CN114896720A - Laser cladding path planning method and system for surface of blade of aircraft engine - Google Patents
Laser cladding path planning method and system for surface of blade of aircraft engine Download PDFInfo
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Abstract
The invention relates to the field of laser cladding path planning, and provides a method and a system for planning a laser cladding path on the surface of an aircraft engine blade, which comprises the following steps: obtaining boundaries of the slice; calculating the boundary of the slice by a black-white partition algorithm to obtain an entity area of the section of the slice; layering the solid area of the section of the slice by using a self-adaptive layering algorithm to obtain a data point of the maximum profile of the slice after self-adaptive layering; calculating the data points of the maximum profile after the self-adaptive layering of the slices to obtain a NURBS interpolation curve of the slice profile; analyzing the NURBS interpolation curve of the slice profile by a contour chord method to obtain the position of a processing point; calculating the positions of the processing points by a least square method and a method of solving the partial derivatives of the curved surface equation to obtain normal vectors of the processing points; and carrying out inverse solution on the normal vector of each processing point to obtain a laser cladding path planning diagram. The invention reduces the step effect, ensures the uniformity of the energy distribution of the light spot and improves the cladding quality.
Description
Technical Field
The invention relates to the field of laser cladding path planning, in particular to a method and a system for planning a laser cladding path on the surface of an aircraft engine blade.
Background
Because the aeroengine blade is under the severe working conditions of high temperature, high pressure and alternating load for a long time, the surface of the aeroengine blade is often ablated and corroded, so that cracks and damages are generated. Meanwhile, the blade is expensive and has a long production period, so that huge economic loss can be caused by direct replacement, and the laser cladding process and technology at the present stage reach a high level, so that the use cost is reduced to a great extent by adopting a laser cladding method to repair the surface of the blade of the aero-engine. In order to ensure the repair performance and improve the cladding quality, the invention mainly aims at the route planning of the laser cladding of the surface of the blade of the aero-engine.
At present, in the aspect of cladding repair of the blade surface, most documents still adopt a contour hierarchical algorithm. However, for the blade with larger curvature change, a serious step effect can be generated, so that the difficulty of subsequent polishing is increased. Meanwhile, in the aspect of path planning of a curved surface, most scholars unfold the curved surface into a plane, project or map the curved surface back after path planning on the plane, and thus obtain the track of the curved surface path. The method is relatively complicated to apply to the blade, and it is difficult to determine the position of the processing point and the normal direction of the laser head at the processing point after obtaining the path, so that it is difficult to ensure the energy distribution of the light spot to be uniform.
The above is only for the purpose of assisting understanding of the technical aspects of the present invention, and does not represent an admission that the above is prior art.
Disclosure of Invention
In order to solve the technical problem, the invention provides a laser cladding path planning method for the surface of an aircraft engine blade, which comprises the following steps:
s1: obtaining a slice of a blade model of the aircraft engine, and calculating to obtain a boundary of the slice;
s2: calculating the boundary of the slice by a black-white partition algorithm to obtain an entity area of the section of the slice;
s3: layering the solid area of the section of the slice by using a self-adaptive layering algorithm to obtain a data point of the maximum profile of the slice after self-adaptive layering;
s4: calculating the data points of the maximum profile after the slice self-adaptive layering through a NURBS curve theory to obtain a NURBS interpolation curve of the slice profile;
s5: analyzing the NURBS interpolation curve of the slice profile by a contour chord method to obtain the position of a processing point;
s6: calculating the positions of the processing points by a least square method and a method of solving a partial derivative of a curved surface equation to obtain normal vectors of the processing points;
s7: and establishing a local coordinate system, and carrying out inverse solution on the normal vector of each processing point to obtain a laser cladding path planning diagram.
Preferably, step S1 specifically includes:
s11: placing the blade model in a three-dimensional coordinate system, and extracting a triangular patch and a slice of the blade model;
s12: aligning the direction of the slice with the Z axis of the three-dimensional coordinate system through a rotating blade model, and moving all triangular patches to a first octave of the three-dimensional coordinate system through translation transformation;
s13: layering at equal intervals in the Z-axis direction; in each layer, when a slice intersects two edges of a triangular patch, or intersects one edge and one vertex of the triangular patch, or coincides with one edge of the triangular patch, an intersection line of the slice and the triangular patch is extracted;
s14: connecting intersecting lines in each layer into a plurality of contours in a mode of generating an undirected graph, and sequentially extracting data points on each contour in a depth-first search mode to obtain the boundary of the slice.
Preferably, step S2 specifically includes:
s21: acquiring all contours of the boundary of the slices in each layer, calculating the area of a polygon of each contour, and arranging the contours in a descending order according to the area of the polygon; setting a partition, the partition comprising: the system comprises a black area and a white area, wherein the black area represents an entity area, the white area represents a non-entity area, and the outline with the largest area of a polygon in each layer is drawn into the black area;
s22: traversing all the contours in sequence according to the descending order, and if all the contours are traversed, entering a step S26, otherwise, entering a step S23;
s23: setting the currently traversed contour as a contour Sn, and setting the last traversed contour as a comparison contour Tn;
s24: judging whether the starting point of the outline Sn is in the comparison outline Tn; if so, the profile Sn is drawn into the opposite partition where the comparison profile Tn is located, and the next profile is selected and then the step S22 is returned to; if not, go to step S25;
s25: judging whether the comparison outline Tn is the outline with the largest area of the polygons in descending order; if so, drawing the profile Sn into a black area; if not, setting the last contour of the current comparison contour Tn as a new comparison contour, and returning to the step S24;
s26: filling the outline drawn into the black area into black, and filling the outline drawn into the white area into white; and adding the areas of the polygons of all the outlines in the black area, and subtracting the areas of the polygons of all the outlines in the white area to obtain a solid area of the section.
Preferably, step S3 specifically includes:
s31: calculating the area of the outline in the black area in each layer;
s32: subtracting the area of the outline in the black area of the current layer from the area of the outline in the black area of the previous layer, and dividing the absolute value of the difference by the total area of the current layer to obtain the area difference ratio of the current layer; if the area difference ratio is larger than the threshold value, inserting a new layer between the current layer and the last layer;
s33: repeating the step S32 until the area difference ratio of all the layers is less than or equal to the threshold value, and obtaining the maximum profile after the slice self-adaption layering;
s34: and extracting the coordinates of each node in the maximum profile after the self-adaptive layering of the slices to obtain the data points of the maximum profile after the self-adaptive layering of the slices.
Preferably, step S4 specifically includes:
s41, calculating the data points of the maximum profile after the slice self-adaptive layering through a NURBS curve theory to obtain each node vector;
s42: calculating each node vector by adopting the boundary condition of a closed curve, and reversely solving the coordinates of the NURBS control points;
s43: and obtaining a rational expression of the NURBS curve through the control point and the node vector, obtaining coordinates of interpolation points of the NURBS curve according to the interpolation step length, and interpolating the NURBS curve to obtain the NURBS interpolation curve of the slice profile.
Preferably, step S5 specifically includes:
s51: taking a first data point of a NURBS interpolation curve of the slice profile as a first processing point W1;
s52: selecting a current machining point Wn as a bow string starting point S; the initial value of n is 1;
s53: taking the second data point after the starting point S of the bow string as the end point E of the bow string;
s54: connecting a straight line between the starting point S and the tail end point E, and calculating the maximum vertical distance Lmax from each data point between the starting point S and the tail end point E to the straight line;
if Lmax does not exceed the threshold, go to step S55, otherwise go to step S56;
s55: taking a data point after the end point E as a data point Q;
if the data point Q is the last data point, taking the data point Q as the last processing point Wend, outputting the position of each processing point, and ending the process;
otherwise, taking the data point Q as a new end point, and returning to the step S54;
s56: if the end point E is the last data point, taking the end point E as the last machining point Wend, outputting the position of each machining point and ending the process;
otherwise, the previous data point from the end point E is set as a new current machining point, and the process returns to step S52.
Preferably, step S6 specifically includes:
s61: taking 55 NURBS interpolation points near each processing point as sample points, and obtaining an equation of a local curved surface by a least square method;
s62: and solving the partial derivative of the equation of the local curved surface to obtain the normal vector of each processing point.
Preferably, step S7 specifically includes:
s71: establishing a local coordinate system, and carrying out inverse solution on the normal vector of each processing point in the local coordinate system to obtain the position coordinate and the Euler angle of the tail end of the robot of each processing point;
s72: and cladding is directly performed between all processing points in a linear interpolation mode to obtain the laser cladding path planning diagram.
A laser cladding path planning system for an aircraft engine blade surface, comprising:
the slice boundary acquisition module is used for acquiring slices of a blade model of the aircraft engine and calculating to obtain the boundaries of the slices;
the entity area acquisition module is used for calculating the boundary of the slice through a black-white partition algorithm to obtain an entity area of the section of the slice;
the data point acquisition module is used for layering the entity area of the section of the slice through a self-adaptive layering algorithm to obtain a data point of the maximum profile of the slice after self-adaptive layering;
the interpolation curve acquisition module is used for calculating the data points of the maximum profile after the slice is subjected to self-adaptive layering through a NURBS curve theory to obtain a NURBS interpolation curve of the slice profile;
the position acquisition module of the processing point is used for analyzing the NURBS interpolation curve of the slice profile by a contour chord method to obtain the position of the processing point;
the normal vector acquisition module of the processing point is used for calculating the position of the processing point by a least square method and a method of solving the partial derivative of the curved surface equation to obtain the normal vector of each processing point;
and the laser cladding path planning map acquisition module is used for establishing a local coordinate system and carrying out inverse solution on the normal vector of each processing point to obtain a laser cladding path planning map.
The invention has the following beneficial effects:
(1) the invention provides a black-white partition algorithm to determine the entity area of the slice so as to calculate the area of the slice, and then self-adaptive layering is realized according to the area difference ratio between adjacent layers, so that the step effect is reduced;
(2) the position of a cladding processing point on the surface of the blade is determined by combining a NURBS curve interpolation theory and an equal chord height method, a normal vector of a local area at the processing point is obtained in a least square method surface fitting mode, and the posture of a laser head is determined, so that the energy distribution of laser spots is more uniform, and the cladding quality is improved.
Drawings
FIG. 1 is a flow chart of a method according to an embodiment of the present invention;
FIG. 2 is a schematic view of a solid turbine blade contour layer;
FIG. 3 is a schematic diagram of a hollow turbine blade contour stratification;
FIG. 4 is a schematic solid area view of a solid turbine blade tip cross-section;
FIG. 5 is a schematic view of a cross-sectional solid area of a hollow turbine blade tip;
FIG. 6 is a schematic diagram of an adaptive layering of a solid turbine blade;
FIG. 7 is a schematic diagram of an adaptive layering of a solid turbine blade;
FIG. 8 is a schematic illustration of a blade surface profile interpolation;
FIG. 9 is a schematic view of a machining point for cladding the surface of a blade;
FIG. 10 is a partial surface fitted;
FIG. 11 is a schematic view of normal vectors of processing points cladded on the surface of a blade;
FIG. 12 is a schematic view of the laser head posture for cladding the blade surface;
FIG. 13 is a final path of blade surface cladding;
the implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Referring to fig. 1, the invention provides a laser cladding path planning method for the surface of an aircraft engine blade, which determines the solid area of a slice through a black-white partition algorithm so as to calculate the area of the solid area, and then realizes self-adaptive layering according to the area difference ratio between adjacent layers, thereby reducing the step effect; meanwhile, the position of a cladding processing point on the surface of the blade is determined by combining a NURBS curve interpolation theory and an equal chord height method, a normal vector of a local area at the processing point is obtained in a least square method surface fitting mode, and the posture of a laser head is determined, so that the energy distribution of laser spots is more uniform, and the cladding quality is improved;
the method comprises the following steps:
s1: obtaining a slice of a blade model of the aircraft engine, and calculating to obtain a boundary of the slice;
s2: calculating the boundary of the slice by a black-white partition algorithm to obtain an entity area of the section of the slice;
s3: layering the solid area of the section of the slice by using a self-adaptive layering algorithm to obtain a data point of the maximum profile of the slice after self-adaptive layering;
s4: calculating the data points of the maximum profile after the slice self-adaptive layering through a NURBS curve theory to obtain a NURBS interpolation curve of the slice profile;
s5: analyzing the NURBS interpolation curve of the slice profile by a contour chord method to obtain the position of a processing point;
s6: calculating the positions of the processing points by a least square method and a method of solving a partial derivative of a curved surface equation to obtain normal vectors of the processing points;
s7: and establishing a local coordinate system, and carrying out inverse solution on the normal vector of each processing point to obtain a laser cladding path planning diagram.
Further, step S1 is specifically: referring to FIG. 2 and FIG. 3, the contour of the blade contour
S11: placing the blade model in a three-dimensional coordinate system, and extracting a triangular patch and a slice of the blade model;
specifically, the blade model is cut into a plurality of slices along the direction which is vertical to the Z axis and parallel to the X, Y plane in the three-dimensional coordinate system;
s12: aligning the direction of the slice with the Z axis of the three-dimensional coordinate system through a rotating blade model, and moving all triangular patches to a first octave of the three-dimensional coordinate system through translation transformation;
s13: layering at equal intervals in the Z-axis direction; in each layer, when a slice intersects two edges of a triangular patch, or intersects one edge and one vertex of the triangular patch, or coincides with one edge of the triangular patch, an intersection line of the slice and the triangular patch is extracted;
specifically, the formula for determining whether the triangular patch and the slice have an intersection is as follows:
wherein z _ slice represents the slice height, (x) 1 ,y 1 ,z 1 )(x 2 ,y 2 ,z 2 ) Coordinates representing two vertices, (x, y, z) coordinates representing an intersection;
s14: connecting intersecting lines in each layer into a plurality of contours in a mode of generating an undirected graph, and sequentially extracting data points on each contour in a depth-first search mode to obtain the boundary of the slice.
Further, step S2 is specifically: referring to FIG. 4 and FIG. 5, the extraction of the solid area of the blade tip slice
S21: acquiring all contours of the boundary of the slices in each layer, calculating the area of a polygon of each contour, and arranging the contours in a descending order according to the area of the polygon; setting a partition, the partition comprising: the system comprises a black area and a white area, wherein the black area represents an entity area, the white area represents a non-entity area, and the outline with the largest area of a polygon in each layer is drawn into the black area;
s22: sequentially traversing all the contours according to the descending order, and if all the contours are traversed, entering a step S26, otherwise, entering a step S23;
s23: setting the currently traversed contour as a contour Sn, and setting the last traversed contour as a comparison contour Tn;
s24: judging whether the starting point of the outline Sn is in the comparison outline Tn; if so, the profile Sn is drawn into the opposite partition where the comparison profile Tn is located, and the next profile is selected and then the step S22 is returned to; if not, go to step S25;
s25: judging whether the comparison outline Tn is the outline with the largest area of the polygons in descending order; if so, drawing the profile Sn into a black area; if not, setting the last contour of the current comparison contour Tn as a new comparison contour, and returning to the step S24;
s26: filling the outline drawn into the black area into black, and filling the outline drawn into the white area into white; and adding the areas of the polygons of all the outlines in the black area, and subtracting the areas of the polygons of all the outlines in the white area to obtain a solid area of the section.
Further, step S3 is specifically:
s31: calculating the area of the outline in the black area in each layer;
s32: subtracting the area of the outline in the black area of the current layer from the area of the outline in the black area of the previous layer, and dividing the absolute value of the difference by the total area of the current layer to obtain the area difference ratio of the current layer; if the area difference ratio is larger than the threshold value, inserting a new layer between the current layer and the last layer;
s33: repeating the step S32 until the area difference ratio of all the layers is less than or equal to the threshold (or the thickness of the slice is thinnest), and obtaining the maximum profile after the slice self-adaptive layering;
s34: extracting coordinates of each node in the maximum profile after the slice is subjected to the self-adaptive layering to obtain a data point of the maximum profile after the slice is subjected to the self-adaptive layering, referring to fig. 6-7, wherein fig. 6 is a slice diagram after the solid turbine blade is subjected to the self-adaptive layering, and fig. 7 is a slice diagram after the hollow turbine blade is subjected to the self-adaptive layering.
Further, step S4 is specifically: FIG. 8 is a schematic illustration of a blade surface profile interpolation;
s41, calculating the data points of the maximum profile after the slice self-adaptive layering through a NURBS curve theory to obtain each node vector;
in particular, NURBS curves (non-uniform rational B-spline curves), which have very strong flexible operability and visual intuition, are often used in machine design and reverse engineering, and a rational expression of a k-th NURBS curve can be written as:
the above formula needs to satisfy the conditions:
wherein k represents the order of the NURBS curve, and three NURBS curves are generally adopted;
w i n is a weighting factor, and a control point d i One-to-one correspondence is made between (i ═ 0, 1.., n), where the first weighting factor w is 0 And a final weight factor w 1 Are all greater than 0, other weight factors w i Not less than 0; i represents the number of data points;
the basic function of the B-spline curve (NURBS curve) can be obtained by the Deboolean-Cockss recursion formula as N i,k (U) consisting of a node vector U ═ U 0 ,u 1 ,...,u n+k+1 ]Obtained by calculation, and the definition domain of the NURBS curve is u ∈ [ u ∈ ] i ,u i+1 ]；
Calculating the node vector by using a centripetal parameterization method, wherein the calculation formula is as follows:
u 0 ＝u 1 ＝u 2 ＝u 3 ＝0
u n+3 ＝u n+4 ＝u n+5 ＝u n+6 ＝1
wherein u is i Representing a node vector, P i Representing a type value point.
S42: calculating each node vector by adopting the boundary condition of a closed curve, and reversely solving the coordinates of the NURBS control points;
specifically, a closed curve condition is used as a boundary condition, and the boundary condition is used as an additional equation:
wherein d is 0 ,d 1 ,d n+1 ,d n+2 Representing the first, second, penultimate, and penultimate control points.
And reversely solving the coordinates of the control points, wherein the formula is as follows: :
e i ＝(Δ i+1 +Δ i+2 )p i-1 i＝0,1,...,n
wherein d is i N +1 represents a control point other than the first and last, and n +3 represents the total number of control points; delta i ＝u i+1 -u i ，a i ,b i ,c i ,e i Is the coefficient of the equation set;
s43: and obtaining a rational expression of the NURBS curve through the control points and the node vectors, obtaining coordinates of interpolation points of the NURBS curve according to the interpolation step length, and interpolating the NURBS curve to obtain the NURBS interpolation curve of the slice profile.
Further, referring to fig. 9, a schematic view of a machining point of the blade surface cladding is shown;
step S5 specifically includes:
s51: using the first data point of the NURBS interpolation curve of the slice profile as the first processing point W 1 ；
S52: selecting a current processing point W n As a start point S of the bow string; the initial value of n is 1;
s53: taking the second data point after the starting point S of the bow string as the end point E of the bow string;
s54: connecting the starting point S and the end point E with a straight line, and calculating the maximum vertical distance L from each data point between the starting point S and the end point E to the straight line max ；
If L is max If the threshold value is not exceeded, the step S55 is executed, otherwise, the step S56 is executed;
s55: taking a data point after the end point E as a data point Q;
if the data point Q is the last data point, the data point Q is taken as the last processing point W end Outputting the position of each processing point and ending the process;
otherwise, taking the data point Q as a new end point, and returning to the step S54;
s56: if the end point E is the last data point, the end point E is set as the last processing point W end Outputting the position of each processing point and ending the process;
otherwise, the previous data point from the end point E is set as a new current machining point, and the process returns to step S52.
Further, referring to fig. 11, a normal vector diagram of a processing point cladded on the surface of the blade is shown;
step S6 specifically includes:
s61: taking 55 NURBS interpolation points near each processing point as sample points, and obtaining an equation of a local curved surface by a least square method;
taking the local curved surface in the y direction as an example, the curved surface equation is set as follows:
a 0 +a 1 x+a 2 z+a 3 x 2 +a 4 xz+a 5 z 2 ＝y
a i is the coefficient of the surface equation
Specifically, the formula for fitting the local curved surface by the least square method is as follows:
wherein (x) i ,y i ,z i ) Representing the coordinates of 55 sample interpolation points, wherein i and j are the numbers of the interpolation points;
s62: solving the partial derivatives of the equation of the local curved surface to obtain the normal vector of each processing point;
specifically, the calculation formula of the normal vector of each processing point is as follows:
let F be a 0 +a 1 x+a 2 z+a 3 x 2 +a 4 xz+a 5 z 2 -y
n y ＝-1
Wherein (x) 0 ,y 0 ,z 0 ) To process point coordinates, (n) x ,n y ,n z ) For the calculated normal vectorQuantity:
the fitted local surface is shown in fig. 10, and the normal direction is shown in fig. 11.
Further, step S7 is specifically:
s71: establishing a local coordinate system, and carrying out inverse solution on the normal vector of each processing point in the local coordinate system to obtain the position coordinate and the Euler angle of the tail end of the robot of each processing point;
s72: cladding is directly carried out between all processing points in a linear interpolation mode to obtain the laser cladding path planning diagram; fig. 12-13 show laser cladding path planning diagrams, fig. 12 is a schematic diagram of a laser head posture for cladding the blade surface, and fig. 13 is a final path for cladding the blade surface.
The invention provides a laser cladding path planning system for the surface of an aircraft engine blade, which comprises:
the slice boundary acquisition module is used for acquiring slices of a blade model of the aircraft engine and calculating to obtain boundaries of the slices;
the entity area acquisition module is used for calculating the boundary of the slice through a black-white partition algorithm to obtain an entity area of the section of the slice;
the data point acquisition module is used for layering the entity area of the section of the slice through a self-adaptive layering algorithm to obtain a data point of the maximum profile of the slice after self-adaptive layering;
the interpolation curve acquisition module is used for calculating the data points of the maximum profile after the slice is subjected to self-adaptive layering through a NURBS curve theory to obtain a NURBS interpolation curve of the slice profile;
the processing point position acquisition module is used for analyzing the NURBS interpolation curve of the slice profile by a contour chord method to obtain the position of the processing point;
the normal vector acquisition module of the processing point is used for calculating the position of the processing point by a least square method and a method of solving the partial derivative of the curved surface equation to obtain the normal vector of each processing point;
and the laser cladding path planning map acquisition module is used for establishing a local coordinate system and carrying out inverse solution on the normal vector of each processing point to obtain a laser cladding path planning map.
It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or system. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or system that comprises the element.
The above-mentioned serial numbers of the embodiments of the present invention are merely for description and do not represent the merits of the embodiments. In the unit claims enumerating several means, several of these means may be embodied by one and the same item of hardware. The use of the words first, second, third and the like do not denote any order, but rather the words first, second and the like may be interpreted as indicating any order.
The above description is only a preferred embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by using the contents of the present specification and the accompanying drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (9)
1. A laser cladding path planning method for the surface of an aircraft engine blade is characterized by comprising the following steps:
s1: obtaining a slice of a blade model of the aircraft engine, and calculating to obtain a boundary of the slice;
s2: calculating the boundary of the slice by a black-white partition algorithm to obtain an entity area of the section of the slice;
s3: layering the solid area of the section of the slice by using a self-adaptive layering algorithm to obtain a data point of the maximum profile of the slice after self-adaptive layering;
s4: calculating the data points of the maximum profile after the self-adaptive layering of the slices through a NURBS curve theory to obtain a NURBS interpolation curve of the slice profile;
s5: analyzing the NURBS interpolation curve of the slice profile by a contour chord method to obtain the position of a processing point;
s6: calculating the positions of the processing points by a least square method and a method of solving a partial derivative of a curved surface equation to obtain normal vectors of the processing points;
s7: and establishing a local coordinate system, and carrying out inverse solution on the normal vector of each processing point to obtain a laser cladding path planning diagram.
2. The laser cladding path planning method for the surface of the aircraft engine blade according to claim 1, wherein the step S1 specifically comprises:
s11: placing the blade model in a three-dimensional coordinate system, and extracting a triangular patch and a slice of the blade model;
s12: aligning the direction of the slice with the Z axis of the three-dimensional coordinate system through a rotating blade model, and moving all triangular patches to a first octave of the three-dimensional coordinate system through translation transformation;
s13: layering at equal intervals in the Z-axis direction; in each layer, when a slice intersects two edges of a triangular patch, or intersects one edge and one vertex of the triangular patch, or coincides with one edge of the triangular patch, an intersection line of the slice and the triangular patch is extracted;
s14: connecting intersecting lines in each layer into a plurality of contours in a mode of generating an undirected graph, and sequentially extracting data points on each contour in a depth-first search mode to obtain the boundary of the slice.
3. The laser cladding path planning method for the surface of the aircraft engine blade according to claim 1, wherein the step S2 specifically comprises:
s21: acquiring all contours of the boundary of the slices in each layer, calculating the area of a polygon of each contour, and arranging the contours in a descending order according to the area of the polygon; setting a partition, the partition comprising: the system comprises a black area and a white area, wherein the black area represents an entity area, the white area represents a non-entity area, and the outline with the largest area of a polygon in each layer is drawn into the black area;
s22: sequentially traversing all the contours according to the descending order, and if all the contours are traversed, entering a step S26, otherwise, entering a step S23;
s23: setting the currently traversed contour as a contour Sn, and setting the last traversed contour as a comparison contour Tn;
s24: judging whether the starting point of the outline Sn is in the comparison outline Tn; if so, the profile Sn is drawn into the opposite partition where the comparison profile Tn is located, and the next profile is selected and then the step S22 is returned to; if not, go to step S25;
s25: judging whether the comparison outline Tn is the outline with the largest area of the polygons in descending order; if so, drawing the profile Sn into a black area; if not, setting the last contour of the current comparison contour Tn as a new comparison contour, and returning to the step S24;
s26: filling the outline drawn into the black area into black, and filling the outline drawn into the white area into white; and adding the areas of the polygons of all the outlines in the black area, and subtracting the areas of the polygons of all the outlines in the white area to obtain a solid area of the section.
4. The laser cladding path planning method for the surface of the aircraft engine blade according to claim 1, wherein the step S3 specifically comprises:
s31: calculating the area of the outline in the black area in each layer;
s32: subtracting the area of the outline in the black area of the current layer from the area of the outline in the black area of the previous layer, and dividing the absolute value of the difference by the total area of the current layer to obtain the area difference ratio of the current layer; if the area difference ratio is larger than the threshold value, inserting a new layer between the current layer and the last layer;
s33: repeating the step S32 until the area difference ratio of all the layers is less than or equal to the threshold value, and obtaining the maximum profile after the slice self-adaption layering;
s34: and extracting the coordinates of each node in the maximum profile after the self-adaptive layering of the slices to obtain the data points of the maximum profile after the self-adaptive layering of the slices.
5. The laser cladding path planning method for the surface of the aircraft engine blade according to claim 1, wherein the step S4 specifically comprises:
s41, calculating the data points of the maximum profile after the slice self-adaptive layering through a NURBS curve theory to obtain each node vector;
s42: calculating each node vector by adopting the boundary condition of a closed curve, and reversely solving the coordinates of the NURBS control points;
s43: and obtaining a rational expression of the NURBS curve through the control point and the node vector, obtaining coordinates of interpolation points of the NURBS curve according to the interpolation step length, and interpolating the NURBS curve to obtain the NURBS interpolation curve of the slice profile.
6. The laser cladding path planning method for the surface of the aircraft engine blade according to claim 1, wherein the step S5 specifically comprises:
s51: using the first data point of the NURBS interpolation curve of the slice profile as the first processing point W 1 ；
S52: selecting a current processing point W n As a start point S of the bow string; the initial value of n is 1;
s53: taking the second data point after the starting point S of the bow string as the end point E of the bow string;
s54: connecting the starting point S and the end point E with a straight line, and calculating the maximum vertical distance L from each data point between the starting point S and the end point E to the straight line max ；
If L is max If the threshold value is not exceeded, the step S55 is executed, otherwise, the step S56 is executed;
s55: taking a data point after the end point E as a data point Q;
if the data point Q is the last data point, the data point Q is taken as the last processing point W end Outputting each working pointPosition, ending the process;
otherwise, taking the data point Q as a new end point, and returning to the step S54;
s56: if the end point E is the last data point, the end point E is set as the last processing point W end Outputting the position of each processing point and ending the process;
otherwise, the previous data point from the end point E is set as a new current machining point, and the process returns to step S52.
7. The laser cladding path planning method for the surface of the aircraft engine blade according to claim 1, wherein the step S6 specifically comprises:
s61: taking 55 NURBS interpolation points near each processing point as sample points, and obtaining an equation of a local curved surface by a least square method;
s62: and solving the partial derivative of the equation of the local curved surface to obtain the normal vector of each processing point.
8. The laser cladding path planning method for the surface of the aircraft engine blade according to claim 1, wherein the step S7 specifically comprises:
s71: establishing a local coordinate system, and carrying out inverse solution on the normal vector of each processing point in the local coordinate system to obtain the position coordinate and the Euler angle of the tail end of the robot of each processing point;
s72: and cladding is directly performed between all processing points in a linear interpolation mode to obtain the laser cladding path planning diagram.
9. A laser cladding path planning system for an aircraft engine blade surface, comprising:
the slice boundary acquisition module is used for acquiring slices of a blade model of the aircraft engine and calculating to obtain boundaries of the slices;
the entity area acquisition module is used for calculating the boundary of the slice through a black-white partition algorithm to obtain an entity area of the section of the slice;
the data point acquisition module is used for layering the entity area of the section of the slice through a self-adaptive layering algorithm to obtain a data point of the maximum profile of the slice after self-adaptive layering;
the interpolation curve acquisition module is used for calculating the data points of the maximum profile after the slice is subjected to self-adaptive layering through a NURBS curve theory to obtain a NURBS interpolation curve of the slice profile;
the position acquisition module of the processing point is used for analyzing the NURBS interpolation curve of the slice profile by a contour chord method to obtain the position of the processing point;
the normal vector acquisition module of the processing point is used for calculating the position of the processing point by a least square method and a method of solving the partial derivative of the curved surface equation to obtain the normal vector of each processing point;
and the laser cladding path planning map acquisition module is used for establishing a local coordinate system and carrying out inverse solution on the normal vector of each processing point to obtain a laser cladding path planning map.
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