Automobile Cylinder Block Measurement Method Based on Laser Displacement Sensing Technology

Abstract

The present invention relates to the technical field of laser measurement, and particularly to a method for measuring an automobile cylinder block based on laser displacement sensing technology. The present invention preliminarily laser scans the surface of the automobile cylinder block to be measured to mark the cylinder block holes, obtains the point cloud data at the cylinder block holes to determine the interference characterization coefficient of the cylinder block holes so as to screen the characteristic cylinder block holes, determines the chamfer shape fluctuation coefficient based on the reflection light angles of several preset measurement points at the characteristic regions of the characteristic cylinder block holes to determine the chamfer shape category of the characteristic cylinder block holes, selects the adjustment method for locally focusing laser scanning of the characteristic cylinder block holes based on the chamfer shape category, and further realizes the rapid measurement of the actual chamfer shape structure of the cylinder block holes, adaptively adjusts the laser scanning method at the cylinder block holes according to different chamfer shape structures, and improves the measurement accuracy and measurement efficiency of the automobile cylinder block.

Description

Technical Field

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

[0002] In the automotive manufacturing industry, the cylinder block is the core component of the engine, and its manufacturing precision has a decisive impact on engine performance. Among them, the quality of the cylinder bore 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 engine's power output, fuel economy, stability, and service life. In actual production, the vast majority of cylinder bores are designed with a chamfered structure. The presence of the chamfer not only serves as a guide during the assembly process and prevents component damage, but also relieves stress concentration and enhances the overall reliability of the cylinder block. Different cylinder bores have different 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 chamfer structures have different reflection characteristics and scattering patterns for lasers. Using the same measurement parameters, it is difficult to accurately capture subtle shape changes and dimensional information of the chamfered area, which affects 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 three-dimensional coordinate measurement method and system for the center of the positioning hole of an automobile cylinder workpiece, wherein the method includes: S10 obtaining a point cloud image of the positioning hole area of the automobile 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, thereby completing the three-dimensional coordinate measurement of the center of the positioning hole of the automobile cylinder workpiece.

[0004] The following problems also exist in the prior art:

[0005] The existing technology does not take into account that the different morphological structures of the cylinder hole chamfer will affect the measurement accuracy of laser detection. The existing technology 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

[0006] To this end, the present invention provides a method for measuring an automobile cylinder block based on laser displacement sensing technology, so as to overcome the problems in the prior art that the actual chamfer morphology structure of the cylinder block holes cannot be measured quickly, the laser scanning method at the cylinder block holes cannot be adaptively adjusted according to different chamfer morphology structures, and the measurement accuracy and efficiency of the automobile cylinder block are affected.

[0007] To achieve the above object, the present invention provides a method for measuring an automobile cylinder block based on laser displacement sensing technology, including:

[0008] Place the automobile cylinder block to be measured on the cylinder block bearing platform, conduct preliminary laser scanning on the surface of the automobile cylinder block to be measured, mark the cylinder block holes according to the point cloud data obtained from the preliminary laser scanning, 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;

[0009] Among them, the interference characterization coefficient is determined according to the depth parameter and the aperture parameter of the cylinder block hole;

[0010] Obtain the reflection light angles of several preset measurement points at the characteristic area of the characteristic cylinder block hole, determine the chamfer morphology fluctuation coefficient according to the comparison of the reflection light angles, and determine the chamfer morphology category of the characteristic cylinder block hole;

[0011] Based on the chamfer morphology category, determine the method of local focused laser scanning for the characteristic cylinder block hole;

[0012] The method of local focused laser scanning includes obtaining the reflection light angles of 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 scanning;

[0013] Or determine the reflection fluctuation factor based on the reflection light angles of each preset measurement point on the characteristic area at different laser scanning angles, so as to select the laser scanning angle of the local focused laser scanning.

[0014] 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.

[0015] Further, screening the characteristic cylinder block holes includes,

[0016] If the interference characterization coefficient of the cylinder block hole meets the interference determination condition, then screen the cylinder block hole as a characteristic cylinder block hole;

[0017] Among them, the interference determination condition is that the interference characterization coefficient exceeds a preset interference characterization reference value.

[0018] Further, the method for determining the chamfer shape fluctuation coefficient is to calculate the angular difference between the reflected light angles at any preset measurement point in the characteristic region of the characteristic cylinder hole and the reflected light angles at the other preset measurement points, and determine the variance of the angular difference as the chamfer shape fluctuation coefficient of the characteristic cylinder hole.

[0019] Further, the process of determining the chamfer shape category of the characteristic cylinder hole includes

[0020] If the chamfer shape fluctuation coefficient of the characteristic cylinder hole meets the first chamfer shape determination condition, it is determined that the chamfer shape category of the characteristic cylinder hole is the first chamfer shape category;

[0021] If the chamfer shape fluctuation coefficient of the characteristic cylinder hole does not meet the first chamfer shape determination condition, it is determined that the chamfer shape category of the characteristic cylinder hole is the second chamfer shape category;

[0022] Among them, the first chamfer shape determination condition is that the chamfer shape fluctuation coefficient exceeds a preset chamfer shape fluctuation reference value.

[0023] Further, the method for selecting the adjustment method for local focused laser scanning of the characteristic cylinder hole includes

[0024] If the chamfer shape category is the first chamfer shape category, obtain the reflected light angle at the preset measurement point along the diameter direction of the cylinder hole in the characteristic region of the characteristic cylinder hole, determine the chamfering tendency factor according to the reflected light angles at adjacent preset measurement points, and adjust the scanning spot diameter of the local focused laser scanning according to the chamfering tendency factor;

[0025] If the chamfer shape category is the second chamfer shape category, determine the reflection fluctuation factor based on the reflected light angles at each preset measurement point in the characteristic region of the characteristic cylinder hole at different laser scanning angles, so as to select the laser scanning angle of the local focused laser scanning.

[0026] Further, the process of determining the chamfering tendency factor includes

[0027] Obtain the reflected light angles at adjacent preset measurement points along the diameter direction of the cylinder hole in the characteristic region of the characteristic cylinder hole;

[0028] Calculate the difference between the reflected light angles at adjacent preset measurement points, and determine the difference as the chamfering tendency factor of the characteristic measurement point.

[0029] Among them, the characteristic measurement point is the preset measurement point closer to the center position of the cylinder hole among the two adjacent preset measurement points.

[0030] Further, the scanning spot diameter is negatively correlated with the chamfering tendency factor.

[0031] Further, the process of determining the reflection fluctuation factor includes

[0032] Performing local focused laser scanning on preset measurement points on the characteristic area of the characteristic cylinder hole at different laser scanning angles, where the laser scanning angles increase successively with a preset interval angle change amount, obtaining the difference in the reflection light angles at adjacent scanning angles, and determining 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.

[0033] Further, the process of selecting the laser scanning angle for local focused laser scanning includes

[0034] If the reflection fluctuation factors of the preset measurement points on the characteristic area 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;

[0035] wherein, the scanning conditions are that the reflection fluctuation factors of all preset measurement points do not exceed a preset reflection fluctuation threshold, and the variance of the reflection fluctuation factors does not exceed a preset variance threshold.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention preliminarily performs laser scanning on the surface of the to-be-tested automobile cylinder block to mark the cylinder holes, obtains the point cloud data at the cylinder holes to determine the interference characterization coefficient of the cylinder holes so as 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 area of the characteristic cylinder hole to determine the chamfer shape category of the characteristic cylinder hole, and selects the adjustment method for local focused laser scanning of the characteristic cylinder hole based on the chamfer shape category. Furthermore, the actual chamfer shape structure of the cylinder hole is quickly measured, the laser scanning method at the cylinder hole is adaptively adjusted according to different chamfer shape structures, and the measurement accuracy and measurement efficiency of the automobile cylinder block are improved.

[0037] 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. In 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 accurate measurement of the key cylinder holes that may affect 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, the screening of the characteristic cylinder holes is realized, and the measurement accuracy and measurement efficiency of the automobile cylinder block are improved.

[0038] In particular, the present invention determines the chamfer form fluctuation coefficient by comparing the reflection light angles to determine the chamfer form category of the characteristic cylinder hole. It can be understood that chamfer structures with different forms have different reflection characteristics for laser light. The comparison of the reflection light angles can characterize the chamfer form of the characteristic cylinder hole, and clarify the chamfer form category of the characteristic cylinder hole. Efficient laser measurement methods 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.

[0039] In particular, 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 characteristic cylinder hole is in an arc shape. 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 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 characteristic 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, 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.

[0040] 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 characteristic region of the characteristic 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 characteristic 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 characteristic region 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, ensuring that the laser scanning angle matches the actual shape of the linear chamfer, making the measurement result 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 that the most suitable laser scanning angle for the current linear chamfer measurement can be quickly locked, optimizing the entire scanning process. Furthermore, the actual chamfer shape structure of the cylinder hole is quickly measured, and the laser scanning method at the cylinder hole is adaptively adjusted according to different chamfer shape structures, improving the measurement accuracy and measurement efficiency of the automotive cylinder block. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 FIG. 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;

[0042] Figure 2 FIG. is a logical flow chart for screening characteristic cylinder holes according to an embodiment of the present invention;

[0043] Figure 3 FIG. is a logical flow chart for determining the chamfer shape category of a characteristic cylinder hole according to an embodiment of the present invention;

[0044] Figure 4 FIG. is a logical flow chart for selecting an adjustment method for local focused laser scanning of a characteristic cylinder hole according to an embodiment of the present invention;

[0045] Figure 5 FIG. is a top view schematic diagram of a characteristic cylinder hole according to an embodiment of the present invention;

[0046] In the figure: 1. Characteristic cylinder hole; 2. Characteristic region; 3. Cylinder hole diameter; 4. Preset measurement point along the cylinder hole diameter direction. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0047] In order to make the objectives and advantages of the present invention more clearly understood, 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.

[0048] 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 principles of the present invention and do not limit the protection scope of the present invention.

[0049] 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 the 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, and therefore should not be construed as a limitation of the present invention.

[0050] Please refer to Figure 1 As shown, it is a step diagram of the method for measuring an automobile cylinder block based on laser displacement sensing technology in 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:

[0051] 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.

[0052] 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, and image processing or computer graphics methods are used to extract and mark the boundaries of the identified cylinder block hole point cloud regions, which will not be elaborated here.

[0053] 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.

[0054] Among them, the interference characterization coefficient is determined according to the depth parameter and aperture parameter of the cylinder block hole.

[0055] Specifically, the depth parameter of the cylinder block hole can be obtained by establishing a correlation between the laser scanning 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.

[0056] Step S300: Obtain the reflection light angles of several preset measurement points at the characteristic area of the characteristic cylinder block hole for preliminary laser scanning, and determine the chamfer form fluctuation coefficient according to the comparison of the reflection light angles to determine the chamfer form category of the characteristic cylinder block hole.

[0057] Specifically, the characteristic area of the characteristic cylinder block hole is the chamfer area of the characteristic cylinder block 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 characteristic cylinder block hole can be calculated, and the chamfer area can be preliminarily determined according to the change of the normal vectors, so as to determine the characteristic area of the characteristic cylinder block hole, which will not be elaborated here.

[0058] Specifically, the preset measurement points can be set by those skilled in the art according to the measurement experience of several cylinder block holes of the same type. Preferably, for the circular characteristic cylinder block hole, the circumference can be equally divided into 12 parts, and a measurement point is set every 30°. Along the axial direction of the cylinder block hole, a measurement point is set every 1 mm.

[0059] Step S400: Determine the local focused laser scanning method for the characteristic cylinder block hole based on the chamfer form category.

[0060] 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 scanning.

[0061] Or determine 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 scanning.

[0062] Specifically, the scanning spot is the spot formed when the laser beam irradiates the surface of the object during laser scanning, and the laser scanning angle is the incident angle of the laser beam relative to the surface of the characteristic cylinder block hole.

[0063] Specifically, the method for determining the interference characterization coefficient of the cylinder block holes is to determine the depth parameter and the hole diameter parameter based on the point cloud data at the cylinder block holes, calculate the ratio of the depth parameter to the hole diameter parameter, and determine the ratio as the interference characterization coefficient of the cylinder block holes.

[0064] Specifically, please refer to Figure 2 shown in the figure, which is the logic flow chart for screening characteristic cylinder block holes in the embodiment of the present invention. Screening characteristic cylinder block holes includes

[0065] 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;

[0066] If the interference characterization coefficient of the cylinder block hole does not meet the interference determination condition, then the cylinder block hole is not screened;

[0067] Among them, the interference determination condition is that the interference characterization coefficient exceeds a preset interference characterization reference value.

[0068] 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 automobile cylinder block measurement. 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.

[0069] Specifically, the present invention screens 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 at the cylinder block holes during laser scanning. During the measurement of the automobile cylinder block, measurement resources such as measurement time and equipment usage duration are limited. By screening out characteristic cylinder block 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 block holes that may affect product quality, but also improve the overall measurement efficiency and make the measurement work more efficient and reasonable. The present invention screens characteristic cylinder block holes according to the comparison of the ratio of the calculated depth parameter to the hole diameter parameter, and thus realizes the screening of characteristic cylinder block holes, improving the measurement accuracy and measurement efficiency of the automobile cylinder block.

[0070] Specifically, it can be understood that the larger the interference representation coefficient is, the larger the ratio of the depth parameter to the aperture parameter of the cylinder block hole is. For the cylinder block holes with a larger ratio, the reflection and scattering of light in the holes are more complex, which is likely to interfere with the laser measurement, resulting in an increase in measurement error and having a greater impact on 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 dimensions and shapes of the automotive cylinder block. Furthermore, the screening of the characteristic cylinder block holes is realized, and the measurement accuracy and efficiency of the automotive cylinder block are improved.

[0071] Specifically, the method for determining the chamfer shape fluctuation coefficient is to calculate the angular difference between the reflection light angles at any preset measurement point in the characteristic region of the characteristic cylinder block hole and the reflection light angles at 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.

[0072] 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 region 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, which can be obtained by using the angle sensor in the laser displacement sensing device and will not be elaborated here.

[0073] Specifically, please refer to Figure 3 As shown, it is the logic flow chart for determining the chamfer shape category of the characteristic cylinder block hole in the embodiment of the present invention. The process of determining the chamfer shape category of the characteristic cylinder block hole includes

[0074] 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;

[0075] 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;

[0076] Among them, the first chamfer shape determination condition is that the chamfer shape fluctuation coefficient exceeds a preset chamfer shape fluctuation reference value.

[0077] Specifically, the preset chamfer shape fluctuation reference value can be set by those skilled in the art according to the accuracy requirements of automotive cylinder block measurement. The higher the accuracy requirements are, the smaller the preset chamfer shape fluctuation reference value is. 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.

[0078] Specifically, 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 block hole. It can be understood that chamfer structures of different forms have different laser reflection characteristics. The comparison of the reflection light angles can characterize the chamfer form of the characteristic cylinder block hole. By clarifying the chamfer form category of the characteristic cylinder block hole, efficient laser measurement methods 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 stable and reliable completion of the measurement task under different chamfer form categories. The present invention judges the chamfer form category of the characteristic cylinder block hole through the chamfer form fluctuation coefficient. Furthermore, it realizes the rapid measurement of the actual chamfer form structure of the cylinder block hole, improving the measurement accuracy and efficiency of the automotive cylinder block.

[0079] Specifically, it can be understood that there are differences in geometric shapes between linear chamfers and arc chamfers, resulting in different characteristics of laser reflection light angles. The change in the reflection light angle of a 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. However, the change in the reflection light angle of an arc chamfer is more complex, the angle difference at different points is large, and the variance is also large. By calculating the chamfer form fluctuation coefficient, these differences can be accurately captured, thus effectively distinguishing linear chamfers and arc chamfers. Furthermore, it realizes the rapid measurement of the actual chamfer form structure of the cylinder block hole, improving the measurement accuracy and efficiency of the automotive cylinder block.

[0080] Specifically, please refer to Figure 4 as shown, which is the logic flow chart of the adjustment method for selecting local focused laser scanning of the characteristic cylinder block hole in the embodiment of the present invention. The adjustment method for selecting local focused laser scanning of the characteristic cylinder block hole includes

[0081] If the chamfer form category is the first chamfer form category, obtain the reflection light angle of the preset measurement point along the diameter direction of the cylinder block hole in the characteristic area of the characteristic 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;

[0082] Specifically, under the condition of the first chamfer shape category, the chamfer tendency factor is determined according to the reflection light angles of adjacent preset measurement points to adjust the scanning spot diameter of local focused laser scanning. It can be understood that the first chamfer shape category means that the chamfer of the characteristic cylinder hole is in an arc shape. 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 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, so as to more accurately measure the contour size and shape of the cylinder hole, reduce the measurement error, and improve the 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 characteristic cylinder hole can be clarified. Adjusting the scanning spot for these specific characteristics can realize the adaptive adjustment of local focused laser scanning, make the measurement more targeted, and better adapt to the measurement requirements of various arc chamfers with different shapes. Furthermore, the actual chamfer shape structure of the cylinder hole is measured quickly, and the laser scanning method at the cylinder hole is adjusted adaptively according to different chamfer shape structures, improving the measurement accuracy and measurement efficiency of the automotive cylinder block.

[0083] If the chamfer shape category is the second chamfer shape category, the reflection fluctuation factor is determined based on the reflection light angles of each preset measurement point on the characteristic region of the characteristic cylinder hole at different laser scanning angles to select the laser scanning angle of local focused laser scanning.

[0084] Specifically, 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 characteristic region of the characteristic 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 characteristic 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 characteristic region 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. 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 shape structure of the cylinder hole is quickly measured, and the laser scanning method at the cylinder hole is adaptively adjusted according to different chamfer shape structures, improving the measurement accuracy and measurement efficiency of the automotive cylinder block.

[0085] Specifically, please refer to Figure 5 shown in the figure, which is a top view schematic diagram of the characteristic cylinder hole of the embodiment of the present invention. The process of determining the chamfer tendency factor includes

[0086] Obtaining the reflection light angles of adjacent preset measurement points on the characteristic region of the characteristic cylinder hole along the diameter direction of the cylinder hole;

[0087] Calculating the difference between the reflection light angles of adjacent preset measurement points, and determining the difference as the chamfer tendency factor of the characteristic measurement point.

[0088] Wherein, the characteristic measurement point is the preset measurement point close to the center position of the cylinder hole among two adjacent preset measurement points.

[0089] Exemplarily, a specific embodiment of determining the chamfering tendency factor of the characteristic measurement point position is given here. The reflection light angles of 5 preset measurement points along the diameter direction of the characteristic cylinder hole in the characteristic area of the feature 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°.

[0090] Specifically, the scanning spot diameter is negatively correlated with the chamfering tendency factor.

[0091] 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 area 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 area with a large curvature, the scanning spot can be adjusted smaller to capture the details of the chamfer more precisely. For the arc chamfer area 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 area 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.

[0092] Specifically, the process of determining the reflection fluctuation factor includes

[0093] Performing local focused laser scanning on the preset measurement points in the characteristic area of the feature cylinder hole at different laser scanning angles. The laser scanning angles increase sequentially 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.

[0094] 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°.

[0095] 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 successively 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°.

[0096] Specifically, the process of selecting the laser scanning angle for local focused laser scanning includes,

[0097] If the reflection fluctuation factors of each preset measurement point on the characteristic area 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;

[0098] If the reflection fluctuation factors of each preset measurement point on the characteristic area of the characteristic cylinder hole do not meet the scanning conditions, increase the laser scanning angle;

[0099] 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.

[0100] 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.

[0101] 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.

[0102] Specifically, it can be understood that the laser scanning angle is sequentially increased by a preset interval angle change amount, and the difference between the reflected light angles 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 of the laser scanning angle at each preset measurement point. The surface of the linear chamfer is relatively regular, and the change of 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 of 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 quickly measured, and the laser scanning method at the cylinder block hole is adaptively adjusted according to different chamfer shape structures, improving the measurement accuracy and measurement efficiency of the automotive cylinder block.

[0103] Exemplarily, a specific embodiment of selecting the laser scanning angle of 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 of the laser scanning angle is not stopped, and the current laser scanning angle (45°) is not selected as the laser scanning angle of 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. The variance of the reflection fluctuation factors does not exceed the variance threshold. Therefore, the increase of the laser scanning angle is stopped, and the current laser scanning angle (50°) is selected as the laser scanning angle of local focused laser scanning.

[0104] 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 fall within the protection scope of the present invention.

[0105] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention; for those skilled in the art, various modifications and variations can be made to the present invention. 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. An automobile cylinder block measurement method based on laser displacement sensing technology, characterized in that, Including: Placing the cylinder block of the vehicle to be tested on the cylinder block bearing platform, performing preliminary laser scanning on the surface of the cylinder block of the vehicle to be tested, marking the cylinder block holes according to the point cloud data obtained from the preliminary laser scanning, 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; Wherein, 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 in the characteristic region of the characteristic cylinder block hole during preliminary laser scanning, and determining the chamfer form fluctuation coefficient according to the comparison of the reflection light angles to determine the chamfer form category of the characteristic cylinder block hole; Determining the method of locally focused laser scanning for the characteristic cylinder block hole based on the chamfer form category; The method of locally focused laser scanning includes obtaining the reflection light angles of the preset measurement points on the characteristic region of the characteristic cylinder block hole to determine the chamfer tendency factor, and adjusting the scanning spot of the locally focused laser scanning; Or determining the reflection fluctuation factor based on the reflection light angles of each preset measurement point on the characteristic region at different laser scanning angles to select the laser scanning angle of the locally focused laser scanning; Wherein, the process of determining the chamfer tendency factor includes obtaining the reflection light angles of adjacent preset measurement points along the diameter direction of the cylinder block hole in the characteristic region of the characteristic cylinder block hole; Calculating the difference between the reflection light angles of adjacent preset measurement points, and determining the difference as the chamfer tendency factor of the characteristic measurement point, where the characteristic measurement point is the preset measurement point closer to the center of the cylinder block hole among the two adjacent preset measurement points; The process of determining the reflection fluctuation factor includes performing locally focused laser scanning on the preset measurement points in 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, obtaining the difference between the reflection light angles at adjacent scanning angles, and determining 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.

2. The method for measuring an automobile cylinder block based on laser displacement sensing technology according to claim 1, wherein The method of 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.

3. The method for measuring an automotive cylinder block based on laser displacement sensing technology according to claim 2, wherein, Screening the characteristic cylinder block holes includes: If the interference characterization coefficient of the cylinder block hole meets the interference determination condition, then screening the cylinder block hole as a characteristic cylinder block hole; Wherein, the interference determination condition is that the interference characterization coefficient exceeds a preset interference characterization reference value.

4. The method for measuring an automotive cylinder block based on laser displacement sensing technology according to claim 3, wherein The method of determining the chamfer form fluctuation coefficient is to calculate the angle difference between the reflection light angle of any preset measurement point in the characteristic region of the characteristic cylinder block hole and the reflection light angles of the remaining preset measurement points, and determine the variance of the angle difference as the chamfer form fluctuation coefficient of the characteristic cylinder block hole.

5. The method for measuring an automotive cylinder block based on laser displacement sensing technology according to claim 4, wherein The process of determining the chamfer form category of the characteristic cylinder block hole includes: If the chamfer form fluctuation coefficient of the characteristic cylinder block hole meets the first chamfer form determination condition, then determining the chamfer form category of the characteristic cylinder block hole as the first chamfer form category; If the chamfer form fluctuation coefficient of the characteristic cylinder block hole does not meet the first chamfer form determination condition, it is determined that the chamfer form category of the characteristic cylinder block hole is the second chamfer form category; Among them, the first chamfer form determination condition is that the chamfer form fluctuation coefficient exceeds a preset chamfer form fluctuation reference value.

6. The method for measuring an automotive cylinder block based on laser displacement sensing technology according to claim 5, characterized in that, The selected adjustment method for performing local focused laser scanning on the characteristic cylinder block 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 cylinder block hole on the characteristic area of the characteristic cylinder block hole, determine the chamfering 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 chamfering tendency factor; 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 characteristic area 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.

7. The method for measuring an automobile cylinder block based on a laser displacement sensing technology according to claim 6, wherein, The scanning spot diameter has a negative correlation with the chamfering tendency factor.

8. The method for measuring an automotive cylinder block based on laser displacement sensing technology according to claim 7, wherein, The process of selecting the laser scanning angle of the local focused laser scanning includes, If the reflection fluctuation factors of each preset measurement point on the characteristic area of the characteristic cylinder block hole meet the scanning conditions, stop increasing the laser scanning angle, and select the current laser scanning angle as the laser scanning angle of the 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.

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