A method for identifying the installation error of a large gear

Abstract

An embodiment of the present invention relates to a method for identifying the installation error of a large gear. By utilizing the multi-axis interpolation motion function of a numerical control machine tool, an original data set is obtained by measuring any complete circumferential profile on the gear with an axis of rotation as the axis through a scanning probe; a low-frequency profile scanning data set is obtained from the original data set, and the low-frequency profile scanning data set is combined with the theoretical radius of the measured circle and plotted in polar coordinates, and the theoretically circular section becomes an ellipse in the polar coordinate system; the points in the polar coordinates are converted into the Cartesian coordinate system to obtain the center coordinates of the ellipse, and the vector connecting the center coordinate point and the origin of the Cartesian coordinate system reflects the magnitude and phase of the geometric installation error; the minor axis of the ellipse is the yaw axis, and the yaw angle can be deduced according to the ratio of the minor axis to the major axis. The present invention can simultaneously judge the geometric eccentricity and phase of the gear, the end face yaw angle and direction, and is used to guide the correction of the installation error, thereby providing conditions for accurate detection.

Description

Technical Field

[0001] The present invention belongs to the technical field of precision machining of large gears, and particularly relates to a method for identifying the installation error of large gears. Background Art

[0002] Large-sized gears mainly refer to gears with a radius greater than 250 mm, which are widely used in ships, construction machinery, water conservancy power generation, etc. To improve production efficiency, the rough machining or semi-finishing of such gears is mostly carried out on machine tools such as hobbing machines, and the final finishing process is completed on a gear grinding machine. However, regardless of the machining process, the gear needs to be fixed on the rotary workbench in advance, and this process will generate the installation error of the gear. To avoid affecting the machining result of the gear tooth surface, this error must be corrected.

[0003] When the gear is installed on the rotary table, there will be a geometric eccentricity error caused by the gap between the gear shaft hole and the rotary table spindle and a yaw error caused by the inclination angle between the gear end face and the installation end face, that is, the parallelism error. The geometric eccentricity error and the parallelism error are collectively referred to as the installation error. If not corrected, it will lead to gear machining errors. Especially for large gears, even a small gear installation error will magnify the end tooth surface machining error due to the too large radius. Therefore, it is necessary to adjust the installation of large gears. There are many reasons for the gear installation error, mainly from the non-coincidence of the reference during mechanical hoisting and the inaccuracy of the detection instrument during manual calibration.

[0004] At present, in the actual production process, the small arc method using a standard ball or the standard gauge method using gauge blocks is mostly used to identify the gear center parameters. These methods can often only identify a certain type of geometric error or yaw error, and the accuracy is low. Some enterprises use the tooth profile or pitch measurement data to reverse deduce the eccentric geometric installation error. This type of method assumes that the tooth profile of the gear to be measured is a standard involute in principle. However, for some gears, in order to meet the use performance requirements, the tooth surface usually needs to be modified, which will cause this type of reverse deduction method to go wrong. Some scholars have proposed to use the method of plane fitting after multi-point measurement of the end face, but ignored the error existing in the gear end face itself.

[0005] In addition, there is also the use of special instruments for measurement. This method has great limitations, is time-consuming and laborious, is only applicable to gears of a certain size specification, and due to the influence of manual operation, the repeatability of the measurement position is poor, and there will be a principle error. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for identifying the installation error of large gears, which can simultaneously judge the geometric eccentricity, phase, end face yaw angle and direction of the gear, and is used to guide the correction of the installation error, so as to provide conditions for accurate detection.

[0007] The technical solution of the present invention is as follows:

[0008] To achieve the above object, the present invention provides a method for identifying the installation error of a large gear, comprising the following steps:

[0009] S1: First, install the probe, check the fixation of the gear to be measured, set the measurement operation parameters to ensure that the probe returns normal values; rotate the rotary table and start the measurement.

[0010] S2: Then, process the measurement data and separate the frequency components by using the wavelet decomposition method.

[0011] S3: Plot the processed measurement points in the polar coordinate system.

[0012] S4: Convert the points in the polar coordinate system to the Cartesian coordinate system.

[0013] S5: Use the least squares fitting method to perform ellipse fitting on the measurement points in the Cartesian coordinate system.

[0014] S6: Determine the magnitude and azimuth of the yaw angle, and the magnitude and phase of the geometric eccentricity according to the fitted ellipse.

[0015] S7: Adjust the gear installation position according to the determined yaw angle and geometric error, and judge whether the identified installation error parameters meet the requirements; if not, return to step S1 and start iterative execution again; otherwise, take the current adjusted state as the initial machining state of the gear and end the installation error correction.

[0016] Further, step S1 is specifically:

[0017] Install the gear on the rotary worktable, check the clamping condition of the fixture of the rotary worktable and the gear to be measured. First, use the manual calibration method to ensure the coaxiality of the central axis of the gear to be measured and the central axis of the rotary worktable and the parallelism of the end face of the gear to be measured and the end face of the rotary worktable as much as possible; after the inspection, install a scanning probe on the machine tool, place the probe at any position on the circumference to be scanned, and combine the C-axis rotary interpolation motion to scan any complete circumference with the rotary axis as the axis on the gear to obtain the original data set X c ={x1,x2,x3...x n}, where n is the number of original data values.

[0018] Further, step S2 is specifically:

[0019] Eliminate the high-frequency components such as noise, roughness, and waviness in the original data set, and leave the low-frequency components reflecting the contour; use the wavelet decomposition method to separate the frequency components and reconstruct the low-frequency components to obtain the low-frequency contour scanning data set X d ={x d1 ,x d2 ,xd3 ...x dm}, where m is the number of low-frequency profile scan data values.

[0020] Further, the above step S3 is specifically as follows:

[0021] Divide the low-frequency profile scan data set X d According to the time series, determine the angle x of each measurement point in the polar coordinate system in a 360° equal division manner di-angle , and the calculation formula is:

[0022] x di-angle = i * 360 / m (i = 1 ~ m) (1)

[0023] The scanning probe outputs relative measurement values, so the data is processed: determine the radius change amount x of each measurement point in the polar coordinate system with the relative measurement data value di-length , and the calculation formula is:

[0024]

[0025] Then the measured radius size of each measurement point in the polar coordinate system is recorded as:

[0026] x di-ρ = R + x di-length (i = 1 ~ m) (3)

[0027] In formula (3), R is the theoretical radius value of the measured circumference;

[0028] Thus, the coordinate sequence Co of all measurement points in the polar coordinate system is obtained as:

[0029] Co = {(x di-ρ , x di-angle ) | i = 1 ~ m} (4).

[0030] Further, the above step S4 is specifically as follows:

[0031] Convert the points in the polar coordinate system to the Cartesian coordinate system, and we have:

[0032]

[0033] In formula (5), X di , Y di are the coordinate values of the measurement points in the Cartesian coordinate system.

[0034] Further, the above step S5 is specifically as follows:

[0035] Use the least squares fitting method to perform ellipse fitting on the measurement points in the Cartesian coordinate system. For an ellipse with any center coordinate and offset angle, it can be expressed in the following general form:

[0036] x 2 +Axy + By 2 +Cx + Dy + E = 0 (6)

[0037] In formula (6), A, B, C, D, and E are parameters of the elliptical equation in general form;

[0038] The least - squares ellipse fitting formula is:

[0039]

[0040] In formula (7), i = 1 to m;

[0041] Substitute all the measured points (X di , Y di ) in the Cartesian coordinate system into formula (7) to obtain the parameters A, B, C, D, and E; Calculate the five parameters of the ellipse according to the mathematical model of the standard ellipse: the ellipse center coordinate parameters (x0, y0), the major and minor axis parameters a, b, and the angle θ between the major axis and the horizontal direction. There are:

[0042]

[0043]

[0044] Furthermore, the above - mentioned step S6 is specifically:

[0045] Determine the magnitude and azimuth of the yaw angle according to the fitted ellipse; the magnitude and phase of the geometric eccentricity; Set the short - axis direction as the gear yaw axis direction, and solve the yaw angle according to the calculated value a of the major axis and the calculated value b of the minor axis It is:

[0046]

[0047] According to the ellipse center parameters (x0, y0), the magnitude e and phase β of the geometric eccentricity can be determined as:

[0048]

[0049] Furthermore, the above - mentioned step S7 is specifically:

[0050] Adjust the gear installation position according to the determined yaw angle and geometric error; Judge whether the identified installation error parameters simultaneously satisfy the following discriminant formula (12); If not, continue to iterate from step S1; On the contrary, take the current adjusted state as the initial machining state of the gear, and the installation error correction ends;

[0051]

[0052] In formula (12), ε is the design tolerance value of the roundness of the measured circle of the gear; ζ is the design tolerance value of the cylindricity of the gear mounting shaft hole.

[0053] The technical solutions provided by the embodiments of the present invention may include the following beneficial effects:

[0054] 1) The present invention adopts a scanning measurement method for detecting gear installation errors. By measuring any complete circumference on the gear to obtain original data, the low-frequency contour scanning data is obtained by using the wavelet decomposition method. Compared with the traditional methods of small arc fitting and inferring the partial tooth profile measurement, it more comprehensively reflects the yaw information of one week of the gear. The measurement result is not affected by the gear tooth surface topography error, and the detection method is simple, without the need for complex detection path planning and equipment installation.

[0055] 2) The present invention uses the machining tolerance of the measured gear as the identification iteration stop condition. This processing method weakens the influence of gear manufacturing errors to the greatest extent on the premise of ensuring the minimization of correcting gear installation errors, and avoids the situations of "precision redundancy" or "precision insufficiency" in measurement.

[0056] 3) The gear installation error of the present invention is directly obtained by solving the center, major and minor axes information of the fitted ellipse, avoiding the multiple calculation errors caused by the mathematical modeling accuracy and method of the traditional method, and making the installation error value more accurate and reliable.

[0057] 4) The present invention can simultaneously analyze and calculate the gear installation yaw and geometric eccentricity errors through one-time data scanning processing, and the realized measurement items are richer than the traditional measurement means; the installation error measurement method of the present invention can be used in all scanning gear processing or detection where there may be gear installation and positioning errors. Since the scanning probe has been widely used, this detection method is very mature and can also be extended for use in expanding the calibration function of gears. Description of the Drawings

[0058] Figure 1 is the execution flow chart of the method of the present invention;

[0059] Figure 2 is the schematic diagram of the detection model of the present invention;

[0060] Figure 3 is the schematic diagram of the basic detection principle of the present invention;

[0061] Figure 4 is the schematic diagram of the principle of generating the coordinates of each measurement point in the polar coordinate system of the present invention;

[0062] Figure 5 is the schematic diagram of ellipse fitting and each parameter in the rectangular coordinate system of the present invention;

[0063] Figure 6Schematic diagram of the gear yaw angle calculation method of the present invention. Detailed implementation manners

[0064] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0065] Please refer to Figure 1 , the present invention provides a technical solution: a method for identifying the installation error of a large gear, including the following steps:

[0066] The first step: Install the gear on the rotary workbench, check the clamping situation of the fixture of the rotary workbench and the gear to be measured. First, use the manual calibration method to ensure the coaxiality of the central axis of the gear to be measured and the central axis of the rotary workbench and the parallelism of the end face of the gear to be measured and the end face of the rotary workbench as much as possible; after the inspection, install a scanning probe on the machine tool. As Figure 2 shown, place the probe at a position on the scannable circumference coaxial with the gear to be measured (it can also be other circumferential positions), is the gear yaw angle (∠LES), QG is the geometric eccentricity of the gear, PQ is the rotation axis of the gear to be measured, and KJ is the rotation axis of the rotary table. Combine the C-axis rotary interpolation movement to scan the complete circumference on the gear to obtain the original data set X c ={x1, x2, x3...x n}, where n is the number of data in the original data set;

[0067] The second step: When the circumference is yawed, as Figure 3 shown, theoretically it will become the ellipse shown by the solid line. The shape difference between the two is reflected on the elliptical plane as Figure 4 shown. According to the scanning measurement method, the actual scanned morphology is an ellipse, and the actual measured value is the difference between the dotted circle and the solid ellipse in the radial direction. To correctly obtain the contour shape information reflecting the scanned circumference of the gear, it is necessary to remove the high-frequency components such as noise, roughness, and waviness in the original data set and leave the low-frequency components reflecting the contour. Therefore, the wavelet decomposition method is used to separate the frequency components and reconstruct the low-frequency components to obtain the low-frequency contour scanning data set X d ={x d1 , x d2 , x d3 ...x dm}, where m is the number of data in the low-frequency contour scanning data set;

[0068] The third step: As Figure 4As shown, the low-frequency contour scan data set X d Determine the angle x of each measurement point in the polar coordinate system at 360° equal divisions according to the time series di-angle , and the calculation formula is:

[0069] x di-angle = i * 360 / m (i = 1 ~ m) (1)

[0070] According to the scanning measurement principle, the scanning probe outputs relative measurement values. Therefore, the radius change amount x of each measurement point in the polar coordinate system is determined by the relative measurement data value di-length , and the calculation formula is:

[0071]

[0072] As Figure 4 shown, the measured radius size of each measurement point in the polar coordinate system is recorded as:

[0073] x di-ρ = R + x di-length (i = 1 ~ m) (3)

[0074] In formula (3), R is the theoretical radius value of the measured circumference;

[0075] Thus, the coordinate sequence Co of the measurement points in the polar coordinate system is obtained as:

[0076] Co = {(x di-ρ , x di-angle ) | i = 1 ~ m} (4)

[0077] Plot the above coordinate set in the polar coordinate system, as Figure 4 shown;

[0078] Step 4: The formula for converting the points in the polar coordinate system to the Cartesian coordinate system is:

[0079]

[0080] In formula (5), X di , Y di are the coordinate values of the measurement points in the Cartesian coordinate system;

[0081] Step 5: Use the least squares fitting method to perform ellipse fitting on the measurement points in the Cartesian coordinate system, as Figure 5 shown. For an ellipse with any center coordinate and offset angle, it can be expressed in the following general form:

[0082] x 2 + Axy + By 2 + Cx + Dy + E = 0 (6)

[0083] In Equation (6), A, B, C, D, and E are parameters of the general form of the elliptic equation.

[0084] Then the least squares elliptic fitting formula is:

[0085]

[0086] In Equation (7), i = 1 to m.

[0087] After obtaining the parameters A, B, C, D, and E of the general form from Equation (7), five parameters of the ellipse are calculated according to the mathematical model of the standard ellipse: the ellipse center parameters (x0, y0), the major and minor axis parameters a, b, and the angle θ between the major axis and the horizontal direction. The geometric meanings of the parameters are as Figure 5 shown, and the formula is:

[0088]

[0089]

[0090] Step 6: Determine the yaw angle size and orientation; the geometric eccentricity size and phase. According to Figure 2 it can be known that when the theoretical geometric eccentricity is QG, due to the gear installation tilt error, the measured eccentricity will be TH. In practice, the gear yaw angle , so it can be considered that QG≈TH = e. As Figure 6 shown, the short axis direction is the gear yaw axis direction. According to the calculated value a of the major axis and the calculated value b of the minor axis, the yaw angle is:

[0091]

[0092] As Figure 5 shown, according to the ellipse center parameters (x0, y0), the geometric eccentricity size e and phase β can be determined as:

[0093]

[0094] Step 7: Adjust the gear installation position according to the determined yaw angle and geometric error;

[0095] Step 8: Determine whether the identified installation error parameters satisfy the following discriminant formula (12). If not, continue to iterate from Step 1; otherwise, take the current adjusted state as the initial measurement or processing state of the gear, and the installation error correction ends.

[0096]

[0097] In Equation (12), ε is the roundness design tolerance value of the measured circle of the gear; ζ is the cylindricity design tolerance value of the gear installation shaft hole.

[0098] During actual measurement, it shall be ensured that there is no interference between the probe and the gear under test and the measuring device during the measurement process, and the measurement data of the sensor is valid.

[0099] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for identifying the installation error of a large gear, characterized in that Including: S1: First, install the probe, check the fixation of the gear to be measured, set the measurement operation parameters to ensure that the probe returns normal values; rotate the rotary table to start the measurement. S2: Then, process the measurement data and separate the frequency components by using the wavelet decomposition method. S3: Plot the processed measurement points in the polar coordinate system. S4: Convert the points in the polar coordinate system to the Cartesian coordinate system. S5: Use the least squares fitting method to perform ellipse fitting on the measurement points in the Cartesian coordinate system. S6: Determine the magnitude and azimuth of the yaw angle, and the magnitude and phase of the geometric eccentricity according to the fitted ellipse. Determine the magnitude and azimuth of the yaw angle according to the fitted ellipse; the magnitude and phase of the geometric eccentricity; set the short-axis direction as the gear yaw axis direction, and solve the yaw angle according to the calculated value a of the long axis and the calculated value b of the short axis It is: According to the ellipse center parameters (x0, y0), the geometric eccentricity magnitude e and phase β can be determined as follows: S7: Adjust the gear installation position according to the determined yaw angle and geometric error, and judge whether the identified installation error parameters meet the requirements; if not, return to step S1 and start iterative execution again; otherwise, take the current adjusted state as the initial machining state of the gear, and the installation error correction is completed.

2. The large gear installation error identification method according to claim 1, characterized in that The specific content of step S1 is: Install the gear on the rotary table and check the clamping condition of the fixture of the rotary table and the gear to be measured. First, use the manual calibration method to ensure as much as possible the coaxiality of the central axis of the gear to be measured and the central axis of the rotary table, and the parallelism between the end face of the gear to be measured and the end face of the rotary table. After the inspection, install a scanning probe on the machine tool, place the probe at any position on the circumference to be scanned, and combine the C-axis rotary interpolation motion to scan any complete circumference with the axis of rotation as the axis on the gear to obtain the original data set X c ={x1, x2, x3...x n}, where n is the number of original data values.

3. The large gear installation error identification method according to claim 2, characterized in that The specific content of step S2 is: Remove the medium and high frequency components such as noise, roughness, and waviness from the original dataset, leaving the low frequency components that reflect the contour; use the wavelet decomposition method to separate the frequency components and reconstruct the low frequency components to obtain the low frequency contour scan dataset X d ={x d1 ,x d2 ,x d3 ...x dm}, where m is the number of low frequency contour scan data values.

4. The large gear installation error identification method according to claim 3, characterized in that The specific content of step S3 is: The low-frequency contour scan data set X d Determine the angle x of each measurement point in the polar coordinate system in 360° equal divisions according to the time series di-angle , and the calculation formula is: x di-angle = i * 360 / m (i = 1 to m) (1) The scanning probe outputs relative measurement values, so the data is processed: the radius change amount x of each measurement point in the polar coordinate system is determined by the relative measurement data value di-length , and the calculation formula is: Then, the measured radius magnitude of each measurement point in the polar coordinate system is denoted as: x di-ρ = R + x di-length (i = 1 to m) (3) In formula (3), R is the theoretical radius value of the measured circumference. Thus, the coordinate sequence Co of all measurement points in the polar coordinate system is obtained as: Co = {(x di-ρ , x di-angle ) | i = 1 to m} (4).

5. The large gear installation error identification method according to claim 4, characterized in that The specific content of step S4 is: Convert the points in the polar coordinate system to the Cartesian coordinate system, and we have: In formula (5), X di , Y di are the coordinate values of the measurement points in the Cartesian coordinate system.

6. The large gear installation error identification method according to claim 5, characterized in that The specific content of step S5 is: Use the least squares fitting method to perform ellipse fitting on the measurement points in the Cartesian coordinate system. For an ellipse with any center coordinate and offset angle, it can be expressed in the following general form: x 2 +Axy + By 2 +Cx + Dy + E = 0 (6) In formula (6), A, B, C, D, and E are the parameters of the general form of the ellipse equation. The least squares ellipse fitting formula is: In formula (7), i = 1 to m. Substitute all the measured points (X di , Y di ) in the Cartesian coordinate system into Equation (7) to obtain the parameters A, B, C, D, and E; calculate the five parameters of the ellipse according to the mathematical model of the standard ellipse: the ellipse center coordinate parameters (x0, y0), the major and minor axis parameters a, b, and the angle θ between the major axis and the horizontal direction, as follows:

7. The method for identifying the installation error of the large gear according to claim 6, characterized in that, The specific content of step S7 is: Adjust the gear installation position according to the determined yaw angle and geometric error; judge whether the identified installation error parameters simultaneously satisfy the following discriminant formula (12); if not, continue iterative execution from step S1; otherwise, take the current adjusted state as the initial machining state of the gear, and the installation error correction is completed. In formula (12), ε is the roundness design tolerance value of the measured circle of the gear; ζ is the cylindricity design tolerance value of the gear installation shaft hole.

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