Blade section area five-axis linkage swing sweeping path planning method and system

Abstract

The invention provides a blade section area five-axis linkage swing sweeping path planning method and system, and the method comprises the steps: building a volume model of a measuring head and a grid model of a blade, employing a collision detection algorithm to achieve the collision detection of the blade and the measuring head, and then building a measuring rod-blade contact model to guide the generation of the direction of a measuring rod, and the deviation angle of the directions of the adjacent measuring rods is minimized by adjusting the directions of the measuring rods so as to solve the problem of path sudden change. And fitting the measuring seat path and the measuring tip path into two NURBS curves, and then carrying out fairing and smoothing operations on the two curves by using a double NURBS method to finally obtain a fairing and smooth five-axis linkage sweeping path.

Description

Technical Field

[0001] This invention relates to the technical field of five-axis linkage scanning path planning methods, specifically to a five-axis linkage oscillating scanning path planning method and system for blade cross-section regions. Background Technology

[0002] Complex curved surface components, such as large aircraft blades and integral bladed disks, are key research objects in digital manufacturing. How to perform precise and efficient measurement is currently a research focus. Coordinate measuring machines (CMMs) have advantages such as high measurement accuracy and wide range, and are widely used in the precision measurement of components. Traditional CMMs mainly perform measurements through point-by-point measurement and three-axis scanning measurement. Point-by-point measurement requires approximation-retreat during measurement, which results in a significant amount of non-measurement time and low measurement efficiency. Traditional five-axis measurement simply combines a three-axis CMM with a two-axis indexing probe, keeping the probe angle constant during measurement. Five-axis linkage measurement technology, as an emerging technology, improves the measurement efficiency of complex curved surface components by using a probe to perform high-speed sliding sweeps across the surface of the part being measured to acquire surface data at high speed. A five-axis linkage CMM is based on a traditional three-axis CMM and incorporates a continuously rotating two-axis probe. The probe is equipped with an ultra-light carbon fiber probe rod, enabling high-speed oscillation of the probe rod. During measurement, the three-axis CMM and the two-axis probe can be linked. The specific process is as follows... Figure 1 As shown.

[0003] Traditional coordinate measuring machines (CMMs) paired with PH10 indexing probes require multiple adjustments to the probe direction based on measurement needs, resulting in low measurement efficiency. Furthermore, considering the geometric complexity of the blade cross-section area, slippage and collisions frequently occur in traditional five-axis linkage measurements. Therefore, the path planning process needs to address the slippage problem during five-axis linkage measurement of the blade cross-section area while ensuring interference-free measurement. Traditional methods neglect the characteristic of abrupt changes in curvature in the blade cross-section region (Z. Zhou, Y. Zhang, and K. Tang, 'Sweep scan path planning for efficient freeform surface inspection on five-axis CMM', ComputerAided Design, vol. 77, pp. 1–17, Aug. 2016, doi:10.1016 / j.cad.2016.03.003). Therefore, there is currently no efficient five-axis linkage sweep path planning algorithm for the blade cross-section region. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a five-axis linkage sweeping path planning method and system for blade cross-section regions.

[0005] A five-axis linkage sweeping path planning method for a blade cross-section region provided by the present invention includes:

[0006] Step S1: Construct a probe-blade simulated volume model, and perform collision detection based on the probe-blade simulated volume model to determine the collision boundary;

[0007] Step S2: Optimize the probe direction based on the collision boundary;

[0008] Step S3: Based on the direction of the probe, the five-axis oscillating scan path is initially determined. Then, the obtained probe tip path and probe base path are smoothed and fitted using the dual NURBS method to finally obtain a smooth, smooth, and interference-free five-axis scanning path trajectory.

[0009] The probe-blade simulation volume model includes a probe simulation volume model and a blade cross-sectional area mesh model.

[0010] Preferably, step S1 employs:

[0011] Obtain any line segment SE in the blade cross-section region mesh model, determine the position of the start and end points of line segment SE in the probe simulated volume model coordinate system, and determine the intersection relationship between line segment SE and probe simulated volume model based on the position of the start and end points of line segment SE in the probe simulated volume model coordinate system. When they intersect, it is determined that there is a collision between the current blade and the probe.

[0012] Preferably, the intersection relationship between line segment SE and the probe's simulated volume model is obtained by using the projection intersection method in computer graphics.

[0013] Preferably, step S2 employs:

[0014] Step S2.1: Construct the tip-blade mechanical model;

[0015] Step S2.2: Based on the probe-blade simulation volume model, the continuous probe direction is discretized using an iterative algorithm, and collision detection is performed on the discretized probe direction to extract the probe direction that minimizes the constraints of the probe tip-blade mechanical model.

[0016] Step S2.3: Correct the current direction of the measuring rod by minimizing the deviation between the front and rear measuring rod directions;

[0017] The aforementioned tip-blade mechanical model abstracts the force contact model between the measuring rod and the blade into the interaction relationship between the force-bearing rod and the deformable surface.

[0018] Preferably, step S3 employs the following methods:

[0019] The NRUBS curve of the tip path is PT(t), and its expression is:

[0020]

[0021] Where PTC is the control point of the NURBS probe path, N i,n Let λ be a basis function of the NURBS curve. i The weights are denoted by n; n represents the order.

[0022] The NURBS curve of the probe path is PH(t), and its expression is:

[0023]

[0024] Where PC is the control point of the NURBS coordinate path, N i,nLet λ be a basis function of the NURBS curve. i The weight is denoted by n;

[0025] After obtaining two NURBS curves, the dual NURBS method is used to perform smoothing and synchronization operations on the obtained probe path and probe base path, and finally a smooth, smooth and interference-free five-axis scanning path trajectory is obtained.

[0026] A five-axis linkage sweeping path planning system for a blade cross-section region, provided by the present invention, includes:

[0027] Module M1: Constructs a probe-blade simulated volume model and performs collision detection based on the probe-blade simulated volume model to determine the collision boundary;

[0028] Module M2: Optimizes probe orientation based on collision boundary;

[0029] Module M3: Based on the direction of the probe, the five-axis oscillating scan path is initially determined. Then, the obtained probe tip path and probe base path are smoothed and fitted using the dual NURBS method to finally obtain a smooth, smooth, and interference-free five-axis scanning path trajectory.

[0030] The probe-blade simulation volume model includes a probe simulation volume model and a blade cross-sectional area mesh model.

[0031] Preferably, module M1 adopts:

[0032] Obtain any line segment SE in the blade cross-section region mesh model, determine the position of the start and end points of line segment SE in the probe simulated volume model coordinate system, and determine the intersection relationship between line segment SE and probe simulated volume model based on the position of the start and end points of line segment SE in the probe simulated volume model coordinate system. When they intersect, it is determined that there is a collision between the current blade and the probe.

[0033] Preferably, the intersection relationship between line segment SE and the probe's simulated volume model is obtained by using the projection intersection method in computer graphics.

[0034] Preferably, the module M2 adopts:

[0035] Module M2.1: Constructing the tip-blade mechanical model;

[0036] Module M2.2: Based on the probe-blade simulation volume model, the continuous probe direction is discretized using an iterative algorithm, and collision detection is performed on the discretized probe direction to extract the probe direction that minimizes the constraints of the probe tip-blade mechanical model.

[0037] Module M2.3: Corrects the current probe direction by minimizing the deviation between the front and rear probe directions;

[0038] The aforementioned tip-blade mechanical model abstracts the force contact model between the measuring rod and the blade into the interaction relationship between the force-bearing rod and the deformable surface.

[0039] Preferably, the module M3 adopts:

[0040] The NRUBS curve of the tip path is PT(t), and its expression is:

[0041]

[0042] Where PTC is the control point of the NURBS probe path, N i,n Let λ be a basis function of the NURBS curve. i The weights are denoted by n; n represents the order.

[0043] The NURBS curve of the probe path is PH(t), and its expression is:

[0044]

[0045] Where PC is the control point of the NURBS coordinate path, N i,n Let λ be a basis function of the NURBS curve. i The weight is denoted by n;

[0046] After obtaining two NURBS curves, the dual NURBS method is used to perform smoothing and synchronization operations on the obtained probe path and probe base path, and finally a smooth, smooth and interference-free five-axis scanning path trajectory is obtained.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] 1. This invention establishes a collision model between the probe and the blade before optimizing the probe direction, ensuring no interference during the subsequent probe optimization process;

[0049] 2. This invention establishes a mechanical model of the blade and measuring rod as the basis for generating the direction of the measuring rod to ensure that the measuring rod does not slip or become interrupted when measuring the cross-sectional area of ​​the blade;

[0050] 3. This invention addresses the issue of abnormal tip points that are prone to sudden changes in the high curvature region of the blade tip measurement path. It corrects these abnormal tip points by optimizing the measuring rod angle through an iterative algorithm, which greatly improves the feasibility of the measurement path.

[0051] 4. In the region of high blade curvature, the measuring rod conditions may not be met in the measuring base path and measuring tip path. That is, the length from the measuring tip point to the measuring base point is not equal to the measuring rod length, resulting in abrupt changes and non-smoothness in the generated measuring base path and measuring tip path. The double NURBBS method is used to smooth the measuring base and measuring tip path, ensuring that the trajectory is as smooth as possible without interference.

[0052] 5. This invention establishes a collision model using the probe, probe head volume, and blade mesh model to ensure no interference when solving the probe direction in the subsequent process; it fully utilizes the advantages of five-axis linkage, eliminating the need for approximation and retraction measurements, and can continuously complete the measurement of the blade cross-section area; it establishes a mechanical model of the probe-blade to guide the generation of the probe direction and avoid measurement slippage; and it uses NURBS curves and the double NURBS method to solve for a smooth, interference-free five-axis linkage scanning trajectory. Attached Figure Description

[0053] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0054] Figure 1 A flowchart of the five-axis linkage scanning path planning method for the blade cross-section region.

[0055] Figure 2 This is a structural schematic diagram of the cross-sectional area of ​​a five-axis linkage measuring machine, probe, and blade.

[0056] Figure 3 This is a schematic diagram of the probe volume model and the blade mesh model.

[0057] Figure 4 This is a schematic diagram for determining the intersection of projected spheres.

[0058] Figure 5 This is a schematic diagram of the force model of the measuring rod-blade.

[0059] Figure 6 A schematic diagram for generating a five-axis oscillating sweep path. Detailed Implementation

[0060] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0061] Example 1

[0062] like Figure 1 As shown, this invention provides a five-axis linkage sweeping path planning method for a blade cross-section region, comprising the following steps:

[0063] Step S1: Represent the blade cross-section region using a mesh model to obtain the blade cross-section region mesh model, and construct the probe simulated volume model; construct the probe-blade simulated volume model based on the blade cross-section region mesh model and the probe simulated volume model; consider the geometric intersection of the probe and blade under different region mesh line segments and probe angle conditions. For a specific mesh model line segment SE, the positions of its starting and ending points in the probe simulated volume model coordinate system determine whether it intersects with the model; the probe simulated volume model simplifies the probe into multiple superimposed cylinders. For collision judgment, considering the intersection relationship between cylinders and line segments can be simplified to considering the intersection relationship between the projected circle and the projected line segment, thus obtaining the collision relationship between the blade mesh model and the probe. In practice, the probe volume should be enlarged by 5-10% to ensure sufficient anti-collision margin. The probe simulated volume model refers to the geometric representation of the probe's volume in space, and this geometric model is used to perform collision detection operations with the blade cross-section region mesh model.

[0064] Step S2: To solve for the optimized probe angle, a probe tip-blade mechanical model was established. The force contact model between the probe and blade was abstracted into an interaction model between the force-bearing rod and the deformable surface. Based on the simulated volume model of the probe-blade, an iterative algorithm was used to discretize the continuous probe direction, perform collision detection on the discretized probe direction, and extract the probe direction that minimizes the constraints of the probe tip-blade mechanical model. Considering that there may be abrupt changes between the initially solved probe directions, it is necessary to minimize the deviation constraint on the angle of the probes before and after; that is, after obtaining the probe direction after the force model optimization, the probe direction is corrected by minimizing the deviation of the probe direction before and after to avoid abrupt changes in the probe direction that would cause abrupt changes in the probe tip path. In this embodiment, the probe tip-blade mechanical model guides the generation of the probe direction, and the angle between the probe and the blade should be as small as possible.

[0065] Step S3: Based on the probe direction in Step S2, a preliminary five-axis oscillating scan path is determined. Then, the obtained probe tip path and probe base path are smoothed and fitted using the dual NURBS method to finally obtain a smooth, interference-free five-axis scanning path trajectory. The smoothed probe tip path and the smoothed probe base path constitute an executable five-axis oscillating scan path.

[0066] Specifically, step S1 includes: if a line segment of the blade mesh model intersects with the probe cylinder during measurement, it indicates that a collision has occurred; the collision will occur at this angle and with subsequent increases / decreases in angle, and vice versa.

[0067] Specifically, step S1 includes: according to Figure 2The schematic diagram shows that the five-axis linkage measuring machine is based on a traditional coordinate measuring machine with the addition of a continuously rotating two-axis probe. The measured blade cross-sectional area is obtained by cutting along the stacking axis of the blade.

[0068] For the five-axis CMM and blade cross-sectional area model used, collision detection is performed using geometric volume simulation and blade mesh model. The specific algorithm principle is as follows: Figure 3 As shown. Figure 3 It contains two cylinders of different sizes but coaxial, representing Figure 2 The image shows the probe and the edges of three triangular mesh models in different positions. Edge 1 is located within the length of the large cylinder; edge 2 is located within the length of the small cylinder; and edge 3 is located between the large and small cylinders. Figure 4 As shown, the intersection relationships between the edges and the two cylinders at three different positions are calculated using the projection intersection method in computer graphics. When projected along the axial direction of the cylinders, the intersection relationship between the line segments of the blade model and the two circles determines whether the blade collides with the probe. Specific calculation method:

[0069]

[0070] Where O is the projection point of the central axis; AB is the line segment in the blade cross-section region mesh model; E is the projection of point O onto line segment AB; after solving for the position of E, the collision relationship can be determined by judging the length relationship between OE and the radius. If OE is greater than the radius, there is a collision; if OE is less than the radius, there is no collision. In practice, the volume of the probe should be enlarged by 5-10% to ensure sufficient collision avoidance margin.

[0071] Specifically, step S2 includes: according to Figure 5 A structural diagram, in Figure 2 The force conditions of the measuring rod and blade during measurement are abstracted into a force diagram of the rod and curved surface. For the blade, the influence of its torsional deformation on the measuring rod needs to be considered; in practice, the smallest possible contact angle of the measuring rod should be used. When optimizing the calculation of the measuring rod direction, a small number of path points P are first uniformly sampled along the axis of the cross-sectional region. A local coordinate system LCS can be established at each sampled path point, where v is the measuring rod direction, determined by the angles ω and φ in the local coordinate system.

[0072]

[0073] After obtaining the corresponding probe direction, the rotation angle needs to be discretized within the probe's rotation range, typically using a 1° subdivision. The probe direction with the smallest included angle and no collision is calculated and selected as the initial optimized probe direction. Next, deviation checks are performed on the previous and next probe directions for the obtained probe direction. If the deviation is greater than Δ, adjustments are made to minimize the deviation, ensuring that the generated probe points do not produce large abrupt changes. This process yields a non-slip, collision-free five-axis linkage probe direction and measurement path.

[0074] Specifically, step S3 includes: firstly, based on the probe direction in S2, a five-axis oscillating sweep path is initially determined, and the NURBS curve of the probe tip path is PT(t). The NURBS curve expression of the probe tip path is as follows:

[0075]

[0076] Where PTC is the control point of the NURBS probe path, N i,n Let λ be a basis function of the NURBS curve. i As weight.

[0077] The NURBS curve of the probe path is PH(t), and its expression is:

[0078]

[0079] Where PC is the control point of the NURBS coordinate path, N i,n Let λ be a basis function of the NURBS curve. i The weights are denoted as . After obtaining two NURBS curves, the obtained tip path and base path are smoothed and synchronized using the dual NURBS method, ultimately obtaining a smooth, interference-free five-axis scanning path trajectory.

[0080] The present invention also provides a five-axis linkage sweeping path planning system for a blade cross-section area. The five-axis linkage sweeping path planning system for a blade cross-section area can be implemented by executing the process steps of the five-axis linkage sweeping path planning method for a blade cross-section area. That is, those skilled in the art can understand the five-axis linkage sweeping path planning method for a blade cross-section area as a preferred embodiment of the five-axis linkage sweeping path planning system for a blade cross-section area.

[0081] The final five-axis simultaneous scanning path needs to be obtained synchronously on dual NURBS curves based on both the probe path and the probe tip path. This is to avoid situations where the measurement path cannot be generated in areas of high curvature. Figure 6As shown, the black curve represents the probe base path, indicating the path along which the probe center moves with the coordinate measuring machine (CMM), while the red curve represents the probe tip path, indicating the path along which the probe tip center moves with the probe. This path is the result of synchronizing two NURBS curves (probe base path NURBS and probe tip path NURBS) using the dual NURBS method. The probe base path and probe tip path optimized by the dual NURBS method are smoother and maintain interference-free operation during the measurement process.

[0082] Those skilled in the art will understand that, besides implementing the system and its various devices, modules, and units provided by this invention in the form of purely computer-readable program code, the same functions can be achieved entirely through logical programming of the method steps, making the system and its various devices, modules, and units of this invention function in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers. Therefore, the system and its various devices, modules, and units provided by this invention can be considered as a hardware component, and the devices, modules, and units included therein for implementing various functions can also be considered as structures within the hardware component; alternatively, the devices, modules, and units for implementing various functions can be considered as both software modules implementing the method and structures within the hardware component.

[0083] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for planning the five-axis linkage sweeping path of a blade cross-section region, characterized in that, include: Step S1: Construct a probe-blade simulated volume model, and perform collision detection based on the probe-blade simulated volume model to determine the collision boundary; Step S2: Optimize the probe direction based on the collision boundary; Step S3: Based on the direction of the probe, the five-axis oscillating scan path is initially determined. Then, the obtained probe tip path and probe base path are smoothed and fitted using the dual NURBS method to finally obtain a smooth, smooth, and interference-free five-axis scanning path trajectory. The probe-blade simulation volume model includes a probe simulation volume model and a blade cross-sectional area mesh model.

2. The five-axis linkage sweeping path planning method for the blade cross-section region according to claim 1, characterized in that, Step S1 adopts the following: Obtain any line segment SE in the blade cross-section region mesh model, determine the position of the start and end points of line segment SE in the probe simulated volume model coordinate system, and determine the intersection relationship between line segment SE and probe simulated volume model based on the position of the start and end points of line segment SE in the probe simulated volume model coordinate system. When they intersect, it is determined that there is a collision between the current blade and the probe.

3. The five-axis linkage sweeping path planning method for the blade cross-section region according to claim 2, characterized in that, The intersection relationship between line segment SE and the simulated volume model of the probe is obtained by using the projection intersection method in computer graphics.

4. The five-axis linkage sweeping path planning method for the blade cross-section region according to claim 1, characterized in that, Step S2 employs the following: Step S2.1: Construct the tip-blade mechanical model; Step S2.2: Based on the probe-blade simulation volume model, the continuous probe direction is discretized using an iterative algorithm, and collision detection is performed on the discretized probe direction to extract the probe direction that minimizes the constraints of the probe tip-blade mechanical model. Step S2.3: Correct the current direction of the measuring rod by minimizing the deviation between the front and rear measuring rod directions; The aforementioned tip-blade mechanical model abstracts the force contact model between the measuring rod and the blade into the interaction relationship between the force-bearing rod and the deformable surface.

5. The five-axis linkage sweeping path planning method for the blade cross-section region according to claim 1, characterized in that, Step S3 employs the following: The NRUBS curve of the tip path is PT(t), and its expression is: Where PTC is the control point of the NURBS probe path, N i,n Let λ be a basis function of the NURBS curve. i The weights are denoted by n; n represents the order. The NURBS curve of the probe path is PH(t), and its expression is: Where PC is the control point of the NURBS coordinate path, N i,n Let λ be a basis function of the NURBS curve. i The weight is denoted by n; After obtaining two NURBS curves, the dual NURBS method is used to perform smoothing and synchronization operations on the obtained probe path and probe base path, and finally a smooth, smooth and interference-free five-axis scanning path trajectory is obtained.

6. A five-axis linkage sweeping path planning system for a blade cross-section region, characterized in that, include: Module M1: Constructs a probe-blade simulated volume model and performs collision detection based on the probe-blade simulated volume model to determine the collision boundary; Module M2: Optimizes probe orientation based on collision boundary; Module M3: Based on the direction of the probe, the five-axis oscillating scan path is initially determined. Then, the obtained probe tip path and probe base path are smoothed and fitted using the dual NURBS method to finally obtain a smooth, smooth, and interference-free five-axis scanning path trajectory. The probe-blade simulation volume model includes a probe simulation volume model and a blade cross-sectional area mesh model.

7. The five-axis linkage sweeping path planning system for the blade cross-section area according to claim 6, characterized in that, The module M1 adopts: Obtain any line segment SE in the blade cross-section region mesh model, determine the position of the start and end points of line segment SE in the probe simulated volume model coordinate system, and determine the intersection relationship between line segment SE and probe simulated volume model based on the position of the start and end points of line segment SE in the probe simulated volume model coordinate system. When they intersect, it is determined that there is a collision between the current blade and the probe.

8. The five-axis linkage sweeping path planning system for the blade cross-section area according to claim 7, characterized in that, The intersection relationship between line segment SE and the simulated volume model of the probe is obtained by using the projection intersection method in computer graphics.

9. The five-axis linkage sweeping path planning system for the blade cross-section region according to claim 6, characterized in that, The module M2 adopts: Module M2.1: Constructing the tip-blade mechanical model; Module M2.2: Based on the probe-blade simulation volume model, the continuous probe direction is discretized using an iterative algorithm, and collision detection is performed on the discretized probe direction to extract the probe direction that minimizes the constraints of the probe tip-blade mechanical model. Module M2.3: Corrects the current probe direction by minimizing the deviation between the front and rear probe directions; The aforementioned tip-blade mechanical model abstracts the force contact model between the measuring rod and the blade into the interaction relationship between the force-bearing rod and the deformable surface.

10. The five-axis linkage sweeping path planning system for the blade cross-section region according to claim 6, characterized in that, The module M3 adopts: The NRUBS curve of the tip path is PT(t), and its expression is: Where PTC is the control point of the NURBS probe path, N i,n Let λ be a basis function of the NURBS curve. i The weights are denoted by n; n represents the order. The NURBS curve of the probe path is PH(t), and its expression is: Where PC is the control point of the NURBS coordinate path, N i,n Let λ be a basis function of the NURBS curve. i The weight is denoted by n; After obtaining two NURBS curves, the dual NURBS method is used to perform smoothing and synchronization operations on the obtained probe path and probe base path, and finally a smooth, smooth and interference-free five-axis scanning path trajectory is obtained.

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