Blade repair path conformal compensation method and equipment based on non-rigid matching

Abstract

The invention belongs to the related technical field of aero-engine manufacturing and precision repair, and discloses a blade repair path follow-up compensation method and device based on non-rigid matching, and the method comprises the steps: S1, reconstructing a machining error reference point cloud curved surface based on a scanning data point set and a repair region design model; s2, performing unified modeling on the static deviation of the machining error of the to-be-compensated blade to obtain an error transfer model, and simplifying the corresponding nonlinear comprehensive machining error into a calculation equation of linear pose deviation of a local workpiece coordinate system; s3, establishing a tangent contact approximation cost function based on non-rigid matching so as to register and approach a target curved surface under the constraint of retaining tool path features, and meanwhile, solving a calculation equation by adopting a least square method so as to obtain a linear pose deviation of a local workpiece coordinate system, solving to obtain a pose deviation of each tangent contact coordinate system so as to obtain a linear pose deviation of each tangent contact coordinate system; and furthermore, each cutting contact and each cutter location point are updated, and the shape follow-up compensation of the blade is realized. The compensation precision is improved.

Description

Technical Field

[0001] This invention belongs to the technical field of aero-engine manufacturing and precision repair, and more specifically, relates to a method and device for conformal compensation of blade repair path based on non-rigid matching. Background Technology

[0002] As the heart of an aircraft, the aero-engine is a core component and power source, and its performance directly affects the aircraft's safety and economy. Blade-like components are widely used in aero-engines. This study focuses on integral bladed disks (IBDs). Compared to traditional bladed turbine disk structures commonly used in aero-engines, IBDs feature a compact, high-strength design, capable of withstanding higher speeds and operating temperatures, and offer significant improvements in reliability, safety, and airtightness. With advancements in aero-engine technology, IBDs are becoming increasingly widespread, commonly used in critical components such as compressors, turbines, and fans. Turbine and fan blades operate under harsh conditions of high temperature, high pressure, and high speed during service, making them susceptible to various forms of damage, such as cracks, wear, corrosion, and fracture. These damages not only reduce engine performance but can also lead to serious safety accidents. Blades are expensive; for example, high-pressure turbine blades cost over 100,000 RMB each. Since IBDs are machined as a single unit, individual blade replacement is not possible, making direct disk replacement prohibitively costly. Therefore, researching and developing effective blade repair technologies for bladed disks is crucial for reducing maintenance costs and improving service performance.

[0003] Achieving adaptive machining quality control for blade repair in high-end equipment such as aero-engines has become one of the core hot issues in advanced manufacturing research and engineering applications in recent years. After the damaged areas of the blade are repaired using additive manufacturing technology, subsequent processing using subtractive machining processes such as CNC milling and precision grinding and polishing is necessary to ensure that the geometry and surface accuracy of the repaired area meet the stringent engineering standards of critical equipment such as aero-engines. For the repair of complex components such as integral bladed disks, it is essentially a typical reverse engineering task. Due to high-temperature creep, fatigue damage, or the lack of reference information such as original design drawings and 3D models during service, there is a significant deviation between the actual shape of the bladed disk and the theoretical design state. Moreover, this deviation is often coupled with the reference positioning deviation, making it difficult for traditional positioning machining modes based on fixed tooling and preset programs to meet the requirements of high-precision repair. In current blade repair processing, the industry generally adopts the repair compensation scheme of in-machine measurement-cut depth direction allowance compensation, which shifts the tool position point in the cut depth direction to compensate for the comprehensive processing error. However, due to the deformation of the actual blade surface and the offset of the reference, there is a nonlinear deviation between the actual target surface and the theoretical model. The traditional compensation mapping in the cut depth or normal direction is difficult to establish an accurate correspondence between the cutting contact points in the area to be repaired, which can easily lead to problems such as deviation of the processing streamline, undercutting or overcutting in the blade edge area, which seriously affects the geometric accuracy and aerodynamic performance after the blade is repaired. Summary of the Invention

[0004] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides a non-rigid matching blade repair path conformal compensation method and device, which aims to solve the problem of low compensation accuracy of existing blades.

[0005] To achieve the above objectives, according to one aspect of the present invention, a method for conformal compensation of blade repair paths based on non-rigid matching is provided, comprising the following steps: S1 employs a non-rigid ICP point cloud registration algorithm based on scanned data point sets. And repair the design model of the area to reconstruct the reference point cloud surface for processing errors; S2, Based on the machining error reference point cloud surface, the static deviation of the machining error of the blade to be compensated is uniformly modeled to obtain the error propagation model; Based on the error propagation model, the corresponding nonlinear comprehensive machining error is simplified into the calculation equation of the linear pose deviation of the local workpiece coordinate system. S3. Based on non-rigid matching, a cutting contact point approximation cost function is established. The cutting contact point approximation cost function is used to register and approximate the target surface under the constraint of preserving toolpath features. At the same time, the least squares method is used to solve the calculation equation to obtain the linear pose deviation of the current local workpiece coordinate system. Based on the linear pose deviation of the current local workpiece coordinate system, the pose deviation of each cutting contact point coordinate system is obtained. Based on the obtained pose deviation, each cutting contact point and tool position point is updated to realize the conformal compensation of the blade.

[0006] Furthermore, the scan data point set With design model data point set Registration is performed to obtain the reference point cloud surface for machining errors.

[0007] Furthermore, design the model data point set. Density is obtained using a curvature-based adaptive sampling method.

[0008] Furthermore, for each discrete point... Establish the coordinate system of the contact point respectively. ,by Indicates the theoretical processing point. If the actual contact point is [the location of the contact], then [it is in the context of the actual contact point]. Comprehensive machining error based on the point-tangent definition in the coordinate system Represented as:

[0009] In the formula, For contact point Machining error in the normal direction.

[0010] Furthermore, the local workpiece coordinate system pose deviation Simultaneously, the pose deviation of the coordinate system of the contact point Satisfying the speed-related changes, for the contact point Its position in the workpiece coordinate system is The overall machining error is then derived as follows:

[0011] In the formula, This refers to the local workpiece coordinate system position error; This refers to the local workpiece coordinate system attitude error. coordinate system Position error; coordinate system Attitude error; coordinate system of The unit vector of the axis in the local workpiece coordinate system; For contact point Coordinates in the local workpiece coordinate system.

[0012] Furthermore, the local workpiece coordinate system pose deviation Pose deviation of the contact point coordinate system The following relationship exists between them: .

[0013] Furthermore, the solution process is implemented based on nearest neighbor iteration. Feature registration between the tangent contact point and the target surface is used to improve the accuracy of the tangent contact point correspondence. The following tangent contact point approximation cost function is established to solve the local workpiece pose change:

[0014] In the formula, Characterize the approximation between measurement error and theoretical error; simultaneously construct a rigidity term. Maintain the characteristics of the contact point distribution. Constraints are provided for the continuous pose changes between various processing points; among which...

[0015]

[0016] In the formula, The comprehensive machining error is nonlinear. The actual processing error was calculated using nearest neighbor retrieval. This represents the total number of discrete contact points. For contact point Local workpiece coordinate system pose deviation corresponding to other contact points in the neighborhood; This is the Frobenius norm operator.

[0017] Furthermore, during the repeated iterative convergence process, the rigid weight term The decay gradually decreases as the number of iterations increases.

[0018] The present invention also provides a non-rigid matching blade repair path conformal compensation system, the system including a memory and a processor, the memory storing a computer program, and the processor executing the computer program to perform the non-rigid matching blade repair path conformal compensation method as described above.

[0019] The present invention also provides a computer-readable storage medium storing machine-executable instructions, which, when invoked and executed by a processor, cause the processor to implement the non-rigid matching-based blade repair path conformal compensation method as described above.

[0020] In summary, compared with the prior art, the conformal compensation method and equipment for blade repair paths based on non-rigid matching provided by the present invention have the following advantages: 1. This invention reconstructs the error reference of the repaired area after deformation based on the non-rigid approximation of point cloud. It relies on the original surface of the repaired area as the approximation benchmark and improves the non-rigid ICP registration accuracy by using curvature sampling. In this way, a reference benchmark for reconstructing the damaged blade after deformation and pose displacement is realized, making the calculation and evaluation of processing errors more accurate and reliable, thereby improving the compensation accuracy.

[0021] 2. This invention achieves shape matching between the tool contact point and the target surface during toolpath compensation by using feature approximation registration. This allows the machining path to still achieve conformal compensation even when the target surface of the blade undergoes torsional deformation, thereby improving the accuracy of repair and compensation machining.

[0022] 3. The compensation method provided by this invention unifies the static errors caused by factors such as clamping, measurement, and support by defining and dividing the local workpiece coordinate system. It simplifies the nonlinear comprehensive error distribution into a local linear workpiece coordinate system pose deviation for compensation, which simplifies the implementation logic of compensation processing and improves the computational efficiency of the algorithm.

[0023] 4. Design the model data point set A curvature-based adaptive density sampling method is adopted to obtain the data. Higher sampling density is used in high curvature regions such as the leaf edge to improve the density sensitivity of the non-rigid ICP registration method, prevent the registration results from shifting to the leaf surface region with a larger point cloud scale, and improve the registration accuracy of the leaf edge region. Attached Figure Description

[0024] Figure 1 This is a flowchart of a blade repair path conformal compensation method based on non-rigid matching provided in an embodiment of the present invention; Figure 2 These are the scanning point cloud image and the design point cloud image of a semi-finished sample of a blade in service according to the present invention, wherein (a) is the design point cloud image and (b) is the scanning point cloud image of the semi-finished result; Figure 3 This is a schematic diagram of the non-rigid ICP reference reconstruction calculated in step S1 of the embodiment of the present invention; Figure 4 This is a schematic diagram of the contact point coordinate system established in step S2 of the embodiment of the present invention; Figure 5 This is a schematic diagram of the implementation logic of the conformal compensation scheme of the present invention, wherein (a) is a schematic diagram of compensation processing, (b) is a schematic diagram of compensation cross section in the cutting depth direction, and (c) is a schematic diagram of conformal compensation cross section under a non-rigid matching frame. Figure 6 The above are the simulation and example compensation and repair results of the compensation path processing calculated in step S3 of the present invention, where (a) is the color map of the compensation processing result error and (b) is the comparison map of the sampling error of the repair area. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0026] Please see Figure 1 and Figure 2 This invention provides a non-rigid matching blade repair path conformal compensation method. The conformal compensation method is for aero-engine damaged blades with deformation and positioning reference deviation on the milling station. It can effectively reconstruct the repair reference reference and generate conformal compensation tool path based on the semi-finishing tool path while maintaining the original feature distribution.

[0027] The conformal compensation method mainly includes the following steps: S1 employs a non-rigid ICP point cloud registration algorithm based on scanned data point sets. The design model of the repair area is used to reconstruct the reference point cloud surface for processing errors.

[0028] Scan data point set Data was obtained through a 3D scanner; point cloud sampling was performed on the design model of the repair area to obtain the design model data point set. Scan the data point set Affine transformation to design model data point set This is to achieve initial alignment between the measurement coordinate system and the design (workpiece) coordinate system.

[0029] Design model data point set A curvature-based density adaptive sampling method is employed, using higher sampling density in high-curvature regions such as the leaf edge. This improves the density sensitivity of the non-rigid ICP registration method, prevents the registration results from shifting to the larger point cloud area of ​​the leaf blade surface, and enhances the registration accuracy in the leaf edge region. Specifically, the scanned data point set... With design model data point set Registration is performed to obtain the reference point cloud surface for machining errors.

[0030] like Figure 5As shown, the damaged blade exhibits bending and torsional deformation. To reconstruct the blade's deformation during clamping and support processes in machine operation and obtain a nominal reference for error calculation, a non-rigid ICP registration-based method is used to reconstruct the target surface, incorporating the design model data point set. To scan data point set Registration is performed to obtain the reconstructed target surface point set. and the target surface point set The machining error is calculated using a reference standard as a benchmark, and the reconstruction result is as follows: Figure 3 As shown.

[0031] S2, Based on the machining error reference point cloud surface, the static deviation of the machining error of the blade to be compensated is uniformly modeled to obtain the error propagation model; Based on the error propagation model, the corresponding nonlinear comprehensive machining error is simplified into the calculation equation of the linear pose deviation of the local workpiece coordinate system.

[0032] The correspondence between the contact point coordinate system and the workpiece coordinate system is as follows: Figure 4 As shown, the toolpath for semi-finishing milling is distributed in the workpiece coordinate system as a series of ordered discrete points. Below, a corresponding tangent point coordinate system is established at each machining point to reasonably characterize the semi-finishing milling error. It is assumed that a milling toolpath exists. If there are multiple tool positions, the toolpath trajectory can be discretized into a set of discrete points. For each discrete point Establish the coordinate system of the contact point respectively. For the coordinate system of the contact point The origin of the coordinate system is the point of contact. The axis is the feed direction of the tool at the point of contact. axial direction Unit normal vector at point direction, The axis is defined by the right-hand rule.

[0033] by Indicates the theoretical processing point. If the actual contact point is [the location of the contact], then [it is in the context of the actual contact point]. Comprehensive machining error based on the point-tangent definition in the coordinate system This can be expressed as: (1) In the formula, For contact point Machining error in the normal direction.

[0034] Local workpiece coordinate system pose deviation Simultaneously, the pose deviation of the coordinate system of the contact point Satisfying the speed-related changes, for the contact point Its position in the workpiece coordinate system is Then, by further combining with formula (1), the comprehensive processing error can be derived as follows: (2) In the formula, This refers to the local workpiece coordinate system position error; This refers to the local workpiece coordinate system attitude error. coordinate system Position error; coordinate system Attitude error; coordinate system of The unit vector of the axis in the local workpiece coordinate system; For contact point Coordinates in the local workpiece coordinate system.

[0035] Meanwhile, the local workpiece coordinate system pose deviation Pose deviation of the contact point coordinate system The following relationship exists between them: (3) Neglecting tool deformation, machining errors are directly related to workpiece orientation deviations. Deformation deviations caused by process deformation are static during machining, thus allowing for the unification of workpiece orientation deviations and deformation errors. Static error deformation can be considered as rigid deformation within local areas, thereby unifying the static process deformation errors caused by support and workpiece orientation deviations. This is necessary for each cutting point... Due to local workpiece coordinate system pose deviation This causes an offset in the actual processing point. For example... Figure 4 As shown, establishing a local workpiece coordinate system near the machining point ensures that the pose of the machining point is unique and fixed relative to the workpiece coordinate system. Therefore, the local pose change can be described as follows: .in Let be the number of contact points. Combining formulas (1) to (3), the nonlinear comprehensive machining error is thus simplified into the linear pose deviation of each local coordinate system.

[0036] The compensation process uses rigid support to suppress dynamic machining errors caused by factors such as vibration and tool deformation. Static machining errors caused by process deformation and reference deviation are the main sources of error in the compensation process.

[0037] S3. Based on non-rigid matching, a cutting contact point approximation cost function is established. The cutting contact point approximation cost function is used to register and approximate the target surface under the constraint of preserving toolpath features. At the same time, the least squares method is used to solve the calculation equation to obtain the linear pose deviation of the current local workpiece coordinate system. Based on the linear pose deviation of the current local workpiece coordinate system, the pose deviation of each cutting contact point coordinate system is obtained. Based on the obtained pose deviation, each cutting contact point and tool position point is updated to realize the conformal compensation of the blade.

[0038] like Figure 5 As shown, this embodiment of the invention, while ensuring continuous change in the pose of the local workpiece coordinate system, implements the solution process based on nearest neighbor iteration. It uses feature registration between the tangent contact point and the target surface to improve the accuracy of the tangent contact point correspondence, and establishes the following tangent contact point approximation cost function to solve for the local workpiece pose change: (4) Constructing an approximation term to achieve accurate compensation of the contact point, wherein, Characterize the approximation between measurement error and theoretical error; simultaneously construct a rigidity term. Maintain the characteristics of the contact point distribution. Constraints for continuous pose changes between various processing points; where: (5) (6) in the formula The comprehensive machining error is nonlinear. The actual processing error was calculated using nearest neighbor retrieval. This represents the total number of discrete contact points. For contact point Local workpiece coordinate system pose deviation corresponding to other contact points in the neighborhood; This is the Frobenius norm operator. Construct a quadratic form matrix from equation (4), and then construct a matrix using equation (2). , which is the first The diagonal terms are Diagonal matrix of the matrix block; construct the measured error matrix Constructing a rigid matrix ,Depend on indivual Composed of matrix blocks, if the contact point There are tangents in the neighborhood. and ,but In the matrix Location is Matrix blocks, at the same time and Location is The matrix block can rewrite the cost function for approximating the contact point as follows: (7) The cost function for approximating the contact point is solved using the least squares method, utilizing the fact that the derivative is zero at the minimum value to solve for the set of local workpiece pose deviation matrices. Set the local workpiece pose deviation matrix. Substituting into formula (3), the pose change vector of the contact point coordinate system can be solved. The coordinate system of the tangent contact point is updated, and the tangent contact point and the target surface point set are calculated using nearest neighbor retrieval. And calculate the measured machining error. .

[0039] During the repeated iterative convergence process, the rigid weight term The decay gradually decreases with the number of iterations, reaching its maximum at the 1st iteration. In the next iteration loop satisfy The attenuation formula is used until the set of local workpiece pose deviation matrices is reached. If the results of two consecutive iterations do not change significantly, exit the iteration loop and update... Continue iterating. The iteration terminates when the measured machining error meets the expected error range, and the final set of local workpiece pose deviation matrices is output. .

[0040] The measured machining error value is obtained from the nearest neighbor distance between the cutting contact point and the machining error reference point cloud surface; the cutting contact point approximation iteration process is as follows: Calculate the coordinate system of each contact point Actual machining error .

[0041] A cost function for approximating the contact point is established based on non-rigid matching. Under the constraint of preserving toolpath characteristics, the target surface is registered and approximated to achieve conformal compensation. The local workpiece coordinate system pose deviation is solved by least squares. .

[0042] Based on the deviation of the tangent point coordinate system Update the coordinate system of the contact point.

[0043] Repeat the above steps until the error converges to the expected range.

[0044] like Figure 4 As shown, there is an offset relationship between the set of machining points and the actual tool position point. It is assumed that the machining points... The surface normal vector is The tool radius is The actual tool position coordinates can be obtained by solving the following formula: (8) Figure 6 The final compensation processing simulation result of this embodiment is as follows: Figure 6 As shown, the simulation results of the processing were sampled in the leaf edge area. The compensation simulation results showed that the error distribution was between -0.02mm and 0.02mm, and the processing error was uniformly distributed.

[0045] This invention effectively overcomes the problems of reference failure caused by comprehensive static deviation in the repair and processing of aero-engine blades, unreliable calculation of processing errors, and difficulty in establishing the correct tool position compensation correspondence in the compensation processing process. It significantly reduces the impact of process deformation and positioning error on the processing accuracy of blade compensation and repair, and is particularly suitable for aero-engine blade compensation and repair processing scenarios with various static deformations or unreliable positioning references.

[0046] The present invention also provides a non-rigid matching blade repair path conformal compensation system, the system including a memory and a processor, the memory storing a computer program, and the processor executing the computer program to perform the non-rigid matching blade repair path conformal compensation method as described above.

[0047] The present invention also provides a computer-readable storage medium storing machine-executable instructions, which, when invoked and executed by a processor, cause the processor to implement the non-rigid matching-based blade repair path conformal compensation method as described above.

[0048] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for conformal compensation of blade repair paths based on non-rigid matching, characterized in that, The steps are as follows: S1 employs a non-rigid ICP point cloud registration algorithm based on scanned data point sets. And repair the design model of the area to reconstruct the reference point cloud surface for processing errors; S2, Based on the machining error reference point cloud surface, the static deviation of the machining error of the blade to be compensated is uniformly modeled to obtain the error propagation model; Based on the error propagation model, the corresponding nonlinear comprehensive machining error is simplified into the calculation equation of the linear pose deviation of the local workpiece coordinate system. S3. Based on non-rigid matching, a cutting contact point approximation cost function is established. The cutting contact point approximation cost function is used to register and approximate the target surface under the constraint of preserving toolpath features. At the same time, the least squares method is used to solve the calculation equation to obtain the linear pose deviation of the current local workpiece coordinate system. Based on the linear pose deviation of the current local workpiece coordinate system, the pose deviation of each cutting contact point coordinate system is obtained. Based on the obtained pose deviation, each cutting contact point and tool position point is updated to realize the conformal compensation of the blade.

2. The blade repair path conformal compensation method based on non-rigid matching as described in claim 1, characterized in that: Scan the data point set With design model data point set Registration is performed to obtain the reference point cloud surface for machining errors.

3. The blade repair path conformal compensation method based on non-rigid matching as described in claim 2, characterized in that: Design model data point set Density is obtained using a curvature-based adaptive sampling method.

4. The blade repair path conformal compensation method based on non-rigid matching as described in claim 1, characterized in that: For each discrete point Establish the coordinate system of the contact point respectively. ,by Indicates the theoretical processing point. If the actual contact point is [the location of the contact], then [it is in the context of the actual contact point]. Comprehensive machining error based on the point-tangent definition in the coordinate system Represented as: In the formula, For contact point Machining error in the normal direction.

5. The blade repair path conformal compensation method based on non-rigid matching as described in claim 4, characterized in that: Local workpiece coordinate system pose deviation Simultaneously, the pose deviation of the coordinate system of the contact point Satisfying the speed-related changes, for the contact point Its position in the workpiece coordinate system is The overall machining error is then derived as follows: In the formula, This refers to the local workpiece coordinate system position error; This refers to the local workpiece coordinate system attitude error. coordinate system Position error; coordinate system Attitude error; coordinate system of The unit vector of the axis in the local workpiece coordinate system; For contact point Coordinates in the local workpiece coordinate system.

6. The blade repair path conformal compensation method based on non-rigid matching as described in claim 5, characterized in that: Local workpiece coordinate system pose deviation Pose deviation of the contact point coordinate system The following relationship exists between them: 。 7. The blade repair path conformal compensation method based on non-rigid matching as described in any one of claims 1-6, characterized in that: The solution process is implemented based on nearest neighbor iteration. Feature registration between the contact point and the target surface is used to improve the accuracy of the contact point correspondence. The following contact point approximation cost function is established to solve the local workpiece pose change: In the formula, Characterize the approximation between measurement error and theoretical error; simultaneously construct a rigidity term. Maintain the characteristics of the contact point distribution. Constraints are provided for the continuous pose changes between various processing points; among which... In the formula, The comprehensive machining error is nonlinear. The actual processing error was calculated using nearest neighbor retrieval. This represents the total number of discrete contact points. For contact point Local workpiece coordinate system pose deviation corresponding to other contact points in the neighborhood; For Frobenius norm operators.

8. The blade repair path conformal compensation method based on non-rigid matching as described in claim 7, characterized in that: During the repeated iterative convergence process, the rigid weight term The decay gradually decreases as the number of iterations increases.

9. A conformal compensation system for blade repair paths based on non-rigid matching, characterized in that: The system includes a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, it performs the conformal compensation method for blade repair path based on non-rigid matching as described in any one of claims 1-8.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores machine-executable instructions, which, when invoked and executed by a processor, cause the processor to implement the non-rigid matching blade repair path conformal compensation method according to any one of claims 1-8.

Images