Vision method and system for coating processes and systems

Abstract

A system and method are provided for determining properties of a metal strip in a coating process. A pattern is projected onto or reflected by the strip, and images of the pattern are captured simultaneously from at least two different angles using visual sensors. These images are analyzed to determine properties of the strip, such as position, orientation, movement, and / or deformation. The system may use reference points formed by intersections of the pattern with the strip edges or interior features to construct a three-dimensional representation of the strip. Deformations may be identified using deflectometry and magnification effects. The determined properties can be used to dynamically adjust coating process parameters, such as air knife position, roll position and alignment, and edge baffle location, to improve coating uniformity and reduce defects.

Description

[0001] VISION METHOD AND SYSTEM FOR COATING PROCESSES AND SYSTEMS

[0002] FIELD

[0003] [1] The present disclosure relates to continuous metal coating processes and systems, and determining properties of a metal strip in such metal coating processes and systems.

[0004] BACKGROUND

[0005] [2] Sheets of metal (also referred to herein as strips of metal or strips) may be coated with a material to provide the metal with certain desired physical properties. For example, sheets of steel may be coated with a protective zinc-based material in a process known as galvanization. The protective coating inhibits the sheet from oxidizing. Galvanized sheet metal is used for general applications and automotive applications, such as car doors and other exposed panels.

[0006] [3] Conventional metal sheet galvanization process lines draw long coils of sheets or strips of metal from an annealing furnace through a coating bath. Rollers and other equipment may help guide a sheet continuously through the bath.

[0007] [4] A coating bath typically consists of a molten zinc-based coating which provides the metal sheet with a protective coating that inhibits the sheet from oxidizing.

[0008] [5] It is important to precisely control the amount or thickness of zinc-based coating on the metal sheet. The zinc-based coating is expensive. It is also preferable to achieve a uniform thickness of the coating. It is also important to limit the surface defects / imperfections in the coating.

[0009] [6] In order to control the thickness of the coating on a metal sheet in a galvanization process, the sheet may pass between air knives after emerging from the coating bath. The air knives emit high pressure and high velocity gas directed at both sides of the metal sheet to remove the excess coating from the sheet and more evenly distribute the coating across the sheet. The molten coating metal that is stripped from the sheet is typically returned to the bath for re-use. Excessive coating, beyond the minimum requirements, increases material production costs with no functional benefits or way to recoup such costs in the market. Too little coating, or imperfections / defects in the coating, may result in the sheet not meeting certain industry specifications, and may require the product to be downgraded or even result in scrapped product. [7] The proximity of the air knives to the sheet and gas wiping pressures are the main parameters used to control the coating thickness. The metal sheet can, however, deform including buckle, warp, bow around the area of the air knives as the sheet continuously passes between the air knives. This can cause a varying gap between the air knife and the sheet along the width, resulting in variations in coating thickness, and potentially imperfections in the coating surface. Also, the closer the air knives are to the sheet, the greater the risk that sheet movement and / or deformation will result in the sheet hitting an air knife. This can block the air knife slot with coating material, potentially damage the air knife, introduce imperfections into the coating, and potentially require the shutdown of the entire galvanization line.

[0010] [8] In order to guide the sheet into, then out of, the bath, the sheet may be bent around a main roll within the bath. A main roll is often referred to as a sink roll. The main roll causes the sheet to change direction within the bath. This bending, however, can cause a deformation in the metal sheet where the internal stress can exceed the yield strength of the metal. The metal sheet becomes compressed on the side contacting the roll, and elongated on the opposite side. When the yield strength is exceeded, plastic deformation can result in an unwanted crossbow (transverse warp) or deviation from flatness in the sheet. Importantly, among other issues, a crossbow in the sheet may result in a non- uniform thickness of the molten zinc-based coating to be controlled through conventional air knife wiping methods employed on galvanizing lines.

[0011] [9] In order to more precisely guide the sheet through the coating process, and to identify and / or prevent imperfections in the sheet, it is desirable to determine properties of a portion of the sheet around the vicinity of the air knives. The properties include one or more of the position of the sheet, the orientation of the sheet, the motion or movement of the sheet, and the deformation of the sheet, all relative to the air knives or some other element(s) within the environment of the sheet. Deformation includes the shape of the sheet, and defects in / on the sheet. However, the environment around the air knives is close to the molten coating material and often involves high temperatures. This makes it difficult for conventional sensing electronics to be kept cool and clean.

[0012]

[0010] Conventional sensing electronics for this application, such as laser displacement and optic fiber sensors, often require complicated cooling hardware and frequent cleaning from dust and vapor deposit from the coating material. The reflectiveness, movement, and deformation of the measurement surface (i.e. the sheet) can also make laser technologies (such as laser displacement sensors) unreliable, as the reflected laser beam may not go back to the sensor’s receiver.

[0013] BRIEF DESCRIPTION OF THE DRAWINGS

[0014]

[0011] Figure 1 schematically depicts a continuous system for coating a metal sheet comprising a vision system according to an embodiment of the present disclosure.

[0015]

[0012] Figure 2 is an enlarged top view of the air knives area of Figure 1 showing a desired sheet and potential undesired bowed sheets passing through the air knives.

[0016]

[0013] Figure 3 is an enlarged view of an embodiment of the vision system of Figure 1 in isolation.

[0017]

[0014] Figure 4 shows an example feasibility setup for the disclosed vision system.

[0018]

[0015] Figure 5 shows the output of an edge positioning system and method when applied to edges of a strip using the disclosed vision method and system in accordance with an embodiment of the present disclosure.

[0019]

[0016] Figure 6 is an enlarged view of another embodiment of the vision system of Figure 1 in isolation.

[0020]

[0017] Figure 7 schematically depicts vertical reference examples on a reflective sheet in accordance with embodiments of the present disclosure.

[0021]

[0018] Figure 8 is a block diagram representation of a vision system in communication with a coating mass control system in an embodiment of the present disclosure.

[0022]

[0019] Figure 9 is a flow diagram illustrating a method for determining properties of a strip in a coating process, according to an embodiment of the present disclosure.

[0023] DETAILED DESCRIPTION

[0024]

[0020] Described herein is a vision system and method for determining the properties of a metal sheets (also referred to herein as strips) in a coating process. Also described herein is a system for and method for coating a sheet. As noted above, current laser displacement and optic fiber sensors often require complex cooling hardware and frequent cleaning from dust and vapor deposit from the coating material. In many implementations of the present disclosure, the strip being coated is a reflective or semi-reflective strip. In such cases, the reflectiveness of the metal strip can also make such laser technologies unreliable.

[0021] To alleviate such concerns, the present vision system and method places the more sensitive visual sensory equipment (such as cameras), far from the heat source where little to no cooling is required, and places the less sensitive equipment or electronics (such as lights) close to the measurement point near the strip. Light fixtures are generally often more easily cooled, and they tend to be more robust against heat and dirt. To perform the measurements, the present disclosure does not use direct reflection of laser beams for providing the sensing data. Rather, the properties of a reflected image formed in the measurement surface, i.e. the metal sheet, is considered, as opposed to the location of reflected laser beam in laser-based technologies. This allows for non-contact and remote installation of measurement apparatuses.

[0025]

[0022] One aspect of the present disclosure relates to a method for determining properties of a strip in a coating process, the method comprising: providing a pattern onto the strip; obtaining images of that pattern on the strip at the same time from at least two different angles; and determining the properties of the strip based on the images.

[0026]

[0023] In some implementations, the method further comprises identifying two sets of vertically-aligned reference points from the images, fitting a two-dimensional line to each of the sets of refence points, converting the two-dimensional lines into a three-dimensional representation of the strip based the multiple images, and determining the properties of the strip based on the three-dimensional representation of the strip.

[0027]

[0024] In some implementations, the three-dimensional representation of the strip comprises an orientation or location of the strip, or a magnification effect of the strip.

[0028]

[0025] In some implementations, converting the two-dimensional lines into the three- dimensional representation of the strip comprises triangulating three-dimensional lines from the two-dimensional lines based on epipolar geometry formed by the angles from which the images are obtained.

[0029]

[0026] In some implementations, the vertically-aligned reference points comprise endpoints defined by the intersection of the pattern with an edge of the strip.

[0030]

[0027] In some implementations, the vertically-aligned reference points comprises points defined by the pattern that are interior to the edges of the strip.

[0031]

[0028] In some implementations, the method further comprises the vertically-aligned reference points comprise breaks within the pattern or vertical lines.

[0029] In some implementations, providing the pattern comprises providing the pattern so as to extend to each of the edges of the strip at least two points; and wherein obtaining images comprises capturing at least a first image from a first angle of view and a second image from a second angle of view of the pattern on the strip; and further comprising identifying endpoints from the images defined by the intersection of the pattern with the edges of the strip, and determining the properties of the strip based on the endpoints.

[0032]

[0030] In some implementations, the pattern comprises two horizontal lines spaced vertically from one-another.

[0033]

[0031] In some implementations, the horizontal lines extend across the width of the strip.

[0034]

[0032] In some implementations, each of the horizonal lines is non-continuous in the same vertical locations to define at least two sets of vertically-aligned reference points that are interior to the edges of the strip.

[0035]

[0033] In some implementations, the pattern comprises one or more lines.

[0036]

[0034] In some implementations, the pattern comprises at least two lines.

[0037]

[0035] In some implementations, the strip is a reflective or semi-reflective strip.

[0038]

[0036] In some implementations, subsequent to identifying the endpoints from the images, the method further comprises determining locations of the edges of the strip based on the endpoints.

[0039]

[0037] In some implementations, the properties of the strip comprise one or more of position, orientation, movement, and deformations of or on the strip.

[0040]

[0038] In some implementations, the method further comprises illuminating the pattern source for the pattern to be reflected by the reflective or semi-reflective strip.

[0041]

[0039] In some implementations, the pattern source is a diffuse material.

[0042]

[0040] In some implementations, the pattern source is made of retro-reflective material.

[0043]

[0041] In some implementations, the pattern is provided onto the strip by projecting the pattern as a light pattern from the pattern source onto the strip.

[0044]

[0042] In some implementations, a property of the strip is a deformation of the strip, and wherein the deformation is determined using deflectometry.

[0043] In some implementations, the method further comprises providing a vertical references on the strip to provide the two sets of vertically-aligned reference points, and identifying a deformation in the strip as a property based on the magnification effect.

[0045]

[0044] In some implementations, computing the magnification effect comprises comparing a known width between the two sets of vertically aligned reference points with a width between the two sets of vertically aligned reference points from the images.

[0046]

[0045] In some implementations, the vertical reference is a reference gap in the pattern.

[0047]

[0046] In some implementations, the vertical reference is a vertical light or a vertical line pattern.

[0048]

[0047] In some implementations, each of the lines comprises a reference gap therein, and identifying a deformation in the strip comprises computing the magnification effect based on the reference gaps in the lines on the strip from the images.

[0049]

[0048] In some implementations, providing the reference gap comprises providing an interruption or occlusion in the lines.

[0050]

[0049] In some implementations, the method further comprises adjusting an aspect in the coating process in response to the properties of the strip.

[0051]

[0050] In some implementations, adjusting an aspect in the coating process comprises one or more of: adjusting air knives, adjusting a correction roller, adjusting blower air pressure, adjusting line tension, adjusting roll alignments, adjusting the tension leveler, and adjusting an air baffle.

[0052]

[0051] Another aspect of the present disclosure relates to a vision system for determining properties of a strip in a coating system, the vision system comprises: a pattern source for positioning proximate to the strip for providing a pattern onto the strip; two or more sensors for capturing images of the pattern on the strip at the same time from at least two different angles; a processor coupled to the two or more sensors, the processor having memory comprising instructions that, when executed by the processor, cause the processor to determine the properties of the strip in the coating system based on the images.

[0053]

[0052] In some implementations, the memory comprises instruction for causing the process to identify two sets of vertically-aligned reference points from the images, fit a two-dimensional line to each of the sets of reference points, convert the two-dimensional lines into a three-dimensional representation of the strip based on the multiple images, and determine the properties of the strip based on the three-dimensional representation of the strip.

[0054]

[0053] In some implementations, the three-dimensional representation of the strip comprises the orientation or location of the strip, or the magnification effect of the strip.

[0055]

[0054] In some implementations, converting the two-dimensional lines into the three- dimensional representation of the strip comprises triangulating three-dimensional lines from the two-dimensional lines based on epipolar geometry formed by the angles of the sensors.

[0056]

[0055] In some implementations, the vertically-aligned reference points comprise endpoints defined by the intersection of the pattern with an edge of the strip.

[0057]

[0056] In some implementations, the vertically-aligned reference points comprises points defined by the pattern that are interior to the edges of the strip.

[0058]

[0057] In some implementations, the pattern sources comprises a line source configured to reflect as the pattern across the width of the strip.

[0059]

[0058] In some implementations, the pattern source comprises two line sources configured to reflect across the width of the strip.

[0060]

[0059] In some implementations, the strip comprises a coating providing a reflective or semi-reflective surface.

[0061]

[0060] In some implementations, the vision further comprises a light source for illuminating the pattern source such that the pattern from the pattern source is reflected by the reflective or semi-reflective strip.

[0062]

[0061] In some implementations, the pattern source is made of retro-reflective material and the light source is positioned between the two or more sensors.

[0063]

[0062] In some implementations, the pattern source further comprises a light source to project the pattern as a light pattern onto the strip.

[0064]

[0063] In some implementations, the memory comprises further instructions that, when executed by the processor, cause the processor to determine a deformation of the strip using deflectometry.

[0065]

[0064] In some implementations, the pattern source comprises a vertical reference source for providing a vertical reference on the strip, and the memory comprises further instructions that, when executed by the processor, cause the processor to identify a deformation in the strip by computing a magnification effect based on the vertical reference on the strip from the images.

[0066]

[0065] In some implementations, the vertical reference source is a reference gap in the pattern.

[0067]

[0066] In some implementations, the vertical reference source is a vertical light source or a vertical line pattern source.

[0068]

[0067] In some implementations, the properties are locations of edges of the strip, and further comprising edge baffles configured to be actuated to track the edges of the strip based on the locations of the edges of the strip.

[0069]

[0068] In some implementations, the memory comprises instructions that, when executed by the process, causes the process to perform the method of any of the preceding method claims.

[0070]

[0069] Another aspect of the present disclosure relates to a system for coating a strip comprising a vision system in accordance with any one of the above noted implementations.

[0071]

[0070] Another aspect of the present disclosure relates to a strip coating system comprising: a bath of coating material; rolls for directing a strip through the bath; opposing air knives positioned on opposite sides of the strip downstream of the bath; and a vision system in accordance with any one of the preceding vision system claims.

[0072]

[0071] In some implementations, the strip coating system further comprises actuators for controlling the location of the air knives relative to the strip, and wherein the actuators are configured to be controlled based on the properties determined by the vision system.

[0073]

[0072] In some implementations, the strip coating system further comprises a roll contacting the strip, and wherein the location of the roll is configured to be controlled based on the properties determined by the vision system.

[0074]

[0073] Another aspect of the present disclosure relates to a process for coating a strip, comprising: providing a strip through a bath of coating materials; providing the strip between opposing air knives; providing high pressure air onto each side of the strip using the air knives; determining properties of the strip based on the method of any one of the preceding method claims; and varying the process based on the properties of the strip determined by the method.

[0075]

[0074] In some implementations, the varying the process comprises adjusting the location of the air knives, the location of one or more rolls, or the location of edge baffles.

[0076]

[0075] Figure 1 illustrates a schematic side view of a continuous metal coating arrangement with a coating mass control (CMC) system 100 comprising a vision system 10 according to embodiment of the present disclosure. The metal sheet 102 goes into a pot 104 that may be filled with a zinc alloy or another coating material. The metal sheet exits the pot, then on the other end the metal sheet goes through a few rollers 106 and then passes between air knives 108. The air knives help control the thickness of the zinc coating on the metal sheet 102 by blowing off excess zinc using air pressure.

[0077]

[0076] Figure 2 is a top view of the air knives 108 of Figure 1. The strip 102 that is passing through the air knives 108 may be undesirably deformed as shown. This may happen because of the deformation that occurs when it is forced to conform to rollers 106 inside the coating pot 104. Examples of deformations that regularly occurs in the strip is a “crossbow” and “skew”. This is not desirable since it causes uneven coating on the strip 102. This deformation of bending causes variation in distance from the knife’s edge, hence variation in air pressure and coating thickness. The CMC system 100 constantly moves the air knives 108 to help the air knives 108 follow the strip 102 as the strip 102 passes between the air knives 108 in a continuous process. That is also why it is important to know where the strip 102 is (e.g. location, orientation) relative to the air knives 108.

[0078]

[0077] Figure 3 illustrates an example embodiment of the present vision system 10. The vision system 10 may include two or more visual sensors 12, such as cameras, and a pattern source 14 (which may be or include a light fixture, not shown) that generates a line pattern 20 onto the metal strip 102. The two or more sensors 12 are positioned to capture the pattern 20 on the strip 102 from two or more (or at least two) different angles. The sensors 12 may be at different locations relative to the metal strip 102. A sensor 12 may be adapted to capture images of a pattern reflection or the light pattern 20 on the strip 102. The sensors 12 may be coordinated so each sensor 12 captures its own respective image of the pattern 20 on the strip 102 at the same time. In some applications, the two or more sensors 12 may capture at least a first image of the pattern reflection 20 on the strip 102 from a first location and a second image of the pattern reflection 20 on the strip 102 from a second location. In other applications, the two or more sensors 12 may capture a first image of the pattern reflection 20 on the strip 102 from a first angle of view and a second image of the pattern reflection 20 on the strip 102 from a second angle of view of the reflection.

[0079]

[0078] As used herein, the terms “strip,” “sheet,” and “metal sheet” refer interchangeably to the continuous length of metal material being processed and coated in the described system. These terms are used synonymously throughout the disclosure to reflect the same component of the coating process. Additionally, the term ‘pattern’ refers to any visual feature that can be projected onto or reflected by the strip surface and subsequently captured by the sensors. The pattern may be generated by a light-based source (e.g., LED grid, projected lines) or may be a physical marking (e.g., printed lines, stickers, etched features) applied to or positioned near the strip. Similarly, the ‘pattern source’ may include active light-emitting devices, passive reflective materials, or physical structures that define the visual pattern. These variations of the pattern / pattern source allow the system to be configured to different strip reflectivity levels and environmental conditions. The pattern may be provided onto the strip in various ways depending on the configuration of the pattern source. In some implementations, the pattern is projected as a light pattern from an active source, such as an LED grid or structured light projector, directly onto the surface of the strip. In other implementations, the pattern may be reflected onto the strip from a passive source, such as a printed or etched image, a diffuse material, or a retro-reflective surface illuminated by a separate light fixture. The pattern may also be physically applied to or positioned near the strip using markings, stickers, or painted lines.

[0080]

[0079] Once the pattern is provided onto the strip, images of the pattern are obtained using two or more visual sensors, such as cameras, positioned at different angles relative to the strip. These sensors are configured to capture images of the pattern on the strip simultaneously, allowing for multi-angle analysis. The sensors may be placed remotely from the strip to avoid heat and contamination, while still maintaining a clear line of sight to the pattern. The captured images include reflections or projections of the pattern on the strip surface, which are then processed to extract information about the strip’s position, orientation, movement, and deformation.

[0081]

[0080] As noted above, the more sensitive visual sensory equipment (such as cameras), may be placed at a sufficient distance from the heat and dust source to inhibit damage. This is unlike other conventional systems which use electronics which need to be positioned relatively close to the air knives 108 / strips 102 to function correctly, but which can be negatively impacted from such challenging environmental conditions. As such, the two or more visual sensors 12 of the present disclosure may be positioned far from the strip 102. For example, in some applications, the two or more sensors 12 may be positioned from 1 to 10 meters away from the strip 102. In a preferred application, the two or more sensors 12 may be positioned approximately 2 meters away from the strip 102. One or more of the visual sensors 12 may be placed at an elevation or plane that is different than the plane of the pattern source 14. The visual sensors 12 of the present disclosure may be any sensor that can detect a visual field (as opposed to a single point of light source).

[0082]

[0081] The pattern source 14 may comprise any pattern which can be seen by the sensors 12 on the strip 102. The pattern source 14 may be a diffuse material. The pattern source 14 may comprise a line.

[0083]

[0082] As depicted in Figure 6, for example, the pattern source 14 may be illuminated and reflected to result in a reflection 20 on the strip 102 which extends past each edge 103 of the strip 102. The pattern source 14 may continuously extend the entire width of the strip 102. The patterns source 14 may comprise one or more lines 22 which continuously extend the entire width of the strip 102 and extends past each edge 103 of the strip 102. The pattern source 14, which may include the light fixture, provides the pattern for projection or reflection onto the strip 102.

[0084]

[0083] In the depicted embodiment of Figure 6, for example, two line sources are shown which are orientated generally parallel to one another. Due to the deformation or bowed nature of the strip 102 in Figure 6, the two lines 22 in the reflected pattern 20 are also deformed or not straight. In other applications, the pattern source 14 may comprise more than two lines sources, and / or the line sources may be orientated at different angles from one another. The pattern source 14 in the depicted embodiment further includes a vertical reference feature 24. The vertical reference feature 24 may be a reference gap in the pattern source 14 / pattern 20. Where the pattern 14 is one or more lines, the vertical reference 24 may be one or more reference gaps in the one or more lines 22. The reference gaps may be provided by blocking a portion of the pattern source 14 from reaching the strip 102. The reference gaps may be provided by removing a portion of the pattern source 14. In other applications, instead of a vertical reference gap, the vertical reference feature 24 may be generated by a vertical light source or a vertical line pattern source. The vertical line pattern source may be physical objects or drawn lines on a material. The vertical light source or vertical line pattern source may comprise lines that extend in a more vertical direction than a horizontal direction. In some applications, the reference gap in the pattern source 14 may be positioned in the middle of the at least two line sources. In other applications, the reference gap may be positioned at a different location along the pattern source 14.

[0085]

[0084] Figure 7 illustrates various examples of different pattern sources that may be used in the disclosed vision system 10. When the pattern is projected onto or reflected by the strip 102, the line sources 14 are reflected onto the strip 102 such that the line reflections 20 extend across an entire width of the strip 102. The vertical reference feature 24 may be used for magnification calculations later on.

[0086]

[0085] The pattern source 14 may be passive or active (light emitting) that is positioned close to the strip 102. If the pattern source 14 is passive, the light source / fixture may be separate and remote from the pattern source 14, for illuminating the pattern source 14 for the pattern to be reflected by the reflective or semi-reflective strip 102. In some applications, the pattern source 14 may be a colored image, where lines are painted, printed, or made by stickers on top of a flat panel. In other applications, the pattern source 14 may be made of retro-reflective material. These materials are similarly used on road signs, where they return light in the same direction as the incident angle. In such cases, the light source would be positioned close to the cameras, so that the reflection is received by the cameras.

[0087]

[0086] If the pattern source 14 is active, the light source / fixture may be coupled to the pattern source 14 such that the light source projects the pattern as a light pattern from the pattern source onto the strip 102. For example, the pattern source 14 may be a grid of LED dots.

[0088]

[0087] In either case, the light sources / fixtures may be any known light sources. For example, the light fixtures may emit light with 660 nm wavelengths. The vision system 10 can alternatively or additionally work with any type of light, even invisible IR lights, that are invisible to the human eye, but would be visible to corresponding sensors 12, such as cameras.

[0089]

[0088] The less sensitive light source may be positioned close to the measurement point near the strip 102. In some applications, therefore, the light source may be positioned from 10 to 100 cm away from the strip 102. In a preferred configuration, the light source may be positioned 20 to 50 cm away from the strip 102.

[0089] The sensors 12 or cameras function to capture images of the pattern reflection 20 on the reflective surface of the strip 102. The captured images are then used to determine properties of the strip 102 in the coating system 100. To that end, as shown in Figure 8, for example, the vision system 10 further comprises a processor 30 that is coupled to the two or more 12 sensors / cameras.

[0090]

[0090] The processor 30 has memory comprising instructions that, when executed by the processor 30, cause the processor 30 to identify endpoints. Because of the reflective nature of the strip 102, it is often not possible to determine the location or orientation of the strip 102 from an image of the pattern 20 when the pattern 20 is solely within the strip 102. However, if the pattern 20 extends at least to the edges 103 of the strip 102 so as to intersect each edge 103, it is possible to identify endpoints 26 along each edge 103 of the strip 102, the endpoints 26 corresponding to the edge 103 of the strip 102. The instructions of the vision system and method may comprise an algorithm that assists with detecting an end of a line, generally. In some applications, the vision system and method of the present disclosure may use image processing algorithms to perform edge detection to identify the edge points 26. If the pattern 20 intersects with an edge 103 at at least two points, the method / system may detect two endpoints 26 along that edge 103. If at least two end points 26 are identified for an edge 103 of the strip 102, the system and method of the present disclosure may use those endpoints 26 to define a line passing between those endpoints 26, the line now representing one of the edges 103 of that strip 102. A line representing each of the edges 103 of a portion of the strip 102 may be used together to define the location and / or orientation of the portion of the strip 102. In other words, the locations where the system / method determines that the pattern ends 26 on each side of the strip 102 is determined to be the edges 103 of the strip 102. A 2D line is fitted to the edges 103 of the strip 102 in each image based on these endpoints 26 . In this way, the processor 30 may be configured to identify the endpoints 26 of the lines in the images that are intersecting at / with the edges 103 of the strip 102.

[0091]

[0091] The memory may further comprise instructions that, when executed by the processor 30, cause the processor 30 to determine properties of the strip 102 in the coating system 100 based on the images. Where edge endpoints 26 are identified from the images, the properties determined may comprise the position and / or orientation of the strip 102. Where vertically-aligned reference points, such as those resulting from the vertical reference feature 24, within the strip are identified, the properties determined may comprise the magnification effect of the strip 102 (as a result of the strip curvature combined with strip reflectivity). In an embodiment, a two-dimensional vertical line is fitted based on the two or more vertically-aligned edge endpoints / internal reference points of an image. Using the vision relations between the two or more cameras 12 (each camera obtaining at least one image of the same area of the strip 102 at the same time as the other camera 12 but from a different angle), a 3D (three-dimensional) line may then be determined based on the 2D (two-dimensional) line from each of the two or more images from those two or more sensors / cameras 12. In an embodiment, a 3D line is triangulated from the 2D line based on epipolar geometry formed by the two or more sensors / cameras 12. This process / method / system may provide the position and / or orientation of the strip edges 103 from which strip properties may be further determined and used in other processes. If more than two lines sources are provided as a pattern source 14, the additional endpoints 26 along the strip edges 103 can be used to help increase the measurement / computation accuracy.

[0092]

[0092] Deformations (including deflections and imperfections) in the strip 102 may be determined from the images using deflectometry. A vertical reference feature 24, such as a reference gap in the pattern source 14, may be used to determine the magnification of the pattern in the strip 102 due to the strip 102 being reflective. The vertical reference feature 24 may be any feature having a generally vertical orientation that can be captured appearing in the strip 102 using the sensors 12. For example, the vertical reference feature 24 may be provided using a vertical light source or a vertical pattern source. Determining the magnification may help better determine the magnitude of the deformation. In an embodiment, the reference gap in the pattern source 14 may also be reflected by, or projected onto, the strip 102. If there is a deflection, deformation, or imperfection in the strip 102, the image of the pattern source 14 on the strip 102 will be correspondingly distorted. The processor 30 may further be configured to calculate a magnification effect or factor of the (distorted) reflected reference gap on the strip 102 in the images relative to the reference gap in the pattern source 14. To do so, the reflected reference gap in the image and the reference gap in the pattern source 14 are measured. The magnification factor is then calculated by the processor 30 as a function of how the size of the reference gap in the images relate to the size of the reference gap in the pattern source 14.

[0093]

[0093] In the depicted embodiment of Figure 6, the pattern source 14 includes one vertical reference feature 24, in this case the reference gap, positioned in the middle along the two line sources 22. In other applications, the pattern source 14 may include more than one vertical reference feature 24 or reference gap and / or the reference gap(s) may be positioned at different places along the line sources 22. Such multiple and variously positioned reference gaps may be used to detect finer imperfections in the strip 102 (such as localized dents), continuous defects (such as streaks, ridges), and / or edge effects and imperfections.

[0094]

[0094] The present vision system 10 may be applied in coating systems 100 of any strips, which may be reflective, semi-reflective, or dull. In such cases, the present vision system 10 may further be adapted to determine the reflectivity of the strip 102 in use. Upon such determination, the present vision system 10 may adapt its calculations to the level of reflectiveness of its strip 102.

[0095]

[0095] Figure 4 illustrates an example feasibility study of the disclosed vision system 10 and method. Figure 5 illustrates the output of the edge positioning method and system of the example feasibility setup of Figure 4. The results of the study demonstrate that the present vision system and method can provide very accurate results. Pattern fixture 14 provides two lines of light towards a curved reflective strip 102. The reflective strip 102 reflects the lines of light 22 as a reflected pattern 20. The vision system 10 comprises two cameras 12 configured to capture the reflected pattern 20, namely, the two reflected lines of light 22 from the reflective strip 102. Since the reflective strip 102 is curved, the vision system 10 sees the reflected lines of light 22 as curved lines in two dimensional space. The vision system 10 may also detect the ends 26 of each of the two lines 22. Each of those ends (four in total as shown in Figure 4) is determined by the system to be an endpoint 26 which corresponds to a point on an edge 103 of the strip 102. Figure 5 shows four detected endpoints 26 and the output from the use of those endpoints 26 to determine properties of the strip 102. Properties include the position and orientation of the strip 102. From the strip endpoints 26, the strip width may be determined, three positional dimension of the strip edges may be determined, and 2 orientational dimension of the strip edges may be determined. Once the edges 103 of the strip 102 are identified, it is possible to determine the six dimension of the strip 102 (three positional dimension and three rotational dimension).

[0096]

[0096] After the position, orientation, motion, deformation, and / or defects of the strip 102 are identified by the processor 30, appropriate adjustments may be made to the coating method and / or system in response. For example, adjusting the position of the air knives 108 may be made relative to the strip 102 to modify and / or control the thickness of the coating, or the position of the correcting roll may be adjusted to minimize / mitigate crossbowing or other deformations of the strip 102. Other modifications of the coating system 100 in response to the vision system 10 determinations are possible for addressing other production or quality requirements.

[0097]

[0097] In an embodiment, the position of the strip detected in accordance with the present system and / or method (also referred to herein as strip localization) may be used to help control the position of edge baffles relative to the strip 102. Edge baffles (not shown) are separator walls that are at least partially positioned between the air knives 108 on either side of the strip 102, approximately coplanar with the strip 102. The presence of edge baffles flanking the strip 102 helps to prevent the collision of opposing air jets from the air knives 108, resulting in reduction of process noise and of edge overcoating on the strip 102. During the coating process, the position of the strip 102 may wander between the air knives 108, such as moving left, right, towards, or away from one of the air knives 108. To account for this, the edge baffles may be moved relative to the strip using actuators. As such, after the position (and orientation) of the strip 102, and in particular the strip’s edges, are identified by the processor 30 as discussed above, the actuators may be actuated to move the edge baffles in response to the location of the strip edges 103. In that regard, the edges baffles may track and stay parallel or generally coplanar with the strip 102 during the coating process, without needing to come in contact with the strip 102. In some applications, the actuators may only be configured to move the edge baffles left and right relative to the air knives 108 to track with the strip 102. In other applications, the actuators may also be configured to move the edge baffles towards and away from one of the air knives 108 to track with the strip 102.

[0098]

[0098] In the present disclosure, the term vertical and horizontal are relative to one another and may be interchanged and are with reference to the orientation of the strip and the strips direction of travel. In the present disclosure the strip is travelling in a vertical direction.

[0099]

[0099] Figure 9 illustrates a method 900 for determining properties of the strip in a coating process according to an example embodiment. The present method may be implemented using the vision system 10 as part of the CMC system 100 as described above to perform the functionalities noted above. In other embodiments, the method 900 may be implemented on a different system with different components to perform the functionalities noted above. The operations of the method 900 are intended to be illustrative. In some embodiments, the method 900 may be accomplished with one or more additional operations not described, and / or without one or more of the operations discussed. Additionally, the order in which the operations of the method 900 are illustrated in FIG. 3 and described below is not intended to be limiting.

[0100]

[0100] In some embodiments, the method 900 may involve one or more processing devices (e.g., a digital processor, an analog processor, a digital circuit designed to process information, an analog circuit designed to process information, a state machine, and / or other mechanisms for electronically processing information). The one or more processing devices may include one or more devices executing some or all of the operations of the method 900 in response to instructions stored electronically on an electronic storage medium. The one or more processing devices may include one or more devices configured through hardware, firmware, and / or software to be specifically designed for execution of one or more of the operations of the method 900.

[0101]

[0101] At operation 902, the method 900 comprises providing a pattern onto the strip. For example, providing the pattern on the strip may comprise providing the pattern so as to extend to each of the edges of the strip at least two points.

[0102]

[0102] At operation 904, the method 900 further comprises obtaining images of that pattern on the strip at the same time from at least two different angles. For example, obtaining the images may comprise capturing at least a first image from a first angle of view and a second image from a second angle of view of the pattern on the strip.

[0103]

[0103] At operation 906, the method 900 further comprises determining the properties of the strip based on the images. For example, endpoints may be identified from the images defined by the intersection of the pattern with the edges of the strip. In that manner, the properties of the strip based on the endpoints may be determined.

[0104]

[0104] In the preceding description, for purposes of explanation, numerous details are set forth in order to provide a thorough understanding of the embodiments. However, it will be apparent to one skilled in the art that certain details are not provided, such as to whether the embodiments described herein are implemented as a software routine, hardware circuit, firmware, or a combination thereof. The above-described embodiments are intended to be examples only. Alterations, modifications and variations can be effected to the particular embodiments by those of skill in the art.

Claims

1. CLAIMSWhat is claimed is:

1. A method for determining properties of a strip in a coating process, the method comprising: providing a pattern onto the strip; obtaining images of that pattern on the strip at the same time from at least two different angles; and determining the properties of the strip based on the images.

2. The method of claim 1, further comprising identifying two sets of vertically-aligned reference points from the images, fitting a two-dimensional line to each of the sets of refence points, converting the two-dimensional lines into a three-dimensional representation of the strip based the multiple images, and determining the properties of the strip based on the three-dimensional representation of the strip.

3. The method of claim 2, wherein the three-dimensional representation of the strip comprises an orientation or location of the strip, or a magnification effect of the strip.

4. The method of claim 2, wherein converting the two-dimensional lines into the three- dimensional representation of the strip comprises triangulating three-dimensional lines from the two-dimensional lines based on epipolar geometry formed by the angles from which the images are obtained.

5. The method of claim 2, wherein the vertically-aligned reference points comprise endpoints defined by the intersection of the pattern with an edge of the strip.

6. The method of claim 2, wherein the vertically-aligned reference points comprises points defined by the pattern that are interior to the edges of the strip.

7. The method of claim 6, wherein the vertically-aligned reference points comprise breaks within the pattern or vertical lines.

8. The method of claim 1, wherein providing the pattern comprises providing the pattern so as to extend to each of the edges of the strip at least two points; and wherein obtaining images comprises capturing at least a first image from a first angle of view and a second image from a second angle of view of the pattern on the strip; and further comprising identifying endpoints from the images defined by the intersection of the pattern with the edges of the strip, and determining the properties of the strip based on the endpoints.

9. The method of claim 8, wherein the pattern comprises two horizontal lines spaced vertically from one-another.

10. The method of claim 9, wherein the horizontal lines extend across the width of the strip.

11. The method of claims 9 or 10, wherein each of the horizonal lines is non-continuous in the same vertical locations to define at least two sets of vertically-aligned reference points that are interior to the edges of the strip.

12. The method of claim 1, wherein the pattern comprises one or more lines.

13. The method of claim 1, wherein the pattern comprises at least two lines.

14. The method of any one of the preceding claims, wherein the strip is a reflective or semi-reflective strip.

15. The method of claim 5, subsequent to identifying the endpoints from the images, further comprising determining locations of the edges of the strip based on the endpoints.

16. The method of claim 1, wherein the properties of the strip comprise one or more of position, orientation, movement, and deformations of or on the strip.

17. The method of claim 14, further comprising illuminating the pattern source for the pattern to be reflected by the reflective or semi-reflective strip.

18. The method of any one of claims 1-17, wherein the pattern source is a diffuse material.

19. The method of any one of claims 1-18, wherein the pattern source is made of retro- reflective material.

20. The method of any one of claims 1-19, wherein the pattern is provided onto the strip by projecting the pattern as a light pattern from the pattern source onto the strip.

21. The method of any one of claims 1-20, wherein a property of the strip is a deformation of the strip, and wherein the deformation is determined using deflectometry.

22. The method of claim 3, further comprising providing a vertical references on the strip to provide the two sets of vertically-aligned reference points, and identifying a deformation in the strip as a property based on the magnification effect.

23. The method of claim 3, wherein computing the magnification effect comprises comparing a known width between the two sets of vertically aligned reference points with a width between the two sets of vertically aligned reference points from the images.

24. The method of claim 22, wherein the vertical reference is a reference gap in the pattern.

25. The method of claim 22, wherein the vertical reference is a vertical light or a vertical line pattern.

26. The method of claim 13, wherein each of the lines comprises a reference gap therein, and identifying a deformation in the strip comprises computing the magnification effect based on the reference gaps in the lines on the strip from the images.

27. The method of claim 26, wherein providing the reference gap comprises providing an interruption or occlusion in the lines.

28. The method of any one of claims 1-27, further comprising adjusting an aspect in the coating process in response to the properties of the strip.

29. The method of claim 28, wherein adjusting an aspect in the coating process comprises one or more of: adjusting air knives, adjusting a correction roller, adjusting blower air pressure, adjusting line tension, adjusting roll alignments, adjusting the tension leveler, and adjusting an air baffle.

30. A vision system for determining properties of a strip in a coating system, the vision system comprising: a pattern source for positioning proximate to the strip for providing a pattern onto the strip; two or more sensors for capturing images of the pattern on the strip at the same time from at least two different angles; a processor coupled to the two or more sensors, the processor having memory comprising instructions that, when executed by the processor, cause the processor to determine the properties of the strip in the coating system based on the images.

31. The vision system of claim 30, wherein the memory comprises instruction for causing the process to identify two sets of vertically-aligned reference points from the images, fit a two-dimensional line to each of the sets of reference points, convert the two-dimensional lines into a three-dimensional representation of the strip based on the multiple images, and determine the properties of the strip based on the three-dimensional representation of the strip.

32. The vision system of claim 31, wherein the three-dimensional representation of the strip comprises the orientation or location of the strip, or the magnification effect of the strip.

33. The visions system of claim 31, wherein converting the two-dimensional lines into the three-dimensional representation of the strip comprises triangulating three-dimensional lines from the two-dimensional lines based on epipolar geometry formed by the angles of the sensors.

34. The vision system of claim 31, wherein the vertically-aligned reference points comprise endpoints defined by the intersection of the pattern with an edge of the strip.

35. The vision system of claim 31, wherein the vertically-aligned reference points comprises points defined by the pattern that are interior to the edges of the strip.

36. The vision system of any of claims 30-35, wherein the pattern sources comprises a line source configured to reflect as the pattern across the width of the strip.

37. The vision system any of claims 30-36, wherein the pattern source comprises two line sources configured to reflect across the width of the strip.

38. The vision system of any one of claims 30-37, wherein the strip comprises a coating providing a reflective or semi-reflective surface.

39. The vision system of claim 38, further comprising a light source for illuminating the pattern source such that the pattern from the pattern source is reflected by the reflective or semi-reflective strip.

40. The vision system of claim 38, wherein the pattern source is made of retro-reflective material and the light source is positioned between the two or more sensors.

41. The vision system of any one of claims 30-40, wherein the pattern source further comprises a light source to project the pattern as a light pattern onto the strip.

42. The vision system of any one of claims 30-41, wherein the memory comprises further instructions that, when executed by the processor, cause the processor to determine a deformation of the strip using deflectometry.

43. The vision system of claim 30, wherein the pattern source comprises a vertical reference source for providing a vertical reference on the strip, and the memory comprises further instructions that, when executed by the processor, cause the processor to identifya deformation in the strip by computing a magnification effect based on the vertical reference on the strip from the images.

44. The vision system of claim 43, wherein the vertical reference source is a reference gap in the pattern.

45. The vision system of claim 43, wherein the vertical reference source is a vertical light source or a vertical line pattern source.

46. The vision system of claim 30, wherein the properties are locations of edges of the strip, and further comprising edge baffles configured to be actuated to track the edges of the strip based on the locations of the edges of the strip.

47. The visions system of claim 30, wherein the memory comprises instructions that, when executed by the process, causes the process to perform the method of any of the preceding method claims.

48. A system for coating a strip comprising a vision system in accordance with any one of claims 30-47.

49. A strip coating system comprising: a bath of coating material; rolls for directing a strip through the bath; opposing air knives positioned on opposite sides of the strip downstream of the bath; and a vision system in accordance with any one of claims 30 to 48.

50. A strip coating system according to claim 49, further comprising actuators for controlling the location of the air knives relative to the strip, and wherein the actuators are configured to be controlled based on the properties determined by the vision system.

51. A strip coating system according to claim 35, further comprising a roll contacting the strip, and wherein the location of the roll is configured to be controlled based on the properties determined by the vision system.

52. A process for coating a strip, comprising: providing a strip through a bath of coating materials; providing the strip between opposing air knives;providing high pressure air onto each side of the strip using the air knives; determining properties of the strip based on the method of any one of method claims 1 to 29; and varying the process based on the properties of the strip determined in accordance with any one of the method claims 1 to 29.

53. The process of claim 52, wherein varying the process comprises adjusting the location of the air knives, the location of one or more rolls, or the location of edge baffles.

Images