Speed planning method for uncertain interval

Abstract

The application particularly relates to a speed planning method of an uncertain interval, which is a speed planning method of an uncertain interval, first, a chord height error model is adopted to recognize feature points of tool position points, the feature points are candidate points of the uncertain interval; second, the feature tool position points are further compressed based on joint constraints of adjacent tool position corner deviation, curvature variation and other geometric characteristics; third, tool position points with similar geometric characteristics of original tool position points are in an interval, different intervals can be obtained according to chord height error, adjacent deviation angle and curvature variation threshold value, so that reasonable speed can be planned. The purpose is to set different threshold values according to different tool performance and machining speed requirements, so that the optimal interval can be selected in multiple interval divisions, and a basis for subsequent simple and efficient speed planning is provided.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of tool speed planning of numerical control machine tools, and particularly relates to a speed planning method of uncertain intervals. BACKGROUND

[0002] With the development of science and technology, numerical control machine tools play an increasingly important role in the field of mechanical processing. Although China started late, the speed planning of tool trajectories has been gradually improved after decades of development, but there are still some defects, such as it is difficult to plan the speed in the same speed interval, accurate speed planning is not needed, accurate speed planning of tool trajectories will produce large speed fluctuations, and affect the surface quality.

[0003] The traditional speed planning method for tools on numerical control machine tools is to plan the speed of each tool position accurately according to different tool positions on the tool trajectory. The tool speed is closely related to the tool trajectory. When the tool moves from one tool position to the next tool position, the speed of each position is different, so the tool speed needs to be changed frequently. This kind of speed that changes quickly and slowly easily causes tool fluctuation, and cannot obtain a relatively smooth machining surface. SUMMARY

[0004] In order to solve the above problems, the application provides a speed planning method of uncertain intervals. The method divides the uncertain intervals of a section of tool positions to be processed according to different chord height error, adjacent tool position rotation angle deviation, curvature change and other threshold values, so as to plan reasonable machining sections and reasonable tool speeds.

[0005] To achieve the above application purposes, the technical solution adopted by the application is as follows: a speed planning method of uncertain intervals, comprising the following steps:

[0006] S1: selecting a section of tool positions to be planned, using a chord height error model to extract feature points of the section of tool positions as candidate points of uncertain interval boundaries;

[0007] S2: compressing the tool positions to be planned according to the feature points selected in step S1 and the geometric feature values between the feature points and adjacent tool positions, obtaining segmented intervals, and determining the end points of each segmented interval in the uncertain interval;

[0008] S3: selecting different chord height error threshold values in the chord height error model, and the geometric feature values between the feature points and adjacent tool positions, repeating the above steps S1 and S2, obtaining an array of candidate points of uncertain interval boundaries and an array of segmented intervals;

[0009] S4: determining the optimal chord height error threshold value and the optimal segmentation interval;

[0010] S5: planning the speed in each segmentation interval based on the geometric parameters in each segmentation interval.

[0011] Preferably, the specific method of extracting feature points by using the chord height error model in step S1 is as follows:

[0012] S1.1: setting all points on the tool position of the planned speed, setting the chord height error threshold value d r as a control factor;

[0013] S1.2: taking the starting point of the tool position as the initial point, selecting the position of the point j away from the starting point as the terminal point; calculating the midpoint between the initial point and the terminal point, and the distance d after connecting the initial point and the terminal point in a straight line;

[0014] S1.3: if d is greater than d r , then the next point at the starting point is taken as the new initial point, and step S1.2 is repeated; if d is less than d r , then the terminal point is saved as a candidate point of the boundary of the uncertain interval, and the saved terminal point is taken as the new initial point, and step S1.2 is repeated.

[0015] Preferably, the geometric feature values between adjacent feature points in step S2 include the angle, curvature, and distance ratio between adjacent tool positions.

[0016] Preferably, the specific method of compressing the tool positions to be planned to obtain the segmentation interval is as follows: setting the threshold values of the angle deviation, curvature change, and adjacent distance ratio between adjacent tool positions, calculating the angle, curvature, and distance ratio between the candidate point and adjacent tool positions, if the angle deviation, curvature, and distance ratio between the candidate point and the front and rear tool positions are less than the corresponding threshold values, then the candidate point is integrated into the same interval; otherwise, the candidate point is the boundary point of the uncertain interval.

[0017] Preferably, in step S4, the specific method of determining the optimal chord height error threshold value and the optimal segmentation interval is as follows: calculating the curvature, tangent, and chord height error in each segmentation interval in each group of segmentation intervals; if the geometric features in each segmentation interval in a group of segmentation intervals are close and the total number of interval segments is the least, then the group of segmentation intervals is considered as the optimal segmentation interval.

[0018] Preferably, the geometric parameters in each segmentation interval in step S5 include the curvature, tangent, and chord height error.

[0019] Preferably, in step S5, the specific method for planning the speed in each sub-interval is as follows: the curvature of each tool position is calculated, the average curvature of each sub-interval is calculated according to the curvature of each tool position and the number of tool positions, and the speed in each sub-interval is planned based on the following formula:

[0020]

[0021]

[0022] wherein Q i is the curvature, R is the radius, F is the calculated interval speed, and A is the normal acceleration.

[0023] Preferably, a linear speed is used for transition between adjacent sub-intervals.

[0024] An electronic device, comprising,

[0025] one or more processors;

[0026] a storage device for storing one or more programs;

[0027] When the one or more programs are executed by the one or more processors, the one or more processors implement the above-described speed planning method for uncertain intervals.

[0028] A computer readable medium, the readable medium storing a computer program, the computer program being executed by a processor to implement the above-described speed planning method for uncertain intervals.

[0029] The present application has the following beneficial effects:

[0030] 1) The present application can reasonably divide the uncertain intervals according to not using the chord height error model in solving the tool path, in combination with the threshold of the corner deviation and the curvature change of adjacent tool positions, so as to ensure that the same speed planning is used for path control under the condition that the geometric characteristics of the tool path are similar; the present application sets different thresholds according to different tool performance and processing speed requirements, so that the optimal interval can be selected from multiple interval divisions, thereby providing a basis for subsequent simple and efficient speed planning;

[0031] 2) The method of the present application places the tool positions with similar geometric characteristics in the original tool positions in an interval, and the points exceeding the set threshold are used as interval division points, so that a plurality of interval segments with different numbers are divided according to different thresholds, the average speed of each interval is obtained according to the average curvature of each interval, and the speed of the entire tool path is reasonably planned, and the adjacent intervals are transitioned through linear speed due to different planning speeds. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 This is a schematic diagram of the overall process of the present invention;

[0033] Figure 2 This is a schematic diagram of the tool trajectory during the operation of the present invention;

[0034] Figure 3 This is a schematic diagram illustrating the division of embodiments in this invention. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0036] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0037] This invention provides a speed planning method for uncertain intervals. This method, based on the speed planning of uncertain intervals, firstly uses a chord height error model to identify characteristic points of the tool position, which are candidate points for uncertain intervals. Secondly, it further compresses the characteristic tool positions based on joint constraints of geometric characteristics such as the rotation angle deviation and curvature change of adjacent tool positions. Thirdly, it ensures that tool positions with similar geometric characteristics are placed in one interval, rather than precisely calculating the geometric characteristic value of each point; points exceeding a threshold are used as interval division points. Finally, different values ​​can be set according to the chord height error, adjacent deviation angle, and curvature change threshold to obtain different interval divisions. These uncertain intervals are further used to plan reasonable speeds based on the geometric characteristics of the tool positions within the interval, thus realizing the speed planning method for uncertain intervals.

[0038] The uncertain intervals described in this invention refer to the uncertain number of segments into which a tool position to be planned is divided. This invention aims to divide intervals based on speed, thereby ensuring that the speed within each segment can be the same, thus significantly reducing tool speed variations.

[0039] Specifically, such as Figures 1-2 As shown, a velocity planning method for uncertain intervals includes the following steps:

[0040] S1: Regardless of whether it's row cutting or ring cutting, select a section of tool positions with the planned speed, and use the chord height error model to extract feature points of this section of tool positions as candidate points for the boundary of the uncertain interval; the specific method for extracting feature points using the chord height error model is as follows:

[0041] S1.1: Set all points on the tool position where the speed to be planned is to be set, and set the chord height error threshold d. r As a control factor;

[0042] S1.2: Take the starting point of the tool position as the initial point, and select a position j points away from the starting point as the ending point; calculate the distance d from the midpoint between the initial point and the ending point to the straight line connecting the initial point and the ending point;

[0043] S1.3: If d is greater than d r If d is less than d, then the next point from the starting point is taken as the new initial point, and step S1.2 is repeated; r If so, save the endpoint as a candidate point for the boundary of the uncertain interval, and use the saved endpoint as the new initial point to repeat step S1.2.

[0044] Specifically, input the tool position points P0, ..., P n Combined with the chord height error threshold d r As a control factor, let P k Starting from point P j As the endpoint, where 0≤k≤j-2, k+2≤j≤n, choose the intermediate point P. i , k < i < j, calculate P i to line P k P j The distance d; compare d with the threshold d r The size, if d is greater than d r Continue searching, otherwise save P. j Point, with P k =P j As a new starting point, P j =P j+2 As the new endpoint, continue the search until all tool points on the segment have been traversed, and the saved points serve as candidate points for the boundaries of the uncertain interval.

[0045] S2: Based on the feature points selected in step S1 and the geometric feature values ​​between the tool points adjacent to the feature points, the tool points of the planned speed are compressed to obtain segmented intervals, and the endpoints of each segmented interval in the uncertain interval are determined; the geometric feature values ​​between adjacent feature points include the rotation angle, curvature, and distance ratio between adjacent tool points.

[0046] The specific method for compressing the planned speed of the tool position points to obtain the segmented intervals is as follows: setting the threshold values of the corner deviation, the curvature variation, and the adjacent distance ratio between adjacent tool position points, calculating the corner, the curvature, and the distance ratio (the adjacent distance ratio and the uniformity of the distance between the control points) between the candidate point and the adjacent tool position points, if the corner deviation, the curvature, and the distance ratio between the candidate point and the front and rear tool position points are less than the corresponding threshold values, the candidate point is integrated into the same interval; otherwise, the candidate point is the boundary point of the uncertain interval. That is, when the compression segmentation is performed, the front and rear tool position points adjacent to the candidate point (the tool position points may not belong to the candidate point) are calculated for the corner deviation, the curvature, and the distance ratio between the two points, and the calculated corner deviation, curvature, and distance ratio are compared with the set threshold values of the corner deviation, curvature, and distance ratio, if the calculated values are less than the threshold values, the candidate point is in the same segmented interval; if the calculated values of the corner deviation, the curvature, and the distance ratio between two points are greater than the threshold values in the calculation process, the candidate point is taken as the boundary point of the segmented interval.

[0047] Finally, a plurality of segmented intervals and the end points of the first and last points on each segmented interval are obtained.

[0048] S3: selecting the chord height error threshold value in different chord height error models, the feature points, and the geometric feature values between the feature points and the tool position points adjacent to the feature points, and repeating the above steps S1 and S2 to obtain a plurality of candidate points of the uncertain interval boundaries and a plurality of segmented intervals; that is, when different chord height error threshold values and geometric feature values between adjacent feature points are selected, a plurality of segmented intervals can be obtained, and the number of segments in each group of segmented intervals is different or the segmented positions are different.

[0049] S4: determining the optimal chord height error threshold value and the optimal segmented interval; the specific method for determining the optimal chord height error threshold value and the optimal segmented interval is as follows: calculating the curvature, the tangent, and the chord height error in each segment in each group of segmented intervals; if the geometric features in each segment in a group of segmented intervals are close and the total number of segmented intervals is the least, the group of segmented intervals is considered as the optimal segmented interval.

[0050] S5: planning the speed in each segmented interval based on the geometric parameters in each segmented interval, wherein the geometric parameters in each segmented interval include the curvature, the tangent, and the chord height error; the specific method for planning the speed in each segmented interval is as follows: calculating the curvature of each tool position point, calculating the average curvature of each segmented interval according to the curvature of each tool position point and the number of tool position points, and planning the speed in each segmented interval based on the following formula, so as to ensure that the tool speed is the same in one segmented interval, and the tool speed in the next segmented interval is used after the transition to the next segmented interval, thereby avoiding the tool vibration caused by the different speeds of the tool at each tool position point, and thereby avoiding the problem of uneven machining surface.

[0051]

[0052]

[0053] The above Q i Let R be the curvature, F be the radius, F be the calculated interval velocity, and A be the normal acceleration.

[0054] Between adjacent segmented intervals, a linear velocity is used for transition, thereby enabling velocity planning for the uncertain intervals of the entire trajectory. The linear velocity is the velocity at the end of the previous segment, which is linearly added to or subtracted from the velocity at the beginning of the next segment.

[0055] In summary, when solving tool path problems, this invention can reasonably divide the uncertainty interval, ensuring that the same speed planning is used for trajectory control strategies when the geometric characteristics of the tool path are similar. This invention can set different thresholds according to different tool performance and machining speed requirements, thereby generating the optimal uncertainty interval.

[0056] The present invention also provides an electronic device, comprising: one or more processors; a storage device for storing one or more programs; wherein when the one or more programs are executed by the one or more processors, the one or more processors implement the above-described speed planning method for uncertain intervals.

[0057] The present invention also provides a computer-readable medium storing a computer program that, when executed by a processor, implements the above-described speed planning method for uncertain intervals.

[0058] Example

[0059] The toolpath of a selected program segment consists of 29 tool positions, such as... Figure 3 As shown in figure a, in order to calculate the same speed range, a chord height error threshold E is set. thr =0.1, distance ratio L thr =5, curvature ratio threshold Q thr =2. Based on the error threshold, obtain the characteristic cutter positions of this cutter position segment, such as... Figure 3 As shown in b, the square knife site is the characteristic knife site.

[0060] Furthermore, the curvature and distance of the characteristic cutter site and its adjacent original cutter sites are calculated. 1 / L thr <L i <L thr Or 1 / Q thr <Q i <Q thr This indicates that within a threshold range, the feature knife points are merged into the interval. For example... Figure 3As shown in Fig. 14, the hollow dots are the start and end points of the constant speed intervals, 14 tool position points are combined into intervals, through the uncertain interval division, finally four different speed intervals are obtained, the speed in each interval is consistent, and the speed in different intervals is different.

[0061] The above-described embodiments are only to describe the preferred modes of the present application, and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications, variations, modifications, and replacements of the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A speed planning method of an uncertain interval, characterized by, The method comprises the following steps: S1: selecting a section of tool position with a planned speed, and extracting feature points of the tool position in the section as candidate points of the boundary of the uncertain interval by using a chord height error model; S2: compressing the tool position with the planned speed according to the feature points selected in step S1 and geometric characteristic values between the tool positions adjacent to the feature points, obtaining a segmented interval, and determining end points on each segmented interval in the uncertain interval; S3: selecting chord height error thresholds in different chord height error models, feature points, and geometric characteristic values between the tool positions adjacent to the feature points, repeating the above steps S1 and S2, and obtaining candidate points of the boundary of the uncertain interval and segmented intervals; S4: determining an optimal chord height error threshold and an optimal segmented interval; The specific method for compressing the tool position with the planned speed to obtain the segmented interval is as follows: setting threshold values of an angle deviation, a curvature change, and a distance ratio between adjacent tool positions, calculating an angle, a curvature, and a distance ratio between the candidate points and the adjacent tool positions, and if the angle deviation, the curvature, and the distance ratio between the candidate points and the front and rear tool positions are less than the corresponding threshold values, the candidate points are integrated into the same interval; otherwise, the candidate points are boundary points of the uncertain interval; The specific method for determining the optimal chord height error threshold and the optimal segmented interval is as follows: calculating the curvature, the tangent, and the chord height error in each segmented interval in each group of segmented intervals; if the geometric characteristics in each segmented interval in a group of segmented intervals are close and the total number of interval segments is the least, the group of segmented intervals is considered as the optimal segmented interval; S5: planning the speed in each segmented interval based on geometric parameters in the segmented interval.

2. The method of claim 1, wherein: The specific method for extracting the feature points by using the chord height error model in step S1 is as follows: S1.1: Set all points on the tool position of the speed to be planned, set the chord height error threshold d r as a control factor; S1.2: taking the starting point of the tool position as an initial point, selecting a position j points away from the starting point as a terminal point, calculating a midpoint between the initial point and the terminal point, and the distance d between the initial point and the terminal point after the straight line connection. S1.3: If d is greater than d r then the next point at the starting point is taken as a new initial point, and step S1.2 is repeated; if d is less than d r then the end point is saved as a candidate point for the boundary of the uncertain interval, and step S1.2 is repeated with the saved end point as the new initial point.

3. The method of claim 2, wherein: The geometric characteristic values between the tool positions adjacent to the feature points in step S2 include an angle, a curvature, and a distance ratio between the adjacent tool positions.

4. The method of claim 1, wherein: The geometric parameters in each segmented interval in step S5 include a curvature, a tangent, and a chord height error.

5. The method of claim 4, wherein: In step S5, the specific method of planning the speed in each segment interval is: calculating the curvature of each tool position, calculating the average curvature of each segment interval according to the curvature of each tool position and the number of tool positions, and planning the speed in each segment interval based on the following formula: ; ； where: Q i is the curvature, R is the radius, F is the found segment velocity, and A is the normal acceleration.

6. The method of claim 1, wherein: Linear speed is adopted for transition between adjacent segmented intervals.

7. An electronic device, comprising: The method comprises the following steps: one or more processors; a storage device for storing one or more programs; when the one or more programs are executed by the one or more processors, the one or more processors implement the speed planning method for the uncertain interval as claimed in any one of claims 1-6.

8. A computer readable medium storing a computer program, characterized in that: The computer program is executed by the processor to implement the speed planning method for the uncertain interval as claimed in any one of claims 1-6.

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