CN113867259B - Reconstruction method of cutter track transverse information based on space grid - Google Patents

Abstract

The present invention belongs to the technical field related to numerical control machining, and discloses a method for reconstructing the lateral information of a tool trajectory based on a spatial grid. The method includes the following steps: S1 determines the coordinates of each tool position point on the machining trajectory and the limit coordinates along the coordinate axis direction, and divides the area included in the limit coordinates into grids; S2 determines the grids intersecting with the straight lines formed by connecting adjacent tool positions, and marks the intersecting grids, traversing all tool positions to obtain the corresponding relationship between the tool positions and the grids; S3 constructs a search range for any tool position point, calculates the distance between the tool position point corresponding to each grid and the tool position point, and uses the tool position point with the closest distance as the lateral point of the tool position point, so as to obtain the lateral points of all tool positions in this way, that is, to obtain the lateral information of the tool trajectory. Through the present invention, the problems of low efficiency and long time consumption when accessing points and straight line segments along the tool path trajectory and lateral access between adjacent tool positions across the tool path in the line cutting trajectory are solved.

Description

A method for reconstructing lateral information of tool paths based on spatial grids

Technical Field

The present invention belongs to the technical field related to numerical control machining, and more specifically, relates to a method for reconstructing lateral information of tool paths based on space grids.

Background technique

In CNC machining, the G code generated by CAM software usually has extremely uneven distribution of points when it is discretized. Some areas have dense distribution of points, while others have sparse distribution of points. Sparse point clouds can only be accessed in an orderly manner based on the order in which they are generated. This order of point access is not efficient. When the number of point clouds is large, it seriously affects the access to points on the tool path, restricting other operations such as calculation or optimization performed by the program or algorithm. This traditional access method makes the process of searching for points very time-consuming during the optimization of machining complex curved parts.

As shown in Figure 2, the operation of G code points is usually accessed in the order of points from front to back along the tool path trajectory, but sometimes it is necessary to quickly access along the horizontal direction of the tool path, as shown in Figure 3. Based on the speed planning method of speed interval, after identifying the boundary feature points of the speed interval, it is necessary to optimize the boundary feature points of the speed interval in a horizontal direction, and the optimization is generally carried out through the spline curve. Since the spline curve is relatively smooth in the horizontal direction of the tool path, the "sawtooth" speed boundary feature points in the horizontal direction of the tool path are smoothed to make them consistent in the horizontal direction. However, since the spline curve is mapped to the tool path trajectory along the horizontal direction of the tool path, it is necessary to access the tool path trajectory across the tool path line. The traditional point-based construction of the horizontal relationship of the tool path becomes very unreliable due to the uneven distribution of points.

Summary of the invention

In response to the above defects or improvement needs of the prior art, the present invention provides a method for reconstructing the lateral information of the tool trajectory based on a spatial grid, which solves the problems of low efficiency and long time consumption when accessing points and straight line segments along the tool path trajectory and when accessing adjacent tool position points across the tool path in the cutting trajectory.

To achieve the above object, according to the present invention, a method for reconstructing lateral information of tool paths based on a spatial grid is provided, the method comprising the following steps:

S1 determines the coordinates of each tool position point on the machining trajectory according to the G code on the machining trajectory, determines the limit coordinates of all tool position points along the coordinate axis direction, and divides the area included in the limit coordinates into grids to obtain multiple subdivided grids;

S2, for each group of adjacent tool position points corresponding to the G code, determining the grids intersecting with the straight lines formed by connecting the group of adjacent tool position points, marking the intersecting grids, and traversing all tool position points to obtain the corresponding relationship between the tool position points and the grids;

S3 constructs a search range for any tool position point _ps , and calculates the distance between the tool position point corresponding to each grid and the tool position point _ps according to the correspondence between the tool position point and the grid established in step S2. The tool position point with the closest distance is taken as the lateral point of the tool position point _ps . In this way, the lateral points of all tool position points are obtained, that is, the lateral information of the tool trajectory is obtained.

Further preferably, in S1, the processing trajectory is a line cutting trajectory, and the processing trajectory has a plurality of parallel tool paths.

Further preferably, before step S2, each tool position point needs to be assigned an index number that is consistent with the order in sequence.

Further preferably, in step S2, the marking of the intersecting grids is performed in the following manner:

When the straight line formed by adjacent tool point locations is in the same grid, the adjacent tool point locations are used to mark the grids at the same time; when the straight line formed by adjacent tool point locations p _i and p _i+1 are not in the same grid, the grid where tool point location p _i is located is marked with the index number of tool point location p _i , and the other grids intersecting with the straight line and the grid of the tool point location p _i+1 are marked with the index number of tool point location p _i+1 .

Further preferably, in step S3, the building of the search scope is performed according to the following steps:

S31 determines the offset direction of the tool position point _ps and the tool path interval between the cutting trajectories, wherein the offset direction is a direction perpendicular to the tool path cutting direction and parallel to the XOY plane, and the tool position point _ps is offset according to the offset direction to obtain an offset point;

S32 takes the grid where the offset point is located as the center and presets the search radius to determine the search range.

Further preferably, for the grids in the search range, grids corresponding to index numbers greater than and less than the index number corresponding to the tool position point _ps are respectively established into sets V ⁺ and ^V- , and grid points in sets V ⁺ and ^V- with index numbers between the index numbers of the first and last boundary points of the single tool trajectory where the tool position point _ps is located are eliminated, and the set formed by the remaining grids is used as the new search range.

Further preferably, the first and last boundary points of the single tool trajectory where the tool position point _ps is located are determined in the following manner:

According to the index number of the tool position point _ps , on the single tool trajectory where _ps is located, search is performed in two directions with index numbers greater than and less than the index number of the tool position point _ps ; when a straight line formed by connecting two adjacent tool position points on the single tool trajectory is not parallel to the direction of the single tool trajectory, the tool position point closer to _ps among the two adjacent tool position points is one of the head and tail boundary points of the single tool trajectory.

Further preferably, the preset search radius is 3×3×n, in the X and Y axis directions, the search step is 3 grids, and n is the step in the Z direction, which is set according to actual conditions.

Further preferably, according to the correspondence between the tool position point and the grid established in step S2, the distance between the tool position point corresponding to each grid and the tool position point _ps is calculated, specifically: according to the index number corresponding to each grid, the tool position point corresponding to the index number is obtained, and the distance from the tool position point corresponding to the index number to the tool position point _ps is calculated.

Further preferably, in step S1, when the grid is divided, the spacing between grids is set to [d/8, d/4], where d is the spacing between parallel tool paths.

In general, the above technical solutions conceived by the present invention have the following beneficial effects compared with the prior art:

1. In the present invention, by constructing a topological relationship between a grid and a tool point, searching for grids on adjacent tool paths, using grids to represent tool points, and constructing a lateral relationship between tool path and tool point locations adjacent across rows, rapid lateral access to tool paths is achieved, thereby improving the access efficiency of lateral tool points;

2. In the present invention, when constructing the topological relationship between the network and the tool point, the index number of the tool point is introduced into the grid, which, on the one hand, retains the information of the tool point, and on the other hand, enables the tool point to be quickly found by the index number when calculating the horizontal tool point, thereby reducing the amount of calculation in the calculation process and reducing the calculation complexity;

3. In the present invention, when searching for the lateral points of the tool position point, firstly, the offset point of the tool position point is obtained by the spacing of the machining trajectory, the offset point is used as the search center, and the points near the offset point are searched. The grid points outside the boundary of the search range are extracted within the search range, and the search range is further narrowed, thereby avoiding large-area searches, narrowing the search range, improving the search accuracy, and simplifying the calculation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a flow chart of a method for reconstructing lateral information of a tool trajectory based on a space grid according to a preferred embodiment of the present invention;

FIG2 is a schematic diagram of a line cutting tool path trajectory constructed according to a preferred embodiment of the present invention;

FIG3 is a schematic diagram of a knife position point in a row cutting path constructed according to a preferred embodiment of the present invention;

4 is a schematic diagram of solving the limit coordinates of the tool position coordinate axis direction constructed according to the preferred embodiment of the present invention;

FIG5 is a schematic diagram of a meshed tool path constructed according to a preferred embodiment of the present invention;

6 is a schematic diagram of the relationship between the tool position points and the grid obtained by intersecting adjacent tool position points with the grid constructed according to the preferred embodiment of the present invention;

7 is a flow chart of obtaining the lateral point of the tool position point constructed according to the preferred embodiment of the present invention;

FIG8 is a schematic diagram of solving boundary points of a current point constructed according to a preferred embodiment of the present invention;

FIG9 is a schematic diagram showing the principle of solving the lateral point of the cutter position constructed according to the preferred embodiment of the present invention;

FIG. 10 is a schematic diagram of a rapid access from a knife position point to a lateral point constructed according to a preferred embodiment of the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

In view of the technical problem solved by the present invention, the present invention can be applied in the scenario of solving two problems: fast access to G code points and straight line segments and fast access between straight line segments of tool path lateral operation. In order to explain the method of the present invention in more detail, the technical solution of the present invention is described below in combination with specific scenarios and embodiments. Specifically, as shown in FIG1:

S1: Calculate the limit coordinates of the tool position point in the three directions of x, y and z, and divide the grid into these ranges. The specific method is as follows:

①Import the G-code file and record the coordinates of each tool position point in sequence.

The G code file is composed of a series of discrete point coordinates and control instructions. The point positions are ordered. Two adjacent points form a straight line segment. The lines between the ordered points form the tool path. By recording the index of points and straight lines, you can quickly and easily access the points and straight lines on the tool path.

② As shown in Figure 4, traverse the tool position points and find the maximum and minimum values x_min, x_max, y_min, y_max, z_min, z_max in the x, y, and z directions;

Set the spatial grid step size x_step, y_step, z_step, and calculate the number of divisions in the three directions of xyz, that is, x_num = [x_max + x_offset - (x_min - x_offset)] / x_step,

y_num = [y_max + y_offset - (y_min - y_offset)] / y_step,

z_num＝[z_max+z_offset-(z_min-z_offset)]/z_step,

Among them, x_offset, y_pffset, z_offset are the sizes of the border enlargement. For simplicity, let x_offset = y_offset = z_offset = x_step/2 = y_step/2 = z_step/2

In order to better present the spatial gridding algorithm of G-code trajectory, the XOY plane gridding is used for illustration, and the spatial gridding can be added with the z coordinate. As shown in Figure 4, the grid is divided between the four lines of the upper, lower, left and right of the outer frame. The number of grids in the x direction is x_num = [x_max + x_offset - (x_min - x_offset)] / x_step, and the number of grids in the y direction is y_num = [y_max + y_offset - (y_min - y_offset)] / y_step. The index of any p _i (x _i , y _i ) in the x direction is:

intx＝[ _xi +x_offset-(x_min-x_offset)]/x_step，

The index in the y direction is:

inty = [ _yi + y_offset - (y_min - y_offset)] / y_step.

S2: As shown in Figure 5, add the index numbers of all tool positions in the programming trajectory to the grid. The specific method is as follows:

① Traverse all straight line segments blk _i = p _i ( _xi , _yi , z _i ) p _i+1 (xi ₊₁ , yi ₊₁ , z _i+1 ) and calculate the grid set {cube _i } that the straight line segment passes through. The calculation method is as follows:

First, the grid index numbers xNum _i , yNum _i , zNum _i , xNum _i+1 , yNum _i+1 , zNum _i+1 where the tool positions p _i , p _i+1 are located are calculated according to the following formula.

Then determine whether p _i , p _i+1 are in the same grid. If so, just add the grid to {cube}. If p _i , p _i+1 are not in the same grid, discretize the straight line segments p _i , p _i+1 as the point set {P} with a step size of step/4, calculate the grid where each point in {P} is located, and do not repeatedly add each grid to {cube _i }.

② Add the corresponding knife point index number to the grid in {cube _i }, as shown in Figure 6. First, determine whether {cube _i } has only one grid. If so, add p _i and p _i+1 to the grid. Before adding, determine whether p _i already exists in the grid. If so, only add p _i+1 . If the number of grids in {cube} is greater than 1, the rule for adding knife points is as follows: p _i is added to the first grid without duplication, and p _i+1 is added to each subsequent grid without duplication.

S3: As shown in FIG7 , find the lateral tool position points on the adjacent tool paths of each tool position point and construct the lateral adjacent relationship of the tool position points. The specific method is as follows:

① As shown in Figure 8, calculate the boundary points P _b1 and P _b2 of the line cutting path to which the current point P _s belongs. Start searching forward and backward from the selected tool position point. If the direction of the searched straight line segment is not parallel to the line cutting direction, take the endpoint of the straight line segment close to the selected tool position point as the boundary points P _b1 and P _b2 of the current line cutting path, and their index numbers are N _b1 and N _b2 . If the selected point P _s is a boundary point, no subsequent operation is performed; otherwise, continue the subsequent lateral search.

② Calculate the estimated points _Pt1 and _Pt2 of the lateral tool positions of the current tool position _Ps on the adjacent tool path. is the projection direction/> The position coordinates calculated to be one tool path interval d in the lateral direction from the current tool position point are P _t1 , P _t2 .

③ Determine the horizontal point search range. Calculate the grid index numbers c _t1 , c _t2 to which the estimated points P _t1 , P _t2 coordinates belong, and set the 3×3×n (n is set by the user according to different programming trajectories) grid centered on this grid as the search range c _t1 , c _t2 .

④ Find the transverse tool position point of _Ps in c _t1 , c _t2 . All tool positions in C _t1 , C _t2 and the front and back points of each tool position point (no duplication) are set V. These points are stored in containers V ⁺ , V ^- according to the index number greater than the selected point index number and less than the selected point index number. Eliminate the tool positions with row numbers [N _b1 , N _b2 ] in V ⁺ , V ^- (these points are points on the current line cutting path rather than points on the adjacent tool path) to avoid affecting the subsequent calculation of the nearest point. Calculate the tool position point closest to the current point in V ⁺ , V ^- respectively, which are the transverse tool positions P _front , P _next of the selected tool position point on the adjacent tool path.

S4: Applying the established transverse relationship, as shown in Figures 9 and 10, the transverse tool position point corresponding to the current tool position point can be quickly obtained: for example, select any tool position point on the programming trajectory, directly obtain the left and right transverse points of the selected tool position point according to the established transverse relationship, and then continue to obtain the next transverse point to the left and right based on the obtained transverse point, and repeat the cycle until the next transverse point cannot be found, and finally a "transverse feature line" is obtained.

In the method of the present invention, a method for constructing lateral information of tool path trajectory based on grid is adopted. Under the premise of not changing the original G code, the lateral relationship between the tool position point and the tool position point on its adjacent tool path is constructed through the spatial topological relationship of the grid. This can solve the problem of needing to access adjacent tool path tool position points across rows during the lateral calculation or optimization of the tool path trajectory. It only needs to establish the lateral relationship once in advance to improve the efficiency of subsequent lateral adjacent point access and reduce the running time consumption.

Notice:

(1) In order to ensure the effectiveness of establishing horizontal relationships, the grid step size in S1② is usually set to be no greater than (d is the tool path spacing); at the same time, in order to ensure the efficiency of establishing lateral relationships, the grid step size is usually set to be no less than / >

(2) In S3③, 3×3×n is the number of grids in the x, y, and z directions. The number of grids in the z direction depends on the specific situation of the G code trajectory to ensure that the tool position points to be searched are not missed.

It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims (9)

1. A method for reconstructing lateral information of tool paths based on a spatial grid, characterized in that the method comprises the following steps: S1 determines the coordinates of each tool position point on the machining trajectory according to the G code on the machining trajectory, determines the limit coordinates of all tool position points along the coordinate axis direction, and divides the area included in the limit coordinates into grids to obtain multiple subdivided grids; S2, for each group of adjacent tool position points corresponding to the G code, determining the grids intersecting with the straight lines formed by connecting the group of adjacent tool position points, marking the intersecting grids, and traversing all tool position points to obtain the corresponding relationship between the tool position points and the grids; S3: for any tool position point _ps , a search range is constructed, and according to the correspondence between the tool position point and the grid established in step S2, the distance between the tool position point corresponding to each grid and the tool position point _ps is calculated, and the tool position point with the closest distance is taken as the lateral point of the tool position point _ps , and in this way, the lateral points of all tool position points are obtained, that is, the lateral information of the tool trajectory is obtained; The construction of the search scope is performed according to the following steps: S31 determines the offset direction of the tool position point _ps and the tool path interval between the cutting trajectories, and offsets the tool position point _ps according to the offset direction to obtain an offset point; S32 takes the grid where the offset point is located as the center and presets the search radius to determine the search range. 2. A method for reconstructing lateral information of tool paths based on spatial grids as described in claim 1, characterized in that, in S1, the processing trajectory is a cutting trajectory, and the processing trajectory has multiple parallel tool paths. 3. A method for reconstructing lateral information of tool paths based on a spatial grid as described in claim 1 or 2, characterized in that before step S2, each tool position point needs to be assigned an index number consistent with the size of the sequence in sequence. 4. The method for reconstructing lateral information of tool paths based on spatial grids according to claim 3, characterized in that, in step S2, the marking of intersecting grids is performed in the following manner: When the straight line formed by adjacent tool point locations is in the same grid, the adjacent tool point locations are used to mark the grids at the same time; when the straight line formed by adjacent tool point locations p _i and p _i+1 are not in the same grid, the grid where tool point location p _i is located is marked with the index number of tool point location p _i , and the other grids intersecting with the straight line and the grid of the tool point location p _i+1 are marked with the index number of tool point location p _i+1 . 5. A method for reconstructing lateral information of a tool trajectory based on a spatial grid as described in claim 1, characterized in that, for the grids in the search range, grids corresponding to grids with index numbers greater than and less than the index number corresponding to the tool position point _ps are respectively established into sets V ⁺ and ^V- , grid points in sets V ⁺ and ^V- with index numbers between the index numbers of the first and last boundary points of the single tool trajectory where the tool position point _ps is located are eliminated, and the set formed by the remaining grids is used as a new search range. 6. A method for reconstructing lateral information of a tool trajectory based on a spatial grid as claimed in claim 5, characterized in that the first and last boundary points of the single tool trajectory where the tool position point _ps is located are determined in the following manner: According to the index number of the tool position point _ps , on the single tool trajectory where _ps is located, search is performed in two directions with index numbers greater than and less than the index number of the tool position point _ps ; when a straight line formed by connecting two adjacent tool position points on the single tool trajectory is not parallel to the direction of the single tool trajectory, the tool position point closer to _ps among the two adjacent tool position points is one of the head and tail boundary points of the single tool trajectory. 7. A method for reconstructing lateral information of tool trajectory based on spatial grid as described in claim 1, characterized in that the preset search radius is 3×3×n, and the search step size in the X and Y axis directions is 3 grids, and n is the step size in the Z direction, which is set according to actual conditions. 8. A method for reconstructing lateral information of tool paths based on spatial grids as described in claim 3, characterized in that, according to the correspondence between the tool position points and the grids established in step S2, the distance between the tool position point corresponding to each grid and the tool position point _ps is calculated, specifically: according to the index number corresponding to each grid, the tool position point corresponding to the index number is obtained, and the distance from the tool position point corresponding to the index number to the tool position point _ps is calculated. 9. A method for reconstructing lateral information of tool paths based on spatial grids as described in claim 2, characterized in that, in step S1, when the grid is divided, the spacing between grids is set to [d/8, d/4], where d is the spacing between parallel tool paths.