阅读说明：本技术 一种基于机器视觉的管材直径测量装置及其测量方法 (Pipe diameter measuring device and method based on machine vision ) 是由 陈占春 孙亮 于兵 姚爱英 于 2019-08-14 设计创作，主要内容包括：本发明属于管材测量领域,公开了一种基于机器视觉的管材直径测量装置及其测量方法,该装置包括垂直连接的竖向支架和底盘,支架上水平连接有上下两根横杆,两根横杆的同侧端头分别安装有一个相机,两个相机处于被测管材中心线正上方；两根横杆分别通过夹持装置与竖向支架可调式安装,通过夹持装置连续调节相机距离管材的竖向距离以及相机水平方向的伸出长度。本发明是使用自然光源与两台高清相机相结合的方式进行非接触式测量,装置简易且成本低,并可以去除管材的圆心跳动所产生的测量误差；本发明可以实现管材运行中的实时在线测量,即使管材在运行中存在径向跳动也可以准确的测量其直径。(The invention belongs to the field of pipe measurement, and discloses a pipe diameter measuring device based on machine vision and a measuring method thereof, wherein the device comprises a vertical support and a chassis which are vertically connected, an upper cross rod and a lower cross rod are horizontally connected on the support, the ends of the two cross rods on the same side are respectively provided with a camera, and the two cameras are positioned right above the central line of a pipe to be measured; the two cross rods are respectively installed with the vertical support in an adjustable mode through the clamping devices, and the vertical distance between the camera and the pipe and the extension length of the camera in the horizontal direction are continuously adjusted through the clamping devices. The invention uses the mode of combining the natural light source and two high-definition cameras to carry out non-contact measurement, has simple device and low cost, and can remove the measurement error generated by the circle center jump of the pipe; the invention can realize real-time online measurement in the operation of the pipe, and can accurately measure the diameter of the pipe even if the pipe has radial run-out in the operation.)

1. A pipe diameter measuring method based on machine vision is characterized in that an upper camera and a lower camera are arranged right above a pipe, the centers of the two cameras and the axis of the pipe are located in the same vertical plane, the distance H1 between the upper camera and the lower camera and the distance H2 between the lower camera and the center of the pipe are measured, the focal lengths L1 and L2 of the upper camera and the lower camera are obtained at the same time, corresponding pipe edge information K1 and K2 are obtained according to pictures of the pipe respectively shot by the upper camera and the lower camera, and finally the method is carried out according to an equation set:

；

；

R1=R2；

r1 and R2 are solved to obtain the diameter of the pipe.

2. A pipe diameter measuring device based on machine vision is characterized by comprising a vertical support and a chassis which are vertically connected, wherein the support is horizontally connected with an upper cross rod and a lower cross rod; the two cross rods are respectively installed with the vertical support in an adjustable mode through the clamping devices, and the vertical distance between the camera and the pipe and the extension length of the camera in the horizontal direction are continuously adjusted through the clamping devices.

3. The pipe diameter measuring device based on the machine vision as claimed in claim 2, wherein the clamping device comprises a clamping block and two locking screws, the clamping block is provided with a transverse through hole and a vertical through hole for inserting the installation cross rod and the support, the locking screws which can be screwed in are respectively installed along the horizontal direction perpendicular to the transverse through hole and the vertical through hole, and the end heads of the locking screws are provided with rubber cushion blocks.

4. The machine vision based pipe diameter measuring device according to claim 3, wherein the specific measuring operation steps of the machine vision based pipe diameter measuring device are as follows:

1) the whole device is arranged on one side of a pipe to be measured, the height H2 from the center line of the pipe to a camera B on a cross bar below and the focal length L2 of the camera are adjusted, so that the pipe occupies most of the shooting range of the camera B, the extension length of the cross bar below is adjusted through a clamping device, and a vertical line passing through the center of the camera B is intersected with the axis of the pipe;

2) adjusting the height from a camera A on the upper cross bar to a camera B and the focal length L1 of the camera A to enable the pipe to occupy most of the shooting range of the camera A, and adjusting the extension length of the upper cross bar to enable a vertical line passing through the center of the camera A to be intersected with the axis of the pipe;

3) connecting two high-definition cameras with a computer, processing the images of the pictures, extracting the edge information K1 and K2 of the pipe, and substituting the obtained data into an equation set

；

；

R1=R2；

R1 and R2 are solved to obtain the diameter of the pipe.

5. The machine vision-based pipe diameter measuring device according to claim 4, wherein the specific adjusting process of the extending length of the camera A and the camera B is as follows: and (3) processing the images of the pipe shot by the camera, if two edge lines of the images are symmetrical about the central line of the camera, successfully debugging the horizontal extension length of the camera, and if the two edge lines are not symmetrical about the central line of the camera, repeating the steps until the debugging is successful.

Technical Field

The invention relates to a pipe diameter measuring device based on machine vision and a measuring method thereof, which are non-contact diameter measuring devices and belong to the field of pipe measurement.

Background

In the production process of the pipe, particularly the production of welded pipes (including straight seam welded pipes and spiral seam welded pipes), the diameter of the welded pipe is often unstable due to the special production process, and the diameter error range of the welded pipe needs to be controlled within 0.5 percent. In order to ensure the production quality of products, the diameter of a moving pipe needs to be measured in real time.

At present, most manufacturers send people specially to detect the manual diameter on an assembly line, the machine is stopped to detect and adjust when the diameter is found not to meet the requirement, waste products are easily generated due to the fact that the pipe diameter exceeds the standard, a traditional measuring method has certain limitation, abrasion is caused to a workpiece in the measuring process, and the measuring precision is not high. The practical application value of the pipe diameter real-time measuring system is not questionable, a large amount of development and research have been carried out at home and abroad in recent years, and a great deal of achievements are obtained, but the research, development, popularization and use of the project at home are relatively weak.

There are some non-contact diameter measuring devices that have been used in manufacturing processes. The invention patent with patent number CN 108344370A adopts a mode of combining a vision sensor and laser to measure the diameter of the pipe. The measuring device is complex, the fixing device for the pipe has certain requirements, and the central line position of the pipe is changed along with the diameter change of the pipe, so that the measuring result is greatly influenced. Patent CN 201488707 describes a tubular product pipe diameter measuring device, adopts the laser to stretch into the inside internal diameter of tubular product and measures, but its external diameter that can't accurate measurement tubular product.

The invention relates to a real-time pipe diameter measuring device, which combines two cameras, measures the diameter by using the optical principle that the cameras shoot the side surface of a cylindrical object to form images, can timely find and adjust corresponding production process parameters when the diameter of a pipe is slightly changed, does not need to be interrupted in production, and greatly improves the quality and the production efficiency of the pipe.

Disclosure of Invention

The invention aims to realize real-time measurement of the diameter of a pipe, and further provides a pipe diameter measuring device and a pipe diameter measuring method based on machine vision.

The invention adopts the following technical scheme:

a method for measuring the diameter of a pipe based on machine vision comprises the steps of installing an upper camera and a lower camera right above the pipe, enabling the centers of the two cameras and the axis of the pipe to be located on the same vertical plane, measuring the distance H1 between the upper camera and the lower camera and the distance H2 between the lower camera and the center of the pipe, obtaining the focal lengths L1 and L2 of the upper camera and the lower camera at the moment, obtaining corresponding pipe edge information K1 and K2 according to pictures of the pipe respectively shot by the upper camera and the lower camera, and finally obtaining the pipe edge information according to an equation set:

；

；

R1=R2；

r1 and R2 are solved to obtain the diameter of the pipe.

A pipe diameter measuring device based on machine vision comprises a vertical support and a chassis which are vertically connected, wherein an upper cross rod and a lower cross rod are horizontally connected to the support, a camera is respectively installed at the ends of the two cross rods on the same side, and the two cameras are positioned right above the central line of a pipe to be measured; the two cross rods are respectively installed with the vertical support in an adjustable mode through the clamping devices, and the vertical distance between the camera and the pipe and the extension length of the camera in the horizontal direction are continuously adjusted through the clamping devices.

The clamping device comprises a clamping block and two locking screws, a transverse through hole and a vertical through hole which are used for inserting the installation cross rod and the support are formed in the clamping block, the locking screws which can be screwed in are respectively installed in the transverse through hole and the vertical through hole in a manner of being perpendicular to the transverse through hole and the vertical through hole in the horizontal direction, and rubber cushion blocks are arranged at the ends of the locking screws.

The specific measurement operation steps of the pipe diameter measuring device based on machine vision are as follows:

1) the whole device is arranged on one side of a pipe to be measured, the height H2 from the center line of the pipe to a camera B on a cross bar below and the focal length L2 of the camera are adjusted, so that the pipe occupies most of the shooting range of the camera B, the extension length of the cross bar below is adjusted through a clamping device, and a vertical line passing through the center of the camera B is intersected with the axis of the pipe;

2) adjusting the height from a camera A on the upper cross bar to a camera B and the focal length L1 of the camera A to enable the pipe to occupy most of the shooting range of the camera A, and adjusting the extension length of the upper cross bar to enable a vertical line passing through the center of the camera A to be intersected with the axis of the pipe;

3) connecting two high-definition cameras with a computer, processing the images of the pictures, extracting the edge information K1 and K2 of the pipe, and substituting the obtained data into an equation set；；R1=R2；

R1 and R2 are solved to obtain the diameter of the pipe.

The specific adjusting process of the extending length of the camera A and the camera B is as follows: and (3) processing the images of the pipe shot by the camera, if two edge lines of the images are symmetrical about the central line of the camera, successfully debugging the horizontal extension length of the camera, and if the two edge lines are not symmetrical about the central line of the camera, repeating the steps until the debugging is successful.

The invention can realize real-time online measurement of the pipe in operation, can accurately measure the diameter of the pipe even if the pipe has radial run-out in operation, does not damage the pipe in the measurement process, and improves the production efficiency.

Compared with manual measurement, the device can realize on-line measurement, improve the measurement efficiency, ensure the measurement accuracy and real-time performance, and indirectly ensure the production quality by measuring on the premise of not changing the original production line.

The invention utilizes natural light source and high-definition camera to measure, can be applied to more complicated production lines, and because of production error and simple and easy fixing device of the pipe, the axial line position of the pipe is indefinite, in order to solve the problem that the axial line position of the pipe is indefinite, the invention uses two cameras to measure, measures the diameter under the condition of knowing the relative distance between the two cameras.

Drawings

FIG. 1 is a schematic view of the measurement principle of the apparatus of the present invention;

FIG. 2 is a schematic view of the external structure of the apparatus of the present invention;

FIG. 3 is a sectional view of a connection structure of a cross bar and a vertical bar;

in the figure: 1-a support, 2-a cross bar A, 3-a first clamping device, 4-a cross bar B, 5-a second clamping device, 6-a chassis, 7-an adjusting camera A, 8-a third clamping device, 9-a camera B, 10-a fourth clamping device and 11-a pipe;

12-a first locking screw, 13-a first rubber cushion block, 14-a clamping block, 15-a second rubber cushion block and 16-a second locking screw.

Detailed Description

The pipe diameter measuring device based on machine vision as shown in fig. 2 comprises a vertical support and a chassis which are vertically connected, wherein an upper cross rod and a lower cross rod (a cross rod A and a cross rod B) are horizontally connected to the support, one camera is respectively installed at the ends of the two cross rods on the same side, and the two cameras (the camera A and the camera B) are positioned right above the central line of a pipe to be measured; the two cross rods are respectively installed with the vertical support in an adjustable mode through the clamping devices, and the vertical distance between the camera and the pipe and the extension length of the camera in the horizontal direction are continuously adjusted through the clamping devices. The invention uses the combination of the natural light source and the two high-definition cameras to carry out non-contact measurement, has simple device and low cost, and can remove the measurement error generated by the circle center jump of the pipe.

The measuring steps of the device are as follows:

(1) the base position is adjusted manually, makes the centre point of two high-definition cameras and the centre of a circle of tubular product on same vertically line: the height of the camera A and the extending distance of the camera are adjusted through the adjusting device (3), meanwhile, the focal distance of the camera is adjusted to enable the pipe to occupy most of the picture of the camera A, and a perpendicular line passing through the imaging center of the camera passes through the center line of the pipe. The height and the extending distance of the camera B are adjusted through the adjusting device (5), meanwhile, the focal distance of the camera is adjusted, so that the pipe occupies most of the picture of the camera B, and a perpendicular line passing through the imaging center of the camera passes through the center line of the pipe. The height difference H1 of camera a and camera B was recorded accurately.

(2) The camera is connected with the computer through a data line, and pictures shot by the camera A and the camera B are transmitted to the computer in real time.

(3) And processing the pictures transmitted to the computer, extracting the edge profile of the pipe, importing the data obtained by processing the images into a visual identification system, and calculating the diameter of the pipe.

The following are examples of measurements based on the apparatus of the present invention:

firstly, a standard pipe with a known diameter is placed, the base (6) is placed on the ground, and the position of the base is adjusted, so that the camera A and the camera B are placed right above the pipe.

Adjusting the horizontal extension length of the cross bar A by adjusting the cross bar A control device (3) to enable the perpendicular line passing through the optical center of the camera to be intersected with the axis of the pipe.

The horizontal extension length of the cross bar B is adjusted through adjusting the position control device (5) of the cross bar B, so that the perpendicular line passing through the optical center of the camera is intersected with the axis of the pipe.

The method comprises the steps of moving out a standard pipe with a known diameter, placing the pipe to be measured on a pipe fixing device, adjusting the height of the cross rod A in the vertical direction through a position control device (3) for adjusting the cross rod A, and adjusting the focal length of a camera A at the same time, so that most of the area in the picture of the camera A is occupied by the pipe.

The height of the cross bar B in the vertical direction is adjusted by adjusting the position control device (5) of the cross bar B, and meanwhile, the focal length of the camera B is adjusted, so that most of the area in the picture of the camera B is occupied by the pipe.

The focal lengths L1 and L2 of camera A and camera B are recorded. And recording the vertical distance H1 between the cross bar A and the cross bar B according to the scale on the bracket (1).

And respectively connecting the camera A and the camera B with a computer, carrying out picture processing on pictures shot by the camera A and the camera B by the computer to obtain edge information of the pipe, wherein the edge information of the pipe obtained according to the pictures shot by the camera A and the camera B is K1 and K2.

The values of K1, K2 and H1 are substituted into the system of equations

R1, R2 and H1 are solved to obtain the radius and the height H1 of the pipe. In the present device, H1 is a measurable variable, so that no error is generated in the measurement result even if there is a radial run-out problem with the center of the pipe in operation.

The invention has the advantages of simple structure and low cost, can be applied to various complex production environments, has low requirements on the fixing mode and the fixing position of the pipe, and can be applied to the production or operation process of the pipe. The measuring efficiency is improved, the production efficiency is indirectly improved, and the measurement is not influenced by the jumping in the running process.

We used this apparatus to measure pipes of 450 and 320 diameters, as shown in the table below.

Measurement example 1

Measurement example 2

According to the measurement example, the device can effectively control the measurement error to be below 0.5 percent, and the measurement precision meets the production requirement.