Interpolation method of computer numerical control system based on data driving

Abstract

The invention relates to the technical field of numerical control interpolation, in particular to an interpolation method of a computer numerical control system based on data driving. The method comprises the following steps: acquiring each path point on a linear feeding path, and acquiring a starting window under different synchronization lengths from a starting path point; determining the likelihood in each direction according to the characteristics of the path points in the starting window; forming a likelihood sequence; determining a cut-off window according to the change of elements in the likelihood sequence and the length-width ratio of the starting window; performing reverse analysis to obtain a reverse window; determining a limiting window according to the values of the likelihood of the returning window and the starting window in each direction at the same waypoint, and limiting the speed of the waypoint in the limiting window according to a cut-off coefficient corresponding to the limiting window; and traversing all the path points, and re-planning the feeding speed according to the speed limitation of all the path points. According to the method, more accurate feeding speed planning can be carried out, the consistency deviation is reduced, and the interpolation fluency and the feeding precision are improved.

Description

Technical Field

[0001] The invention relates to the technical field of numerical control interpolation, and in particular to an interpolation method of a computer numerical control system based on data drive. Background Art

[0002] CNC interpolation is to compensate for the result that the machining path of the workpiece is represented by discrete points in CAD / CAM software, and to control the movement of the tool between the path points. Frequent starting and stopping at the path point position will cause great damage to the linear motor. The impact and vibration on the entire movable plate during starting and stopping are large, which can easily increase the wear of the CNC machine tool. For the planning of machining paths for complex curves and surfaces, NURBS (Non uniform rational B-spline) curves are often used for feed speed planning and interpolation point position calculation to avoid the problem of low machining efficiency and feed fluctuation caused by a large number of small segments approaching the curve.

[0003] In the related technology, the route is split into 1 / 2 and the speed is interpolated separately as acceleration and deceleration sections. In this way, due to the different complexity of the tool path at different positions of the workpiece, the traditional planning scheme splits the path in a fixed ratio, which will lead to inconsistent processing speeds for continuous surfaces during the processing process, easily causing consistency deviations in the cutting route and insufficient interpolation smoothness, which will affect the tool path accuracy in the complex tool path stage. Summary of the invention

[0004] In order to solve the technical problem that the method of splitting the path by fixed ratio in the related art will lead to inconsistent processing speed of continuous surfaces during the processing, which is easy to cause consistency deviation of the cutting route and insufficient interpolation fluency, thereby affecting the tool walking accuracy in the complex tool walking stage, the present invention provides an interpolation method based on a data-driven computer numerical control system, and the technical solution adopted is as follows: The present invention proposes an interpolation method for a computer numerical control system based on data drive, the method comprising: Obtain each path point on the linear feed path, and obtain the starting window under 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 isotropic similarity 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 angle between the front and rear paths; determine the similarity sequence of the isotropic similarities under different step lengths; determine the cutoff coefficient under the current step length according to the change of elements in the similarity sequence and the aspect ratio of the starting window of different step lengths, perform step length cutoff according to the cutoff coefficient, and determine the cutoff window; Starting from the end path point of the cut-off window, a non-repeated traversal is performed in the direction of the starting path point to select a window, which is recorded as the return window; according to the values ​​of the isotropic similarities of the return window and the starting window at the same path point under different step lengths, the cut-off window is divided into different restriction windows, and the speed of the path points within the restriction window is restricted by the cut-off coefficient corresponding to the restriction window; Traverse all path points and re-plan the feed speed according to the speed limits of all path points.

[0005] Furthermore, the method of determining the isotropic similarity 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 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 in the corresponding window as the starting direction straight line, and determine the straight line formed by the next next path point and the last path point in the window as the ending direction straight line; The angle formed by the starting direction straight line and the ending direction straight line is taken as the path angle, the opposite of the path angle is calculated, and normalized to obtain the angle index; The ratio of the total length of the tool path in the window to the number of path points in the window is used as a density analysis index; The isotropic similarity of the last path point in the window is determined according to the angle index and the density analysis index.

[0006] Further, according to the angle index and the density analysis index, the isotropic similarity of the last path point of the window is determined, including: The product of the density analysis index and the angle index is normalized and used as the isotropic similarity of the last path point in the window.

[0007] Further, the determining of the similarity sequence of the isotropic similarities under different step lengths includes: The isotropic similarities of different path points are arranged in order from small to large step values ​​to obtain a similarity sequence.

[0008] Furthermore, the step of determining the cutoff coefficient at the current step size according to the change of elements in the similarity sequence and the aspect ratio of the starting windows of different step sizes includes: Calculate the average of the aspect ratios of the starting window corresponding to the current step size and all previous step sizes to obtain the average aspect ratio; The difference between the average value of the aspect ratio and the aspect ratio of the starting window corresponding to the current step size is used as the first cutoff coefficient; Perform first-order difference processing on the elements in the similarity sequence, take the absolute value to obtain the difference value, and multiply the sum of all the difference values ​​by the first cutoff coefficient as the similarity change index under the current step size; The difference between the similarity change index and the minimum value of the elements in the similarity sequence is calculated as a cutoff coefficient.

[0009] Further, the step length is cut off according to the cut off coefficient to determine the cut off window, including: When the cutoff coefficient is greater than or equal to 1, the window under the corresponding step size is used as the cutoff window.

[0010] Furthermore, according to the values ​​of the isotropic similarities of the return window and the start window at the same path point under different step lengths, the cutoff window is divided into different limit windows, including: Within the cutoff window, the path point position corresponding to any step length is used as the analysis position; According to the numerical comparison of the similarities in all directions between the starting window and the return window corresponding to the analysis position, the limiting coefficient for dividing the cut-off window is determined; According to the value of the limiting coefficient under each step length, the limiting step length is determined, and the cutoff window is divided into different limiting windows according to the limiting step length.

[0011] Furthermore, according to the numerical comparison of the similarities of the starting window and the return window corresponding to the analysis position in each direction, the restriction coefficient for dividing the cutoff window is determined, including: The window from the starting path point to the analysis position is determined as the starting analysis window, and the window from the last path point in the ending window to the analysis position is determined as the return analysis window; The ratio of the isotropic similarity of the return analysis window to the isotropic similarity of the forward analysis window is used as a restriction coefficient.

[0012] Furthermore, the speed of the path points within the restriction window is limited by the cutoff coefficient corresponding to the restriction window, including: Calculate the mean of the cutoff coefficients of all path points within the restriction window as the cutoff mean; Calculate the difference between the unit value 1 and the cutoff mean as the speed limit weight; The product value of the speed limit weight and the maximum speed is used as the tool movement limit speed of the path point in the restriction window.

[0013] Furthermore, all path points are traversed and the feed speed is replanned according to the speed limits of all path points, including: The NURBS smooth interpolation is performed on the tool feed speed limit of each path point in the timing sequence to realize the feed speed planning of the tool path.

[0014] The present invention has the following beneficial effects: In the embodiment of the present invention, by performing a comprehensive analysis of the starting window and the return window on different path points, the total length of the tool path formed by the path points in the starting window, the number of path points, and the angle change of the front and rear paths, the various directional similarities are determined, so as to facilitate the cutoff of the path complexity according to the various directional similarities, and analyze the adjacent path points with relatively consistent path complexity as a whole, and then according to the traversal of the return window in the cutoff window, the refined analysis of the tool complexity in different directions is realized to obtain the restriction window, which integrates the tool analysis of different directional dimensions, thereby avoiding tool analysis based on only one direction. Analysis causes consistency deviation; In summary, the embodiment of the present invention uses the different directional dimensional features of the starting window and the return window to perform a more refined analysis of the tool path, thereby solving the problem that the traditional planning scheme uses a fixed-ratio path splitting scheme and causes the unreasonable splitting scheme, which makes the interpolation point parameter results of the tool walking process insufficient to adjust the machining integrity of the entire surface and the interpolation smoothness. This scheme divides the path with a more consistent tool walking representation into a restriction window, and performs tool walking planning within the same restriction window, thereby ensuring the stability of the interpolation points, improving the interpolation smoothness, reducing the consistency deviation, and thereby improving the tool walking accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 A flow chart of an interpolation method for a computer numerical control system based on data drive provided by one embodiment of the present invention; Figure 2 A schematic diagram of tool acceleration and deceleration changes provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0017] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is a detailed description of the interpolation method based on a data-driven computer numerical control system proposed by the present invention, its specific implementation, structure, features and effects, in conjunction with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0018] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0019] The specific scheme of the interpolation method of a data-driven computer numerical control system provided by the present invention is described in detail below with reference to the accompanying drawings.

[0020] See also Figure 1 , which shows a flow chart of an interpolation method based on a data-driven computer numerical control system provided by an embodiment of the present invention, the method comprising: S101: Acquire each path point on the linear feeding path, and acquire a starting window under 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.

[0021] CNC interpolation is the result of compensating for the fact that the machining path of the workpiece is represented by discrete points in CAD / CAM software, which will cause the spindle to move frequently between path points. Frequent starting and stopping at the target point position will cause great damage to the linear motor. The impact and vibration on the entire movable disk during starting and stopping are relatively large, which can easily aggravate the wear of the CNC machine tool.

[0022] The existing technology uses NURBS (Nonuniform rational B-spline) curves to plan feed speeds and calculate interpolation point positions for complex curve and surface machining paths, so as to avoid the problems of low machining efficiency and feed fluctuations caused by a large number of small segments approaching the curve.

[0023] However, due to the different complexity of the workpiece processing paths, and the inconsistency of the corresponding complexity of different processing paths, for example, a certain section of the processing path requires "toothed" tool movement, while the next section of the processing path is a "straight" tool movement. Therefore, if a uniform speed is used for interpolation, the accuracy of the "toothed" tool movement may be different, thus affecting the quality of the workpiece. Based on this, this solution analyzes the tool path and interpolates the feed speed to achieve a more precise tool planning.

[0024] In an embodiment of the present invention, CNC engineering software (such as Mastercam, Rhinocam, etc.) can be used to construct a processing model of the current product, input the size of the processed blank, and the CNC software generates a tool path based on the part contour lines, and number each path point to complete the acquisition of the path points of the processing model.

[0025] Understandably, see Figure 2 , Figure 2A schematic diagram of tool acceleration and deceleration changes provided by an embodiment of the present invention; analyzing the movement conditions generated by adjacent path points: the "S"-shaped acceleration and deceleration method formed by path planning is shown as follows: In the acceleration section 0-t1, the acceleration a is increased from 0 to a preset positive value with a constant positive jerk j; in the uniform acceleration section t1-t2, the acceleration is accelerated with a constant acceleration a; in the deceleration section t2-t3, the acceleration a is decelerated from a preset positive value to 0 with a constant negative jerk j; in the uniform speed section t3-t4, the vehicle runs at a constant speed v; in the deceleration section t4-t5, the acceleration a is reduced from 0 to a preset negative value (wherein the preset positive value and the preset negative value are opposite numbers) with a constant negative jerk j; in the uniform deceleration section t5-t6, the vehicle decelerates with a constant acceleration a; in the deceleration section t6-t7, the acceleration a is increased from a preset negative value to 0 with a constant positive jerk j.

[0026] It should be noted that the preset positive value in the embodiment of the present invention can be specifically, for example, 0.1 meters per second squared, and the preset negative value can be -0.1 meters per second squared, and there is no limitation on this. The acceleration control is achieved by the corresponding jerk, thereby achieving an "S" curve of the speed.

[0027] It is understandable that moving the tool between two adjacent path points will result in excessively uneven speed, which in turn leads to an unreasonable initial speed setting for the planned stroke of the next path point. For example, the next path point requires a smaller feed speed due to the more complex shape being processed, while the ending speed of the previous path point is greater. The resulting instantaneous deceleration causes speed jitter between path points, resulting in large changes in tool movement, which in turn affects tool movement accuracy. Therefore, it is necessary to plan the speed limits between segments based on the complexity of the feed route.

[0028] In an embodiment of the present invention, firstly, regional planning is performed for different path points. Since the changes in tool path complexity between adjacent path points are inconsistent, specific path point classification can be performed to classify adjacent path points with consistent complexity into one category.

[0029] 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 counting 5 path points backward from the starting path point, and taking the minimum circumscribed rectangle of all path points in between as the starting window under the step length of 5. In this way, the starting window under each step length is obtained, which is convenient for subsequent analysis.

[0030] S102: Determine the isotropic similarity of each path point based on 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 angle between the front and rear paths; determine the similarity sequence of the isotropic similarities under different step lengths; determine the cutoff coefficient under the current step length based on the change of elements in the similarity sequence and the aspect ratio of the starting window of different step lengths, perform step cutoff based on the cutoff coefficient, and determine the cutoff window.

[0031] Among them, the isotropic similarity is an indicator of the tool direction and tool density of the corresponding path point position. The larger the value of the isotropic similarity, the more consistent the direction between the path point lines is, and the longer the tool path length formed by the path points is, indicating that the tool path at the path point is smoother and can leave a higher deceleration margin. Since the total length of the tool path in adjacent path points is inconsistent, and the number of path points and the change in tool angle generated by the two path points are also inconsistent, based on this, the specific calculation of the isotropic similarity can be performed.

[0032] Among them, the number of path points includes the last path point, that is, when the step length is 5, the corresponding number of path points is 5.

[0033] Furthermore, in some embodiments of the present invention, the isotropic similarity of each path point is determined based on 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 angle between the front and rear paths, including: taking each path point as the last path point in 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 next path point in the window and the last path point as the ending direction straight line; taking the angle formed by the starting direction straight line and the ending direction straight line as the path angle, calculating the opposite of the numerical value of the path angle, and normalizing it to obtain an angle index; taking the ratio of the total length of the tool path in the window to the number of path points in the window as a density analysis index; and determining the isotropic similarity of the last path point in the window based on the angle index and the density analysis index.

[0034] That is to say, in the embodiment of the present invention, the isotropic similarity analysis is achieved by analyzing the angle change and the density analysis index. The angle change is mainly the angle change corresponding to the starting path point and the last path point in the window. Therefore, in the embodiment of the present invention, the path angle is determined by determining the starting direction straight line and the ending direction straight line. The smaller the path angle (maximum 180 degrees), the smaller the corresponding angle change between the path start and the path end.

[0035] The embodiment of the present invention directly calculates the opposite of the numerical value of the path angle (this numerical value only represents the numerical feature and does not include the angular feature), and normalizes it as the angle index. That is, the larger the angle index is, the smaller the numerical value of the corresponding path angle is, which further indicates that the angle change between the path start and the path end is smaller, and the path angle change in the corresponding window is smoother.

[0036] Among them, the ratio of the total length of the tool path in the window to the number of path points in the window is used as a density analysis indicator. Usually, the selection of path points in complex areas is more dense, and the specific calculation of path point density is the ratio of the number of path points in the window to the total length of the tool path in the window. The larger the density, the more complex the tool path in the window.

[0037] Therefore, the density analysis index in the embodiment of the present invention is used as the inverse of the path point density (by directly calculating the ratio of the total length of the tool path in the window to the number of path points in the window), so that the larger the value of the density analysis index, the longer the tool path length in the corresponding window and the smaller the number of path points. At this time, there is more room for tool deceleration and the tool movement is smoother.

[0038] Therefore, according to the density analysis index, the smoothing effect of the path in the window can be further characterized. The embodiment of the present invention can combine the angle index and the density analysis index to perform isotropic similarity analysis.

[0039] Furthermore, in some embodiments of the present invention, the isotropic similarity of the last path point in the window is determined based on the angle index and the density analysis index, including: normalizing the product of the density analysis index and the angle index as the isotropic similarity of the last path point in the window.

[0040] Among them, the larger the value of the density analysis index is, the smaller the density is, and the tool has a higher deceleration margin, and the larger the angle index is, the smaller the angle change between the path start and the path end is, and the corresponding path angle change in the window is smoother. It can be seen that the density analysis index and the angle index are both positively correlated with the isotropic similarity. Therefore, the present invention directly calculates the product value of the density analysis index and the angle index, and normalizes it as the isotropic similarity of the last path point in the window.

[0041] After obtaining the isotropic similarity of each path point, the path points and the starting path point can be arranged in order from small to large according to the step value, and a similarity sequence of isotropic similarities under different step lengths can be obtained. In addition, different tool paths can be classified and analyzed according to the similarity sequence. The classification in the embodiment of the present invention is mainly cutoff classification, that is, when a large change is detected, a cutoff process is performed and re-analysis is performed, thereby, path points with close neighbors and similar tool paths can be classified into one category.

[0042] Furthermore, in some embodiments of the present invention, a cutoff coefficient at a current step size is determined based on changes in elements in a similarity sequence and aspect ratios of starting windows of different step sizes, including: calculating the average of the aspect ratios of the starting windows corresponding to the current step size and all previous step sizes to obtain the aspect ratio average; taking the difference between the aspect ratio average and the aspect ratio of the starting window corresponding to the current step size as a first cutoff coefficient; performing first-order difference processing on the elements in the similarity sequence, taking the absolute value to obtain the difference value, and multiplying the sum of all the difference values ​​by the first cutoff coefficient as a similarity change index at the current step size; and calculating the difference between the similarity change index and the minimum value of the element in the similarity sequence as the cutoff coefficient.

[0043] The cutoff coefficient represents the realization of step length cutoff, and the tool path within the corresponding step length range is used as a whole indicator information for cutoff judgment.

[0044] In the embodiment of the present invention, the starting window will produce an angular deflection characteristic as the step length increases, that is, the angle will produce a cumulative deflection effect. If this cumulative deflection is too large, it will also lead to a complicated tool path. Therefore, in the embodiment of the present invention, the deviation amplitude of the path is measured by the aspect ratio of the minimum circumscribed rectangular bounding box (Bounding Box function) of the path points in the current window.

[0045] Therefore, in an embodiment of the present invention, the average of the aspect ratios of the starting window corresponding to the current step length and all previous step lengths is calculated to obtain the average aspect ratio, which characterizes the path deviation amplitude characteristics under all step lengths, and the difference between the average aspect ratio and the aspect ratio of the starting window corresponding to the current step length is calculated as the first cutoff coefficient. The first cutoff coefficient represents the change in window shape, that is, the difference between the window shape of all previous step lengths and the window shape under the current step length. The larger the difference, the greater the window change under the current step length.

[0046] The first-order difference processing of the elements in the similarity sequence can represent the changes in the isotropic similarities. The larger the sum of all differential values, the greater the difference in the isotropic similarities. At this time, a cutoff analysis is more needed. Therefore, in an embodiment of the present invention, the first cutoff coefficient is used as the weight of the sum of all differential values ​​for analysis, and the product of the sum of all differential values ​​and the first cutoff coefficient is directly calculated as the similarity change indicator under the current step size.

[0047] As the step size changes, the similarity change index gradually increases. The similarity change index is compared with the minimum value of the element in the similarity sequence, and the difference between the similarity change index and the minimum value of the element in the similarity sequence is calculated as the cutoff coefficient. The cutoff coefficient represents the difference between the similarity change index and the minimum value of the element in the similarity sequence. When the value of the similarity change index is small, the cutoff coefficient is small. As the value of the similarity change index increases, the cutoff coefficient also gradually increases, indicating that the complexity of the tool path is gradually increasing.

[0048] Further, in some embodiments of the present invention, the step length is cut off 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 under the corresponding step length is used as the cut-off window. That is, when the difference between the similarity change index and the minimum value of the element in the similarity sequence is 1, it means that the cut-off requirement is met, and thus the cut-off window is determined. Of course, in other embodiments of the present invention, other thresholds can also be set to implement cut-off analysis, and there is no limitation on this.

[0049] S103: Starting from the end path point of the cutoff window, a non-repeated traversal is performed in the direction of the starting path point to select a window, which is recorded as the return window; according to the values ​​of the isotropic similarities of the return window and the starting window at the same path point under different step lengths, the cutoff window is divided into different restriction windows, and the speed of the path points within the restriction window is limited by the cutoff coefficient corresponding to the restriction window.

[0050] Judge the path direction variation caused by window extension: During the tool movement process, the speed requirement for the complex forward situation is not fully estimated, which is reflected in the obvious tool movement direction deviation caused by gradual changes. When analyzing this deviation, it is masked by the long smooth path in the window, making it impossible to accurately analyze it, resulting in poor timeliness of response of the workpiece interpolation data points, and the interpolation data points do not reflect the hierarchy of the processing texture (that is, the NURBS curve has a higher local approximation order, resulting in the local processing path being not smooth).

[0051] In an embodiment of the present invention, after the cutoff window is determined, the forward window stepping is stopped, and starting from the last path point (termination path point) of the cutoff window, the window is selected in the direction of the starting path point without repetition traversal to obtain a return window. It should be noted that, if the path interpolation planning analysis is performed only based on the starting window, the corresponding tool movement is still affected by the precision error of the path point arrangement, and the introduction of the return window and the integration analysis combined with the forward and return windows can better characterize the tool movement analysis of each path point position. The return window is used to perform deflection analysis under different step lengths, which not only judges the abnormal output position, but also can show the instability of frequent path changes.

[0052] Furthermore, in some embodiments of the present invention, the cutoff window is divided into different restriction windows according to the values ​​of the isotropic similarities of the return window and the starting window at the same path point under different step lengths, including: within the cutoff window, the path point position corresponding to any step length is used as the analysis position; based on the comparison of the values ​​of the isotropic similarities of the starting window and the return window corresponding to the analysis position, the restriction coefficient for dividing the cutoff window is determined; based on the value of the restriction coefficient under each step length, the restriction step length is determined, and the cutoff window is divided into different restriction windows according to the restriction step length.

[0053] It can be understood that the starting window corresponding to the analysis position is the minimum circumscribed rectangle from the starting path point to the analysis position, and the return window corresponding to the analysis position is the minimum circumscribed rectangle from the ending path point to the analysis position. Since the entire cutoff window indicates that its overall tool change is relatively consistent during analysis, the greater the difference in the similarities between the starting window and the return window corresponding to the analysis position in all directions, it means that a more refined cutoff window tool consistency division can be performed from the analysis position.

[0054] Furthermore, in some embodiments of the present invention, the restriction coefficient for dividing the cut-off window is determined based on the numerical comparison of the isotropic similarities of the starting window and the reverse window corresponding to the analysis position, 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 in the cut-off window to the analysis position as the return analysis window; and taking the ratio of the isotropic similarity of the return analysis window to the isotropic similarity of the starting analysis window as the restriction coefficient.

[0055] The numerical comparison in the embodiment of the present invention is mainly to calculate the ratio, and directly use the ratio of the isotropic similarity of the return analysis window to the isotropic similarity of the start analysis window as the restriction coefficient. The restriction coefficient represents the restriction on the consistency of the tool path.

[0056] Furthermore, in some embodiments of the present invention, the speed of the path points within the restriction window is limited by the cutoff coefficient corresponding to the restriction window, including: calculating the mean of the cutoff coefficients of all path points in the restriction window as the cutoff mean; calculating the difference between the unit value 1 and the cutoff mean as the speed limit weight; and taking the product of the speed limit weight and the maximum speed as the tool movement limit speed of the path points in the restriction window.

[0057] It can be understood that when the value of the cutoff coefficient is greater than or equal to 1, it is divided into a cutoff window. Therefore, the cutoff coefficients in the restricted window are all less than 1, and the cutoff mean is less than 1. The cutoff mean represents the overall tool path complexity of the restricted window, and the speed limit can be based on this. The larger the value of the cutoff mean, the more complex the tool path in the restricted window, so the speed needs to be reduced. Therefore, the difference between the unit value 1 and the cutoff mean 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 tool path limit speed of the path point.

[0058] Thus, the tool speed limit of each path point is determined and marked, so as to facilitate the subsequent interpolation planning according to the tool speed limit of each path point.

[0059] S104: Traverse all path points and re-plan the feed speed according to the speed limits of all path points.

[0060] In an embodiment of the present invention, a built-in NURBS interpolator can be used to perform NURBS smooth interpolation on the tool limit speed of each path point in the timing to realize the feed speed planning of the tool path. That is to say, the intermediate value interpolation is performed on the discrete tool limit speeds of all path points to facilitate the planning of the speed of the entire tool path, generate the NURBS tool path and simulate and verify it.

[0061] In the embodiment of the present invention, by performing a comprehensive analysis of the starting window and the return window on different path points, the total length of the tool path formed by the path points in the starting window, the number of path points, and the angle change of the front and rear paths, the various directional similarities are determined, so as to facilitate the cutoff of the path complexity according to the various directional similarities, and analyze the adjacent path points with relatively consistent path complexity as a whole, and then according to the traversal of the return window in the cutoff window, the refined analysis of the tool complexity in different directions is realized to obtain the restriction window, which integrates the tool analysis of different directional dimensions, thereby avoiding tool analysis based on only one direction. Analysis causes consistency deviation; In summary, the embodiment of the present invention uses the different directional dimensional features of the starting window and the return window to perform a more refined analysis of the tool path, thereby solving the problem that the traditional planning scheme uses a fixed-ratio path splitting scheme and causes the unreasonable splitting scheme, which makes the interpolation point parameter results of the tool walking process insufficient to adjust the machining integrity of the entire surface and the interpolation smoothness. This scheme divides the path with a more consistent tool walking representation into a restriction window, and performs tool walking planning within the same restriction window, thereby ensuring the stability of the interpolation points, improving the interpolation smoothness, reducing the consistency deviation, and thereby improving the tool walking accuracy.

[0062] It should be noted that the sequence of the above embodiments of the present invention is only for description and does not represent the advantages and disadvantages of the embodiments. The processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0063] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

Claims

1. An interpolation method for a data-driven computer numerical control system, characterized in that: The method comprises: Obtain each path point on the linear feed path, and obtain the starting window under 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 isotropic similarity 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 angle between the front and rear paths; determine the similarity sequence of the isotropic similarities under different step lengths; determine the cutoff coefficient under the current step length according to the change of elements in the similarity sequence and the aspect ratio of the starting window of different step lengths, perform step length cutoff according to the cutoff coefficient, and determine the cutoff window; Starting from the end path point of the cut-off window, a non-repeated traversal is performed in the direction of the starting path point to select a window, which is recorded as the return window; according to the values ​​of the isotropic similarities of the return window and the starting window at the same path point under different step lengths, the cut-off window is divided into different restriction windows, and the speed of the path points within the restriction window is restricted by the cut-off coefficient corresponding to the restriction window; Traverse all path points and re-plan the feed speed according to the speed limits of all path points.

2. The interpolation method based on a data-driven computer numerical control system according to claim 1, characterized in that: The method of determining the isotropic similarity 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 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 in the corresponding window as the starting direction straight line, and determine the straight line formed by the next next path point and the last path point in the window as the ending direction straight line; The angle formed by the starting direction straight line and the ending direction straight line is taken as the path angle, the opposite of the path angle is calculated, and normalized to obtain the angle index; The ratio of the total length of the tool path in the window to the number of path points in the window is used as a density analysis index; The isotropic similarity of the last path point in the window is determined according to the angle index and the density analysis index.

3. The interpolation method based on a data-driven computer numerical control system as claimed in claim 2, characterized in that: Determining the isotropic similarity of the last path point of the window according to the angle index and the density analysis index includes: The product of the density analysis index and the angle index is normalized and used as the isotropic similarity of the last path point in the window.

4. The interpolation method based on a data-driven computer numerical control system according to claim 1, characterized in that: The similarity sequence of determining the isotropic similarities under different step lengths includes: The isotropic similarities of different path points are arranged in order from small to large step values ​​to obtain a similarity sequence.

5. The interpolation method based on a data-driven computer numerical control system according to claim 1, characterized in that: The method of determining the cutoff coefficient under the current step size according to the change of elements in the similarity sequence and the aspect ratio of the starting windows of different step sizes includes: Calculate the average of the aspect ratios of the starting window corresponding to the current step size and all previous step sizes to obtain the average aspect ratio; The difference between the average value of the aspect ratio and the aspect ratio of the starting window corresponding to the current step size is used as the first cutoff coefficient; Perform first-order difference processing on the elements in the similarity sequence, take the absolute value to obtain the difference value, and multiply the sum of all the difference values ​​by the first cutoff coefficient as the similarity change index under the current step size; The difference between the similarity change index and the minimum value of the elements in the similarity sequence is calculated as a cutoff coefficient.

6. The interpolation method based on a data-driven computer numerical control system according to claim 1, characterized in that: The step length is cut off according to the cut-off coefficient to determine the cut-off window, including: When the cutoff coefficient is greater than or equal to 1, the window under the corresponding step size is used as the cutoff window.

7. The interpolation method based on a data-driven computer numerical control system according to claim 1, characterized in that: According to the values ​​of the isotropic similarities of the return window and the start window at the same path point under different step lengths, the cutoff window is divided into different limit windows, including: Within the cutoff window, the path point position corresponding to any step length is used as the analysis position; According to the numerical comparison of the similarities in all directions between the starting window and the return window corresponding to the analysis position, the limiting coefficient for dividing the cut-off window is determined; According to the value of the limiting coefficient under each step length, the limiting step length is determined, and the cutoff window is divided into different limiting windows according to the limiting step length.

8. The interpolation method based on a data-driven computer numerical control system according to claim 7, characterized in that: According to the numerical comparison of the similarities of the starting window and the return window corresponding to the analysis position in all directions, the limiting coefficient for dividing the cutoff window is determined, including: The window from the starting path point to the analysis position is determined as the starting analysis window, and the window from the last path point in the ending window to the analysis position is determined as the return analysis window; The ratio of the isotropic similarity of the return analysis window to the isotropic similarity of the forward analysis window is used as a restriction coefficient.

9. The interpolation method based on a data-driven computer numerical control system according to claim 1, characterized in that: The speed of the path points within the restriction window is limited by the cutoff coefficient corresponding to the restriction window, including: Calculate the mean of the cutoff coefficients of all path points within the restriction window as the cutoff mean; Calculate the difference between the unit value 1 and the cutoff mean as the speed limit weight; The product value of the speed limit weight and the maximum speed is used as the tool movement limit speed of the path point in the restriction window.

10. The interpolation method based on a data-driven computer numerical control system according to claim 9, characterized in that: Traverse all path points and re-plan the feed speed according to the speed limits of all path points, including: The NURBS smooth interpolation is performed on the tool feed speed limit of each path point in the timing sequence to realize the feed speed planning of the tool path.

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