory, fitting the processing trajectory, and completing the adaptive repair of the free-form surface.

2. The method for adaptively repairing a free-form surface according to claim 1, characterized in that: The step 1 specifically includes: Discretizing the data of the standard workpiece and the worn workpiece respectively to obtain a standard point cloud model and a worn object to be restored, and iteratively obtaining the gap value between the worn object to be restored and the standard point cloud model point by point; The worn object to be restored is adaptively segmented based on the gap value to obtain an initial reference surface.

3. The method for adaptively repairing a free-form surface according to claim 1, characterized in that: The step three specifically includes: Constructing a curvature-overlap spacing optimization model based on the surface curvature distribution data according to an equal volume overlap model; Setting an initial trajectory plane and a distance threshold, obtaining distance data from each discrete point in the free-form surface slice to the initial trajectory plane, judging the distance data of each discrete point based on the distance threshold, saving discrete points corresponding to distance data less than the distance threshold, and constructing an initial scanning trajectory based on the saved discrete points; Iteratively calculating the overlap spacing optimization points corresponding to each point on the initial scanning trajectory, and generating adjacent overlap trajectories based on the overlap spacing optimization points; The free-form surface slices are adaptively filled based on the adjacent overlapping trajectories to obtain a free-form surface scanning trajectory.

4. The method for adaptively repairing a free-form surface according to claim 1, characterized in that: The step 4 specifically includes: The scanning trajectory points in the free-form surface scanning trajectory are topologically sorted, and the topologically sorted scanning trajectory points are used as processing points. Based on the processing points, safety points are inserted between different free-form surface scanning trajectories to obtain a processing trajectory. The processing trajectory is fitted based on a NURBS curve to complete the adaptive repair of the free-form surface.

5. An adaptive repair system for free-form surfaces, characterized in that: include: The module for constructing the object to be restored is used for discretizing the data of the worn workpiece to obtain the worn object to be restored; Adaptively segmenting the worn object to be restored to obtain an initial reference surface; wherein the initial reference surface includes a bottom surface of a worn model and a top surface of a standard model; A trajectory adaptive filling module is used to calculate the normal vector of each discrete point in the initial reference surface, construct a tangent sphere model of the corresponding discrete point based on each normal vector, and construct an envelope surface tangent to each tangent sphere model as a free-form surface slice; calculate the surface curvature distribution data of the free-form surface slice, and construct a curvature-overlap spacing optimization model to perform trajectory adaptive filling on the free-form surface slice to obtain a free-form surface scanning trajectory; The fitting module is used to topologically sort the scanning trajectory points in the free-form surface scanning trajectory to obtain a processing trajectory, fit the processing trajectory, and complete the adaptive repair of the free-form surface.

6. An electronic device, characterized in that: It comprises a memory and a processor, the memory is used to store a computer program, and the processor runs the computer program to enable the electronic device to execute a method for adaptively repairing a free-form surface according to any one of claims 1 to 4.

7. A computer-readable storage medium, characterized in that: The device stores a computer program, which, when executed by a processor, implements a method for adaptively repairing a free-form surface as described in any one of claims 1 to 4.

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