Aerospace blade ceramic core trimming path consistency evaluation method based on point cloud segmentation

Abstract

The application is based on the aerofoil ceramic core trimming path consistency evaluation method based on point cloud segmentation, which comprises the following steps: firstly, obtaining the ceramic core point cloud data and the elliptical hole trimming path, preliminarily segmenting the point cloud near the elliptical hole, then completing the establishment of the local coordinate system based on RANSAC, realizing the coordinate conversion of the point cloud near the elliptical hole from the world coordinate system to the local coordinate system, then establishing the elliptical hole arc chamfer model under the local coordinate system, realizing the point cloud segmentation and model fitting of the elliptical hole arc chamfer based on particle filtering, and finally completing the aerofoil ceramic core trimming path consistency evaluation combined with the model parameters and the trimming path. The application simultaneously considers the influence of the shrinkage deformation of the ceramic core and defects such as burrs, flash and hole blockage on the parameter fitting and point cloud segmentation, and the influence of the position deviation of the path points and the deviation of the laser trimming direction on the alignment degree of the path edges, thereby improving the accuracy, robustness and reliability of the path consistency evaluation, and meeting the accuracy requirements of the feedback index for improving the trimming path generation algorithm.

Description

Technical Field

[0001] This invention belongs to the field of three-dimensional vision-guided laser processing technology, specifically involving a method for evaluating the consistency of the machining path of ceramic cores for aero-engine blades based on point cloud segmentation. Background Technology

[0002] Ceramic cores are transitional components used in investment casting to form the cavities of cast parts. They are key components for forming complex blade cavities and ensuring dimensional accuracy, and are widely used in the zero-margin precision casting of single-crystal hollow turbine blades and guide vanes for aero-engines. With the continuous improvement of aero-engine design specifications in thrust, thrust-to-weight ratio, and fuel consumption, the high-temperature resistance of high-pressure turbine blades is becoming increasingly demanding. Ceramic cores are crucial components for improving the air-cooling structure of blades, increasing blade cooling efficiency, and thus enhancing blade temperature resistance. Developing precision manufacturing technology for ceramic cores is of great significance for improving aero-engine performance.

[0003] Currently, hot die casting is widely used in the preparation of ceramic cores. However, due to factors such as die casting process parameters and the parting line clearance of the die casting mold, cast ceramic cores often have defects such as burrs, flash, and hole blockage. Therefore, it is necessary to modify the ceramic cores for aero-engine blades. Furthermore, because ceramic core materials are fragile and hot die-cast ceramic cores shrink and deform during cooling, it is difficult to modify them using traditional machining equipment. Therefore, the industry currently mainly uses manual modification, but this method suffers from low yield and low production efficiency, failing to meet the needs of large-scale precision casting of blades. Since ultrafast laser processing technology and 3D vision-guided processing technology have significant advantages in non-contact and flexible manufacturing, it is proposed to achieve automated modification of ceramic cores using ultrafast lasers, 3D vision, and multi-axis machine tools.

[0004] In the field of 3D vision-guided laser processing, a visual guidance path is generated before the actual processing of the workpiece. For laser shaping of ceramic cores, the alignment between the shaping path and the actual edge of the ceramic core significantly affects the final shaping quality. Path consistency refers to the consistency of distance between the actual edge and the shaping line determined by the path points and the laser shaping direction. It is an important indicator for measuring the alignment between the shaping path and the actual edge of the ceramic core, as well as the degree of deviation between the processed features and the actual features. Currently, path consistency evaluation methods generally calculate the root mean square error between point pairs. However, the nearest neighbor matching method, which does not consider feature deviations, is used to determine the correspondence between points. Furthermore, due to the complex structure, anisotropic shrinkage deformation, and lack of accurate clamping and positioning references of ceramic cores, it cannot be guaranteed that the matched points can effectively represent the actual edge. Moreover, this method only considers the distance error between point pairs and does not consider the deviation of the laser shaping direction, thus failing to effectively judge the matching degree between the shaping path and the actual edge in terms of size, shape, and pose, and cannot help improve the accuracy of the shaping path generation algorithm.

[0005] Therefore, there is an urgent need to propose a new method for evaluating the consistency of the ceramic core modification path for aero-engine blades. This method should ensure the effectiveness of the comparison points in representing the actual edges of the ceramic core, comprehensively consider the deviation between the path point positions and the laser modification direction, and thus effectively measure the degree of deviation between the processed features and the actual features. Simultaneously, it should meet the accuracy requirements of the feedback index used to improve the modification path generation algorithm, thereby effectively improving overall processing consistency and accelerating algorithm research and equipment iteration. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, this invention provides a method for evaluating the consistency of the modification path of the ceramic core of aero-engine blades based on point cloud segmentation, which is of great significance for improving the accuracy of the modification path generation algorithm.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for evaluating the consistency of the modification path of ceramic core for aero-engine blades based on point cloud segmentation includes the following steps:

[0009] 1) Use a 3D scanner to acquire point cloud data of ceramic cores on the machine tool, and obtain elliptical hole shaping path information of ceramic cores based on the scanned point cloud data;

[0010] 2) Based on the elliptical hole shaping path information, the ceramic core scanning point cloud is initially segmented to obtain the point cloud D near the elliptical hole. i ;

[0011] 3) Use the RANSAC algorithm to analyze the point cloud D near the elliptical aperture. iPerform plane segmentation, and combine the points in the segmented plane with the plane normal vector. Establish a local coordinate system for each elliptical aperture and complete the point cloud D near the elliptical aperture. i Coordinate transformation from global to local;

[0012] 4) The geometric modeling of the elliptical hole circular arc chamfer surface is performed using the cosine theorem in the local coordinate system. The modeling process is simplified based on the local coordinate system rotation, the geometric properties of the ellipse, and the normal vector attribute in the point cloud data. The simplified model parameters are the Euler angles φ, ψ, and θ of the local coordinate system rotation, the radius r of the circular arc chamfer, the length R of the minor axis of the ellipse, and the y coordinate b and z coordinate c of the center point B of the ellipse in the local coordinate system.

[0013] 5) Using the model parameters of the chamfered arc of the elliptical aperture as the state variables, a function based on the state change as the motion model, and the model parameter estimation based on the least squares method as the observation model, the point cloud D near the elliptical aperture is used as the model parameters. i Using the local coordinates as observation data, and the ratio of the number of internal points to the total number of points ξ as the weight update index, point cloud segmentation and model fitting for the chamfer of the elliptical hole are realized based on the particle filter framework.

[0014] 6) Evaluate the consistency of the shaping path using the model fitting parameters of the chamfered elliptical hole after point cloud segmentation and the shaping path information of the elliptical hole.

[0015] In step 1), the ceramic core is clamped in the machine tool fixture. Point cloud data of the ceramic core is acquired using a 3D scanner and a machine tool rotary table. Based on the scanned point cloud data, a shaping path generation algorithm is used to obtain the elliptical hole shaping path of the ceramic core. The shaping path information includes the shaping path points and the laser shaping direction.

[0016] In step 2), the segmentation criterion for initially segmenting the point cloud near the elliptical aperture based on the elliptical aperture shaping path information is: using the center point P of the elliptical aperture shaping path points as the segmentation criterion. i Based on the laser shaping direction For the axis, the aperture threshold h i A cylindrical surface is defined with respect to the diameter of the base. All points within the cylindrical surface are divided into a point cloud D near the elliptical hole. i .

[0017] In step 3), the RANSAC algorithm is used to transform the point cloud D near the elliptical hole in step 2). i Two planes are divided, using plane B located on the back of the ceramic core. i As a reference plane for establishing a local coordinate system;

[0018] The local coordinate system of the elliptical hole is defined as follows: with plane B i Geometric center of interior point With the origin O, the direction is towards the plane B inside the hole. i normal vector Using the X-axis as the axis and the normal vector as the axis of reference. With laser shaping direction The opposite vectors of the vector sum lie in plane B. i The projection vector on the plane is the Y-axis, and the Z-axis is determined by the right-hand rule;

[0019] Point cloud D near the elliptical aperture i The coordinate transformation from global to local specifically involves converting the point cloud coordinates in the world coordinate system to the point cloud coordinates in the local coordinate system of the elliptical aperture.

[0020] In step 4), the specific method for geometrically modeling the elliptical hole chamfered surface using the cosine theorem in the local coordinate system is as follows: Based on the local coordinate system established in step 3), select any point T on the chamfered surface. The center of the arc containing point T is point S, and the center point of the ellipse formed by the centers of all arcs is point B. Construct the geometric model in ΔSBT using the cosine theorem as follows:

[0021] |BT| 2 =|ST| 2 +|SB| 2 +2*|ST|*|SB|*cos∠TSB

[0022] The elliptical hole chamfer model has seven parameters: Euler angles φ, ψ, and θ for local coordinate system rotation; chamfer radius r; minor axis length R; and the y-coordinate b and z-coordinate c of the ellipse center point B in the local coordinate system. Points T, B, and S are respectively located in the local coordinate system as T(x,y,z) and B(r,b,c). The eccentric angle α of the ellipse can be derived from plane B. i normal vector Laser shaping direction And the y-coordinates (normal_y) and z-coordinates (normal_z) of the normal vector of point T on the chamfered surface in the local coordinate system are calculated using the following formulas:

[0023]

[0024] In step 5), the specific method for point cloud segmentation and model fitting of the elliptical aperture chamfered corner based on the particle filter framework is as follows: the state variables are defined as the elliptical aperture chamfered corner model parameters:

[0025]

[0026] The motion model is defined as a multivariate mixture Gaussian distribution function based on the state changes:

[0027]

[0028]

[0029] The observation model is defined as the least squares estimation model parameters. Since the elliptical hole chamfer model established in step 4) is a nonlinear model, the Gauss-Newton method is used for linear approximation solution.

[0030] In step 5), the particle filter framework is as follows:

[0031] (1) Initialization: When k=0, N samples with weights of 1 / N are drawn from the prior distribution p(x0) to form the initial particle set. Corresponding particle weights

[0032] (2) Sampling: When k≠0, select the motion model As an importance density function Mid-sampling to obtain particle sets

[0033] (3) Particle weight update: update the point cloud D near the elliptical hole in the local coordinate system. i Substitute the points into the elliptical hole arc chamfer model, select points with a distance less than a threshold as observation points, substitute these observation points into the observation model to update the parameters of the elliptical hole arc chamfer model, and select the point set C within the model. k Record the ratio ξ of the number of points in the record to the total number of points, and update the formula using weights. Update the particle weights, where λ is the adjustment parameter;

[0034] (4) Resampling: Select the system resampling method to obtain the resampled particle set. The corresponding particle weights are

[0035] (5) Output: Select the particle with the largest ratio ξ between the number of interior points and the total number of points, and output the corresponding set of interior points C. k and model fitting parameters;

[0036] (6) Convergence check: If the algorithm convergence condition is met, stop the iteration; otherwise, repeat steps (2)-(6).

[0037] In step 6), the specific steps for evaluating the consistency of the shaping path are as follows: In the local coordinate system, the coordinates of the center point B of the ellipse and the expression of the plane containing the ellipse are obtained using the model fitting parameters. The center point P of the shaping path is along the laser shaping direction. The projection of the ellipse onto the plane is point P′, and the vector from the center point B of the ellipse to the projection point P′ is... The consistency of the evaluation path was assessed; the statistical analysis method used to assess the consistency of the path was to obtain the evaluation data. The mean, standard deviation, and variance of the modulus.

[0038] The present invention has at least the following beneficial technical effects:

[0039] (1) Since the present invention uses a large number of elliptical holes on the ceramic core that are widely distributed and have significant characteristics to evaluate the consistency of the modification path of the ceramic core of the aero-engine blade, the accuracy and reliability of the path consistency evaluation are higher.

[0040] (2) Since the present invention performs model fitting and point cloud segmentation on the chamfer of the elliptical hole, the shrinkage deformation of the ceramic core and defects such as burrs, flash, and hole blockage have little effect on the fitting and segmentation effect. Therefore, the present invention has higher feature estimation accuracy and stronger robustness for the actual edge of the ceramic core, and can more effectively measure the degree of deviation between the processing features and the actual features.

[0041] (3) Since the present invention is based on the geometric modeling of the elliptical hole arc chamfered surface using a rotatable local coordinate system, the modeling process is simplified according to the geometric characteristics of the ellipse and the normal vector properties of the point cloud. Furthermore, the RANSAC plane segmentation algorithm is used to initialize the local coordinate system attitude, which reduces the model parameters and the number of algorithm iterations. This reduces the computational complexity and computation time while ensuring computational accuracy.

[0042] (4) Since the present invention is based on the particle filter framework to realize the point cloud segmentation of the elliptical hole arc chamfer, and the motion model is a multivariate mixed Gaussian distribution based on the state change, the algorithm has a stronger ability to fit the parameters of the nonlinear model. Therefore, the model fitting accuracy of the present invention is better and the point cloud segmentation accuracy is higher, which meets the accuracy requirements of the feedback index for improving the shaping path generation algorithm. It plays a positive role in promoting the research of shaping path generation algorithm, improving the overall processing consistency of ceramic cores, and accelerating the iteration of laser shaping equipment.

[0043] (5) Since the path consistency evaluation data of the present invention comes from the elliptical center point of each elliptical hole and the projection point of the path center point along the laser shaping direction, and comprehensively considers the positional deviation of the path point and the directional deviation of the laser processing, the present invention can effectively judge the degree of matching between the shaping path and the actual edge in terms of size, shape, pose, etc. while simplifying the path edge alignment evaluation process. Attached Figure Description

[0044] Figure 1 This is a flowchart illustrating an embodiment of the present invention.

[0045] Figure 2 This is a schematic diagram of the ceramic core to be generated and modified according to an embodiment of the present invention.

[0046] Figure 3 This is a schematic diagram of the modeling of the chamfered corner of the elliptical hole according to an embodiment of the present invention.

[0047] Figure 4 This is a schematic diagram of the point cloud segmentation process based on particle filtering for elliptical aperture circular bevel.

[0048] Figure 5 The path consistency evaluation result is the ideal modification path of the embodiment of the present invention. Detailed Implementation

[0049] Exemplary embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. These described embodiments are only some, not all, of the embodiments of the present invention. Although exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the invention to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other. The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings, and one embodiment of the present invention will be given.

[0050] Example 1:

[0051] like Figure 1 As shown in the embodiment of the present invention, the method for evaluating the consistency of the modification path of the ceramic core of aero-engine blade based on point cloud segmentation includes the following steps:

[0052] 1) Acquiring Ceramic Core Point Cloud Data and Elliptical Hole Shaping Path: The ceramic core is clamped in the machine tool fixture. A 3D scanner and machine tool rotary table are used to acquire the point cloud data of the ceramic core. Based on the scanned point cloud data, a shaping path generation algorithm is used to obtain the elliptical hole shaping path of the ceramic core. The shaping path information includes the shaping path points and the laser shaping direction. like Figure 2 As shown, the area indicated by the dashed box is the part of the ceramic core to be modified in this embodiment of the invention, which includes 30 elliptical holes. This embodiment of the invention needs to use the alignment degree between the path around the elliptical holes and the actual edge to evaluate the consistency of the overall modification path.

[0053] 2) Preliminary segmentation of the point cloud near the elliptical hole: using the center point P of the elliptical hole shaping path points as the basis. i Based on the laser shaping direction For the axis, the aperture threshold h i A cylindrical surface is defined with respect to the diameter of the base. Points within the cylindrical surface are divided into a point cloud D near the elliptical hole. iBy using KdTree to establish the point cloud topology and perform nearest neighbor search, the efficiency of initial segmentation can be improved.

[0054] 3) Establishment of a local coordinate system based on RANSAC: The RANSAC algorithm is used to establish the local coordinate system D near the elliptical aperture. i For planar segmentation, this method uniformly uses plane B located on the back of the ceramic core. i As a reference plane for establishing a local coordinate system, such as Figure 3 As shown, the origin O of the local coordinate system is plane B. i Geometric center of interior point The X-axis is plane B. i The direction is towards the normal vector inside the hole. The Y-axis is the normal vector. With laser shaping direction The opposite vectors of the vector sum lie in plane B. i The projection vector on the plane is determined by the right-hand rule for the Z-axis. Point cloud D near the elliptical aperture. i Coordinates in the world coordinate system need to be converted to coordinates in the aforementioned local coordinate system.

[0055] 4) Establish the chamfer model for the elliptical hole: such as Figure 3 As shown, the elliptical hole chamfer model of this embodiment is constructed in the local coordinate system established in step 3). Any point T is selected on the chamfer surface, with point S as the center of the arc containing point T, and point B as the center point of the ellipse formed by the centers of all arcs. The formula is constructed in ΔSBT using the law of cosines as follows:

[0056] |BT| 2 =|ST| 2 +|SB| 2 +2*|ST|*|SB|*cos∠TSB

[0057] Let the coordinates of point T on the chamfered surface be (x, y, z) in the local coordinate system, the radius of the chamfer be r, the coordinates of the center point B of the ellipse formed by the centers of the chamfers be (r, b, c) in the local coordinate system, the length of the minor axis of the ellipse be R, and the length of the major axis of the ellipse be r. The coordinates of the center S of the arc containing point T in the local coordinate system are: The formula for determining the eccentric angle α of the ellipse is as follows:

[0058]

[0059] Where normal_y and normal_z represent the y-coordinate and z-coordinate of the normal vector of point T on the chamfered surface in the local coordinate system, respectively.

[0060] The orientation of the elliptical hole chamfer model established in the local coordinate system is fixed. To enable the model to describe changing orientations, Euler angle parameters φ, ψ, and θ need to be added to describe the rotation of the local coordinate system. In summary, the parameters of the elliptical hole chamfer model are simplified to seven: the Euler angles φ, ψ, and θ of the local coordinate system rotation; the chamfer radius r; the minor axis length R of the ellipse; and the y-coordinate b and z-coordinate c of the ellipse center point B in the local coordinate system.

[0061] 5) Point cloud segmentation of elliptical aperture chamfer: The model parameters of the elliptical aperture chamfer are used as state variables and defined as follows:

[0062]

[0063] The motion model is based on a multivariate mixture Gaussian distribution function of the state change, as shown in the following formula:

[0064]

[0065]

[0066] The observation model needs to estimate the model parameters based on point cloud data and using the least squares method. Since the elliptical hole chamfer model established in step 4) is a nonlinear model, it needs to be solved linearly using the Gauss-Newton method.

[0067] 6) Path consistency assessment: such as Figure 3 As shown, in the local coordinate system, the coordinates of the ellipse center point B and the expression of the plane containing the ellipse are obtained using the model fitting parameters. The center point P of the shaping path is along the laser shaping direction. Projecting onto the plane containing the ellipse, the vector pointing from the center point B of the ellipse in each elliptical aperture to the projection point P′ is... As evaluation data, and then by obtaining the evaluation data Statistical analysis methods such as the mean, standard deviation, and variance of the modulus length are used to analyze the data and complete the consistency assessment of the modification path of the ceramic core of the aero-engine blade.

[0068] Example 2:

[0069] like Figure 4 As shown, this embodiment provides a point cloud segmentation method for elliptical aperture circular bevels based on particle filtering. It uses the point cloud data, local coordinate system, circular bevel model, state variables, motion model, and observation model provided in Embodiment 1 above. The specific implementation method is as follows:

[0070] (1) Particle initialization: When k=0, N samples with weights of 1 / N are drawn from the prior distribution p(x0) to form the initial particle set. Corresponding particle weights

[0071] (2) Importance sampling based on motion model: When k≠0, the motion model is selected as the importance density function. The particle set is obtained by sampling from the importance density function.

[0072] (3) Rotation of local coordinate system and point cloud coordinate transformation: Based on the Euler angles φ, ψ, θ in the particle state, rotate the local coordinate system established in step 3), and then convert the point cloud coordinates into coordinates under the rotated local coordinate system;

[0073] (4) Observation point selection based on model: Select the point cloud D near the elliptical aperture in the local coordinate system. i Substitute the elliptical hole arc chamfer model and select the point cloud within a certain distance range of the model as observation points;

[0074] (5) Least squares estimation of model parameters: Using the observation points selected in step (4), the model parameters that match the observation points are approximately estimated based on the least squares method and the Gauss-Newton method.

[0075] (6) Filtering interior points based on the updated model: The point cloud D near the elliptical aperture in the local coordinate system is... i Substitute these points into the updated geometric model and select points whose distance from the model is within a threshold as interior points C. k ξ represents the ratio of the number of points recorded to the total number of points.

[0076] (7) Update particle weights based on the number of inliers: The larger the number of inliers, the closer the model parameters are to the true values. Therefore, the weight update formula is as follows:

[0077]

[0078] (8) System resampling: The particle set is resampled according to the system resampling method to obtain the resampled particle set. Corresponding particle weights

[0079] (9) Determine if the convergence condition is met: If the convergence condition is not met, repeat steps (2)-(9); if the convergence condition is met, stop the iteration and output the model parameters and interior point set C when ξ is maximized. k .

[0080] Example 3:

[0081] This embodiment uses the point cloud segmentation-based method for evaluating the consistency of the ceramic core shaping path for aero-engine blades, and the particle filtering-based point cloud segmentation method for chamfering elliptical apertures, provided in Embodiments 1 and 2. It utilizes template point cloud data and an ideal shaping path to achieve consistency evaluation of the ceramic core's ideal shaping path. Since the template point cloud data and the ideal shaping path are directly generated from the CAD design model, the ideal shaping path is theoretically perfectly aligned with the actual edge. The ideal shaping path consistency evaluation data of this embodiment is as follows: Figure 5 As shown, the calculated mean, standard deviation, and variance of the evaluation data are 0.0097 mm, 0.0018 mm, and 0.000003406 mm, respectively. 2 The path consistency evaluation results show that the method of the present invention can effectively determine the degree of matching between the modified path and the actual edge in terms of size, shape, pose, etc., and meets the accuracy requirements of the feedback index for improving the modified path generation algorithm.

[0082] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for evaluating the consistency of the modification path of ceramic core for aero-engine blades based on point cloud segmentation, characterized in that, Includes the following steps: 1) Use a 3D scanner to acquire point cloud data of ceramic cores on the machine tool, and obtain elliptical hole shaping path information of ceramic cores based on the scanned point cloud data; 2) Based on the elliptical hole shaping path information, the ceramic core scanning point cloud is initially segmented to obtain the point cloud D near the elliptical hole. i ; 3) Use the RANSAC algorithm to analyze the point cloud D near the elliptical aperture. i Perform plane segmentation, and combine the points in the segmented plane with the plane normal vector. Establish a local coordinate system for each elliptical aperture and complete the point cloud D near the elliptical aperture. i Coordinate transformation from global to local; 4) The geometric modeling of the elliptical hole circular arc chamfer surface is performed using the cosine theorem in the local coordinate system. The modeling process is simplified based on the local coordinate system rotation, the geometric properties of the ellipse, and the normal vector attribute in the point cloud data. The simplified model parameters are the Euler angles φ, ψ, and θ of the local coordinate system rotation, the radius r of the circular arc chamfer, the length R of the minor axis of the ellipse, and the y coordinate b and z coordinate c of the center point B of the ellipse in the local coordinate system. 5) Using the model parameters of the chamfered arc of the elliptical aperture as the state variables, a function based on the state change as the motion model, and the model parameter estimation based on the least squares method as the observation model, the point cloud D near the elliptical aperture is used as the model parameters. i Using the local coordinates as observation data, and the ratio of the number of internal points to the total number of points ξ as the weight update index, point cloud segmentation and model fitting for the chamfer of the elliptical hole are realized based on the particle filter framework. 6) Evaluate the consistency of the shaping path using the model fitting parameters of the chamfered elliptical hole after point cloud segmentation and the shaping path information of the elliptical hole.

2. The method for evaluating the consistency of the modification path of aero-engine blade ceramic core based on point cloud segmentation according to claim 1, characterized in that, In step 1), the ceramic core is clamped in the machine tool fixture. Point cloud data of the ceramic core is acquired using a 3D scanner and a machine tool rotary table. Based on the scanned point cloud data, a shaping path generation algorithm is used to obtain the elliptical hole shaping path of the ceramic core. The shaping path information includes the shaping path points and the laser shaping direction.

3. The method for evaluating the consistency of the modification path of aero-engine blade ceramic core based on point cloud segmentation according to claim 1, characterized in that, In step 2), the segmentation criterion for initially segmenting the point cloud near the elliptical aperture based on the elliptical aperture shaping path information is: using the center point P of the elliptical aperture shaping path points as the segmentation criterion. i Based on the laser shaping direction For the axis, the aperture threshold h i A cylindrical surface is defined with respect to the diameter of the base. All points within the cylindrical surface are divided into a point cloud D near the elliptical hole. i .

4. The method for evaluating the consistency of the modification path of aero-engine blade ceramic core based on point cloud segmentation according to claim 1, characterized in that, In step 3), the RANSAC algorithm is used to transform the point cloud D near the elliptical hole in step 2). i Two planes are divided, using plane B located on the back of the ceramic core. i As a reference plane for establishing a local coordinate system; The local coordinate system of the elliptical hole is defined as follows: with plane B i The geometric center O of the interior point ti With the origin O, the direction is towards the plane B inside the hole. i normal vector Using the X-axis as the axis and the normal vector as the axis of reference. With laser shaping direction The opposite vectors of the vector sum lie in plane B. i The projection vector on the plane is the Y-axis, and the Z-axis is determined by the right-hand rule; Point cloud D near the elliptical aperture i The coordinate transformation from global to local specifically involves converting the point cloud coordinates in the world coordinate system to the point cloud coordinates in the local coordinate system of the elliptical aperture.

5. The method for evaluating the consistency of the modification path of aero-engine blade ceramic core based on point cloud segmentation according to claim 1, characterized in that, In step 4), the specific method for geometrically modeling the elliptical hole chamfered surface using the cosine theorem in the local coordinate system is as follows: Based on the local coordinate system established in step 3), select any point T on the chamfered surface. The center of the arc containing point T is point S, and the center point of the ellipse formed by the centers of all arcs is point B. Construct the geometric model in ΔSBT using the cosine theorem as follows: |BT| 2 =|ST| 2 +|SB| 2 +2*|ST||*|SB|*cos∠TSB The elliptical hole chamfer model has seven parameters: Euler angles φ, ψ, and θ for local coordinate system rotation; chamfer radius r; minor axis length R; and the y-coordinate b and z-coordinate c of the ellipse center point B in the local coordinate system. Points T, B, and S are respectively located in the local coordinate system as T(x,y,z) and B(r,b,c). The eccentric angle α of the ellipse can be derived from plane B. i normal vector Laser shaping direction And the y-coordinates (normal_y) and z-coordinates (normal_z) of the normal vector of point T on the chamfered surface in the local coordinate system are calculated using the following formulas:

6. The method for evaluating the consistency of the modification path of aero-engine blade ceramic core based on point cloud segmentation according to claim 1, characterized in that, In step 5), the specific method for point cloud segmentation and model fitting based on the particle filter framework for elliptical aperture chamfered corners is as follows: the state variables are defined as the elliptical aperture chamfered corner model parameters: The motion model is defined as a multivariate mixture Gaussian distribution function based on the state changes: The observation model is defined as the least squares estimation model parameters. Since the elliptical hole chamfer model established in step 4) is a nonlinear model, the Gauss-Newton method is used for linear approximation solution.

7. The method for evaluating the consistency of the modification path of aero-engine blade ceramic core based on point cloud segmentation according to claim 6, characterized in that, The particle filter framework is as follows: (1) Initialization: When k=0, N samples with weights of 1 / N are drawn from the prior distribution p(x0) to form the initial particle set. Corresponding particle weights (2) Sampling: When k≠0, select the motion model As an importance density function Mid-sampling to obtain particle sets (3) Particle weight update: update the point cloud D near the elliptical hole in the local coordinate system. i Substitute the points into the elliptical hole arc chamfer model, select points with a distance less than a threshold as observation points, substitute these observation points into the observation model to update the parameters of the elliptical hole arc chamfer model, and select the point set C within the model. k Record the ratio ξ of the number of points in the record to the total number of points, and update the formula using weights. Update particle weights; (4) Resampling: Select the system resampling method to obtain the resampled particle set. The corresponding particle weights are (5) Output: Select the particle with the largest ratio ξ between the number of interior points and the total number of points, and output the corresponding set of interior points C. k and model fitting parameters; (6) Convergence check: If the algorithm convergence condition is met, stop the iteration; otherwise, repeat steps (2)-(6).

8. The method for evaluating the consistency of the modification path of aero-engine blade ceramic core based on point cloud segmentation according to claim 1, characterized in that, In step 6), the specific steps for evaluating the consistency of the shaping path are as follows: In the local coordinate system, the coordinates of the center point B of the ellipse and the expression of the plane containing the ellipse are obtained using the model fitting parameters. The center point P of the shaping path is along the laser shaping direction. The projection of the ellipse onto the plane is point P′, and the vector from the center point B of the ellipse to the projection point P′ is... The consistency of the evaluation path was assessed; the statistical analysis method used to assess the consistency of the path was to obtain the evaluation data. The mean, standard deviation, and variance of the modulus.

Images