An automatic measuring method and system for hole diameter of engine case parts

Abstract

The present application relates to the field of processing measurement technology, and more particularly to a kind of automatic measurement method and system for engine box class part machining aperture.The method includes the following steps: obtaining original aperture image;Using local gradient sliding window to locate initial edge point set, determining the tilt angle of viewing axis and the deflection azimuth angle of major axis based on fitting method, to realize the independent separation of the two;Using the deflection azimuth angle of major axis to construct rotation relationship to obtain spindle alignment point set;Using the tilt angle of viewing axis to carry out projection transformation to obtain orthogonal projection point set;Based on the tilt angle of viewing axis, determine the local object distance drift of each edge pixel point, and then determine the non-uniform magnification correction gain, carry out numerical compensation restoration on orthogonal projection point set, to obtain the final machining aperture size;Output compensation signal to drive machine tool compensation actuator to adjust tool offset value.The present application solves the non-uniform magnification distortion problem caused by probe rod droop, and realizes the true value restoration of space light field.

Description

Technical Field

[0001] This invention relates to the field of machining measurement technology, and in particular to an automatic measurement method and system for machining hole diameters of engine housing parts. Background Technology

[0002] In the precision manufacturing of large engine housing parts, the machining accuracy of deep holes such as main bearing holes and oil pump holes directly determines the assembly quality and operational performance of the engine. Existing deep hole optical automatic measurement schemes are mostly based on an idealized physical assumption, namely, that the measuring probe maintains ideal rigidity and perfect orthogonal posture when moving in the hole, that the spatial object distance from the optical center of the imaging lens to each point on the hole wall remains absolutely constant, and that the magnification of the imaging system is globally uniformly distributed.

[0003] In actual high-precision machining conditions, the measuring probe extends deep into the hole, forming a typical cantilever beam structure. Due to the probe's own weight and the limitation of the probe material's elastic modulus, the microscopic physical phenomenon of cantilever sag objectively exists. This mechanical deflection causes a slight tilt of the probe's line of sight relative to the central axis of the deep hole, thus rendering the aforementioned idealized assumptions completely invalid. The tilt of the line of sight directly changes the relative distance between the probe lens and different positions on the hole wall, causing a nonlinear shift in the object distance. This results in non-uniform magnification fluctuations on the imaging element, specifically manifested as excessive magnification of near edges and reduction of far edges.

[0004] Conventional measurement schemes often employ only global two-dimensional affine transformations or simple elliptical stretching algorithms for error compensation. These methods essentially apply idealized planar geometric calculations to the actual physical process of deflection deformation. Because the theoretical calculation model is severely disconnected from the actual physical deformation of the probe, and because it fails to introduce physical parameters reflecting local object distance changes, the algorithm cannot eliminate second-order perspective distortion caused by non-uniform magnification. This is the fundamental reason why existing measurement systems consistently exhibit micron-level perspective step errors at the end of deep holes, thus failing to meet the requirements for high-precision hole diameter consistency. Summary of the Invention

[0005] To address the issues of non-uniform magnification distortion caused by probe drooping in existing deep hole measurement technologies, and the inability to eliminate measurement errors due to the disconnect between theoretical models and actual physical deformation, this invention provides an automatic measurement method and system for machining hole diameters in engine housing-type parts.

[0006] In a first aspect, the present invention provides an automatic measurement method for the machining hole diameter of engine housing parts, employing the following technical solution:

[0007] An automatic measurement method for machining hole diameters in engine housing parts includes the following steps:

[0008] The original aperture image is acquired by an image acquisition sensor installed at the end of the machine tool probe; the original aperture image is then processed by edge localization using a local gradient sliding window to lock an initial set of edge points consisting of multiple edge pixels;

[0009] The minor axis length, major axis length, and major axis deflection azimuth angle of the initial edge point set are determined by a fitting algorithm, and the line-of-sight tilt angle is determined based on the ratio of the minor axis length to the major axis length, thereby achieving independent separation of attitude distortion and phase distortion.

[0010] The initial edge point set is rotated and aligned using the major axis deflection azimuth angle to obtain the principal axis aligned point set; the principal axis aligned point set is then projected and transformed using the view axis tilt angle to obtain an orthogonal projection point set that eliminates first-order perspective distortion.

[0011] Based on the tilt angle of the viewing axis, the local object distance drift of each edge pixel is determined. Combined with the preset magnification gradient, the non-uniform magnification correction gain of each edge pixel is determined. Based on this, the modulus compensation of the orthogonal projection point set is performed to restore the final processing aperture size.

[0012] This invention separates and extracts the line-of-sight tilt angle from edge point set features and constructs two key physical calculation indicators: local object distance drift and non-uniform magnification correction gain. By introducing underlying optical physical mechanisms into the measurement algorithm, it directly compensates for local magnification fluctuations caused by cantilever probe sag, ensuring the measurement model closely matches real physical deformation and achieving pixel-level depth reconstruction of the true aperture value.

[0013] Preferably, the edge localization processing of the original aperture image using a local gradient sliding window includes:

[0014] The average pixel width of the micro-tool marks produced by machine tool processing on the original aperture image;

[0015] The sliding window width is set to 3 to 5 times the average pixel width to obtain the gradient calculation sliding window;

[0016] The gradient calculation sliding window is used to perform sliding sampling on the original aperture image to determine the initial edge point set.

[0017] This invention utilizes the physical dimensions of the machining tool marks to constrain the width of the sliding window, enabling the edge extraction process to have high-frequency anti-interference capabilities across metal cutting textures, thus avoiding local false detections caused by surface roughness from the source.

[0018] Preferably, the tilt angle of the visual axis is determined by the following formula:

[0019]

[0020] In the formula, Representing the A depth section; For the first The tilt angle of the view axis at each depth section; For the first The length of the minor axis of a cross-section at a depth; For the first The length of the major axis of a cross-section at a depth; This is a preset zero-prevention parameter.

[0021] Preferably, the set of principal axis alignment points satisfies the following rotational relationship:

[0022]

[0023] In the formula, Representing the One edge pixel; and The first The first depth section The original x and y coordinates of each edge pixel; For the first The major axis deflection azimuth angle of a depth section; and The first The first depth section Alignment x-coordinates and alignment y-coordinates of each edge pixel.

[0024] This invention eliminates the initial angle deviation caused by different installation phases during each random stop of the machine tool spindle by extracting and offsetting the long axis deflection azimuth angle, thus ensuring the consistency of the reference for subsequent projection transformation.

[0025] Preferably, the orthogonal projection point set satisfies the following projection relation:

[0026]

[0027] In the formula, and The first The first depth section The orthogonal x-coordinates and orthogonal y-coordinates of each edge pixel and The first The first depth section Alignment x-coordinates and alignment y-coordinates of each edge pixel; For the first The tilt angle of the view axis at each depth section.

[0028] This invention compresses the elliptical dataset acquired under a tilted field of view into a circular reference dataset under a normal field of view through a purely geometric method, thus completing the cleanup of first-order global perspective distortion.

[0029] Preferably, the final machined hole diameter satisfies the following relationship:

[0030]

[0031] In the formula, For the first The final machined hole diameter of each depth section; This represents the total number of edge pixels. and The first The first depth section The orthogonal x-coordinate and orthogonal y-coordinate of each edge pixel; This is the magnification gradient compensation coefficient; For the first The tilt angle of the view axis at each depth section; For the first The length of the minor axis of a cross-section at a depth; This is a preset zero-prevention parameter.

[0032] This invention utilizes a non-uniform gain term to accurately compensate for near-large and far-small imaging distortion caused by probe attitude bias, enabling each edge pixel in the image to obtain differentiated correction weights based on its own physical coordinate system, thus completely restoring the original spatial appearance of the part.

[0033] Preferably, the method for determining the magnification gradient compensation coefficient is as follows:

[0034] First, on a standard constant-temperature calibration stage, the image acquisition sensor is aligned with a standard ring gauge of known absolute physical dimensions. Next, a micrometer-level precision displacement stage is used to uniformly change the physical object distance of the image acquisition sensor along the optical axis, while simultaneously recording multiple sets of pixel diameter values ​​of the standard ring gauge imaged on the photosensitive array unit under different physical object distances. Then, a linear fit is performed between the physical object distance increment and the pixel diameter change to calculate the physical response slope of the imaging magnification as a function of the spatial object distance. Finally, this physical response slope is divided by the nominal diameter of the standard ring gauge to obtain the magnification gradient compensation coefficient.

[0035] Preferably, after acquiring the original aperture image, the method further includes:

[0036] The original aperture image is denoised using a smoothing filter to eliminate random high-frequency noise.

[0037] Preferably, the depth section corresponds to the axial feed position of the probe within the deep hole component.

[0038] Secondly, the present invention provides an automatic measurement system for the machining hole diameter of engine housing parts, which adopts the following technical solution:

[0039] An automatic measurement system for machining hole diameters of engine housing-type parts includes a processor and a memory. The memory stores computer program instructions, and when the computer program instructions are executed by the processor, the aforementioned automatic measurement method for machining hole diameters of engine housing-type parts is implemented.

[0040] By adopting the above technical solution, a computer program is generated for the automatic measurement method of machining hole diameter of engine housing parts, and stored in the memory so that it can be loaded and executed by the processor. A terminal device can then be made based on the memory and the processor for convenient use.

[0041] The present invention has the following technical effects:

[0042] This invention directly obtains the tolerance zone range of the machine tool CNC system to define the physical search space, and uses the actual statistical micro-cutting tool mark width to set the sliding window step size parameter. This operation enables the invention to directly cross the high-gloss reflection fracture zone caused by tool marks when processing pixel grayscale values, effectively eliminating the interference of jagged pseudo-edges from the physical level, and ensuring that the extracted multiple edge pixels and the final initial edge point set can be stably and realistically anchored on the macroscopic metal contour of the hole wall.

[0043] Furthermore, addressing the unavoidable issue of probe cantilever sag in deep hole measurements, this invention utilizes the least squares method to fit the initial edge point set, accurately separating the major axis deflection azimuth angle and the line-of-sight tilt angle. By rotating and aligning the major axis deflection azimuth angle, the initial angle deviation caused by random spindle stops is eliminated; and by projecting the line-of-sight tilt angle, the elliptical data under the tilted field of view is restored to an orthogonal projection point set. This operation effectively removes global first-order perspective distortion, providing an absolutely unified orthogonal physical observation surface for subsequent microscopic dimension calculations.

[0044] Furthermore, this invention introduces two physical parameters based on the underlying optical lens imaging principle: local object distance drift and non-uniform magnification correction gain. By substituting the spatial depth deviation caused by the viewing axis tilt angle into a preset magnification gradient feature, a differentiated scaling weight is assigned to each edge pixel in the orthogonal projection point set. This calculation logic precisely intercepts and compensates for the optical illusion of near-large and far-small caused by the different object distances above and below the aperture wall, completely eliminating the micron-level oval measurement distortion of deep holes that cannot be solved by conventional methods. It achieves a leap from planar geometric restoration to the true value restoration of the three-dimensional spatial light field, ensuring the absolute physical accuracy of the final processed aperture size. Attached Figure Description

[0045] Figure 1 This is a flowchart of an automatic measurement method for machining hole diameter of engine housing parts provided in an embodiment of the present invention;

[0046] Figure 2 This is an initial edge point set distribution map provided in an embodiment of the present invention;

[0047] Figure 3 This is a comparison image of the multi-dimensional restoration effect and local details provided in the embodiments of the present invention;

[0048] Figure 4 The measurement deviation quantification and residual analysis diagram provided for embodiments of the present invention. Detailed Implementation

[0049] This invention discloses an automatic measurement method for the machining hole diameter of engine housing parts, referring to... Figure 1 This includes steps S1-S4:

[0050] S1: Acquire the original aperture image through an image acquisition sensor set at the end of the machine tool probe; perform edge localization processing on the original aperture image using a local gradient sliding window to lock the initial edge point set composed of multiple edge pixels.

[0051] It should be noted that in real-world deep-hole boring operations for engine blocks or main bearing bores, the metal hole surface will inevitably retain microscopic spiral cutting marks caused by the extrusion of the tool feed. This physical characteristic means that conventional global thresholding or simple differential operators are prone to misidentifying high-contrast tool mark highlight reflection areas as the physical boundary of the hole diameter when extracting edges. If conventional methods are used, it can easily lead to severe serrations or even breaks in the edge contour, resulting in spurious distortions in subsequent fitting calculations. Therefore, the core purpose of this step is to eliminate interference such as tool marks and achieve accurate edge extraction.

[0052] Preferably, as an example, the original aperture image is acquired by an image acquisition sensor located at the end of the machine tool probe; the original aperture image is then processed using a local gradient sliding window to locate the edges, locking an initial set of edge points consisting of multiple edge pixels, including:

[0053] First, an image acquisition sensor installed at the end of the machine tool probe captures the reflected light signal from the hole wall to obtain the original hole diameter image. A smoothing filter is then used to denoise the original hole diameter image to eliminate random high-frequency noise. Simultaneously, the real-time axial coordinate fed back by the machine tool's Z-axis grating encoder is read in real-time via the machine tool's CNC system's fieldbus and defined as the physical feed depth of the probe extending into the deep hole, i.e., the depth section. At this point, the depth section corresponds to the same physical location as the real-time acquired frame of the original hole diameter image.

[0054] Next, retrieve the corresponding machining G-code program from the storage area of ​​the machine tool CNC system, and extract the nominal hole radius and the corresponding tolerance zone range.

[0055] Subsequently, a polar coordinate system is established using the two-dimensional pixel plane where the original aperture image is located as the reference system and the projection point of the lens optical center on the plane as the origin.

[0056] Subsequently, a local gradient sliding window is used to perform differential retrieval on the pixel grayscale values ​​corresponding to the original aperture image, and the following gradient retrieval relationship is constructed:

[0057]

[0058] In the formula, For the first The lower edge of the depth section polar angle The maximum gradient in the direction, and the physical radial position coordinates corresponding to the maximum gradient. That is, the physical location of an edge pixel is locked by its index. The multiple edge pixels obtained after traversing all polar angle directions together constitute a complete set of initial edge points corresponding to that depth; Representing the A depth section; and They represent the first time in the second month. In the polar coordinate system mapped from the original aperture image corresponding to each depth section, along the polar angle... On the ray, the physical radial position coordinates from the origin of polar coordinates are and The pixel grayscale value at that location; The radial search range is determined by the nominal aperture radius and the corresponding tolerance zone range. Polar angle; This is the preset sliding window step size parameter.

[0059] Understandably, during the machining of cast iron cylinder blocks for heavy-duty diesel engines, uneven material hardness results in localized, deep, tear-like micro-cutting marks approximately 5 pixels wide appearing on the hole walls. Under these specific conditions, conventional pixel-by-pixel gradient calculations can produce abrupt peaks at the edges of these marks, leading to the extraction of false concave contours. At this point, the sliding window step size... The value set to cross this width will directly cross the 5-pixel-wide local tear area and extract the true positions of its inner and outer sides. and The difference between the pixel grayscale values ​​at each location is calculated to determine the final maximum gradient value. Physical radial position coordinates It can ignore high-frequency cutting noise and be steadily anchored on the real macroscopic metal boundary of the hole wall, thereby accurately locking the edge pixels and forming the initial edge point set.

[0060] It should be noted that the sliding window step size Methods for obtaining parameters include:

[0061] The average pixel width of the micro-cutting marks generated by the machine tool processing on the original aperture image is calculated, and 3 to 5 times the average pixel width is set as the sliding window step size.

[0062] S2: The minor axis length, major axis length, and major axis deflection azimuth angle of the initial edge point set are determined using a fitting algorithm, and the line-of-sight tilt angle is determined based on the ratio of the minor axis length to the major axis length, thereby achieving independent separation of attitude distortion and phase distortion.

[0063] It should be noted that when the probe penetrates a large aspect ratio hole exceeding 1 meter, the probe, acting as a typical cantilever beam, undergoes physical bending due to its own weight. This physical characteristic means that the probe's optical axis will no longer be parallel to the hole's centerline, causing a perfectly circular hole to be imaged as an ellipse on the image plane. Furthermore, since the rotational phase of the machine tool spindle is random each time it stops, the orientation of this ellipse is also random. If conventional methods are used to perform global compensation indiscriminately, it is highly likely to lead to errors in angle correction direction or distortion in amplitude calculation. Therefore, the core objective of this step is to extract the attitude distortion caused by physical gravity and the phase distortion caused by spindle shutdown.

[0064] Preferably, as an example, a fitting algorithm is used to determine the minor axis length, major axis length, and major axis deflection azimuth angle of the initial edge point set, and the line-of-sight tilt angle is determined based on the ratio of the minor axis length to the major axis length, thereby achieving independent separation of attitude distortion and phase distortion, including:

[0065] First, the initial set of edge points is used as input, and the least squares method is used to perform algebraic fitting of the ellipse equation parameters on the target interior point set to calculate the minor axis length, major axis length, and major axis deflection azimuth of the depth section.

[0066] Next, the viewing angle is calculated based on the minor axis length and major axis length of the depth section, specifically satisfying the following relationship:

[0067]

[0068] In the formula, Representing the A depth section; For the first The tilt angle of the view axis at each depth section; For the first The length of the minor axis of a cross-section at a depth; For the first The length of the major axis of a cross-section at a depth; For example, a preset zero-prevention parameter. Pick .

[0069] Understandably, when machining the end of the 1.2-meter-long engine main bearing bore, gravity caused a minute 0.5-degree physical sag at the probe tip, tilting the sensor's imaging plane accordingly. This directly resulted in the hole, originally 100mm in diameter, appearing as a slightly flattened ellipse with a major axis of 100mm and a minor axis of only 99.96mm in the image. At this point, the minor axis... With long axis The ratio will produce a certain deviation value, which in turn will affect the final calculated line-of-sight tilt angle. It can accurately describe this 0.5-degree microscopic mechanical deformation. Furthermore, under extreme abnormal conditions where large-area cutting fluid blockage leads to failure of the long axis fitting, a situation may occur where the long axis is 0, and the tiny parameter in the denominator... Forced intervention prevented the underlying program from crashing due to division by zero.

[0070] S3: Rotate and align the initial edge point set using the major axis deflection azimuth angle to obtain the principal axis aligned point set; project and transform the principal axis aligned point set using the view axis tilt angle to obtain an orthogonal projection point set that eliminates first-order perspective distortion.

[0071] It should be noted that the radial stopping angle of the machine tool spindle is completely random when it stops in each measurement cycle. This means that the short axis compression direction caused by the probe tilt is constantly rotating and changing in the absolute coordinate system. If conventional methods are used to directly perform radial numerical compensation, it is very easy to cause the compensation vector to be misaligned, incorrectly shrinking the area that should be magnified. Therefore, the core of this step is to perform distortion correction based on the true distortion direction.

[0072] Preferably, as an example, the initial edge point set is rotated and aligned using the major axis deflection azimuth angle to obtain a principal axis aligned point set; the principal axis aligned point set is then projected and transformed using the view axis tilt angle to obtain an orthographic projection point set that eliminates first-order perspective distortion, including:

[0073]

[0074] In the formula, Representing the One edge pixel; and The first The first depth section The original x and y coordinates of each edge pixel; For the first The tilt angle of the view axis at each depth section; For the first The major axis deflection azimuth angle of a depth section; and The first The first depth section Alignment x-coordinate and alignment y-coordinate of each edge pixel and The first The first depth section The orthogonal x-coordinate and orthogonal y-coordinate of each edge pixel.

[0075] Understandably, when the machine tool spindle is measuring a cylinder bore, due to the braking inertia of the servo motor, it stops at a position with a horizontal deflection of 37 degrees. Under this specific working condition, the minor axis of the image caused by the probe drooping is not vertically up and down, but rather obliquely distributed. At this time, the right-side rotation matrix... First, the entire elliptic point set will be rotated 37 degrees in the reverse direction to ensure its major and minor axes are strictly aligned with the computer's XY physical coordinate axes; then, the projection matrix on the left... It will depend on the tilt angle The compressed X-axis pixels are re-stretched so that the final calculated set of orthogonal coordinates can be restored to a circle that is close to a top-down view, thus proving that accurate distortion adjustment can be achieved through the above adjustment.

[0076] S4: Based on the tilt angle of the viewing axis, determine the local object distance drift of each edge pixel, and combine the preset magnification gradient to determine the non-uniform magnification correction gain of each edge pixel. Based on this, perform modulus compensation and restoration on the orthogonal projection point set to obtain the final processing aperture size.

[0077] It should be noted that after the aforementioned distortion correction steps, the image only restores a perfect circle on the macroscopic plane. However, at the microscopic physical optics level, the tilt of the probe inevitably results in the upper part of the aperture wall being closer to the lens than the lower part. This means that the magnification of the imaging lens exhibits a significant gradient non-uniformity within the same image. Without processing, this can easily lead to persistent, unavoidable micrometer-level step errors on both sides of the deep aperture. Therefore, the core purpose of this step is to perform a second-order optical physical distortion depth compensation operation, using non-uniform magnification to correct the gain and assign differentiated restoration weights to each pixel, thereby obtaining the true physical spatial dimensions.

[0078] Preferably, as an example, the local object distance drift of each edge pixel is determined based on the viewing axis tilt angle, and the non-uniform magnification correction gain of each edge pixel is determined in combination with a preset magnification gradient. Based on this, the orthogonal projection point set is subjected to modulus compensation to restore the final processing aperture size, including:

[0079]

[0080] In the formula, For the first The final machined hole diameter of each depth section; This represents the total number of edge pixels. and The first The first depth section The orthogonal x-coordinates and orthogonal y-coordinates of each edge pixel; This is the magnification gradient compensation coefficient; For the first The tilt angle of the view axis at each depth section; For the first The length of the minor axis of a cross-section at a depth; For example, a preset zero-prevention parameter. Pick . This represents the local object distance drift. This is a gain correction for non-uniform amplification.

[0081] It is understandable that, by performing a first-order Taylor series expansion of the lens magnification formula, the degree of distortion in local magnification is approximately linearly related to the local object distance drift of each point relative to the optical center. In three-dimensional geometric mapping, the local object distance drift of a certain edge pixel is exactly equal to the sine component of the probe's line-of-sight tilt angle. The ratio of the physical projection offset of the edge pixel in the tilt direction to the length of the minor axis (i.e., the ratio of the ordinate to the minor axis). The product of these. The physical correction term constructed from this can accurately infer the lost three-dimensional spatial depth at each point from the underlying optical mechanism level.

[0082] To facilitate understanding, the following example illustrates the situation: When inspecting a high-precision hydraulic valve hole with a diameter tolerance of only 0.005mm, the probe's slight tilt causes the actual physical object distance at the lower edge of the hole to increase by 0.2mm compared to the upper edge. Under this specific condition, the inherent mechanism of the optical lens causes the physical size represented by the pixels in the lower half of the image to become larger. In this case, the non-uniform correction gain term constructed from the above formula automatically calculates a gain weight greater than 1 for the lower half of the pixels and an attenuation weight less than 1 for the upper half, thus affecting the final calculated machining hole diameter. It can precisely counteract the optical illusion of objects appearing larger when closer and smaller when farther away caused by this 0.2 mm difference in object distance.

[0083] It should be noted that the magnification gradient compensation coefficient Methods for obtaining parameters include:

[0084] First, on a standard constant temperature calibration platform, align the image acquisition sensor with a standard ring gauge whose absolute physical dimensions are known;

[0085] Next, the physical distance of the image acquisition sensor is changed at a constant speed along the optical axis using a micron-level precision displacement stage, and the pixel diameter values ​​of the standard ring gauge image on the photosensitive array unit under multiple sets of different physical distances are recorded simultaneously.

[0086] Subsequently, a linear fit was performed on the physical object distance increment and the pixel diameter change to calculate the physical response slope of the imaging magnification as the spatial object distance drifted.

[0087] Finally, the amplification gradient compensation coefficient is obtained by dividing the slope of the physical response by the nominal diameter of the standard ring gauge.

[0088] To demonstrate the effectiveness of the solution, relevant experiments were conducted. Below are the images obtained from the experiments:

[0089] Figure 2The image shows the distribution of the initial edge point set. It can be seen from the image that the initial edge point set does not perfectly fit the theoretical aperture reference trajectory, but instead exhibits an elliptic deviation at the microscale and undergoes an overall rotational shift in two-dimensional space.

[0090] Figure 3 The image shows a comparison of the multi-dimensional reconstruction effect and local details. The thick solid line represents the physical reference contour of the true machining value, unaffected by any systematic errors. The dotted line represents the measured contour after first-order reconstruction using only the traditional geometric stretching method. The dashed line represents the final reconstructed contour after compensation using the present invention. The upper and lower magnified windows respectively show the microscopic overlap details of the contours in the top and bottom regions most significantly affected by probe sagging. The image clearly shows that the dotted line representing the traditional method deviates outward from the reference in the upper region and inward from the reference in the lower region. This asymmetrical deviation in opposite directions proves that the traditional method cannot eliminate the near-large and far-small object distance distortion caused by probe sagging due to gravity. In contrast, the dashed line representing the present invention achieves a perfect overlap with the thick solid line in both the global view and the local extreme stress area. This strongly confirms that the present invention can effectively remove distortion and achieve true shape reconstruction.

[0091] Figure 4 For the measurement deviation quantification and residual analysis graph, the horizontal center line serves as the absolute reference line for zero error. The dashed line depicts the systematic residual curve of the radius dimension measured by the conventional method as a function of the circumferential scanning angle. The thin solid line depicts the final residual curve of the radius dimension measured by the present invention as a function of the circumferential scanning angle.

[0092] As can be seen from the images, the residuals representing the dashed lines of the traditional method exhibit violent periodic positive and negative oscillations with the scanning phase angle. The thin solid line representing the present invention shows significantly reduced fluctuations, with the curve closely adhering to the zero-error baseline. This demonstrates that the present invention effectively suppresses systematic composite distortions in deep hole measurements, endowing the detection system with extremely high micron-level measurement accuracy and industrial reliability.

[0093] This invention also discloses an automatic measurement system for machining hole diameters of engine housing-type parts, including a processor and a memory. The memory stores computer program instructions, and when the computer program instructions are executed by the processor, an automatic measurement method for machining hole diameters of engine housing-type parts according to the present invention is implemented.

[0094] The system also includes other components well known to those skilled in the art, such as communication buses and communication interfaces, the settings and functions of which are known in the art and will not be described in detail here.

[0095] In this invention, the aforementioned memory can be any tangible medium containing or storing a program that can be used or combined with an instruction execution system, apparatus, or device. For example, a computer-readable storage medium can be any suitable magnetic or magneto-optical storage medium, such as resistive random access memory (DRAM), dynamic random access memory (DRAM), static random access memory (SRAM), enhanced dynamic random access memory (DRAM), high-bandwidth memory, hybrid memory cube, etc., or any other medium that can be used to store desired information and can be accessed by an application, module, or both. Any such computer storage medium can be part of a device or accessible to or connected to a device.

Claims

1. An automatic measurement method for the machining hole diameter of engine housing parts, characterized in that, Including the following steps: The original aperture image is acquired by an image acquisition sensor installed at the end of the machine tool probe; the original aperture image is then processed by edge localization using a local gradient sliding window to lock an initial set of edge points consisting of multiple edge pixels; The minor axis length, major axis length, and major axis deflection azimuth angle of the initial edge point set are determined using a fitting algorithm. The line-of-sight tilt angle is then determined based on the ratio of the minor axis length to the major axis length, achieving independent separation of attitude distortion and phase distortion. This includes: In the formula, Representing the A depth section; For the first The tilt angle of the view axis at each depth section; For the first The length of the minor axis of a cross-section at a depth; For the first The length of the major axis of a cross-section at a depth; These are preset zero-prevention parameters; The initial edge point set is rotated and aligned using the major axis deflection azimuth angle to obtain the principal axis aligned point set, which satisfies the following rotation relationship: In the formula, Representing the One edge pixel; and The first The first depth section The original x and y coordinates of each edge pixel; For the first The major axis deflection azimuth angle of a depth section; and The first The first depth section Alignment x-coordinates and alignment y-coordinates of each edge pixel; By using the tilt angle of the viewing axis to perform a projection transformation on the principal axis aligned point set, an orthogonal projection point set with first-order perspective distortion eliminated is obtained; Based on the tilt angle of the viewing axis, the local object distance drift of each edge pixel is determined. Combined with the preset magnification gradient, the non-uniform magnification correction gain of each edge pixel is determined. Based on this, the modulus compensation of the orthogonal projection point set is performed to restore the final processing aperture size.

2. The automatic measurement method for machining hole diameter of engine housing parts according to claim 1, characterized in that, The edge localization processing of the original aperture image using a local gradient sliding window includes: The average pixel width of the micro-tool marks produced by machine tool processing on the original aperture image; The sliding window width is set to 3 to 5 times the average pixel width to obtain the gradient calculation sliding window; The gradient calculation sliding window is used to perform sliding sampling on the original aperture image to determine the initial edge point set.

3. The automatic measurement method for machining hole diameter of engine housing parts according to claim 1, characterized in that, The orthogonal projection point set satisfies the following projection relation: In the formula, and The first The first depth section The orthogonal x-coordinates and orthogonal y-coordinates of each edge pixel and The first The first depth section Alignment x-coordinates and alignment y-coordinates of each edge pixel; For the first The tilt angle of the view axis at each depth section.

4. The automatic measurement method for machining hole diameter of engine housing parts according to claim 1, characterized in that, The final machined hole diameter satisfies the following relationship: In the formula, For the first The final machined hole diameter of each depth section; This represents the total number of edge pixels. and The first The first depth section The orthogonal x-coordinate and orthogonal y-coordinate of each edge pixel; This is the magnification gradient compensation coefficient; For the first The tilt angle of the view axis at each depth section; For the first The length of the minor axis of a cross-section at a depth; These are preset zero-prevention parameters; The method for determining the magnification gradient compensation coefficient is as follows: First, on a standard constant-temperature calibration stage, the image acquisition sensor is aligned with a standard ring gauge of known absolute physical dimensions. Next, a micrometer-level precision displacement stage is used to uniformly change the physical object distance of the image acquisition sensor along the optical axis, while simultaneously recording multiple sets of pixel diameter values ​​of the standard ring gauge imaged on the photosensitive array unit under different physical object distances. Then, a linear fit is performed between the physical object distance increment and the pixel diameter change to calculate the physical response slope of the imaging magnification as a function of the spatial object distance. Finally, this physical response slope is divided by the nominal diameter of the standard ring gauge to obtain the magnification gradient compensation coefficient.

5. The automatic measurement method for machining hole diameter of engine housing parts according to claim 1, characterized in that, After obtaining the original aperture image, the process further includes: The original aperture image is denoised using a smoothing filter to eliminate random high-frequency noise.

6. The automatic measurement method for machining hole diameter of engine housing parts according to claim 1, characterized in that, The depth section corresponds to the axial feed position of the probe in the deep hole component.

7. An automatic measurement system for machining hole diameters of engine housing-type parts, characterized in that, include: A processor and a memory, the memory storing computer program instructions, which, when executed by the processor, implement an automatic measurement method for machining hole diameters of engine housing-type parts according to any one of claims 1-6.

Images