A method for multi-pitch angle calibration error-proofing

Abstract

The application discloses a kind of methods for multi-pendulum angle calibration mistake-proofing, belong to the technical field of inspection and detection, it is characterized in that, comprising the following steps: S1, determine the distribution of each angle of standard ball measuring point;S2, standard ball is fixed on machine tool;S3, obtain standard ball ball center coordinates O';S4, contact probe is installed to machine tool spindle;S5, carry out multi-pendulum angle calibration, and obtain the calibration compensation value r of different angles;S6, calculate the difference δ between each other of multi-pendulum angle compensation value, according to the correctness of the correctness of calibration result if the difference δ is judged measurement part tolerance, if difference δ <1 / 4 product tolerance, then calibration data is correct;S7, if difference δ >1 / 4 product tolerance, then repeat S3-S6 steps.The application directly utilizes the calibration result under multi-pendulum angle to verify each other, both carry out mistake-proofing verification, and do not increase additional time factor, can effectively guarantee the accuracy of calibration result, improve the measurement accuracy and measurement efficiency of on-line measurement.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of inspection and detection, and particularly relates to a method for multi-pendulum-angle calibration error-proofing. BACKGROUND

[0002] Numerical control machining and measurement play an important role in the field of modern production and processing. With the development of intelligent manufacturing, numerical control machining develops towards high precision, high efficiency and large scale. Building an online detection system, loading a three-dimensional trigger type probe as a detection sensor on a numerical control machine tool, combining machining and measurement into one, and orderly alternating machining and measurement under the monitoring environment to ensure machining precision are the mainstream direction of production and manufacturing at this stage. Since the three-dimensional trigger type probe has pre-travel error, anisotropy error and probe eccentricity error, the probe radius value that needs to be compensated is different for different measurement speeds and different measurement directions, so the probe should be calibrated at the corresponding angle according to the normal vector of the measured point.

[0003] Probe calibration is the basis for ensuring measurement accuracy and is an indispensable action before measurement. In the current calibration process, the measurement point on the standard ball with the known ruby contact position on the probe is used to emit a measurement signal to obtain the coordinates of the center of the probe, and then the accurate measurement coordinates are obtained by compensating the probe radius of the probe in the measurement normal direction, that is, by calculating the difference between the actual measurement value and the theoretical measurement value of the measurement point on the standard ball, the deviation caused by the probe in the subsequent part measurement process is compensated. The calibration result is directly used for compensation when measuring after the calibration process is completed, the calibration process lacks checking and error-proofing process, and the abnormality of the probe, the abnormality of the measurement system or the position error of the standard ball is not considered to cause abnormal measurement data, the measurement result is unreliable and cannot meet the demand of high-precision dimension measurement. If the calibration data is inaccurate due to the reasons of measurement system abnormality, probe abnormality and standard ball position error in the calibration process, the accuracy of the online measurement result of the part will be seriously affected, the measurement result will be invalid due to measurement distortion, and the part state will not be controlled in the subsequent processing.

[0004] A linear calibration method for probe pose in on-machine laser measurement is disclosed in Chinese patent document with publication number CN105404238A and publication date of March 16, 2016, which comprises the following steps: establishing a measurement model of laser probe motion on a machine tool, generating an off-line machine tool motion program to make the machine tool drive the probe to scan a standard ball at multiple angles to fit the ball center, and obtaining a linear equation set of the relationship between the standard ball center at multiple machine tool angles and the probe installation pose, and solving the equation set to obtain the probe installation pose parameters.

[0005] The linear calibration method for measuring head pose in machine laser measurement disclosed in the patent document does not need to express the calibration problem as a nonlinear optimization problem with constraints, avoiding a large amount of calculation and instability problems in nonlinear optimization solving. However, error prevention in the multi-angle calibration process cannot be realized, and the accuracy of the calibration data cannot be effectively guaranteed. SUMMARY

[0006] In order to overcome the defects of the prior art, the present application provides a method for multi-angle calibration error prevention, which directly utilizes the calibration results under multi-angle to verify each other, both error prevention verification and additional time factor are not increased, error prevention in the multi-angle calibration process is realized, the accuracy of the calibration results can be effectively guaranteed, and the measurement accuracy and measurement efficiency of online measurement are improved.

[0007] The present application is realized by the following technical solutions:

[0008] A method for multi-angle calibration error prevention, characterized in that it comprises the following steps:

[0009] S1, determining the distribution of measuring points of each angle of the standard ball;

[0010] S2, fixing the standard ball on the machine tool;

[0011] S3, obtaining the center coordinates O' of the standard ball;

[0012] S4, installing the contact probe to the machine tool spindle;

[0013] S5, performing the calibration process, performing multi-angle calibration, and obtaining the calibration compensation values r of different angles;

[0014] S6, calculating the difference δ between the multi-angle compensation values two by two by difference comparison, and judging the correctness of the calibration results according to the tolerance of the measured part, if the difference δ is less than 1 / 4 of the product tolerance, the calibration data is correct;

[0015] S7, if the difference δ is greater than 1 / 4 of the product tolerance, repeat steps S3-S6.

[0016] In the step S1, the distribution of measuring points, the specific steps include:

[0017] S11, when the swing angle is not used, except for the pole point, the standard ball is evenly divided into m parts along the latitude direction from the pole point to 90° below the pole point, then there are measuring points every ( )°; the standard ball is evenly divided into n parts along the longitude direction 0-360°, then there are measuring points every ( )°, then there are ( ) measuring points in one angle;

[0018] S12, after determining the measurement point without using the swing angle, each angle measurement point is formed by rotating the measurement point without using the swing angle with the standard ball center as the rotation center according to the machine tool structure around the X-axis, Y-axis and Z-axis.

[0019] In the step S5, the calibration process is specifically that the standard ball is equally divided into multiple regions along the longitude and latitude, and the probe measures the vertex of each region along the normal of the spherical surface.

[0020] In the step S5, the compensation value r of different angles is specifically the radius compensation value obtained after the probe measures the measurement point under each swing angle, and each swing angle has (n-1) compensation values.

[0021] In the step S5, the point position calibrated under different swing angles has the same point normal of the probe and the same calibration sequence and one-to-one correspondence.

[0022] In the step S6, the difference value δ is the absolute value of the difference between the radius compensation values of the same position in the latitude and longitude direction between any two swing angles.

[0023] The beneficial effects of the present application mainly include the following aspects:

[0024] 1. In the present application, S1, the distribution of the measurement point of each angle of the standard ball is determined; S2, the standard ball is fixed on the machine tool; S3, the ball center coordinates O' of the standard ball are obtained; S4, the contact probe is installed on the machine tool spindle; S5, the calibration process is performed, multi-swing angle calibration is performed, and the compensation value r of different angles is obtained; S6, the difference value δ between the two multi-swing angle compensation values is calculated by difference comparison, and the correctness of the calibration result is judged according to the tolerance of the measured part. If the difference value δ is less than 1 / 4 of the product tolerance, the calibration data is correct; S7, if the difference value δ is greater than 1 / 4 of the product tolerance, the steps S3-S6 are repeated. Compared with the prior art, the calibration results under multi-swing angles are directly verified, which not only prevents errors, but also does not increase additional time factors, realizes error prevention in the multi-swing angle calibration process, and effectively guarantees the accuracy of the calibration result, improves the measurement accuracy and measurement efficiency of online measurement.

[0025] 2. In the present application, the compensation value of each angle is verified by difference comparison, and the reliability of the calibration data can be determined by judging whether the fluctuation range of the multi-swing angle compensation value is within the product control range, which can effectively avoid measurement errors caused by abnormal calibration.

[0026] 3. In the present application, the compensation value of the probe at different angles is verified, which ensures the accuracy of the calibration result and can be used for compensation of the measurement result of the part.

[0027] ​4、The present application does not increase the calibration time, and ensures the efficiency and accuracy of the calibration process.

[0028] 5、The present application one-to-one correspondence between the measurement points of multiple swing angles, through the difference between the corresponding points of multiple swing angles to complete the calibration of any angle error proofing, neither affect the calibration efficiency, and also ensures the accuracy of multiple swing angle calibration compensation value. BRIEF DESCRIPTION OF DRAWINGS

[0029] The present application will be further specifically explained below in combination with the drawings and specific embodiments of the present application:

[0030] Fig. 1 The flow chart of the present application is shown in the figure;

[0031] Fig. 2 The schematic diagram of the present application is shown in the figure;

[0032] Fig. 3 The schematic diagram of the present application is shown in the figure;

[0033] The figure shows: 1, the first swing angle of calibration, 2, the second swing angle of calibration, 3, the third swing angle of calibration, 4, the standard ball, 5, the contact point of the measuring head and the standard ball during calibration, 6, the cutter location point when the measuring head is triggered, 7, the current calibration point compensation value, 8, the measuring head. DETAILED DESCRIPTION

[0034] Embodiment 1

[0035] A method for multiple swing angle calibration error proofing, comprising the following steps:

[0036] S1, determining the distribution of the measurement points of each angle of the standard ball;

[0037] S2, fixing the standard ball on the machine tool;

[0038] S3, obtaining the center coordinate O' of the standard ball;

[0039] S4, installing the contact measuring head to the machine tool spindle;

[0040] S5, performing the calibration process, carrying out multiple swing angle calibration, and obtaining the calibration compensation value r of different angles;

[0041] S6, calculating the difference δ between the multiple swing angle compensation values two by two by difference comparison, and judging the correctness of the calibration result according to the tolerance of the measured part, if the difference δ < 1 / 4 product tolerance, then the calibration data is correct;

[0042] S7, if the difference δ > 1 / 4 product tolerance, then repeat steps S3-S6.

[0043] The embodiment is the most basic implementation, directly uses the calibration results under multiple swing angles for mutual verification, performs error-proof verification, does not increase additional time factors, realizes error-proof in the multiple swing angle calibration process, can effectively guarantee the accuracy of the calibration results, and improves the measurement accuracy and measurement efficiency of online measurement.

[0044] Embodiment 2

[0045] A method for multiple swing angle calibration error-proofing, comprising the following steps:

[0046] S1, determining the distribution of the measurement points of each angle of the standard ball;

[0047] S2, fixing the standard ball on the machine tool;

[0048] S3, obtaining the center coordinates O' of the standard ball;

[0049] S4, installing the contact probe on the spindle of the machine tool;

[0050] S5, performing the calibration process, performing multiple swing angle calibration, and obtaining the calibration compensation values r of different angles;

[0051] S6, calculating the difference δ between the multiple swing angle compensation values two by two by difference comparison, and judging the correctness of the calibration results according to the tolerance of the measured part. If the difference δ is less than 1 / 4 of the product tolerance, the calibration data is correct;

[0052] S7, if the difference δ is greater than 1 / 4 of the product tolerance, repeating steps S3-S6.

[0053] Further, in the step S1, the distribution of the measurement points specifically comprises:

[0054] S11, when the swing angle is not used, the standard ball is divided into m parts along the latitude direction from the pole to 90° below the pole, and then every (m-1) ° distribution measurement point is obtained; the standard ball is divided into n parts along the longitude direction from 0 to 360°, and then every (n-1) ° distribution measurement point is obtained, and then one angle has (m-1) * (n-1) measurement points;

[0055] S12, after determining the measurement points without using the swing angle, the measurement points of each angle are formed by rotating the measurement points without using the swing angle around the X-axis, Y-axis and Z-axis with the center of the standard ball as the rotation center according to the structure of the machine tool.

[0056] The embodiment is a preferred implementation, the compensation values of each angle are two by two difference comparison for mutual verification, the reliability of the calibration data can be determined by judging whether the fluctuation range of the multiple swing angle compensation values is within the product control range, and the measurement result error caused by abnormal calibration can be effectively avoided.​​​

[0057] Embodiment 3

[0058] A method for multi-swing angle calibration error proofing, comprising the steps of:

[0059] S1, determining the distribution of measurement points of each angle of a standard ball;

[0060] S2, fixing the standard ball on a machine tool;

[0061] S3, obtaining the center coordinate O' of the standard ball;

[0062] S4, installing a contact probe on the spindle of the machine tool;

[0063] S5, performing a calibration process to obtain calibration compensation values r at different angles;

[0064] S6, calculating the difference δ between each pair of multi-swing angle compensation values using difference comparison, and determining the correctness of the calibration result according to the tolerance of the measured part. If the difference δ is less than 1 / 4 of the product tolerance, the calibration data is correct.

[0065] S7, if the difference δ is greater than 1 / 4 of the product tolerance, repeating steps S3-S6.

[0066] In the step S1, the distribution of measurement points includes the following specific steps:

[0067] S11, without using swing angle, the standard ball is divided into m parts along the latitude direction from the pole to 90° below the pole, and then every (m / n) ° has a measurement point. The standard ball is divided into n parts along the longitude direction from 0 to 360°, and then every (m / n) ° has a measurement point. Therefore, one angle has (m*n) measurement points.

[0068] S12, after determining the measurement points without using swing angle, the measurement points of each angle are formed by rotating the measurement points without using swing angle around the X, Y and Z axes according to the structure of the machine tool, with the center of the standard ball as the rotation center.

[0069] Further, in the step S5, the calibration process is performed by dividing the standard ball into multiple regions along the longitude and latitude, and measuring the vertex of each region along the normal of the spherical surface.

[0070] In the step S5, the calibration compensation values r at different angles are the radius compensation values obtained after the probe measures the measurement points at each swing angle. Each swing angle has (m*n) compensation values.

[0071] ​​​​The point position calibrated in the step S5 is the same as the point position contacted by the probe in different swing angles, and the calibration sequence is the same and one-to-one corresponding.

[0072] The embodiment is another preferable embodiment, adopts the principle of verifying the compensation values in different angles of the probe with each other, ensures the accuracy of the calibration result, and can be used for compensation of the measurement result of the part.

[0073] Embodiment 4

[0074] A method for multi-swing angle calibration error prevention, comprising the following steps:

[0075] S1, determining the distribution of measurement points of each angle of the standard ball;

[0076] S2, fixing the standard ball on the machine tool;

[0077] S3, obtaining the center coordinate O' of the standard ball;

[0078] S4, installing the contact probe to the spindle of the machine tool;

[0079] S5, performing the calibration process, performing multi-swing angle calibration, and obtaining calibration compensation values r in different angles;

[0080] S6, calculating the difference δ between the multi-swing angle compensation values by difference comparison, and judging the correctness of the calibration result according to the tolerance of the measured part, if the difference δ is less than 1 / 4 of the product tolerance, the calibration data is correct;

[0081] S7, if the difference δ is greater than 1 / 4 of the product tolerance, repeat steps S3-S6.

[0082] In the step S1, the distribution of the measurement points, the specific steps include:

[0083] S11, without using the swing angle, except for the pole point, the standard ball is evenly divided into m parts along the latitude direction from the pole point to 90° below the pole point, then every (m / n) ° distribution measurement point; the standard ball is evenly divided into n parts along the longitude direction 0-360°, then every (m / n) ° distribution measurement point, then one angle has (m*n) measurement points;

[0084] S12, after determining the measurement points without using the swing angle, the measurement points of each angle are formed by rotating the measurement points without using the swing angle around the X axis, Y axis and Z axis as the center of rotation according to the structure of the machine tool.

[0085] In the step S5, the calibration process is specifically that the standard ball is equally divided into multiple regions along the longitude and latitude, and the probe measures the vertex of each region along the normal direction of the spherical surface.

[0086] ​​​In step S5, obtaining the calibration compensation value r at different angles specifically refers to the radius compensation value obtained after the probe measures the measurement point at each swing angle. Each swing angle has ( ) compensation values.

[0087] In step S5, the normal vectors of the points calibrated at different swing angles are the same as those of the points in contact with the probe, and the calibration order is the same and they correspond one-to-one.

[0088] Furthermore, in step S6, the difference δ is the absolute value of the difference between the radius compensation values ​​at the same position in the latitude and longitude directions between any two swing angles.

[0089] This embodiment is the best implementation method, which does not increase the calibration time and ensures the efficiency and accuracy of the calibration process.

[0090] The measurement points between multiple pendulum angles correspond one-to-one. By comparing the differences between the corresponding points of multiple pendulum angles, the calibration error prevention verification of any angle is completed, which does not affect the calibration efficiency and ensures the accuracy of the calibration compensation value of multiple pendulum angles.

[0091] The following is combined Figs. 1-3 The specific implementation process of the present invention will be described as follows:

[0092] Step S1: Determine the distribution of measurement points for each angle of the standard sphere;

[0093] a. When calibrating the standard sphere at each angle, except for the poles, divide the standard sphere along the latitudinal direction from the poles to 90° below the poles into m equal parts. Then each ( )° distribution measurement points; divide the standard sphere into n equal parts along the longitude direction 0-360°, then each ( )° distribution measurement points;

[0094] b. Except for the first angle, taking the AC oscillating machine as an example, first determine the measurement point under A0C0, and denote the radius of the standard ball as R. For each angle to be calibrated, there are a total of ( ( ) calibration points; when the swing angles of A and C are both 0, the pole is... The normal vector matrix is:

[0095]

[0096] c. Move the pole along the latitude m times, each time moving ( )°, that is, forming a series of calibration points distributed along the latitudinal direction, among which The normal vector matrix is:

[0097]

[0098] d. Move along the longitude n times, each time moving ( i.e. a series of calibration points are formed distributed in the longitude direction, wherein The normal vector matrix is:

[0099]

[0100] e. When the coordinate system is located at the center of the standard sphere, the diameter of the standard sphere is recorded as R, and for any calibration point position The coordinate matrix is:

[0101]

[0102] f. For any A, C swing angle, the calibration point under A0C0 is subjected to matrix transformation to obtain the measurement point position of the angle, and then the coordinate matrix of any calibration point is:

[0103]

[0104] Step S2, fix the standard sphere at any position on the machine tool, and install the position in the effective stroke of the machine tool and without interference area;

[0105] Step S3, obtain the accurate standard sphere center coordinates O', fix the standard sphere on the workbench, and position the X, Y and Z positions of the standard sphere through the lever dial gauge and 3D edge finder respectively. Install the lever dial gauge on the spindle, adjust the X, Y position of the machine tool to make the lever dial gauge press the dial 0.3mm when the reading of the dial does not move, and the position is the X, Y position of the center of the standard sphere; install the 3D edge finder on the spindle, measure the distance from the top to the end face of the spindle, move the machine tool to the center of the standard sphere, adjust the Z position of the machine tool to press the measuring needle of the 3D edge finder on the surface of the standard sphere, and calculate the Z position of the center of the standard sphere according to the dial reading;

[0106] Step S4, install the contact probe to the spindle of the machine tool;

[0107] Step S5, execute the calibration process, perform multi-swing angle calibration to obtain calibration compensation values r of different angles, and the measurement software generates a calibration program by recognizing the diameter and position of the measurement standard sphere and measuring the swing angle, through which different measurement swing angles automatically contact measure each measurement point position to obtain compensation data after multi-swing angle calibration;

[0108] Specifically, for the wth layer in the latitude direction and the qth measurement point in the longitude direction of any A, C angle, the compensation value of the point is:

[0109]

[0110] Wherein:

[0111] , and are the measured coordinate values of the point;

[0112] , and are the theoretical coordinate values of the point;

[0113] Step S6, solve the difference δ between the two multi-pendulum angle compensation values, use the difference comparison method to calculate the difference δ, and measure the correctness of the calibration result according to the tolerance of the measured part. If the difference δ is within 1 / 4 of the product tolerance control range, it means that the calibration data is reliable.

[0114] Specifically, the difference δ is the absolute value of the difference between the compensation values of any two A, C angle latitude direction w layer longitude direction q measurement point positions, that is:

[0115]

[0116] Step S7, if there is any difference δ>1 / 4 product tolerance, find out the reason and repeat steps S3-S6;

[0117] Step S8, record the compensation value at each measurement point in step S5 to form a compensation file, and the calibration is completed.

Claims

1. A method for error prevention in multi-angle calibration, characterized in that, Includes the following steps: S1. Determine the distribution of measurement points for each angle of the standard sphere; S2. Fix the standard ball on the machine tool; S3. Obtain the coordinates of the center of the standard sphere, O'. S4. Install the contact probe onto the machine tool spindle; S5. Perform the calibration process, carry out multi-angle calibration, and obtain the calibration compensation value r at different angles; S6. Calculate the difference δ between each pair of multi-angle compensation values ​​using difference comparison. Determine the correctness of the calibration result based on the tolerance of the measured parts. If the difference δ < 1 / 4 of the product tolerance, the calibration data is correct. S7. If the difference δ > 1 / 4 of the product tolerance, repeat steps S3-S6. In step S5, obtaining the calibration compensation value r at different angles specifically refers to the radius compensation value obtained after the probe measures the measurement point at each swing angle. Each swing angle has ( ) compensation value, The number of equal parts along the latitudinal direction of the standard sphere from the pole to 90° below the pole. The number of equal parts that the standard sphere is divided into along the longitude direction from 0 to 360°.

2. The method for error prevention in multi-angle calibration according to claim 1, characterized in that: In step S1, the distribution of measurement points includes the following specific steps: S11. Without using the pendulum angle, except for the pole, divide the standard sphere into m equal parts along the latitudinal direction from the pole to 90° below the pole. Then each ( )° distribution measurement points; divide the standard sphere into n equal parts along the longitude direction 0-360°, then each ( If the measurement points are distributed at a certain angle, then there are a total of ( ) ° measurement points. ) measurement points; S12. After determining the measurement points that do not use the swing angle, the measurement points for each angle are formed by rotating the measurement points that do not use the swing angle around the center of the standard ball, according to the machine tool structure, around the X-axis, Y-axis, and Z-axis.

3. The method for error prevention in multi-angle calibration according to claim 1, characterized in that: In step S5, the calibration process specifically refers to dividing the standard sphere into multiple regions along the longitude and latitude, and measuring the vertex of each region along the normal of the sphere with the probe.

4. The method for error prevention in multi-angle calibration according to claim 1, characterized in that: In step S5, the normal vectors of the points calibrated at different swing angles are the same as those of the points in contact with the probe, and the calibration order is the same and they correspond one-to-one.

5. The method for error prevention in multi-angle calibration according to claim 1, characterized in that: In step S6, the difference δ is the absolute value of the difference between the radius compensation values ​​at the same position in the latitude and longitude directions between any two swing angles.

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