CN101571379A - Method for measuring diameter and straightness accuracy parameters of seamless round steel pipe - Google Patents

Abstract

A method for measuring the diameter and straightness parameters of a seamless circular steel pipe: complete the calibration of the parameters of the multi-line structured light vision sensor composed of a camera and a multi-line laser projector; lay out multiple lines near the seamless circular steel pipe to be measured Structured light vision sensor; the computer separately controls the laser projector to project the structured light plane to the measured section of the seamless circular steel pipe, the camera collects the light strip image on the surface of the seamless circular steel pipe, performs light strip image processing, and calculates the different cross section according to the measurement model Three-dimensional coordinates; determine the center of the ellipse in the space section, realize the measurement of the straightness of the seamless circular steel pipe, and construct the dynamic virtual central axis of the seamless circular steel pipe; construct the dynamic virtual projection datum of the space section ellipse; transform the space section ellipse to the dynamic virtual The projection datum plane is forward projected, and the circle fitting is performed on the datum plane to obtain the cross-sectional circle of the steel pipe. The invention can realize the online, real-time, automatic and non-contact measurement of the diameter and straightness parameters of the seamless circular steel pipe.

Description

A method for measuring the diameter and straightness parameters of seamless circular steel pipes

technical field

The invention relates to a method for measuring the diameter and straightness parameters of a seamless circular steel pipe. In particular, it relates to a method for measuring the diameter and straightness parameters of a seamless circular steel pipe based on a multi-line structured light vision sensor.

Background technique

Seamless circular steel pipe is a widely used steel, such as precision internal for structures, fluid transportation, low, medium and high pressure boilers, ships, high pressure fertilizer equipment, petroleum cracking, gas cylinders, hydraulic props, diesel engines, hydraulic and pneumatic cylinders Cylinders, automobile half shaft casings, etc. For different seamless circular steel pipe products and applications, there are different index parameter requirements. Among them, the conformity of processing parameters such as diameter and straightness of seamless circular steel pipe products with design indicators is a direct reflection of its quality. Therefore, the measurement of parameters such as the diameter and straightness of the seamless circular steel pipe is very important.

The traditional measurement methods of geometric parameters of seamless circular steel pipes are mostly based on manual, off-line, and random inspection methods. The labor intensity of workers is high, the efficiency is low, and the real-time performance is poor. The production line cannot be monitored and adjusted in a timely and effective manner, which seriously affects the seamless The modernization of seam circular steel pipe production has limited the further improvement of product quality.

With the development of optics, electronics, computer, image processing and other technologies, a new measurement technology - visual measurement technology has emerged. Compared with traditional measurement technology, visual measurement technology has the advantages of non-contact, online, fast speed and high precision. With the in-depth research of visual measurement technology, an application attempt has been made to realize the measurement of geometric parameters of seamless circular steel pipes based on single-line structured light visual sensors. However, in the application of measuring the geometric parameters of seamless circular steel pipes based on the single-line structured light vision sensor, it is necessary to ensure that the structured light plane projected by the laser is perpendicular to the central axis of the seamless circular steel pipe when measuring the diameter, which greatly increases the system installation. Difficulty of debugging. When realizing straightness measurement, multiple single-line structured light vision sensors are required, and special instruments and equipment are needed for global calibration of the system to achieve the unification of the measurement coordinate system of each sensor, which greatly increases the complexity of system construction and application costs. , reducing the availability of the system.

Contents of the invention

The technical problem to be solved by the present invention is to provide a device that is easy to install, easy to adjust, and has the characteristics of fast measurement speed, non-contact, automatic, online, can be used in harsh environments, and has high measurement accuracy. A method for measuring the diameter and straightness parameters of seamless circular steel pipes that meets the online, real-time, automatic, and non-contact measurement requirements for parameters such as diameter and straightness of seamless circular steel pipes.

The technical solution adopted in the present invention is: a method for measuring the diameter and straightness parameters of a seamless circular steel pipe, comprising the following steps:

(1) A multi-line structured light vision sensor is composed of a camera and a multi-line laser projector, and the calibration of the parameters of the camera and the multi-line structured light vision sensor is completed;

(2) According to the working distance of the multi-line structured light visual sensor and the measurement depth of field, the multi-line structured light visual sensor is arranged and fixed at an appropriate position near the seamless circular steel pipe to be tested;

(3) The computer controls the multi-line laser projector in the multi-line structured light vision sensor to project the structured light plane to the measured section of the seamless circular steel pipe through the multi-line structured light vision sensor controller;

(4) The computer controls the camera of the multi-line structured light visual sensor arranged by the multi-line structured light visual sensor controller to collect the light strip image on the surface of the seamless circular steel pipe;

(5) The computer performs light strip image processing, and calculates the three-dimensional coordinates of different sections according to the measurement model of the multi-line structured light vision sensor;

(6) Fit the space section ellipse through three-dimensional data measured in different sections, determine the center of the space section ellipse, use 3 or more space section ellipse centers, and combine the minimum envelope straightness evaluation theory to realize the straightness of seamless circular steel pipes Measurement;

(7) Using 3 or more space section ellipse centers, combined with the least squares space straight line fitting algorithm to construct the dynamic virtual central axis of the seamless circular steel pipe;

(8) Pass any point on the virtual central axis of the seamless circular steel pipe as a virtual space vertical plane, that is, construct a space section ellipse dynamic virtual projection datum plane;

(9) Forward project the space section ellipse to the dynamic virtual projection datum plane, and perform circle fitting on the datum plane to obtain the cross-sectional circle of the steel pipe, thereby realizing the measurement of the diameter of the seamless circular steel pipe.

The multi-line laser projector projects three or more rays.

The multi-line laser projector is a laser projector that generates multiple projection lines from one projector, or a combination of multiple independent one-line laser projectors.

The calibration parameters of the camera described in step 1 include: effective focal length, center of image plane, distortion coefficient and scale factor.

The calibration parameters of the multi-line structured light vision sensor described in step 1 include: the structured light plane equation.

The multi-line laser projector projection described in step 3 is simultaneous projection or sequential projection.

The method for measuring the diameter and straightness parameters of a seamless circular steel pipe according to the present invention can realize the online, real-time, automatic and non-contact measurement of the diameter and straightness parameters of the seamless circular steel pipe, which is conducive to the formation of production and measurement closed-loop control , can greatly improve production efficiency and product quality, and effectively reduce the labor intensity of workers.

By adopting the multi-line structured light vision sensor, the present invention can realize the dynamic construction of the virtual central axis of the seamless circular steel pipe and the virtual projection reference plane, and then realize the projection of the structured light projection ellipse section to the dynamic reference plane, so as to obtain an accurate representation of the seamless circle The perfect circular section of the steel pipe, thus avoiding the restriction that the structured light plane projected by the laser is strictly perpendicular to the central axis of the seamless circular steel pipe when the traditional single-line structured light vision sensor is used to measure the diameter of the seamless circular steel pipe. In addition, the multi-line structured light vision sensor itself is equivalent to multiple single-line structured light vision sensor systems in coordinate system 1, thus avoiding the need to use special equipment when traditionally using line structured light vision sensors to measure the straightness of seamless circular steel pipes Limitations for doing global calibration. Therefore, the present invention is convenient to install and simple to adjust, and can be popularized and applied in actual production.

Description of drawings

Fig. 1 is a structural schematic diagram of a multi-line structured light vision sensor (3 projection lines);

Fig. 2 is a schematic diagram of a line structured light vision sensor measurement model;

Fig. 3 is a schematic diagram of a seamless circular steel pipe diameter and straightness parameter measurement system based on a multi-line structured light vision sensor.

in:

1: Multi-line structured light vision sensor housing 2: Camera

3: Laser projector 4: The first line of structured light

5: The second line of structured light 6: The third line of structured light

7: Structured light plane 8: Image plane

9: Seamless circular steel pipe 10: Multi-line structured light vision sensor

11: Virtual central axis of seamless circular steel pipe 12: Virtual projection reference plane

Detailed ways

A method for measuring the diameter and straightness parameters of a seamless circular steel pipe according to the present invention will be described in detail below in conjunction with the accompanying drawings of the embodiments.

A method for measuring the diameter and straightness parameters of a seamless circular steel pipe of the present invention is to install a multi-line structured light vision sensor at a suitable position (refer to the working distance of the sensor) of the seamless circular steel pipe to be measured, and the structure of laser projection in the sensor The central axis of the light plane and the seamless circular steel pipe is not required to be strictly vertical, and the installation of the sensor has no strict pose requirements; the measurement of the straightness of the seamless circular steel pipe and the dynamic construction of the virtual central axis: the multi-line structured light vision sensor is used to realize it simultaneously The measurement of three-dimensional data of multiple different sections of seamless circular steel pipes, fitting the space section ellipse through the three-dimensional data measured by different sections, and determining the center of the space section ellipse, combined with the minimum envelope straightness evaluation theory to realize the straightness of seamless circular steel pipes At the same time, use the space section ellipse center fitting to construct the dynamic virtual central axis of the seamless circular steel pipe; the dynamic construction of the space section ellipse virtual projection reference plane: pass through any point on the virtual central axis of the seamless circular steel pipe as a virtual space The vertical plane is defined as the dynamic virtual projection datum plane of the space section ellipse; the measurement of the diameter of the seamless circular steel pipe: project the space section ellipse forward to the dynamic virtual projection datum plane, and perform circle fitting on the datum plane to obtain The cross-section of the steel pipe is round, so as to realize the measurement of the diameter of the seamless circular steel pipe. Specifically include the following steps:

(1) A multi-line structured light vision sensor is formed by a camera and a multi-line laser projector, and the calibration of the parameters of the camera and the multi-line structured light vision sensor is completed; the projected rays of the multi-line laser projector are 3 or 3 or more.

The multi-line laser projector can be a laser projector that generates multiple projection lines, or a combination of multiple independent one-line laser projectors.

(2) According to the working distance of the multi-line structured light vision sensor and the measurement depth of field, the multi-line structured light vision sensor is arranged and fixed at an appropriate position near the seamless circular steel pipe to be tested, and the on-site thermal protection treatment is carried out;

(3) The computer controls the multi-line laser projector in the multi-line structured light vision sensor to project the structured light plane to the measured section of the seamless circular steel pipe through the multi-line structured light vision sensor controller (can be projected simultaneously or sequentially) ;

(4) The computer controls the camera of the multi-line structured light visual sensor arranged by the multi-line structured light visual sensor controller to collect the light strip image on the surface of the seamless circular steel pipe (the camera image acquisition should be matched with the laser projection);

(5) The computer performs light strip image processing, and calculates the three-dimensional coordinates of different sections according to the measurement model of the multi-line structured light vision sensor;

(6) Fit the space section ellipse through three-dimensional data measured in different sections, determine the center of the space section ellipse, use 3 or more space section ellipse centers, and combine the minimum envelope straightness evaluation theory to realize the straightness of seamless circular steel pipes Measurement;

(7) Using 3 or more space section ellipse centers, combined with the least squares space straight line fitting algorithm to construct the dynamic virtual central axis of the seamless circular steel pipe;

(8) Pass any point on the virtual central axis of the seamless circular steel pipe as a virtual space vertical plane, that is, construct a space section ellipse dynamic virtual projection datum plane;

(9) Forward project the space section ellipse to the dynamic virtual projection datum plane, and perform circle fitting on the datum plane to obtain the cross-sectional circle of the steel pipe, thereby realizing the measurement of the diameter of the seamless circular steel pipe.

Describe in detail below in conjunction with accompanying drawing:

As shown in FIG. 1 , a multi-line structured light vision sensor 10 is composed of a camera and a 3-line laser projector. Before measurement and application, the multi-line structured light vision sensor 10 needs to be calibrated for parameters such as the effective focal length of the camera, the center of the image plane, the distortion coefficient, and the scale factor, and the structured light plane equation in the multi-line structured light vision sensor.

The mathematical model of the linear structured light vision sensor shown in Figure 2 assumes that the three-dimensional world coordinate system is o _w x _w y _w z _w , the camera coordinate system is o _c x _c y _c z _c , and the image plane π _n coordinate system is o _n X _n Y _n . Taking the camera coordinate system as the sensor measurement coordinate system, the mathematical model of the line structured light vision sensor can be expressed by the equation of the structured light plane π _s in the camera coordinate system. Assume that under the coordinate system o _c x _c y _c z _c , the equation coefficient of the light plane π _s is V=[a b c d], and the coordinate of any point P on the light plane is P _c =[x _c y _c z _c ] ^T , The corresponding homogeneous coordinates are ${\tilde{P}}_c={\left[\begin{array}{cccc}{x}_c& {\mathrm{the\; y}}_c& z_c& 1\end{array}\right]}^T,$ Then the light plane equation can be expressed as:

$\mathrm{<span\; class="notranslate">\; V</span>}<span\; class="notranslate">\; \&CenterDot;</span>{\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; P</span>}}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

If the ideal projection normalized image homogeneous coordinates of point P are known ${\tilde{P}}_{\mathrm{no}}={\left[\begin{array}{ccc}{x}_{\mathrm{no}}& Y_{\mathrm{no}}& 1\end{array}\right]}^T,$ Then the equation of a straight line passing through the optical center of the camera and this image point can be expressed as:

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; o</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; -</span>{\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; P</span>}}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Then the combination of (1) and (2) is the mathematical model of the linear structured light vision sensor.

The camera 2 coordinate system in the multi-line structured light vision sensor 10 is defined as the sensor measurement coordinate system. The multi-line structured light vision sensor 10 shown in FIG. 1 is composed of a camera 2 and a 3-line laser projector 3, so it is equivalent to three single-line structured light vision sensors in the first measurement coordinate system.

First, according to the working distance and measurement depth of field of the multi-line structured light visual sensor 10, the multi-line structured light visual sensor 10 is arranged and fixed at a suitable position of the seamless circular steel pipe to be measured to construct a measurement system. Figure 3 is a schematic diagram of a seamless circular steel pipe diameter and straightness parameter measurement system based on a multi-line structured light vision sensor.

During measurement, the laser projector 3 of the multi-line structured light vision sensor 10 projects the first line structured light 4, the second line structured light 5, and the third line structured light 6 to the surface of the seamless circular steel pipe 9, forming three bright stripes. The computer collects the bright fringe image through the camera 2, and processes the light fringe image to obtain the center image coordinates of the three bright fringes. On the basis of the center image coordinates of the three bright stripes, combined with the calibration parameters of the camera 2, the multi-line structured light vision sensor 10 and the mathematical model of the line structured light vision sensor 10, the center space coordinates of the three bright stripes are calculated. The space section ellipse was fitted by the center space coordinates of the three bright stripes, and the center of the space section ellipse was obtained. According to the minimum envelope straightness evaluation principle, the straightness parameters of the seamless circular steel pipe 9 are evaluated based on the obtained elliptical centers of the three space sections, and the virtual central axis 11 of the seamless circular steel pipe is constructed at the same time. Pass through any point on the virtual central axis 11 of the seamless circular steel pipe, and make a vertical plane of the virtual central axis to construct a virtual projection datum plane 12 . The ellipse data of the space section of the seamless circular steel pipe 9 is forward projected to the virtual projection reference plane 12 to obtain the perfect circular section of the seamless circular steel pipe 9, and the diameter parameter measurement of the seamless circular steel pipe is realized through plane circle fitting.

The method for measuring the diameter and straightness parameters of seamless circular steel pipes based on the multi-line structured light visual sensor of the present invention is a brand-new multi-line structured light visual sensor to realize real-time, real-time measurement of the diameter and straightness parameters of seamless circular steel pipes. The online measurement method and device are unique in that: based on the multi-line structured light vision sensor, the virtual central axis of the seamless circular steel pipe and the virtual projection reference plane are dynamically constructed. The circular section of the circular steel pipe avoids the limitation that the structured light plane projected by the laser is strictly perpendicular to the central axis of the seamless circular steel pipe when the traditional linear structured light vision sensor is used to measure the diameter of the seamless circular steel pipe. At the same time, the multi-line structured light vision sensor itself is equivalent to multiple single-line structured light vision sensor systems in the first coordinate system, thus avoiding the need for special instruments and equipment when the traditional line structured light vision sensor is used to measure the straightness of seamless circular steel pipes. Limitations of Global Calibration.

Claims (6)

1. A method for seamless circular steel pipe diameter and straightness parameter measurement, is characterized in that, comprises the steps: (1) A multi-line structured light vision sensor is composed of a camera and a multi-line laser projector, and the calibration of the parameters of the camera and the multi-line structured light vision sensor is completed; (2) According to the working distance of the multi-line structured light visual sensor and the measurement depth of field, the multi-line structured light visual sensor is arranged and fixed at an appropriate position near the seamless circular steel pipe to be tested; (3) The computer controls the multi-line laser projector in the multi-line structured light vision sensor to project the structured light plane to the measured section of the seamless circular steel pipe through the multi-line structured light vision sensor controller; (4) The computer controls the camera of the multi-line structured light visual sensor arranged by the multi-line structured light visual sensor controller to collect the light strip image on the surface of the seamless circular steel pipe; (5) The computer performs light strip image processing, and calculates the three-dimensional coordinates of different sections according to the measurement model of the multi-line structured light vision sensor; (6) Fit the space section ellipse through three-dimensional data measured in different sections, determine the center of the space section ellipse, use 3 or more space section ellipse centers, and combine the minimum envelope straightness evaluation theory to realize the straightness of seamless circular steel pipes Measurement; (7) Using 3 or more space section ellipse centers, combined with the least squares space straight line fitting algorithm to construct the dynamic virtual central axis of the seamless circular steel pipe; (8) Pass any point on the virtual central axis of the seamless circular steel pipe as a virtual space vertical plane, that is, construct a space section ellipse dynamic virtual projection datum plane; (9) Forward project the space section ellipse to the dynamic virtual projection datum plane, and perform circle fitting on the datum plane to obtain the cross-sectional circle of the steel pipe, thereby realizing the measurement of the diameter of the seamless circular steel pipe. 2 . The method for measuring the diameter and straightness parameters of a seamless circular steel pipe according to claim 1 , wherein the multi-line laser projector projects three or more rays. 3 . 3. The method for measuring the diameter and straightness parameters of a seamless circular steel pipe according to claim 1, wherein the multi-line laser projector is a laser projector that generates multiple projection lines with one projector , or a combination of multiple independent line laser projectors. 4. The method for measuring the diameter and straightness parameters of a seamless circular steel pipe according to claim 1, wherein the calibration parameters of the camera described in step 1 include: effective focal length, center of image plane, distortion coefficient and scale factor. 5. The method for measuring the diameter and straightness parameters of a seamless circular steel pipe according to claim 1, wherein the calibration parameters of the multi-line structured light vision sensor described in step 1 include: structured light plane equation . 6. The method for measuring the diameter and straightness parameters of a seamless circular steel pipe according to claim 1, wherein the multi-line laser projector projection in step 3 is simultaneous projection or sequential projection.

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