Title of Invention

AN AUTOMATED DEVICE FOR OPTIMISED MEASUREMENT OF MOVING HOT SLAB LENGTH IN A CASTER ROLL MILL .

Abstract

This invention relates to an automated device for optimised measurement of moving hot slab length in a Caster roll mill to be cut in specified length accurately comprising of a pair of linear progressive area scan CCD Cameras (6) installed at a fixed distance from one another in the control pulpit of the caster line to view the hot slab (4), rolled on the caster table (3) and transmitting the images so formed of the slab to an image processing system integrated with the said cameras, the image processing system comprises of a high-end PC (7) with high resolution color grahics monitor (8), high speed frame grabber (2), DSP-based image processing cards and an image processing software (1), wherein the captured images by the cameras are sent to a frame grabber to be processed through an image processing card (10), operated and controlled by the image processing software(1) through the high end PC to save records and generate report (9) and display the accurate length of the hot slab to be cut by a gas flame.

Full Text

- 2 - Held of Invention The present invention relates to a hot slab length measurement device using image processing system through CCD Cameras. More specifically the invention relates to determination of hot length, hence the cold length after carrying out correction for the co-efficient of expansion of the slab after the slab cutter, using the charged coupled device (CCD) Cameras in the control room of the caster line along the length of the continuous caster table. Background of the Invention In tiie existing art the accurate measurement of the length of slabs, during processing of this material has presented many problems to the manufacturer. One conventional technique for measuring the slab length involves the positioning of a CCD (Charged Coupled Device) Camera immediately above the slab. The problem with a single camera device is that it is constrained to relatively small slab lengths. For longer slabs, the field of view is restricted and cannot accommodate the complete length of the slab. In order to obtain tiie complete length in the field of view, it would be necessary to move the camera to an unrealistic distance, thereby losing fidelity in the measurement. - 3 - Another disadvantage of the existing system is that when a slab is rolled on the caster table in a conventional system, the slab is sliced at the preset length that is fed to gas cutter. The slab is then labeled and piled up in the slab yard for further dispensation. The computation of the preset length depends on the roller movement; hence consistency of the preset length is not reliable due to slippage etc. The present invention is aimed to solve the difficulties of the existing art by developing an automated device for optimization and control of slab length for the Slab Caster Mill specifically for LD Slab Caster Mill for cutting the slab as accurate to the requirements as possible. Another objective of the present invention is to provide two CCD (Charged Coupled Device) Cameras being separated by an accurately known distance, each camera monitoring a specified length portion over an end of material and being focused upon the surface upon which the slab is moving. A further objective of the invention is to provide two camera remaining always in a monitoring mode of the caster table and the cameras are synchronised to capture the head and tail ends of the slab simultaneously as soon as the slab enters into an early specified region of interest. A still further object of the present invention is to propose an automatic decision making system based on a computer in cutting of a slab while dispensing with the inaccurate and rigid conventional system. - 4 - Yet another object of the present invention is to propose a closed circuit area-scan CCD camera to view the slab rolled on the caster table and sending out the images to be processed by a Image processing card based system to determine the hot length of the slab, completely lying in the view of 2camera system on the caster table. Yet a further objective of the system is to determine the length of the cut stab and provide feedback to level#2 (computer network which monitors and controls the process parameters of the mill regarding the actual cut made). Level#2 can further use this feedback to tweak the cut parameters for future references. Description of the Invention The device operates with a computer assisted visual decision system, using efficient Image Processing techniques. Two high-resolution area-scan CCD cameras capture the Head and Tail ends and behave like intelligent eyes of the system. The captured images are sent to the computer in the central control room for further processing. The processing is done on a DSP (Digital Signal Processing) based high speed Image Processing Hardware and by supporting software. The software determines from the image, the profile of the Head end and Tail ends and calculates the slab length. The lengths calculated are then sent to Level#2 (Logistics) for further analysis. The device integrated with the Image processing system performs with two main citeria a) Camera Calibration and b) Image Capturing And Processing. - 5 - Measuring of the hot length of a moving slab is carried on by imaging a plane of the slab at two positions displaced longitudinally about a datum producing signals indicative of the angle subtended by the slab at the image positions and representative of the image lengths apparent at those positions. The signals produced at the image positions are then combined to provide their product and difference components and true slab length is calculated from the said components generated by the signals. Intrinsic parameters of the camera are focal length, horizontal and vertical spatial resolution, CCD place skew and image center. Extrinsic parameters of the camera are rotation and translation of camera frame of reference with respect to world frame of reference. The camera is calibrated geometrically through the process of estimating the intrinsic and extrinsic parameters of the camera. Through the calibrated camera the image features are optimized by minimizing the discrepancies between the observed image features and their theoretical propositions with respect to camera's intrinsic and extrinsic parameters. In the instrumentation laboratory of Automation Division, image of a calibration object was observed by the camera and the images of the known points on the calibration object were found manually on the picture. The Image Processing System consists of the following: 1. Two High-resolution area-scan cameras with environmental enclosure installed at a fixed distance from one another in the control pulpit of the caster line. - 6 - 2. High-speed frame grabber and Image processing card (DSP Based) for real-time processing. 3. High-end Industrial PC. 4. Sophisticated software, coded in Microsoft Visual C++ ver.6.0. using specific Image processing routines of MVTOOLS ver.6.0 and ITEX routines for card interface. 5. To reduce glare and avoid noise in the image, the camera iens has been coupled with polarizing and Infra-Red(IR) filter. Further calibration task of the camera are decomposed into:- Computation of (he perspective projection matrix W Estimation of intrinsic and extrinsic parameters from the projection matrix W. Intrinsic parameter the images of the known world points in the picture give rise to set of linear equation in unknown camera parameters. The matrix equivalent representation can be written as per Forsyth and Ponce's equation for a given value of I - 7 - - 8 - c R Rotation of the Camera frame of w refernce with respect to World frame of Reference WP Coordinate in World reference frame c Ow Camera frame origin with respect to World frame origin. A matrix with one row (column) as shown in the equation is viewed as a vector and similarly a vector is viewed as a matrix with only one row. According to the invention there is provided an automated device for optimised measurement of moving hot slab length in a Caster roll mill to be cut in specified length accurately comprising of a pair of linear progressive area scan CCD Cameras installed at a fixed distance from one another in the control pulpit of the caster line to view the hot siab, rolled on the caster table and transmitting the images so formed of the slab to an image processing system integrated with the said cameras, the image processing system comprises of a high-end PC with high resolution color grahics monitor, high speed frame grabber, DSP-based image processing cards and an image processing software, wherein the captured images by the cameras are sent to a frame grabber to be processed through an image processing card, operated and controlled by the image processing software through the high end PC to save records and generate report and display the accurate length of the hot slab to be cut by a gas flame. Detailed Description of the Invention The invention will be better understood by description with reference to the accompanying drawings in which - 9 - Figure 1 represents a complete system diagram of the slab length measurement Device Figure 2 represents the progress of the slab and the position of the cameras. Figure 3 represents a flow chart to describe the strategy used in finding the slab length. And Figure 4 represents a schematic diagram of the slab length measurement Device through CCD (charged coupled device) Cameras. In figure 1 on a Caster table (3) hot slab (4) is moving. Above the moving slab two environmental protecting closed circuit area CCD Cameras (6) are arranged at two positions being separated by an accurately known distance. The cameras are focused upon a plane of the slab at two positions displaced longitudinally about a datum. The CCD cameras produce an image area (5) when the slab subtends an angle at the image positions. Imaged plane of the slab at two positions produce signals indicative of the subtended angle at the image positions and represent the image length at these positions. The images are processed by a MV Tools image processing Library (10). The captured images in CCD cameras are sent to a PC Vision (2) frame grabber and image processing card for processing of the said captured images through image processing hardware interface such as I TEX Interface Library (11) and supporting software (1) such as Visual C++ (Vc ++) Software development for this purpose. The host processor (7) save records of image processing and generates report and save (9) and display (8) displays the accurate length of hot slab to be cut by gas flame simulated through the in home built hardwares (10 & 11) and software (1). ¦ 10 - Figure 2 schematically explain how the 2 camera system measure the slab length and how the CCD cameras are positioned being separated by an accurately known distance. Each camera monitors a specified length portion over an end of the material. The cameras are focused on the surface upon which the hot slab is moving. The cameras are synchronised to capture the head and tail ends of the slab simultaneously as soon as the slab enters into an early specified region of interest. In the synchronised images where the head and tail offsets of the slab are added to the offset between the two cameras to compute accurate length of the slab. Figure 3 clearly shows in a self explanatory mode the strategy used to measure the length of the moving slab to be cut in accurate length through two synchronised cameras by image capturing and processing through hardwares and softwares as described herein before via calibrated camera. Figure 4 shows a schematic diagram of the slab measurement device in which 12 volt DC Input via CCD Cameras from 230 Volt AC supply is provided through video amplifier to the image processing system by PC vision image Processing Card hardware and PCI 1711 Advantech I/O Card (Analog/digital input/output card), both being connected to a port shown by dotted lines. The PCI 1711 hardware activates gas cutter by securing digital output signals (relay) of digital images of the correct length of the hot slab and corrected via video splitter of the digital images through the same Advantech I/O Card which are displayed in the PC VGA Monitor. The correct length of the hot slab is cut by the isolator on providing admitted output digital signal by the Advantech I/O Card. The whole operation is operated in a control room by an operator through a PC on display of the image datas. - 11 - The invention is herein described and illustrated should not be read in a restrictive manner as various adaptations, modifications and changes are possible as encampused within the scope of the appended claims. - 12 -WE CLAIM 1. An automated device for optimised measurement of moving hot slab length in a Caster roll mill to be cut in specified length accurately comprising of a pair of linear progressive area scan CCD Cameras (6) installed at a fixed distance from one another in the control pulpit of the caster line to view the hot slab (4), rolled on the caster table (3) and transmitting the images so formed of the slab to an image processing system integrated with the said cameras, the image processing system comprises of a high-end PC (7) with high resolution color grahics monitor (8), high speed frame grabber (2), DSP-based image processing cards and an image processing software (1), wherein the captured images by the cameras are sent to a frame grabber to be processed through an image processing card (10), operated and controlled by the image processing software(l) through the high end PC to save records and generate report (9) and display the accurate length of the hot slab to be cut by a gas flame. 2. An automated device as claimed in claim 1 wherein the captured images are processed through a HEX Interface Library (11) and sent to the frame grabber (2) for further processing. 3. An automated device as claimed in claim 1 wherein the cameras and the lenses are encapsulated inside a protective jacket to secure the cameras from the harsh environmental plant conditions and mounted on a rigid structure inside the control room. - 13 - 4. An automated device as claimed in claim 1 wherein the two cameras are synchronised to generate two separate synchronised images where the head and tail offsets of the slab are added to the offset between the two cameras to compute accurate length of the slab. 5. An automated device as claimed in the preceeding claims wherein a plane of the moving hot slab is imaged at two positions to produce signals indicative of the angle subtended by the slab at the image positions and representative of the image lengths apparent at those positions, the signals so generated being then combined to provide their product and difference components and true slab length is computed from the said components generated by the digital image signals. 6. An automated device as claimed in the preceeding claims wherein the cameras are calibrated geometrically through the process of estimating the intrinsic and extrinsic parameters of the cameras, the image features through the calibrated cameras being optimized by minimizing the discrepancies between the observed image features and their theoretical propositions with respect to the cameras intrinsic and extrinsic parameters. 7. An automated device as claimed in claim 6 wherein the intrinsic parameters of the cameras are focal length, horizontal and vertical spatial resolution, CCD plane skew and image center and extrinsic properties are rotation and translation of camera frame of reference with respect to world frame of reference. - 14 - 8. An automated device as claimed in the preceeding claims wherein a PCI 1711 Advantech I/O card simulated with a D/I gas cutter activates the gas cutter by securing digital output signals (relay) of digital images of correct length of the hot slab and corrected via video splitter of the digital images through the said PCI 1711 card being displayed in a monitor and the corrected length of the hot slab being cut by an isolator on providing admitted output digital image signal by the said card. 9. * An automated device as claimed in claims 6 & 7 wherein the calibration task of camera are carried through two fold representations Computation of the perspective projection matrix Wand Estimation^ of intrinsic and extrinsic parameters from the projection matrix W, in which the images of the known world points in the picture give rise to set of linear equation in unknown camera parameters, the matrix equivalent representation being written as per Forsyth and Ponce's equation for a given value of I - 15 - and where extrinsic parameters are represented by c P Point's coordinate in Camera frame of reference c R Rotation of the Camera frame of w refernce with respect to World frame of Reference wp Coordinate in World reference frame c Ow Camera frame origin with respect to World frame origin. 10. An automated device for optimised measurement of moving hot slab length in a caster roll mill as herein described and illustrated.

Documents:

00875-kol-2006-correspondence-1.1.pdf

00875-kol-2006-form-9.pdf

0875-kol-2006 abstract.pdf

0875-kol-2006 claims.pdf

0875-kol-2006 correspondence(others).pdf

0875-kol-2006 description(complete).pdf

0875-kol-2006 drawings.pdf

0875-kol-2006 form1.pdf

0875-kol-2006 form2.pdf

0875-kol-2006 form3.pdf

0875-kol-2006 g.p.a.pdf

875-KOL-2006-(05-12-2011)-FORM-27.pdf

875-KOL-2006-ABSTRACT-1.1.pdf

875-KOL-2006-CANCELLED DOCUMENT.pdf

875-KOL-2006-CLAIMS-1.1.pdf

875-KOL-2006-DRAWINGS-1.1.pdf

875-kol-2006-granted-abstract.pdf

875-kol-2006-granted-claims.pdf

875-kol-2006-granted-correspondence.pdf

875-kol-2006-granted-description (complete).pdf

875-kol-2006-granted-drawings.pdf

875-kol-2006-granted-examination report.pdf

875-kol-2006-granted-form 1.pdf

875-kol-2006-granted-form 18.pdf

875-kol-2006-granted-form 2.pdf

875-kol-2006-granted-form 3.pdf

875-kol-2006-granted-gpa.pdf

875-kol-2006-granted-reply to examination report.pdf

875-kol-2006-granted-specification.pdf

875-KOL-2006-REPLY TO EXAMINATION REPORT.pdf

abstract-0875-kol-2006.jpg