CN117288062A - Thread detection device and method suitable for long shaft part of aero-engine - Google Patents

Thread detection device and method suitable for long shaft part of aero-engine Download PDF

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Publication number
CN117288062A
CN117288062A CN202311061389.6A CN202311061389A CN117288062A CN 117288062 A CN117288062 A CN 117288062A CN 202311061389 A CN202311061389 A CN 202311061389A CN 117288062 A CN117288062 A CN 117288062A
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China
Prior art keywords
thread
module
long shaft
measurement
projection image
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Inventor
袁园
黄意
魏翔
陈春
谢海鹏
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AECC South Industry Co Ltd
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AECC South Industry Co Ltd
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Priority to CN202311061389.6A priority Critical patent/CN117288062A/en
Publication of CN117288062A publication Critical patent/CN117288062A/en
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B5/00—Measuring arrangements characterised by the use of mechanical techniques
    • G01B5/02—Measuring arrangements characterised by the use of mechanical techniques for measuring length, width or thickness
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/08—Measuring arrangements characterised by the use of optical techniques for measuring diameters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/08—Measuring arrangements characterised by the use of optical techniques for measuring diameters
    • G01B11/12—Measuring arrangements characterised by the use of optical techniques for measuring diameters internal diameters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B5/00—Measuring arrangements characterised by the use of mechanical techniques
    • G01B5/0002—Arrangements for supporting, fixing or guiding the measuring instrument or the object to be measured

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Length Measuring Devices By Optical Means (AREA)

Abstract

The invention discloses a thread detection device and a thread detection method suitable for long-axis parts of an aeroengine, which overcome the defects that axial details cannot be measured in radial dimension measurement and radial resolution of projection measurement is insufficient in the mode of combining radial dimension measurement with projection measurement, simultaneously improve the measurement precision and measurement range of a projection measurement method, realize thread parameter measurement with the precision of about 0.01 millimeter under the condition that the measured shaft diameter is as high as one hundred millimeters, simultaneously meet the detection requirements of large-span and high-precision details of the long-axis parts of the aeroengine, adopt non-contact optical detection, cannot be additionally arranged in an auxiliary mode, greatly improve the thread measurement efficiency and meet the requirements of mass thread detection.

Description

Thread detection device and method suitable for long shaft part of aero-engine
Technical Field
The invention relates to the technical field of precise measurement, in particular to a thread detection device and method suitable for long shaft parts of an aeroengine.
Background
The flexible long shaft of the vortex shaft aero-engine is a key component of the aero-engine and is responsible for transmitting thrust generated by the aero-engine to an airplane, and the threaded connection on the long shaft is a key structure bearing high-speed rotation, high temperature and high pressure and complex stress environments, and the quality of the flexible long shaft directly influences the reliability, safety and performance of the aero-engine. The threaded connection on the long shaft generally has the requirements of high precision, high strength, high wear resistance and the like, the requirements enable the machining and measurement of the threads of the long shaft of the aeroengine to have higher technical difficulty, the threaded measurement is a key link for ensuring that the quality of the threads meets the design requirements, and the deviation in the machining process can be timely found and corrected before the assembly through the measurement of the pitch diameter and the runout of the threads, so that the assembly stability and the assembly strength of the aeroengine are ensured. In addition, the high-quality threaded connection can improve the working efficiency of the engine, reduce the fuel consumption and improve the endurance mileage of the aircraft.
However, the length of the flexible long shaft of the aeroengine is longer, generally more than 600mm, and even more than 1000mm, and the stroke of a common thread detector is only 400mm at maximum, so that the long shaft type part cannot be installed, and the flexible long shaft cannot be measured in a threaded manner. The optical shaft detector can only detect external conventional geometric dimensions such as outer diameter, length and the like, and cannot measure thread parameters. In addition, in the conventional method of performing combined measurement by using a screw gauge, a three-needle method, etc., the offline measurement method is adopted, so that the problem of low measurement efficiency is solved, and the key parameters such as runout are difficult to analyze and measure due to lack of a unified reference. Therefore, the existing thread measurement method cannot meet the requirements of high-precision and large-batch thread detection of long shaft parts of aeroengines.
Disclosure of Invention
The invention provides a thread detection device and a thread detection method suitable for long shaft parts of an aeroengine, and aims to solve the technical problem that the existing thread measurement method cannot meet the requirements of high-precision and large-batch thread detection of the long shaft parts of the aeroengine.
According to one aspect of the present invention, there is provided a thread inspection device for use with an aero-engine long shaft component, comprising:
the radial dimension measuring module is used for measuring any radial dimension of the long shaft part;
the machine vision measurement module is used for shooting projection images of the long-axis part in the radial direction;
the motion shaft module is used for driving the radial dimension measuring module and the machine vision measuring module to move along the axial direction of the long shaft part and is also used for axially positioning and clamping the long shaft part;
the control module is electrically connected with the radial dimension measuring module, the machine vision measuring module and the moving axis module, and is used for controlling the moving axis module to drive the radial dimension measuring module to move to any optical axis position on the long axis part, measuring to obtain the radial dimension at the reference position by taking the optical axis position as a reference, controlling the moving axis module to drive the machine vision measuring module to align with the reference position so as to shoot a projection image at the reference position, controlling the moving axis module to drive the machine vision measuring module to align with the screw thread and shoot the projection image of the screw thread, finally taking the radial dimension at the reference position measured by the radial dimension measuring module as the radial reference dimension, and calculating to obtain the large diameter value, the medium diameter value and the screw pitch of the screw thread by combining the projection image at the reference position shot by the machine vision measuring module and the projection image of the screw thread.
Further, the motion axis module is further used for driving the long shaft part to rotate, the control module is further used for controlling the motion axis module to rotate for one circle, controlling the machine vision measurement module to shoot at a preset angle at fixed intervals in the rotating process, obtaining a plurality of thread projection images, and calculating to obtain pitch diameter values of threads in each thread projection image, so that pitch diameter runout of the threads is calculated.
Further, the radial dimension measuring module is a light curtain type shaft diameter measuring sensor which is oppositely arranged at two sides of the long shaft part along the radial direction, the machine vision measuring module comprises an imaging unit and a light source unit, the imaging unit and the light source unit are oppositely arranged at two sides of the long shaft part along the radial direction, the imaging unit is an industrial camera matched with a telecentric lens, the light source unit is a parallel backlight source, the center of the light curtain type shaft diameter measuring sensor is aligned with the rotation center of the long shaft part, and the visual field edge of the imaging unit is aligned with the rotation center of the long shaft part.
Further, the control module is further used for performing shielding distortion compensation on the threaded projection image after obtaining the threaded projection image.
Further, the process of the control module for carrying out shielding distortion compensation on the threaded projection image is as follows:
establishing a three-dimensional coordinate system by taking the rotation axis of the long-axis part as a z axis;
intersecting a cutting plane parallel to the xoz plane with the single-sided spiral surface to obtain a spiral curve;
obtaining an extremum by deriving a z-axis coordinate equation of the spiral curve to obtain an actually measured thread section profile;
and calculating a compensation value based on the actually measured thread cross section profile and the theoretical thread cross section profile, and performing shielding distortion compensation on the thread projection image based on the compensation value to obtain a real image.
Further, the machine vision measuring device also comprises a calibrating module used for the machine vision measuring module to calibrate the image.
Further, the motion axis module comprises a measurement axis motion unit, a clamping axis motion unit and a rotary table unit, wherein the measurement axis motion unit is arranged on two sides of the long axis part in a radial opposite mode and can move along an axial direction, the radial dimension measurement module and the machine vision measurement module are fixedly arranged on the measurement axis motion unit, the clamping axis motion unit is fixedly arranged on the rotary table unit and can move along the axial direction in a relative mode and is used for clamping and positioning the long axis part in an axial direction, and the rotary table unit is used for driving the clamping axis motion unit and the long axis part to synchronously rotate.
In addition, the invention also provides a thread detection method suitable for the long shaft part of the aeroengine, which adopts the thread detection device and comprises the following steps:
controlling the motion axis module to drive the radial dimension measuring module to move to any optical axis position on the long axis part, and measuring to obtain the radial dimension at the reference position by taking the optical axis position as a reference;
controlling the motion axis module to drive the machine vision measuring module to align with the reference position so as to shoot a projection image at the reference position;
controlling the motion axis module to drive the machine vision measuring module to align with the threads and shooting projection images of the threads;
and the radial dimension measuring module is used for measuring the radial dimension at the reference position to serve as the radial reference dimension, and the large diameter value, the middle diameter value and the screw pitch of the screw thread are calculated by combining the projection image at the reference position and the projection image of the screw thread shot by the machine vision measuring module.
Further, the method also comprises the following steps:
and controlling the motion axis module to drive the long shaft part to rotate for one circle, controlling the machine vision measurement module to shoot at a preset angle at fixed intervals in the rotating process, obtaining a plurality of thread projection images, and calculating to obtain the pitch diameter value of the threads in each thread projection image, so as to calculate to obtain pitch diameter runout of the threads.
Further, after obtaining the projection image of the screw thread, the following is included:
and performing shielding distortion compensation on the threaded projection image.
The invention has the following effects:
the invention relates to a thread detection device suitable for a long shaft part of an aeroengine, which takes any optical axis position on the long shaft part as a reference position, firstly utilizes a radial dimension measurement module to measure radial dimension data of the reference position, and takes the radial dimension data as actual radial reference dimension for measuring the major diameter and the intermediate diameter of threads. After the radial projection image at the reference position is shot by the machine vision measuring module, the corresponding relation between the projection radial dimension at the reference position and the actual radial reference dimension can be obtained. And shooting a projection image at the thread by using the machine vision measurement module, performing high-point straight line fitting based on the projection image at the thread to obtain a thread large-diameter profile, and performing profile extraction based on the projection image at the reference position, so that the pixel distance between the thread large-diameter profile and the profile at the reference position can be calculated, the pixel distance is converted into an actual distance, and radial dimension data of the reference position is obtained by combining the radial dimension measurement module, so that the large-diameter value of the thread can be calculated. Similarly, the pitch diameter value of the thread can be calculated by determining the edge of the thread based on the projection image of the thread, calculating the pixel distance between the pitch diameter position and the large diameter position after finding the pitch diameter position, converting the pixel distance into the actual distance, and then collecting the large diameter value of the thread. According to the invention, by combining radial dimension measurement and projection measurement, the defects that axial details cannot be measured in radial dimension measurement and the radial resolution of projection measurement is insufficient are overcome, the measurement precision and the measurement range of a projection measurement method are improved, the screw thread parameter measurement with the precision of about 0.01 millimeter can be realized under the condition that the measurement shaft diameter is as high as one hundred millimeters, the detection requirements of large axial dimension span and high detail precision of long shaft parts of an aeroengine can be simultaneously met, and the non-contact optical detection is adopted, so that additional auxiliary setting cannot be realized, the screw thread measurement efficiency can be greatly improved, and the requirement of mass screw thread detection can be met.
In addition, the thread detection method suitable for the long shaft part of the aeroengine has the advantages.
In addition to the objects, features and advantages described above, the present invention has other objects, features and advantages. The present invention will be described in further detail with reference to the drawings.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention. In the drawings:
fig. 1 is a schematic structural view of a screw thread inspection device suitable for use with long shaft parts of an aircraft engine in accordance with a preferred embodiment of the present invention.
FIG. 2 is a schematic illustration of the placement of a machine vision measurement module offset from the center of rotation of a long axis part in accordance with a preferred embodiment of the present invention.
Fig. 3 is a schematic view of a projected image of a half of a long axis part taken by a machine vision measurement module according to a preferred embodiment of the present invention.
FIG. 4 is a schematic diagram of a calibration module according to a preferred embodiment of the present invention.
Fig. 5 is a schematic view of the intersection of a single-sided helical surface with a cutting plane in a preferred embodiment of the invention.
Fig. 6 is a schematic diagram of the compensation of occlusion distortion for a threaded projection image in accordance with a preferred embodiment of the present invention.
Fig. 7 is a flow chart of a thread inspection method for an aircraft engine long shaft part according to another embodiment of the invention.
Fig. 8 is another flow chart of a thread inspection method for an aircraft engine long shaft part according to another embodiment of the invention.
FIG. 9 is a flow chart of the compensation of occlusion distortion for threaded projection images in accordance with another embodiment of the present invention.
Description of the reference numerals
100. A radial dimension measurement module; 200. a machine vision measurement module; 300. a motion axis module; 400. a calibration module; 201. an imaging unit; 202. a light source unit; 301. a measuring shaft movement unit; 302. a clamping shaft movement unit; 303. a rotary table unit.
Detailed Description
Embodiments of the invention are described in detail below with reference to the attached drawing figures, but the invention can be practiced in a number of different ways, as defined and covered below.
It will be appreciated that as shown in fig. 1, the preferred embodiment of the present invention provides a screw thread detecting device suitable for long shaft parts of an aeroengine, which includes a radial dimension measuring module 100, a machine vision measuring module 200, a motion shaft module 300 and a control module (not shown), wherein the radial dimension measuring module 100 is used for measuring any radial dimension of the long shaft parts, the machine vision measuring module 200 is used for shooting projection images of the long shaft parts in a radial direction, and the motion shaft module 300 is used for driving the radial dimension measuring module 100 and the machine vision measuring module 200 to move along an axial direction of the long shaft parts and also is used for axially positioning and clamping the long shaft parts. The control module is electrically connected with the radial dimension measuring module 100, the machine vision measuring module 200 and the moving axis module 300, and is generally an upper computer, and is configured to control the moving axis module 300 to drive the radial dimension measuring module 100 to move to any optical axis position on the long axis part, measure the radial dimension at the reference position by taking the optical axis position as a reference, control the moving axis module 300 to drive the machine vision measuring module 200 to align with the reference position so as to capture a projection image at the reference position, control the moving axis module 300 to drive the machine vision measuring module 200 to align with the screw thread and capture a projection image of the screw thread, and finally measure the radial dimension at the reference position by using the radial dimension measuring module 100 as a radial reference dimension, and calculate a large diameter value, a medium diameter value and a screw pitch of the screw thread by combining the projection image at the reference position captured by the machine vision measuring module 200 and the projection image of the screw thread. After the thread projection image is obtained, the control module carries out straight line fitting on high points in the image, so that a thread large diameter can be obtained, then the pixel distance between the fitting straight line and the outline of the projection image at the reference position is calculated, the actual distance is obtained through conversion, and the large diameter value of the thread can be calculated.
It can be understood that, in the thread detection device applicable to the long shaft part of the aeroengine of the present embodiment, with an arbitrary optical axis position on the long shaft part as a reference position, radial dimension data of the reference position is measured by the radial dimension measurement module 100, and the radial dimension data is used as an actual radial reference dimension for measuring the major diameter and the intermediate diameter of the thread. After the radial projection image at the reference position is photographed by the machine vision measurement module 200, the correspondence between the projected radial dimension at the reference position and the actual radial reference dimension can be obtained. And then shooting a projection image of the thread by using the machine vision measurement module 200, performing high-point straight line fitting based on the projection image of the thread to obtain a thread large-diameter profile, and performing profile extraction based on the projection image of the reference position, so that the pixel distance between the thread large-diameter profile and the profile of the reference position can be calculated, the pixel distance is converted into an actual distance, and radial dimension data of the reference position can be obtained by combining the radial dimension measurement module 100 to calculate the large-diameter value of the thread. Similarly, the thread edge is determined based on the projection image at the thread, after the pitch diameter position is found, the pixel distance between the pitch diameter position and the large diameter position is calculated and converted into the actual distance, the pitch diameter value of the thread can be calculated by collecting the large diameter value of the thread, the pitch diameter is the axial distance between two pitch diameter value measuring points, and the actual distance can be obtained after calibration conversion based on the pixel distance between the two pitch diameter value measuring points. According to the invention, by combining radial dimension measurement and projection measurement, the defects that axial details cannot be measured in radial dimension measurement and the radial resolution of projection measurement is insufficient are overcome, the measurement precision and the measurement range of a projection measurement method are improved, the screw thread parameter measurement with the precision of about 0.01 millimeter can be realized under the condition that the measurement shaft diameter is as high as one hundred millimeters, the detection requirements of large axial dimension span and high detail precision of long shaft parts of an aeroengine can be simultaneously met, and the non-contact optical detection is adopted, so that additional auxiliary setting cannot be realized, the screw thread measurement efficiency can be greatly improved, and the requirement of mass screw thread detection can be met.
It can be appreciated that the radial dimension measuring module 100 is a light curtain type shaft diameter measuring sensor, which is disposed at two sides of the long shaft part along the radial direction, and can measure the radial dimension of any position of the long shaft part, and provide a reference for measuring the major diameter and the intermediate diameter of the thread. The machine vision measurement module 200 includes an imaging unit 201 and a light source unit 202, where the imaging unit 201 and the light source unit 202 are disposed on two sides of the long shaft part in opposite directions along a radial direction, the imaging unit 201 is an industrial camera with a telecentric lens, an optical axis of the industrial camera is perpendicular to an axis of the long shaft part, and the telecentric lens is used for capturing a projection image, and the telecentric lens is used for receiving light generated by the light source unit 202 and ensuring that the received light is parallel incident, and the light source unit 202 is a parallel backlight and is used for generating stable and uniform light so as to ensure definition and accuracy of the projection image. Preferably, the center of the light curtain type shaft diameter measuring sensor is aligned with the rotation center of the long shaft part to be measured during installation, and the machine vision measuring module 200 is placed in an offset manner, that is, the visual field edge of the imaging unit 201 is aligned with the rotation center of the long shaft part, as shown in fig. 2. The structural layout mode has the advantages that the measuring range of the telecentric lens due to caliber limitation is not enough through the light curtain type shaft diameter measuring sensor, and the dead zone of the light curtain type shaft diameter measuring sensor, which cannot detect the fine features of the shaft shoulder due to the thickness of the light curtain, can be made up through the longitudinal resolution of the telecentric lens. Therefore, in the present invention, the machine vision measurement module 200 only needs to shoot the projection image of the half of the long axis part, as shown in fig. 3, then extracts the pixel position of the large diameter/medium diameter, compares the pixel position with the pixel position at the reference position, and combines the actual radial dimension at the reference position measured by the light curtain type axis diameter measurement sensor to calculate the large diameter value/medium diameter value, thereby realizing the high-speed, high-precision and multi-feature measurement of the long axis part through the complementation of the two sets of measurement systems.
Optionally, the motion axis module 300 is further configured to drive the long axis part to rotate, and the control module is further configured to control the motion axis module 300 to rotate for one circle, control the machine vision measurement module 200 to shoot at a preset angle at a fixed interval in a rotating process, obtain a plurality of thread projection images, and calculate a pitch diameter value of a thread in each thread projection image, thereby calculating pitch diameter runout of the thread. According to the invention, by adopting a rotary shooting mode, the thread pitch diameter runout detection is realized, and the measurement speed is greatly improved.
It will be appreciated that the motion axis module 300 includes a measurement axis motion unit 301, a clamping axis motion unit 302, and a rotation stage unit 303, the measurement axis motion unit 301 is disposed at two sides of the long axis part in a radial direction relatively and is movable in an axial direction, the radial dimension measurement module 100 and the machine vision measurement module 200 are fixedly mounted on the measurement axis motion unit 301, specifically, on the same slide carriage of the measurement axis motion unit 301, wherein the radial dimension measurement module 100 is mounted under the machine vision measurement module 200, and of course, in other embodiments of the present invention, the radial dimension measurement module 100 may be mounted above the machine vision measurement module 200. The measuring shaft moving unit 301 may be a linear driving mechanism such as an electric telescopic rod or a linear motor. The clamping shaft moving unit 302 is fixedly installed on the rotating table unit 303 and can move relatively along the axial direction, and is used for clamping and positioning long shaft parts axially, and the rotating table unit 303 is used for driving the clamping shaft moving unit 302 and the long shaft parts to rotate synchronously. The clamping shaft moving unit 302 comprises an upper clamping head and a lower clamping head, the lower clamping head is fixedly arranged on the rotary table unit 303, the upper clamping head is arranged on the rotary table unit 303 in an up-down adjustable mode, and the upper clamping head is controlled to move relatively towards the lower clamping head, so that two axial ends of a long shaft part are positioned and clamped. It will be appreciated that the rotary table unit 303 may be omitted when it is not necessary to detect thread pitch run out.
In addition, the thread detection device further comprises a calibration module 400 for performing image calibration by the machine vision measurement module 200. Optionally, as shown in fig. 4, the calibration module 400 is a checkerboard calibration board, which is used for calibrating the pixel size of the CCD, and the pixel size in the image is calculated and converted into the actual size, so that the conversion relationship between the pixel size and the actual size can be obtained by calibration.
It can be understood that for the shot screw projection image, because the optical axis of the CCD camera is perpendicular to the screw axis, shielding distortion is generated when screw projection enters the camera, the obtained screw edge is not a true contour on the axial section, and the selected pitch diameter position is inaccurate, so that the accuracy of the detection result of the pitch diameter value is poor. Therefore, a real image needs to be inverted on the basis of the distorted image to obtain a real thread section, so that accuracy in selecting the pitch diameter position is ensured, and measurement accuracy of the pitch diameter value is improved. Optionally, the control module is further configured to perform occlusion distortion compensation on the threaded projection image after obtaining the threaded projection image. The process of the control module for carrying out shielding distortion compensation on the threaded projection image comprises the following steps:
establishing a three-dimensional coordinate system by taking the rotation axis of the long-axis part as a z axis;
intersecting a cutting plane parallel to the xoz plane with the single-sided spiral surface to obtain a spiral curve;
obtaining an extremum by deriving a z-axis coordinate equation of the spiral curve to obtain an actually measured thread section profile;
and calculating a compensation value based on the actually measured thread cross section profile and the theoretical thread cross section profile, and performing shielding distortion compensation on the thread projection image based on the compensation value to obtain a real image.
Specifically, as shown in fig. 5, when a three-dimensional coordinate system oxyz is established with the rotation axis of the long-axis part as the z axis, the single-sided spiral surface can be expressed as:wherein phi represents the angle between the point on the single-sided helical surface in the xoy plane and the x-axis, P represents the pitch, d represents the major diameter of the thread, alpha represents the thread angle, t represents a variable parameter,d 1 representing the minor diameter of the thread.
In the present invention, the backlight is then projected in the x-direction, so that a cutting plane (y=d) parallel to the xoz plane intersects the single-sided spiral surface to give a spiral curve, which can be expressed as:wherein (1)>And is also provided with
It can be seen that z is a function of phi, and then the derivative of phi for z results:then, let z' =0, find the extremum, get:
the above formula is substituted into the equation of the spiral curve, so that the actual boundary point of the projection image can be obtained, that is, the thread profile actually measured by the machine vision measurement module 200 can be expressed as:
whereas the theoretical thread cross-sectional profile is:therefore, the compensation value is: Δz=z max -z real And performing shielding distortion compensation on the thread projection image based on the compensation value to obtain a real image, and selecting a real pitch diameter position point from the back-calculated real image to calculate the pitch diameter value of the thread as shown in fig. 6.
It can be understood that the working process of the thread detection device of the invention is specifically as follows:
the light source unit 202 is turned on to generate stable and uniform light, the imaging unit 201 is turned on, the calibration module 400 is clamped, the direction of the light source unit is made to be perpendicular to the optical axis of the industrial camera as much as possible through manual rotation, then the calibration plate image is photographed, the relation between the pixel size and the real size of the image is calculated through the distance between the checkerboard angular points, and then the calibration module 400 is dismounted. And then the upper clamping block in the clamping shaft moving unit 302 is controlled to move for clamping and positioning, and the long shaft part of the aero-engine is fixed on the rotating table unit 303.
Then, any optical axis position on the long axis part is selected as a reference position, and the measuring axis movement unit 301 is controlled to move axially, so that the light curtain type axis diameter measuring sensor is aligned with the reference position for measurement, and radial dimension data at the reference position are obtained.
The measuring axis moving unit 301 is controlled to move axially, so that the machine vision measuring module 200 shoots aiming at the reference position, a projection image of the reference position is obtained, and contour extraction is performed.
Then, the measuring axis moving unit 301 is controlled to move axially, so that the machine vision measuring module 200 photographs the thread to obtain a projection image of the thread and extract the contour. And performing straight line fitting on high points in the thread projection image to obtain a thread major diameter, then calculating the pixel distance between the profile at the thread major diameter and the profile at the reference position, and converting the pixel distance into an actual distance through a calibration result to obtain a major diameter value of the thread.
Then, carrying out shielding distortion compensation on the shot thread image to obtain a real image, selecting a real pitch diameter position, converting to obtain an actual distance based on the pixel distance between the pitch diameter position and the large diameter position, and calculating to obtain the pitch diameter value of the thread by combining the large diameter value of the thread, wherein the axial distance between two pitch diameter position points is the pitch diameter.
Then, the turntable unit 303 is controlled to start, the turntable is controlled to rotate 360 degrees, one photo is taken every n degrees (n is generally less than 1), 360/n photos are taken in total, and the pitch diameter value of the thread measured in each photo is calculated, so that the pitch diameter runout value can be calculated.
And finally, comparing the measured large diameter value, pitch diameter runout value with a preset threshold value so as to judge whether the thread processing quality meets the requirement, and outputting the measurement result to display equipment or exporting data to data storage equipment.
In addition, as shown in fig. 7, another embodiment of the present invention further provides a thread detection method suitable for a long shaft part of an aeroengine, preferably adopting the thread detection device as described above, the method comprising the following steps:
step S1: controlling the motion axis module to drive the radial dimension measuring module to move to any optical axis position on the long axis part, and measuring to obtain the radial dimension at the reference position by taking the optical axis position as a reference;
step S2: controlling the motion axis module to drive the machine vision measuring module to align with the reference position so as to shoot a projection image at the reference position;
step S3: controlling the motion axis module to drive the machine vision measuring module to align with the threads and shooting projection images of the threads;
step S4: and the radial dimension measuring module is used for measuring the radial dimension at the reference position to serve as the radial reference dimension, and the large diameter value, the middle diameter value and the screw pitch of the screw thread are calculated by combining the projection image at the reference position and the projection image of the screw thread shot by the machine vision measuring module.
It can be understood that in the thread detection method applicable to the long shaft part of the aeroengine in this embodiment, an arbitrary optical axis position on the long shaft part is taken as a reference position, radial dimension data of the reference position is measured by using a radial dimension measurement module, and the radial dimension data is taken as an actual radial reference dimension for measuring a major diameter and a middle diameter of the thread. After the radial projection image at the reference position is shot by the machine vision measuring module, the corresponding relation between the projection radial dimension at the reference position and the actual radial reference dimension can be obtained. And shooting a projection image at the thread by using the machine vision measurement module, performing high-point straight line fitting based on the projection image at the thread to obtain a thread large-diameter profile, and performing profile extraction based on the projection image at the reference position, so that the pixel distance between the thread large-diameter profile and the profile at the reference position can be calculated, the pixel distance is converted into an actual distance, and radial dimension data of the reference position is obtained by combining the radial dimension measurement module, so that the large-diameter value of the thread can be calculated. Similarly, the thread edge is determined based on the projection image at the thread, after the pitch diameter position is found, the pixel distance between the pitch diameter position and the large diameter position is calculated and converted into the actual distance, the pitch diameter value of the thread can be calculated by collecting the large diameter value of the thread, the pitch diameter is the axial distance between two pitch diameter value measuring points, and the actual distance can be obtained after calibration conversion based on the pixel distance between the two pitch diameter value measuring points. According to the invention, by combining radial dimension measurement and projection measurement, the defects that axial details cannot be measured in radial dimension measurement and the radial resolution of projection measurement is insufficient are overcome, the measurement precision and the measurement range of a projection measurement method are improved, the screw thread parameter measurement with the precision of about 0.01 millimeter can be realized under the condition that the measurement shaft diameter is as high as one hundred millimeters, the detection requirements of large axial dimension span and high detail precision of long shaft parts of an aeroengine can be simultaneously met, and the non-contact optical detection is adopted, so that additional auxiliary setting cannot be realized, the screw thread measurement efficiency can be greatly improved, and the requirement of mass screw thread detection can be met.
Optionally, as shown in fig. 8, the thread detection method further includes the following:
step S5: and controlling the motion axis module to drive the long shaft part to rotate for one circle, controlling the machine vision measurement module to shoot at a preset angle at fixed intervals in the rotating process, obtaining a plurality of thread projection images, and calculating to obtain the pitch diameter value of the threads in each thread projection image, so as to calculate to obtain pitch diameter runout of the threads.
Optionally, in the step S3, after obtaining the projection image of the thread, the following is further included:
and performing shielding distortion compensation on the threaded projection image.
As shown in fig. 9, the process of performing the shielding distortion compensation on the threaded projection image specifically includes:
step S31: establishing a three-dimensional coordinate system by taking the rotation axis of the long-axis part as a z axis;
step S32: intersecting a cutting plane parallel to the xoz plane with the single-sided spiral surface to obtain a spiral curve;
step S33: obtaining an extremum by deriving a z-axis coordinate equation of the spiral curve to obtain an actually measured thread section profile;
step S34: and calculating a compensation value based on the actually measured thread cross section profile and the theoretical thread cross section profile, and performing shielding distortion compensation on the thread projection image based on the compensation value to obtain a real image.
It may be understood that the method embodiment corresponds to the apparatus embodiment described above, and specific execution of each step of the method may refer to the description of the apparatus embodiment described above, which is not repeated herein.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. Screw thread detection device suitable for aeroengine major axis part, characterized in that includes:
a radial dimension measurement module (100) for measuring any radial dimension of the long shaft part;
the machine vision measurement module (200) is used for shooting projection images of the long-axis part in the radial direction;
the motion shaft module (300) is used for driving the radial dimension measuring module (100) and the machine vision measuring module (200) to move along the axial direction of the long shaft part and is also used for axially positioning and clamping the long shaft part;
the control module is electrically connected with the radial dimension measuring module (100), the machine vision measuring module (200) and the moving shaft module (300), and is used for controlling the moving shaft module (300) to drive the radial dimension measuring module (100) to move to any optical axis position on a long shaft part, measuring the radial dimension at the reference position by taking the optical axis position as a reference, controlling the moving shaft module (300) to drive the machine vision measuring module (200) to align with the reference position so as to shoot a projection image at the reference position, controlling the moving shaft module (300) to drive the machine vision measuring module (200) to align with a thread and shoot a projection image of the thread, finally taking the radial dimension at the reference position measured by the radial dimension measuring module (100) as the radial reference dimension, and calculating a large diameter value, a medium diameter value and a pitch of the thread by combining the projection image at the reference position shot by the machine vision measuring module (200) and the projection image of the thread.
2. The thread detection device for long shaft parts of aeroengines according to claim 1, wherein the motion shaft module (300) is further used for driving the long shaft parts to rotate, the control module is further used for controlling the motion shaft module (300) to rotate for one circle, and controlling the machine vision measurement module (200) to shoot at a preset angle at fixed intervals in the rotating process, so as to obtain a plurality of thread projection images, and calculating the pitch diameter value of threads in each thread projection image, so as to calculate pitch diameter runout of the threads.
3. The thread inspection device for long shaft parts of aeroengines according to claim 1, wherein the radial dimension measurement module (100) is a light curtain type shaft diameter measurement sensor which is oppositely arranged at two sides of the long shaft parts along the radial direction, the machine vision measurement module (200) comprises an imaging unit (201) and a light source unit (202), the imaging unit (201) and the light source unit (202) are oppositely arranged at two sides of the long shaft parts along the radial direction, the imaging unit (201) is an industrial camera matched with a telecentric lens, the light source unit (202) is a parallel backlight, the center of the light curtain type shaft diameter measurement sensor is aligned with the rotation center of the long shaft parts, and the visual field edge of the imaging unit (201) is aligned with the rotation center of the long shaft parts.
4. The thread inspection device for long shaft parts of aero-engines according to claim 1, wherein the control module is further configured to perform occlusion distortion compensation on the threaded projection image after obtaining the threaded projection image.
5. The thread detection device for long shaft parts of aero-engine according to claim 4, wherein the process of the control module for performing shielding distortion compensation on the thread projection image is as follows:
establishing a three-dimensional coordinate system by taking the rotation axis of the long-axis part as a z axis;
intersecting a cutting plane parallel to the xoz plane with the single-sided spiral surface to obtain a spiral curve;
obtaining an extremum by deriving a z-axis coordinate equation of the spiral curve to obtain an actually measured thread section profile;
and calculating a compensation value based on the actually measured thread cross section profile and the theoretical thread cross section profile, and performing shielding distortion compensation on the thread projection image based on the compensation value to obtain a real image.
6. The thread inspection device for aircraft engine long shaft parts according to claim 1, further comprising a calibration module (400) for image calibration by the machine vision measurement module (200).
7. The thread detection device for long shaft parts of aeroengines according to claim 2, wherein the movement shaft module (300) comprises a measurement shaft movement unit (301), a clamping shaft movement unit (302) and a rotating table unit (303), the measurement shaft movement unit (301) is relatively arranged at two sides of the long shaft parts in the radial direction and can move along the axial direction, the radial dimension measurement module (100) and the machine vision measurement module (200) are fixedly arranged on the measurement shaft movement unit (301), the clamping shaft movement unit (302) is fixedly arranged on the rotating table unit (303) and can move relatively along the axial direction for axially clamping and positioning the long shaft parts, and the rotating table unit (303) is used for driving the clamping shaft movement unit (302) and the long shaft parts to synchronously rotate.
8. A thread detection method suitable for long shaft parts of aeroengines, adopting the thread detection device as claimed in any one of claims 1 to 7, characterized by comprising the following contents:
the control movement axis module (300) drives the radial dimension measuring module (100) to move to any optical axis position on the long axis part, and the radial dimension at the reference position is measured by taking the optical axis position as a reference;
controlling the motion axis module (300) to drive the machine vision measurement module (200) to align with the reference position so as to shoot a projection image at the reference position;
controlling the motion axis module (300) to drive the machine vision measurement module (200) to align the threads and shoot projection images of the threads;
the radial dimension at the reference position is measured by a radial dimension measuring module (100) to be used as a radial reference dimension, and the large diameter value, the middle diameter value and the screw pitch of the screw thread are calculated by combining the projection image at the reference position and the projection image of the screw thread shot by a machine vision measuring module (200).
9. The thread inspection method for aircraft engine long shaft parts according to claim 8, further comprising the following:
the motion axis control module (300) drives the long shaft part to rotate for one circle, the machine vision measurement module (200) is controlled to shoot at a preset angle at fixed intervals in the rotating process, a plurality of thread projection images are obtained, and the pitch diameter value of threads in each thread projection image is obtained through calculation, so that pitch diameter runout of the threads is obtained through calculation.
10. The thread inspection method for aircraft engine long shaft parts according to claim 8, further comprising, after obtaining the projection image of the thread:
and performing shielding distortion compensation on the threaded projection image.
CN202311061389.6A 2023-08-22 2023-08-22 Thread detection device and method suitable for long shaft part of aero-engine Pending CN117288062A (en)

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CN202311061389.6A CN117288062A (en) 2023-08-22 2023-08-22 Thread detection device and method suitable for long shaft part of aero-engine

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Application Number Priority Date Filing Date Title
CN202311061389.6A CN117288062A (en) 2023-08-22 2023-08-22 Thread detection device and method suitable for long shaft part of aero-engine

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