阅读说明：本技术 一种基于机器视觉的制孔及铆接质量控制方法及其装置 (Hole making and riveting quality control method and device based on machine vision ) 是由 郝博 王明阳 王鹏 郭嵩 闫俊伟 王杰 尹兴超 于 2021-08-03 设计创作，主要内容包括：本发明公开了一种基于机器视觉的制孔及铆接质量控制方法及其装置,该装置通过第一滑台、第二滑台、第一滑块、第二滑块、连杆联动可实现CCD相机对工件上平面孔或曲面孔的拍摄,并通过灰度处理、中值滤波、阈值分割、边缘提取、最小二乘法拟合等操作来检测孔的直径和圆度,结构稳固、自动化程度高、操作简单、检测精度高,在对曲面孔进行检测时可避免失真；该方法基于工程计算法,在考虑镦头端面摩擦力对正应力影响的情况下得出压铆力与镦头尺寸的关系模型,给工人配备过程监控铆枪来通过压铆力间接控制镦头尺寸,压铆质量控制精度高,可以实现及时发现、及时补救,避免误差累积,从而提高压铆质量和效率。(The invention discloses a hole making and riveting quality control method and a device thereof based on machine vision, the device can realize the shooting of a CCD camera to a plane hole or a curved hole on a workpiece through the linkage of a first sliding table, a second sliding table, a first sliding block, a second sliding block and a connecting rod, and detect the diameter and the roundness of the hole through the operations of gray processing, median filtering, threshold segmentation, edge extraction, least square fitting and the like, the device has the advantages of stable structure, high automation degree, simple operation and high detection precision, and can avoid distortion when the curved hole is detected; the method is based on an engineering calculation method, a relation model of the riveting force and the size of the upset is obtained under the condition that the influence of the friction force of the end face of the upset on the normal stress is considered, a process monitoring riveter is provided for workers to indirectly control the size of the upset through the riveting force, the control precision of the riveting quality is high, timely discovery and timely remediation can be realized, the error accumulation is avoided, and the riveting quality and efficiency are improved.)

1. A hole making and riveting quality control method and device based on machine vision are characterized in that: the technical architecture for realizing the hole making and riveting quality control comprises a hole center aligning stage, an original image acquisition stage, an image processing stage and an upset head quality monitoring stage, and specifically comprises the following steps: (1) the first sliding table, the second sliding table, the first sliding block, the second sliding block and the connecting rod are linked to realize that the CCD camera is aligned with a plane hole or a curved surface hole on the workpiece; (2) the fine adjustment of the positions of the first sliding block, the second sliding block and the connecting rod is used for realizing the alignment of the conical head on the revolving frame to the center of the plane hole or the curved hole; (3) then, the CCD camera is aligned to the center of the hole by rotating the revolving frame for 180 degrees and locking the position, and shooting is carried out; (4) detecting the diameter and the roundness of the hole through gray processing, median filtering, threshold segmentation, edge extraction, least square fitting processing and a MajorAxisLength command based on the shot original picture; (5) according to the detected aperture, a relation model of the riveting force and the size of the upset head is utilized to indirectly monitor whether the size of the upset head is qualified or not by monitoring the riveting force, so that the size of the upset head is controlled, and the quality of the upset head and even the quality of the riveting are improved; (6) and (3) in the actual riveting assembly process, the steps (1) to (5) are circulated until all holes in the workpiece are detected and the quality and the guarantee of the riveting work are finished.

2. The utility model provides a system hole and riveting quality control device based on machine vision which characterized in that: the lower end of the box body is provided with a support leg, one side of the box body is provided with a box door, the inner side of the box body is provided with a drawer and a controller, the upper end of the drawer is provided with a computer, the box body is provided with a groove block close to one side of the box door, the upper end of the box body is provided with a base, the upper end of the base is provided with a first linear guide rail, the upper end of the first linear guide rail is provided with a first sliding table, the upper end of the first sliding table is provided with a second linear guide rail, the upper end of the second linear guide rail is provided with a second sliding table, the inner side of the second sliding table is provided with a glass plate, the second sliding table is hollow, the glass plate is embedded into the second sliding table, the lower end of the glass plate is provided with a green light lamp, the upper end of the glass plate is provided with the workpiece, the front side of the base is provided with a stand column, the rear end of the stand is provided with a measuring head, and the measuring head is provided with a first lifting lug, a lead screw mounting seat is arranged on the inner side of the first lifting lug, a lead screw is arranged at the lower end of the lead screw mounting seat, a guide plate is arranged at the front end of the lead screw, the first sliding block is arranged on the outer side of the lead screw, a rotary frame mounting seat is arranged at the rear end of the first sliding block, the rotary frame is arranged at the lower end of the rotary frame mounting seat, a baffle is arranged in a groove of the rotary frame, a push rod mounting seat is arranged at the lower end of the rotary frame, a push rod is arranged at the lower end of the push rod mounting seat, the conical head is arranged at the lower end of the push rod, a camera mounting seat is arranged at the lower end of the rotary frame opposite to the other side of the push rod mounting seat, the CCD camera is arranged on the inner side of the camera mounting seat, white light lamps are arranged around the CCD camera, a second lifting lug is arranged at the lower end of the guide plate, a bolt is arranged on the inner side of the second lifting lug, and a slide rail is arranged on the front side of the guide plate, the inner side of the sliding rail is provided with the second sliding block, and the connecting rod is arranged on the second sliding block.

3. A machine vision based hole making and riveting quality control device as claimed in claim 2, wherein: when examining, the chamber door can be opened, pulls out the drawer can use the computer is handled the picture that the CCD camera gathered can push when the instrument finishes using the back the drawer, correspond on the chamber door the position of recess piece has inlayed magnet, can with the recess piece is inhaled tightly, thereby closes tightly the chamber door, when the device is located ambient light dark, through the white light provides the light source, when light is bright, through the green glow lamp provides the light source, thereby improves the definition of picture.

4. A machine vision based hole making and riveting quality control device as claimed in claim 2, wherein: the computer acquires the pictures acquired by the CCD camera, and then the hole contour is obtained by sequentially performing gray processing, median filtering processing, threshold segmentation and edge extraction, wherein during edge extraction, interference points in the pictures are removed by using bweareaopen and imdilate commands in MATLAB, the inner hole edge and the outer hole edge are extracted by using a Canny algorithm, then a contour curve of the hole is fitted by using a least square method, and finally the lengths of a long axis and a short axis of the contour curve of the hole are measured by using a MajorAxisLength command, so that the diameter and the roundness of the hole are measured.

5. A machine vision based hole making and riveting quality control device as claimed in claim 2, wherein: first linear guide can drive first slip table is preceding, the back removes, second linear guide can drive second slip table is left and right to be removed, first slider can pass through the lead screw drives the upper and lower removal of revolving rack mount pad, just first slider with the lead screw can the auto-lock, when only receiving the action of gravity, first slider can not move down, first linear guide second linear guide first slider by controller control removes.

6. A machine vision based hole making and riveting quality control device as claimed in claim 2, wherein: the groove of the revolving frame and the groove on the revolving frame mounting seat can be inserted into the baffle when being collinear, when the baffle is pulled out, the revolving frame can rotate in the revolving frame mounting seat, when the baffle is inserted, the revolving frame is locked, and the distances from the optical centers of the conical head and the CCD camera to the revolving center of the revolving frame are equal.

7. A machine vision based hole making and riveting quality control device as claimed in claim 2, wherein: the second sliding block is provided with magnetic force and can control the size of the magnetic force through a knob, after the bolt is pulled out, the second sliding block drives the connecting rod to move through moving in the sliding rail, the connecting rod pushes the guide plate to swing, and when the guide plate swings to a certain angle, the magnetic force of the second sliding block is set to be the maximum, so that the current position is locked.

8. A hole making and riveting quality control method based on machine vision is characterized in that: during riveting, the process of forming an upset head by the nail rod can be regarded as upsetting of the cylinder along the axis, and the deformation process has the axial symmetry characteristic. In the upsetting stage, the clinching force F gradually increases until it reaches a maximum value, the positive stress sigma acting on the upset_zThe shear stress tau of the contact surface of the heading and the punch is increased_fThe magnitude and distribution of (A) also directly influence the positive stress sigma_zThe distribution rule of (1). The research on the friction shear stress by combining the Umbersov shows that in the riveting process, the friction force area on the contact surface of the upset head and the punch comprises a stagnation area and a braking area, the friction stagnation area of the end surface of the cylinder is within the range of r being more than or equal to 0 and less than or equal to h, and the friction braking area is within the range of h being more than r and less than or equal to r_bSince the friction conditions adopted in each area are different, the obtained positive stress and riveting force of the contact surface are different, so that the riveting force F of the punch on the upset head is divided into two parts, and the riveting force F of the stagnation area and the braking area is recorded as F₁、F₂. The flat cone head rivet clinching process can be considered as axisymmetric upsetting, and therefore, there is a balance equation: from the infinitesimal nature of equivalenceAnd neglecting the influence of second-order trace, equation (1) can be simplified as: sigma_θhdr-2τ_frdr-σ_rhdr-rhdσ_r0(2) wherein σ represents_θFor positive circumferential stress, σ_rFor positive radial stress, τ_rThe friction shear stress of the contact surface of the punch and the nail rod, r is the radius of the upset head, dr is the differential of the radius of the upset head, and d sigma is_rIs the integral of the radial positive stress. Since the shank has been assumed to be deformed by uniform upsetting, σ_r＝σ_θThus, equation (2) is simplified as:the yield equation is still simplified by the absolute value column, since_r＝σ_θTherefore, the following are: sigma_z-σ_r＝Y(4)、dσ_z＝dσ_r(5) In the formula, σ_zIs the axial positive stress to which the nail rod is subjected. The combined vertical type (3) and (5) can obtain:in the friction braking area (h < r ≦ r_b)，τ_f＝0.5σ_sThe formula (6) can be substituted by:the indefinite integral on both sides of equation (7) can be found:(8) from frictional shear stress τ on the contact surface during upsetting of the cylinder_fThe distribution curve can be obtained when r is r_bWhen the temperature of the water is higher than the set temperature,therefore, it isCan be substituted by the formula (8): integration of equation (9) over the area of the friction braking zone can be found: in the friction stagnation area (r is more than or equal to 0 and less than or equal to h),can be substituted by the formula (6):the indefinite integral on both sides of equation (11) can be found:friction shear stress tau on contact surface during upsetting of cylinder_fThe distribution curves and formula (9) can be obtained when r ═ h, there areTherefore, it is Can be substituted by formula (12):integrating equation (13) in the friction stagnation region:(14) therefore, the riveting force of the punch on the heading is as follows: in the formula, σ_sThe yield strength of the rivet test piece, h is the height of the upset head, mu is the friction coefficient between the punch and the end face of the rivet rod, r_bThe diameter of the end face of the upset head.

9. The machine vision-based hole making and riveting quality control method according to claim 8, characterized in that: forming an upset head after the rivet stem is pressed and riveted, wherein the profile curve of the upset head is similar to a quadratic function curve, and coordinate points (0,0.5d), (0.5h and 0.5d) on the profile curve of the upset head are used_b)，(-0.5h,0.5d_b) Substituting the quadratic function equation to obtain the profile curve equation of the heading:after the squeeze riveting is finished, the volume of the heading is as follows:due to the clinch connection for determining the mounting point, the parameter d in equation (17)₀、l、d₁Since s is known, the right side of the equal sign is denoted as a constant C. The vertical type (16), (17) can obtain:d in formula (18)_bRelated to d and h, the relation is satisfied:formula (18), (19) are combined to give d_bH, d are related to each other, so that when the size of d is defined, the corresponding d is obtained_bAnd h, the replacement type (15) can obtain the riveting force required when the size of the heading is qualified.

10. The machine vision-based hole making and riveting quality control method according to claim 8, characterized in that: the size of the upset head cannot be directly controlled, but the riveting force required when the size of the upset head is qualified can be obtained according to the theoretical model, in the riveting process, a process monitoring riveter is equipped for workers, the workers judge whether the upset head of the riveting point is qualified or not according to the riveting force data collected by the process monitoring riveter, if the collected riveting force data is not in the standard riveting force interval, the suspected upset head of the riveting point is unqualified and detected, and otherwise, the riveting operation is continued.

Technical Field

The invention relates to the technical field of riveting, in particular to a hole making and riveting quality control method and device based on machine vision.

Background

The riveting process is widely applied to equipment manufacture in the fields of aviation and aerospace due to the characteristics of simple process, stable and reliable connection strength and the like. However, with the development requirements of high quality and high efficiency in the equipment manufacturing industry, higher requirements are provided for the riveting quality, and the hole forming quality and the size of the upset head after riveting directly influence the riveting quality, so that the development of a hole forming quality detection device and the research of an upset head size control method have important practical significance.

Patent publications and literature data at the present stage show: 1) in the patent (CN201410683172.3), a vision imaging system is installed at the motion end of a numerical control motion mechanism, and the motion mechanism drives the vision imaging system to move to a position with a proper shooting distance in the hole axis direction of a guide hole to be shot to shoot an image of the guide hole to be shot, but the motion mechanism will cause distortion when shooting a curved hole; 2) the patent (CN201910747724.5) discloses that a monocular vision camera is mounted on a sliding table to detect the diameter of a hole, but when a detected workpiece is large, a guide rail is long, the rigidity of a long and thin guide rail is weak, and the disturbance or even vibration of the guide rail affects the shooting definition of the camera, so that the final aperture detection precision is directly affected; 3) in the patent (CN201810350485.5), a linear array scanning CCD camera is arranged on a sliding bar to detect the punching defects on a production line, the stability of equipment is poor, only whether holes are closed or not and whether the number of the holes reaches the standard or not can be detected, the detection precision is low, and the detection of information such as hole diameter, roundness and the like cannot be realized; 4) the patent (CN201611180634.5) adopts a numerical approximation algorithm to calculate a rivet head height recommended value corresponding to the riveting force recommended value, then further calculates to obtain the diameter of the head of the formed rivet, adopts an approximation algorithm, does not consider the influence of the friction force of the end face of the head on the normal stress, and generates larger errors on the correlation calculation of the riveting force and the diameter of the head.

In summary, although the existing research results and methods can realize hole making quality detection and rivet pressing quality control to a certain extent, the existing research results and methods have the problems of low hole making quality detection precision, incapability of detecting curved surface holes, low rivet pressing quality control precision and the like, and a large number of curved surface holes exist in equipment manufacturing in the aviation and aerospace fields, so that the implementation effect cannot meet the development requirements of complicated manufacturing, high quality and high efficiency of high-end equipment.

Disclosure of Invention

The invention aims to solve the problems and provides a hole making and riveting quality control method and a device thereof based on machine vision, the device has stable structure, high automation degree and simple operation, two light sources of a white light lamp and a green light lamp can be selected, and clear original pictures can be collected no matter the hole making quality of a large workpiece or a small workpiece is detected; the original picture is subjected to gray processing, median filtering processing, threshold segmentation, edge extraction and the like, and interference points in the picture are removed by means of a bweraopen command and an imdilate command, so that the hole making quality detection precision can be remarkably improved; the first sliding block and the second sliding block are linked to drive the conical head to move to the position of the hole to be detected, the conical head is inserted into the hole by pulling out the push rod, the conical head is aligned to the hole to be detected according to the automatic centering function of the conical head, and then the CCD camera is aligned to the hole to be detected by rotating the rotary frame by 180 degrees, so that the quality detection of the curved surface hole is realized, and the distortion phenomenon is avoided; based on an engineering calculation method, a relation model of the riveting force and the size of the upset head is obtained under the condition that the influence of the friction force of the end face of the upset head on the normal stress is considered, the precision is high, the size of the upset head can be indirectly controlled through the riveting force, and the riveting quality is further improved; the process monitoring riveter is provided for workers to control the size of the upset head through riveting pressure control, so that timely discovery and timely remediation can be realized, and error accumulation is avoided, thereby improving the assembly quality and efficiency.

The invention realizes the purpose through the following technical scheme:

the invention provides a hole making and riveting quality control method and device based on machine vision, which is characterized in that: the technical architecture for realizing the hole making and riveting quality control comprises a hole center aligning stage, an original image acquisition stage, an image processing stage and an upset head quality monitoring stage, and specifically comprises the following steps: (1) the first sliding table, the second sliding table, the first sliding block, the second sliding block and the connecting rod are linked to realize that the CCD camera is aligned with a plane hole or a curved surface hole on the workpiece; (2) the conical head on the revolving frame is aligned to the center of the plane hole or the curved hole by fine adjustment of the positions of the first sliding block, the second sliding block and the connecting rod; (3) then, the center of the hole is aligned by the CCD camera through rotating the revolving frame for 180 degrees and locking the position, and shooting is carried out; (4) detecting the diameter and the roundness of the hole through gray processing, median filtering, threshold segmentation, edge extraction, least square fitting processing and a MajorAxisLength command based on the shot original picture; (5) according to the detected aperture, a relation model of the riveting force and the size of the upset head is utilized to indirectly monitor whether the size of the upset head is qualified or not by monitoring the riveting force, so that the size of the upset head is controlled, and the quality of the upset head and even the quality of the riveting are improved; (6) and (3) in the actual riveting assembly process, the steps (1) to (5) are circulated until all holes on the workpiece are detected and the quality and the guarantee of the riveting work are finished.

Further, the lower end of the box body is provided with a support leg, one side of the box body is provided with a box door, the inner side of the box body is provided with a drawer and a controller, the upper end of the drawer is provided with a computer, one side of the box body, which is close to the box door, is provided with a groove block, the upper end of the box body is provided with a base, the upper end of the base is provided with a first linear guide rail, the upper end of the first linear guide rail is provided with a first sliding table, the upper end of the first sliding table is provided with a second linear guide rail, the upper end of the second linear guide rail is provided with a second sliding table, the inner side of the second sliding table is provided with a glass plate, the second sliding table is hollow, the glass plate is embedded into the second sliding table, the lower end of the glass plate is provided with a green light lamp, the upper end of the glass plate is provided with a workpiece, the front side of the base is provided with a stand column, the rear end of the stand column is provided with a measuring head, the first lifting lug is arranged on the measuring head, the inner side of the first lifting lug is provided with a lead screw mounting seat, the lower end of the lead screw is provided with a lead screw, the lead screw outside is provided with first slider, first slider rear end is provided with the revolving frame mount pad, revolving frame mount pad lower extreme is provided with the revolving frame, be provided with the baffle in the recess of revolving frame, the revolving frame lower extreme is provided with the push rod mount pad, push rod mount pad lower extreme is provided with the push rod, the push rod lower extreme is provided with the circular cone head, the relative push rod mount pad opposite side of revolving frame lower extreme is provided with the camera mount pad, camera mount pad inboard is provided with the CCD camera, the CCD camera is provided with the white light lamp all around, the deflector lower extreme is provided with the second lug, second lug inboard is provided with the bolt, the deflector front side is provided with the slide rail, the slide rail inboard is provided with the second slider, be provided with the connecting rod on the second slider.

Further, when examining, the chamber door can be opened, and the picture that the drawer can use the computer to handle CCD camera collection is pulled out, and after the instrument used, the drawer can be pushed into, and magnet has been inlayed to the position that corresponds the recess piece on the chamber door, can inhale tightly with the recess piece to close the chamber door, when the device was located ambient light when dark, provide the light source through the white light, when light was bright, provide the light source through the green glow lamp, thereby improve the definition of picture.

Further, after a picture acquired by a CCD camera is acquired by a computer, the contour of the hole is obtained through gray processing, median filtering processing, threshold segmentation and edge extraction in sequence, wherein during edge extraction, interference points in the picture are removed through bweareaopen and imdilate commands in MATLAB, the edges of the inner hole and the outer hole are extracted through a Canny algorithm, then a contour curve of the hole is fitted through a least square method, and finally the lengths of a long axis and a short axis of the contour curve of the hole are measured through a MajorAxisLength command, so that the diameter and the roundness of the hole are measured.

Furthermore, the first linear guide rail can drive the first sliding table to move forwards and backwards, the second linear guide rail can drive the second sliding table to move leftwards and rightwards, the first sliding block can drive the revolving frame mounting base to move upwards and downwards through the lead screw, the first sliding block and the lead screw can be self-locked, the first sliding block cannot move downwards when only under the action of gravity, and the first linear guide rail, the second linear guide rail and the first sliding block are controlled by the controller to move.

Furthermore, the groove of the revolving frame and the groove on the revolving frame mounting seat can be inserted into the baffle plate when being collinear, when the baffle plate is pulled out, the revolving frame can rotate in the revolving frame mounting seat, when the baffle plate is inserted, the revolving frame is locked, and the distance from the optical center of the conical head and the CCD camera to the revolving center of the revolving frame is equal.

Further, the second slider has magnetic force to accessible knob control magnetic force size, the back is extracted to the bolt, thereby the second slider drives the connecting rod through removing in the slide rail and removes, and the connecting rod will promote the deflector swing, when swinging certain angle, sets up the magnetic force of second slider to the biggest, thereby locks dead current position.

The invention also provides a hole making and riveting quality control method based on machine vision, which is characterized by comprising the following steps: during riveting, the process of forming an upset head by the nail rod can be regarded as upsetting of the cylinder along the axis, and the deformation process has the axial symmetry characteristic. In the upsetting stage, the clinching force F gradually increases until it reaches a maximum value, the positive stress sigma acting on the upset_zThe shear stress tau of the contact surface of the heading and the punch is increased_fThe magnitude and distribution of (A) also directly influence the positive stress sigma_zThe distribution rule of (1). The research on the friction shear stress by combining the Umbersov shows that in the riveting process, the friction force area on the contact surface of the upset head and the punch comprises a stagnation area and a braking area, the friction stagnation area of the end surface of the cylinder is within the range of r being more than or equal to 0 and less than or equal to h, and the friction braking area is within the range of h being more than r and less than or equal to r_bSince the friction conditions adopted in each area are different, the obtained positive stress and riveting force of the contact surface are different, so that the riveting force F of the punch on the upset head is divided into two parts, and the riveting force F of the stagnation area and the braking area is recorded as F₁、 F₂. The flat cone head rivet clinching process can be considered as axisymmetric upsetting, and therefore, there is a balance equation:from the infinitesimal nature of equivalenceAnd neglecting the influence of second-order trace, equation (1) can be simplified as: sigma_θhdr-2τ_frdr-σ_rhdr-rhdσ_r0(2) wherein σ represents_θFor positive circumferential stress, σ_rFor positive radial stress, τ_rThe friction shear stress of the contact surface of the punch and the nail rod, r is the radius of the upset head, dr is the differential of the radius of the upset head, and d sigma is_rIs the integral of the radial positive stress. Since the shank has been assumed to be deformed by uniform upsetting, σ_r＝σ_θThus, equation (2) is simplified as:the yield equation is still simplified by the absolute value column, since_r＝σ_θTherefore, the following are: sigma_z-σ_r＝Y(4)、dσ_z＝dσ_r(5) In the formula, σ_zIs the axial positive stress to which the nail rod is subjected. The combined vertical type (3) and (5) can obtain:in the friction braking area (h < r ≦ r_b)，τ_f＝0.5σ_sThe formula (6) can be substituted by:the indefinite integral on both sides of equation (7) can be found: friction shear stress tau on contact surface during upsetting of cylinder_fThe distribution curve can be obtained when r is r_bWhen the temperature of the water is higher than the set temperature,therefore, it isCan be substituted by the formula (8): integration of equation (9) over the area of the friction braking zone can be found: in the friction stagnation area (r is more than or equal to 0 and less than or equal to h),can be substituted by the formula (6):the indefinite integral on both sides of equation (11) can be found:friction shear stress tau on contact surface during upsetting of cylinder_fThe distribution curves and formula (9) can be obtained when r ═ h, there areTherefore, it is Can be substituted by formula (12):integrating equation (13) in the friction stagnation region: therefore, the clinching force of the punch on the upset is as follows: in the formula, σ_sThe yield strength of the rivet test piece, h is the height of the upset head, mu is the friction coefficient between the punch and the end face of the rivet rod,r_bthe diameter of the end face of the upset head.

Further, a heading is formed after the nail rod is pressed and riveted, the contour curve of the heading is similar to a quadratic function curve, and coordinate points (0,0.5d), (0.5h and 0.5d) on the contour curve of the heading are measured_b)，(-0.5h,0.5d_b) Substituting the quadratic function equation to obtain the profile curve equation of the heading:after the squeeze riveting is finished, the volume of the heading is as follows:due to the clinch connection for determining the mounting point, the parameter d in equation (17)₀、l、d₁Since s is known, the right side of the equal sign is denoted as a constant C. The vertical type (16), (17) can obtain:d in formula (18)_bRelated to d and h, the relation is satisfied:formula (18), (19) are combined to give d_bH, d are related to each other, so that when the size of d is defined, the corresponding d is obtained_bAnd h, the replacement type (15) can obtain the riveting force required when the size of the heading is qualified.

Furthermore, because the size of the upset head cannot be directly controlled, but the riveting force required when the size of the upset head is qualified can be obtained according to the theoretical model, in the riveting process, a process monitoring riveter is equipped for a worker, the worker judges whether the upset head of the riveting point is qualified or not according to the riveting force data collected by the process monitoring riveter, if the collected riveting force data is not in the standard riveting force interval, the upset head of the riveting point is determined to be suspected to be unqualified and is detected, otherwise, the riveting operation is continued.

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

the hole making and riveting quality control device based on machine vision provided by the invention has the advantages of stable structure, high automation degree and simple operation, and two light sources, namely a white light lamp and a green light lamp, can be selected according to the light condition of the environment where the instrument is located, so that clear original pictures can be acquired no matter the hole making quality of a large workpiece or a small workpiece is detected;

according to the hole making and riveting quality control device based on machine vision, an original picture is subjected to gray processing, median filtering processing, threshold segmentation, edge extraction and the like, interference points in the picture are removed by means of a bweraopen command and an insert command, and hole making quality detection precision can be remarkably improved;

according to the hole making and riveting quality control device based on machine vision, the first sliding block and the second sliding block are linked to drive the conical head to move to the position of a hole to be measured, the conical head is inserted into the hole by pulling out the push rod, the conical head is aligned to the hole to be measured according to the automatic centering function of the conical head, and then the CCD camera is aligned to the hole to be measured by rotating the rotary frame for 180 degrees, so that the quality detection of a curved surface hole is realized, and the distortion phenomenon is avoided;

the invention provides a hole making and riveting quality control method based on machine vision, which comprises the following steps: based on an engineering calculation method, a relation model of the riveting force and the size of the upset head is obtained under the condition that the influence of the friction force of the end face of the upset head on the normal stress is considered, the precision is high, the size of the upset head can be indirectly controlled through the riveting force, and the riveting quality is further improved;

according to the hole making and riveting quality control method based on machine vision, provided by the invention, a process monitoring riveter is provided for workers to control the size of the upset head through riveting pressure control, so that timely discovery and timely remediation can be realized, and error accumulation is avoided, thereby improving the assembly quality and efficiency.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is an isometric view of a machine vision based hole making and riveting quality control device provided by the present invention;

FIG. 2 is a front full-sectional view of a hole making and riveting quality control device based on machine vision provided by the invention;

FIG. 3 is a schematic view of a turret and its internal structure provided by the present invention;

FIG. 4 is a schematic view of a second slider provided by the present invention;

FIG. 5 is a flow chart of the present invention for detecting the quality of a hole;

FIG. 6 is a schematic view of a curved hole and a planar hole in a workpiece according to the present invention;

FIG. 7 is a schematic view of the clinch provided by the present invention;

FIG. 8 is a diagram of the deformation of rivet upset and the force analysis of elements provided by the present invention;

FIG. 9 is a schematic view of an analytical calculation coordinate system for a profile of an upset head provided in accordance with the present invention;

fig. 10 is an interface diagram of a process monitoring riveter acquiring riveting force data in real time according to the present invention.

The reference numerals are explained below:

1. a box body; 2. a support leg; 3. a box door; 4. a groove block; 5. a drawer; 6. a computer; 7. a controller; 8. a base; 9. a first linear guide rail; 10. a first sliding table; 11. a second linear guide; 12. a second sliding table; 13. a workpiece; 14. a column; 15. a measuring head; 16. a first lifting lug; 17. a lead screw mounting seat; 18. a lead screw; 19. a guide plate; 20. a first slider; 21. a revolving rack mounting base; 22. a baffle plate; 23. a revolving frame; 24. a push rod mounting seat; 25. a push rod; 26. a conical head; 27. a camera mount; 28. a white light lamp; 29. A CCD camera; 30. a second lifting lug; 31. a bolt; 32. a slide rail; 33. a second slider; 34. a connecting rod; 35. A glass plate; 36. a green light lamp.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings. The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

As shown in fig. 1-6, a hole making and riveting quality control device based on machine vision is characterized in that: as shown in fig. 1 and 2, the lower end of the box body 1 is provided with support legs 2, the box body 1 is connected with the support legs 2 through bolts, one side of the box body 1 is provided with a box door 3, the box body 1 is connected with the box door 3 through hinges, the inner side of the box body 1 is provided with a drawer 5 and a controller 7, the upper end of the drawer 5 is provided with a computer 6, one side of the box body 1 close to the box door 3 is provided with a groove block 4, the groove block 4 is connected with the box body 1 through bolts, when the detection is carried out, the box door 3 can be opened, the drawer 5 can be pulled out to process pictures collected by the CCD camera 29 through the computer 6, after the instrument is used, the drawer 5 can be pushed in, the position on the box door 3 corresponding to the groove block 4 is embedded with a magnet which can be tightly absorbed with the groove block 4, so as to tightly close the box door 3, the upper end of the box body 1 is provided with a base 8 through glue joint, the upper end of the base 8 is provided with a first linear guide rail 9, the base 8 is connected with the first linear guide rail 9 through bolts, the upper end of a first linear guide rail 9 is provided with a first sliding table 10, the upper end of the first sliding table 10 is provided with a second linear guide rail 11, the first sliding table 10 is connected with the second linear guide rail 11 through screws, the upper end of the second linear guide rail 11 is provided with a second sliding table 12, the first linear guide rail 9 can drive the first sliding table 10 to move forwards and backwards, the second linear guide rail 11 can drive the second sliding table 12 to move leftwards and rightwards, the inner side of the second sliding table 12 is provided with a glass plate 35, the second sliding table 12 is hollow, the glass plate 35 is embedded into the second sliding table 12, the lower end of the glass plate 35 is provided with a green light lamp 36, the upper end of the glass plate 35 is provided with a workpiece 13, the front side of a base 8 is provided with a stand column 14, the stand column 14 is connected with a box body 1 through bolts, the rear end of the stand column 14 is provided with a measuring head 15, the measuring head 15 is connected with the stand column 14 through welding, a first lifting lug 16 is arranged on the measuring head 15, and the first lifting lug 16 is connected with the measuring head 15 through welding, a lead screw mounting seat 17 is arranged on the inner side of the first lifting lug 16, the first lifting lug 16 is connected with the lead screw mounting seat 17 through a pin shaft, a lead screw 18 is arranged at the lower end of the lead screw mounting seat 17, the lead screw mounting seat 17 is connected with the lead screw 18 through a thread, a guide plate 19 is arranged at the front end of the lead screw 18, a first slide block 20 is arranged on the outer side of the lead screw 18, the lead screw 18 is connected with the first slide block 20 through a thread, a revolving frame mounting seat 21 is arranged at the rear end of the first slide block 20, the first slide block 20 can drive the revolving frame mounting seat 21 to move up and down through the lead screw 18, the first slide block 20 and the lead screw 18 can be self-locked, the first slide block 20 cannot move down under the action of gravity, the first linear guide rail 9, the second linear guide rail 11 and the first slide block 20 are controlled by the controller 7 to move, the revolving frame mounting seat 21 is connected with the first slide block 20 through a screw, a revolving frame 23 is arranged at the lower end of the revolving frame mounting seat 21, the revolving frame mounting base 21 is connected with the revolving frame 23 through a thread, a baffle 22 is arranged in a groove of the revolving frame 23, the baffle 22 can be inserted when the groove of the revolving frame 23 and the groove on the revolving frame mounting base 21 are collinear, when the baffle 22 is pulled out, the revolving frame 23 can rotate in the revolving frame mounting base 21, when the baffle 22 is inserted, the revolving frame 23 is locked, the distance from the optical center of the conical head 26 and the CCD camera 29 to the revolving center of the revolving frame 23 is equal, as shown in FIG. 3, a push rod mounting base 24 is arranged at the lower end of the revolving frame 23, the push rod mounting base 24 is connected with the revolving frame 23 through a welding way, a push rod 25 is arranged at the lower end of the push rod mounting base 24, the push rod 25 is connected with the push rod mounting base 24 through an interference fit, the conical head 26 is arranged at the lower end of the push rod 25, the conical head 26 is connected with the push rod 25 through a thread, a camera mounting base 27 is arranged at the lower end of the revolving frame 23 opposite to the push rod mounting base 24, the camera mounting seat 27 is connected with the revolving frame 23 by welding, the CCD camera 29 is arranged on the inner side of the camera mounting seat 27, the camera mounting seat 27 is connected with the CCD camera 29 by screws, the white light lamp 28 is arranged on the periphery of the CCD camera 29, when the ambient light of the device is dark, the white light lamp 28 provides a light source, when the light is bright, the green light lamp 36 provides a light source, thereby improving the definition of the picture, as shown in FIG. 5, after the computer 6 acquires the picture collected by the CCD camera 29, the outline of the hole is obtained by gray processing, median filtering processing, threshold segmentation and edge extraction in sequence, wherein, when the edge extraction is carried out, the interference points in the picture are removed by bweraopen and insert commands in MATLAB, the inner and outer hole edges are extracted by Canny algorithm, then the outline curve of the hole is fitted by least square method, finally the lengths of the long axis and the short axis of the outline curve of the hole are measured by Majoror AxisLength command, thereby measuring the diameter and the roundness of the hole, the lower end of the guide plate 19 is provided with a second lifting lug 30, the second lifting lug 30 is connected with the measuring head 15 through welding, the inner side of the second lifting lug 30 is provided with a bolt 31, the front side of the guide plate 19 is provided with a slide rail 32, the slide rail 32 is connected with the measuring head 15 through a screw, the inner side of the slide rail 32 is provided with a second slide block 33, the second slide block 33 is connected with the slide rail 32 through a clamping groove, the second slide block 33 is provided with a connecting rod 34, the connecting rod 34 is connected with the second slide block 33 through a hinge, the connecting rod 34 is connected with the guide plate 19 through a hinge, as shown in fig. 4, the second slide block 33 has magnetic force, the magnetic force can be controlled through a knob, after the bolt 31 is pulled out, the second slide block 33 drives the connecting rod 34 to move through moving in the slide rail 32, the connecting rod 34 pushes the guide plate 19 to swing, when swinging to a certain angle, the magnetic force of the second slide block 33 is set to the maximum, thereby locking the current position.

As shown in fig. 6, when the diameter and the roundness of the plane hole on the workpiece 13 need to be detected, first, the workpiece 13 is placed on the glass plate 35, the box door 3 is opened, the drawer 5 is pulled out, the computer 6 is started, the controller 7 controls the first linear guide rail 9 and the second linear guide rail 11 to drive the first sliding table 10 and the second sliding table 12 to move in the horizontal direction, so that the plane hole on the workpiece 13 is positioned under the CCD camera 29, then, the white light lamp 28 light source or the green light lamp 36 light source is selected to be turned on according to the brightness and darkness of the ambient light of the instrument, and finally, the first slider 20 drives the revolving frame mounting base 21 to move up and down through the lead screw 18, so as to drive the CCD camera 29 to move, so that the CCD camera 29 focuses on the plane of the workpiece 13 to shoot the hole, and obtain an image of the plane hole.

When the diameter and the roundness of the curved hole on the workpiece 13 need to be detected, the optical center of the CCD camera 29 is not collinear with the axis of the curved hole, so that the photographed curved hole is distorted, and the diameter and the roundness cannot be accurately detected, and the method adopted by the present invention for the problem is: firstly, a workpiece 13 is placed on a glass plate 35, a box door 3 is opened, a drawer 5 is drawn out, a computer 6 is started, a controller 7 controls a first linear guide rail 9 and a second linear guide rail 11 to drive a first sliding table 10 and a second sliding table 12 to move in the horizontal direction, so that a curved surface hole on the workpiece 13 is positioned at the rear side of a CCD camera 29, then a white light 28 light source or a green light 36 light source is selected to be opened according to the brightness and darkness of the ambient light of the instrument, finally, a bolt 31 is pulled out, a first sliding block 20 drives a rotary frame mounting base 21 to move up and down through a lead screw 18, a second sliding block 33 is set to be minimum in magnetic force, a connecting rod 34 is driven to push the rotary frame mounting base 21 to swing through moving up and down on the inner side of a sliding rail 32, so that a conical head 26 on a push rod 25 is aligned with the curved surface hole, the conical head 26 is driven to be inserted into the curved surface hole through the push rod 25 being drawn out, the conical head 26 is ensured to be aligned with the curved surface hole according to the automatic centering effect of a cone, at this time, the baffle 22 is pulled out, the revolving frame 23 is rotated by 180 degrees, then the baffle 22 is inserted, the current position is locked, because the distance from the optical center of the CCD camera 29 and the axis of the conical head 26 to the revolving center of the revolving frame 23 is equal, the optical center of the CCD camera 29 is aligned with the curved hole, at this time, the magnetic force of the second slider 33 is set to the maximum, the swinging angle is locked, then the first slider 20 drives the revolving frame mounting seat 21 to move up and down through the lead screw 18 again, so that the CCD camera 29 focuses on the curved hole, and the hole is shot, and the image of the curved hole is obtained.

After obtaining the image of the planar or curved hole, the CCD camera 29 transfers the image to the computer 6 by wire transmission. After the computer 6 acquires the picture acquired by the CCD camera 29, the contour of the hole is obtained by sequentially performing gray processing, median filtering processing, threshold segmentation and edge extraction, wherein during edge extraction, interference points in the picture are removed by using bweareaopen and imdilate commands in MATLAB, the edges of the inner hole and the outer hole are extracted by using a Canny algorithm, then a contour curve of the hole is fitted by using a least square method, and finally the lengths of a long axis and a short axis of the contour curve of the hole are measured by using a MajorAxisLength command, so that the diameter and the roundness of the hole are measured, and after the detection is finished, the controller 7 and the computer 6 are closed, the drawer 5 is pushed in, and the box door 3 is closed.

The invention provides a hole making and riveting quality control device based on machine vision, which comprises the following main components in model specifications: the controller 7 is TK-180 in model, the first linear guide rail 9 is GCH10-L5-400-BC-M10B-C4 in model, the second linear guide rail 11 is GCH 10-L5-600-BC-M10B-C2 in model, a screw rod sliding block assembly composed of the screw rod mounting seat 17, the screw rod 18, the guide plate 19 and the first sliding block 20 is YH120-S350-FO-1610 in model, the push rod 25 is XC6000 in model, and the CCD camera 29 is SZ7D-200HD in model.

As shown in fig. 7-10, a method for controlling the quality of hole making and riveting based on machine vision is characterized in that: as shown in FIG. 7, during riveting, the heading forming process of the nail rod can be regarded as upsetting of the cylinder along the axis, and the deformation process is axially symmetrical. In the upsetting stage, as shown in fig. 8, the clinching force F increases gradually until it reaches a maximum value, and the positive stress σ acting on the upset head_zThe shear stress tau of the contact surface of the heading and the punch is increased_fThe magnitude and distribution of (A) also directly influence the positive stress sigma_zThe distribution rule of (1). The research on the friction shear stress by combining the Umbersov shows that in the riveting process, the friction force area on the contact surface of the upset head and the punch comprises a stagnation area and a braking area, the friction stagnation area of the end surface of the cylinder is within the range of r being more than or equal to 0 and less than or equal to h, and the friction braking area is within the range of h being more than r and less than or equal to r_bSince the friction conditions adopted in each area are different, the obtained positive stress and riveting force of the contact surface are different, so that the riveting force F of the punch on the upset head is divided into two parts, and the riveting force F of the stagnation area and the braking area is recorded as F₁、F₂. The flat cone head rivet clinching process can be considered as axisymmetric upsetting, and therefore, there is a balance equation: from the infinitesimal nature of equivalenceAnd neglecting the influence of second-order trace, equation (1) can be simplified as: sigma_θhdr-2τ_frdr-σ_rhdr-rhdσ_r0(2) wherein σ represents_θFor positive circumferential stress, σ_rFor positive radial stress, τ_rThe friction shear stress of the contact surface of the punch and the nail rod, r is the radius of the upset head, dr is the differential of the radius of the upset head, and d sigma is_rIs the integral of the radial positive stress. Since it has been assumed that the nail rods are allUniform upsetting deformation, so σ_r＝σ_θThus, equation (2) is simplified as:the yield equation is still simplified by the absolute value column, since_r＝σ_θTherefore, the following are: sigma_z-σ_r＝Y(4)、dσ_z＝dσ_r(5) In the formula, σ_zIs the axial positive stress to which the nail rod is subjected. The combined vertical type (3) and (5) can obtain:in the friction braking area (h < r ≦ r_b)，τ_f＝0.5σ_sThe formula (6) can be substituted by:the indefinite integral on both sides of equation (7) can be found:friction shear stress tau on contact surface during upsetting of cylinder_fThe distribution curve can be obtained when r is r_bWhen the temperature of the water is higher than the set temperature,therefore, it isCan be substituted by the formula (8):integration of equation (9) over the area of the friction braking zone can be found: in the friction stagnation area (r is more than or equal to 0 and less than or equal to h),can be substituted by formula (6)： The indefinite integral on both sides of equation (11) can be found:friction shear stress tau on contact surface during upsetting of cylinder_fThe distribution curves and formula (9) can be obtained when r ═ h, there areTherefore, it isCan be substituted by formula (12):integrating equation (13) in the friction stagnation region:thus, the clinching force of the punch against the upset In the formula, σ_sThe yield strength of the rivet test piece, h is the height of the upset head, mu is the friction coefficient between the punch and the end face of the rivet rod, r_bThe diameter of the end face of the upset head. Forming an upset head after the rivet stem is pressed and riveted, as shown in figure 9, the profile curve of the upset head is similar to a quadratic function curve, and coordinate points (0,0.5d), (0.5h and 0.5d) on the profile curve of the upset head are calculated_b)，(-0.5h,0.5d_b) Substituting the quadratic function equation to obtain the profile curve equation of the heading:after the squeeze riveting is finished, the volume of the heading is as follows: due to the clinch connection for determining the mounting point, the parameter d in equation (17)₀、l、d₁Since s is known, the right side of the equal sign is denoted as a constant C. The vertical type (16), (17) can obtain:d in formula (18)_bRelated to d and h, the relation is satisfied:formula (18), (19) are combined to give d_bH, d are related to each other, so that when the size of d is defined, the corresponding d is obtained_bAnd h, the replacement type (15) can obtain the riveting force required when the size of the heading is qualified. The size of the upset head cannot be directly controlled, but the riveting force required when the size of the upset head is qualified can be obtained according to the theoretical model, a process monitoring riveter is equipped for a worker in the riveting process, as shown in fig. 10, the worker judges whether the upset head of the riveting point is qualified or not according to riveting force data collected by the process monitoring riveter, if the collected riveting force data is not in a standard riveting force interval, the suspected upset head of the riveting point is determined to be unqualified and detected, otherwise, the riveting operation is continued, so far, the size of the upset head after riveting is indirectly monitored by monitoring the size of the riveting force, the detection is timely found, the remedy is timely carried out, the error accumulation is avoided, and the riveting quality and the assembly quality are improved. The effectiveness of the theoretical model is verified through tests, and the average error of the diameter and the height of the upset is less than 5% under the determined riveting force.

Finally, it should be noted that: although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can modify and substitute specific embodiments of the present invention without departing from the spirit and scope of the present invention, which is defined by the claims of the appended claims.