Title of Invention	A DEVICE FOR REAL TIME MEASUREMENT OF DISTORTION REMOTELY DURING AN ARC WELDING PROCESS.
Abstract	Accordingly there is proposed a device, which will be able to measure the distortion at a particular location during welding from a far-away place. The device consists of a laser light line source (1), a camera (2), a computer (3) and a reference plate (5). The laser light source emits a line which allows to fall on the surface on the job where the distortion is to be measured. A highly sensitive camera acquires the image at that location on the job where the laser light disposed, an angle of less than 30 degree with reference to the surface of the job. The image consists of the laser line which has a shape according to the profile of the job surface. The image of the laser line appears a straight when the job is in a single plane without distortion. If there is a distortion on the job, the line changes it shape. By finding the difference between the two lines, the distortion can be calculated. Before starting the weld, the initial image should be collected and stored. It should be compared with the new acquired image and the distortion can be calculated from the difference in the line of projected image at that location.

Title of Invention

A DEVICE FOR REAL TIME MEASUREMENT OF DISTORTION REMOTELY DURING AN ARC WELDING PROCESS.

Abstract

Accordingly there is proposed a device, which will be able to measure the distortion at a particular location during welding from a far-away place. The device consists of a laser light line source (1), a camera (2), a computer (3) and a reference plate (5). The laser light source emits a line which allows to fall on the surface on the job where the distortion is to be measured. A highly sensitive camera acquires the image at that location on the job where the laser light disposed, an angle of less than 30 degree with reference to the surface of the job. The image consists of the laser line which has a shape according to the profile of the job surface. The image of the laser line appears a straight when the job is in a single plane without distortion. If there is a distortion on the job, the line changes it shape. By finding the difference between the two lines, the distortion can be calculated. Before starting the weld, the initial image should be collected and stored. It should be compared with the new acquired image and the distortion can be calculated from the difference in the line of projected image at that location.

Full Text	FIELD OF INVENTION The invention generally relates to a device to measure the distortion produced during welding using computer vision. BACKGROUND OF THE INVENTION In arc welding process, a high concentration of heat is generated in the area where welding takes place and due to this heat effect, a change in shape of welded material takes place and is called distortion. This distortion, if exceeds the limit, makes the job unsuitable for the application. Hence distortion is a phenomenon which shall be controlled as much as possible. To control the distortion, it requires to be measured. If the distortion is monitored during welding, the weld sequence can be altered in order to minimize distortion. If the distortion is measured after welding, in that case, the job will be suitably corrected based on the measurement of distortion. Hence the invention has the objective of measuring the distortion at a particular location at different times when the welding is in progress or after completion of weld. The Conventional way of measurement involves either mechanical or electrical based methods. In mechanical measurement method, standard measurement instruments such a vernier calipers, height gages and dial calipers are employed. If the component is large, special mechanical arrangements are made which included one of the above instruments. In the electrical measurement methods, strain gages or linear variable differential transformers (LVDTs) are employed. In the first method, a strain gage is bonded to the component and the strain is read through a data recording device. This is very accurate but measures distortion only in a small zone. In LVDTs, the measurement: is local and covers only a small area. In both cases of electrical measurement, contact with the product is essential and there is a limitation on the temperature of the job at which measurement is possible. A prior Patent US 316504 which discloses an invention wherein the marking of wafer is identified and features from it are analyzed and taken into consideration. This involves acquisition of the image of the wafer and analysis of the features in only one plane and the proposed invention uses a laser line which produces information on the height direction. Another prior Patent EP 1986046A1 describes a method of finding the focus of the image and adjusting the camera to obtain the focus automatically. The object of this patent is to set the correct focus by extracting features of the image and adjusting the same. However, in the present invention is for the measurement of distortion and not adjusting the focus of camera. A further prior Patent WO2008153721A1 describes a method of extracting the feature of a three dimensional object. In this method, multiple cameras are employed for obtaining the three different images and analyzing them and extracting the features in the image. However, in the present invention, a laser source is employed for finding the three dimensional features. OBJECTS OF THE INVENTION It is therefore an object of the present invention to propose a device which can measure distortion during welding. Another object of the present invention is to propose a device which measures the distortion after welding. A further object of the present invention is to propose a device which measures the distortion in the presence of the high temperature in the region where welding took place. A still further object of the present invention is to propose a device which develops a non contact method of measuring the distortion. Yet further object of the present invention is to propose a device which measures the distortion from a remote location. Yet another object of the present invention is to propose a device which measures the distortion in a hazardous environment. SUMMARY OF THE INVENTION Accordingly there is proposed a device, which will be able to measure the distortion at a particular location during welding from a far-away place. The device consists of a laser light line source (1), a camera (2), a computer (3) and a reference plate (5). The laser light source emits a line which allows to fall on the surface on the job where the distortion is to be measured. A highly sensitive camera acquires the image at that location on the job where the laser light disposed, an angle of less than 30 degree with reference to the surface of the job. The image consists of the laser line which has a shape according to the profile of the job surface. The image of the laser line appears a straight when the job is in a single plane without distortion. If there is a distortion on the job, the line changes it shape. By finding the difference between the two lines, the distortion can be calculated. Before starting the weld, the initial image should be collected and stored. It should be compared with the new acquired image and the distortion can be calculated from the difference in the line of projected image at that location. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Fig.1 - shows an embodiment of the device according to the invention Fig.2 - shows the image of profile of the laser line when incident on a plane surface Fig.3 - shows the profile of the laser line when incident on a curved reference plate or job Fig.4 - shows the profile of the laser line when incident on a curved or distorted surface Fig.5 - shows reference plate DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION The device comprises of four components, a) a laser line source (1) is illuminating the location at a given area on the job which will project a line on the surface. b) a camera (2) which is kept at an angle less than 30 degree to acquire the line image formed on the job at a specified location and image is transferred to the computer in a suitable format and projected on monitor. c) a computer (3) processes the image and compares the original line image recorded before welding at the same spot and gives the difference of the dimension in the y-axis which quantifies the distortion at the spot. d) a portable reference plate (5) is engaged for setting the reference image when the absolute value of the profile is required. Principle of equipment operation The line source produces a laser light which is a straight line. When this line is projected on a plane surface, and when this line is captured by a camera at an angle, then the image captured by the camera is a straight line (Fig.2). If the laser line is projected on a bent surface and when this line is captured at the same angle by a camera, then the image captured by the camera on the laser line will be bent line (Fig.4). The height of the bend can be correlated by the change in the straightness a) When the level of distortion is measured with reference to the original product profile ,i.e., when the amount of distortion is required to be analyzed then the original profile of the product is used as the reference: The laser line source projects a straight line on the job surface. The camera is focused to the spot and the image is acquired by the camera, is further projected to computer. This forms the reference image (Fig.3). The welding is undertaken and the distortion of the weld is required to be measured, then the image of the laser line on the job is collected and the co-ordinates are measured by computer software. The final distortion is measured by correlating the difference between the reference and measured co-ordinates of the line. The measurement is taken periodically and the trend in the distortion estimated. b) When the absolute amount of distortion is to be measured with reference to a fixed plane: The laser line source projects a straight line on the plane reference (5). The welding is undertaken and the distortion of the weld is required to be measured, the image of the laser line on the job is collected and the co-ordinates are measured by computer software. The final distortion is measured by the difference between the reference and measured co-ordinates of the line. The measurement is taken periodically and the trend in the distortion estimated. The final distortion of a product can be measured with reference to the original shape of the product or a fixed reference and can be used for correction. WE CLAIM 1. A device for measurement of distortion during welding comprises: - a laser line source (1) is illuminating the location on the surface of job (4); - a camera (2) disposed at less than 30° angle with reference to the surface of the job to capture the line image formed on the job at a specific location and transferring the image to a computer in a suitable format; - a computer processes the image and focus on the monitor; and - a portable reference plate (5) is engaged for setting the reference image Characterised in that the said images are compared with original line image recorded before welding and images obtained after welding at the same spot and produces a difference of dimension in the y-axis which quantifies the distortion at that spot. 2. The process of measuring the distortion by the device comprises the steps of: - illuminating a laser line from a source (1) on the surface of the job; - capturing the line image by a camera (2); - transferring the image from camera (2) to a computer; - focusing the image on screen of the computer in a suitable format; - recording and storing the image line on computer before welding; - recording and storing the image line on computer after welding; - comparing and co-relating the originally stored line image with the final line image and - a difference of the dimension in y-axis quantifies the distortion on the spot of the surface of welded material. Accordingly there is proposed a device, which will be able to measure the distortion at a particular location during welding from a far-away place. The device consists of a laser light line source (1), a camera (2), a computer (3) and a reference plate (5). The laser light source emits a line which allows to fall on the surface on the job where the distortion is to be measured. A highly sensitive camera acquires the image at that location on the job where the laser light disposed, an angle of less than 30 degree with reference to the surface of the job. The image consists of the laser line which has a shape according to the profile of the job surface. The image of the laser line appears a straight when the job is in a single plane without distortion. If there is a distortion on the job, the line changes it shape. By finding the difference between the two lines, the distortion can be calculated. Before starting the weld, the initial image should be collected and stored. It should be compared with the new acquired image and the distortion can be calculated from the difference in the line of projected image at that location.

Full Text

FIELD OF INVENTION
The invention generally relates to a device to measure the distortion produced during welding using computer vision.
BACKGROUND OF THE INVENTION
In arc welding process, a high concentration of heat is generated in the area where welding takes place and due to this heat effect, a change in shape of welded material takes place and is called distortion. This distortion, if exceeds the limit, makes the job unsuitable for the application. Hence distortion is a phenomenon which shall be controlled as much as possible. To control the distortion, it requires to be measured. If the distortion is monitored during welding, the weld sequence can be altered in order to minimize distortion. If the distortion is measured after welding, in that case, the job will be suitably corrected based on the measurement of distortion. Hence the invention has the objective of measuring the distortion at a particular location at different times when the welding is in progress or after completion of weld.

The Conventional way of measurement involves either mechanical or electrical based methods. In mechanical measurement method, standard measurement instruments such a vernier calipers, height gages and dial calipers are employed. If the component is large, special mechanical arrangements are made which included one of the above instruments. In the electrical measurement methods, strain gages or linear variable differential transformers (LVDTs) are employed. In the first method, a strain gage is bonded to the component and the strain is read through a data recording device. This is very accurate but measures distortion only in a small zone. In LVDTs, the measurement: is local and covers only a small area. In both cases of electrical measurement, contact with the product is essential and there is a limitation on the temperature of the job at which measurement is possible.
A prior Patent US 316504 which discloses an invention wherein the marking of wafer is identified and features from it are analyzed and taken into consideration. This involves acquisition of the image of the wafer and analysis of the features in only one plane and the proposed invention uses a laser line which produces information on the height direction.
Another prior Patent EP 1986046A1 describes a method of finding the focus of the image and adjusting the camera to obtain the focus automatically. The object of this patent is to set the correct focus by extracting features of the image and adjusting

the same. However, in the present invention is for the measurement of distortion and not adjusting the focus of camera.
A further prior Patent WO2008153721A1 describes a method of extracting the feature of a three dimensional object. In this method, multiple cameras are employed for obtaining the three different images and analyzing them and extracting the features in the image. However, in the present invention, a laser source is employed for finding the three dimensional features.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to propose a device which can measure distortion during welding.
Another object of the present invention is to propose a device which measures the distortion after welding.
A further object of the present invention is to propose a device which measures the distortion in the presence of the high temperature in the region where welding took place.

A still further object of the present invention is to propose a device which develops a non contact method of measuring the distortion.
Yet further object of the present invention is to propose a device which measures the distortion from a remote location.
Yet another object of the present invention is to propose a device which measures the distortion in a hazardous environment.
SUMMARY OF THE INVENTION
Accordingly there is proposed a device, which will be able to measure the distortion at a particular location during welding from a far-away place. The device consists of a laser light line source (1), a camera (2), a computer (3) and a reference plate (5). The laser light source emits a line which allows to fall on the surface on the job where the distortion is to be measured. A highly sensitive camera acquires the image at that location on the job where the laser light disposed, an angle of less than 30 degree with reference to the surface of the job. The image consists of the laser line which has a shape according to the profile of the job surface. The image of the laser line appears a straight when the job is in a single plane without distortion. If there is a distortion on the job, the line changes it shape. By finding the difference between the two lines, the distortion can be calculated. Before starting the weld, the

initial image should be collected and stored. It should be compared with the new acquired image and the distortion can be calculated from the difference in the line of projected image at that location.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig.1 - shows an embodiment of the device according to the invention Fig.2 - shows the image of profile of the laser line when incident on a plane
surface Fig.3 - shows the profile of the laser line when incident on a curved reference
plate or job Fig.4 - shows the profile of the laser line when incident on a curved or distorted
surface Fig.5 - shows reference plate
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
The device comprises of four components,
a) a laser line source (1) is illuminating the location at a given area on the job which will project a line on the surface.

b) a camera (2) which is kept at an angle less than 30 degree to acquire the line
image formed on the job at a specified location and image is transferred to
the computer in a suitable format and projected on monitor.
c) a computer (3) processes the image and compares the original line image
recorded before welding at the same spot and gives the difference of the
dimension in the y-axis which quantifies the distortion at the spot.
d) a portable reference plate (5) is engaged for setting the reference image
when the absolute value of the profile is required.
Principle of equipment operation
The line source produces a laser light which is a straight line. When this line is projected on a plane surface, and when this line is captured by a camera at an angle, then the image captured by the camera is a straight line (Fig.2). If the laser line is projected on a bent surface and when this line is captured at the same angle by a camera, then the image captured by the camera on the laser line will be bent line (Fig.4). The height of the bend can be correlated by the change in the straightness
a) When the level of distortion is measured with reference to the original
product profile ,i.e., when the amount of distortion is required to be
analyzed then the original profile of the product is used as the reference:
The laser line source projects a straight line on the job surface. The camera is
focused to the spot and the image is acquired by the camera, is further projected to

computer. This forms the reference image (Fig.3). The welding is undertaken and the distortion of the weld is required to be measured, then the image of the laser line on the job is collected and the co-ordinates are measured by computer software. The final distortion is measured by correlating the difference between the reference and measured co-ordinates of the line. The measurement is taken periodically and the trend in the distortion estimated.
b) When the absolute amount of distortion is to be measured with reference to
a fixed plane:
The laser line source projects a straight line on the plane reference (5). The welding is undertaken and the distortion of the weld is required to be measured, the image of the laser line on the job is collected and the co-ordinates are measured by computer software. The final distortion is measured by the difference between the reference and measured co-ordinates of the line. The measurement is taken periodically and the trend in the distortion estimated.
The final distortion of a product can be measured with reference to the original shape of the product or a fixed reference and can be used for correction.

WE CLAIM
1. A device for measurement of distortion during welding comprises:
- a laser line source (1) is illuminating the location on the surface of job (4);
- a camera (2) disposed at less than 30° angle with reference to the surface of
the job to capture the line image formed on the job at a specific location and
transferring the image to a computer in a suitable format;
- a computer processes the image and focus on the monitor; and
- a portable reference plate (5) is engaged for setting the reference image
Characterised in that the said images are compared with original line image
recorded before welding and images obtained after welding at the same spot
and produces a difference of dimension in the y-axis which quantifies the
distortion at that spot.
2. The process of measuring the distortion by the device comprises the steps of:
- illuminating a laser line from a source (1) on the surface of the job;
- capturing the line image by a camera (2);
- transferring the image from camera (2) to a computer;
- focusing the image on screen of the computer in a suitable format;
- recording and storing the image line on computer before welding;
- recording and storing the image line on computer after welding;

- comparing and co-relating the originally stored line image with the final line
image and
- a difference of the dimension in y-axis quantifies the distortion on the spot of
the surface of welded material.

Accordingly there is proposed a device, which will be able to measure the distortion at a particular location during welding from a far-away place. The device consists of a laser light line source (1), a camera (2), a computer (3) and a reference plate (5). The laser light source emits a line which allows to fall on the surface on the job where the distortion is to be measured. A highly sensitive camera acquires the image at that location on the job where the laser light disposed, an angle of less than 30 degree with reference to the surface of the job. The image consists of the laser line which has a shape according to the profile of the job surface. The image of the laser line appears a straight when the job is in a single plane without distortion. If there is a distortion on the job, the line changes it shape. By finding the difference between the two lines, the distortion can be calculated. Before starting the weld, the initial image should be collected and stored. It should be compared with the new acquired image and the distortion can be calculated from the difference in the line of projected image at that location.

Documents:

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Patent Number

279353

Indian Patent Application Number

310/KOL/2009

PG Journal Number

03/2017

Publication Date

20-Jan-2017

Grant Date

18-Jan-2017

Date of Filing

18-Feb-2009

Name of Patentee

BHARAT HEAVY ELECTRICALS LIMITED

Applicant Address

REGIONALOPERATIONS DIVISION (ROD), PLOT NO: 9/1, DJ BLOCK 3RD FLOOR, KARUNAMOYEE, SALT LAKE CITY, KOLKATA-700 091, HAVING ITS REGISTERED OFFICE AT BHEL HOUSE, SIRI FORT, NEW DELHI-110049

Inventors:

#	Inventor's Name	Inventor's Address
1	SETHURAMA SRINIVASA ANANTHAN	WELDING RESEARCH INSTITUTE, BHEL, TIRUCHIRAPPALLI 620 014
2	SRINIVASAN SURESH	WELDING RESEARCH INSTITUTE, BHEL, TIRUCHIRAPPALLI 620 014
3	NARASIMHAN RAJU	WELDING RESEARCH INSTITUTE, BHEL, TIRUCHIRAPPALLI 620 014
4	NAGAMUTHU DHANASEKARAN	WELDING RESEARCH INSTITUTE, BHEL, TIRUCHIRAPPALLI 620 014

PCT International Classification Number

B23K28/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA