A method for rapid allocation of allowances in die forgings for aerospace structural components

Abstract

This invention belongs to the field of CNC machining technology, specifically relating to a method for rapid allocation of allowance in forgings of aerospace structural components. Based on the ICP algorithm, this method first measures the actual position of the forging blank corresponding to each contour point in the theoretical outline point set of the forging in the initial machining coordinate system, forming an actual position point set. Then, iteratively updates the initial machining coordinate system attitude with small step increments, and projects the actual position point set onto the new machining coordinate system to calculate the distance to the remaining theoretical outline point sets until the change is minimized, thus completing the optimal machining coordinate system attitude adjustment.

Description

Technical Field

[0001] This invention belongs to the field of CNC machining technology, specifically relating to a method for rapid allocation of allowances in forgings of aerospace structural components. Background Technology

[0002] Aerospace forgings are a typical complex blank type used in the milling of aerospace structural components, commonly found in components such as slide rails, supports, and frames. During the machining of aerospace forgings, due to die wear and deformation, different batches of blanks produced from the same die exhibit varying degrees of difference in shape. During CNC machining of these forgings, the different shapes of the blanks from different batches, when using the same machining coordinate system, can lead to uneven machining allowances in various directions. This can result in problems such as tool damage from large enveloping allowances and tool breakage from small enveloping allowances, reducing production efficiency. Furthermore, excessive differences in machining allowances on each side can cause the minimum enveloping allowance to fall below the minimum allowance required for heat treatment after rough machining, affecting the yield rate of the parts.

[0003] The traditional method involves marking lines on the incoming forging part based on the theoretical shape template. On-site operators then determine the actual alignment points and an initial machining coordinate system based on the template before conducting trial machining. After the trial machining is completed, the machining coordinate system is adjusted based on the results. This method can only reduce some of the uneven allowance distribution problems, and the template marking places high demands on the operator's skill level. The cumbersome manual operation steps also significantly impact production efficiency.

[0004] In conclusion, a detailed study is needed on the rapid and accurate allocation of allowances in aerospace forgings, and the process operation procedures should be optimized accordingly to improve the processing efficiency and yield of aerospace structural forgings. Summary of the Invention

[0005] Objective: To provide a method for rapid allocation of allowance in forgings of aerospace structural components. Based on the ICP algorithm, the method measures the actual position of the forging blank corresponding to each contour point in the theoretical outline point set of the forging in the initial machining coordinate system, forming an actual position point set. Then, the initial machining coordinate system attitude is iteratively updated with small step increments, and the actual position point set is projected onto the new machining coordinate system to calculate the distance of the remaining theoretical outline point sets until the change is minimal, thus completing the optimal machining coordinate system attitude adjustment.

[0006] Technical solution:

[0007] A method for rapid allocation of allowances in forged aerospace structural components includes:

[0008] Step 1: Establish the theoretical machining coordinate system AxisL for the forging and determine the theoretical outline point set P of the forging;

[0009] Step 2: Develop a program to measure the actual position of P based on AxisL;

[0010] Step 3: Establish an initial machining coordinate system Axis0 on the actual forging blank, and execute the actual position measurement program under Axis0 to determine the actual contour point set Q;

[0011] Step 4: Establish an initial rotation matrix R0 and translation matrix T0, and calculate the rotation matrix R1 and translation matrix T1 that minimize the distance L1 between P and Q using the quaternion method. Adjust the attitude of Axis0 based on R1 and T1 to form the machining coordinate system Axis1 after the first attitude adjustment.

[0012] Step 5, measure each measured point Q in Q obtained under Axis0. i Projecting these points onto Axis1 forms the first iteration's actual contour point set Q1;

[0013] Step 6, calculate each feature measurement point P in P. i Q1 and the intermediate points Q i1 Distance L1

[0014]

[0015] Step 7: Repeat steps 4 and 5 to form the machining coordinate system Axis2 after the second attitude adjustment and the actual contour point set Q2 for the second iteration. Calculate the feature measurement points P in P. i Q at each point between Q2 i2 Distance L2

[0016]

[0017] Step 8: Calculate the difference between L1 and L2;

[0018] Step 9: Repeat steps 4 to 6 for iterative pose adjustment until all feature measurement points P in P are reached. i With the actual contour point set Q after k iterations k Q points in the middle ik Distance L k The distance L after k-1 pose adjustments k-1 The iteration ends when the difference is 0, and the machining coordinate system Axisk at this time is the optimal machining coordinate system.

[0019] Further, step 1 specifically includes:

[0020] Step 1: In the programming environment, establish the theoretical machining coordinate system AxisL for the forging part, and extract n points on the three-dimensional model of the forging part that can describe its shape features under the theoretical machining coordinate system AxisL to form the theoretical shape contour point set P.

[0021] Further, step 3 specifically involves:

[0022] In the actual machining environment, an initial machining coordinate system Axis0 is established on the actual die forging blank, and an actual position measurement program is executed under the initial machining coordinate system Axis0 to complete the measurement of each feature point P in the theoretical outline point set P. i The corresponding actual contour point Q i The measurements are taken to form the actual contour point set Q.

[0023] Furthermore, in step 4, the rotation matrix R0 is initialized as the identity matrix, the translation vector T0 is set as the zero vector, and the number of iterations is set to 0.

[0024] Further, in step 1, the contour point set P is determined as follows:

[0025] After projecting the three-dimensional digital model of the forging part along the Z-axis of the theoretical machining coordinate system AxisL onto the XY plane, the maximum outer contour curve of the projection plane is extracted. Discrete points P1, P2, ... P1 are then extracted on the maximum outer contour curve at intervals of 100 mm. i ...P n Form the theoretical outline point set P.

[0026] Furthermore, in step 3, an initial machining coordinate system Axis0 is established under the actual reference point, specifically as follows:

[0027] The initial machining coordinate system Axis0 is established based on the relative positional relationship between the theoretical machining coordinate system AxisL described in step 1 and the three-dimensional model of the forging. Specifically, a theoretical reference point is selected on the three-dimensional model of the forging, and an actual reference point is established on the actual workpiece based on the workpiece reference point and the outline of the three-dimensional model of the forging. The initial machining coordinate system Axis0 under the actual reference point is established based on the relative positional relationship between the theoretical reference point and the theoretical coordinate system AxisL.

[0028] Furthermore, in step 4,

[0029]

[0030] q = [q0 q1 q2 q3] T (4)

[0031] In formula (4), q is a four-dimensional symmetric matrix K constructed from the covariance matrix K of the point set P under the theoretical machining coordinate system AxisL and the point set Q under the initial machining coordinate system Axis0. T The eigenvectors corresponding to the largest eigenvalue, q0, q1, q2, and q3, are the four component vectors of q, which are the rotation angle, the x-component, y-component, and z-component of the rotation axis vector, respectively.

[0032] Furthermore, the covariance matrix K of P and Q is expressed as follows:

[0033]

[0034] In formula (5), n is the total number of measured feature points on the forging, and μ P With μ Q The two-dimensional centroids of point sets P and Q are μ, respectively. P With μ Q The expression is:

[0035]

[0036] In formula (6), Xi and Yi correspond to the X and Y coordinates of the i-th point in the point set P under the theoretical machining coordinate system AxisL, respectively. In formula (7), Xi and Yi correspond to the X and Y coordinates of the i-th point in the point set Q under the initial machining coordinate system Axis0, respectively.

[0037] Furthermore, in step 7, the four-dimensional symmetric matrix K T The expression is:

[0038]

[0039] In formula (8), K11, K12, K13, ... are the data corresponding to each row and column of the covariance matrix K. For example, K11 is the data in the first row and first column of the covariance matrix K.

[0040] Furthermore, in step 9, the optimal rotation matrix R is solved. k Translation matrix T k The objective function is:

[0041] R k =R k-1 R (10)

[0042] T k =R k T+T k-1 (11)

[0043] In formulas (10) and (11), k is the number of iterations required for the rotation matrix R and the translation matrix T to reach the optimal solution.

[0044] Beneficial effects:

[0045] Through practical verification, it can be seen that the rapid allocation method for aerospace die forgings introduced in this paper is not only simple to operate, highly reliable in calculation, and stable in the accuracy of allocation, but also, compared with traditional methods, does not rely on the experience of technical personnel. It scientifically and efficiently calculates the allocation of aerospace die forgings, effectively reducing the probability of quality problems caused by uneven allocation of the parts and ensuring the product quality of the parts. Attached Figure Description

[0046] Figure 1 Schematic diagram of the die forging model;

[0047] Figure 2 Schematic diagram of feature measurement points of the die forging model;

[0048] Explanation of reference numerals in the attached figures:

[0049] 1-Theoretical coordinate system;

[0050] 2-Forging blank model;

[0051] 3-Measurement points of the forging model features. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are only some, not all, of the embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application. The embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0053] In the description of this invention, it should be understood that the terms "center", "axial", "vertical", "upper", "lower", "upper end", "bottom end", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this invention.

[0054] like Figure 1 and Figure 2 The present invention provides a method for rapid allocation of allowances in forged aerospace structural components, comprising:

[0055] Step 1: In the programming environment, establish the theoretical machining coordinate system AxisL for the forging part, and extract n points on the three-dimensional model of the forging part that can describe its shape features under the theoretical machining coordinate system AxisL to form the theoretical shape contour point set P.

[0056] Step 2: In the programming environment, compile a program to measure the actual position of the theoretical shape contour point set P based on the theoretical machining coordinate system AxisL;

[0057] Step 3: In the actual machining environment, establish an initial machining coordinate system Axis0 on the actual forging blank, and execute the actual position measurement program under the initial machining coordinate system Axis0 to complete the measurement of each feature point P in the theoretical outline point set P. i The corresponding actual contour point Q i The measurements are taken to form the actual contour point set Q;

[0058] Step 4: Establish an initial rotation matrix R0 and translation matrix T0, and calculate the rotation matrix R1 and translation matrix T1 that minimize the distance L1 between the theoretical outline point set P and the actual outline point set Q using the quaternion method. Adjust the orientation of the initial machining coordinate system Axis0 according to the rotation matrix R1 and translation matrix T1, so that its rotation value around its own Z coordinate axis and its translation value along the X and Y directions of its origin form the machining coordinate system Axis1 after the first orientation adjustment.

[0059] Step 5: Measure each measured point Q in the actual contour point set Q obtained under the initial machining coordinate system Axis0. i The first iteration's actual contour point set Q1 is formed by projecting the points onto the machining coordinate system Axis1 after the initial attitude adjustment.

[0060] Step 6: Calculate the feature measurement points P in the theoretical outline point set P. i The points Q between the actual contour point set Q1 in the first iteration and the intermediate points Q i1 Distance L1

[0061]

[0062] Step 7: Repeat steps 4 and 5 to form the machining coordinate system Axis2 after the second attitude adjustment and the actual contour point set Q2 for the second iteration. Calculate the feature measurement points P in the theoretical shape contour point set P. i The intermediate points Q of the actual contour point set Q2 in the second iteration i2 Distance L2

[0063]

[0064] Step 8: Calculate the difference between L1 and L2;

[0065] Step 9: Repeat steps 4, 5, and 6 to iterate and adjust the pose until all feature measurement points P in the theoretical outline point set P are reached. i With the actual contour point set Q after k iterations k Q points in the middle ik Distance L k The distance L after k-1 pose adjustments k-1 The iteration ends when the difference is 0, and the machining coordinate system Axisk at this time is the optimal machining coordinate system.

[0066] In step 1, the three-dimensional digital model of the forging is projected onto the XY plane along the Z-axis of the theoretical machining coordinate system AxisL, and the maximum outer contour curve of the projection plane is extracted. Discrete points P1, P2, ... P are then extracted on the maximum outer contour curve at intervals of 100mm. i ...P n Form the theoretical outline point set P.

[0067] In step 3, the initial machining coordinate system Axis0 is established based on the relative positional relationship between the theoretical machining coordinate system AxisL described in step 1 and the three-dimensional model of the forging. Specifically, a theoretical reference point is selected on the three-dimensional model of the forging, and an actual reference point is established on the actual workpiece based on the workpiece reference point and the outline of the three-dimensional model of the forging. The initial machining coordinate system Axis0 under the actual reference point is established based on the relative positional relationship between the theoretical reference point and the theoretical coordinate system AxisL.

[0068] In step 4, the rotation matrix R0 is initialized as the identity matrix, the translation vector T0 is set as the zero vector, and the number of iterations is set to 0.

[0069] In step 4, the rotation matrix R1 of point sets P and Q is calculated using the quaternion method, and the objective function is:

[0070]

[0071] q = [q0 q1 q2 q3] T (4)

[0072] In formula (4), q is a four-dimensional symmetric matrix K constructed from the covariance matrix K of the point set P under the theoretical machining coordinate system AxisL and the point set Q under the initial machining coordinate system Axis0. T The eigenvectors corresponding to the largest eigenvalue, q0, q1, q2, q3, are the four component vectors of q, representing the rotation angles, and q1, q2, q3 are the x, y, and z components of the rotation axis vector; further, the covariance matrix K of P and Q is expressed as:

[0073]

[0074] In formula (5), n is the total number of measured feature points on the forging. P With μ Q The two-dimensional centroids of point sets P and Q are μ, respectively. P With μ Q The expression is:

[0075]

[0076] In formula (6), Xi and Yi correspond to the X and Y coordinates of the i-th point in the point set P under the theoretical machining coordinate system AxisL, respectively. In formula (7), Xi and Yi correspond to the X and Y coordinates of the i-th point in the point set Q under the initial machining coordinate system Axis0, respectively.

[0077] In formula (5), the four-dimensional symmetric matrix K is constructed by calculating the covariance matrix K. T .

[0078] A four-dimensional symmetric matrix K T The expression is:

[0079]

[0080] In formula (8), K11, K12, K13, ... are the data corresponding to each row and column of the covariance matrix K. For example, K11 is the data in the first row and first column of the covariance matrix K.

[0081] In step 4, the translation matrix T1 for point sets P and Q is calculated.

[0082] T1 = μ Q -R1μ P (9)

[0083] In step 4, the orientation of the initial machining coordinate system Axis0 is adjusted according to the rotation matrix R1 and the translation matrix T1 to form the machining coordinate system Axis1 after the first orientation adjustment.

[0084] In step 5, the first iteration of the actual contour point set Q1 is formed under the initial processing coordinate system Axis1.

[0085] In step 9, the data points Pi and the actual contour point set Q in the first iteration under the machining coordinate system Axis1 are calculated. i1 The distance L1 between each point is iterated by rotating the rotation matrix R and translating the translation matrix T until L is reached. k The distance L after k-1 pose adjustments k-1 The iteration ends when the difference is 0. Find the optimal rotation matrix R. k Translation matrix T k The objective function is:

[0086] R k =R k-1R (10)

[0087] T k =R k T+T k-1 (11)

[0088] In formulas (10) and (11), k is the number of iterations required for the rotation matrix R and translation matrix T to reach the optimal solution. The machining coordinate system Axisk at this point is the optimal machining coordinate system.

[0089] The following detailed explanation uses aerospace structural rail components as an example.

[0090] like Figure 1 and Figure 2 A method for rapid allocation of allowances in forged aerospace structural components includes:

[0091] Step 1: In this test, 40 sets of feature points of the outline of the slide rail part forging blank were selected and output as point set files in the theoretical coordinate system AxisL.

[0092] Step 2: Fix the actual forging part on the worktable. In the machine tool, use a 3D measurement probe to generate a machining coordinate system Axis0 based on the theoretical coordinate system AxisL to measure the corresponding points of the theoretical outline feature points of the actual forging part. Record the measured values ​​of the two-dimensional coordinate data of the points in the machining coordinate system Axis0 and generate the point set Q0.

[0093] Step 3: Set the initial rotation matrix R and translation matrix T.

[0094] Calculate the two-dimensional centroid μ for point sets P and Q respectively. P With μ Q The expression is:

[0095]

[0096] Based on the two-dimensional centroid μ P With μ Q Calculate the covariance matrix K of P and Q, expressed as:

[0097]

[0098] Based on the covariance matrix K, calculate the four-dimensional symmetric matrix K constructed from the covariance matrix K. T The objective function is:

[0099]

[0100] Based on the four-dimensional symmetric matrix K T Calculate the four-dimensional symmetric matrix K T The eigenvector corresponding to the largest eigenvalue, and the objective function is:

[0101] q = [q0 q1 q2 q3] T (16)

[0102] The rotation matrix R of point sets P and Q is calculated using the quaternion method, with the objective function being:

[0103]

[0104] Calculate the translation matrix T for point sets P and Q, with the objective function being:

[0105] T1 = μ Q -Rμ P (18)

[0106] Calculate the rotation matrix R1 and translation matrix T1 after the first iteration. Based on the rotation matrix R1 and translation matrix T1, generate a new machining coordinate system Axis1 and each measured point Q from the theoretical coordinate system. i The points are projected onto the machining coordinate system Axis1 after the initial attitude adjustment to form the actual contour point set Q1 for the first iteration. The feature measurement points P in the theoretical shape contour point set P are then calculated. i The points Q between the actual contour point set Q1 in the first iteration and the intermediate points Q i1 The distance L1 between them, and the objective function is:

[0107]

[0108] Step 4: Calculate the P values ​​for each feature measurement point according to formula (19). i The points Q between the actual contour point set Q1 in the first iteration and the intermediate points Q i1 The distance L1 between them is 10.83. Calculate L iteratively using the method described above and fill it into the table below.

[0109] The calculated values ​​of min: f(R, T) during the iteration process are shown in the table below:

[0110]

[0111] When the number of iterations k = 16, L is satisfied. 16 -L 15 =0, set the rotation matrix R 16 Translation matrix T 16 To determine the optimal rotation and translation matrix, the machining coordinate system Axis16 is set as the actual machining coordinate system.

[0112] The calculation for the rapid allocation of allowances for aerospace forgings has been completed.

[0113] Through practical verification, it can be seen that the rapid allocation method for aerospace die forgings introduced in this paper is not only simple to operate, highly reliable in calculation, and stable in the accuracy of allocation, but also, compared with traditional methods, does not rely on the experience of technical personnel. It scientifically and efficiently calculates the allocation of aerospace die forgings, effectively reducing the probability of quality problems caused by uneven allocation of the parts and ensuring the product quality of the parts.

[0114] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for rapid allocation of allowances in forged aerospace structural components, characterized in that, include: Step 1: Establish the theoretical machining coordinate system AxisL for the forging and determine the theoretical outline point set P of the forging; Step 2: Develop a program to measure the actual position of P based on AxisL; Step 3: Establish an initial machining coordinate system Axis0 on the actual forging blank, and execute the actual position measurement program under Axis0 to determine the actual contour point set Q; Step 4: Establish an initial rotation matrix R0 and translation matrix T0, and calculate the rotation matrix R1 and translation matrix T1 that minimize the distance L1 between P and Q using the quaternion method. Adjust the attitude of Axis0 based on R1 and T1 to form the machining coordinate system Axis1 after the first attitude adjustment. Step 5, measure each measured point Q in Q obtained under Axis0. i Projecting these points onto Axis1 forms the first iteration's actual contour point set Q1; Step 6, calculate each feature measurement point P in P. i Q1 and the points between Q1 i1 Distance L1 Step 7: Repeat steps 4 and 5 to form the machining coordinate system Axis2 after the second attitude adjustment and the actual contour point set Q2 of the second iteration. Calculate the feature measurement points P in P. i Q at each point between Q2 i2 Distance L2 Step 8: Calculate the difference between L1 and L2; Step 9: Repeat steps 4 to 6 for iterative pose adjustment until all feature measurement points P in P are reached. i With the actual contour point set Q after k iterations k Q points in the middle ik Distance L k The distance L after k-1 pose adjustments k-1 The iteration ends when the difference is 0, and the machining coordinate system Axisk at this time is the optimal machining coordinate system.

2. The method according to claim 1, characterized in that, Step 1 specifically includes: Step 1: In the programming environment, establish the theoretical machining coordinate system AxisL for the forging part, and extract n points on the three-dimensional model of the forging part that can describe its shape features under the theoretical machining coordinate system AxisL to form the theoretical shape contour point set P.

3. The method according to claim 1, characterized in that, Step 3, specifically: In the actual machining environment, an initial machining coordinate system Axis0 is established on the actual die forging blank, and an actual position measurement program is executed under the initial machining coordinate system Axis0 to complete the measurement of each feature point P in the theoretical outline point set P. i The corresponding actual contour point Q i The measurements are taken to form the actual contour point set Q.

4. The method according to claim 1, characterized in that, In step 4, the rotation matrix R0 is initialized as the identity matrix, the translation vector T0 is set as the zero vector, and the number of iterations is set to 0.

5. The method according to claim 2, characterized in that, In step 1, the contour point set P is determined as follows: After projecting the three-dimensional digital model of the forging part along the Z-axis of the theoretical machining coordinate system AxisL onto the XY plane, the maximum outer contour curve of the projection plane is extracted. Discrete points P1, P2, ... P1 are then extracted on the maximum outer contour curve at intervals of 100 mm. i ...P n Form the theoretical outline point set P.

6. The method according to claim 3, characterized in that, In step 3, the initial machining coordinate system Axis0 under the actual reference point is established, specifically as follows: The initial machining coordinate system Axis0 is established based on the relative positional relationship between the theoretical machining coordinate system AxisL described in step 1 and the three-dimensional model of the forging. Specifically, a theoretical reference point is selected on the three-dimensional model of the forging, and an actual reference point is established on the actual workpiece based on the workpiece reference point and the outline of the three-dimensional model of the forging. The initial machining coordinate system Axis0 under the actual reference point is established based on the relative positional relationship between the theoretical reference point and the theoretical coordinate system AxisL.

7. The method according to claim 1, characterized in that, In step 4, q=[q0 q1 q2 q3] T (4) In formula (4), q is a four-dimensional symmetric matrix K constructed from the covariance matrix K of the point set P under the theoretical machining coordinate system AxisL and the point set Q under the initial machining coordinate system Axis0. T The eigenvectors corresponding to the largest eigenvalue, q0, q1, q2, and q3, are the four component vectors of q, which are the rotation angle, the x-component, y-component, and z-component of the rotation axis vector, respectively.

8. The method according to claim 7, characterized in that, The covariance matrix K of P and Q is expressed as follows: In formula (5), n is the total number of measured feature points on the forging, and μ P With μ Q The two-dimensional centroids of point sets P and Q are μ, respectively. P With μ Q The expression is: In formula (6), Xi and Yi correspond to the X and Y coordinates of the i-th point in the point set P under the theoretical machining coordinate system AxisL, respectively. In formula (7), Xi and Yi correspond to the X and Y coordinates of the i-th point in the point set Q under the initial machining coordinate system Axis0, respectively.

9. The method according to claim 8, characterized in that, In step 7, the four-dimensional symmetric matrix K T The expression is: In formula (8), K11, K12, K13, ... are the data corresponding to each row and column of the covariance matrix K. For example, K11 is the data in the first row and first column of the covariance matrix K.

10. The method according to claim 1, characterized in that, In step 9, the optimal rotation matrix R is solved. k Translation matrix T k The objective function is: R k =R k-1 R (10) T k =R k T+T k-1 (11) In formulas (10) and (11), k is the number of iterations required for the rotation matrix R and the translation matrix T to reach the optimal solution.

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