Multi-workpiece full-automatic detection system adopting visual servo control

Abstract

The invention discloses a multi-workpiece full-automatic detection system adopting visual servo control. The multi-workpiece full-automatic detection system comprises a large-view visual servo camera, a high-precision measurement camera, a motion control system, an adjustable mounting bracket, an image processor and a workbench, the large-view visual servo camera is used for collecting position information images of all target workpieces on the working table; the high-precision measurement camera is used for collecting an overall edge contour feature information image and a local sequence image of the target workpiece; the adjustable mounting bracket is used for mounting the measuring camera and the visual servo camera so as to ensure that a workpiece on the working table is clearly imaged; the workbench is used for placing a plurality of workpieces to be detected; the image processor is electrically connected with the large-view visual servo camera and the high-precision measurement camera; the motion control system is electrically connected with the workbench and the image processor. According to the invention, full-automatic intelligent measurement and detection can be carried out on a plurality of target workpieces randomly placed on the working table. And the detection efficiency of a large batch of parts is greatly improved.

Description

Technical Field

[0001] The present invention belongs to the field of visual inspection, and in particular relates to a multi-workpiece full-automatic inspection system adopting visual servo control. Background Art

[0002] Visual inspection technology is widely used in electronics, chips, components, rubber products, machinery manufacturing and other fields. Compared with traditional inspection methods, which have advantages such as non-contact and high precision, visual inspection systems have a relatively small field of view to ensure high precision. When performing large-scale inspection tasks for parts, they face many problems, such as positioning the measurement object, time-consuming origin positioning, and long batch measurement operations. They can no longer meet the needs of high-efficiency automated inspection. Visual servoing has many advantages. With the help of visual servo cameras, the visual inspection system increases the ability to obtain information about workpieces outside the field of view, reducing the position requirements of the workpieces to be tested. On the other hand, it can provide reliable and accurate guidance for the visual inspection system when performing inspection tasks. Locating the target workpiece position through visual servoing methods can improve the intelligence level of the inspection system and complete more and wider tasks.

[0003] Therefore, how to provide a fully automatic inspection system that can ensure high precision while meeting the requirements of efficient inspection of large quantities of parts is an urgent problem that needs to be solved by those skilled in the art. Summary of the Invention

[0004] The present invention provides a multi-workpiece fully automatic detection system using visual servo control, which completes fully automatic intelligent detection of multi-target workpieces by introducing a large-field-of-view camera as a visual servo guidance module of the detection system and cooperating with a small-field-of-view high-precision measurement camera.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A multi-workpiece fully automatic inspection system using visual servo control, comprising: a large-field visual servo camera, a high-precision measurement camera, a motion control system, an adjustable mounting bracket, an image processor, and a workbench;

[0007] The workbench is used to place the workpiece to be inspected;

[0008] The adjustable mounting bracket is connected to the workbench base via bolts;

[0009] The large-field visual servo camera and the high-precision measurement camera are both mounted on an adjustable mounting bracket, and are both mounted facing the workbench;

[0010] The image processor is electrically connected to the large-field visual servo camera and the high-precision measurement camera; the motion control system is electrically connected to the workbench and the image processor.

[0011] The large-field visual servo camera is used to collect position information images of all target workpieces on the worktable; the high-precision measurement camera is used to collect overall edge profile feature information images and local sequence images of the target workpieces; the image processor is used to perform image processing on the collected workpiece images; the motion control system automatically generates a motion path for the worktable based on the geometric center position of each workpiece obtained after processing the workpiece image to be measured, and controls the worktable to operate according to the motion path; the workpieces to be measured at various positions on the worktable are moved in sequence to the center position of the field of view of the high-precision measurement camera to complete the inspection task.

[0012] Preferably, in the above-mentioned fully automatic inspection system for multiple workpieces using visual servo control, the image processor is used to perform grayscale conversion, filtering and noise reduction, threshold segmentation and edge detection on the image of the workpiece to be inspected.

[0013] Preferably, in the above-mentioned fully automatic inspection system for multiple workpieces using visual servo control, the wide-field visual servo camera has lens distortion. In order to determine the correspondence between the coordinate points in the real three-dimensional world and the points projected on the two-dimensional image, it is necessary to establish the imaging geometric model of the wide-field visual servo camera and solve the relevant parameters.

[0014] Preferably, in the above-mentioned multi-workpiece fully automatic inspection system using visual servo control, the large-field visual servo camera needs to undergo camera calibration through a calibration board to obtain the internal and external parameter matrix of the large-field visual servo camera, and then perform real-time distortion correction operations on the collected workpiece images.

[0015] Preferably, in the above-mentioned fully automatic inspection system for multiple workpieces using visual servo control, there are multiple high-precision measuring cameras, including an upright camera installed perpendicular to the workbench and side cameras installed obliquely on the left and right sides, which respectively image the same area of ​​the workbench surface at different angles to obtain image information of different parts of the workpiece surface.

[0016] Preferably, in the above-mentioned fully automatic inspection system for multiple workpieces using visual servo control, the motion control system is also used to automatically generate a serial image acquisition path for the workpiece after measuring the size information of a single workpiece; and control the movement of the worktable so that the workpiece rotates around its geometric center to complete the acquisition of serialized images.

[0017] Preferably, in the above-mentioned fully automatic multi-workpiece inspection system using visual servo control, the workbench can translate along the X and Y directions and rotate around the Z axis, and the workbench surface is made of frosted glass that is transparent from top to bottom, which can achieve telecentric imaging.

[0018] Preferably, in the above-mentioned multi-workpiece fully automatic inspection system using visual servo control, the workbench uses a stepper motor and a linear screw transmission method to achieve translation in the X and Y directions, and is equipped with a guide mechanism to increase the load-bearing capacity of the mechanism, and uses a synchronous pulley to achieve Z-axis rotational motion.

[0019] Preferably, the above-mentioned fully automatic inspection system for multiple workpieces using visual servo control further includes a lighting system, which is composed of a ring-shaped top light source, a highly directional backlight source, and a light source controller.

[0020] Preferably, in the above-mentioned fully automatic multi-workpiece inspection system using visual servo control, the adjustable mounting bracket is used to install a high-precision telecentric measurement camera-lens group, so that the distance from multiple measurement camera lenses to the workbench is the working distance of the telecentric lens.

[0021] It can be seen from the above technical solutions that, compared with the prior art, the present invention discloses a multi-workpiece fully automatic inspection system using visual servo control, which has the following beneficial effects:

[0022] 1. The present invention applies visual servo control to the visual inspection industry, which can realize fully automatic detection of multiple target workpieces within the field of view, meeting the needs of automated and efficient detection of large quantities of parts. This method has certain versatility for regular workpieces such as round and square shapes.

[0023] 2. During the detection process, the present invention adopts a large-field visual servo camera to capture images of all target workpieces on the work surface, utilizes an image processor to analyze the workpiece image, extracts the image position information coordinates of the workpiece to be measured, realizes visual positioning, and generates an automatic detection path. By calibrating the global field of view of the visual servo camera, the single-pixel accuracy of each position on the image is obtained, and the pixel coordinate relationship of the workpiece is converted into the real physical position coordinate relationship and transmitted to the motion control system to realize fully automatic detection of multiple workpieces.

[0024] 3. This invention uses a coordinated measurement method with a fixed camera and a moving worktable. The worktable can achieve three degrees of freedom and can move according to the placement of the workpiece on the table. Each workpiece is moved to the center of the field of view of the high-precision measurement camera. In combination with an image processor, the workpiece's dimensional measurement and defect detection tasks are performed. This method not only has a high degree of automation but also avoids the problem of repeated positioning of multiple workpieces. This solves the problems of low automation and low detection efficiency of traditional visual inspection systems for large-scale parts inspection.

[0025] 4. The present invention adopts a combination of multiple cameras for measurement, which can expand the field of view while ensuring high precision, and avoid the situation where the workpiece on the workbench is in the blind spot of the field of view and is missed. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only embodiments of the present invention. Those skilled in the art can also derive other drawings based on the provided drawings without inventive effort.

[0027] Figure 1 This is a structural schematic diagram of a multi-workpiece fully automatic detection system using visual servo control provided by the present invention.

[0028] Figure 2 This is an overall framework diagram of a multi-workpiece fully automatic detection system using visual servo control provided by the present invention.

[0029] Figure 3 This is a workflow diagram of a multi-workpiece fully automatic detection system using visual servo control provided by the present invention. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] like Figure 1 As shown, the embodiment of the present invention discloses a multi-workpiece fully automatic inspection system using visual servo control, comprising: a large-field visual servo camera 1, a high-precision measurement camera 2, a motion control system 5, an adjustable mounting bracket 3, an image processor 6, and a workbench 4;

[0032] The workbench 4 is used to place the workpiece to be inspected;

[0033] The adjustable mounting bracket 3 is connected to the base of the workbench 4 by bolts;

[0034] The large-field visual servo camera 1 and the high-precision measurement camera 2 are both mounted on an adjustable mounting bracket 3 and are both mounted facing the workbench 4;

[0035] The image processor 6 is electrically connected to the large-field visual servo camera 1 and the high-precision measurement camera 2 ; the motion control system 5 is electrically connected to the workbench 4 and the image processor 6 .

[0036] The large-field-of-view visual servo camera 1 is used to collect position information images of all target workpieces on the workbench 4; the high-precision measurement camera 2 is used to collect overall edge profile feature information images and local sequence images of the target workpieces; the image processor 6 is used to perform image processing on the collected workpiece images; the motion control system 5 automatically generates a motion trajectory of the workbench 4 based on the geometric center position of each workpiece obtained after processing the workpiece image to be measured, and controls the workbench 4 to operate according to the motion trajectory; the workpieces to be measured at various positions on the workbench 4 are moved in sequence to the center position of the field of view of the high-precision measurement camera 2 to complete the detection task.

[0037] In one embodiment, the camera lens assembly is mounted above the workbench 4; the image processor 6 and the motion control system 5 are integrated into a single chassis. Signal lines electrically connect the wide-field visual servo camera 1 to the image processor 6, the image processor 6 to the motion control system 5, and the motion control system 5 to the workbench 4.

[0038] In one specific embodiment, the high-precision measurement cameras are multiple, including an upright camera mounted perpendicular to the worktable and two oblique cameras mounted at angles on either side. Each camera images the same area of ​​the worktable at different angles to obtain image information from different parts of the workpiece surface. The high-precision cameras are positioned to achieve the optimal working distance of the telecentric lens, ensuring optimal imaging quality and maximizing inspection efficiency.

[0039] Specifically, the wide-field visual servo camera 1 is calibrated using the Zhang Zhengyou calibration method to obtain the camera's intrinsic and extrinsic parameter matrix, and the captured image is corrected in real time. Image processor 6 employs grayscale processing, median filtering for noise reduction, threshold segmentation based on region partitioning and the maximum inter-class variance method, and edge detection using the Canny operator. Furthermore, a least-squares ellipse fitting is performed on the workpiece edge to obtain the pixel coordinates of the workpiece's geometric center. In this embodiment, image processor 6 employs grayscale processing, filtering for noise reduction, threshold segmentation, edge detection, and least-squares ellipse fitting to solve the problem of precise visual positioning of multiple target workpieces in an image.

[0040] In a specific embodiment, a linear ruler is engraved on a workbench, and the movement of the workbench is controlled by a motion control system. The linear ruler is moved to various positions within the field of view of a large-field visual servo camera and photographs are taken. The single-pixel accuracy of the linear ruler position on different images is measured and recorded by an image processor. By performing a global field of view calibration on the visual servo camera, a functional relationship is obtained in which the single-pixel accuracy at different positions on the image changes with the pixel coordinates, thereby establishing a conversion relationship between the pixel coordinates and the real physical position coordinates, and realizing visual servo control of the detection system.

[0041] In a specific embodiment, the adjustable mounting bracket 3 is used to install a high-precision telecentric measurement camera-lens group 2 and a large-field visual servo camera 1, so that the distance from multiple measurement camera lenses to the workbench is the working distance of the telecentric lens.

[0042] In a specific embodiment, the inspection system further includes an illumination system comprising an annular top light source 7, a highly directional backlight source, and a light source controller. The annular top light source 7 is used to illuminate downward from above, highlighting the surface defect characteristics of the workpiece. The backlight source is used to illuminate upward from the bottom of the workbench, highlighting the contour characteristics of the workpiece. The light source controller facilitates real-time adjustment of the brightness and operating status of the two light sources.

[0043] Combine Figure 2 and Figure 3 The embodiment of the present invention discloses a multi-workpiece fully automatic detection system using visual servo control. The specific detection workflow is as follows:

[0044] Start the system, and the workbench moves to the initial origin. A crosshair is engraved in the center of the table. The crosshair is photographed by a high-precision measuring camera. The image processor obtains the difference between the center of the crosshair and the center of the image. This value is passed to the motion control system to control the movement of the workbench so that the center of the crosshair coincides with the center of the high-precision measuring camera, completing the precise return to the origin.

[0045] Place multiple workpieces to be tested on the workbench at random;

[0046] The large-field visual servo camera collects images of all target workpieces on the work surface;

[0047] The image processor analyzes and processes the image of the target workpiece to obtain the number of all target workpieces and the pixel coordinates of the geometric center;

[0048] The motion control system automatically plans the workbench's path based on the pixel coordinates of the workpiece's geometric center, and then controls the workbench's operation, moving each workpiece along the specified path to the center of the high-precision measurement camera's field of view to begin the inspection task.

[0049] After the workpiece moves to the target position, a high-precision measuring camera captures the workpiece image within the field of view. The image processor processes and analyzes the image to obtain the workpiece's dimensional information. The motion control system then generates a workpiece sequence image acquisition path based on the workpiece's dimensional parameters, controls the operation of the workbench, and uses an inclined measuring camera to capture defect feature information images on the inner and outer surfaces of the workpiece to complete the defect detection task.

[0050] Given that the efficiency of traditional optical inspection systems is no longer sufficient for mass production, this paper proposes a multi-target workpiece inspection method using visual servoing control. By calibrating the global field of view of the visual servo camera, the pixel coordinate relationships between the workpieces to be inspected are converted into real physical coordinates and transmitted to the motion control system, enabling fully automatic intelligent inspection of multiple workpieces. Compared with traditional single-target inspection methods, this method significantly improves inspection efficiency, overcoming the problem of slow inspection efficiency in mass production. This method has important engineering application value in the field of visual inspection.

[0051] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A multi-workpiece fully automatic inspection system using visual servo control, characterized in that: include: Large field of view visual servo camera, high-precision measurement camera, motion control system, adjustable mounting bracket, image processor, workbench; The workbench is used to place the workpiece to be inspected; The adjustable mounting bracket is connected to the workbench base via bolts; The large-field visual servo camera and the high-precision measurement camera are both mounted on an adjustable mounting bracket, and are both mounted facing the workbench; The image processor is electrically connected to the large-field visual servo camera and the high-precision measurement camera; the motion control system is electrically connected to the workbench and the image processor; The large-field visual servo camera is used to collect position information images of all target workpieces on the worktable; the high-precision measurement camera is used to collect overall edge profile feature information images and local sequence images of the target workpieces; the image processor is used to perform image processing on the collected workpiece images; the motion control system automatically generates a motion trajectory of the worktable based on the geometric center position of each workpiece obtained after processing the workpiece image to be measured, and controls the worktable to operate according to the motion trajectory; the workpieces to be measured at various positions on the worktable are moved in sequence to the center position of the field of view of the high-precision measurement camera to complete the inspection task.

2. The multi-workpiece fully automatic inspection system using visual servo control according to claim 1, characterized in that; The image processor is used to perform grayscale conversion, filtering and noise reduction, threshold segmentation and edge detection on the image of the workpiece to be measured.

3. The multi-workpiece fully automatic inspection system using visual servo control according to claim 1 is characterized in that: The wide field of view visual servo camera has lens distortion. In order to determine the correspondence between the coordinate points in the real three-dimensional world and the points projected on the two-dimensional image, it is necessary to establish the imaging geometric model of the wide field of view visual servo camera and solve the relevant parameters.

4. The multi-workpiece fully automatic inspection system using visual servo control according to claim 3 is characterized in that: The large-field-of-view visual servo camera needs to be calibrated using a calibration board to obtain the internal and external parameter matrix of the large-field-of-view visual servo camera, and then a real-time distortion correction operation is performed on the collected workpiece image.

5. The multi-workpiece fully automatic inspection system using visual servo control according to claim 1 is characterized in that: There are multiple high-precision measurement cameras, including an upright camera installed perpendicular to the workbench and side cameras installed obliquely on the left and right sides, which image the same area of ​​the workbench surface at different angles to obtain image information of different parts of the workpiece surface.

6. The multi-workpiece fully automatic inspection system using visual servo control according to claim 1 is characterized in that: The motion control system is also used to automatically generate a serial image acquisition path for the workpiece after measuring the dimensional information of a single workpiece; control the movement of the worktable so that the workpiece rotates around its geometric center to complete the acquisition of serialized images.

7. The multi-workpiece fully automatic inspection system using visual servo control according to claim 1 is characterized in that: The workbench can translate in the X and Y directions and rotate around the Z axis, and the workbench surface is made of frosted glass that is transparent from top to bottom, which can achieve telecentric imaging.

8. The multi-workpiece fully automatic inspection system using visual servo control according to claim 7 is characterized in that: The workbench uses a stepper motor and a linear screw to achieve translation in the X and Y directions, and is equipped with a guide mechanism to increase the load-bearing capacity of the mechanism, and uses a synchronous pulley to achieve Z-axis rotation.

9. The multi-workpiece fully automatic inspection system using visual servo control according to claim 1 is characterized in that: The invention also comprises a lighting system, which consists of a ring-shaped top light source, a highly directional backlight source and a light source controller.

10. The multi-workpiece fully automatic inspection system using visual servo control according to claim 1, characterized in that: The adjustable mounting bracket is used to mount a high-precision telecentric measurement camera-lens assembly, so that the distance from the multiple measurement camera lenses to the workbench is the working distance of the telecentric lens.

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