Tool path planning method for open blisk hub machining based on parameter mapping

Abstract

The present invention relates to a tool path planning method for machining an open integral blade hub based on parameter mapping, comprising the following steps: S1: obtaining NURBS surfaces of the hub and fillet; S2: solving the curve after geodesic offset of the annular boundary; S3: splitting the geodesic offset curve to obtain curves C1 and C2; S4: discretely selecting points on curve C2 and offsetting curve C1 to obtain curve C1′; S5: drawing isoparametric lines from the discrete points as starting points to curve C1′, determining the number of tool paths based on the longest isoparametric line corresponding to the Euclidean space, selecting points at equal intervals on the isoparametric lines based on the number of tool paths, and sequentially connecting them along the hub axis to obtain multiple tool path paths; S6: extending both ends of each tool path in the flow channel to obtain a tool path extension path on the outer side of the blade; and S7: converting the above paths into tool position points. The present invention uses the annular boundary as the boundary for hub machining to relatively simplify complex geometric features, performs sampling based on chord height constraints, and ensures a smooth transition of the path.

Description

Technical Field

[0001] The present invention relates to the technical field of numerical control machining, and in particular to a tool path planning method for machining an open integral blade disk hub based on parameter mapping. Background Art

[0002] With the continued development of the aviation industry, the importance of blisk processing has become increasingly prominent. Blisks are widely used in the aviation sector. They are commonly used in turbine components of aircraft engines, such as the compressor and turbine in turbojets and turboprops. Blisks offer high strength, high temperature resistance, and lightweight properties, improving engine performance and efficiency while reducing aircraft weight and fuel consumption. This makes blisks an indispensable and critical component in the aviation industry.

[0003] Tool path planning for blisk hub finishing is a crucial step in CNC machining of blisks, impacting both efficiency and quality. Traditional machining methods are often unsuitable for blisks with complex surface features, and are prone to problems such as uneven paths, which compromise both efficiency and quality. Summary of the Invention

[0004] Based on this, it is necessary to provide a tool path planning method for open integral blisk hub machining based on parameter mapping in order to solve the problem of uneven path when machining integral blisk using traditional machining methods.

[0005] The present invention proposes a tool path planning method for machining an open integral blade hub based on parameter mapping, which comprises the following steps: S1: obtaining the NURBS surface of the hub and the fillet between the blade and the hub in the three-dimensional model of the blade; S2: solving the curve of the annular boundary of the fillet close to the hub side after geodesic offset in the parameter domain, and the specific steps are: S21: extracting the two-dimensional B-spline curve of the annular boundary of the fillet close to the hub side in the parameter domain from the NURBS surface; S22: finding the position of the corresponding point of each point on the two-dimensional B-spline curve in the Euclidean space along The tangent vector of the annular boundary curve and the normal vector on the corresponding hub surface; S23: cross-multiply the obtained tangent vector and the normal vector to obtain the geodesic offset direction of the annular boundary in the parameter domain; S24: preset an offset distance, and iterate the points on the two-dimensional B-spline curve according to the offset distance to obtain the geodesic offset curve of the annular boundary in the parameter domain; S3: use the golden section method to iteratively calculate the extreme points of the leading and trailing edges of the geodesic offset curve of the annular boundary in the parameter domain in the axial direction of the hub, and use the extreme points of the leading and trailing edges to align the annular boundary. The curve after geodesic migration of the wheel hub boundary in the parameter domain is split to obtain curve C1 and curve C2; ​​S4: discretize the curve C2 according to the chord height constraint to obtain multiple discrete points, and use the multiple discrete points to obtain the isoparametric line along the rotation direction of the hub surface, and offset the curve C1 in the parameter domain to obtain curve C1'; S5: use the multiple discrete points as the starting points of the isoparametric line to intersect the curve C1', and use the intersection of the isoparametric line and the curve C1' as the end point of the isoparametric line, and select the isoparametric line with the longest length in the Euclidean space according to the multiple isoparametric lines. The number of tool paths is determined by the isoparametric lines, and points are taken at equal distances on the isoparametric lines between the discrete points and the curve C1′ according to the number of tool paths, and are sequentially connected along the axial direction of the hub to obtain multiple tool paths in the flow channel between two adjacent blades; S6: the two ends of each tool path in the flow channel are extended respectively to obtain the tool path extension path on the outside of the blade; S7: the tool path in the flow channel and the points on the tool path extension path are mapped to the Euclidean space, and the points corresponding to the Euclidean space are offset by a hub margin along the normal direction of the hub surface to obtain the required tool position position.

[0006] As a further improvement of the present invention, in step S1, the NURBS surface equations of the fillet and the hub are both:

[0007] S(u,v)=P·N u (u)·N v (v) T W

[0008] Among them, P is the matrix storing the control points, W is the matrix storing the weights, and N u N is the matrix storing the B-spline basis function in direction u. v is the matrix storing the B-spline basis functions for direction v.

[0009] As a further improvement of the present invention, in step S21, given the parameter m and the node sequence M={m0,m1,…,m n+z+1}, and a set of control points P = {P0, P1, ..., P n}, the function of the two-dimensional B-spline curve is: C(m)=∑N i,z (m)P i , where N i,z (m) is the i-th basis function, defined as:

[0010] For z = 0,

[0011] For z>0,

[0012] Wherein: n is the number of control points, z is the order of the two-dimensional B-spline curve, and i = 0, 1, ... n.

[0013] As a further improvement of the present invention, the curve parameter equation c(t) of the annular boundary is assumed to be:

[0014] c(t)=(x(t),y(t),z(t))

[0015] Then the tangent vector T(t) is:

[0016]

[0017] Assume the parametric equation of the hub surface r(u,v) is:

[0018] r(u,v)=(x(u,v),y(u,v),z(u,v))

[0019] Then the normal vector N(u,v) is:

[0020]

[0021] Then the iteration direction δ of the geodesic migration n for:

[0022] δ n =T(t)×N(u,v)

[0023] Where t is the parameter of the annular boundary curve equation, x(t), y(t), and z(t) represent the position of the annular boundary curve in the x-axis, y-axis, and z-axis directions as the parameter t changes, respectively; x(u,v), y(u,v), and z(u,v) represent the position of the hub surface in the x-axis, y-axis, and z-axis directions as the parameters u and v change, respectively. and are the partial derivative vectors of the hub surface with respect to parameters u and v respectively.

[0024] As a further improvement of the present invention, in step S24, the update equation used in the coordinate iteration process is as follows:

[0025]

[0026] Among them, p, q are the u, v coordinates of the offset point, ds is the offset distance, It is an expression composed of the first basic quantity, the second basic quantity and their derivatives expressed in Christoffel symbols. k represents the direction of the result, and i and j represent the two parameter directions of the derivative, corresponding to the rate of change of the two local coordinates respectively.

[0027] As a further improvement of the present invention, in step S4, discrete points are taken on the curve C2 according to the chord height constraint, and the chord height error formula L is: s for:

[0028]

[0029] Among them, L s Represents the distance between two adjacent points, ε s is the chord height constraint error, ρ A is the normal radius of curvature of curve C2 at that point; and / or

[0030] In step S4, the parameter domain of curve C1 is [a2, b2], and the offset distance L of curve C1 is c for:

[0031]

[0032] Where B is the number of blades.

[0033] As a further improvement of the present invention, in step S5, the isoparametric line with the longest length in the Euclidean space is selected from the multiple isoparametric lines, and its length is set to L. Then the number of tool paths N is:

[0034]

[0035] Where s is the maximum line spacing between the set isoparametric lines.

[0036] As a further improvement of the present invention, step S6 specifically comprises the following steps:

[0037] S61: Obtain the tangent direction at the first and last endpoints of each tool path, extend the specified tangent distance, obtain the end point after the tangent extension, and take it as the first control point of the quadratic Bezier curve;

[0038] S62: Extend the end point obtained in S61 further along the tangential direction by a specified radial distance to obtain the end point after tangential extension, and take it as the second control point of the quadratic Bezier curve;

[0039] S63: Extend the end point obtained in S62 by a specified radial distance along the axial direction of the hub to obtain the end point after axial extension, and take the end point as the third control point of the quadratic Bezier curve;

[0040] S64: constructing a quadratic Bezier curve using the obtained first control point, second control point, and third control point, and then deriving a tool path extension path based on the quadratic Bezier curve.

[0041] As a further improvement of the present invention, in step S7, the tool position calculation formula is:

[0042] P L =P c +(r 球 +δ)n s

[0043] Among them, P L is the knife point, P c is the knife contact, r 球 is the radius of the ball end cutter, δ is the set hub allowance, n s is the normal vector of the hub surface.

[0044] The present invention also proposes a tool path generation module, which includes a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it adopts the above-mentioned open integral blade hub processing tool path planning method based on parameter mapping to generate the processing path of the blade hub according to the three-dimensional model of the blade to be processed; and sends it to the corresponding machining center.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] The present invention extracts the NURBS surfaces of the fillet and the hub based on the three-dimensional model of the blade disk, and extracts the B-spline curve of the annular boundary from the NURBS surface. Planning the path based on this can reflect the characteristics of the part itself and achieve high-precision processing effects. The annular boundary of the intersection of the hub and the fillet is used as the boundary for hub processing to relatively simplify the complex geometric features, and sampling is performed according to the chord height constraint to ensure a smooth transition of the path. By using the fillet margin control method of the geodesic offset of the intersection of the hub and the fillet, the margin can be flexibly adjusted according to actual conditions, thereby improving accuracy. In combination with the hub margin control through the hub normal vector, a universal processing path can be generated. The entire method makes the path smoother through precise geometric control and error adjustment. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 Flowchart of the steps of a tool path planning method for machining an open blisk hub based on parameter mapping according to an embodiment of the present invention;

[0048] Figure 2 A three-dimensional model diagram of a blade disk according to an embodiment of the present invention;

[0049] Figure 3 Schematic diagram of a curve after geodesic migration of an annular boundary in an embodiment of the present invention;

[0050] Figure 4 Schematic diagram of splitting a curve after geodesic migration of a circular boundary in an embodiment of the present invention;

[0051] Figure 5 Schematic diagram of sampling points after discrete sampling of surface C2 in an embodiment of the present invention;

[0052] Figure 6 Schematic diagram of a curve after the curved surface C1 is offset in an embodiment of the present invention;

[0053] Figure 7 This is a graph showing the sampling points of the surface C2 after discrete sampling and the curve after C1 offset in the Euclidean space according to an embodiment of the present invention;

[0054] Figure 8 Schematic diagram of isoparametric lines drawn through discrete points intersecting with the curve C1′ corresponding to the Euclidean space in an embodiment of the present invention;

[0055] Figure 9 Schematic diagram of the Euclidean space corresponding to uniformly sampling points on all isoparametric lines according to the number of tool paths in an embodiment of the present invention;

[0056] Figure 10 Schematic diagram of a strategy for extending a tool path in an embodiment of the present invention;

[0057] Figure 11 Schematic diagram of the path after the tool path is extended in an embodiment of the present invention;

[0058] Figure 12 This is a schematic diagram of the final complete cutting tool path in an embodiment of the present invention. DETAILED DESCRIPTION

[0059] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0060] It should be noted that when a component is referred to as being "mounted on" another component, it may be directly on the other component or there may be a central component. When a component is considered to be "set on" another component, it may be directly set on the other component or there may be a central component. When a component is considered to be "fixed to" another component, it may be directly fixed to the other component or there may be a central component.

[0061] like Figures 1-12 As shown, the embodiment of the present invention proposes a parameter mapping-based tool path planning method for machining an open blisk hub. The method is mainly used to determine the tool path planning for finishing the blisk hub based on the fillet allowance of the blisk. The specific steps are as follows:

[0062] S1: Obtain a 3D blisk model and read the NURBS surfaces of the hub and the fillets between the blades and the hub. It should be noted that the 3D blisk model is a known, existing model, and the NURBS surface expressions corresponding to the fillets between the hub and the blades in the 3D blisk model are also known. This NURBS surface information can be directly obtained from the 3D blisk model. A total of five NURBS surfaces are obtained: one surface for the hub and four surfaces for the fillets.

[0063] The expressions of the NURBS surface equations of the fillet and hub are:

[0064] S(u,v)=P·N u (u)·N v (v) T W

[0065] Among them, P is the matrix storing the control points, W is the matrix storing the weights, and the matrix N u The matrix N is the B-spline basis function matrix for storing direction u. v is a matrix storing the B-spline basis functions of direction v. In this embodiment, direction v may be the axis direction of the hub, and direction u may be the circumferential direction along the hub.

[0066] S2: Calculate the geodesic offset of the annular boundary of the fillet near the hub. The annular boundary here is the annular intersection line between the fillet and the hub surface.

[0067] The specific steps are:

[0068] S21: Extract the two-dimensional B-spline curve of the annular boundary of the fillet close to the hub side in the parameter domain from the NURBS surface obtained above. The recursive definition of the two-dimensional B-spline curve function is as follows:

[0069] Given parameter m and node sequence M={m0,m1,…,mn+z+1}, and a set of control points P = {P0, P1, ..., P n}, the two-dimensional B-spline curve can be expressed as C(m)=∑N i,z (m)P i , where N i,z (m) is the i-th basis function, defined as follows:

[0070] For z = 0,

[0071] For z>0,

[0072] Wherein: n is the number of control points, z is the order of the two-dimensional B-spline curve, and i = 0, 1, ... n.

[0073] S22: Solve the position of the corresponding point of each point on the two-dimensional B-spline curve in the Euclidean space along the tangent vector of the annular boundary curve and the normal vector on its corresponding hub surface.

[0074] The tangent vector of the corresponding point of each point on the 2D B-spline curve in Euclidean space along the annular boundary curve can be calculated by taking the derivative of the parametric equation of the annular boundary with respect to the parameter. Specifically, let the curve equation of the annular boundary be:

[0075] c(t)=(x(t),y(t),z(t))

[0076] Where t is the parameter of the annular boundary curve equation, and x(t), y(t), and z(t) represent the changes in the position of the annular boundary curve in the x-axis, y-axis, and z-axis directions respectively as the parameter t changes.

[0077] Then the tangent vector T(t) of the corresponding point of each point on the two-dimensional B-spline curve in Euclidean space along the annular boundary curve is:

[0078]

[0079] Assume the parametric equation of the hub surface r(u,v) is:

[0080] r(u,v)=(x(u,v),y(u,v),z(u,v))

[0081] Then the normal vector N(u,v) on the hub surface corresponding to the position of the corresponding point in Euclidean space at each point on the two-dimensional B-spline curve is:

[0082]

[0083] S23: Cross-multiply the obtained tangent vector T(t) and the normal vector N(u,v) to obtain the direction of the geodesic offset of the annular boundary curve δn ;

[0084] δ n =T(t)×N(u,v)

[0085] Among them, x(u,v), y(u,v) and z(u,v) represent the position of the hub surface in the x-axis, y-axis and z-axis directions as the parameters u and v change, respectively. and are the partial derivative vectors of the hub surface with respect to parameters u and v. Since the annular boundary curve is the offset curve obtained through continuous iteration, the above-mentioned geodesic offset direction is also called the geodesic iteration direction.

[0086] S24: Preset an offset distance, and iterate the points on the two-dimensional B-spline curve according to the offset distance to obtain the curve after the annular boundary geodesic offset. It should be noted that the offset distance, also known as the fillet allowance, is usually determined based on the previous process. The operator can set the offset distance based on the actual working conditions. Then, the coordinates of the points on the two-dimensional B-spline curve can be updated and iterated based on the preset offset distance. The update equation used in the coordinate iteration process is as follows:

[0087]

[0088] Among them, p, q are the u, v coordinates of the offset point, ds is the offset distance, It is an expression composed of the first basic quantity, the second basic quantity and their derivatives expressed in Christoffel symbols. k represents the direction of the result, and i and j represent the two parameter directions of the derivative, corresponding to the rate of change of the two local coordinates respectively.

[0089] In this way, the allowance control near the fillet can be achieved, so that different tool paths can be generated according to different allowances, which facilitates multiple cutting processes on the fillet, thereby improving the quality and accuracy of the processing.

[0090] S3: The extreme points of the leading and trailing edges of the two-dimensional B-spline curve in the axial direction of the wheel hub are iteratively calculated using the golden section method, and the two-dimensional B-spline curve is split using the extreme points of the leading and trailing edges to obtain curves C1 and C2.

[0091] Since the first-order derivatives of the leading and trailing edge curves of the two-dimensional B-spline curve in the wheel hub axis are continuous and monotonic, when the first-order derivative of the leading edge curve is 0, it is the extreme point of the corresponding leading edge curve. When the first-order derivative of the trailing edge curve is 0, it is the extreme point of the corresponding trailing edge curve. The golden section method can be used to obtain the first-order derivative of 0.

[0092] For example, the specific steps for finding the minimum value are:

[0093] S31: Given an initial interval [a,b], and an accuracy requirement∈.

[0094] S32: Calculate two segmentation points t1, t2 so that Where φ is the golden ratio, usually taken as

[0095] S33: Calculate the values ​​f(t1) and f(t2) of the function f(t) of the two-dimensional B-spline curve at two segmentation points.

[0096] Compare f(t1) and f(t2) to determine the interval that should be searched in the next iteration.

[0097] If f(t1)>f(t2), then there can be no extreme point in [a,t1], and the update interval is [t1,b];

[0098] If f(t1)≤f(t2), then there can be no extreme points in [t2,b], and the update interval is [a,t2].

[0099] S34: Repeat steps S32 to S33 until the interval length is less than or equal to the given precision ∈, and the midpoint of the remaining interval is the minimum point of the function.

[0100] The specific steps for finding the maximum value are:

[0101] S35: Given an initial interval [a1,b1], and an accuracy requirement∈.

[0102] S36: Calculate two segmentation points t3, t4 so that Where φ is the golden ratio, usually taken as

[0103] S37: Calculate the values ​​f(t3) and f(t4) of the function f(t) of the two-dimensional B-spline curve at the two segmentation points.

[0104] Compare f(t3) and f(t4) to determine the interval that should be searched in the next iteration.

[0105] If f(t3)>f(t4), then there can be no extreme point in [t4,b1], and the update interval is [a1,t4];

[0106] If f(t3)≤f(t4), then there can be no extreme points in [a1,t3], and the update interval is [t3,b1].

[0107] S38: Repeat steps S36 to S37 until the interval length is less than or equal to the given precision ∈, and the midpoint of the remaining interval is the maximum point of the function.

[0108] After obtaining the minimum point and the maximum point, the two-dimensional B-spline curve is split into curve C1 and curve C2 according to the minimum point and the maximum point.

[0109] S4: Discretize the curve C2 according to the chord height constraint to obtain multiple discrete points, and use the multiple discrete points to obtain isoparametric lines along the rotation direction of the hub surface, and offset the curve C1 in the parameter domain to obtain curve C1′.

[0110] Specifically, assume that the curve equation of curve C2 is: C2(t)=(u(t),v(t)), where t is a parameter.

[0111] Chord height error formula L s for:

[0112]

[0113] Among them, L s Represents the distance between two adjacent points, ε s is the chord height constraint error, ρ A is the normal curvature radius of curve C2 at this point.

[0114] First, select the first point P1. The first point P1 can be the first or last endpoint of the curve C2. In this way, we can use the position of the first point P1 and the chord height error formula L s Calculate P2 along the length direction of curve C2. n In this way, multiple discrete points in the curve C2 can be obtained.

[0115] Assume that the parameter domain of curve C1 is [a2, b2], and the offset distance L of curve C1 is c for:

[0116]

[0117] Where B is the number of blades.

[0118] As shown in the figure, it should be noted that when processing the fillet, the flow channel between two adjacent blades is mainly processed. |b2-a2| is the circumference of the hub surface, the curve C2 is the left boundary of one of the flow channels, and the offset C1′ is the right boundary of the flow channel. Finally, the tool path is designed in the flow channel between the corresponding curve C2 and the offset C1′.

[0119] S5: Using the multiple discrete points sampled from the curve C2 as the starting points of the isoparametric line, an intersection line is drawn with the curve C1′, and the intersection point of the isoparametric line and the curve C1′ is used as the end point of the isoparametric line. The number of tool paths is determined based on the isoparametric line with the longest length in the Euclidean space among the multiple isoparametric lines.

[0120] Assume that the length of the longest isoparametric line corresponding to the Euclidean space is L, then the number of tool paths N is:

[0121]

[0122] Where s is the maximum line spacing between the set isoparametric lines.

[0123] And according to the number of tool paths, the isoparametric lines between the discrete points and the curve C1′ are sampled at equal distances. The number of points can be determined according to the actual working conditions, and they are connected in sequence along the axial direction of the hub to obtain the paths of multiple tool paths in the flow channel. For example: if the number of tool paths obtained is 10, 10 points are sampled at equal distances on each isoparametric line, and the first point on each isoparametric line is connected in sequence along the axial direction of the hub to obtain the first tool path. The second point on each isoparametric line is connected in sequence along the axial direction of the hub to obtain the second tool path. And so on, ten tool paths can be obtained. Among them, the flow channel is the space between two adjacent blades.

[0124] S6: As shown in the figure, each end of the tool path in the flow channel is extended to obtain the tool path extension path outside the blade. The specific steps are:

[0125] S61: Obtain the tangent direction at the first and last endpoints of each tool path, extend the tangent by a specified distance, obtain the end point of the tangent extension, and use it as the first control point of the quadratic Bezier curve. The tangent distance here refers to the difference in V values ​​between the two points. The extension distance in this step can be determined based on actual working conditions.

[0126] S62: The end point obtained in S61 is further extended tangentially by a specified radial distance to obtain the end point after tangential extension, and the end point is taken as the second control point of the quadratic Bezier curve. The tangential distance here refers to the difference in V values ​​between the two points, and the extension length can be 1 / 4 of the radial distance.

[0127] S63: Extend the endpoint obtained in S62 along the hub axis by a specified radial distance to obtain the axially extended endpoint, which is used as the third control point of the quadratic Bezier curve. The axial distance here also refers to the difference in V values ​​between the two points. The extension length can be 1 / 4 of the radial distance.

[0128] S64: A quadratic Bezier curve is constructed using the first, second, and third control points as a transition curve. The transition curve is extended from its endpoint along the hub axis by a specified radial distance. This curve, combined with the two extended curves from steps S62 and S63, forms the final tool path extension. The tool path extension path, combined with the previous tool path, forms the complete tool path. The extension distance in this step can be determined based on actual machining conditions.

[0129] Among them, the general expression of Bezier curve is:

[0130]

[0131] Where P(t) is a point on the curve; t is a parameter, usually ranging from 0≤t≤1; n is the number of control points, P i are the coordinates of the control points. is the Bessel basis function, defined as follows:

[0132]

[0133] in, is the binomial coefficient, i.e. the number of combinations:

[0134]

[0135] S7: The tool path in the flow channel and the points on the tool path extension path are mapped to the Euclidean space, and the points corresponding to the Euclidean space are offset along the normal direction of the hub surface by a hub margin to obtain the required tool position points.

[0136] The calculation formula of the knife position point is:

[0137] P L =P c +(r 球 +δ)n s

[0138] Among them, P L is the knife point, P c is the knife contact, r 球 is the radius of the ball end cutter, δ is the set hub allowance, n s is the normal vector of the hub surface.

[0139] An embodiment of the present invention further provides a tool path generation module comprising a memory, a processor, and a computer program stored in the memory and running on the processor. When executing the computer program, the processor employs the aforementioned parameter-mapping-based tool path planning method for machining an open integral blisk hub. Based on a three-dimensional model of the blisk to be machined, the module generates a machining path for the blisk hub, including the machining path and the tool location path obtained in the aforementioned method. The module then transmits the generated machining path to a corresponding machining center. Upon receiving the corresponding information, the machine tool in the machining center controls the tool axis to move according to the preset tool machining path, thereby completing the finish machining of the workpiece.

[0140] The tool path generation module provided in this embodiment is essentially a computer device for implementing data processing and instruction generation, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor.

[0141] The computer device provided in this embodiment can be an embedded device installed on a CNC machine tool, or it can be an intelligent terminal, tablet computer, laptop computer, desktop computer, rack server, blade server, tower server or cabinet server (including an independent server or a server cluster composed of multiple servers) that can execute computer programs and is independent of the machine tool. The computer device of this embodiment includes at least but is not limited to: a memory, a processor, a memory device, a processor ...

[0142] In this embodiment, the memory (i.e., readable storage medium) includes flash memory, hard disk, multimedia card, card-type memory (for example, SD or DX memory, etc.), random access memory (RAM), static random access memory (SRAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), programmable read-only memory (PROM), magnetic memory, magnetic disk, optical disk, etc.

[0143] In some embodiments, the memory may be an internal storage unit of a computer device, such as a hard disk or a memory of the computer device.

[0144] In other embodiments, the memory may also be an external storage device of the computer device, such as a plug-in hard disk, a SmartMediaCard (SMC), a SecureDigital (SD) card, a FlashCard, etc., equipped with the computer device. Of course, the memory may also include both the internal storage unit of the computer device and its external storage device. In this embodiment, the memory is generally used to store the operating system and various application software installed on the computer device. In addition, the memory may also be used to temporarily store various types of data that have been output or are about to be output.

[0145] In some embodiments, the processor may be a central processing unit (CPU), a graphics processing unit (GPU), a controller, a microcontroller, a microprocessor, or other data processing chip. The processor is generally used to control the overall operation of a computer device. In this embodiment, the processor is used to run program code stored in a memory or process data.

[0146] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "or / and" as used herein includes any and all combinations of one or more of the associated listed items.

[0147] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0148] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A tool path planning method for machining an open blisk hub based on parameter mapping, characterized in that: It includes the following steps: S1: Obtain the NURBS surfaces of the hub and the fillet between the blade and hub in the 3D model of the blade disk; S2: Solve the curve of the annular boundary of the fillet close to the hub after geodesic offset in the parameter domain. The specific steps are as follows: S21: Extract the 2D B-spline curve of the annular boundary of the fillet close to the hub side in the parameter domain from the NURBS surface; S22: Find the tangent vector of the corresponding point of each point on the two-dimensional B-spline curve in Euclidean space along the annular boundary curve and the normal vector on the corresponding hub surface; S23: performing a cross multiplication of the obtained tangent vector and the normal vector to obtain the geodesic offset direction of the annular boundary in the parameter domain; S24: Preset an offset distance, and iterate the points on the two-dimensional B-spline curve according to the offset distance to obtain a geodesically offset curve of the annular boundary in the parameter domain; S3: Using the golden section method, iteratively calculate the extreme points of the leading and trailing edges of the curve after geodesic shift of the annular boundary in the parameter domain in the axial direction of the hub. The extreme points of the leading and trailing edges are used to split the curve after geodesic shift of the annular boundary in the parameter domain to obtain curves C1 and C2. S4: Discretize the curve C2 according to the chord height constraint to obtain multiple discrete points, and use the multiple discrete points to obtain isoparametric lines along the rotation direction of the hub surface. Offset the curve C1 in the parameter domain to obtain curve C1′; S5: Using the plurality of discrete points as starting points of the isoparametric lines, intersecting the curve C1′, and using the intersection of the isoparametric lines and the curve C1′ as the end point of the isoparametric lines, determining the number of tool paths according to the isoparametric line with the longest length in the Euclidean space corresponding to the plurality of isoparametric lines, and taking points of equal distances from the isoparametric lines between the discrete points and the curve C1′ according to the number of tool paths, and sequentially connecting them along the axial direction of the hub to obtain a plurality of tool paths in the flow channel between two adjacent blades; S6: Extending both ends of each tool path in the flow channel to obtain a tool path extension path outside the blade; S7: Mapping the tool path in the flow channel and the points on the tool path extension path to the Euclidean space, and offsetting the points corresponding to the Euclidean space by a hub margin along the normal direction of the hub surface to obtain the required tool position points.

2. The tool path planning method for machining an open blisk hub based on parameter mapping according to claim 1, characterized in that: In step S1, the NURBS surface equations of the fillet and hub are: S(u,v)=P·N u (u)·N v (v) T ·W Among them, P is the matrix storing the control points, W is the matrix storing the weights, and N u N is the matrix storing the B-spline basis function in direction u. v is the matrix storing the B-spline basis functions for direction v.

3. The tool path planning method for machining an open blisk hub based on parameter mapping according to claim 1, characterized in that: In step S21, given the parameter m and the node sequence M = {m0, m1, ..., m n+z+1 }, and a set of control points P = {P0, P1, ..., P n }, the function of the two-dimensional B-spline curve is: C(m)=∑N i,z (m)P i , where N i,z (m) is the i-th basis function, defined as: For z = 0, For z>0, Wherein: n is the number of control points, z is the order of the two-dimensional B-spline curve, and i = 0, 1, ... n.

4. The tool path planning method for machining an open blisk hub based on parameter mapping according to claim 1, characterized in that: Assume that the curve parameter equation c(t) of the annular boundary is: c(t)=(x(t),y(t),z(t)) Then the tangent vector T(t) is: Assume the parametric equation of the hub surface r(u,v) is: r(u,v)=(x(u,v),y(u,v),z(u,v)) Then the normal vector N(u,v) is: Then the iteration direction δ of the geodesic migration n for: δ n =T(t)×N(u,v) Where t is the parameter of the annular boundary curve equation, x(t), y(t), and z(t) represent the position of the annular boundary curve in the x-axis, y-axis, and z-axis directions as the parameter t changes, respectively; x(u,v), y(u,v), and z(u,v) represent the position of the hub surface in the x-axis, y-axis, and z-axis directions as the parameters u and v change, respectively. and are the partial derivative vectors of the hub surface with respect to parameters u and v respectively.

5. The tool path planning method for machining an open blisk hub based on parameter mapping according to claim 1, characterized in that: In step S24, the update equation used in the coordinate iteration process is as follows: Among them, p, q are the u, v coordinates of the offset point, ds is the offset distance, It is an expression composed of the first basic quantity, the second basic quantity and their derivatives expressed in Christoffel symbols. k represents the direction of the result, and i and j represent the two parameter directions of the derivative, corresponding to the rate of change of the two local coordinates respectively.

6. The tool path planning method for machining an open blisk hub based on parameter mapping according to claim 1, characterized in that: In step S4, the curve C2 is discretely selected according to the chord height constraint, and the chord height error formula L s for: Among them, L s Represents the distance between two adjacent points, ε s is the chord height constraint error, ρ A is the normal radius of curvature of curve C2 at that point; and / or In step S4, the parameter domain of curve C1 is [a2, b2], and the offset distance L of curve C1 is c for: Where B is the number of blades.

7. The tool path planning method for machining an open blisk hub based on parameter mapping according to claim 1, characterized in that: In step S5, the isoparametric line with the longest length in the Euclidean space is selected from the multiple isoparametric lines, and its length is set as L. Then the number of tool paths N is: Where s is the maximum line spacing between the set isoparametric lines.

8. The tool path planning method for machining an open blisk hub based on parameter mapping according to claim 7, characterized in that: The specific steps of step S6 are: S61: Obtain the tangent direction at the first and last endpoints of each tool path, extend the specified tangent distance, obtain the end point after the tangent extension, and take it as the first control point of the quadratic Bezier curve; S62: Extend the end point obtained in S61 further along the tangential direction by a specified radial distance to obtain the end point after tangential extension, and take it as the second control point of the quadratic Bezier curve; S63: Extend the end point obtained in S62 by a specified radial distance along the axial direction of the hub to obtain the end point after axial extension, and take the end point as the third control point of the quadratic Bezier curve; S64: constructing a quadratic Bezier curve using the obtained first control point, second control point, and third control point, and then deriving a tool path extension path based on the quadratic Bezier curve.

9. The tool path planning method for machining an open blisk hub based on parameter mapping according to claim 1, characterized in that: In step S7, the tool position calculation formula is: P L =P c +(r 球 +δ)n s Among them, P L is the knife point, P c is the knife contact, r 球 is the radius of the ball end cutter, δ is the set hub allowance, n s is the normal vector of the hub surface.

10. A tool path generation module comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the computer program, it uses the parameter mapping-based open integral blade hub machining tool path planning method as described in any one of claims 1 to 9 to generate a machining path for the blade hub based on the three-dimensional model of the blade to be machined; and sends it to the corresponding machining center.

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