A spur face gear parameter measurement method and device based on linear laser point cloud

Abstract

The application discloses a kind of straight-tooth face gear parameter measurement method and device based on line laser point cloud, belong to visual detection size measurement technical field, consider the problem of insufficient precision in straight-tooth face gear measurement in traditional measurement method, by building line laser end surface scanning measurement platform and carrying out multi-angle rotating scanning to straight-tooth face gear to obtain original point cloud;Original point cloud fusion splicing processing obtains complete point cloud;Radial projection is formed to single circle continuous annular point cloud to the end surface annular region of complete point cloud;Two-dimensional profile curve is generated by annular point cloud;By two-dimensional profile curve, identify tooth top and tooth root, and calculate the height difference value of both;Based on radial displacement coefficient, locate the chord of circle and calculate its chord tooth height, chord tooth thickness;Parameter is output tooth by tooth, mark abnormal tooth, complete measurement.The application is fused by multi-angle scanning splicing, and neighborhood density constraint preprocessing is carried out, to ensure accurate parameter measurement, realize the parameter output of strict correspondence with drawing inspection item.

Description

Technical Field

[0001] This invention belongs to the field of visual inspection and size measurement technology, specifically relating to a method and device for measuring the parameters of spur gear end face based on line laser point clouds. Background Technology

[0002] Spur gears are key fundamental components in precision transmission systems, widely used in miniature reducers, precision instruments, aerospace components, medical devices, and consumer electronics. They offer advantages such as small size, high transmission efficiency, compact structure, and the ability to achieve orthogonal transmission. In miniature transmission chains, the tooth profile accuracy and dimensional consistency of the spur gears directly determine the overall transmission smoothness, noise level, and service life. Therefore, stringent requirements are placed on batch, high-precision, and automated measurement. However, existing measurement methods struggle to balance accuracy, efficiency, and automation, making it difficult to meet the batch quality inspection needs of these applications.

[0003] The tooth profile of spur gears is distributed on the end face of the part, characterized by small tooth width, close tooth pitch, deep tooth root, and strong reflectivity of the metal material. Key parameters of spur gears, such as the height from tooth tip to tooth root, pitch circle chord tooth height, and pitch circle chord tooth thickness, directly determine the meshing accuracy, transmission smoothness, and service life. Therefore, high-precision, stable, and reliable non-contact measurement of these parameters has significant engineering value.

[0004] In existing technologies, there are three main types of methods for measuring the geometric parameters of spur gears:

[0005] The first method is contact coordinate measuring machine (CMM) measurement. This method obtains three-dimensional coordinates by touching the probe point by point, which has high accuracy, but the point-by-point scanning efficiency is extremely low, making it difficult to meet the requirements of batch inspection. The contact force between the probe and the tiny tooth surface is especially prone to causing local deformation, especially for thin-walled micro end face gears, introducing systematic measurement errors, and thus is not suitable for rapid industrial quality inspection.

[0006] The second method is three-dimensional optical scanning measurement of end-face gears. Research schemes utilizing structured light or optical scanners for overall three-dimensional reconstruction of end-face gears have been published in the literature. This type of scheme is gear reconstruction targeting macroscopic surfaces or general geometry. The measurement objectives are often to obtain the topology of the entire tooth surface, calculate the overall deviation, or compare with a complete CAD model. The output results are often overall point clouds, deviation cloud maps, or overall surface shape indicators such as RMSE, peak deviation, and other comprehensive indicators. Because its output language is biased towards R&D and morphological analysis, it is difficult to directly use for benchmarking and judgment in process quality inspection.

[0007] The third method is line laser 3D scanning measurement, which is non-contact, has high data density, and can acquire complete 3D morphology, making it the mainstream measurement method for precision parts. However, existing literature and patents on line laser gear measurement focus on cylindrical gears and spiral bevel gears, all of which have achieved good measurement results. No dedicated measurement scheme for spur gears has been found. This gap may be due to the fact that signal saturation and data loss caused by strong metallic reflection are particularly prominent under end-face geometry conditions. Furthermore, the annular tooth profile needs to be unfolded along the reference circle to establish a geometric correspondence with inspection items such as pitch circle chordal tooth height and chordal tooth thickness; this processing link has not been addressed in existing line laser gear measurement literature. Therefore, developing a line laser precision measurement method suitable for annular tooth profiles, resistant to strong reflection, and applicable to spur gears has significant practical value. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method and device for measuring the parameters of spur gear end faces based on line laser point clouds. The problem of data loss and flying point interference caused by strong reflections from the metal end face is solved by multi-angle scanning, stitching and fusion, and neighborhood density constraint preprocessing.

[0009] A method for measuring the parameters of a spur gear end face based on line laser point clouds includes the following steps:

[0010] Step 1: Set up a line laser end-face scanning measurement platform;

[0011] Step 2: The line laser end face scanning measurement platform scans the spur gear at multiple preset angles to obtain multiple sets of original point clouds;

[0012] Step 3: Perform fusion and stitching processing on the multiple sets of original point clouds, and preprocess the complete point cloud after fusion and stitching to retain effective points with tooth-shaped patterns;

[0013] Step 4: Extract the radial projection of the annular region on the end face of the complete point cloud to form a single-ring continuous annular point cloud;

[0014] Step 5: The single-ring continuous annular point cloud is transformed into a two-dimensional contour curve through polar coordinate transformation;

[0015] Step 6: Determine the tooth number of each tooth tip of the spur gear according to the circumferential angle on the two-dimensional profile curve, and calculate the difference between the tooth tip and tooth root of each tooth with the same tooth number on the Z-axis coordinate value along the two-dimensional profile curve.

[0016] Step 7: Calculate the tooth thickness width value and the tooth spacing width value corresponding to each tooth number in each Z-axis coordinate value. Determine the Z coordinate of the pitch circle chord by calculating the root mean square (RMS) of the difference between the two. Calculate the tooth height and tooth thickness of the pitch circle chord at the Z coordinate of the pitch circle chord.

[0017] Step 8: Calculate the output parameters for each tooth number, mark abnormal teeth, and complete the measurement.

[0018] Furthermore, the specific implementation process of building the line laser end-face scanning measurement platform described in step 1 is as follows:

[0019] The line laser end face scanning measurement platform includes a line laser profilometer and a precision motion platform. The emission direction of the line laser profilometer is perpendicular to the gear end face, and the perpendicular direction is denoted as the Z-axis. The spur gear under test is fixed on the precision motion platform, and the precision motion platform can drive the gear end face to achieve horizontal linear movement and circumferential angular rotation relative to the line laser profilometer.

[0020] Furthermore, the specific implementation process for obtaining multiple sets of original point clouds in step 2 is as follows:

[0021] The preset angles are 0°, 30° and 60°, and horizontal scanning is performed along the same direction at the preset angles to obtain multiple sets of original point clouds.

[0022] Furthermore, the specific implementation process for obtaining the effective points of the tooth profile in step 3 is as follows:

[0023] Step 3.1: Rotate the original point cloud at 0° around the center of the gear by 60° and align it with the original point cloud at 60°. Then rotate the original point cloud at 30° around the center of the gear in the same direction as the original point cloud at 0° and align it with the original point cloud at 60°. This unifies the point clouds to the same coordinate system and then merges and stitches them together to complete the tooth profile data missing due to reflection, thus obtaining a complete three-dimensional point cloud of the end face around the entire circumference.

[0024] Step 3.2: Use Gaussian filtering to perform spatial scanning of the point cloud to eliminate random scanning noise; combine neighborhood density constraints to eliminate discrete reflective flying points with very few neighborhood points; retain high-density, continuous tooth-shaped effective points.

[0025] Furthermore, the specific implementation process of forming a single-ring continuous annular point cloud in step 4 is as follows:

[0026] Step 4.1: Project the preprocessed 3D point cloud onto the 2D plane of the gear end face, determine the initial value circle center by the median or geometric median of the point cloud coordinates, and determine the reference circle center and the reference circle radius by using least squares circle fitting or algebraic circle fitting combined with residual elimination iteration.

[0027] Step 4.2: Using the center of the reference circle as the origin and the radius of the reference circle as the center, filter the point cloud that falls within the preset radial width range to obtain the tooth profile annular point cloud band;

[0028] Step 4.3: Normalize the radial distance of each point in the tooth profile annular point cloud to the radius of the reference circle, so that each point is mapped onto the circumference of the reference circle, and obtain a single-ring continuous annular point cloud unfolded along the reference circle.

[0029] Furthermore, the specific implementation process of generating the two-dimensional contour curve in step 5 is as follows:

[0030] Step 5.1: Calculate the circumferential angle of each point in the tooth profile annular point cloud relative to the reference circle center, and map the circumferential angle to... interval;

[0031] Step 5.2: Using the circumferential angle or the corresponding normalized arc length as the abscissa and the Z-axis coordinate of the corresponding point as the ordinate, unfold the single-ring point cloud projected radially to the reference circle into a continuous two-dimensional contour curve.

[0032] Furthermore, the calculation method for the difference between the tooth tip and tooth root under the same tooth number in step 6 is as follows:

[0033] Step 6.1: Apply upper and lower envelopes to the two-dimensional contour curves respectively;

[0034] Step 6.2: Detect local maxima in the upper envelope as tooth apex peaks, and detect local minima in the lower envelope as tooth root valleys;

[0035] Step 6.3: Sort the tooth numbers in ascending order according to the circumferential angles corresponding to the tooth apex on the two-dimensional profile curve. The height from the tooth apex to the tooth root is the difference between the Z-axis coordinate height of the tooth apex and the average Z-axis coordinate height of the adjacent tooth root valleys under the same tooth number.

[0036] Furthermore, the calculation method for the tooth height and tooth thickness of the pitch circle chord in step 7 is as follows:

[0037] Step 7.1: The radius of the common pitch circle is calculated from the normal module and number of teeth given in the drawing;

[0038] Step 7.2: Traverse the Z-axis height values ​​of the two-dimensional contour curve, and at each Z-axis height value, count the tooth thickness width value corresponding to each tooth number and the tooth spacing width value of adjacent tooth slots; wherein, the tooth thickness width value is the projection width of the left and right tooth profiles in the circumferential arc length direction at the current Z-axis height value, and the tooth spacing width value is the projection width of the tooth profiles on the same side of adjacent teeth in the circumferential arc length direction.

[0039] Step 7.3: Calculate the root mean square (RMS) of the difference between the tooth thickness width and the tooth width for each tooth number under each Z-axis height value, and search for the Z-axis height coordinate corresponding to the minimum RMS (Z) value, which is used as the common pitch circle Z-axis coordinate of the spur gear.

[0040] Step 7.4: Take the value at the height of the Z-axis coordinate of the common pitch circle, and extract the intersection point of the left and right tooth profiles corresponding to each tooth number at that point; the pitch circle chord tooth height is the difference between the Z-axis coordinate of the corresponding tooth tip and the Z-axis coordinate of the common pitch circle, and the pitch circle chord tooth thickness is the chord length corresponding to the arc length between the intersection points of the left and right tooth profiles at that height.

[0041] Furthermore, the output parameters and abnormal tooth markers mentioned in step 8 include:

[0042] Step 8.1: Calculate the maximum value, minimum value, range, and standard deviation of the height from tooth tip to tooth root, the pitch circle chord tooth height, and the pitch circle chord tooth thickness for each tooth number;

[0043] Step 8.2: According to the drawing requirements, set the tolerance zone for pitch circle chord tooth height and tooth thickness. Compare the above measurement data with the set tolerance zone in sequence. Mark the tooth number corresponding to the measurement value that exceeds the tolerance zone of the drawing as abnormal tooth, and complete the parameter measurement of spur gear.

[0044] A spur gear end face parameter measurement device based on line laser point cloud includes a multi-angle point cloud acquisition and fusion module, a point cloud preprocessing module, an end face projection and reference circle fitting module, a tooth profile annular point cloud extraction module, a polar coordinate contour generation module, a tooth tip peak and tooth root valley identification module, an indexing circle chord parameter calculation module, and an abnormal tooth marking and result output module. When the multi-angle point cloud acquisition and fusion module, point cloud preprocessing module, end face projection and reference circle fitting module, tooth profile annular point cloud extraction module, polar coordinate contour generation module, tooth tip peak and tooth root valley identification module, indexing circle chord parameter calculation module, and abnormal tooth marking and result output module are executed, they implement the steps of the spur gear end face parameter measurement method based on line laser point cloud.

[0045] The beneficial effects of this invention are as follows:

[0046] This invention addresses the issues of data loss and flying point interference caused by strong reflections on metal end faces through multi-angle scanning and splicing fusion and neighborhood density constraint preprocessing. It achieves precise dimensionality reduction from three-dimensional to two-dimensional by point cloud projection, reference circle fitting, tooth profile annular region extraction, and radial projection. It generates continuous two-dimensional contour curves by circumferentially unfolding the annular point cloud, and then identifies the tooth tip and tooth root one by one and calculates the pitch circle chord parameters, achieving parameter output that strictly corresponds to the drawing inspection items. This effectively solves the problems of insufficient accuracy and low efficiency of traditional measurement methods in the measurement of spur gears. It has the advantages of strong anti-reflective interference, good data integrity, and accurate parameter measurement. Attached Figure Description

[0047] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0048] Figure 1 This is an overall flowchart of a method for measuring parameters of spur gears according to the present invention;

[0049] Figure 2 This is a flowchart illustrating the method for measuring parameters of spur gears according to the present invention, which involves dimensionality reduction of a three-dimensional point cloud to generate a two-dimensional profile.

[0050] Figure 3 This is a flowchart illustrating the global search for the Z-axis coordinate of the common pitch circle in a method for measuring parameters of spur gears according to the present invention. Detailed Implementation

[0051] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other, and the described embodiments are only some embodiments of the present invention, not all embodiments.

[0052] like Figure 1 As shown, a method for measuring the parameters of a spur gear includes the following steps:

[0053] Step 1: Set up a line laser end-face scanning measurement platform, specifically as follows:

[0054] Step 1.1 Hardware Composition: A high-precision line laser profilometer, a precision angle turntable, a one-dimensional precision translation stage, and an industrial computer are selected to form an automated measurement platform. The line laser emission direction is perpendicular to the gear end face, which is defined as the height direction (Z-axis), and the gear end face is defined as the horizontal plane (XY plane).

[0055] Step 1.2 Test Workpiece: In this embodiment, a spur gear with a module of 2 mm, 64 teeth, a tooth profile angle of 20 degrees, a helix angle of 0 degrees, a clearance coefficient of 0.25, and a radial displacement coefficient of 0 is preferably selected, with a pitch circle diameter of 128 mm. This specification is only a preferred test sample for this embodiment. The measurement method of this invention is not limited by this size and can be adapted to the detection of various zero-displacement spur gears with different modules and numbers of teeth.

[0056] Step 1.3 Workpiece installation: Fix the gear in the center of the turntable and adjust the coaxiality error to within 5 micrometers;

[0057] Step 1.4 Optical path calibration: Adjust the position of the line laser so that the laser line is horizontal and clearly focused on the end face of the gear, ensuring that the scan covers the entire circumference of the tooth profile area.

[0058] Step 2, multi-angle rotation scanning, point cloud acquisition, and fusion stitching, specifically includes:

[0059] Step 2.1 Scanning Angle Setting: To eliminate data loss caused by reflections from the metal end face, select three scanning angles: 0°, 30°, and 60°.

[0060] Step 2.2 Angle scanning: At three angles of 0°, 30° and 60° respectively, the gear is moved horizontally in the same direction by the translation stage, and the line laser is continuously scanned to collect three sets of original end face point clouds.

[0061] Step 3 involves preprocessing the point cloud to remove noise and reflective specks, retaining only the effective tooth surface point cloud. Specifically:

[0062] Step 3.1 Coordinate Alignment and Fusion: Using the point cloud obtained from the 60° scan as the reference coordinate system, rotate the 0° collected point cloud around the center by 60°, and then rotate the 30° collected point cloud around the center by 30° in the same direction to complete the coordinate alignment; merge the three sets of point clouds, fill in the missing data in the reflective blind area, and obtain a complete 3D point cloud of the end face.

[0063] Step 3.2 Smoothing and noise reduction: Gaussian smoothing is performed on the stitched complete point cloud to weaken the random small noise generated during the scanning process, while preserving the details of the toothed edges;

[0064] Step 3.3 Remove flying points: Based on the density of points in the neighborhood of the point cloud, remove isolated and discrete reflective flying points, and retain only high-density, continuous, tooth-shaped effective point clouds.

[0065] Specifically, the metal tooth surface of spur gears is prone to specular reflection during scanning, and scanning at a single angle can result in localized missing point clouds on the tooth surface. By using multiple sets of scanning angles at fixed intervals of 30°, the reflective blind spots at a single angle can be rotated to non-reflective positions, and then the original end-face point clouds after scanning can be merged and stitched together to complete the missing tooth profile data. Furthermore, with the fixed interval of 30°, if the interval angle is too large, some tooth profile areas will still be in reflective blind spots, resulting in poor point cloud completion. Using more scanning angles further improves point cloud integrity but increases scanning time and reduces measurement efficiency. Scanning angles of 0°, 30°, and 60° are the preferred implementation angles of this invention, balancing point cloud integrity and measurement efficiency. Finally, this invention is not limited to the above three sets of scanning angles; any rotational angle that can achieve the completion of the reflective blind spots of the spur gear is a selectable scanning angle.

[0066] Step 4, as shown in the attached document Figure 2 As shown, 3D point cloud dimensionality reduction processing generates a single-ring continuous ring point cloud:

[0067] Step 4.1 End face projection: The preprocessed 3D point cloud is vertically projected onto the horizontal plane where the end face of the spur gear is located, and the height information is removed to obtain a set of 2D projection points containing only planar coordinates;

[0068] Step 4.2 Reference circle fitting: Iterative fitting calculation is performed on the two-dimensional projection points. First, the initial circle center is determined by the median of the coordinates. Then, the least squares circle fitting or algebraic circle fitting is used to continuously optimize the process and eliminate outliers with excessive deviations. Finally, the accurate end face center position and reference circle radius are determined. In this embodiment, the reference circle radius is consistent with the theoretical pitch circle radius of the gear, and its value is 64 mm.

[0069] Specifically, in this step, the least squares circle fitting and algebraic circle fitting are both conventional algorithms for point cloud planar circle fitting; the residual elimination iteration is a conventional process for robust circle fitting, and the specific steps are as follows: first, calculate the distance residual of each projection point relative to the fitted circle based on the current circle center and radius, set a residual threshold, and eliminate outlier points with residuals greater than the threshold; use the remaining valid points to re-fit the circle, repeat the above process for iteration until the circle center and radius converge and change less than the set threshold, and finally output the reference circle center and reference circle radius. This processing method is used to eliminate workpiece clamping noise and interference points other than the tooth profile, which greatly improves the circle center positioning accuracy.

[0070] Step 4.3 Extraction of the tooth profile annular region: With the reference circle as the center, select an area with a fixed radial width near the radius of the reference circle, filter out the point cloud that falls completely within the annular range, form an annular point cloud band containing only tooth profile features, and eliminate redundant interference points inside and outside the end face.

[0071] Step 4.4 Radial Normalization Mapping: Map each point within the annular point cloud along the line connecting it to the center of the end face onto the circumference of the reference circle, so that all points fall on the same circumference, forming a continuous, non-overlapping, and non-missing single-ring annular point cloud.

[0072] Step 5, as attached Figure 2 As shown, the annular point cloud is unfolded circumferentially to generate a complete two-dimensional contour curve:

[0073] Step 5.1 Calculation of circumferential angle: Calculate the circumferential angle of each point in the single-ring point cloud relative to the center of the end face, and map the angles of all points to a complete circumference range of 0°~360°.

[0074] Step 5.2 Coordinate Transformation and Unfolding: Using the circumferential angle as the abscissa and the original Z-axis coordinate value corresponding to each point as the ordinate, the point cloud distributed in the ring is unfolded and arranged in angular order to form a continuous, complete two-dimensional profile curve that can reflect the undulation of the entire tooth profile. The horizontal axis of this curve is the circumferential position and the vertical axis is the actual Z-axis height of the tooth surface. Subsequent pitch circle height traversal is based entirely on this two-dimensional profile curve.

[0075] Step 5.3 Contour Smoothing and Verification: Slightly smooth the unfolded two-dimensional contour curve to remove local burr interference, verify the continuity of the curve, and ensure that the tooth tip and tooth root features of the 64 teeth are complete and clear.

[0076] Step 6: Identify the tooth tip and root one by one, and calculate the height from the tooth tip to the tooth root:

[0077] Step 6.1 Extraction of upper and lower envelopes: Extract the upper and lower envelopes from the two-dimensional contour curves respectively. The upper envelope corresponds to the height change of the tooth tip throughout the entire circumference, and the lower envelope corresponds to the height change of the tooth root throughout the entire circumference.

[0078] Step 6.2 Location of tooth apex and tooth root valley: Detect the highest local point on the upper envelope to determine the tooth apex of each tooth; detect the lowest local point on the lower envelope to determine the tooth root valley of each tooth.

[0079] Step 6.3 Tooth numbering and allocation: Assign a unique number to each tooth in order of increasing angle of the tooth apex on the circumference, from number 1 to number 64 to complete the numbering of all teeth;

[0080] Step 6.4 Tooth tip height calculation: For each tooth, subtract the average height of the two adjacent root valleys from the height of the tooth tip to obtain the tooth tip to root height.

[0081] Step 7, as attached Figure 3 As shown, based on the two-dimensional profile curve, a global search for the common pitch circle height is performed to calculate the pitch circle chord tooth height and pitch circle chord tooth thickness, specifically as follows:

[0082] Step 7.1 Parameter reference: Based on the gear drawing parameters, the normal module is 2mm, the number of teeth is 64, the theoretical pitch circle radius is 64mm, the gear radial displacement coefficient is 0, and theoretically the tooth thickness and tooth space width are equal at all points on the pitch circle.

[0083] Step 7.2 Traverse the Z-axis height values ​​longitudinally along the two-dimensional profile curve: With a fixed step size of 0.01mm, traverse the entire range of Z-axis height values ​​(from tooth root height to tooth tip height) of the two-dimensional profile curve point by point. At each curve cross-section corresponding to the Z-axis height value, count the single tooth thickness width and the adjacent tooth groove width one by one.

[0084] Step 7.3 Deviation Quantification: Calculate the overall root mean square deviation for all 64 groups of tooth thickness and tooth space width differences under the same Z-axis height value. The larger the deviation value, the farther the current height deviates from the true pitch circle.

[0085] Step 7.4 Determining the height of the Z-axis coordinate of the optimal common pitch circle: Search for the value of the height of the Z-axis coordinate corresponding to the minimum root mean square value. This coordinate is the height of the common pitch circle shared by the entire gear. In this embodiment, the common pitch circle Z = 0.25 mm.

[0086] Step 7.5 Calculation of pitch circle chord tooth height: Pitch circle chord tooth height of a single tooth = Z-axis coordinate of tooth tip - Z-axis coordinate of common pitch circle; Partial measured values: 0.203mm, 0.182mm, 0.220mm, 0.235mm, 0.220mm, 0.205mm, 0.205mm;

[0087] Step 7.6 Calculation of pitch circle chord tooth thickness: At the horizontal intercept of the two-dimensional profile curve Z=0.25mm, the intersection of the left and right tooth profiles of a single tooth is intercepted. The chord length between the two points is the pitch circle chord tooth thickness; some actual measurements: 0.268mm, 0.291mm, 0.316mm, 0.319mm, 0.313mm.

[0088] Step 8, tooth-by-tooth parameter statistics, abnormal tooth identification, and measurement result output, is as follows:

[0089] Step 8.1 Statistical analysis of all tooth parameters: Calculate the average, maximum, minimum, and range of the tooth tip height, pitch circle chord tooth height, and pitch circle chord tooth thickness for each of the 64 teeth. The statistical results in this embodiment are: average tooth tip height 0.450 mm, average pitch circle chord tooth height 0.206 mm, and average pitch circle chord tooth thickness 0.301 mm.

[0090] Step 8.2 Set tolerance threshold: According to the drawing requirements, set the allowable tolerance range for the pitch circle chord tooth height and chord tooth thickness to ±0.02 mm;

[0091] Step 8.3 Abnormal tooth identification and marking: Compare all measurement data with the set tolerance one by one. There are a total of 2 teeth in the entire measured gear whose pitch chord tooth height exceeds the tolerance range. All dimensional parameters of the remaining 62 teeth are within the qualified tolerance range. The two teeth that exceed the tolerance are judged as abnormal teeth.

[0092] Step 8.4 Data Summary and Organization: Summarize the basic parameters of the workpiece, system measurement parameters, tooth-by-tooth measurement data, overall statistical results, and abnormal tooth information.

[0093] Step 8.5 Report Generation and Output: Generate a standardized measurement report, including workpiece information, measurement process, key parameters, full gear data table, abnormal tooth number and deviation description, and export the report in document format. At the same time, save the original point cloud, contour curve and detection mark information to complete the entire parameter measurement process of spur gear end face.

[0094] This embodiment uses a zero-modulation spur gear with a module of 2mm and 64 teeth as the test object. It utilizes multi-view point cloud stitching to eliminate data loss caused by metal surface reflection. Through point cloud preprocessing for noise reduction, reference circle fitting, radial mapping of the annular point cloud, and circumferential unfolding, the scattered three-dimensional points are transformed into a single two-dimensional contour curve that facilitates parameter analysis. By traversing the entire contour in the Z-axis with a step size of 0.01mm and accurately locking the unique common pitch height based on the root mean square criterion of the difference between tooth thickness and tooth groove, the chordal tooth height and chordal tooth thickness of the pitch circle are automatically calculated. Statistical analysis of the 64 teeth across the entire circle shows that most tooth dimensions meet the drawing tolerance requirements, with only two abnormal teeth exhibiting dimensional deviations, enabling accurate differentiation between good and defective parts. Compared to the shortcomings of traditional three-coordinate single-point sampling inspection and ordinary single-view laser measurement which are susceptible to reflection interference, this measurement scheme has a high degree of automation, strong anti-interference ability, and the measurement data closely matches the actual processing state of the workpiece. This verifies the feasibility, measurement accuracy and engineering applicability of the measurement method of this invention, and it can be widely applied to the online quality inspection scenario of end face gear mass production.

[0095] Therefore, the present invention adopts the above-mentioned parameter measurement scheme for spur gear end face based on multi-angle line laser point cloud splicing, which effectively overcomes the problem of data loss caused by the reflection of metal workpieces, realizes full tooth profile non-contact high-precision detection, and has a high degree of automation in the measurement process. It can be widely used in scenarios such as incoming material inspection, process inspection and finished product inspection of end face gears for micro reducers, aerospace parts and precision instruments.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for measuring the parameters of a spur gear end face based on line laser point clouds, characterized in that, The specific steps are as follows: Step 1: Set up a line laser end-face scanning measurement platform; Step 2: The line laser end face scanning measurement platform scans the spur gear at multiple preset angles to obtain multiple sets of original point clouds; Step 3: Perform fusion and stitching processing on the multiple sets of original point clouds, and preprocess the complete point cloud after fusion and stitching to retain effective points with tooth-shaped patterns; Step 4: Extract the radial projection of the annular region on the end face of the complete point cloud to form a single-ring continuous annular point cloud; Step 5: The single-ring continuous annular point cloud is transformed into a two-dimensional contour curve through polar coordinate transformation; Step 6: Determine the tooth number of each tooth tip of the spur gear according to the circumferential angle on the two-dimensional profile curve, and calculate the difference between the tooth tip and tooth root of each tooth with the same tooth number on the Z-axis coordinate value along the two-dimensional profile curve. Step 7: Calculate the tooth thickness width value and the tooth spacing width value corresponding to each tooth number in each Z-axis coordinate value. Determine the Z coordinate of the pitch circle chord by calculating the root mean square (RMS) of the difference between the two. Calculate the tooth height and tooth thickness of the pitch circle chord at the Z coordinate of the pitch circle chord. Step 8: Calculate the output parameters for each tooth number, mark abnormal teeth, and complete the measurement.

2. The method for measuring parameters of spur gear end face based on line laser point cloud as described in claim 1, characterized in that, The specific implementation process of building the line laser end-face scanning measurement platform in step 1 is as follows: The line laser end face scanning measurement platform includes a line laser profilometer and a precision motion platform. The emission direction of the line laser profilometer is perpendicular to the gear end face, and the perpendicular direction is denoted as the Z-axis. The spur gear under test is fixed on the precision motion platform, and the precision motion platform can drive the gear end face to achieve horizontal linear movement and circumferential angular rotation relative to the line laser profilometer.

3. The method for measuring parameters of spur gear end face based on line laser point cloud according to claim 1, characterized in that, The specific implementation process for obtaining multiple sets of original point clouds in step 2 is as follows: The preset angles are 0°, 30° and 60°, and horizontal scanning is performed along the same direction at the preset angles to obtain multiple sets of original point clouds.

4. The method for measuring the parameters of a spur gear end face based on line laser point clouds according to claim 3, characterized in that, The specific implementation process for obtaining the effective points of the tooth profile in step 3 is as follows: Step 3.1: Rotate the original point cloud at 0° around the center of the gear by 60° and align it with the original point cloud at 60°. Then rotate the original point cloud at 30° around the center of the gear in the same direction as the original point cloud at 0° and align it with the original point cloud at 60°. This unifies the point clouds to the same coordinate system and then merges and stitches them together to complete the tooth profile data missing due to reflection, thus obtaining a complete three-dimensional point cloud of the end face. Step 3.2: Use Gaussian filtering to perform spatial scanning of the point cloud to eliminate random scanning noise; combine neighborhood density constraints to eliminate discrete reflective flying points with very few neighborhood points; retain high-density, continuous tooth-shaped effective points.

5. The method for measuring the parameters of a spur gear end face based on line laser point clouds according to claim 4, characterized in that, The specific implementation process for forming a single-ring continuous point cloud in step 4 is as follows: Step 4.1: Project the preprocessed 3D point cloud onto the 2D plane of the gear end face, determine the initial value circle center by the median or geometric median of the point cloud coordinates, and determine the reference circle center and the reference circle radius by using least squares circle fitting or algebraic circle fitting combined with residual elimination iteration. Step 4.2: Using the center of the reference circle as the origin and the radius of the reference circle as the center, filter the point cloud that falls within the preset radial width range to obtain the tooth profile annular point cloud band; Step 4.3: Normalize the radial distance of each point in the tooth profile annular point cloud to the radius of the reference circle, so that each point is mapped onto the circumference of the reference circle, and obtain a single-ring continuous annular point cloud unfolded along the reference circle.

6. The method for measuring parameters of spur gear end face based on line laser point cloud according to claim 5, characterized in that, The specific implementation process of generating the two-dimensional contour curve in step 5 is as follows: Step 5.1: Calculate the circumferential angle of each point in the tooth profile annular point cloud relative to the reference circle center, and map the circumferential angle to the interval [0, 2π); Step 5.2: Using the circumferential angle or the corresponding normalized arc length as the abscissa and the Z-axis coordinate of the corresponding point as the ordinate, unfold the single-ring point cloud projected radially to the reference circle into a continuous two-dimensional contour curve.

7. The method for measuring parameters of spur gear end face based on line laser point cloud according to claim 6, characterized in that, The calculation method for the difference between the tooth tip and tooth root under the same tooth number in step 6 is as follows: Step 6.1: Apply upper and lower envelopes to the two-dimensional contour curves respectively; Step 6.2: Detect local maxima in the upper envelope as tooth apex peaks, and detect local minima in the lower envelope as tooth root valleys; Step 6.3: Sort the tooth numbers in ascending order according to the circumferential angles corresponding to the tooth apex on the two-dimensional profile curve. The height from the tooth apex to the tooth root is the difference between the Z-axis coordinate height of the tooth apex and the average Z-axis coordinate height of the adjacent tooth root valleys under the same tooth number.

8. The method for measuring parameters of spur gear end face based on line laser point cloud according to claim 7, characterized in that, The calculation method for the tooth height and tooth thickness of the pitch circle chord in step 7 is as follows: Step 7.1: The radius of the common pitch circle is calculated from the normal module and number of teeth given in the drawing; Step 7.2: Traverse the Z-axis height values ​​of the two-dimensional contour curve, and at each Z-axis height value, count the tooth thickness width value corresponding to each tooth number and the tooth spacing width value of adjacent tooth slots; wherein, the tooth thickness width value is the projection width of the left and right tooth profiles in the circumferential arc length direction at the current Z-axis height value, and the tooth spacing width value is the projection width of the tooth profiles on the same side of adjacent teeth in the circumferential arc length direction. Step 7.3: Calculate the root mean square (RMS) of the difference between the tooth thickness width and the tooth width for each tooth number under each Z-axis height value, and search for the Z-axis height coordinate corresponding to the minimum RMS (Z) value, which is used as the common pitch circle Z-axis coordinate of the spur gear. Step 7.4: Take the value at the height of the Z-axis coordinate of the common pitch circle, and extract the intersection point of the left and right tooth profiles corresponding to each tooth number at that point; the pitch circle chord tooth height is the difference between the Z-axis coordinate of the corresponding tooth tip and the Z-axis coordinate of the common pitch circle, and the pitch circle chord tooth thickness is the chord length corresponding to the arc length between the intersection points of the left and right tooth profiles at that height.

9. The method for measuring parameters of spur gear end face based on line laser point cloud as described in claim 8, characterized in that, The output parameters and abnormal tooth markers mentioned in step 8 include: Step 8.1: Calculate the maximum value, minimum value, range, and standard deviation of the height from tooth tip to tooth root, the pitch circle chord tooth height, and the pitch circle chord tooth thickness for each tooth number; Step 8.2: According to the drawing requirements, set the tolerance zone for pitch circle chord tooth height and tooth thickness. Compare the above measurement data with the set tolerance zone in sequence. Mark the tooth number corresponding to the measurement value that exceeds the tolerance zone of the drawing as abnormal tooth, and complete the parameter measurement of spur gear.

10. A device for measuring parameters of spur gear end face based on line laser point cloud, characterized in that: The method includes a multi-angle point cloud acquisition and fusion module, a point cloud preprocessing module, an end face projection and reference circle fitting module, a tooth profile annular point cloud extraction module, a polar coordinate contour generation module, a tooth tip peak and tooth root valley identification module, a pitch circle chord parameter calculation module, and an abnormal tooth marking and result output module. When these modules are executed, they implement the steps of the method described in any one of claims 1 to 9.

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