Interpolation Method for Data-Driven Computer Numerical Control System

Abstract

The present invention relates to the field of numerical control interpolation technology, and particularly relates to an interpolation method for a computer numerical control system based on data driving. The method includes: obtaining each path point on a linear feed path, and obtaining starting direction windows with different step lengths starting from the starting path point; determining the similarity in each direction according to the path point features within the starting direction window; forming a similarity sequence; determining a cut-off window according to the change of elements in the similarity sequence and the aspect ratio of the starting direction window; performing backward analysis to obtain a backward window; determining a limiting window according to the numerical values of the similarity in each direction of the backward window and the starting direction window at the same path point, and performing speed limitation on the path points within the limiting window with the cut-off coefficient corresponding to the limiting window; traversing all path points, and re-planning the feed speed according to the speed limitation of all path points. The present invention can perform more accurate feed speed planning, reduce the consistency deviation, and improve the interpolation smoothness and tool path accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of numerical control interpolation, and particularly relates to an interpolation method for a computer numerical control system based on data driving. Background Art

[0002] Numerical control interpolation is to make up for the result that the machining path of a workpiece is represented by discrete points in CAD / CAM software, and to control the movement of a tool between path points. However, frequent starting and stopping at the path point positions causes great damage to the linear motor, and the impact vibration on the overall movable disk during starting and stopping is large, which easily aggravates the wear of the numerical control machine tool. For the planning of the machining path of complex curve and surface, NURBS (Non-uniform Rational B-spline) curves are often used for feed speed planning and interpolation point position calculation to avoid the problems of low machining efficiency and feed fluctuation caused by approximating the curve with a large number of tiny segments.

[0003] In the related art, by splitting the 1 / 2 journey and performing speed interpolation on each as an acceleration / deceleration section respectively, in this way, due to the different complexity of tool paths at different positions of the workpiece, the traditional planning scheme by splitting the path in a fixed ratio will result in inconsistent machining speeds for continuous surfaces during machining, easily causing a consistency deviation in the cutting path and insufficient interpolation smoothness, thus affecting the machining accuracy in the complex tool path stage. Summary of the Invention

[0004] In order to solve the technical problem that in the related art, the method of splitting the path in a fixed ratio will result in inconsistent machining speeds for continuous surfaces during machining, easily causing a consistency deviation in the cutting path and insufficient interpolation smoothness, thus affecting the machining accuracy in the complex tool path stage, the present invention provides an interpolation method for a computer numerical control system based on data driving, and the specific technical solution adopted is as follows:

[0005] The present invention proposes an interpolation method for a computer numerical control system based on data driving, and the method includes:

[0006] Obtain each path point on the linear feed path, and obtain the starting direction window at different step lengths starting from the starting path point; wherein, the window is the minimum circumscribed rectangle from the starting path point to the ending path point;

[0007] Determine the similarity degree in each direction of each path point according to the total length of the tool path formed by the path points in the starting direction window, the number of path points, and the change in the included angle between the front and rear paths; determine the similarity degree sequence of the similarity degrees at different step lengths; according to the change of the elements in the similarity degree sequence and the aspect ratio of the starting direction window at different step lengths, determine the cut-off coefficient at the current step length, and perform step length cut-off according to the cut-off coefficient to determine the cut-off window;

[0008] Starting from the termination path point of the cut-off window, traverse and select the window in the direction of the starting path point without repetition, which is denoted as the reverse window; according to the similarity values of the reverse window and the forward window at the same path point under different step lengths, divide the cut-off window into different restricted windows, and use the cut-off coefficient corresponding to the restricted window to limit the speed of the path points within the restricted window;

[0009] Traverse all path points, and re-plan the feed speed according to the speed limits of all path points.

[0010] Further, determining the similarity of each path point according to the total length of the tool path formed by the path points within the forward window, the number of path points, and the angular change of the front and rear paths includes:

[0011] Taking each path point as the last path point of the window, determining the straight line formed by the starting path point and the next path point within the corresponding window as the starting direction straight line, and determining the straight line formed by the second-to-last path point and the last path point of the window as the termination direction straight line;

[0012] Taking the included angle formed by the starting direction straight line and the termination direction straight line as the path included angle, calculating the negative value of the included angle value of the path included angle, and performing normalization processing to obtain the included angle index;

[0013] Taking the ratio of the total length of the tool path within the window to the number of path points within the window as the density analysis index;

[0014] Determining the similarity of the last path point of the window according to the included angle index and the density analysis index.

[0015] Further, determining the similarity of the last path point of the window according to the included angle index and the density analysis index includes:

[0016] Taking the product of the density analysis index and the included angle index, and performing normalization processing as the similarity of the last path point of the window.

[0017] Further, the determining the similarity sequence of the similarities under different step lengths includes:

[0018] Arrange the similarities of different path points in ascending order of the step value to obtain the similarity sequence.

[0019] Further, the determining the cut-off coefficient at the current step according to the change of the elements in the similarity sequence and the aspect ratio of the forward window under different step lengths includes:

[0020] Calculate the average value of the aspect ratios of the forward windows corresponding to the current step and all previous steps to obtain the average aspect ratio;

[0021] Take the difference between the mean aspect ratio and the aspect ratio of the starting window corresponding to the current step size as the first cut-off coefficient;

[0022] Perform a first-order difference operation on the elements in the similarity sequence, take the absolute value to obtain the difference value, and take the product of the sum of all difference values and the first cut-off coefficient as the similarity change index under the current step size;

[0023] Calculate the difference between the similarity change index and the minimum value of the elements in the similarity sequence as the cut-off coefficient.

[0024] Further, perform step size cut-off according to the cut-off coefficient to determine the cut-off window, including:

[0025] When the cut-off coefficient is greater than or equal to 1, take the window corresponding to the step size as the cut-off window.

[0026] Further, divide the cut-off window into different restricted windows according to the similarity values in each direction of the backward window and the starting window at the same path point under different step sizes, including:

[0027] Within the cut-off window, take the position of the path point corresponding to any step size as the analysis position;

[0028] Determine the restriction coefficient for dividing the cut-off window according to the comparison of the similarity values in each direction of the starting window and the backward window corresponding to the analysis position;

[0029] Determine the restricted step size according to the value of the restriction coefficient at each step size, and divide the cut-off window into different restricted windows according to the restricted step size.

[0030] Further, determine the restriction coefficient for dividing the cut-off window according to the comparison of the similarity values in each direction of the starting window and the backward window corresponding to the analysis position, including:

[0031] Determine the starting window from the starting path point to the analysis position as the starting analysis window, and determine the window from the last path point of the cut-off window to the analysis position as the backward analysis window;

[0032] Take the ratio of the similarity in each direction of the backward analysis window to the similarity in each direction of the starting analysis window as the restriction coefficient.

[0033] Further, perform speed restriction on the path points within the restricted window with the cut-off coefficient corresponding to the restricted window, including:

[0034] Calculate the mean value of the cut-off coefficients of all path points within the restricted window as the cut-off mean value;

[0035] Calculate the difference between the unit value 1 and the cut-off mean value as the speed restriction weight;

[0036] Use the product value of the speed limit weight and the maximum speed as the feed speed limit for the path points within the limit window.

[0037] Further, traverse all path points and re-plan the feed speed according to the speed limits of all path points, including:

[0038] Perform NURBS smoothing interpolation on the feed speed limit of each path point in time sequence to achieve the feed speed planning of the tool path.

[0039] The present invention has the following beneficial effects:

[0040] In the embodiment of the present invention, through the comprehensive analysis of the starting window and the returning window for different path points, combined with the total length of the tool path formed by the path points within the starting window, the number of path points, and the angular change of the front and rear paths, the similarity in each direction is determined, which is convenient to achieve the cut-off of the path complexity according to the similarity in each direction. The adjacent path points with relatively consistent path complexity are analyzed as a whole, and then through the traversal of the returning window within the cut-off window, the refined analysis of the tool path complexity in different directions is realized, and the limit window is obtained. The limit window integrates the tool path analysis in different direction dimensions, thus avoiding the consistency deviation caused by only analyzing the tool path in one direction. In summary, the embodiment of the present invention conducts a more refined analysis of the tool path through the different direction dimension features of the starting window and the returning window, solves the unreasonable splitting scheme caused by the traditional planning scheme through fixed ratio path splitting, makes the adjustment of the interpolation point parameter results in the tool path process insufficient for the machining integrity and interpolation smoothness of the entire surface. This solution divides the path with more consistent tool path representation into a limit window, conducts tool path planning within the same limit window, ensures the stable effect of the interpolation points, improves the interpolation smoothness, reduces the consistency deviation, and thus improves the tool path accuracy. Description of the Drawings

[0041] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0042] Figure 1 It is a flowchart of an interpolation method for a data-driven computer numerical control system provided by an embodiment of the present invention;

[0043] Figure 2 It is a schematic diagram of the acceleration and deceleration change of the tool path provided by an embodiment of the present invention. Detailed Embodiments

[0044] To further elaborate on the technical means and effects adopted by the present invention to achieve the intended invention purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation manner, structure, features, and effects of an interpolation method for a data-driven computer numerical control system according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs.

[0046] The following specifically describes the specific solution of an interpolation method for a data-driven computer numerical control system provided by the present invention in conjunction with the accompanying drawings.

[0047] Please refer to Figure 1 , which shows a flowchart of an interpolation method for a data-driven computer numerical control system provided by an embodiment of the present invention. The method includes:

[0048] S101: Obtain each path point on the linear feed path, and obtain the starting window at different step lengths starting from the starting path point; wherein, the window is the minimum circumscribed rectangle from the starting path point to the ending path point.

[0049] CNC interpolation is to make up for the result that the machining path of the workpiece represented by discrete points in CAD / CAM software will cause the main shaft to move frequently between path points, and frequent starting and stopping at the target point position will cause greater damage to the linear motor, and the impact vibration on the overall moving plate during starting and stopping is relatively large, which is likely to exacerbate the wear of the CNC machine tool.

[0050] The prior art uses NURBS (Nonuniform rational B-spline) curves for feed speed planning and interpolation point position calculation for the planning of complex curve and surface machining paths to avoid problems such as low machining efficiency and feed fluctuations caused by approximating curves with a large number of tiny segments.

[0051] However, due to the different complexities of the machining paths of the workpiece and the inconsistent complexities corresponding to different machining paths. For example, a certain section of the machining path requires "tooth-shaped" feed, while the subsequent section of the machining path is "linear" feed. Therefore, if interpolation is performed at a uniform speed, the accuracy of the "tooth-shaped" feed may vary, which will in turn affect the quality of the workpiece. Based on this, this solution performs interpolation control on the feed speed through tool path analysis to achieve a more refined feed planning.

[0052] In the embodiments of the present invention, a numerical control engineering software (such as mastercam, rhinocam, etc.) can be used to construct the processing model of the current product, input the size of the processed blank material, and the numerical control software generates the tool path according to the contour lines of the part, numbers each path point, and completes the acquisition of the path points of the processing model.

[0053] It can be understood that referring to Figure 2 , Figure 2 is a schematic diagram of the feed acceleration and deceleration changes provided by an embodiment of the present invention; analyze the movement conditions generated by adjacent path points: for the "S" - type acceleration and deceleration method formed by path planning, it is shown as:

[0054] The acceleration - increasing section is from 0 to t1, with a constant positive jerk j to increase the acceleration a from 0 to a preset positive value; the uniform - acceleration section is from t1 to t2, accelerating with a constant acceleration a; the deceleration - increasing section is from t2 to t3, with a constant negative jerk j to decelerate the acceleration a from the preset positive value to 0; the constant - speed section is from t3 to t4, running at a constant speed v; the deceleration section is from t4 to t5, with a constant negative jerk j to decrease the acceleration a from 0 to a preset negative value (where the preset positive value and the preset negative value are opposite to each other); the uniform - deceleration section is from t5 to t6, decelerating with a constant acceleration a; the deceleration - decreasing section is from t6 to t7, with a constant positive jerk j to increase the acceleration a from the preset negative value to 0.

[0055] It should be noted that in the embodiments of the present invention, the preset positive value can be specifically, for example, 0.1 m / s², and the preset negative value is - 0.1 m / s², and there is no limitation on this. The acceleration control is realized by the corresponding jerk, and then the "S" - type curve of the speed is realized.

[0056] It can be understood that when feeding between two adjacent path points, it will cause the speed to be overly uneven, and then lead to an unreasonable setting of the initial speed for the planned travel of the next path point. For example, the next path point requires a smaller feed speed due to a more complex processing shape, while the end speed of the previous path point is larger, resulting in an instantaneous deceleration that causes speed jitter between path points, leading to a large change in the feed, and then affecting the feed accuracy. Therefore, it is necessary to plan the speed limit between each section according to the complexity of the feed line.

[0057] In the embodiments of the present invention, first, regional planning needs to be carried out for different path points. Since the change in the feed complexity between adjacent path points is inconsistent, specific path - point classification can be carried out, and adjacent path points with the same complexity are classified into one category.

[0058] It should be noted that each step length represents the number of path points along the tool path starting from the starting path point. That is, when the step length is 5, it can represent 5 path points counted backward from the starting path point, and the minimum bounding rectangle of all path points between them is used as the starting window under the step length of 5. Thus, the starting window under each step length is obtained, which is convenient for subsequent analysis.

[0059] S102: Determine the anisotropy degree of each path point according to the total length of the tool path formed by the path points in the starting window, the number of path points, and the change in the included angle between the front and rear paths; determine the anisotropy degree sequence of different step lengths; according to the change of the elements in the anisotropy degree sequence and the aspect ratio of the starting window of different step lengths, determine the cut-off coefficient under the current step length, and perform step length cut-off according to the cut-off coefficient to determine the cut-off window.

[0060] Among them, the anisotropy degree is an index representing the tool path direction and tool path density at the position of the corresponding path point. The larger the value of the anisotropy degree, the more consistent the direction between the path point connections can be represented, and the longer the tool path formed by the path points, indicating that the tool path at the path point is smoother and a higher deceleration margin can be left. Since the total length of the tool path within adjacent path points is inconsistent, and the number of path points and the change in the tool path angle generated by two path points are also inconsistent, based on this, the specific calculation of the anisotropy degree can be carried out.

[0061] Among them, the number of path points includes the last path point. That is, when the step length is 5, the number of corresponding path points is 5.

[0062] Furthermore, in some embodiments of the present invention, determining the anisotropy degree of each path point according to the total length of the tool path formed by the path points in the starting window, the number of path points, and the change in the included angle between the front and rear paths includes: taking each path point as the last path point of the window, determining the straight line formed by the starting path point and the next path point in the corresponding window as the starting direction straight line, and determining the straight line formed by the second last path point and the last path point of the window as the termination direction straight line; taking the included angle formed by the starting direction straight line and the termination direction straight line as the path included angle, calculating the negative value of the numerical value of the path included angle, and performing normalization processing to obtain the included angle index; taking the ratio of the total length of the tool path within the window to the number of path points within the window as the density analysis index; determining the anisotropy degree of the last path point of the window according to the included angle index and the density analysis index.

[0063] That is to say, in the embodiments of the present invention, by analyzing the included angle change and the density analysis index, the anisotropy degree analysis is realized. The included angle change is mainly the included angle change corresponding to the starting path point and the last path point of the window. Therefore, in the embodiments of the present invention, by determining the starting direction line and the ending direction line, the path included angle is determined. The smaller the path included angle (the maximum is 180 degrees), the smaller the angle change between the path start and the path end is represented.

[0064] In the embodiments of the present invention, the opposite number of the value of the path included angle (this value only represents the numerical feature and does not include the angle feature) is directly calculated and normalized to be used as the included angle index. That is, the larger the included angle index is, the smaller the value of the corresponding path included angle is, and further the smaller the angle change between the path start and the path end is, and the smoother the path angle change within the corresponding window is.

[0065] Among them, the ratio of the total length of the tool path within the window to the number of path points within the window is used as the density analysis index. Usually, the path points are selected more densely in the complex area. And the specific calculation of the path point density is the ratio of the number of path points within the window to the total length of the tool path within the window. The greater the density is, the more complex the tool path within the window is represented.

[0066] Therefore, the density analysis index in the embodiments of the present invention is the reciprocal of the path point density (by directly calculating the ratio of the total length of the tool path within the window to the number of path points within the window). Thus, the larger the value of the density analysis index is, the longer the tool path length within the corresponding window is, and the fewer the number of path points is. At this time, there is more tool path deceleration margin and the tool path is smoother.

[0067] Therefore, according to the density analysis index, the smoothness effect of the path within the window can also be further characterized. The embodiments of the present invention can combine the included angle index and the density analysis index to perform the anisotropy degree analysis.

[0068] Further, in some embodiments of the present invention, according to the included angle index and the density analysis index, the anisotropy degree of the last path point of the window is determined, including: normalizing the product of the density analysis index and the included angle index as the anisotropy degree of the last path point of the window.

[0069] Among them, the larger the value of the density analysis index is, the smaller the density is, the higher the deceleration margin of the tool path is, and the larger the included angle index is, the smaller the angle change between the path start and the path end is, and the smoother the path angle change within the corresponding window is. It can be known that both the density analysis index and the included angle index are positively correlated with the anisotropy degree. Therefore, the present invention directly calculates the product value of the density analysis index and the included angle index and normalizes it as the anisotropy degree of the last path point of the window.

[0070] After obtaining the anisotropy degrees of each path point, they can be arranged in ascending order of the step values of the path point and the starting path point to obtain a similarity sequence of the anisotropy degrees at different step values. Moreover, based on the similarity sequence, different tool path conditions can be classified and analyzed. The classification in the embodiments of the present invention is mainly cut-off classification, that is, when a large change is detected, cut-off processing is performed and re-analysis is carried out. Thus, path points that are adjacent and have similar tool path conditions can be grouped into one category.

[0071] Further, in some embodiments of the present invention, according to the change of elements in the similarity sequence and the aspect ratio of the starting direction window at different step values, a cut-off coefficient at the current step value is determined, including: calculating the average value of the aspect ratios of the starting direction windows corresponding to the current step value and all previous step values to obtain the average aspect ratio value; taking the difference between the average aspect ratio value and the aspect ratio of the starting direction window corresponding to the current step value as the first cut-off coefficient; performing a first-order difference processing on the elements in the similarity sequence and taking the absolute value to obtain difference values, and taking the product of the sum of all difference values and the first cut-off coefficient as the similarity change index at the current step value; calculating the difference between the similarity change index and the minimum value of the elements in the similarity sequence as the cut-off coefficient.

[0072] Among them, the cut-off coefficient represents an index information for realizing step cut-off and taking the tool path within the corresponding step value range as a whole, and is used for cut-off judgment.

[0073] In the embodiments of the present invention, since the starting direction window will have an angle deflection characteristic as the step value increases, that is, the angle will have an accumulative deflection effect, and this accumulative deflection being too large will also lead to a complex tool path situation. Therefore, in the embodiments of the present invention, the deviation amplitude of the path is measured by the aspect ratio of the minimum circumscribed rectangle bounding box (Bounding Box function) of the path points within the current window.

[0074] Therefore, in the embodiments of the present invention, the average value of the aspect ratios of the starting direction windows corresponding to the current step value and all previous step values is calculated to obtain the average aspect ratio value, which characterizes the path deviation amplitude characteristics at all step values. And by calculating the difference between the average aspect ratio value and the aspect ratio of the starting direction window corresponding to the current step value as the first cut-off coefficient, the first cut-off coefficient represents the morphological change of the window, that is, the difference between the window morphologies of all previous step values and the window morphology at the current step value. The greater this difference, the greater the window change at the current step value.

[0075] Performing a first-order difference process on the elements in the similarity sequence can represent the change in similarity in each direction. The larger the sum value of all difference values, the greater the difference in similarity in each direction. At this time, the more necessary it is to perform cut-off analysis. Therefore, in the embodiments of the present invention, the first cut-off coefficient is used as the weight of the sum value of all difference values for analysis, and the product of the sum value of all difference values and the first cut-off coefficient is directly calculated as the similarity change index at the current step size.

[0076] As the step size changes, the similarity change index gradually increases. The similarity change index is compared with the minimum value of the elements in the similarity sequence, and the difference between the similarity change index and the minimum value of the elements in the similarity sequence is calculated as the cut-off coefficient. The cut-off coefficient represents the difference result between the similarity change index and the minimum value of the elements in the similarity sequence. When the value of the similarity change index is small, the value of the cut-off coefficient is small. As the value of the similarity change index increases, the cut-off coefficient also gradually increases, indicating that the complexity of the tool path is gradually increasing.

[0077] Further, in some embodiments of the present invention, step size cut-off is performed according to the cut-off coefficient to determine the cut-off window, including: when the cut-off coefficient is greater than or equal to 1, the window corresponding to the current step size is used as the cut-off window. That is, when the difference between the similarity change index and the minimum value of the elements in the similarity sequence is 1, it indicates that the cut-off requirement is met. Thus, the cut-off window is determined. Of course, in other embodiments of the present invention, other thresholds can also be set to achieve cut-off analysis, and this is not limited.

[0078] S103: Starting from the end path point of the cut-off window, non-repeatedly traverse and select a window in the direction of the start path point, denoted as the reverse window; according to the similarity values in each direction of the reverse window and the forward window at the same path point under different step sizes, the cut-off window is divided into different restricted windows, and the path points within the restricted window are speed-limited according to the cut-off coefficient corresponding to the restricted window.

[0079] Judge the situation of path direction variation generated after window extension: During the tool path process, the estimation of the speed requirement for the complex situation in the forward direction is insufficient, manifested as an obvious deviation in the tool path direction formed by a progressive change, and this deviation situation is masked by the long smooth path in the window during analysis, making it impossible to accurately analyze, resulting in poor timeliness of the data point response for workpiece interpolation, and the data points for interpolation do not reflect the hierarchy of the machining texture well (that is, the local approximation order of the NURBS curve is relatively high, resulting in non-smoothness of the local machining path).

[0080] In the embodiments of the present invention, after determining the cut-off window, the forward window stepping is stopped. Starting from the last path point (termination path point) of the cut-off window, a non-repeating traversal is performed in the direction of the starting path point to select a window, obtaining a reverse window. It should be noted that only path interpolation planning analysis is performed based on the starting window, and the corresponding tool path is still affected by the fineness error of the path point arrangement. By introducing the reverse window and performing integrated analysis of the forward and reverse windows, it can better represent the tool path analysis situation at each path point. The reverse window is used for deflection analysis at different step lengths, not only for judging abnormal output positions, but also for reflecting the instability of frequent path changes.

[0081] Further, in some embodiments of the present invention, according to the similarity values of the reverse window and the starting window at the same path point under different step lengths, the cut-off window is divided into different restricted windows, including: within the cut-off window, the path point position corresponding to any step length is used as the analysis position; according to the numerical comparison of the similarity values of the starting window and the reverse window corresponding to the analysis position, the restriction coefficient for dividing the cut-off window is determined; according to the numerical value of the restriction coefficient at each step length, the restricted step length is determined, and the cut-off window is divided into different restricted windows according to the restricted step length.

[0082] It can be understood that the starting window corresponding to the analysis position is the smallest circumscribed rectangle from the starting path point to the analysis position, and the reverse window corresponding to the analysis position is the smallest circumscribed rectangle from the termination path point to the analysis position. Since the overall cut-off window shows relatively consistent tool path changes during analysis, the greater the difference in similarity between the starting window and the reverse window corresponding to the analysis position, the more refined the cut-off window tool path consistency division can be performed from the analysis position.

[0083] Further, in some embodiments of the present invention, according to the numerical comparison of the similarity values of the starting window and the reverse window corresponding to the analysis position, the restriction coefficient for dividing the cut-off window is determined, including: determining the window from the starting path point to the analysis position as the starting analysis window, and determining the window from the last path point of the cut-off window to the analysis position as the reverse analysis window; taking the ratio of the similarity of the reverse analysis window to the similarity of the starting analysis window as the restriction coefficient.

[0084] The numerical comparison in the embodiments of the present invention is mainly to calculate the ratio. Directly taking the ratio of the similarity of the reverse analysis window to the similarity of the starting analysis window as the restriction coefficient, this restriction coefficient represents the restriction of the tool path consistency.

[0085] Further, in some embodiments of the present invention, the path points within the restriction window are speed-limited by the cut-off coefficient corresponding to the restriction window, including: calculating the mean value of the cut-off coefficients of all path points within the restriction window as the cut-off mean value; calculating the difference between the unit value 1 and the cut-off mean value as the speed limit weight; and taking the product value of the speed limit weight and the maximum speed as the feed speed limit for the path points within the restriction window.

[0086] It can be understood that when the value of the cut-off coefficient is greater than or equal to 1, it is divided into a cut-off window. Therefore, the cut-off coefficients within the restriction window are all less than 1, and the cut-off mean value is less than 1. The cut-off mean value represents the overall complexity of the feed path within the restriction window, and speed limitation can be performed based on this. The larger the value of the cut-off mean value, the more complex the feed path within the restriction window. Therefore, the speed needs to be reduced. Thus, the difference between the unit value 1 and the cut-off mean value is calculated as the speed limit weight, and the product value of the speed limit weight and the preset maximum speed is directly calculated as the feed speed limit for the path points.

[0087] Thus, the feed speed limit for each path point is determined and marked, facilitating subsequent interpolation planning according to the feed speed limit of each path point.

[0088] S104: Traverse all path points and re-plan the feed speed according to the speed limits of all path points.

[0089] In the embodiments of the present invention, a built-in NURBS interpolator can be used to perform NURBS smoothing interpolation on the feed speed limit of each path point in time sequence, realizing the feed speed planning of the tool path. That is to say, intermediate value interpolation is performed on the discrete feed speed limits of all path points to facilitate the planning of the speed throughout the feed path, generating a NURBS tool path and simulating and verifying it.

[0090] In the embodiments of the present invention, through comprehensive analysis of the starting window and the returning window for different path points, combined with the total length of the tool path formed by the path points in the starting window, the number of path points, and the angular change of the front and rear paths, the similarity in each direction is determined, which is convenient for achieving the cut-off of the path complexity according to the similarity in each direction. The adjacent path points with relatively consistent path complexity are analyzed as a whole, and then through the traversal of the returning window within the cut-off window, the refined analysis of the tool path complexity in different directions is realized, and a restricted window is obtained. The restricted window integrates the tool path analysis in different direction dimensions, thus avoiding the consistency deviation caused by tool path analysis based on only one direction. In summary, through the different direction dimension features of the starting window and the returning window, the embodiments of the present invention conduct more refined analysis on the tool path, solve the unreasonable splitting scheme caused by the traditional planning scheme through fixed-ratio path splitting, and make up for the insufficient adjustment of the interpolation point parameters in the tool path process for the machining integrity of the entire surface and the interpolation smoothness. This solution divides the paths with more consistent tool path representation into a restricted window, conducts tool path planning within the same restricted window, ensures the stable effect of the interpolation points, improves the interpolation smoothness, reduces the consistency deviation, and thus improves the tool path accuracy.

[0091] It should be noted that the above sequence of the embodiments of the present invention is only for description and does not represent the advantages or disadvantages of the embodiments. The processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multi-tasking and parallel processing are also possible or may be advantageous.

[0092] Each embodiment in this specification is described in a progressive manner. The same or similar parts among the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments.

Claims

1. An interpolation method for a computer numerical control system based on data driving, characterized in that, The method includes: Obtain each path point on the linear feed path, and obtain the starting direction window at different step lengths starting from the starting path point; wherein, the window is the minimum circumscribed rectangle from the starting path point to the ending path point. Determine the anisotropy degree of each path point according to the total length of the tool path formed by the path points within the starting direction window, the number of path points, and the change in the included angle between the front and rear paths; determine the anisotropy degree sequence of the anisotropy degrees at different step lengths; according to the change of the elements in the anisotropy degree sequence and the aspect ratio of the starting direction windows at different step lengths, determine the cut-off coefficient at the current step length, and perform step length cut-off according to the cut-off coefficient to determine the cut-off window. Starting from the ending path point of the cut-off window, traverse and select the window in the direction of the starting path point without repetition, denoted as the reverse direction window; according to the anisotropy degree values of the reverse direction window and the starting direction window at the same path point at different step lengths, divide the cut-off window into different restricted windows, and use the cut-off coefficient corresponding to the restricted window to limit the speed of the path points within the restricted window. Traverse all path points, and re-plan the feed speed according to the speed limits of all path points. The determining the cut-off coefficient at the current step length according to the change of the elements in the anisotropy degree sequence and the aspect ratio of the starting direction windows at different step lengths includes: Calculate the mean value of the aspect ratios of the starting direction windows corresponding to the current step length and all previous step lengths to obtain the mean aspect ratio. Take the difference between the mean aspect ratio and the aspect ratio of the starting direction window corresponding to the current step length as the first cut-off coefficient. Perform a first-order difference process on the elements in the anisotropy degree sequence, take the absolute value to obtain the difference value, and take the product of the sum value of all difference values and the first cut-off coefficient as the anisotropy degree change index at the current step length. Calculate the difference between the anisotropy degree change index and the minimum value of the elements in the anisotropy degree sequence as the cut-off coefficient. Dividing the cut-off window into different restricted windows according to the anisotropy degree values of the reverse direction window and the starting direction window at the same path point at different step lengths includes: Within the cut-off window, take the path point position corresponding to any step length as the analysis position. Determine the window from the starting path point to the analysis position as the starting direction analysis window, and determine the window from the last path point of the cut-off window to the analysis position as the reverse direction analysis window. Take the ratio of the anisotropy degree of the reverse direction analysis window to the anisotropy degree of the starting direction analysis window as the restriction coefficient. Determine the restricted step length according to the value of the restriction coefficient at each step length, and divide the cut-off window into different restricted windows according to the restricted step length.

2. The interpolation method of a data-driven computer numerical control system according to claim 1, characterized in that The determining the anisotropy degree of each path point according to the total length of the tool path formed by the path points within the starting direction window, the number of path points, and the change in the included angle between the front and rear paths includes: Take each path point as the last path point of the window, determine the straight line formed by the starting path point and the next path point within the corresponding window as the starting direction straight line, and determine the straight line formed by the second last path point and the last path point of the window as the ending direction straight line. Take the included angle formed by the starting direction straight line and the ending direction straight line as the path included angle, calculate the opposite number of the path included angle value, and perform normalization processing to obtain the included angle index. Take the ratio of the total length of the tool path within the window to the number of path points within the window as the density analysis index; Determine the anisotropy of the last path point of the window according to the included angle index and the density analysis index.

3. The interpolation method of a data-driven computer numerical control system according to claim 2, characterized in that, Determine the anisotropy of the last path point of the window according to the included angle index and the density analysis index, including: Normalize the product of the density analysis index and the included angle index as the anisotropy of the last path point of the window.

4. The interpolation method of a data-driven computer numerical control system according to claim 1, characterized in that, The anisotropy sequence for determining anisotropy at different step sizes includes: Arrange the anisotropies of different path points in ascending order of the step size value to obtain the anisotropy sequence.

5. The interpolation method of a data-driven computer numerical control system according to claim 1, wherein, Determine the cut-off window according to the cut-off coefficient, including: When the cut-off coefficient is greater than or equal to 1, take the window corresponding to the step size as the cut-off window.

6. The interpolation method of a data-driven computer numerical control system according to claim 1, characterized in that, Perform speed limitation on the path points within the restricted window with the cut-off coefficient corresponding to the restricted window, including: Calculate the mean value of the cut-off coefficients of all path points within the restricted window as the cut-off mean value; Calculate the difference between the unit value 1 and the cut-off mean value as the speed limitation weight; Take the product value of the speed limitation weight and the maximum speed as the feed speed for the path points within the restricted window.

7. An interpolation method for a computer numerical control system based on data driving according to claim 6, characterized in that Traverse all path points and re-plan the feed speed according to the speed limitations of all path points, including: Perform NURBS smoothing interpolation on the feed speed for each path point in time sequence to achieve the feed speed planning of the tool path.

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