Automobile cylinder body measuring method based on laser displacement sensing technology

Abstract

The invention relates to the technical field of laser measurement, in particular to an automobile cylinder body measurement method based on a laser displacement sensing technology, and the method comprises the steps: carrying out the preliminary laser scanning of the surface of a to-be-measured automobile cylinder body, marking cylinder body holes, obtaining the point cloud data of the cylinder body holes, and determining the interference characterization coefficient of the cylinder body holes, so as to screen characteristic cylinder body holes; the method comprises the following steps of: determining a chamfer form fluctuation coefficient according to a reflected light angle of preliminary laser scanning of a plurality of preset measurement point positions in a characteristic region of a characteristic cylinder body hole so as to judge a chamfer form category of the characteristic cylinder body hole, and selecting an adjusting mode for performing local focusing laser scanning on the characteristic cylinder body hole based on the chamfer form category; the actual chamfer form structure of the cylinder body hole can be rapidly measured, the laser scanning method at the position of the cylinder body hole is adaptively adjusted according to different chamfer form structures, and the measurement precision and the measurement efficiency of the automobile cylinder body are improved.

Description

Technical Field

[0001] The invention relates to the technical field of laser measurement, and in particular to a method for measuring an automobile cylinder body based on laser displacement sensing technology. Background Art

[0002] In the automobile manufacturing industry, automobile cylinder blocks are the core components of engines, and their manufacturing precision has a decisive influence on engine performance. Among them, the quality of cylinder block holes is of paramount importance. It is directly related to the tightness of the fit between the piston and the cylinder wall, and plays a key role in the power output, fuel economy, stability and service life of the engine. In actual production, most cylinder block holes are designed with chamfer structures. The existence of chamfers can, on the one hand, play a guiding role in the assembly process to prevent damage to parts; on the other hand, it can also relieve stress concentration and enhance the overall reliability of the cylinder block. Different cylinder block holes will have different forms of chamfer structures to achieve specific process effects. Laser displacement sensing technology, as an advanced non-contact measurement method, has been widely used in the field of automobile cylinder block measurement. However, different forms of chamfer structures have different reflection characteristics and scattering laws for lasers. Using the same measurement parameters, it is difficult to accurately capture the subtle shape changes and size information of the chamfered parts, which affects the measurement accuracy. Therefore, improving the accuracy of automobile cylinder block measurement is a technical problem that needs to be solved urgently.

[0003] For example, the Chinese patent authorization announcement number is: CN114087989B, which discloses a method and system for measuring the three-dimensional coordinates of the center of the positioning hole of a car cylinder workpiece, wherein the method includes: S10 obtaining a point cloud image of the positioning hole area of ​​the car cylinder workpiece to be measured; S20 performing plane fitting on the point cloud area containing the circular ring in the point cloud image; S30 obtaining the positioning hole circular ring point cloud based on the plane fitting, and extracting the boundary features of the circular ring; S40 performing spatial circle fitting on the extracted circular ring boundary features to obtain the three-dimensional coordinates of the spatial circle, and completing the three-dimensional coordinate measurement of the center of the positioning hole of the car cylinder workpiece.

[0004] The prior art still has the following problems: The prior art does not take into account that the different morphological structures of the cylinder hole chamfer will affect the measurement accuracy of laser detection. The prior art cannot quickly measure the actual chamfer morphological structure of the cylinder hole, and cannot adaptively adjust the laser scanning method at the cylinder hole according to the different chamfer morphological structures, which affects the measurement accuracy and efficiency of the automobile cylinder body. Summary of the invention

[0005] To this end, the present invention provides a method for measuring an automotive cylinder block based on laser displacement sensing technology, which is used to overcome the problems in the prior art that the actual chamfer shape structure of the cylinder block holes cannot be quickly measured, and the laser scanning method at the cylinder block holes cannot be adaptively adjusted according to different chamfer shape structures, affecting the measurement accuracy and measurement efficiency of the automotive cylinder block.

[0006] To achieve the above object, the present invention provides a method for measuring an automotive cylinder block based on laser displacement sensing technology, including: Placing the automotive cylinder block to be measured on a cylinder block bearing platform, performing a preliminary laser scan on the surface of the automotive cylinder block to be measured, marking the cylinder block holes according to the point cloud data obtained from the preliminary laser scan, obtaining the point cloud data at the cylinder block holes to determine the interference characterization coefficient of the cylinder block holes, and screening the characteristic cylinder block holes based on the comparison of the interference characterization coefficients; Among them, the interference characterization coefficient is determined according to the depth parameter and the aperture parameter of the cylinder block hole; Obtaining the reflection light angles of several preset measurement points at the characteristic area of the characteristic cylinder block hole through preliminary laser scans, and determining the chamfer shape fluctuation coefficient according to the comparison of the reflection light angles to determine the chamfer shape category of the characteristic cylinder block hole; Determining the local focused laser scanning method for the characteristic cylinder block hole based on the chamfer shape category; The local focused laser scanning method includes obtaining the reflection light angles of the preset measurement points on the characteristic area of the characteristic cylinder block hole to determine the chamfer tendency factor, and adjusting the scanning spot of the local focused laser scan; Or determining the reflection fluctuation factor based on the reflection light angles of each preset measurement point on the characteristic area at different laser scanning angles to select the laser scanning angle of the local focused laser scan.

[0007] Further, the method for determining the interference characterization coefficient of the cylinder block hole is to determine the depth parameter and the aperture parameter according to the point cloud data at the cylinder block hole, calculate the ratio of the depth parameter to the aperture parameter, and determine the ratio as the interference characterization coefficient of the cylinder block hole.

[0008] Further, screening the characteristic cylinder block holes includes, If the interference characterization coefficient of the cylinder block hole meets the interference determination condition, then the cylinder block hole is screened as a characteristic cylinder block hole; Among them, the interference determination condition is that the interference characterization coefficient exceeds a preset interference characterization reference value.

[0009] Further, the method for determining the chamfer shape fluctuation coefficient is to calculate the angular difference between the reflection light angle of any preset measurement point at the characteristic area of the characteristic cylinder block hole and the reflection light angles of the remaining preset measurement points, and determine the variance of the angular difference as the chamfer shape fluctuation coefficient of the characteristic cylinder block hole.

[0010] Further, the process of determining the chamfer shape category of the characteristic cylinder block hole includes If the chamfer shape fluctuation coefficient of the characteristic cylinder block hole meets the first chamfer shape determination condition, it is determined that the chamfer shape category of the characteristic cylinder block hole is the first chamfer shape category; If the chamfer shape fluctuation coefficient of the characteristic cylinder block hole does not meet the first chamfer shape determination condition, it is determined that the chamfer shape category of the characteristic cylinder block hole is the second chamfer shape category; Wherein, the first chamfer shape determination condition is that the chamfer shape fluctuation coefficient exceeds a preset chamfer shape fluctuation reference value.

[0011] Further, the method of selecting the adjustment method for local focused laser scanning of the characteristic cylinder block hole includes If the chamfer shape category is the first chamfer shape category, obtain the reflection light angle of the preset measurement point on the characteristic region of the characteristic cylinder block hole along the diameter direction of the cylinder block hole, determine the chamfer tendency factor according to the reflection light angles of adjacent preset measurement points, and adjust the scanning spot diameter of the local focused laser scanning according to the chamfer tendency factor; If the chamfer shape category is the second chamfer shape category, determine the reflection fluctuation factor based on the reflection light angles of each preset measurement point on the characteristic region of the characteristic cylinder block hole at different laser scanning angles, so as to select the laser scanning angle of the local focused laser scanning.

[0012] Further, the process of determining the chamfer tendency factor includes Obtain the reflection light angles of adjacent preset measurement points on the characteristic region of the characteristic cylinder block hole along the diameter direction of the cylinder block hole; Calculate the difference between the reflection light angles of adjacent preset measurement points, and determine the difference as the chamfer tendency factor of the characteristic measurement point.

[0013] Wherein, the characteristic measurement point is the preset measurement point closer to the center position of the cylinder block hole among two adjacent preset measurement points.

[0014] Further, the scanning spot diameter is negatively correlated with the chamfer tendency factor.

[0015] Further, the process of determining the reflection fluctuation factor includes Perform local focused laser scanning on the preset measurement points on the characteristic region of the characteristic cylinder block hole at different laser scanning angles, where the laser scanning angles increase sequentially with a preset interval angle change amount, obtain the difference between the reflection light angles at adjacent scanning angles, and determine the ratio of the difference to the interval angle change amount as the reflection fluctuation factor of the preset measurement point at the current laser scanning angle.

[0016] Furthermore, the process of selecting the laser scanning angle for local focused laser scanning includes If the reflection fluctuation factors of each preset measurement point on the characteristic region of the characteristic cylinder hole meet the scanning conditions, stop increasing the laser scanning angle, and select the current laser scanning angle as the laser scanning angle for local focused laser scanning; Among them, the scanning conditions are that the reflection fluctuation factors of each preset measurement point do not exceed a preset reflection fluctuation threshold, and the variance of the reflection fluctuation factors does not exceed a preset variance threshold.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows. The present invention preliminarily laser scans the surface of the automobile cylinder block to be measured to mark the cylinder holes, obtains the point cloud data at the cylinder holes to determine the interference characterization coefficient of the cylinder holes to screen the characteristic cylinder holes, determines the chamfer shape fluctuation coefficient based on the reflection light angles of several preset measurement points at the characteristic region of the characteristic cylinder holes to determine the chamfer shape category of the characteristic cylinder holes, and selects the adjustment method for local focused laser scanning of the characteristic cylinder holes based on the chamfer shape category. Furthermore, it realizes the rapid measurement of the actual chamfer shape structure of the cylinder holes, adaptively adjusts the laser scanning method at the cylinder holes according to different chamfer shape structures, and improves the measurement accuracy and measurement efficiency of the automobile cylinder block.

[0018] In particular, the present invention screens the characteristic cylinder holes through the comparison of the interference characterization coefficients. It can be understood that the interference characterization coefficient can characterize whether there is light interference at the cylinder holes during laser scanning. During the measurement process of the automobile cylinder block, measurement resources such as measurement time and equipment usage duration are limited. By screening the characteristic cylinder holes through the interference characterization coefficient, more measurement resources can be concentrated and allocated to these key parts, which can not only ensure the accurate measurement of the key cylinder holes that may affect the product quality, but also improve the overall measurement efficiency and make the measurement work more efficient and reasonable. The present invention screens the characteristic cylinder holes according to the comparison of the ratio of the calculated depth parameter to the aperture parameter. Furthermore, it realizes the screening of the characteristic cylinder holes and improves the measurement accuracy and measurement efficiency of the automobile cylinder block.

[0019] In particular, the present invention determines the chamfer form fluctuation coefficient by comparing the reflection light angles to judge the chamfer form category of the characteristic cylinder hole. It can be understood that chamfer structures of different forms have different reflection characteristics for laser light, and the comparison of the reflection light angles can characterize the chamfer form of the characteristic cylinder hole. By clarifying the chamfer form category of the characteristic cylinder hole, an efficient laser measurement method can be formulated separately for different chamfer form categories, enabling the measurement system to better adapt to the chamfer form changes and adjust to the optimal measurement state, ensuring that the measurement task can be stably and reliably completed under different chamfer form categories. The present invention determines the chamfer form category of the characteristic cylinder hole through the chamfer form fluctuation coefficient, and further realizes the rapid measurement of the actual chamfer form structure of the cylinder hole, improving the measurement accuracy and efficiency of the automotive cylinder block.

[0020] In particular, under the condition of the first chamfer form category, the present invention determines the chamfer inclination factor according to the reflection light angles of adjacent preset measurement points to adjust the scanning spot diameter of the local focused laser scanning. It can be understood that the first chamfer form category means that the chamfer of the characteristic cylinder hole is in an arc shape, and the slope change at different positions of the chamfer will cause different reflection light angles. By obtaining the reflection light angles of the preset measurement points along the diameter direction of the cylinder hole, the change trend of the arc chamfer can be accurately analyzed. Adjusting the scanning spot according to the chamfer inclination factor determined by the reflection light angles of adjacent points can make the laser scanning more conform to the actual shape of the arc chamfer, thereby more accurately measuring the contour dimensions and shape of the cylinder hole, reducing measurement errors, and improving measurement accuracy. Different arc chamfers have different curvatures and inclination degrees, that is, different chamfer inclinations. By calculating the chamfer inclination factor, the unique chamfer characteristics of each characteristic cylinder hole can be clarified. Adjusting the scanning spot according to these specific characteristics can realize the adaptive adjustment of the local focused laser scanning, making the measurement more targeted and better adapting to the measurement requirements of various different-shaped arc chamfers. Further, the rapid measurement of the actual chamfer form structure of the cylinder hole is realized, and the laser scanning method at the cylinder hole is adaptively adjusted according to different chamfer form structures, improving the measurement accuracy and efficiency of the automotive cylinder block.

[0021] In particular, under the condition of the second chamfer shape category, the present invention determines the reflection fluctuation factor based on the reflection light angles of each preset measurement point on the feature area of the feature cylinder hole at different laser scanning angles, so as to select the laser scanning angle for local focused laser scanning. It can be understood that the second chamfer shape category means that the chamfer of the feature cylinder hole is a linear chamfer. The surface of the linear chamfer is relatively flat, but there will be slight angular changes or unevenness at different positions. By analyzing the reflection light angles of each preset measurement point on the feature area at different laser scanning angles to determine the reflection fluctuation factor, these slight changes can be accurately captured. Only when the reflection fluctuation factors of each preset measurement point meet the scanning conditions, that is, each reflection fluctuation factor does not exceed the preset reflection fluctuation threshold, and the variance of the reflection fluctuation factors does not exceed the preset variance threshold, the current laser scanning angle is selected as the scanning angle for local focused laser scanning to ensure that the laser scanning angle matches the actual shape of the linear chamfer, so that the measurement result can more accurately reflect the true situation of the cylinder hole. Increase the laser scanning angle in sequence with a preset interval angle change amount, and judge whether to stop increasing the angle according to the reflection fluctuation factor, so as to quickly lock the most suitable laser scanning angle for the current linear chamfer measurement, optimize the entire scanning process. Furthermore, it realizes the rapid measurement of the actual chamfer shape structure of the cylinder hole, adaptively adjusts the laser scanning method at the cylinder hole according to different chamfer shape structures, and improves the measurement accuracy and measurement efficiency of the automotive cylinder block. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a step diagram of the method for measuring an automotive cylinder block based on the laser displacement sensing technology according to an embodiment of the present invention; Figure 2 It is a logical flow chart for screening the feature cylinder hole according to an embodiment of the present invention; Figure 3 It is a logical flow chart for determining the chamfer shape category of the feature cylinder hole according to an embodiment of the present invention; Figure 4 It is a logical flow chart for selecting the adjustment method for local focused laser scanning of the feature cylinder hole according to an embodiment of the present invention; Figure 5 It is a top view schematic diagram of the feature cylinder hole according to an embodiment of the present invention; In the figure: 1. Feature cylinder hole; 2. Feature area; 3. Cylinder hole diameter; 4. Preset measurement points along the cylinder hole diameter direction. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] In order to make the objectives and advantages of the present invention clearer and more understandable, the present invention will be further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0024] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principle of the present invention and do not limit the protection scope of the present invention.

[0025] It should be noted that in the description of the present invention, the terms indicating the direction or positional relationship such as "upper", "lower", "inner", "outer", etc. are based on the direction or positional relationship shown in the drawings. This is only for convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of the present invention.

[0026] Please refer to Figure 1 as shown, which is a step diagram of the method for measuring an automobile cylinder block based on laser displacement sensing technology according to an embodiment of the present invention. The method for measuring an automobile cylinder block based on laser displacement sensing technology of the present invention includes: Step S100, place the automobile cylinder block to be measured on the cylinder block bearing platform, perform a preliminary laser scan on the surface of the automobile cylinder block to be measured, and mark the cylinder block holes according to the point cloud data obtained from the preliminary laser scan; Specifically, the laser displacement sensing device emits a laser beam and receives the laser signal reflected from the surface of the cylinder block. According to the principles such as the flight time and phase difference of the laser, the three-dimensional coordinate information of each preset measurement point is calculated, so as to obtain the point cloud data of the cylinder block surface. The point cloud data is preprocessed such as noise removal and data registration. According to the geometric features and clustering analysis results extracted from the preprocessed point cloud data, the position and range of the cylinder block holes in the point cloud data are determined. The method of image processing or computer graphics is used to extract and mark the boundary of the identified cylinder block hole point cloud area, which will not be elaborated here.

[0027] Step S200, obtain the point cloud data at the cylinder block holes to determine the interference characterization coefficient of the cylinder block holes, and screen the characteristic cylinder block holes based on the comparison of the interference characterization coefficients; Among them, the interference characterization coefficient is determined according to the depth parameter and aperture parameter of the cylinder block hole; Specifically, the depth parameter of the cylinder block hole can be obtained by establishing an association relationship between the laser scan coordinate system and the actual coordinate system of the cylinder block, so as to obtain the depth parameter of the cylinder block hole according to the coordinate values of the point cloud data. The aperture parameter of the cylinder block hole can be obtained by extracting the contour point cloud of the cylinder block hole and using the ellipse fitting algorithm. Taking the major axis length, minor axis length, major axis inclination angle and ellipse center position of the ellipse as evaluation indexes, when the ellipse fitting points are distributed on the complete ellipse contour, the calculation method of the orthogonal distance contact points in the geometric fitting algorithm is optimized to obtain the aperture parameter, which will not be elaborated here.

[0028] Step S300: Obtain the reflection light angles at several preset measurement points in the feature region of the feature cylinder hole, determine the chamfer shape fluctuation coefficient according to the comparison of the reflection light angles, and determine the chamfer shape category of the feature cylinder hole; Specifically, the feature region of the feature cylinder hole is the chamfer region of the feature cylinder hole. The edge point cloud data can be extracted, the geometric features in its local neighborhood can be analyzed, the normal vectors of the neighborhood point clouds of several edge points of the feature cylinder hole can be calculated, and the chamfer region can be preliminarily determined according to the change of the normal vectors, so as to determine the feature region of the feature cylinder hole, which will not be elaborated here.

[0029] Specifically, the preset measurement points can be set by those skilled in the art according to the measurement experience of several cylinder holes of the same type. Preferably, for a circular feature cylinder hole, the circumference can be equally divided into 12 parts, and a measurement point can be set every 30°, and a measurement point can be set every 1 mm along the axial direction of the cylinder hole.

[0030] Step S400: Determine the local focused laser scanning method for the feature cylinder hole based on the chamfer shape category; The local focused laser scanning method includes obtaining the reflection light angles at the preset measurement points on the feature region of the feature cylinder hole to determine the chamfer tendency factor, and adjusting the scanning spot of the local focused laser scanning; Or determine the reflection fluctuation factor based on the reflection light angles of each preset measurement point on the feature region at different laser scanning angles, so as to select the laser scanning angle of the local focused laser scanning.

[0031] Specifically, the scanning spot is the spot formed when the laser beam irradiates the object surface during the laser scanning process, and the laser scanning angle is the incident angle of the laser beam relative to the surface of the feature cylinder hole.

[0032] Specifically, the method for determining the interference characterization coefficient of the cylinder hole is to determine the depth parameter and the aperture parameter according to the point cloud data at the cylinder hole, calculate the ratio of the depth parameter to the aperture parameter, and determine the ratio as the interference characterization coefficient of the cylinder hole.

[0033] Specifically, please refer to Figure 2 As shown, it is the logical flowchart for screening the feature cylinder hole in the embodiment of the present invention. Screening the feature cylinder hole includes, If the interference characterization coefficient of the cylinder hole meets the interference determination condition, then the cylinder hole is screened as a feature cylinder hole; If the interference characterization coefficient of the cylinder hole does not meet the interference determination condition, then the cylinder hole is not screened; Among them, the interference determination condition is that the interference characterization coefficient exceeds the preset interference characterization reference value.

[0034] Specifically, the preset interference characterization reference value is the product of the average value of the interference characterization coefficient and the interference characterization factor. The interference characterization factor can be set by those skilled in the art according to the accuracy requirements of the measurement of the automotive cylinder block. The higher the accuracy requirements, the smaller the interference characterization factor. The value range of the interference characterization factor can be [0.2, 0.4]. Preferably, the interference characterization factor can be 0.3.

[0035] Specifically, the present invention screens the characteristic cylinder block holes through the comparison of the interference characterization coefficients. It can be understood that the interference characterization coefficient can characterize whether there is light interference in the cylinder block holes during laser scanning. During the measurement process of the automotive cylinder block, measurement resources such as measurement time and equipment usage duration are limited. By screening the characteristic cylinder block holes through the interference characterization coefficients, more measurement resources can be concentrated and allocated to these key parts, which can not only ensure the accurate measurement of the key cylinder block holes that may affect the product quality, but also improve the overall measurement efficiency, making the measurement work more efficient and reasonable. The present invention screens the characteristic cylinder block holes according to the comparison of the ratio of the calculated depth parameter to the aperture parameter. Furthermore, the screening of the characteristic cylinder block holes is realized, and the measurement accuracy and measurement efficiency of the automotive cylinder block are improved.

[0036] Specifically, it can be understood that the larger the interference characterization coefficient, the larger the ratio of the depth parameter to the aperture parameter of the cylinder block hole. For the cylinder block holes with a larger ratio, the reflection and scattering of light in the hole are more complex, which is likely to interfere with the laser measurement, resulting in an increase in measurement error and being more likely to affect the subsequent measurement of the chamfer of the cylinder block hole. By screening out these characteristic cylinder block holes, targeted measures can be taken, thereby improving the measurement accuracy of the chamfers of these cylinder block holes and ensuring that the final measurement results can truly reflect the actual size and shape of the automotive cylinder block. Furthermore, the screening of the characteristic cylinder block holes is realized, and the measurement accuracy and measurement efficiency of the automotive cylinder block are improved.

[0037] Specifically, the method for determining the chamfer shape fluctuation coefficient is to calculate the angular difference between the reflection light angles of any preset measurement point in the characteristic area of the characteristic cylinder block hole and the reflection light angles of the remaining preset measurement points, and determine the variance of the angular difference as the chamfer shape fluctuation coefficient of the characteristic cylinder block hole.

[0038] Specifically, the reflection light angle is the angle between the reflected light and a specific reference direction after the laser beam irradiates a preset measurement point in the characteristic area of the characteristic cylinder block hole. The specific reference direction can be the direction perpendicular to the plane where the cylinder block hole is located, and it can be obtained by using the angle sensor in the laser displacement sensing device, which will not be elaborated here.

[0039] Specifically, please refer to Figure 3As shown, it is a logic flowchart for determining the chamfer shape category of the feature cylinder block holes in the embodiments of the present invention. The process of determining the chamfer shape category of the feature cylinder block holes includes: If the chamfer shape fluctuation coefficient of the feature cylinder block hole meets the first chamfer shape determination condition, it is determined that the chamfer shape category of the feature cylinder block hole is the first chamfer shape category; If the chamfer shape fluctuation coefficient of the feature cylinder block hole does not meet the first chamfer shape determination condition, it is determined that the chamfer shape category of the feature cylinder block hole is the second chamfer shape category; Among them, the first chamfer shape determination condition is that the chamfer shape fluctuation coefficient exceeds a preset chamfer shape fluctuation reference value.

[0040] Specifically, the preset chamfer shape fluctuation reference value can be set by those skilled in the art according to the accuracy requirements of automobile cylinder block measurement. The higher the accuracy requirement, the smaller the preset chamfer shape fluctuation reference value. The value range of the chamfer shape fluctuation reference value can be [0.3, 0.8]. Preferably, the chamfer shape fluctuation reference value can be 0.5.

[0041] Specifically, the present invention determines the chamfer shape fluctuation coefficient through the comparison of the reflected light angles to determine the chamfer shape category of the feature cylinder block holes. It can be understood that chamfer structures of different shapes have different laser reflection characteristics. The comparison of the reflected light angles can characterize the chamfer shape of the feature cylinder block holes. By clarifying the chamfer shape category of the feature cylinder block holes, efficient laser measurement methods can be formulated separately for different chamfer shape categories, enabling the measurement system to better adapt to chamfer shape changes, adjust to the best measurement state, and ensure stable and reliable completion of the measurement task under different chamfer shape categories. The present invention determines the chamfer shape category of the feature cylinder block holes through the chamfer shape fluctuation coefficient, and thus, realizes the rapid measurement of the actual chamfer shape structure of the cylinder block holes, improving the measurement accuracy and measurement efficiency of the automobile cylinder block.

[0042] Specifically, it can be understood that there are differences in geometric shapes between linear chamfers and arc chamfers, resulting in different characteristics of the laser reflected light angles. The change of the reflected light angle of the linear chamfer is relatively regular, and the angle difference at different measurement points is small, so the variance of the angle difference is also small. While the change of the reflected light angle of the arc chamfer is more complex, the angle difference at different points is large, and the variance is also large. By calculating the chamfer shape fluctuation coefficient, these differences can be accurately captured, thereby effectively distinguishing linear chamfers and arc chamfers. Thus, the rapid measurement of the actual chamfer shape structure of the cylinder block holes is realized, and the measurement accuracy and measurement efficiency of the automobile cylinder block are improved.

[0043] Specifically, please refer to Figure 4As shown, it is a logic flowchart for selecting an adjustment method for local focused laser scanning of the feature cylinder hole in an embodiment of the present invention. The method for selecting the adjustment method for local focused laser scanning of the feature cylinder hole includes: If the chamfer form category is the first chamfer form category, obtain the reflection light angle of the preset measurement points along the diameter direction of the feature cylinder hole on the feature area of the feature cylinder hole, determine the chamfer tendency factor according to the reflection light angles of adjacent preset measurement points, and adjust the scanning spot diameter of the local focused laser scanning according to the chamfer tendency factor. Specifically, under the condition of the first chamfer form category, the present invention determines the chamfer tendency factor according to the reflection light angles of adjacent preset measurement points to adjust the scanning spot diameter of the local focused laser scanning. It can be understood that the first chamfer form category means that the chamfer of the feature cylinder hole is an arc shape, and the slope change at different positions of the chamfer will cause different reflection light angles. Obtaining the reflection light angles of the preset measurement points along the diameter direction of the cylinder hole can accurately analyze the change trend of the arc chamfer. Adjusting the scanning spot according to the chamfer tendency factor determined by the reflection light angles of adjacent points can make the laser scanning more conform to the actual shape of the arc chamfer, thereby more accurately measuring the contour dimensions and shape of the cylinder hole, reducing measurement errors, and improving measurement accuracy. Different arc chamfers have different curvatures and inclination degrees, that is, different chamfer tendencies. By calculating the chamfer tendency factor, the unique chamfer characteristics of each feature cylinder hole can be clarified. Adjusting the scanning spot according to these specific characteristics can achieve the adaptive adjustment of the local focused laser scanning, make the measurement more targeted, and better adapt to the measurement requirements of various arc chamfer shapes of different shapes. Furthermore, it realizes the rapid measurement of the actual chamfer form structure of the cylinder hole, adaptively adjusts the laser scanning method at the cylinder hole according to different chamfer form structures, improves the measurement accuracy and measurement efficiency of the automotive cylinder block.

[0044] If the chamfer form category is the second chamfer form category, determine the reflection fluctuation factor based on the reflection light angles of each preset measurement point on the feature area of the feature cylinder hole at different laser scanning angles, so as to select the laser scanning angle of the local focused laser scanning.

[0045] Specifically, under the condition of the second chamfer form category, the present invention determines the reflection fluctuation factor based on the reflection light angles of each preset measurement point on the feature region of the feature cylinder hole at different laser scanning angles, so as to select the laser scanning angle for local focused laser scanning. It can be understood that the second chamfer form category means that the chamfer of the feature cylinder hole is a linear chamfer. The surface of the linear chamfer is relatively flat, but there will be slight angle changes or unevenness at different positions. By analyzing the reflection light angles of each preset measurement point on the feature region at different laser scanning angles, the reflection fluctuation factor is determined, and these slight changes can be accurately captured. Only when the reflection fluctuation factors of each preset measurement point meet the scanning conditions, that is, each reflection fluctuation factor does not exceed the preset reflection fluctuation threshold, and the variance of the reflection fluctuation factors does not exceed the preset variance threshold, the current laser scanning angle is selected as the scanning angle for local focused laser scanning, ensuring that the laser scanning angle matches the actual form of the linear chamfer, so that the measurement result can more accurately reflect the true situation of the cylinder hole. The laser scanning angle is increased in sequence by a preset interval angle change amount, and it is judged whether to stop increasing the angle according to the reflection fluctuation factor, so that the laser scanning angle most suitable for the current linear chamfer measurement can be quickly locked, optimizing the entire scanning process. Furthermore, the actual chamfer form structure of the cylinder hole is quickly measured, and the laser scanning method at the cylinder hole is adaptively adjusted according to different chamfer form structures, improving the measurement accuracy and measurement efficiency of the automotive cylinder block.

[0046] Specifically, please refer to Figure 5 shown, which is a top view schematic diagram of the feature cylinder hole of the embodiment of the present invention. The process of determining the chamfer inclination factor includes obtaining the reflection light angles of adjacent preset measurement points on the feature region of the feature cylinder hole along the diameter direction of the cylinder hole; calculating the difference between the reflection light angles of adjacent preset measurement points, and determining the difference as the chamfer inclination factor of the feature measurement point.

[0047] Among them, the feature measurement point is the preset measurement point close to the center position of the cylinder hole among two adjacent preset measurement points.

[0048] Exemplarily, a specific embodiment of determining the chamfering tendency factor of the characteristic measurement points is given here. The reflection light angles of 5 preset measurement points along the diameter direction of the characteristic cylinder hole in the characteristic region of the characteristic cylinder hole are obtained. The preset measurement points from the one close to the center position of the cylinder hole to the one far from the center position of the cylinder hole are D1, D2, D3, D4, and D5 respectively. The reflection light angle of D1 is 40°, the reflection light angle of D2 is 42°, the reflection light angle of D3 is 45°, the reflection light angle of D4 is 48°, and the reflection light angle of D5 is 50°. The differences in the reflection light angles of adjacent preset measurement points are as follows: the difference between D1 and D2 is 2°, the difference between D2 and D3 is 3°, the difference between D3 and D4 is 3°, and the difference between D4 and D5 is 2°. Therefore, the chamfering tendency factor of D1 is 2°, the chamfering tendency factor of D2 is 3°, the chamfering tendency factor of D3 is 3°, and the chamfering tendency factor of D4 is 2°.

[0049] Specifically, the scanning spot diameter is negatively correlated with the chamfering tendency factor.

[0050] Specifically, it can be understood that when the laser irradiates the arc chamfer surface, since the normal direction of the arc surface continuously changes along the contour, according to the law of reflection of light, the reflection light angle will also change continuously accordingly. Preset measurement points are set along the diameter direction in the characteristic region of the cylinder hole. The reflection light angles at these points can reflect the inclination degree and curvature change of the arc chamfer at different positions. The difference in the reflection light angles of adjacent preset measurement points can reflect the slope change situation of the arc chamfer between these two points. If the angle difference is large, the inclination degree of the chamfer changes rapidly in this interval and the curvature is large. For the arc chamfer region with a large curvature, the scanning spot can be adjusted to be smaller to capture the details of the chamfer more precisely. For the arc chamfer region with a small curvature, the scanning spot can be increased to improve the measurement efficiency while ensuring the measurement accuracy. In an adaptive spot adjustment method, the laser scanning can achieve the best measurement effect at different positions of the arc chamfer, ensuring accurate and detailed information of the characteristic region of the cylinder hole is obtained, and avoiding problems such as information loss or low measurement efficiency caused by too large or too small spots, thereby improving the accuracy and reliability of the entire measurement process.

[0051] Specifically, the process of determining the reflection fluctuation factor includes Performing local focused laser scanning on the preset measurement points in the characteristic region of the characteristic cylinder hole at different laser scanning angles. The laser scanning angles increase successively with a preset interval angle change amount. The difference in the reflection light angles at adjacent scanning angles is obtained, and the ratio of the difference to the interval angle change amount is determined as the reflection fluctuation factor of the preset measurement point at the current laser scanning angle.

[0052] Specifically, the preset interval angle change amount can be set by those skilled in the art according to the accuracy requirements of automobile cylinder block measurement. The higher the accuracy requirement, the smaller the interval angle change amount. The value range of the interval angle change amount can be [3, 8], and the interval unit is °. Preferably, the interval angle change amount can be 5°.

[0053] Exemplarily, a specific embodiment for determining the reflection fluctuation factor is given here. The interval angle change amount is preset to 5°, and the initial laser scanning angle is 40 degrees. It increases sequentially with an interval angle change amount of 5°. The laser scanning angles are 40°, 45°, and 50° in sequence. The differences in the reflection light angles of any preset measurement point at adjacent scanning angles are obtained as 3° and 2° respectively. The ratios of the differences to the interval angle change amount are 0.6 and 0.4 respectively. Therefore, 0.6 is determined as the reflection fluctuation factor of this measurement point when the laser scanning angle is 45°, and 0.4 is determined as the reflection fluctuation factor of this measurement point when the laser scanning angle is 50°.

[0054] Specifically, the process of selecting the laser scanning angle for local focused laser scanning includes, If the reflection fluctuation factors of each preset measurement point on the characteristic region of the characteristic cylinder hole meet the scanning conditions, stop increasing the laser scanning angle, and select the current laser scanning angle as the laser scanning angle for local focused laser scanning; If the reflection fluctuation factors of each preset measurement point on the characteristic region of the characteristic cylinder hole do not meet the scanning conditions, increase the laser scanning angle; Among them, the scanning conditions are that the reflection fluctuation factors of each preset measurement point do not exceed the preset reflection fluctuation threshold, and the variance of the reflection fluctuation factors does not exceed the preset variance threshold.

[0055] Specifically, the preset reflection fluctuation threshold can be set by those skilled in the art according to the measurement experience of several cylinder holes of the same type. The value range of the reflection fluctuation threshold can be [0.5, 2]. Preferably, the reflection fluctuation threshold can be 1.

[0056] Specifically, the preset variance threshold can be set by those skilled in the art according to the accuracy requirements of automobile cylinder block measurement. The higher the accuracy requirement, the smaller the variance threshold. The value range of the variance threshold can be [0.5, 1]. Preferably, the variance threshold can be 0.8.

[0057] Specifically, it can be understood that the laser scanning angle is sequentially increased by a preset interval angle change amount, and the difference in the reflected light angle at adjacent scanning angles is calculated. The difference reflects the change rate of the reflected light angle during the angle change process. By comparing this difference with the interval angle change amount, the obtained reflection fluctuation factor can quantify the sensitivity of the reflected light angle to the change in the laser scanning angle at each preset measurement point. The surface of the linear chamfer is relatively regular, and the change in the reflected light angle at each point is relatively stable and small. When the reflection fluctuation factors at each preset measurement point do not exceed the reflection fluctuation threshold and their variance does not exceed the variance threshold, the laser scanning angle at this time makes the change in the reflected light angle within a reasonable range, that is, the laser scanning angle and the actual shape of the linear chamfer achieve a good match. Furthermore, the actual chamfer shape structure of the cylinder block hole is measured quickly, and the laser scanning method at the cylinder block hole is adaptively adjusted according to different chamfer shape structures, improving the measurement accuracy and efficiency of the automotive cylinder block.

[0058] Exemplarily, a specific embodiment of selecting the laser scanning angle for local focused laser scanning is given here. When the laser scanning angle is 45°, the reflection fluctuation factors of 5 preset measurement points on the characteristic region of the characteristic cylinder block hole are 0.9, 1.2, 1.1, 0.8, and 1.2 respectively. The reflection fluctuation threshold is set to 1. There are preset measurement points where the reflection fluctuation factor exceeds the reflection fluctuation threshold. Therefore, the increase in the laser scanning angle is not stopped, and the current laser scanning angle (45°) is not selected as the laser scanning angle for local focused laser scanning. When the laser scanning angle is 50°, the reflection fluctuation factors of 5 preset measurement points on the characteristic region of the characteristic cylinder block hole are 0.35, 0.79, 0.98, 0.8, and 0.6 respectively. The reflection fluctuation threshold is set to 1. There are no preset measurement points where the reflection fluctuation factor exceeds the reflection fluctuation threshold, and the variance of the reflection fluctuation factors is 0.044. The variance threshold is set to 0.8, and the variance of the reflection fluctuation factors does not exceed the variance threshold. Therefore, the increase in the laser scanning angle is stopped, and the current laser scanning angle (50°) is selected as the laser scanning angle for local focused laser scanning.

[0059] So far, the technical solution of the present invention has been described in conjunction with the preferred embodiments shown in the drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the protection scope of the present invention.

[0060] The foregoing are only preferred embodiments of the present invention and are not intended to limit the present invention; for those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for measuring automobile cylinder body based on laser displacement sensing technology, characterized in that: include: Placing the automobile cylinder body to be tested on a cylinder body bearing platform, performing a preliminary laser scan on the surface of the automobile cylinder body to be tested, marking the cylinder body holes according to the point cloud data obtained by the preliminary laser scan, acquiring the point cloud data at the cylinder body holes to determine the interference characterization coefficients of the cylinder body holes, and screening the characteristic cylinder body holes based on the comparison of the interference characterization coefficients; Wherein, the interference characterization coefficient is determined according to the depth parameter and the aperture parameter of the cylinder hole; Obtaining the reflected light angles of a preliminary laser scan of a plurality of preset measuring points at a characteristic region of a characteristic cylinder hole, and determining the chamfer shape fluctuation coefficient according to the comparison of the reflected light angles to determine the chamfer shape category of the characteristic cylinder hole; Determining a method of performing local focused laser scanning on a characteristic cylinder hole based on the chamfer shape category; The local focused laser scanning method includes obtaining the reflected light angle of a preset measuring point on a characteristic area of ​​the characteristic cylinder hole to determine the chamfer tendency factor, and adjusting the scanning spot of the local focused laser scanning; Alternatively, the reflection fluctuation factor is determined based on the reflected light angles of each preset measurement point on the feature area at different laser scanning angles to select the laser scanning angle for the local focused laser scanning.

2. The automobile cylinder body measurement method based on laser displacement sensing technology according to claim 1 is characterized in that: The interference characterization coefficient of the cylinder hole is determined by determining a depth parameter and an aperture parameter based on point cloud data at the cylinder hole, calculating a ratio of the depth parameter to the aperture parameter, and determining the ratio as the interference characterization coefficient of the cylinder hole.

3. The automobile cylinder body measurement method based on laser displacement sensing technology according to claim 2 is characterized in that: Screening features cylinder bore include, If the interference characterization coefficient of the cylinder hole meets the interference determination condition, the cylinder hole is selected as a characteristic cylinder hole; The interference determination condition is that the interference characterization coefficient exceeds a preset interference characterization reference value.

4. The automobile cylinder body measurement method based on laser displacement sensing technology according to claim 3 is characterized in that: The method for determining the chamfer morphology fluctuation coefficient is to calculate the angle difference between the reflected light angle of any preset measurement point in the characteristic area of ​​the characteristic cylinder hole and the reflected light angle of the remaining preset measurement points, and determine the variance of the angle difference as the chamfer morphology fluctuation coefficient of the characteristic cylinder hole.

5. The automobile cylinder body measurement method based on laser displacement sensing technology according to claim 4 is characterized in that: The process of determining the chamfer shape category of the characteristic cylinder hole includes: If the chamfer shape fluctuation coefficient of the characteristic cylinder hole meets the first chamfer shape determination condition, the chamfer shape category of the characteristic cylinder hole is determined to be the first chamfer shape category; If the chamfer shape fluctuation coefficient of the characteristic cylinder hole does not meet the first chamfer shape determination condition, the chamfer shape category of the characteristic cylinder hole is determined to be the second chamfer shape category; Among them, the first chamfer shape determination condition is that the chamfer shape fluctuation coefficient exceeds a preset chamfer shape fluctuation reference value.

6. The automobile cylinder body measurement method based on laser displacement sensing technology according to claim 5 is characterized in that: The selected adjustments for local focused laser scanning of characteristic cylinder bores include: If the chamfer shape category is the first chamfer shape category, obtaining the reflected light angle of the preset measuring point on the characteristic area of ​​the characteristic cylinder hole along the cylinder hole diameter direction, determining the chamfer inclination factor according to the reflected light angle of the adjacent preset measuring point, and adjusting the scanning spot diameter of the local focused laser scanning according to the chamfer inclination factor; If the chamfer shape category is the second chamfer shape category, the reflection fluctuation factor is determined based on the reflected light angles of each preset measurement point on the characteristic area of ​​the characteristic cylinder hole at different laser scanning angles to select the laser scanning angle of the local focused laser scanning.

7. The automobile cylinder body measurement method based on laser displacement sensing technology according to claim 6 is characterized in that: The process of determining the chamfer tendency factor includes, Acquire the reflected light angles of adjacent preset measuring points on the characteristic area of ​​the characteristic cylinder hole along the cylinder hole diameter direction; Calculating the difference in reflected light angles of adjacent preset measuring points, and determining the difference as a chamfer tendency factor of the characteristic measuring point; Wherein, the characteristic measurement point is a preset measurement point close to the center position of the cylinder hole among two adjacent preset measurement points.

8. The automobile cylinder body measurement method based on laser displacement sensing technology according to claim 7 is characterized in that: The scanning spot diameter is negatively correlated with the chamfer tendency factor.

9. The automobile cylinder body measurement method based on laser displacement sensing technology according to claim 6 is characterized in that: The process of determining the reflection fluctuation factor includes, Local focused laser scanning is performed on preset measurement points on the characteristic area of ​​the characteristic cylinder hole at different laser scanning angles, and the laser scanning angles are sequentially increased at a preset interval angle change amount, and the difference in reflected light angles at adjacent scanning angles is obtained, and the ratio of the difference to the interval angle change amount is determined as the reflection fluctuation factor of the preset measurement point at the current laser scanning angle.

10. The automobile cylinder body measurement method based on laser displacement sensing technology according to claim 9 is characterized in that: The process of selecting the laser scanning angle for the local focused laser scanning includes, If the reflection fluctuation factors of the preset measuring points on the characteristic area of ​​the characteristic cylinder hole meet the scanning conditions, the increase of the laser scanning angle is stopped, and the current laser scanning angle is selected as the laser scanning angle of the local focusing laser scanning; The scanning condition is that the reflection fluctuation factor of each preset measuring point does not exceed a preset reflection fluctuation threshold, and the variance of the reflection fluctuation factor does not exceed a preset variance threshold.

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