TECHNICAL FIELD OF THE INVENTION
This invention relates generally to the field of hot rolling of steel in a hot strip mill.
More particularly, the present invention relates to an improved system for measurement
of strip width during hot rolling of steel in a hot strip mill and a method thereof.
BACKGROUND AND THE PRIOR ART
In a Hot Strip Mill, strips of different thickness and width are rolled from slab. The Hot
Strip Mill consists of roughing stands and finishing stands. The roughing stand may
include a combination of horizontal stand and a vertical stand. There may exist a delay
table, one coil box and a crop shear at the end of the delay table. It also includes
hydraulic down coilers. A schematic diagram of the mill is shown in Fig 1.
Camera based width measurement systems are widely used in the mill. The camera
based width measurement system consists of a high resolution digital camera and a
computer system. The digital camera takes photographs of the strip and sends the
picture to the computer system. The software in the computer system reads the image,
counts the pixels and calculates strip width. The software has different factors, out of
which Camera Exposure Gain (CEG), Offset and Scale can be adjusted manually to get
desired reading. There are a number of deficiencies associated with said prior art due to
which the strip with calculation may not be accurate.
With this existing system different types of error may exist, like there may be no output
display at all. There may be inaccurate display of calculated strip width as compared to
physically measured value from corresponding strip sample.
The present inventors have found that, said error exists because of either "very high
CEG" or "very low CEG". Further it was noticed that a definite pattern for different
thickness of the measured strip exists. This shows that the width measurement is also

dependent upon strip thickness. A statistical relationship between "thickness of strip"
and "CEG and Offset" has been developed with fixed scale.
Some of the prior arts associated with the present invention are as follows:
US4671674 relates to a process for the detection and recording of the weak points or
defects on hot semifinished iron and steel industry products, by application of the flame
of an oxygen-supplied blowtorch to the surface to be examined, displacing the
application point along the surface, picking up the image of the application point by
video camera, and transmitting the image to a remote location. An observer viewing this
screen can make a map of the surface examined, recording thereon the weak points or
defects detected both by their dimensions and by their type. This process finds
application in the hot treatment of the slabs, blooms, and steel rods, when the casting,
defect repair and rolling operations are to be carried out continuously.
US 6184924 provides method for the automatic detection of surface defects for
continuously cast products with continuous mechanical removal of the material, which
products are separated into part lengths while still in the hot state and are introduced
before the final rolling in a rolling train to a material removing machine , in particular to
a grinding machine, in which the material of the continuously cast product is removed
as a function of the defective areas determined by a defect localizing equipment more or
less intensively from the surface(s) to be machined, which method provides that the
surface defect is introduced by the defect localizing equipment as pictorial information
to a picture processing processor and read in by a computer, comprising an integrated
comparison and evaluation module and connected superposed to the machine control, in
which computer the transmitted digital pictorial information is compared in a sample
recognition process with stored pictures of typical surface defects and the results like
length, width and area of the defect are either directly processed and stored in a
coordinate-related set of defect area in accordance with a classification with regard to
the relevance of the surface defects, or, after the storing in a set of surface defect data
are classified in a subsequent evaluation process. The defect localizing equipment is

constructed as an inspection unit which has at least one camera and a lighting equipment
which are arranged on a transverse girder extending over the resting table and the
inspection unit is connected to a comparison and evaluation module and to a computer
having a coordinate-related set of defect data.
US7623226 provides optical method and device for detecting surface and structural
defects of a traveling hot product, such as flat metal products during hot rolling, is
disclosed. The optical method includes using images of the product from a camera and
formed for one part by light for which the wavelength is in the infrared region and for
another part by light for which the wavelength is in the visible spectrum. Detection of
the images is provided by several linear sensors, each of them being associated with the
detection of one image, each located in a different focal plane associated with each
wavelength range so as to obtain superposable images. The light forming a portion of
the images is sent onto the surface of the traveling product. However, the above
mentioned prior arts provide a method which calculates defects on strip(s) but it does
not calculate width of the strip.
US8295608 provides a device and method for detecting joint parts of a steel strip in an
endless hot rolling process. The device for detecting joint parts of a steel strip in an
endless hot rolling process includes an image signal collection block receiving image
signals, each having information on gray level pixels of a steel strip, from a charge
coupled device (CCD) camera; an edge line detection block receiving the image signals
from the image signal collection block to detect an edge line of the steel strip; a profile
calculation block receiving information on the detection of the edge line from the edge
line detection block to calculate the sum of gray levels up to an edge line of the steel
strip in a traverse direction of the steel strip when the edge line is detected by the edge
line detection block; a joint part judgment block receiving information on the sum of the
gray levels, which shows a current profile value, from the profile calculation block to
judge the edge line as a joint part when a ratio of a mean value of the current profile and
a mean value of the previous profile is less than a predetermined value; and an output
block receiving information on the judgment of the edge line as the joint part from the
joint part judgment block to output a joint part-detecting signal when the edge line is

judged to be a joint part. However, this invention provides a method which determines
joint parts on strips but it does not calculate width of the strip.
JP2009233724 provide a cooling control method for a hot-rolled metal strip in a hot
rolling mill, and a manufacturing method for the hot-rolled metal strip using the above
method. The cooling related equipments to control flow-rate of cooling water
comprises: a thermal image measurement step to measure surface temperature
distribution of the hot-rolled metal strip being transferred through the cooing related
equipments between a finishing mill and a coiler in the hot rolling mill as image data by
a near-infrared camera; a temperature estimation step to estimate the maximum and the
minimum surface temperature in a region based on the image data, when the region of
the hot-rolled metal strip in which the image data was measured reaches a point in the
downstream side further than the near-infrared camera position; a cooling water flow
changing step to change the cooling water flow in the cooling related equipments so that
both the maximum and the minimum temperatures estimated in the temperature
estimation step come into a permissible temperature range; and a cooling water flow
setting step to set the revised cooling water flow in the cooling related equipments.
However, this invention provides a cooling control method for a hot-rolled metal strip
which is entirely different from the present invention and it does not provide a camera
based system to calculate width of the strip.
CN101543844 discloses an online thickness measurement and control method for a
metal alloy sheet strip hot rolling mill, which comprises the following steps that: a laser-
camera method is used for thickness measurement and a thickness signal is input to a
thickness adjustment AGC system after being converted so as to realize the control over
the thickness precision of a hot rolled sheet strip; a laser source is projected onto a
rolled piece, laser points are focused on carrying rollers on roller table, and an optical
scanner is arranged on a part which takes central line of rollers, before or behind a
machine frame, on the roller table as a mirror image; a scanned data signal is input into
the thickness adjustment AGC system of a computer to measure the actual thickness of
the rolled piece; and a hydraulic system pushes a lower rolling work roll of the hot
rolling mill to perform closed-loop timely regulation of a position for pressing with

upper rolling work roll of the hot rolling mill to realize the precision control of the final
rolled thickness of the rolled piece, as well as labor and material conservation and labor
intensity reduction. However, this mentioned prior art provides a method which used
laser rays to measure strip thickness but it does not use optical-camera based system to
calculate width of the strip.
JP2008238271 provide a method of photographing overall width of a hot-rolled metal
band and a method of recording the photographed result of the overall width
photographed result by which quality assurance in view of delivery to customers is
properly performed. When performing temperature measurement by photographing a
material to be rolled by installing near infrared cameras with which the overall width of
the hot-rolled metal band can be photographed in at least one or more places of the inlet
side of a coiler in a hot rolling line, the middle of a run out table and the outlet side of a
finishing mill, it is stored that what is beforehand determined how the relationship
between the brightness measured with the near infrared camera and temperature
measuring with a spot thermometer about the same places of the same heat source is
changed when changing the temperature of the heat source to change when changing the
temperature of the heat source as a brightness-temperature transformation curve. The
brightness when photographing the material to be rolled by installing the near infrared
camera on the hot rolling line is transformed into temperature according to the
brightness-temperature transformation curve. However, this mentioned prior art used a
"near-infrared" camera for calculating the width of the strip and Infrared cameras as
widely used for temperature measurement. In this prior art there is no variable CEG
based correction and no provision of modification of width of strip as per thickness of
rolled products.
JP60038609 enable the measurement of the flat shape of a steel plate quickly with a
high resolution by partially photographing infrared radiation from a steel plate wile
under rolling with a plurality of 2-D cameras to be synthesized. Infrared rays of radiant
heat from a steel plate during the hot rolling process are photographed as heat infrared
image with cameras as 2-D camera to be fed to a control section as electrical signal and
signals from video processors in the control section are fed sequentially to an A/D

converter, a subslicer, a main slicer and an edge position detection circuit through a
selector whereby edge positions on scan lines are detected and stored into a memory;
Then, after the detection of edges for one picture and the storage of data thereof, a CPU
feeds the data of the memory 36 to an arithmetic unit, which converts the edge list of
individual fields of view into the reference coordinates of a synthetic screen to
synthesize individual fields of view for nine pictures into a synthetic field of view.
However, this mentioned prior art provides a method using a infrared camera to
measure shape of steel. It does not use optical-camera based system to measure width of
the strip.
Therefore, the present invention provides an improved system for measurement of strip
width during hot rolling of steel in a hot strip mill and a method thereof. The present
invention provides a method for modification of width of strip as per thickness of rolled
hot coil.
OBJECTS OF THE INVENTION
A basic object of the present invention is to overcome the disadvantages/drawbacks of
the known art.
Another object of the present invention is to provide an improved system for
measurement of strip width during hot rolling of steel in a hot strip mill.
Another object of the present invention is to provide a method for measurement of strip
width during hot rolling of steel in a hot strip mill.
These and other advantages of the present invention will become readily apparent from
the following detailed description read in conjunction with the accompanying drawings.
SUMMARY OF THE INVENTION
The following presents a simplified summary of the invention in order to provide a
basic understanding of some aspects of the invention. This summary is not an extensive

overview of the present invention. It is not intended to identify the key/critical elements
of the invention or to delineate the scope of the invention. Its sole purpose is to present
some concept of the invention in a simplified form as a prelude to a more detailed
description of the invention presented later.
There is provided an improved system for measurement of strip width during hot rolling
of steel in a hot strip mill and a method thereof.
According to one aspect of the present invention there is provides a system for
measuring the strip width of a hot rolled coil(s) during hot rolling. The system
comprises, an image capturing device for capturing the image of said hot rolled coil(s)
during hot rolling; a programmable logic controller for generating strip thickness analog
signal ; a hardware instrumentation panel comprises a digital indicating controller for
providing an output (s) (A, B, C) corresponding to thickness of the strip of hot rolled
coil; a data processing device comprises an image processing module for calculating the
strip width of the hot rolled coil; a output display device for displaying the correct value
of the strip width of the hot rolled coil. The image processing module in the data
processing device calculate width of the strip of the hot rolled coil by selecting the
correct value of camera exposure gain and offset factor based on the thickness of the
strip of the hot rolled coil.
In another aspect of the present invention, there is provided a process for measuring the
strip width of a hot rolled coil(s) during hot rolling. The process comprises following
steps
a. capturing image of said hot rolled coil during hot rolling by an image
capturing device,
b. calculating the width of said hot rolled coil by data received from step (a)
using a data processing device which comprises an image processing
module for counting the pixels and converting it to width of which,
c. generating a strip thickness analog signal by using a programmable logic
controller,

d. converting said strip thickness analog signal received from step (d) into
digital output signal corresponding to the thickness of the strip by using a
hardware instrumentation panel,
e. processing said data received from step (d) by selecting the correct value
of camera exposure gain and offset factor using an image processing
module, said image processing module comprises in said data
processing device, wherein said processing comprises step,
i. interpreting the digital signal data input received from said digital
indicating controller in said hardware instrumentation panel,
ii. converting said digital data received from step (i) to a data
corresponding to the thickness of said hot strip,
iii. interpreting the correct values of camera exposure gain and
offset factor corresponding to data received from step (ii) using a
thickness lookup table,
iv. calculating the width of the strip corresponding to the thickness
of said strip of said hot rolled coil
f. displaying the correct value of the width of said hot rolled coil on a
display device.
Other aspects, advantages, and salient features of the invention will become apparent to
those skilled in the art from the following detailed description, which, taken in
conjunction with the annexed drawings, discloses exemplary embodiments of the
invention.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The following drawings are illustrative of particular examples for enabling methods of
the present invention, are descriptive of some of the methods, and are not intended to
limit the scope of the invention. The drawings are not to scale (unless so stated) and are

intended for use in conjunction with the explanations in the following detailed
description.
Reference is first invited to Figure 1 where the layout of hot strip mill is shown.
Figure 2 illustrates a conventional camera based width measurement system.
Figure 3 illustrates a schematic diagram of the implementation of the present invention.
Figure 4 illustrates a relationship between CEG and coil thickness.
Figure 5 illustrates a hardware panel design.
Persons skilled in the art will appreciate that elements in the figures are illustrated for
simplicity and clarity and may have not been drawn to scale. For example, the
dimensions of some of the elements in the figure may be exaggerated relative to other
elements to help to improve understanding of various exemplary embodiments of the
present disclosure.
Throughout the drawings, it should be noted that like reference numbers are used to
depict the same or similar elements, features, and structures.
DETAILED DESCRIPTION OF THE INVENTION
The following description with reference to the accompanying drawings is provided to
assist in a comprehensive understanding of exemplary embodiments of the invention as
defined by the claims and their equivalents. It includes various specific details to assist
in that understanding but these are to be regarded as merely exemplary. Accordingly,
those of ordinary skill in the art will recognize that various changes and modifications
of the embodiments described herein can be made without departing from the scope and
spirit of the invention. In addition, descriptions of well-known functions and
constructions are omitted for clarity and conciseness.
The terms and words used in the following description and claims are not limited to the
bibliographical meanings, but, are merely used by the inventor to enable a clear and

consistent understanding of the invention. Accordingly, it should be apparent to those
skilled in the art that the following description of exemplary embodiments of the present
invention are provided for illustration purpose only and not for the purpose of limiting
the invention as defined by the appended claims and their equivalents.
It is to be understood that the singular forms "a," "an," and "the" include plural
referents unless the context clearly dictates otherwise.
By the term "substantially" it is meant that the recited characteristic, parameter, or value
need not be achieved exactly, but that deviations or variations, including for example,
tolerances, measurement error, measurement accuracy limitations and other factors
known to those of skill in the art, may occur in amounts that do not preclude the effect
the characteristic was intended to provide.
Accordingly, the present invention provides a hardware instrumentation panel that gets
strip thickness signal from existing mill programmable logic controller (PLC) interface
during rolling. The improved system has a coil thickness based camera exposure gain
(CEG) and offset calculation. Modified software has been developed to make
corrections based on variable CEG and offset rather than fixed CEG and offset. A
hardware system has been designed which takes input thickness data from PLC system
and changes the CEG and offset in the software automatically. The output of the
software is width of hot rolled coils.
The present invention provides a cost effective and highly reliable system of width
measurement using ordinary optical camera. The hardware of PLC and Digital
Indicating Controller has been developed to improve the accuracy. No such system is
available anywhere which makes width measurement using optical camera (Infrared
camera which is used at many places for width measurement) with automatic tunning of
CEG and Offset as per strip thickness. Normal image processing software's with optical
camera cannot measure width accurately and therefore is not used anywhere. But, the
method described here has made it possible to measure width with high accuracy using
normal optical camera.

Present invention provides a camera as measuring device. The improved system has a
coil thickness based Camera Exposure Gain (CEG) and offset calculation. A modified
software has been developed to make corrections based on variable CEG and Offset
rather than fixed CEG and Offset. A hardware system has been designed which takes
input thickness data from PLC system and changes the CEG and offset in the software
automatically. The output of the software is width of hot rolled coils.
A hardware instrumentation panel that gets strip thickness signal from existing mill
Programmable Logic Controller (PLC) interface during rolling has been provided as
shown in Figure 3. The instrumentation panel contains a Digital indicating controller.
The Analog input signal of strip thickness from Siemens PLC was taken as an input to
this controller. The Controller has been programmed to make three digital output (0 or
1) as per following table

Based on the output signal the CEG are selected in the software using CEG Vs.
thickness graph as given in the earlier figure (Fig.4). It provides a method of calculation
of CEG and Offset based on strip thickness has been developed. A modified software
has been developed to make corrections based on variable CEG and Offset rather than
fixed CEG and Offset. The Method step used in image processing module,
Step-1: Read the three digital signal data input from Digital Indicating Controller
Step-2: Convert the data into thickness

Step-3: Read CEG and Offset from a lookup table corresponding to the thickness
Step-4: Send the CEG and Offset values to a software module which counts number of
pixels and converts to a width value
Step-5: Send the display value to Display Unit
The cases of non-display of output in some cases have also been avoided. The system is
low cost compared to other width measurement systems. This is useful in steel industry
and other industry like Aluminum industry.
Although the embodiments herein are described with various specific embodiments, it
will be obvious for a person skilled in the art to practice the embodiments herein with
modifications. However, all such modifications are deemed to be within the scope of the
invention.
It is also to be understood that the description is intended to cover all of the generic and
specific features of the embodiments described herein and all the statements of the
scope of the embodiments which as a matter of language might be said to fall there
between.

WE CLAIM:
1. A system for measuring the strip width of a hot rolled coil(s) during hot rolling,
said system comprising:
an image capturing device for capturing the image of the hot rolled
coil(s) during hot rolling;
a programmable logic controller for generating strip thickness analog
signal;
a hardware instrumentation panel comprises a digital indicating
controller for providing an output (s) (A, B, C) corresponding to
thickness of said strip of hot rolled coil;
a data processing device comprises an image processing module for
calculating the strip width of said hot rolled coil;
a output display device for displaying the correct value of the strip width
of said hot rolled coil;
wherein said image processing module in said data processing device
calculate width of the strip of the hot rolled coil by selecting the correct
value of camera exposure gain and offset factor based on the thickness of
the strip of the hot rolled coil.
2. The system as claimed in claim 1, wherein said hardware instrumentation panel
change the constant values of camera exposure gain and offset factor into strip
thickness dependent variables.
3. The system as claimed in claim 1, wherein said image capturing device is an
optical camera.
4. The system as claimed in claim 1, wherein said data processing device is a
computer system.
5. A process for measuring the strip width of a hot rolled coil(s) during hot rolling,
said process comprising steps of:
g. capturing image of said hot rolled coil during hot rolling by an image
capturing device,

h. calculating the width of said hot rolled coil by data received from step (a)
using a data processing device which comprises an image processing
module for counting the pixels and converting it to width of which,
i. generating a strip thickness analog signal by using a programmable logic
controller,
j. converting said strip thickness analog signal received from step (d) into
digital output signal corresponding to the thickness of the strip by using a
hardware instrumentation panel,
k. processing said data received from step (d) by selecting the correct value
of camera exposure gain and offset factor using an image processing
module, said image processing module comprises in said data
processing device, wherein said processing comprises step,
v. interpreting the digital signal data input received from said digital
indicating controller in said hardware instrumentation panel,
vi. converting said digital data received from step (i) to a data
corresponding to the thickness of said hot strip,
vii. interpreting the correct values of camera exposure gain and
offset factor corresponding to data received from step (ii) using a
thickness lookup table,
viii. calculating the width of the strip corresponding to the thickness
of said strip of said hot rolled coil
1. displaying the correct value of the width of said hot rolled coil on a
display device.
6. The process as claimed in claim 5, wherein said hardware instrumentation panel
comprises a digital indicating controller for providing digital output(s) (A, B, C).
7. The process as claimed in claim 5, wherein said hardware instrumentation panel
change the constant values of camera exposure gain and offset factor into strip
thickness dependent variables.
8. The process as claimed in claim 5, wherein said image capturing device is an
optical camera.

9. The process as claimed in claim 5, wherein said data processing device is a
computer system.

ABSTRACT

The present invention relates to an improved system for measurement of strip width
during hot rolling of steel in a hot strip mill and a method thereof. The system for
measurement of strip width during hot rolling of steel in a hot strip mill comprises, an
image capturing device for capturing the image of said hot rolled coil(s) during hot
rolling; a programmable logic controller for generating strip thickness analog signal; a
hardware instrumentation panel comprises a digital indicating controller for providing
an output (s) (A, B, C) corresponding to thickness of the strip of hot rolled coil; a data
processing device comprises an image processing module for calculating the strip width
of the hot rolled coil; a output display device for displaying the correct value of the strip
width of the hot rolled coil. The image processing module in the data processing device
calculate width of the strip of the hot rolled coil by selecting the correct value of camera
exposure gain and offset factor based on the thickness of the strip of the hot rolled coil.