CN112001911B

CN112001911B - Needle missing detection method based on double-purpose double-row needle roller bearing

Info

Publication number: CN112001911B
Application number: CN202010871027.3A
Authority: CN
Inventors: 冯春; 姜文彪; 武之炜; 赵彻; 张祎伟; 周叙荣
Original assignee: Changzhou Institute of Technology
Current assignee: Changzhou Institute of Technology
Priority date: 2020-08-26
Filing date: 2020-08-26
Publication date: 2023-10-27
Anticipated expiration: 2040-08-26
Also published as: CN112001911A

Abstract

The invention discloses a double-row needle bearing needle missing detection method based on double purposes. The invention applies the machine vision to the needle deficiency detection of the double-row needle roller bearing, avoids the problems of high working strength, time and labor consumption of a manual measurement mode, and simultaneously avoids the problem of poor universality of contact measurement. The method not only can be used as a needle missing detection means of the double-row needle roller bearing, but also is suitable for the problems of needle missing detection, size, accurate positioning and the like of other needle roller bearings, and has good universality. As a flexible detection means, the double-row needle bearing needle lack detection device and method based on machine vision can be very conveniently transplanted to other related application fields such as detection, identification, classification and the like.

Description

Needle missing detection method based on double-purpose double-row needle roller bearing

Technical Field

The invention relates to a detection method for needle missing condition of a needle bearing, in particular to a double-row needle bearing needle missing detection method based on vision.

Background

Needle bearings are needle bearings with cylindrical rollers, and in general the diameter of the bearing itself is much larger than the diameter of the rollers. The double row roller bearing is a cylindrical roller (shown in fig. 1) comprising an upper layer and a lower layer, and the production and the installation process of the double row roller bearing are more complex than those of the single row needle roller bearing. During production, the rollers are typically arranged in fixed positions on the upper and lower layers using mechanical means. However, due to uncertainty in the manufacturing and assembly process, it sometimes happens that the rollers are not mounted in a given position or that some or even some of the rollers are missing (so-called missing needles). When a needle deficiency occurs, the bearings need to be sorted out and reloaded into the missing rollers and then the next bearing manufacturing process is performed. In the detection method of the needle deficiency, a common bearing manufacturer adopts a manual method for detection, and the method is time-consuming, labor-consuming and high in working strength, and has the risk of missed detection due to limited energy of people.

Aiming at the problem of needle leakage of the bearing, the related patent proposes that the bearing with a certain difference between the weight and the normal needle bearing is the bearing with a needle missing function by weighing the bearing after the frame is assembled. The detection method requires high weighing precision, and particularly for bearings with small size and light weight, the measuring precision of the weighing device must be capable of achieving the purpose of distinguishing a single needle roller. The hardware cost of the corresponding device of the method is high, and the method is sensitive to environmental changes, so that the measurement precision is difficult to ensure, and the accuracy of needle missing detection is affected; in addition, a probe detection apparatus and method are disclosed. The needle lack detection mechanism of the method comprises a linear displacement sensor and a controller, wherein a probe is arranged at the sliding end of the linear displacement sensor and is used for penetrating into a needle roller clearance of a needle roller bearing on the bearing conveying channel. The diameter of the probe is larger than one half of the diameter of the needle roller and smaller than the diameter of the needle roller, and whether the needle roller is in a missing state or is assembled according to requirements is judged by judging the deep distance of the probe. The judgment basis of the method is that the difference between the penetration distance under the condition of needle lack and the penetration distance when the needle roller is full is large, and the judgment can be carried out without high-precision detection. However, it has the following problems as a method of contact measurement: 1) The machining precision requirement of the probe is high, and the machining precision is difficult to ensure especially under the condition of small needle roller diameter; 2) The probe can only detect the current needle bearing, and if bearings with different diameter sizes need to be detected, the universality is poor. In order to avoid the problems, the invention provides a machine vision-based method for solving the problem of needle deficiency of double-row needle bearings. The method comprises the steps of utilizing a binocular camera to collect images of needle bearings in a certain direction, and utilizing an image processing method to judge whether the number of obtained needle imaging subareas is matched with the number of actual needle rollers or not so as to judge whether the needle is in shortage or not.

Disclosure of Invention

The invention aims to solve the technical problems of needle deficiency detection of double-row needle bearings, and the existing manual detection and contact detection methods have the defects of high labor intensity, high processing difficulty, poor detection flexibility and the like. In order to solve the technical problems, the invention provides a double-row needle bearing needle missing detection method based on a double-purpose machine vision method.

In order to achieve the above purpose, the present invention provides the following technical solutions:

the needle missing detection method based on the double-purpose double-row needle roller bearing comprises the following steps:

step S1: initializing, setting a value of a counter count, wherein the value of the counter count is set to be M1 when one camera of the binocular camera performs needle missing detection on a row of needle rollers close to one side of the needle roller bearing, and is set to be M2 when the other camera of the binocular camera performs needle missing detection on a row of needle rollers close to the one side of the needle roller bearing;

step S2: adopting a binocular camera to collect images of the needle roller bearing;

step S3: extracting independent subareas of the rolling needle through threshold segmentation; meanwhile, acquiring a ring area of the bearing through threshold segmentation, extracting edges to obtain the outer and inner boundaries of the ring, and further fitting an inner circle and an outer circle by using Hough transformation to obtain the contours of the inner circle and the outer circle;

step S4: comparing the number N1 of the independent needle roller subareas of the area outside the outer circle with the number N0 of the needle roller;

if n1=n0, step S5 is performed; if n1 is not equal to N0, comparing the sum of the numbers N2 and N1 of the needle rollers with pixel intersections in the inner independent subarea and the inner circle with the size of N0, if n1+n2=n0, executing step S5, if n1+n2 is not equal to N0, judging that the bearing lacks the needle, removing the bearing and reassembling the needle rollers, and executing steps S1-S4 again;

step S5: judging the value of a counter;

if count=m1, the current detection is the first detection of the double row needle roller of the bearing, and under the condition of no needle missing, setting the value of the counter count to be M2, and re-executing the steps S2-S5; if count=m2, the current test is a second test of the double row needle roller of the bearing, and the bearing is transferred to the next process without missing needle.

Further, in the step S2, the binocular camera acquires an image of the needle bearing under the action of the active light source.

Further, the active light source is a ring light source.

Further, the value of M1 is 0, and the value of M2 is 1.

Further, the secondary detection using the binocular camera includes: shooting from above by a first camera and a first light source for the first time, wherein an imaged needle roller row is a row above a bearing; the second time is to shoot the bearing from the lower part through the transparent body by the second camera and the second light source, and the imaging roller needle row is one row below the bearing.

Further, a black background is arranged directly above the bearing.

Compared with the prior art, the invention has the beneficial effects that:

the invention applies the machine vision to the needle deficiency detection of the double-row needle roller bearing, avoids the problems of high working strength, time and labor consumption of a manual measurement mode, and simultaneously avoids the problem of poor universality of contact measurement. The method not only can be used as a needle missing detection means of the double-row needle roller bearing, but also is suitable for the problems of needle missing detection, size, accurate positioning and the like of other needle roller bearings, and has good universality. As a flexible detection means, the double-row needle bearing needle lack detection device and method based on machine vision can be very conveniently transplanted to other related application fields such as detection, identification, classification and the like.

Drawings

FIG. 1 is a pictorial view of a double row needle bearing;

FIG. 2 is a schematic structural view of a double row needle bearing needle missing visual inspection device;

FIG. 3 is a flow chart of needle failure detection for a double row needle bearing;

FIG. 4 is an original image taken of a double row needle bearing;

FIG. 5 is an extraction of the needle bearing rings and outer and inner circles;

FIG. 6 is needle bearing outer subarea detection;

FIG. 7 is a partial needle offset into an inner independent subregion;

FIG. 8 is a needle missing from the outer subregion of the needle bearing;

fig. 9 is an external and internal subregion extraction and needle deficiency detection.

Detailed Description

The present invention will be further described in detail below with reference to specific embodiments and with reference to the accompanying drawings, in order to make the objects, technical solutions and advantages of the present invention more apparent.

As shown in fig. 2, the key components of the double-row needle bearing needle lack visual detection device adopted by the invention comprise a double camera, a double light source, a black background and a detection piece. The detection idea is that a binocular camera is combined with an active light source (annular light source) to perform image acquisition and pretreatment on a bearing with a specific pose so as to judge whether the needle is in a shortage state. As a new detection method, the main steps are shown in figure 3, and the method comprises the steps of dividing the inside and the outside of the bearing, dividing and detecting independent subareas of the needle roller outside the bearing, dividing and detecting subareas of the needle roller inside the bearing, judging needle lack detection and the like.

The division of the bearing inner and outer portions is based on the outer and inner circles of the ring of the needle bearing shown in fig. 5 as the division of the bearing outer and inner portions. Since the needle is not mounted in a fixed position on the bearing without play, the play is instead sufficient to allow the needle to move. Thus, as can be seen from fig. 4, individual needles may be offset due to the gap in needle mounting, which may also be the case if the same needle is affiliated to an outer sub-area or an inner sub-area. In general, the needle is usually attached to the outer subarea under natural conditions, and the needle is attached to the inner subarea occasionally. The number of needles in the same needle bearing is generally fixed. Therefore, whether the needle is missing can be preliminarily judged by judging the number of the independent outer subareas. However, even if the number of individual outer subregions is less than the number of needles at full needle, the true needle deficiency cannot be accounted for, and the cause of this may be that the needles shift to become inner subregions. In addition, since the needle bearings are double-row, it can be seen from fig. 4 that the inner subregions of the needle bearings can be divided into two types. One is an inner subregion formed by upper row needle rollers, these subregions have intersections of pixel points with the inner wall of the needle roller bearing (subregions within small rectangles in the figure); the other is an inner subregion formed by the lower row of needle rollers, which subregions have no intersection of pixel points with the inner wall of the needle roller bearing (subregions within small triangles in the figure). Therefore, it is necessary to distinguish whether the first case or the second case is determined in the inner sub-region. Further, due to the pose imaging relationship of the camera and the bearing, one row of needle rollers close to the camera lens can block imaging of the other row of needle rollers far away from the camera lens. This results in the possible missed detection problem due to the shielding of the upper row of needles even if the lower row of needles are missing. Therefore, the invention adopts the binocular camera to carry out secondary detection (the device structure is shown in figure 2): the 1 st time is shooting from the upper part by a camera 1 and a light source 1, and the imaged needle roller row is a row above the bearing; the 2 nd time is to shoot the bearing from the lower part through the transparent body by the camera 2 and the light source 2, and the imaging roller needle row is a row below the bearing. For simplicity of imaging the background, a black background is arranged directly above the bearing. And combining the needle deficiency judging results of 1 and 2 times to finish the needle deficiency detection of the double-row needle rollers.

Specifically, the method comprises the following steps:

step 1:

the initialization is mainly the parameter initialization of various hardware and software systems, so that the detection system is in a normal working state and starts working. The working device comprises: camera, light source, bearing conveyor, image acquisition and image processing system, etc. The camera is installed to ensure that the optical axis of the camera and the rotating shaft of the bearing are in the coaxial direction as much as possible, so that the collected single image can image all the roller pins on the bearing closest to the camera lens. Only if the row of needle rollers arranged on the bearing can image on the image, the true needle missing or false judgment of the bottom bearing can be accurately judged. A counter count is mentioned here in particular, which parameter is used to determine which row of needles is to be detected for the bearing. When detecting a certain needle bearing, describing that a row of needle rollers close to a camera 1 detect a needle lack when count=0; when count=1, a row of needle rollers near the lens of the camera 2 is described to detect the missing needle. This is also a numerical description of the different positions and camera detection required to be performed when a double row needle bearing detection is performed with a binocular camera.

Step 2:

and acquiring an image of the needle bearing. In this step, the corresponding camera captures images of the needle bearing under the action of the light source. The light source is mainly added to ensure the imaging quality, and excessive noise is avoided from being introduced under the natural light condition, so that the subsequent image preprocessing is utilized. An example of the acquired image is shown in fig. 4, from which it can be seen that the needle roller portion is easily distinguished from the background and other portions of the bearing due to the higher brightness. However, since the needle roller is partially shielded by the bearing mount, the bright portion thereof is imaged as a "partial circle" region. Initially, each "partial circle" region corresponds to substantially 1 needle roller, and the number of needle rollers can be determined according to the number of independent regions. The image acquisition speed is determined according to the conveying speed of the bearings, and the image acquisition speed can be ensured to be timely and accurately acquired when each bearing is conveyed to a specified position. The acquired image ensures as high imaging quality as possible, a simple background and a comprehensive prospect.

Step 3:

image thresholding. The step is mainly to perform image preprocessing based on the image acquired in the previous step to obtain needle roller information. The threshold segmentation is to segment the foreground and background with appropriate gray values to obtain the region of interest. The determination of the threshold value may be obtained experimentally, the principle of which is to separate the region of interest from the non-region of interest as much as possible. Because the brightness value is higher, namely the gray value is larger after the needle roller imaging, each needle roller of the needle roller bearing is extracted as an independent subarea after threshold segmentation. Meanwhile, as can be seen from fig. 4, the ring region of the bearing is also obtained by threshold segmentation, the outer and inner boundaries of the ring are obtained by edge extraction, and the hough transform is further used for fitting the inner circle and the outer circle. Through the processing, the circular ring area, the inner circle and the outer circle outline of the bearing are obtained by using the methods of area extraction and boundary extraction and circle fitting.

Step 4:

this step is a main step of judging the number of needle rollers. Because the installation position of the needle roller has a certain gap, the needle roller can move so that the imaging subarea of the needle roller can possibly appear in an area outside the outer circle (a white 'small rectangular' area shown in fig. 6) or an area inside the inner circle (a subarea in a white rectangular frame shown in fig. 7), and the difficulty of judging whether the needle is in a missing state of the bearing is increased. The invention divides the conditions of needle deficiency detection into 2 types: 1, judging the number of independent needle roller subareas in the area outside the outer circle; and 2, judging by combining the number of the independent needle roller subareas with pixel intersections of the inner region and the inner circle on the basis of judging of 1.

Step 4.1:

based on the above steps, the outer circle of the bearing annular region and the outer independent sub-region of the needle roller can be determined. In order to judge whether the needle is missing, the number of the external independent subregions of the needle roller is calculated firstly, is assumed to be N1, and then the number of the external independent subregions of the needle roller is compared with the number N0 of the needle roller. If n1=n0, the number of the detected needle rollers is proved to be equal to the actual number of the needle rollers, and at the moment, the current row of the needle rollers of the bearing can be judged to have no needle missing phenomenon. Further, whether the detection of the single row needle roller or the detection of the double row needle roller is completed can be determined by judging the value of the counter count. If count=0, the current detection is the first detection of the double-row needle roller of the bearing, and the second detection is needed to determine whether the needle is missing or not; if count=1, it is described that the current detection is the second detection of the double row needle roller of the bearing and the situation of no needle missing, and the phenomenon that the bearing does not have needle missing can be known by the judgment of no needle missing in the above 2 detections. At this point, the bearing may be transferred to the next process for subsequent assembly or other work. And simultaneously, returning to an initialized state, resetting the counter count, and re-entering the needle lack detection judgment of the next bearing.

Step 4.2:

on the basis of the steps, the number N2 of the inner circles of the bearing circular ring areas and the independent subareas inside the needle rollers with pixel intersection points can be determined. In order to judge whether the needle is missing, the number N1 of the independent subareas outside the needle roller is calculated, and the N1 plus N2 is compared with the number N0 of the needle roller. If n1+n2=n0, the number of the detected needle rollers is proved to be equal to the actual number of the needle rollers, and at the moment, the phenomenon that the needle is not in a shortage state in the current row of the needle rollers of the bearing can be judged. Further, whether the detection of the single row needle roller or the detection of the double row needle roller is completed can be determined by judging the value of the counter count. If count=0, the current detection is the first detection of the double-row needle roller of the bearing, and the second detection is needed to determine whether the needle is missing or not; if count=1, it is described that the current detection is the second detection of the double row needle roller of the bearing and the situation of no needle missing is the present detection, and the phenomenon that the bearing does not have needle missing can be known through the judgment of no needle missing in the second detection. At this point, the bearing may be transferred to the next process for subsequent assembly of the bearing or other work. And returning the running program to the initialized state, resetting the counter count, and re-entering the needle deficiency detection judgment of the next bearing.

Step 5:

in the above steps, if the number N1 of the outer independent subregions determined by the outer circle boundary is not equal to the number N0 of the needle rollers (the number N2 of the pixel intersections between the inner independent subregions and the inner circle is not equal to the number N1 of the needle rollers (the number N0 of the needle rollers of the rectangular box is not detected in both the inner and outer parts of the needle rollers shown in fig. 9), the condition that the needle is missing in the bearing is indicated, that is, the problem that the needle rollers are unqualified is solved. At the moment, the needle missing bearing is removed and the needle roller is reinstalled, so that the needle missing position can be covered by the needle roller. And simultaneously, the running program returns to an initialized state, resets a counter count, and reenters the needle missing detection of the next bearing.

While the foregoing is directed to embodiments of the present invention, other and further details of the invention may be had by the present invention, it should be understood that the foregoing description is merely illustrative of the present invention and that no limitations are intended to the scope of the invention, except insofar as modifications, equivalents, improvements or modifications are within the spirit and principles of the invention.

Claims

1. The needle lack detection method based on the double-purpose double-row needle roller bearing is characterized by comprising the following steps of:

step S5: judging the value of a counter;

if count=m1, the current detection is the first detection of the double-row needle bearing, and the situation of no needle missing exists, setting the value of the counter count to M2, and re-executing the steps S2-S5; if count=m2, the current test is a second test of a double row needle bearing, which is transferred to the next process without missing needles.

2. The method for detecting needle deficiency based on double-purpose double-row needle bearings according to claim 1, wherein in the step S2, the double-purpose camera collects images of the needle bearings under the action of the active light source.

3. The dual-purpose double-row needle bearing-based needle deficiency detection method according to claim 2, wherein the active light source is an annular light source.

4. The dual-purpose double-row needle bearing needle deficiency detection method according to claim 1, wherein the value of M1 is 0, and the value of M2 is 1.

5. The dual-purpose double-row needle bearing-based needle deficiency detection method according to claim 1, wherein the performing of the secondary detection by using the dual-purpose camera comprises: shooting from above by a first camera and a first light source for the first time, wherein an imaged needle roller row is a row above a bearing; the second time is to shoot the bearing from the lower part through the transparent body by the second camera and the second light source, and the imaging roller needle row is one row below the bearing.

6. The dual-purpose double-row needle bearing-based needle deficiency detection method according to claim 5, wherein,

a black background is arranged directly above the bearing.