A method and system for measuring edge error of a curved surface based on longitude vector measurement

Abstract

The application discloses a kind of based on fixed longitude vector measurement's curved surface edge error measurement method and system, the method steps include: S1) fixed longitude vector calibration is carried out to the measuring probe to obtain the trigger radius of the measuring probe;S2) according to trigger radius, obtain the measurement program of the edge to be measured;S3) the theoretical profile point coordinate is obtained by the measurement program of the edge to be measured, the actual profile point coordinate is obtained by the measuring probe actual measurement, by comparing theoretical profile point coordinate and actual profile point coordinate, the vector error of the edge to be measured is calculated.Compared with the traditional vector measurement method, the present application can realize the in-machine measurement of curved surface edge error, be used to guide chamfering or edge cutting process, and improve product qualification rate.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of five-axis numerical control, and particularly relates to a curved surface edge error measurement method and system based on fixed longitude vector measurement. BACKGROUND

[0002] Curved surface detection technology is an important part of in-machine measurement, and has a decisive influence on improving the automation efficiency and precision of the machining industry and forming an innovative industry integrating detection and machining. Five-axis is the top of the numerical control industry, and therefore how to realize the measurement of complex curved surfaces of a five-axis machine tool has become an important issue urgently needed to be solved in the industrial field. Edge measurement technology, as a further application of five-axis curved surface measurement, has become a serious obstacle to the processing qualification rate of the industry.

[0003] The commonly used curved surface measurement methods can be divided into normal measurement and vector measurement. The normal measurement requires that the tool axis is parallel to the normal vector of the point to be measured during measurement, while the vector measurement does not have requirements on the direction of the tool axis, and only needs the speed direction to be parallel to the normal vector of the point to be measured. Therefore, compared with the normal measurement, the vector measurement has the following characteristics: 1) wider application range, capable of realizing measurement of a larger range with a smaller stroke of the machine tool; 2) higher measurement efficiency, capable of reducing the rotation of the tool axis and reducing unnecessary actions as much as possible; 3) capable of reducing the error caused by the rotation of the axis due to the reduced rotation angle of the axis; and 4) when actually contacting the measurement point, the ball of the measuring head can be in any position to contact the point to be measured, resulting in complex calculation.

[0004] The curved surface edge feature has the characteristics of small contact area and discontinuous normal vector. The former leads to the difficulty in directly contacting the edge, and the latter leads to the difficulty in calculating the normal vector at the edge. It is difficult to directly measure the edge point, and therefore it is necessary to develop an efficient and accurate indirect measurement scheme. SUMMARY

[0005] The present application aims to overcome the defects of the prior art, and provides a curved surface edge error measurement method and system based on fixed longitude vector measurement. The present application is used for guiding the contour machining of a complex curved surface. The curved surface edge error measurement method based on fixed longitude vector measurement provided by the present application has the following characteristics: the vector measurement can improve the flexibility of measurement and cover a larger range of measurement at a smaller rotation angle; the fixed longitude measurement method can reduce the calibration data and the calculation amount of the system during operation on the premise of ensuring the precision; and the edge calculation realizes the error measurement of the curved surface contour by means of indirect measurement. The present application estimates the error measurement of the curved surface contour by means of indirect measurement, and overcomes the problem that the edge cannot be measured.

[0006] To achieve the above object, the present application adopts the following technical scheme:

[0007] The application discloses a curved surface edge error measurement method based on fixed longitude vector measurement.

[0008] S1) performing fixed longitude vector calibration on the measurement probe to obtain a trigger radius of the measurement probe;

[0009] S2) obtaining a measurement program of the edge to be measured according to the trigger radius;

[0010] S3) obtaining theoretical profile point coordinates through the measurement program of the edge to be measured, obtaining actual profile point coordinates through actual measurement of the measurement probe, and calculating vector error of the edge to be measured by comparing the theoretical profile point coordinates with the actual profile point coordinates.

[0011] Further, the S1) specifically comprises:

[0012] S101) installing the measurement probe on the spindle end and installing a standard gauge on the machine tool workbench;

[0013] S102) determining the tool length of the measurement probe and the distance from the ball center of the measurement probe to the spindle end surface;

[0014] S103) determining the center position coordinates of the standard gauge;

[0015] S104) controlling the machine tool to move the measurement probe to a certain longitude and different latitude positions relative to the standard ball, and calculating the relative distance between the ball center of the measurement probe and the ball center of the standard ball, and then determining the trigger radius at different latitudes of the longitude line.

[0016] Further, before the fixed longitude vector calibration of the measurement probe, the coaxial calibration of the measurement probe and the spindle is further included.

[0017] Further, the coaxial calibration specifically comprises:

[0018] fixing the micrometer on the rotary table, pressing the micrometer needle on the highest point of the side of the measurement probe, rotating the spindle, and observing the needle jump;

[0019] according to the needle jump of the micrometer, adjusting the position of the measurement probe through the probe adjusting bolt to make the needle jump of the micrometer less than a preset value.

[0020] Further, the S1) further comprises: when the fixed longitude vector calibration of the measurement probe is performed, the actual contact position of the measurement probe is calculated through the position of the measured point and the normal vector, so that the trigger radius corresponding to the latitude and longitude is compensated along the normal vector component.

[0021] Further, the S2) specifically comprises:

[0022] S201) importing the trigger radius into the computer-aided manufacturing software to generate the edge curve to be measured;

[0023] S202) The edge curve to be measured is shifted a certain distance to the two adjacent curved surfaces to generate two actual detection curves;

[0024] S203) Establish the normal plane of the curve at the discrete points of the edge curve to be measured and intersect the two actual detection curves at two points to ensure that all three points are on the normal plane of the discrete points of the edge curve to be measured.

[0025] After processing by computer-aided manufacturing software, S204 generates a measurement program for the edge to be measured.

[0026] Furthermore, S3) specifically includes:

[0027] S301) Place the workpiece to be measured on the worktable and confirm the coordinate system of the workpiece;

[0028] S302) The theoretical contour point coordinates of the edge to be measured are obtained through the measurement program of the edge to be measured, and the actual contour point coordinates of the corresponding position of the workpiece to be measured are obtained through the measurement probe.

[0029] S303) Calculate the difference between the coordinates of the theoretical contour points and the actual contour points to obtain the vector error of the edge to be measured.

[0030] Furthermore, the contour points are approximately obtained using the three-plane intersection method.

[0031] Furthermore, the vector measurement also includes vector compensation, specifically including: calculating the actual contact position of the measuring probe by the position of the edge contour point to be measured and the normal vector component, thereby compensating the trigger radius on the corresponding latitude and longitude along the normal vector component.

[0032] This invention also discloses a surface edge error measurement system based on fixed longitude vector measurement, comprising:

[0033] The receiving module is used to receive various data from the edge to be tested;

[0034] The measurement module is used to perform longitude vector calibration of the measurement probe to obtain the trigger radius of the measurement probe based on various data of the edge to be measured; it is used to obtain the measurement program of the edge to be measured based on the trigger radius; it is used to obtain the theoretical contour point coordinates through the measurement program of the edge to be measured, obtain the actual contour point coordinates through actual measurement by the measurement probe, and calculate the vector error of the edge to be measured by comparing the theoretical contour point coordinates and the actual contour point coordinates.

[0035] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention discloses a method for measuring the edge error of a curved surface based on fixed-longitude vector measurement. The method includes the following steps: S1) calibrating the measuring probe with a fixed-longitude vector to obtain the trigger radius of the measuring probe; S2) obtaining the measurement program for the edge to be measured based on the trigger radius; S3) obtaining the theoretical contour point coordinates through the measurement program of the edge to be measured, obtaining the actual contour point coordinates through actual measurement with the measuring probe, and calculating the vector error of the edge to be measured by comparing the theoretical contour point coordinates and the actual contour point coordinates. Compared with traditional vector measurement methods, this invention, through fixed-longitude calibration and compensation, only requires calibrating a few sets of points on a certain longitude line of the measuring probe to complete the measurement, greatly reducing the number of calibrations required for vector measurement and improving work efficiency. Compared with traditional compensation methods, this invention uses linear interpolation, which can estimate the trigger radius and perform compensation at locations where latitude and longitude are not calibrated, thus improving measurement accuracy. Addressing the challenge of directly detecting curved surface edges, this invention employs a "straight line to approximate curve" approach by measuring coordinates near the edge. This indirectly estimates the deviation between the theoretical and actual edge positions, guiding subsequent processing operations and demonstrating significant practical benefits. This invention enables on-machine measurement of curved surface edge errors, guiding processes such as chamfering and trimming, thereby improving product yield. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a flowchart of a surface edge error measurement method based on fixed longitude vector measurement provided by an embodiment of the present invention.

[0038] Figure 2 This is a schematic diagram of the measuring probe and standard fixture of a surface edge error measurement method based on fixed longitude vector measurement provided in an embodiment of the present invention, wherein 1 is the measuring probe, 2 is the standard fixture, and P... t0 To measure the center of the probe sphere, P0 is the center of the standard sphere.

[0039] Figure 3 This is a vector compensation diagram of a surface edge error measurement method based on fixed longitude vector measurement provided in an embodiment of the present invention, wherein 1 is the workpiece to be measured, 2 is the measuring probe, and θ is the latitude.

[0040] Figure 4This is a schematic diagram of workpiece S measurement according to an embodiment of the present invention, which is a surface edge error measurement method based on fixed longitude vector measurement, wherein C1 is the edge curve to be measured.

[0041] Figure 5 This is a partially enlarged view of workpiece S measured according to an embodiment of the present invention, which provides a method for measuring the edge error of a curved surface based on a fixed longitude vector measurement. P cx1 Let P be a point on the edge curve to be measured. cx2 and P cx3 For P cx1 Points on two cross sections. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] See Figures 1 to 5 This invention discloses a method for measuring the edge error of a curved surface based on a fixed longitude vector measurement, comprising:

[0044] S1) The trigger radius of the measuring probe is obtained by performing a fixed longitude vector calibration on the measuring probe; the measuring probe is used for fixed longitude vector calibration, the purpose of which is to reduce the number of calibrations, improve calibration efficiency, and reduce the amount of measurement calculation.

[0045] S2) Based on the trigger radius, obtain the measurement program for the edge to be measured; generally, existing computer-aided manufacturing (CAM) software is used to plan the measurement path and generate the measurement program for the edge to be measured. Specifically, the model to be measured is imported into the CAM software, and the measurement path is generated by extracting the contour curve of the edge to be measured.

[0046] S3) The theoretical contour point coordinates are obtained through the measurement program of the edge to be measured, the actual contour point coordinates are obtained through actual measurement by the measuring probe, and the vector error of the edge to be measured is calculated by comparing the theoretical contour point coordinates and the actual contour point coordinates.

[0047] This invention utilizes a longitude calibration method, requiring only a few sets of points along a specific longitude line of the measuring probe to complete the measurement. This significantly reduces the number of calibrations needed for vector measurements, improving work efficiency. In cases where latitude and longitude are not calibrated, linear interpolation can be used to estimate the trigger radius for compensation, thereby improving measurement accuracy. Furthermore, when it is impossible to directly probe the edge of a curved surface, this invention can indirectly estimate the deviation between the theoretical and actual edge positions by measuring the coordinates near the edge and introducing the concept of "using straight lines to approximate curves." This information guides subsequent processing operations, demonstrating significant guiding value and effective results.

[0048] In a preferred embodiment, S1) specifically includes:

[0049] S101) The measuring probe is mounted on the spindle end, and the spindle drives the measuring probe to move. The standard fixture is then mounted on the machine tool worktable; for example... Figure 5 As shown. The measuring probe is used to measure the position of the workpiece. The standard fixture is used to calculate the trigger radius of the measuring probe. In a preferred embodiment, the measuring probe is a ruby ​​ball measuring probe. In a preferred embodiment, the standard fixture can be a standard ball, standard needle, or standard block, or other tools that facilitate position measurement.

[0050] S102) Determine the length of the measuring probe and the distance from the center of the measuring probe ball to the end face of the spindle; in a preferred embodiment, determining the length of the measuring probe specifically includes: fixing a dial indicator on the worktable, pressing the dial indicator needle against the lowest point of the ruby ​​ball of the measuring probe, recording the current machine tool coordinate value Z1, manually moving the machine tool so that the dial indicator needle is pressed against the end face of the spindle without moving the dial indicator, and recording the machine tool coordinate value Z2. The difference between the two values ​​is the tool length Z0 = Z1 - Z2.

[0051] S103) Determine the center position coordinates of the standard fixture; in a preferred embodiment, the center position of the standard fixture is determined by means of dial indicator, directional measurement with a measuring probe, etc. In a preferred embodiment, the standard fixture is a standard sphere, and determining the center position of the standard sphere includes the following steps: install a measuring probe on the spindle end, fix the standard sphere 2 on the worktable, manually move the machine tool so that the measuring probe just touches the leftmost end of the standard sphere, and record the machine tool coordinate X1. Without moving the Y-axis, make the measuring probe just touch the rightmost end of the standard sphere, and record the machine tool coordinate X2. Then the center coordinate of the standard sphere is X0 = (X1 + X2) / 2.

[0052] S104) Control the machine tool movement to move the measuring probe to a certain longitude and different latitude positions relative to the standard sphere, and calculate the relative distance between the center of the probe sphere and the center of the standard sphere, thereby determining the trigger radius at different latitudes on that longitude line.

[0053] In a preferred embodiment, the steps of the longitude measurement method are as follows: Using a standard sphere as an example, the position of the point to be measured is denoted as P. oi The initial measurement position is denoted as P. gi Then the normal vector of the target point is: Vai = P gi -P oi At this point, a spherical coordinate system can be established at the standard sphere center, and the positioning angle of the principal axis can be determined. Where i and j are the points to be measured, P and j are respectively. ai The components of the normal vector on the X and Y axes.

[0054] In a preferred embodiment, the calibration method at different latitudes is as follows: Taking a standard sphere as an example, the standard gauge is divided into n equal parts along a fixed longitude line from the top of the standard sphere to the equator. The measuring probe is used to touch the position of the point to be measured and the starting measurement position. The distance between the center of the probe tip and the center of the standard sphere is calculated, thereby determining the trigger radius R of the measuring probe sphere at that latitude. θ .

[0055] In a preferred embodiment, during measurement, the theoretical position P of the sphere at a given longitude is obtained by dividing the distance from the apex of the standard sphere to the equator into equal parts according to the calibration division n. oθ By touching this position with the measuring probe, the machine tool coordinates P of the center of the measuring probe sphere at that point are obtained. aθ Then, the trigger radius R at that angle is calculated. θ =P aθ -P oθ -R o ;

[0056] In a preferred embodiment, the measuring probe can communicate with the CNC machine tool. When the measuring probe reads a trigger signal, the CNC machine tool will lock and store the machine tool position coordinates of the center of the measuring probe. This position can be calculated as the actual contact point position using the trigger radius. In the following text, the measuring position of the measuring probe refers to the actual contact point measurement position.

[0057] In a preferred embodiment, before performing longitude vector calibration on the measuring probe, the coaxiality of the measuring probe and the spindle is further calibrated. In a preferred embodiment, the coaxiality calibration specifically includes:

[0058] Fix the dial indicator on the turntable, with the dial indicator needle pressed against the highest point on the side of the measuring probe. Observe the needle movement by manually rotating the spindle.

[0059] Based on the dial indicator needle runout, the position of the measuring probe is adjusted using the probe adjusting screw to ensure the dial indicator needle runout is less than a preset value. At this point, the coaxiality of the measuring probe and the spindle meets the requirements. In a preferred embodiment, the preset value is 5µm.

[0060] In a preferred embodiment, step S1) further includes: when calibrating the measuring probe using a fixed longitude vector, calculating the actual contact position of the measuring probe using the position of the point to be measured and the normal vector component, thereby compensating the trigger radius on the corresponding latitude and longitude along the normal vector component.

[0061] In a preferred embodiment, S2) specifically includes:

[0062] S201) Import parameters such as the trigger radius into the computer-aided manufacturing (CAM) software to generate the edge curve C1 to be measured; the CAM software is NX modeling software.

[0063] S202) The edge curve to be tested is shifted to two adjacent curved surfaces by a certain distance to generate two actual detection curves C2 and C3; the certain distance can be set to 0.5mm.

[0064] S203) Discretize the edge curve C1 to be measured into N points, and at each discrete point P of the edge curve to be measured... cx1 Establish the normal plane F of the curve cx1 It intersects with the two actual detection curves C2 and C3 at two points P respectively. cx2 P cx3 Ensure P cx1 P cx2 P cx3 All three points are discrete points P on the edge curve C1 to be measured. cx1 normal plane F cx1 Above; where N is set to 60.

[0065] After being processed by the modeling software NX, S204 generates a measurement program for the edge to be measured that can be recognized by the CNC device.

[0066] In a preferred embodiment, S3) specifically includes:

[0067] S301) Place the workpiece to be measured on the worktable and confirm the coordinate system of the workpiece;

[0068] S302) The theoretical contour point coordinates of the edge to be measured are obtained through the measurement program of the edge to be measured, and the actual contour point coordinates of the corresponding position of the workpiece to be measured are obtained through the measuring probe. Specifically, during measurement, the rotation angle φ of the measuring probe on the spindle is determined according to the position and orientation of the point to be measured on the curved surface, so that when measuring any point of the workpiece, the longitude fixed on the probe ball touches the point to be measured, and the longitude here is consistent with the calibrated longitude in S104). In a preferred embodiment, the spindle following mode is used for measurement, that is, the spindle is rotated according to the normal vector of the measured point, so that the same longitude line of the measuring probe is always used for measurement, and the longitude here is consistent with the calibrated longitude in S104).

[0069] In a preferred embodiment, the contour points are approximately obtained using the three-plane intersection method, specifically including: extracting the test point P on the edge curve C1 to be measured. cx1 The other two points P at the cross section cx2 P cx3 and the two normal vectors V at their corresponding positions cx2 V cx3 plane F cx2 Through point P cx2 The normal vector is V cx2 The tangent plane, plane F cx3 Through point P cx3 The normal vector is V cx3 The tangent plane, point P cx1 P cx2 P cx3 Forming plane F cx1 plane F cx1 F cx2 F cx3 The intersection of and is the theoretical profile point at that cross section.

[0070] S303) Calculate the coordinates P of the theoretical contour point. cx and the actual contour point coordinates P ax The difference is used to obtain the vector error E of the edge to be measured. x =P ax -P cx In a preferred embodiment, the vector error is obtained by comparing the XYZ coordinate components of the theoretical contour point and the actual contour point, and can characterize the vector deviation of the contour point.

[0071] It is worth noting that P cx2 and P cx3 The data is variable, specifically P extracted from the measurement program used to calculate the theoretical edge contour points of the edge to be measured. cx2 and P cx3 Coordinates, while the actual edge contour points are calculated by substituting the P values ​​measured by the measuring probe. ax2 and P ax3 Coordinates. And P cx1 F cx1 V cx2 V cx3 All data are extracted from the measurement program of the edge to be measured generated by NX model software, and are unrelated to actual measurement data. Although this invention uses the three-plane intersection method, the theoretical and practical edge contour point calculation rules are consistent.

[0072] In a preferred embodiment, the vector measurement further includes vector compensation, specifically including: calculating the actual contact position of the measuring probe based on the position of the edge contour point to be measured and the normal vector component, thereby adjusting the corresponding latitude and longitude θ. i The trigger radius R oni Compensation is performed along the normal vector component, and the specific calculation formula is as follows: Among them, R i For the corresponding latitude θ i The trigger radius, R i+1 and R i-1 For two adjacent latitudes θ i+1 and θ i-1 The trigger radius, R here i This is the trigger radius obtained in S1). Actual contact point P ai To measure the position P of the probe's center of gravity when the probe touches the target. ao With trigger radius R i The sum of the normal vector components at that point.

[0073] Compared to traditional vector measurement methods, this invention, through fixed longitude calibration and compensation, only requires calibrating 10 sets of points on a certain longitude line of the measuring probe to complete the measurement, which greatly reduces the number of calibrations required for vector measurement and improves work efficiency.

[0074] In a preferred embodiment, the method of the present invention is also applicable to the measurement of edge errors of curved surfaces and planes of three-axis and five-axis machine tools. When performing five-axis measurements, the coordinate transformation of the rotary axis motion should also be considered.

[0075] In a preferred embodiment, to describe the measurement process for workpiece S with curved edge features, the edge measurement is taken as an example. A five-axis machine tool with an AC dual rotary table is used for measurement. Workpiece S is an industry standard part with curved surface features. A five-axis machine tool is used to describe the five-axis measurement function.

[0076] In a preferred embodiment, the spindle angle is fixed at 180° and held stationary, and the positions of the standard sphere at different latitudes along the 0° longitude line are measured. The calibration accuracy is set to 10°, and the center of the standard sphere is used as the zero point of the reference coordinate system to measure positions from 0 to 90° latitude along the 0° longitude line. In a preferred embodiment, the physical radius of the standard sphere is 15mm, and the radius of the measuring probe sphere is 3mm. The measuring probe is used to touch the Cartesian coordinate system position corresponding to the aforementioned longitude and latitude, and the distance between the tip of the probe sphere and the center of the standard sphere is calculated, thereby determining the trigger radius R of the measuring probe sphere at that latitude. θ Taking latitude 50° calibration as an example, the standard spherical coordinates are: N(15×cos50,0,15×sin50), and the actual measurement position is T(x,0,y). Therefore, the trigger radius R at this location is... 50 =|TN|-15.

[0077] It is worth noting that, in calculating the coordinate position, the method of the present invention preferably uses the coordinates of the measuring probe as the coordinates of the machine tool coordinate system. By shifting the measuring probe in the detection direction to the trigger radius at the current detection angle, the trigger radius at any angle can be obtained based on the linear difference of the vector calibration.

[0078] This invention also discloses a surface edge error measurement system based on fixed longitude vector measurement, comprising:

[0079] The receiving module is used to receive various data from the edge to be tested;

[0080] The measurement module is used to perform longitude vector calibration on the measurement probe based on various data of the edge to be measured, thereby obtaining the trigger radius of the measurement probe. The measurement probe is used for longitude vector calibration and vector detection. The purpose of longitude vector calibration is to reduce the number of calibrations, improve calibration efficiency, and reduce the computational load. The vector detection is used to measure surface features and perform vector compensation. In surface measurement, accurate measurement coordinates can be obtained based on the normal vector of the point to be measured and the trigger radius. The module is used to obtain the measurement program for the edge to be measured based on the trigger radius; generally, existing computer-aided manufacturing (CAM) software is used to plan the measurement path and generate the measurement program for the edge to be measured. The module is used to obtain the theoretical contour point coordinates through the measurement program for the edge to be measured, and the actual contour point coordinates are obtained through actual measurement by the measurement probe. By comparing the theoretical and actual contour point coordinates, the vector error of the edge to be measured is calculated. The theoretical and actual contour point coordinates obtained from the measurement program should be measured at positions on the same longitude line to ensure the accuracy of the measurement results. The detection action is controlled by the detection program in the CNC device, which generally uses existing CAM software to plan the measurement path and generate the detection program. After the detection is completed, based on the measured actual coordinates and the theoretical coordinate data exported from CAM, the theoretical contour point coordinates and actual contour point coordinates of the edge curve to be measured are obtained, and the vector error of the edge to be measured is calculated. In actual detection operations, measurements should be taken at positions on the same longitude line to ensure the accuracy of the measurement results.

[0081] In a preferred embodiment, the step of performing a fixed-longitude vector calibration on the measuring probe to obtain the trigger radius of the measuring probe specifically includes:

[0082] S101) The measuring probe is mounted on the spindle end, and the spindle drives the measuring probe to move. The standard fixture is then mounted on the machine tool worktable; for example... Figure 5 As shown. The measuring probe is used to measure the position of the workpiece. The standard fixture is used to calculate the trigger radius of the measuring probe. In a preferred embodiment, the measuring probe is a ruby ​​ball measuring probe. In a preferred embodiment, the standard fixture can be a standard ball, standard needle, or standard block, or other tools that facilitate position measurement.

[0083] S102) Determine the length of the measuring probe and the distance from the center of the measuring probe ball to the end face of the spindle; in a preferred embodiment, determining the length of the measuring probe specifically includes: fixing a dial indicator on the worktable, pressing the dial indicator needle against the lowest point of the ruby ​​ball of the measuring probe, recording the current machine tool coordinate value Z1, manually moving the machine tool so that the dial indicator needle is pressed against the end face of the spindle without moving the dial indicator, and recording the machine tool coordinate value Z2. The difference between the two values ​​is the tool length Z0 = Z1 - Z2.

[0084] S103) Determine the center position coordinates of the standard fixture; in a preferred embodiment, the center position of the standard fixture is determined by means of dial indicator, directional measurement with a measuring probe, etc. In a preferred embodiment, the standard fixture is a standard sphere, and determining the center position of the standard sphere includes the following steps: install a measuring probe on the spindle end, fix the standard sphere 2 on the worktable, manually move the machine tool so that the measuring probe just touches the leftmost end of the standard sphere, and record the machine tool coordinate X1. Without moving the Y-axis, make the measuring probe just touch the rightmost end of the standard sphere, and record the machine tool coordinate X2. Then the center coordinate of the standard sphere is X0 = (X1 + X2) / 2.

[0085] S104) Control the machine tool movement to move the measuring probe to a certain longitude and different latitude positions relative to the standard sphere, and calculate the relative distance between the center of the probe sphere and the center of the standard sphere, thereby determining the trigger radius at different latitudes on that longitude line.

[0086] In a preferred embodiment, the steps of the longitude measurement method are as follows: Using a standard sphere as an example, the position of the point to be measured is denoted as P. oi The initial measurement position is denoted as P. gi Then the normal vector of the target point is: V ai =P gi -P oi At this point, a spherical coordinate system can be established at the standard sphere center, and the positioning angle of the principal axis can be determined. Where i and j are the points to be measured, P and j are respectively. ai The components of the normal vector on the X and Y axes.

[0087] In a preferred embodiment, the calibration method at different latitudes is as follows: Taking a standard sphere as an example, the standard gauge is divided into n equal parts along a fixed longitude line from the top of the standard sphere to the equator. The measuring probe is used to touch the position of the point to be measured and the starting measurement position. The distance between the center of the probe tip and the center of the standard sphere is calculated, thereby determining the trigger radius R of the measuring probe sphere at that latitude. θ .

[0088] In a preferred embodiment, during measurement, the theoretical position P of the sphere at a given longitude is obtained by dividing the distance from the apex of the standard sphere to the equator into equal parts according to the calibration division n. oθBy touching this position with the measuring probe, the machine tool coordinates P of the center of the measuring probe sphere at that point are obtained. aθ Then, the trigger radius R at that angle is calculated. θ =P aθ -P oθ -R o ;

[0089] In a preferred embodiment, the measuring probe can communicate with the CNC machine tool. When the measuring probe reads a trigger signal, the CNC machine tool will lock and store the machine tool position coordinates of the center of the measuring probe. This position can be calculated as the actual contact point position using the trigger radius. In the following text, the measuring position of the measuring probe refers to the actual contact point measurement position.

[0090] In a preferred embodiment, before performing longitude vector calibration on the measuring probe, the coaxiality of the measuring probe and the spindle is further calibrated. In a preferred embodiment, the coaxiality calibration specifically includes:

[0091] Fix the dial indicator on the turntable, with the dial indicator needle pressed against the highest point on the side of the measuring probe. Observe the needle movement by manually rotating the spindle.

[0092] Based on the dial indicator needle runout, the position of the measuring probe is adjusted using the probe adjusting screw to ensure the dial indicator needle runout is less than a preset value. At this point, the coaxiality of the measuring probe and the spindle meets the requirements. In a preferred embodiment, the preset value is 5µm.

[0093] In a preferred embodiment, the step of obtaining the trigger radius of the measuring probe by performing a fixed longitude vector calibration further includes: when performing a fixed longitude vector calibration on the measuring probe, calculating the actual contact position of the measuring probe by the position of the point to be measured and the normal vector component, thereby compensating the trigger radius on the corresponding latitude and longitude along the normal vector component.

[0094] In a preferred embodiment, the measurement procedure for obtaining the edge to be measured based on the trigger radius specifically includes:

[0095] S201) Import parameters such as the trigger radius into the computer-aided manufacturing software to generate the edge curve C1 to be measured; the computer-aided manufacturing software is NX computer-aided manufacturing software.

[0096] S202) The edge curve to be tested is shifted to two adjacent curved surfaces by a certain distance to generate two actual detection curves C2 and C3; the certain distance can be set to 0.5mm.

[0097] S203) Discretize the edge curve C1 to be measured into N points, and at each discrete point P of the edge curve to be measured... cx1 Establish the normal plane F of the curve cx1 It intersects with the two actual detection curves C2 and C3 at two points P respectively.cx2 P cx3 Ensure P cx1 P cx2 P cx3 All three points are discrete points P on the edge curve C1 to be measured. cx1 normal plane F cx1 Above; where N is set to 60.

[0098] S204) After being processed by the computer-aided manufacturing software NX, a measurement program for the edge to be measured is generated.

[0099] In a preferred embodiment, the theoretical contour point coordinates are obtained through the measurement procedure of the edge to be measured, the actual contour point coordinates are obtained through actual measurement by the measuring probe, and the vector error of the edge to be measured is calculated by comparing the theoretical contour point coordinates and the actual contour point coordinates. Specifically, this includes:

[0100] S301) Place the workpiece to be measured on the worktable and confirm the coordinate system of the workpiece;

[0101] S302) The theoretical contour point coordinates of the edge to be measured are obtained through the measurement program of the edge to be measured, and the actual contour point coordinates of the corresponding position of the workpiece to be measured are obtained through the measuring probe. Specifically, during measurement, the rotation angle φ of the measuring probe on the spindle is determined according to the position and orientation of the point to be measured on the curved surface, so that when measuring any point of the workpiece, the longitude fixed on the probe ball touches the point to be measured, and the longitude here is consistent with the calibrated longitude in S104). In a preferred embodiment, the spindle following mode is used for measurement, that is, the spindle is rotated according to the normal vector of the measured point, so that the same longitude line of the measuring probe is always used for measurement, and the longitude here is consistent with the calibrated longitude in S104).

[0102] In a preferred embodiment, the contour points are approximately obtained using the three-plane intersection method, specifically including: extracting the test point P on the edge curve C1 to be measured. cx1 The other two points P at the cross section cx2 P cx3 and the two normal vectors V at their corresponding positions cx2 V cx3 plane F cx2 Through point P cx2 The normal vector is V cx2 The tangent plane, plane F cx3 Through point P cx3 The normal vector is V cx3 The tangent plane, point P cx1 P cx2 P cx3 Forming plane F cx1 plane F cx1 F cx2 Fcx3 The intersection of and is the theoretical profile point at that cross section.

[0103] S303) Calculate the coordinates P of the theoretical contour point. cx and the actual contour point coordinates P ax The difference is used to obtain the vector error E of the edge to be measured. x =P ax -P cx In a preferred embodiment, the vector error is obtained by comparing the XYZ coordinate components of the theoretical contour point and the actual contour point, and can characterize the vector deviation of the contour point.

[0104] It is worth noting that P cx2 and P cx3 The data is variable, specifically P extracted from the measurement program used to calculate the theoretical edge contour points of the edge to be measured. cx2 and P cx3 Coordinates, while the actual edge contour points are calculated by substituting the P values ​​measured by the measuring probe. ax2 and P ax3 Coordinates. And P cx1 F cx1 V cx2 V cx3 All data are extracted from the measurement program of the edge to be measured generated by NX model software, and are unrelated to actual measurement data. Although this invention uses the three-plane intersection method, the theoretical and practical edge contour point calculation rules are consistent.

[0105] In a preferred embodiment, the vector measurement further includes vector compensation, specifically including: calculating the actual contact position of the measuring probe based on the position of the edge contour point to be measured and the normal vector component, thereby adjusting the corresponding latitude and longitude θ. i The trigger radius R on i Compensation is performed along the normal vector component, and the specific calculation formula is as follows: Among them, R i For the corresponding latitude θ i The trigger radius, R i+1 and R i-1 For two adjacent latitudes θ i+1 and θ i-1 The trigger radius. Actual contact point P. ai To measure the position P of the probe's center of gravity when the probe touches the target. ao With trigger radius R i The sum of the normal vector components at that point.

[0106] Compared to traditional vector measurement methods, this invention, through fixed longitude calibration and compensation, only requires calibrating 10 sets of points on a certain longitude line of the measuring probe to complete the measurement, which greatly reduces the number of calibrations required for vector measurement and improves work efficiency.

[0107] In a preferred embodiment, the method of the present invention is also applicable to the measurement of edge errors of curved surfaces and planes of three-axis and five-axis machine tools. When performing five-axis measurements, the coordinate transformation of the rotary axis motion should also be considered.

[0108] In a preferred embodiment, to describe the measurement process for workpiece S with curved edge features, the edge measurement is taken as an example. A five-axis machine tool with an AC dual rotary table is used for measurement. Workpiece S is an industry standard part with curved surface features. A five-axis machine tool is used to describe the five-axis measurement function.

[0109] In a preferred embodiment, the spindle angle is fixed at 180° and held stationary, and the positions of the standard sphere at different latitudes along the 0° longitude line are measured. The calibration accuracy is set to 10°, and the center of the standard sphere is used as the zero point of the reference coordinate system to measure positions from 0 to 90° latitude along the 0° longitude line. In a preferred embodiment, the physical radius of the standard sphere is 15mm, and the radius of the measuring probe sphere is 3mm. The measuring probe is used to touch the Cartesian coordinate system position corresponding to the aforementioned longitude and latitude, and the distance between the tip of the probe sphere and the center of the standard sphere is calculated, thereby determining the trigger radius R of the measuring probe sphere at that latitude. θ Taking latitude 50° calibration as an example, the standard spherical coordinates are: N(15×cos50,0,15×sin50), and the actual measurement position is T(x,0,y). Therefore, the trigger radius R at this location is... 50 =|TN|-15.

[0110] It is worth noting that, when calculating the coordinate position, the method of the present invention preferably measures the coordinates of the probe and shifts the probe in the detection direction to the trigger radius at the current detection angle. Thus, the trigger radius at any angle can be obtained based on the linear difference of the vector calibration.

[0111] This invention utilizes a longitude calibration method, requiring only a few sets of points along a specific longitude line of the measuring probe to complete the measurement, significantly reducing the number of calibrations needed for vector measurements and improving work efficiency. In the absence of latitude and longitude calibration, linear interpolation can be used to estimate the trigger radius for compensation, thereby improving measurement accuracy. This invention, by measuring the coordinates near the edge and introducing the concept of "using straight lines to approximate curves," indirectly estimates the deviation between the theoretical and actual positions of the edge processing location, guiding subsequent processing operations and demonstrating significant guiding value and effective work results.

[0112] Based on the same inventive concept, this invention also discloses an electronic device, which may include: a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other through the communication bus. The processor can call logical instructions in the memory to execute a surface edge error measurement method based on fixed longitude vector measurement. The method includes: S1) performing fixed longitude vector calibration on the measuring probe to obtain the trigger radius of the measuring probe; S2) obtaining the measurement program of the edge to be measured according to the trigger radius; S3) obtaining the theoretical contour point coordinates through the measurement program of the edge to be measured, obtaining the actual contour point coordinates through actual measurement by the measuring probe, and calculating the vector error of the edge to be measured by comparing the theoretical contour point coordinates and the actual contour point coordinates.

[0113] Furthermore, the logical instructions in the aforementioned memory can be implemented as software functional units and sold or used as independent products, and can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0114] On the other hand, embodiments of the present invention also provide a computer program product, the computer program product including a computer program stored on a non-transitory computer-readable storage medium, the computer program including program instructions, when the program instructions are executed by a computer, the computer is able to execute a surface edge error measurement method based on fixed longitude vector measurement provided in the above-described method embodiments, the method including: S1) performing fixed longitude vector calibration on the measuring probe to obtain the trigger radius of the measuring probe; S2) obtaining the measurement program of the edge to be measured according to the trigger radius; S3) obtaining the theoretical contour point coordinates through the measurement program of the edge to be measured, obtaining the actual contour point coordinates through actual measurement by the measuring probe, and calculating the vector error of the edge to be measured by comparing the theoretical contour point coordinates and the actual contour point coordinates.

[0115] In another aspect, embodiments of the present invention also provide a non-transitory computer-readable storage medium storing a computer program thereon. When executed by a processor, the computer program implements a surface edge error measurement method based on fixed longitude vector measurement provided in the above embodiments. The method includes: S1) performing fixed longitude vector calibration on the measuring probe to obtain the trigger radius of the measuring probe; S2) obtaining the measurement program of the edge to be measured according to the trigger radius; S3) obtaining the theoretical contour point coordinates through the measurement program of the edge to be measured, obtaining the actual contour point coordinates through actual measurement by the measuring probe, and calculating the vector error of the edge to be measured by comparing the theoretical contour point coordinates and the actual contour point coordinates.

[0116] It should be understood that although the steps in the flowcharts of the accompanying figures are shown sequentially as indicated by the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the accompanying figures may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times, and their execution order is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the sub-steps or stages of other steps.

[0117] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for measuring the edge error of a curved surface based on fixed longitude vector measurement, characterized in that, include: S1) The trigger radius of the measuring probe is obtained by performing a fixed longitude vector calibration. S2) Obtain the measurement program for the edge to be measured based on the trigger radius; S3) The theoretical contour point coordinates are obtained through the measurement program of the edge to be measured, the actual contour point coordinates are obtained through the actual measurement of the measuring probe, and the vector error of the edge to be measured is calculated by comparing the theoretical contour point coordinates and the actual contour point coordinates. S1) specifically includes: S101) Install the measuring probe on the spindle end and install the standard fixture on the machine tool table; S102) Determine the length of the measuring probe and the distance from the center of the measuring probe ball to the end face of the spindle; S103) Determine the center coordinates of the standard inspection fixture; S104) Control the machine tool movement to move the measuring probe to a certain longitude and different latitude positions relative to the standard sphere, and calculate the relative distance between the center of the probe sphere and the center of the standard sphere, thereby determining the trigger radius at different latitudes on that longitude line; The S1) further includes: when calibrating the measuring probe with a fixed longitude vector, the actual contact position of the measuring probe is calculated by the position of the point to be measured and the normal vector, so as to compensate the trigger radius on the corresponding latitude and longitude along the normal vector component; S2) specifically includes: S201) Import the trigger radius into the computer-aided manufacturing software to generate the edge curve to be measured; S202) The edge curve to be measured is shifted a certain distance to the two adjacent curved surfaces to generate two actual detection curves; S203) Establish the normal plane of the curve at the discrete points of the edge curve to be measured and intersect the two actual detection curves at two points, ensuring that all three points are on the normal plane of the discrete points of the edge curve to be measured. S204) After being processed by computer-aided manufacturing software, a measurement program for the edge to be measured is generated.

2. The method for measuring surface edge error based on fixed longitude vector measurement as described in claim 1, characterized in that, Before performing longitude vector calibration on the measuring probe, the coaxiality of the measuring probe and the spindle is also calibrated.

3. The method for measuring surface edge error based on fixed longitude vector measurement as described in claim 2, characterized in that, The coaxiality calibration specifically includes: Fix the dial indicator on the turntable, press the dial indicator needle to the highest point on the side of the measuring probe, rotate the spindle, and observe the needle movement. Based on the dial indicator needle movement, adjust the position of the measuring probe using the probe adjustment screw to ensure that the dial indicator needle movement is less than the preset value.

4. The method for measuring surface edge error based on fixed longitude vector measurement as described in claim 1, characterized in that, S3 specifically includes: S301) Place the workpiece to be measured on the worktable and confirm the coordinate system of the workpiece; S302) The theoretical contour point coordinates of the edge to be measured are obtained through the measurement program of the edge to be measured, and the actual contour point coordinates of the corresponding position of the workpiece to be measured are obtained through the measurement probe. S303) Calculate the difference between the coordinates of the theoretical contour points and the actual contour points to obtain the vector error of the edge to be measured.

5. The surface edge error measurement method based on fixed longitude vector measurement as described in claim 4, characterized in that, The contour points are approximately obtained using the three-plane intersection method.

6. The method for measuring surface edge error based on fixed longitude vector measurement as described in claim 1, characterized in that, The vector measurement also includes vector compensation, specifically: calculating the actual contact position of the measuring probe by the position of the edge contour point to be measured and the normal vector component, thereby compensating the trigger radius on the corresponding latitude and longitude along the normal vector component.

7. A surface edge error measurement system based on fixed longitude vector measurement, characterized in that, include: The receiving module is used to receive various data from the edge to be tested; The measurement module is used to perform longitude vector calibration of the measurement probe to obtain the trigger radius of the measurement probe based on various data of the edge to be measured; it is used to obtain the measurement program of the edge to be measured based on the trigger radius; it is used to obtain the theoretical contour point coordinates through the measurement program of the edge to be measured, obtain the actual contour point coordinates through the actual measurement of the measurement probe, and calculate the vector error of the edge to be measured by comparing the theoretical contour point coordinates and the actual contour point coordinates. The specific steps of obtaining the trigger radius of the measuring probe by performing a fixed longitude vector calibration include: S101) Install the measuring probe on the spindle end and install the standard gauge on the machine tool worktable; S102) Determine the length of the measuring probe and the distance from the center of the measuring probe ball to the end face of the spindle; S103) Determine the center coordinates of the standard inspection fixture; S104) Control the machine tool movement to move the measuring probe to a certain longitude and different latitude positions relative to the standard sphere, and calculate the relative distance between the center of the probe sphere and the center of the standard sphere, thereby determining the trigger radius at different latitudes on that longitude line; The vector measurement also includes vector compensation, specifically including: when calibrating the measuring probe with a fixed longitude vector, the actual contact position of the measuring probe is calculated by the position of the point to be measured and the normal vector, thereby compensating the trigger radius on the corresponding latitude and longitude along the normal vector component; The measurement procedure for obtaining the edge to be measured based on the trigger radius specifically includes: S201) Import the trigger radius into the computer-aided manufacturing software to generate the edge curve to be measured; S202) The edge curve to be measured is shifted a certain distance to the two adjacent curved surfaces to generate two actual detection curves; S203) Establish the normal plane of the curve at the discrete points of the edge curve to be measured and intersect the two actual detection curves at two points, ensuring that all three points are on the normal plane of the discrete points of the edge curve to be measured. S204) After being processed by computer-aided manufacturing software, a measurement program for the edge to be measured is generated.

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