Corner smooth control method for compensating arc offset and numerical control machine tool

Abstract

The invention provides a corner smooth control method for compensating arc offset and a numerical control machine tool, and the method comprises the steps: testing the corner arc offset of each motion shaft seat, and calculating to obtain a corner arc correlation coefficient of each motion shaft; and receiving an interpolation instruction of two adjacent line segments in the path cache region, determining a plane where the two adjacent line segments are located, obtaining a corner arc correlation coefficient of the corresponding motion axis, and performing compensation offset calculation on the corner arc of the two adjacent line segments through the obtained corner arc correlation coefficient. The offset of the numerical control machine tool at the corner arc is compensated, arc corner turning can be conducted at the maximum arc speed allowed by a numerical control system, and therefore the machining efficiency of the machine tool at the corner point is improved. The phenomenon of undercut or overcut and the like occurring when a machine tool machines corner points is eliminated, an additional smooth curve interpolation function does not need to be developed in a numerical control system, processing can be directly completed in a real-time kernel of the numerical control system, and the requirement for hardware of the numerical control system is low.

Description

Technical Field

[0001] The invention relates to the technical field of numerical control machining, and in particular to a corner smoothing control method for compensating for circular arc offset and a numerical control machine tool. Background Art

[0002] High-speed and high-precision machining has always been a problem that needs to be solved urgently by modern CNC systems. For the machining of parts with complex profiles, CNC systems usually use computer CAM software to decompose the profile of the parts into a series of straight line segments and arc segments, and then use various interpolation functions in the CNC system to complete the interpolation operation of each path segment, and finally complete the processing of the complex profile. The use of this NC program formed by a large number of straight line segments and arc segments has too many corner points and frequent acceleration and deceleration, which can easily cause impact, resulting in overcutting, undercutting and other problems, seriously affecting the machining accuracy and efficiency of parts with complex profiles. Therefore, path optimization and speed optimization for small line segment NC programs to achieve smooth transition of the machining path is of great significance to improving machining quality and improving the machining efficiency and motion stability of machine tools. Summary of the invention

[0003] In order to solve the technical problem of discontinuous and non-smooth speed planning of a numerical control system at a connection point of continuous line segments in the above-mentioned prior art, the present invention proposes a corner smoothing control method for compensating for arc offset and a numerical control machine tool.

[0004] The technical solution adopted by the present invention is:

[0005] The present invention proposes a method for smoothing corner control for compensating for circular arc offset, comprising the steps of:

[0006] Test the rotation angle arc offset of each motion axis seat and calculate the rotation angle arc correlation coefficient of each motion axis;

[0007] An interpolation instruction of two adjacent line segments in a path buffer is received, and a plane where the two adjacent line segments are located is determined to obtain a corresponding rotation angle arc correlation coefficient of the motion axis, and a compensation offset calculation is performed on the rotation angle arc of the two adjacent line segments using the obtained rotation angle arc correlation coefficient.

[0008] The present invention also comprises the steps of:

[0009] The corner arc feature information obtained by the offset compensation calculation modifies the end point information of the previous line segment and the starting point information of the next line segment between two adjacent line segments, and a new arc interpolation instruction corresponding to the corner arc feature information is added, and the arc interpolation instruction is inserted between the instructions of the two adjacent line segments.

[0010] Specifically, the test of the rotation angle arc offset of each moving shaft seat and the calculation of the rotation angle arc correlation coefficient of each moving shaft specifically include:

[0011] NC code is written to make the machine tool perform forward feed motion along multiple motion axes and then make a right-angle forward motion, and multiple sets of different speeds are used to perform corner arc tests for each motion axis to obtain multiple corner arc trajectories corresponding to each motion axis, and the maximum arc offset and centripetal acceleration generated by each set of speeds are calculated, and then the maximum arc offset and centripetal acceleration generated are fitted and calculated to obtain the coefficient terms and constant terms corresponding to the multiple motion axes.

[0012] The multiple motion axes include an X-axis, a Y-axis and a Z-axis respectively;

[0013] Among them, the coefficient term calculated by X-axis fitting is kx, and the constant term is acx;

[0014] The coefficient term calculated on the Y axis is ky, and the constant term is acy;

[0015] The coefficient term calculated for the Z axis is kz and the constant term is acz.

[0016] Furthermore, the compensation offset calculation of the corner arc is performed by using the obtained corner arc correlation coefficient, specifically including:

[0017] Substitute the obtained corner arc correlation coefficient into the compensation value formula to calculate the compensation value Δc;

[0018] Substitute the calculated compensation value Δc into the transition distance Lt formula to calculate the transition distance Lt;

[0019] Substitute the transition distance Lt into the calculation formula of the arc radius r after compensation to calculate the arc radius r after compensation;

[0020] Substitute the transition distance Lt into the starting and ending corner point formula to calculate the starting corner point Q 0 , and the terminal corner point Q 2 .

[0021] Furthermore, the compensation value formula is:

[0022] Δc=kv+ac0;

[0023] Among them, k is the average value of multiple motion axis coefficient items corresponding to the plane where the two adjacent line segments are located, ac0 is the average value of multiple motion axis constant items corresponding to the plane where the two adjacent line segments are located; v takes the minimum value of the NC programming speed of the previous line segment instruction and the arc motion speed in the two adjacent line segments. The formula for the arc motion speed is: a 系 is the value of the centripetal acceleration term of the channel parameter in the CNC system, and r is the radius of the transition arc in the CNC system before compensation.

[0024] Furthermore, the transition distance Lt formula is:

[0025]

[0026] Among them, e is the angle smoothing error, and α is the vector angle between two adjacent straight line segments.

[0027] Furthermore, the calculation formula of the arc radius r after compensation is:

[0028]

[0029] Among them, α is the vector angle between two adjacent straight line segments.

[0030] Furthermore, the formulas for the starting and ending corner points are:

[0031]

[0032] Among them, P i-1、 P i are respectively the starting point coordinates and the ending point coordinates of the previous straight line segment among the two adjacent line segments;

[0033] S i is the length of the previous straight line segment;

[0034] is the unit vector from the starting point to the end point of the previous straight line segment, The unit vector pointing from the start point of the next straight line segment to the end point.

[0035] The present invention further proposes a numerically controlled machine tool, characterized in that the method for smoothing the control of the angle for compensating for arc offset as described in any one of claims 1 to 9 is used to perform arc compensation calculation and command interpolation on two adjacent line segments.

[0036] Compared with the prior art, the present invention has the following advantages:

[0037] 1. The corner smoothing control method for compensating arc offset proposed in the present invention can compensate for the offset of the CNC machine tool at the corner arc, and can perform arc corner rotation at the maximum arc speed allowed by the CNC system, thereby improving the processing efficiency of the machine tool at the corner point.

[0038] 2. The present invention can eliminate the phenomenon of under-cutting or over-cutting when the machine tool processes corner points, and does not need to develop additional smooth curve interpolation functions in the numerical control system. The processing can be completed directly in the real-time kernel of the numerical control system, and the hardware requirements of the numerical control system are low. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be 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 labor.

[0040] Figure 1 This is a diagram of the corner arc deviation phenomenon during machine tool processing in the prior art;

[0041] Figure 2 is a flow chart of a corner arc offset test in an embodiment of the present invention;

[0042] Figure 3 is a test path diagram of an X-axis rotation angle arc offset in an embodiment of the present invention;

[0043] Figure 4 is a diagram of the X-axis rotation angle arc offset trajectory in an embodiment of the present invention;

[0044] Figure 5 Schematic diagram of a smooth arc corner according to an embodiment of the present invention;

[0045] Figure 6 is a flow chart of compensating for corner arc offset in an embodiment of the present invention;

[0046] Figure 7 It is a flow chart in an embodiment of the present invention. DETAILED DESCRIPTION

[0047] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0048] The principle and structure of the present invention are described in detail below with reference to the accompanying drawings and embodiments.

[0049] In the prior art, the patent publication number CN104932424A discloses a method for smoothing the corners of tool paths for CNC numerical control equipment, which is implemented by segmenting the line segments on both sides according to the characteristic values ​​on the corner path, adjusting the endpoints to change a single corner point into multiple corner points or increasing the angle to achieve corner smoothing. However, this method only achieves corner smoothing under geometric shapes, and does not consider the movement speed; changing a single corner point into multiple corner points or increasing the angle cannot well retain the corner information; and changing a single corner point into multiple corner points will increase the number of acceleration and deceleration, affecting the processing efficiency.

[0050] Patent publication number CN111061213A discloses a processing method based on the Bezier curve corner smooth transition algorithm, which is implemented by first using CAD / CAM software to obtain discrete points of small line segment trajectories, and then sequentially reading three data points and substituting them into the model to construct a transition curve according to the preset approximate error constraints and maximum curvature limits to complete the smooth transition of the corner. This method requires additional development of a program to smooth the discrete points of the small line segments, and the model solution is complex, has high hardware requirements, and requires more computing resources.

[0051] In this regard, Figure 7 As shown, the present invention proposes a method for smoothing corner control for compensating arc offset, comprising the steps of:

[0052] Test the corner arc offset of each moving axis seat, and calculate and obtain the corner arc correlation coefficient of each moving axis based on the test results; in this step, the offset of the arc path under different corner conditions can be tested for the X, Y, Z and other rotating axes that may be involved in the interpolation of the machine tool, so as to establish the correlation between the corner arc offset and the corresponding moving axis characteristics. When the machine tool moves to the turning point of the path, the deformation amount and centripetal acceleration requirements of the corresponding corner arc will cause a certain error between the actual path and the theoretical interpolation trajectory. The error can be quantitatively described and corrected through the pre-measured corner arc correlation coefficient, so that precise adjustments can be made in subsequent compensation calculations;

[0053] The interpolation instructions of two adjacent line segments in the path buffer are received, and a suitable combination of motion axes is selected according to the motion plane where the two adjacent line segments are located, and the corner arcs of the two adjacent line segments are compensated for by calculating the offset through the obtained corner arc correlation coefficients.

[0054] When the CNC system is planning the processing path, it needs to identify the corner position according to the switching between the current processing path and the next segment path. Then, using the aforementioned measured corner arc correlation coefficient, the predetermined corner arc compensation amount is allocated to each related motion axis to reduce the impact and vibration at the curve transition, making the connection between adjacent path segments smoother, thereby effectively reducing overcutting and undercutting, and improving the fit of the actual processing curve to the original design contour.

[0055] Through the above method, not only can the relationship between the corner arc offset and the centripetal acceleration be quantified and refined, but also different compensation coefficients can be assigned to different motion axes, thereby achieving accurate compensation and flexible control of the corner arc segment. By independently testing and analyzing the offset influence coefficients of each motion axis of the machine tool, the actual compensation amount of the corner arc can be calculated quickly and accurately, making the transition of the processing path more natural and smooth. This method can significantly reduce the dynamic impact during processing, reduce the path deviation, vibration and unstable factors that occur during the processing process, thereby ensuring higher processing accuracy and processing efficiency, and improving the overall performance and stability of the machine tool in high-speed and high-precision processing.

[0056] In a specific embodiment, the method further comprises the steps of:

[0057] The connection point between two adjacent line segments is adjusted by using the corner arc feature information obtained by compensation offset calculation; specifically, according to the corner arc radius and offset determined after compensation, the end point information of the previous line segment is accurately adjusted to make it exactly match the starting point of the arc segment; and the starting point information of the next line segment is correspondingly corrected so that the line segment can smoothly transition to the end point of the arc segment. On this basis, an instruction for generating arc interpolation is inserted between the instructions of the two adjacent line segments. The generated arc interpolation trajectory segment will provide a smooth and continuous transition for the conversion of the two linear interpolation instructions, and realize a natural transition from the end position of the previous line segment to the starting position of the next line segment. The existence of the arc interpolation segment and the addition of the arc segment can ease the acceleration and deceleration transformation process of the motion axis and realize a flexible and smooth transition at the path corner. This strategy helps to reduce the load impact of machine tool mechanical parts, reduce machining errors, extend the service life of tools and machine tool parts in high-speed and high-precision machining, and ultimately improve the overall machining efficiency and product quality.

[0058] In a specific embodiment, the rotation angle arc offset test of each motion axis seat is performed to calculate the rotation angle arc correlation coefficient of each motion axis, including the following refinement process:

[0059] Write a corresponding NC test program on the actual machine tool, which performs interpolation motion of a specific path in different or the same machining planes (such as XY plane, YZ plane, XZ plane and other possible rotation axis planes);

[0060] The basic characteristics of the test path are: the machine tool first performs a linear positive feed along a certain motion axis at a set speed. When the motion reaches the predetermined position, it immediately performs a positive feed at a right angle to achieve the corner connection test between the two line segments. Multiple groups of different feed speeds are tested repeatedly under the same motion axis, including tests under low-speed feed, medium-speed feed, and high-speed feed conditions. In this process, the actual arc trajectory presented after each corner interpolation is completed is recorded by the CNC system.

[0061] After obtaining the trajectory data of the above-mentioned multiple corner arcs, the maximum offset of each arc trajectory needs to be measured. The offset is defined as the maximum deviation value generated by the actual processing trajectory compared with the ideal corner position. The centripetal acceleration corresponding to each test trajectory also needs to be accurately calculated by analyzing multiple factors such as machine tool speed, trajectory curvature, and interpolation strategy. After sorting these data, a set of associated data samples including "speed-arc offset-centripetal acceleration" can be obtained. Using these sample data, a mathematical fitting method (such as multivariate linear regression, nonlinear fitting or other suitable parameter identification methods) is used to establish an associated model between the arc offset and the centripetal acceleration under different speed conditions. The coefficient terms and constant terms generated by the model are used to quantify the relationship between the corner arc offset and the machine tool motion characteristics. In the fitting process, different motion axis test data can be fitted separately to obtain specific coefficient terms and constant term parameter groups corresponding to the plane, thereby providing an accurate reference basis for the subsequent corner arc compensation calculation.

[0062] In the attached Figure 1 In the process, when the machine tool passes through the corner at different speeds, the actual motion trajectory of the corner arc will shift toward the center of the circle as the arc speed increases, causing the machine tool to overcut the workpiece and affecting the processing accuracy. In view of the arc offset phenomenon, the arc offset and the centripetal acceleration generated by the arc motion are analyzed, which satisfies a quasi-linear proportional relationship. Therefore, the corner arc offset test is performed on different motion axes to obtain the axis corner arc offset correlation coefficient. The basic test implementation process is shown in the attached figure. Figure 2 As shown, the specific process is as follows:

[0063] Taking the X-axis as an example, the specific test process and calculation steps can be summarized as follows:

[0064] Test path setting and data collection:

[0065] (1) Write a test NC program in the machine tool control system to make the machine tool first feed a certain distance (such as 5 mm) along the positive direction of the X-axis in the XY plane, and then turn to the positive direction of the Y-axis at a right angle (also 5 mm), forming an L-shaped path corner, as shown in the attached figure. Figure 3 shown.

[0066] (2) Under the premise of satisfying the centripetal acceleration parameter limit of the machine tool, three different feed speeds (such as v1, v2, and v3) are selected to test the above path. The actual machining trajectory of the machine tool is recorded in each test, and the focus is on obtaining the arc offset trajectory at the corner (such as the attached Figure 4 shown).

[0067] (3) Through precise measurement and data acquisition, the maximum arc offset d1, d2, d3 and the corresponding centripetal acceleration a1, a2, a3 at each speed are obtained. Here:

[0068] d1, d2, and d3 correspond to the maximum arc offsets produced at the corner position at feed speeds v1, v2, and v3, respectively.

[0069] a1, a2, and a3 correspond to the centripetal acceleration values ​​under v1, v2, and v3, respectively.

[0070] Data fitting calculation steps:

[0071] The three sets of data pairs ([a1, d1], [a2, d2], [a3, d3]) obtained are fitted and calculated once to determine the corner arc offset coefficient term k and the non-offset initial centripetal acceleration constant term ac.

[0072] (1) Calculate the intermediate variables k1, k2, k3:

[0073]

[0074] (2) Calculate k:

[0075]

[0076] (3) Calculate ac1, ac2, ac3:

[0077] ac 1 =d 1 -k·a 1 , ac 2 =d 2 -k·a 2 , ac 3 =d 3 -k·a 3

[0078] (4) Calculate ac:

[0079]

[0080] Finally, the X-axis rotation angle arc offset coefficient is obtained as kx=k, and the non-offset initial centripetal acceleration term is obtained as acx=ac.

[0081] Y-axis and Z-axis test examples:

[0082] The method of testing other axes is similar, the difference lies in the selection of test path and the change of plane coordinates.

[0083] When testing the Y axis, the path can also be set in the XY plane. For example, first move 5mm in the positive direction of the Y axis, and then turn 5mm in the positive direction of the x axis at a right angle. In this process, three groups of different speed tests are also selected to obtain the corresponding dy1, dy2, dy3 and ay1, ay2, ay3, and then calculate according to the same formula and steps as above to obtain the Y axis corner arc offset coefficient ky and the non-offset initial centripetal acceleration term acy.

[0084] When testing the Z axis, the path can be set in the XZ plane. For example, first move 5mm in the positive direction of the Z axis, and then turn 5mm in the positive direction of the X axis at a right angle in the XZ plane. Similarly, record dz1, dz2, dz3 and az1, az2, az3, and through the same calculation process, obtain the Z axis's angular arc offset coefficient kz and the non-offset initial centripetal acceleration term acz.

[0085] Attached Figure 5 It is a smooth arc transition model of the corner between two line segments used in the present invention;

[0086] Where e is the angle smoothing error,

[0087] P i-1 P i is the previous straight line segment, P i P i+1 is the next straight line segment,

[0088] S i is the length of the previous straight line segment, S i+1 is the length of the next straight line segment,

[0089] is the unit vector from the starting point to the end point of the previous straight line segment, is the unit vector from the start point of the next straight line segment to the end point,

[0090] α is the angle between the two vectors,

[0091] r is the radius of the transition arc;

[0092] Q 0 , Q 2 The starting and ending corner points respectively.

[0093] In a specific embodiment, the process of calculating the compensation offset of the corner arc by obtaining the corner arc correlation coefficient can be divided into the following specific steps:

[0094] Calculate the compensation value Δc:

[0095] In the previous tests and data fitting, the relevant coefficient k of the corner arc offset (and the ac corresponding to the initial centripetal acceleration without offset) has been obtained. Substitute these coefficients and the operating parameters during actual processing (such as the current feed speed, the corresponding centripetal acceleration requirements, etc.) into the pre-established compensation value calculation formula to obtain the compensation value Δc under the corner arc.

[0096] The compensation value Δc is usually defined as the parameter correction required to eliminate or reduce the difference between the actual machining trajectory and the ideal interpolation path at the corner. The accurate solution of Δc can provide a basis for the subsequent adjustment of the transition distance and arc radius.

[0097] Calculate the transition distance Lt:

[0098] Substitute the calculated compensation value Δc into the calculation formula of the transition distance Lt to obtain the length of the corner segment in the arc transition area, that is, Lt.

[0099] In the ideal non-compensated case, the transition at the corner of the line segment is a direct transition from a straight line to a straight line segment in the next direction. If arc compensation is not performed, there will be a large acceleration and deceleration shock and trajectory deviation at the corner transition point. By adjusting Lt using Δc, an arc segment of a reasonable length can be introduced in the transition area, making the acceleration change of the moving axis in the transition interval more stable, thereby reducing the offset and vibration of the tool and achieving a smoother corner motion transition.

[0100] Calculate the arc radius r after compensation:

[0101] After obtaining the transition distance Lt, substitute it into the calculation formula of the arc radius r after compensation to determine the curvature characteristics of the final arc segment.

[0102] The size of r directly determines the radius of curvature of the arc segment and the smoothness of the tool's turning at the corner. A larger r can make the path smoother at the corner, but if r is too large, it will cause too much path deviation; if r is too small, although a relatively compact corner profile is maintained, it may cause machining vibration and path error, leading to overcutting. By comprehensively considering Δc and Lt, the determination of r can achieve a reasonable balance between smoothness and accuracy.

[0103] Calculate the starting corner point Q0 and the ending corner point Q2;

[0104] After completing the calculation of r and Lt, Lt can be substituted into the calculation formula of the starting and ending corner points to locate the starting point Q0 and the end point Q2 of the corner arc segment in the path.

[0105] Q 0It is the starting point of the corner arc segment, located at the end of the previous linear interpolation path, but needs to be appropriately offset according to the compensation result; Q 2 It is the end point of the arc segment, which is located before the start of the next straight path. 0 and Q 2 The CNC system can generate Q 0 As the starting point, Q 2 A smooth transition arc is formed at the end point, thereby achieving a natural transition from the previous path to the next path.

[0106] Through the above calculation steps, the corner arc correlation coefficient and the compensation value formula are combined to effectively control the path shape and transition characteristics at the corner. 0 , Q 2 After solving and parameterizing adjustments, the final machining path can not only maintain high-precision fit to the original contour, but also significantly reduce the impact and vibration at the corners under high-speed and high-acceleration conditions, effectively improving the machining quality and efficiency of complex-profile parts.

[0107] In specific facts, the calculation formula of the compensation value Δc is as follows:

[0108] Δc=kv+ac0,

[0109] in:

[0110] k is the mean value of multiple motion axis coefficient terms corresponding to the plane where the two adjacent line segments are located;

[0111] ac0 is the average value of multiple motion axis constant terms corresponding to the plane where the two adjacent line segments are located; that is, it is obtained by averaging the constant terms ac corresponding to each motion axis obtained by previous fitting.

[0112] v is the reference speed used in the transition process between two adjacent line segments, which is defined as the minimum value between the NC programming speed of the previous line segment (usually the feed speed during line segment interpolation) and the arc motion speed. The arc motion speed is obtained by the following formula:

[0113] a 系 is the centripetal acceleration parameter value set for the machining channel in the CNC system. This parameter is used to limit the upper limit of the centripetal acceleration that the machine tool can withstand during the transition process to ensure the stability and safety of the machining process; r is the transition arc radius value set in the CNC system before compensation. By calculating, we can get the reasonable upper limit of the arc tangent speed that can be achieved by the corner transition arc segment under the current centripetal acceleration limit. Finally, compare the upper limit speed of the arc with the linear speed set by the previous line segment interpolation instruction, and take the smaller value of the two as v for calculating the compensation value Δc.

[0114] Through the above formula and parameter selection, accurate compensation and control of the arc segment at the corner transition can be achieved, making the shape and speed distribution of the transition section more reasonable, effectively reducing the path error and acceleration and deceleration impact at the corner, thereby improving the machining surface quality and machining efficiency.

[0115] The formula for transition distance Lt is:

[0116]

[0117] α is the vector angle between two adjacent straight line segments, that is, the angle formed when the CNC path turns from the previous line segment to the next line segment. Through geometric analysis, this angle can be defined as the angle between the vector directions of two consecutive path segments.

[0118] e is the corner smoothing error, which refers to the allowable error parameter between the ideal arc transition path and the actual processing trajectory, and is used to constrain the smoothness and accuracy of the transition section.

[0119] Δc is the compensation value calculated in the previous step. By correcting it in the transition section, the arc angle is made to fit the theoretical trajectory more closely, thus reducing the problems of overcutting and undercutting.

[0120] The trigonometric function values ​​based on the half angle of the turning angle are used to relate the geometric characteristics of the straight line turning to the transition distance through these trigonometric parameters;

[0121] Lt is determined by the geometric characteristics of the corner, the allowable smoothing error and the actual compensation value. When α is large, a longer transition distance is required at the corner to achieve a smooth transition; when e-Δc is small, it means that the required transition distance can be shortened after appropriate compensation, while still maintaining high precision and high quality corner transition effect.

[0122] The Lt value calculated by this formula will be used in the subsequent steps, that is, to determine the optimized arc radius and the starting and ending points of the corner arc segment based on the compensated transition distance, so as to achieve smooth transition and high-quality processing of the entire processing path under high-speed and high-precision conditions.

[0123] Specifically, the calculation formula of the arc radius r after compensation is:

[0124]

[0125] in:

[0126] α is the vector angle between two adjacent straight line segments, which has the same definition as the turning angle in the calculation of the transition distance Lt mentioned above.

[0127] By combining the transition distance Lt with the cosine factor and its distribution characteristics, the arc radius r can be accurately linked to the geometric relationship of the corner.

[0128] When the turning angle is large, The value will change accordingly, thus affecting the calculation result of the final arc radius. A larger radius r helps provide a smoother transition at larger corners; when the corner is small, the radius adjustment is relatively more flexible.

[0129] The compensated arc radius r calculated by this formula, combined with the correction of the aforementioned compensation value Δc and transition distance Lt, can make the corner transition arc segment smoother and more precise in actual processing, effectively reduce overcutting, undercutting and vibration problems, and further improve processing quality and efficiency.

[0130] The calculation formula for the starting and ending corner points is:

[0131]

[0132] P i-1 is the starting point coordinate of the previous straight line segment, P i is the coordinate of the end point of the previous straight line segment;

[0133] S i is the length of the previous straight line segment;

[0134] is the unit vector from the starting point of the previous straight line segment to the end point, that is, from P i-1 Point to P i The direction vector is obtained after normalization;

[0135] is the unit vector from the start point of the next straight line segment to the end point, that is, from P i The direction vector pointing to the next end point (the end point of the next line segment) is obtained after normalization;

[0136] Lt is the aforementioned compensated and corrected transition distance (determined by the corner smoothing error and the compensation value).

[0137] By calculating the Q 0 and Q 2 Introduce interpolation instructions to insert a corresponding arc transition segment at the connection between two adjacent straight line segments. 0 and Q 2 The starting and ending corner points are determined through the aforementioned compensation and optimization process to make the transition of the corner section smoother, reduce the impact and vibration of the tool at the corner, and thus improve the overall machining accuracy and efficiency.

[0138] The present invention also proposes a CNC machine tool, which uses the above-mentioned corner smoothing control method for compensating arc offset to perform arc compensation calculation and command interpolation on two adjacent line segments, and connects the two adjacent line segments by arc smoothing to solve the problem of speed discontinuity at the corner point, and can ensure processing accuracy and improve efficiency.

[0139] It should be noted that the terms used above are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0140] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

Claims

1. A method for smoothing corner control for compensating arc deviation, characterized in that: Includes steps: Test the rotation angle arc offset of each motion axis seat and calculate the rotation angle arc correlation coefficient of each motion axis; An interpolation instruction of two adjacent line segments in a path buffer is received, and a plane where the two adjacent line segments are located is determined to obtain a corresponding rotation angle arc correlation coefficient of the motion axis, and a compensation offset calculation is performed on the rotation angle arc of the two adjacent line segments using the obtained rotation angle arc correlation coefficient.

2. The method for smoothing the corner of the arc offset compensation according to claim 1, characterized in that: Also includes the steps: The corner arc feature information obtained by the offset compensation calculation modifies the end point information of the previous line segment and the starting point information of the next line segment between two adjacent line segments, and a new arc interpolation instruction corresponding to the corner arc feature information is added, and the arc interpolation instruction is inserted between the instructions of the two adjacent line segments.

3. The method for smoothing the corner of the arc offset compensation according to claim 1, characterized in that: The test of the rotation angle arc offset of each moving axis seat and the calculation of the rotation angle arc correlation coefficient of each moving axis specifically include: NC code is written to make the machine tool perform forward feed motion along multiple motion axes and then make a right-angle forward motion, and multiple sets of different speeds are used to perform corner arc tests for each motion axis to obtain multiple corner arc trajectories corresponding to each motion axis, and the maximum arc offset and centripetal acceleration generated by each set of speeds are calculated, and then the maximum arc offset and centripetal acceleration generated are fitted and calculated to obtain the coefficient terms and constant terms corresponding to the multiple motion axes.

4. The method for smoothing the corner of the arc offset compensation according to claim 3, characterized in that: The multiple motion axes include an X-axis, a Y-axis and a Z-axis respectively; Among them, the coefficient term calculated on the X-axis is kx, and the constant term is acx; The coefficient term calculated on the Y axis is ky, and the constant term is acy; The coefficient term calculated for the Z axis is kz and the constant term is acz.

5. The method for smoothing the corner of the arc offset compensation as claimed in claim 3, characterized in that: The compensation offset calculation of the corner arc by the obtained corner arc correlation coefficient specifically includes: Substitute the obtained corner arc correlation coefficient into the compensation value formula to calculate the compensation value Δc; Substitute the calculated compensation value Δc into the transition distance Lt formula to calculate the transition distance Lt; Substitute the transition distance Lt into the calculation formula of the arc radius r after compensation to calculate the arc radius r after compensation; Substitute the transition distance Lt into the starting and ending corner point formula to calculate the starting corner point Q0 and the ending corner point Q2.

6. The method for smoothing the corner of the arc offset compensation according to claim 5, characterized in that: The compensation value formula is: △c=kv+ac0; Among them, k is the average value of multiple motion axis coefficient items corresponding to the plane where the two adjacent line segments are located, ac0 is the average value of multiple motion axis constant items corresponding to the plane where the two adjacent line segments are located; v takes the minimum value of the NC programming speed of the previous line segment instruction and the arc motion speed in the two adjacent line segments. The formula for the arc motion speed is: a 系 is the value of the centripetal acceleration term of the channel parameter in the CNC system, and r is the radius of the transition arc in the CNC system before compensation.

7. The method for smoothing the corner of the arc offset compensation according to claim 5, characterized in that: The transition distance Lt formula is: Among them, e is the angle smoothing error, and α is the vector angle between two adjacent straight line segments.

8. The method for smoothing the corner of the arc offset compensation as claimed in claim 5, characterized in that: The calculation formula of the arc radius r after compensation is: Among them, α is the vector angle between two adjacent straight line segments.

9. The method for smoothing the corner of the arc offset compensation according to claim 5, characterized in that: The formulas for the starting and ending corner points are: Among them, P i-1、 P i are respectively the starting point coordinates and the ending point coordinates of the previous straight line segment among the two adjacent line segments; S i is the length of the previous straight line segment; is the unit vector from the starting point to the end point of the previous straight line segment, The unit vector pointing from the start point of the next straight line segment to the end point.

10. A numerically controlled machine tool, characterized in that: The arc compensation calculation and instruction interpolation are performed on two adjacent line segments using the angle smoothing control method for compensating arc offset as described in any one of claims 1 to 9.

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