A method, system, storage medium and product for decoupling tool mark errors during blisk repair

Abstract

The present invention belongs to the field of blade repair processing, and specifically discloses a method, system, storage medium and product for decoupling the tool mark error during the repair of an integral blade disk, comprising: based on the tool mark error after the blade repair, determining the iterative function #imgabs0# of the actual undeformed cutting depth according to the fixed point iteration method: #imgabs1# wherein a k 、a k+1 are the actual undeformed cutting depths at the kth and k+1th iterations, respectively. e The target cutting depth, Δd, and f represent the tool mark error and yield deformation error functions. The iterative function #imgabs2# is solved using the Mueller iteration method to obtain the actual undeformed cutting depth a at which the iterative function converges. The workpiece positioning error and yield deformation error are then determined based on the actual undeformed cutting depth a, achieving decoupling of the tool mark error. This method significantly reduces the impact of positioning error and yield deformation error during blade repair, improves the accuracy of tool mark error compensation, and is applicable to various aircraft engine integral blade disc repair and compensation processes.

Description

Technical Field

[0001] The present invention belongs to the field of blade repair processing, and more specifically, relates to a method, system, storage medium and product for decoupling tool mark errors during integral blade disk repair. Background Art

[0002] To improve aeroengine thrust-to-weight ratios, reduce structural mass, and enhance reliability and aerodynamic efficiency, the use of integral blisks in place of conventional blades is a major development trend both domestically and internationally. Due to the high manufacturing costs and processing difficulties of blisks, and the significant economic losses associated with direct replacement, laser cladding and other repair methods are often used to repair individual blades in service.

[0003] Compared to traditional manufacturing, the repair process for damaged blisks cannot be directly machined according to the designed model due to the uneven deformation experienced during service. This process is prone to creating a cutter mark between the repaired area and the base. Because the cutter mark is affected by both workpiece positioning errors and tool deformation, direct compensation often fails to meet the required repair accuracy. Therefore, it is necessary to decouple and predict different error sources to achieve comprehensive compensation for blisks, thus employing different compensation strategies. Summary of the Invention

[0004] In response to the above-mentioned defects or improvement needs of the prior art, the present invention provides a method, system, storage medium and product for decoupling the tool mark error during the repair of an integral blade disk. The purpose is to achieve rapid and accurate decoupling of the tool mark error during the repair of an integral blade disk, so as to compensate for different errors separately and improve the repair processing accuracy.

[0005] To achieve the above objectives, according to a first aspect of the present invention, a method for decoupling tool mark errors during blisk repair is proposed, comprising the following steps:

[0006] Based on the blade repair mark error, the iterative function of the actual undeformed cutting depth is determined according to the fixed point iteration method. for: Among them, a k 、a k+1 are the actual undeformed cutting depths at the kth and k+1th iterations, respectively. e is the target cutting depth, Δd is the tool mark error, and f is the tool deformation error function;

[0007] Based on the Mueller iteration method, iterative function The solution is performed to obtain the actual undeformed cutting depth a when the iterative function converges; then, based on the actual undeformed cutting depth a, the workpiece positioning error and the tool deformation error are determined to achieve the decoupling of the tool mark error.

[0008] As a further preferred method, the iterative function is Solve, including:

[0009] The iterator function The accelerated iterative formula is transformed into an accelerated iterative formula, and then the accelerated iterative formula is solved based on the Mueller iteration method; the accelerated iterative formula is:

[0010]

[0011] Among them, the parameter ω=F[a k ,a k-1 ]+F[a k ,a k-2 ]-F[a k-1 ,a k-2 ], a k-1 、a k-2 are the actual undeformed cutting depths at the k-1th and k-2th iterations, respectively; F represents the difference quotient; and sign represents the sign function.

[0012] As a further preferred method, when solving the accelerated iteration formula based on the Mueller iteration method, the initial value of the actual undeformed cutting depth is determined as follows: let the initial workpiece positioning error e h0 =Δd, and then we get a1=a e -e h0 ; Then, according to the iterative function, a2 and a3 are calculated.

[0013] As a further preferred embodiment, the workpiece positioning error and the tool deformation error are determined based on the actual undeformed cutting depth a, including: after determining the actual undeformed cutting depth a, the tool deformation error e is determined. f =f(a); workpiece positioning error e h =Δd-e f .

[0014] As a further preferred embodiment, the tool deformation error function f is a nonlinear function of the actual undeformed cutting depth, which is calculated by a machining dynamics equation.

[0015] As a further preferred method, obtaining the blade joint mark error after the repair in advance includes:

[0016] The scanned point cloud of the repaired area of ​​the damaged blade of the integral blisk is obtained and aligned with the corresponding reference model point cloud. The aligned reference model point cloud and the scanned point cloud are compared to obtain the tool mark error of each tool position after the blade is repaired.

[0017] As a further preferred method, registering the scanned point cloud with the corresponding reference model point cloud includes:

[0018] Preliminary adjustment of the reference model point cloud through the affine transformation model to align it with the scanned point cloud;

[0019] The reference model point cloud is finely adjusted through a Gaussian mixture model-based registration method to ensure accurate alignment between the reference model point cloud and the scanned point cloud.

[0020] According to a second aspect of the present invention, a system for decoupling tool mark errors during blisk repair is provided, comprising a processor configured to execute the above-mentioned method for decoupling tool mark errors during blisk repair.

[0021] According to a third aspect of the present invention, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the method for decoupling tool mark errors during blisk repair is implemented.

[0022] According to a fourth aspect of the present invention, a computer program product is provided, which includes a computer program, and when the computer program is executed by a processor, the method for decoupling tool mark errors during repair of an integral blade disk is implemented.

[0023] In general, the above technical solutions conceived by the present invention have the following technical advantages compared with the existing technology:

[0024] The present invention takes into account the positioning error caused by factors such as workpiece clamping and measurement, as well as the machining tool deformation error, decouples the workpiece positioning error and tool deformation error through a numerical iteration method, and adopts an accelerated iteration algorithm based on the Mueller method to improve the convergence speed of the error decoupling process, thereby achieving efficient and high-precision decoupling and compensation of the tool mark error, thereby improving the accuracy of the repair processing as much as possible and increasing the success rate of blade repair.

[0025] The present invention can significantly reduce the influence of positioning error and tool deformation error in the repair processing of blade parts, improve the compensation calculation accuracy of tool mark error, and realize high-precision repair processing of damaged blades of integral blade disks. It is suitable for the repair and compensation processing of integral blade disks of various types of aircraft engines. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a flow chart of a method for decoupling tool mark errors during blisk repair according to an embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of the calibration of the scanned point cloud coordinates of the repair area of ​​a damaged blade of an integral blisk according to an embodiment of the present invention;

[0028] Figure 3 This is a schematic diagram of non-rigid registration of a damaged leaf according to an embodiment of the present invention;

[0029] Figure 4Schematic diagram of iterative decoupling calculation of positioning error and tool deformation error according to an embodiment of the present invention;

[0030] Figure 5 Schematic diagram of the tool mark error analysis results of an embodiment of the present invention. DETAILED DESCRIPTION

[0031] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is 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 for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0032] The embodiment of the present invention provides a method for decoupling tool mark errors during blade disk repair. Figure 1 As shown, the following steps are included:

[0033] (1) Obtain the joint mark error of the damaged blade of the integral blisk after repair.

[0034] The in-situ scanning point cloud file of the damaged blade repair area of ​​the semi-finished integral blade disk is measured by 3D scanning, and the reference model point cloud file is obtained through the CAD model; the scanning point cloud file in pcd, ply and other formats and the corresponding reference model point cloud file are imported, such as Figure 2 As shown, in this embodiment, the workpiece coordinate system sets the Z axis as the center axis direction of the blade disk, the X axis points to the reference point position of the blade disk, and the Y axis is determined by the right-hand rule.

[0035] Due to the uneven deformation of the actual damaged blade, a non-rigid point cloud registration method based on the Gaussian mixture model is used to register the reference model point cloud S and the scanned point cloud P to obtain the deformed reference model point cloud S'. The joint mark error of each tool point in the repair area is calculated based on S' and P, as shown in the following example: Figure 3 shown.

[0036] Specifically, during point cloud registration, the scale, rotation, and translation of the reference model point cloud are preliminarily adjusted through the affine transformation model so that it is roughly aligned with the scanned point cloud; then, fine-tuning is performed based on the Gaussian mixture model registration method to ensure high-precision alignment of the model point cloud and the scanned point cloud.

[0037] (2) The tool mark error is decoupled into workpiece positioning error and tool deformation error during milling process through numerical iteration method.

[0038] Since there is also a workpiece positioning error e h The tool deformation error e during milling process f =f(a), where f(a) is calculated by the machining dynamics equation, so that the actual undeformed cutting depth a=ae -e h -f(a), a e is the target cutting depth. The combined effect of these two errors results in a tool mark error between the final repair area and the base area. To compensate for the tool mark error, it is first necessary to decouple the workpiece positioning error from the tool deformation error so that each can be compensated separately. The tool mark error Δd and the actual undeformed cutting depth satisfy the following relationship:

[0039] Δd=e h +f(a)(1.1)

[0040] Since f(a) is a nonlinear function of the actual undeformed cutting depth a, it is impossible to obtain an explicit solution to equation (1.1), and a numerical iteration method is usually required to solve the equation.

[0041] Figure 4 This shows the iterative process using the fixed point iteration method:

[0042] First, for the obtained tool mark error Δd of any tool position, the initial position of the workpiece coordinate system correction is set to the actual cutting position, that is, e h0 =Δd, and the undeformed cutting depth a1 of the current iteration step is obtained.

[0043] In iteration step 1, the tool deformation error f1 (i.e., f(a1)) can be calculated by the established machining dynamics model, and the workpiece positioning error e h1 =Δd-f(a1).

[0044] In iteration step 2, the undeformed cutting depth a2 is updated, and the offset is equal to the tool deformation error f1, thereby obtaining the new workpiece positioning error e h2 and the tool deformation error f2, continue to iterate to get the next workpiece positioning error e h3 The iterative process continues until the set tolerance is met.

[0045] Undeformed cutting depth a during the iteration process k+1 It can be expressed as:

[0046] a k+1 =a e -e hk (1.2)

[0047] The workpiece positioning error is initially set to Δd. Based on the machining dynamics equation, the machining deformation error can be obtained as f(a k ), so the workpiece positioning error can be updated as:

[0048] e hk =Δd-f(a k )(1.3)

[0049] To achieve in-situ measurement and error decoupling of machining errors, error analysis must be performed on all point clouds in the semi-finished area to be repaired after measurement. This iterative analysis process must converge within the practically allowed computational time to minimize the impact of the error analysis process on overall machining efficiency. Exceeding the allowed iterative computational time or iterative divergence can affect the error compensation results in the next step or reduce the computational accuracy of the iterative process. Therefore, the convergence and convergence rate of the iterative process for error decoupling have a significant impact on the efficiency and accuracy of the repair process.

[0050] The above iterative process can be transformed into finding the root of equation (1.4). The undeformed cutting depth a in the k+1th iteration is k+1 It can be calculated from the target cutting depth, the measured tool mark error and the tool deformation:

[0051] a k+1 =a e -Δd+f(a k )(1.4)

[0052] Using iterative functions It can be expressed as

[0053]

[0054] Therefore, the iterative process In the root a * The convergence is local and linear near the . This iterative process converges slowly and may not meet the efficiency requirements of the in-situ measurement and tool mark error compensation algorithm when there are many measurement points in the repair area.

[0055] (3) An accelerated iterative algorithm based on the Mueller method is used to improve the convergence speed of the error decoupling process.

[0056] For equation (1.5), its derivative is not easy to obtain. To achieve a faster convergence rate, an accelerated iterative algorithm for the error decoupling process based on the Mueller method is proposed. This method does not require the calculation of derivatives and has a wide range of initial value selection. The solution of the target equation (1.5) is equivalent to the following equation:

[0057] F(a)=a e -Δd+f(a)-a=0(1.6)

[0058] Passing three points (a k-2 ,F(a k-2 ))、(a k-1 ,F(a k-1 )) and (a k ,F(a k The quadratic polynomial of )) is

[0059] pk (x) = F(a k )+(xa k )F[a k ,a k-1 ]+(xa k-1 )(xa k-1 )F[a k ,a k-1 ,a k-2 ](1.7)

[0060] Where F[a k ,a k-1 ] and F[a k ,a k-1 ,a k-2 ] represents the difference quotient.

[0061] Let ω=F[a k ,a k-1 ]+F[a k ,a k-2 ]-F[a k-1 ,a k-2 ], the above formula can be rewritten as:

[0062] p k (x) = F(a k )+ω(xa k )+F[a k ,a k-1 ,a k-2 ](xa k ) 2 (1.8)

[0063] Find the answer about (xa k ) and rationalize the numerator of the solution to be sought, the accelerated iteration formula for the undeformed cutting depth based on the Muller method can be obtained:

[0064]

[0065] Where ω=F[a k ,a k-1 ]+F[a k ,a k-2 ]-F[a k-1 ,a k-2 ], F represents the difference quotient, sign(ω) is the sign function, which means to select the one closer to a from the two zero points k The roots of the equation.

[0066] Specifically, the solution process of the Mueller iteration method is as follows:

[0067] Set the initial values ​​of iterative undeformed cutting depth a1, a2 and a3, and calculate a2 and a3 by a simple iterative method (Formula 1.5);

[0068] Calculate the current error function value F(a k ), intermediate variable ω=F[a k ,a k-1 ]+F[a k ,a k-2 ]-F[a k-1 ,a k-2 ];

[0069] Update the actual undeformed cutting depth using formula (1.9);

[0070] Repeat the above steps until the error converges to the predetermined range and the actual undeformed cutting depth a is obtained.

[0071] After determining the actual undeformed cutting depth a, the tool deformation error and workpiece positioning error can be obtained, and the tool mark error decoupling is completed. The tool mark error analysis of the repair area is as follows: Figure 5 As shown in Figure 1, the comprehensive machining error is obtained from the scanning point cloud, and the tool deformation error is obtained by decoupling.

[0072] According to the convergence analysis, the sequence generated by formula (1.9) converges and must converge to the zero point a of F. * It can be shown that the convergence order of this method is at least p = 1.839, where p is the equation p 3 -p 2 - the only real root of p-1 = 0. In contrast, the convergence order of the simple iterative method is only 1.

[0073] Note that Newton's method has second-order convergence Each iteration requires calculating two function values ​​F(a n ) and F′(a n ), while the Mueller method with a convergence order of 1.839 only needs to calculate one function value F(a n ), and there is no need to calculate derivatives, so the proposed method converges faster than the Newton iteration method in the actual calculation process.

[0074] It will be easily understood by those skilled in the art 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 in the scope of protection of the present invention.

Claims

1. A method for decoupling tool mark errors during blisk repair, characterized in that: The steps include: Based on the blade repair mark error, the iterative function of the actual undeformed cutting depth is determined according to the fixed point iteration method. for: Among them, a k 、a k+1 are the actual undeformed cutting depths at the kth and k+1th iterations, respectively. e is the target cutting depth, Δd is the tool mark error, and f is the tool deformation error function; Based on the Mueller iteration method, iterative function The solution is performed to obtain the actual undeformed cutting depth a when the iterative function converges; then, based on the actual undeformed cutting depth a, the workpiece positioning error and the tool deformation error are determined to achieve the decoupling of the tool mark error.

2. The method for decoupling tool mark errors during blisk repair according to claim 1, characterized in that: The iterative function based on the Mueller iteration method Solve, including: The iterator function The accelerated iterative formula is transformed into an accelerated iterative formula, and then the accelerated iterative formula is solved based on the Mueller iteration method; the accelerated iterative formula is: Among them, the parameter ω=F[a k ,a k-1 ]+F[a k ,a k-2 ]-F[a k-1 ,a k-2 ], a k-1 、a k-2 are the actual undeformed cutting depths at the k-1th and k-2th iterations, respectively; F represents the difference quotient; and sign represents the sign function.

3. The method for decoupling tool mark errors during blisk repair according to claim 2, characterized in that: When solving the accelerated iteration formula based on the Mueller iteration method, the initial value of the actual undeformed cutting depth is determined as follows: Let the initial workpiece positioning error e h0 =Δd, and then we get a1=a e -e h0 ; Then, according to the iterative function, a2 and a3 are calculated.

4. The method for decoupling tool mark errors during blisk repair according to claim 1, characterized in that: The method of determining the workpiece positioning error and the tool deformation error based on the actual undeformed cutting depth a includes: after determining the actual undeformed cutting depth a, the tool deformation error e f =f(a); workpiece positioning error e h =Δd-e f .

5. The method for decoupling tool mark errors during blisk repair according to any one of claims 1 to 4, characterized in that: The tool deformation error function f is a nonlinear function of the actual undeformed cutting depth, which is calculated by the machining dynamics equation.

6. The method for decoupling tool mark errors during blisk repair according to any one of claims 1 to 4, characterized in that: Obtain the blade joint mark error after repair in advance, including: The scanned point cloud of the repaired area of ​​the damaged blade of the integral blisk is obtained and aligned with the corresponding reference model point cloud. The aligned reference model point cloud and the scanned point cloud are compared to obtain the tool mark error of each tool position after the blade is repaired.

7. The method for decoupling tool mark errors during blisk repair according to claim 6, characterized in that: Register the scanned point cloud with the corresponding reference model point cloud, including: The reference model point cloud is preliminarily adjusted through the affine transformation model to align it with the scanned point cloud; The reference model point cloud is finely adjusted through a Gaussian mixture model-based registration method to ensure accurate alignment between the reference model point cloud and the scanned point cloud.

8. A tool mark error decoupling system for repairing an integral blade disk, characterized in that: The method comprises a processor configured to execute the method for decoupling tool mark errors during repair of an integral blade disk according to any one of claims 1 to 7.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method for decoupling tool mark errors during blisk repair according to any one of claims 1 to 7 is implemented.

10. A computer program product, characterized in that The invention comprises a computer program, which, when executed by a processor, implements the method for decoupling tool mark errors during repair of an integral blade disk according to any one of claims 1 to 7.

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