DE102022208364A1 - Corrugated cardboard plant and method for monitoring a corrugated cardboard plant - Google Patents

Abstract

The invention relates to a corrugated cardboard system (2) and a method for monitoring such a corrugated cardboard system (2), wherein a defined area of a conveyor device (4) of the corrugated cardboard system (2) is specified as a test area (12), a camera system (20) with at least one Camera (22) is arranged with which images (11) are recorded, the camera (22) being aligned in the direction of the test area (12) in such a way that the test area (12) is depicted in the recorded image (11), and where With the help of the camera system (20), the position of the markers (14) is recorded and the test area (12) in the recorded image (11) is determined based on the recorded position. If a deviation of the imaged test area (12) from a target orientation (27) is identified, an automatic image correction is preferably carried out. This makes it possible to check the adjustment of the camera (22) and ensures reliable image evaluation for subsequent evaluation, for example for automatically checking whether the sheets (6) are flat.

Description

The invention relates to a corrugated cardboard system and a method for monitoring a corrugated cardboard system.

Corrugated cardboard systems are well known and are used to produce individual sheets of corrugated cardboard. When producing the sheets, the aim is to ensure that the individual sheets are as flat as possible, as this is a crucial criterion in terms of quality and further processing. Flatness is understood to mean that a respective arch is flat and without curvature. A deviation from such a flat position in the form of a curvature is also referred to as a “warp”.

From the EP 1 473 147 A1 Undesirable curvature of the arches is detected using a camera-based system. The height levels of various points on an arc are recorded and evaluated. Checking the sheets for deviations from flatness is also referred to below as “warp detection”.

Camera-based systems for monitoring a corrugating plant or for checking the corrugated cardboard produced are also well known. Markers are applied to the corrugated cardboard. For example, in the DE 10 2015 204 407 A1 a luminescence marker system is described.

Detecting a deviation from flatness requires a high level of accuracy in order to obtain reliable information about such a deviation in such a camera-based monitoring system.

Proceeding from this, the invention is based on the object of ensuring reliable monitoring of a corrugating cardboard system, in particular reliable monitoring of the sheets produced, especially with regard to a deviation from the flatness.

• - zumindest eine sich in einer Längsrichtung erstreckende und mit zumindest einem Förderband versehene Fördereinrichtung zur Förderung von Bögen aus Wellpappe angeordnet ist,
• - ein definierter Bereich der Fördereinrichtung, speziell des Förderbands als Prüfbereich (Region of Interest) vorgegeben ist,
• - mehrere Marker ortsfest an der Fördereinrichtung angebracht sind, die zu dem Prüfbereich korreliert sind,
• - ein Kamerasystem mit zumindest einer Kamera angeordnet ist, wobei vorzugsweise genau eine Kamera pro Förderband angeordnet ist, die zur Aufnahme von Bildern ausgebildet ist und die in Richtung zum Prüfbereich derart ausgerichtet und auch derart eingerichtet ist, dass im jeweils aufgenommenen Bild der Prüfbereich abgebildet ist,
• - wobei das Kamerasystem weiterhin zur optischen Erfassung der Position der Marker ausgebildet ist,
• - eine Auswerteeinheit angeordnet ist, die dazu eingerichtet ist, auf Basis der erfassten Position der Marker den Prüfbereich im dargestellten Bild zu bestimmen.

The object is achieved according to the invention by a corrugated cardboard system in which

• - at least one conveyor device extending in a longitudinal direction and provided with at least one conveyor belt is arranged for conveying sheets of corrugated cardboard,
• - a defined area of the conveyor device, especially the conveyor belt, is specified as a test area (region of interest),
• - several markers are fixedly attached to the conveyor device, which are correlated to the test area,
• - a camera system with at least one camera is arranged, with preferably exactly one camera being arranged per conveyor belt, which is designed to record images and which is aligned in the direction of the test area and also set up in such a way that the test area is depicted in the image taken ,
• - the camera system is further designed to optically record the position of the markers,
• - An evaluation unit is arranged which is set up to determine the test area in the displayed image based on the detected position of the markers.

• - ein definierter Bereich einer Fördereinrichtung der Wellpappenanlage als Prüfbereich vorgegeben ist,
• - ein Kamerasystem mit zumindest einer Kamera angeordnet ist, mit der Bilder aufgenommen werden und die in Richtung zum Prüfbereich derart ausgerichtet ist, dass im aufgenommenen Bild der Prüfbereich abgebildet ist,
• - wobei mit Hilfe des Kamerasystems die Position der Marker erfasst wird und auf Basis der erfassten Position der Prüfbereich im aufgenommenen Bild bestimmt wird.

According to the invention, the object is further achieved by a method for monitoring a corrugated cardboard plant, in which

• - a defined area of a conveyor device of the corrugated cardboard plant is specified as a test area,
• - a camera system is arranged with at least one camera with which images are recorded and which is aligned in the direction of the test area in such a way that the test area is depicted in the recorded image,
• - The position of the markers is recorded with the help of the camera system and the test area in the recorded image is determined based on the recorded position.

The advantages and preferred embodiment variants listed below for the corrugated cardboard system can also be applied to the process and vice versa.

The embodiments according to the invention are based on the consideration that for the reliable and precise evaluation of the images recorded with the camera system, particularly with regard to monitoring the flatness, a highly precise adjustment of the respective camera in relation to the test area, i.e. to the “region of interest” (ROI) is required. Furthermore, the invention is based on the knowledge that during operation of the system, even after an initial high-precision adjustment of the camera system, misalignment can occur, so that, for example, the recorded image has errors such as distortion or twisting compared to one correct adjustment of the camera. Such misalignment and the resulting image artifacts are for subsequent image evaluation disadvantageous, especially with regard to identifying whether the respective sheets are flat.

By determining the position of the markers in the displayed image, the actual image and orientation of the test area in the recorded image (imaged test area) is recorded. This test area shown in the image is taken into account for further image evaluation, in particular for warp capture.

In the method described here, the procedure is in particular with the help of automatic image evaluation in such a way that, based on the identified positions of the markers, the actual test area in the recorded image is determined and identified and preferably checked whether it is correctly represented in the image.

The test area preferably has a width that corresponds to the width of the conveyor belt. Furthermore, the test area has a depth in the longitudinal direction, which is preferably less than 1m and in particular in the range between 40cm and 75cm. Depending on the arrangement of the camera, the depth can also be greater.

For testing and evaluation, the evaluation unit has a suitable computing unit with a processor, memory, etc. Algorithms or computer programs are stored for the evaluation, with which the corresponding evaluations and tests are carried out fully automatically based on the recorded image data and, if necessary, other sensor data. Known or adapted image evaluation algorithms can be used for this purpose

The system according to the invention therefore also checks, in particular, a correct alignment of the at least one camera with respect to the test area based on the recorded position of the stationary markers. If incorrect alignment (misalignment) is detected, suitable measures are preferably taken to at least compensate for such a misalignment. This is done in particular by automatically correcting the captured image. The corrected image is then used for subsequent further automatic (image) processing, in particular for warp capture.

This check is carried out continuously during operation of the corrugator. This means that the camera system continuously records images that are continuously subjected to image evaluation. It is specifically provided that an image evaluation, in particular a warp capture, is carried out for each individual sheet and that the correct alignment is checked in advance as described here.

According to a first embodiment, individual images are recorded with the camera and, according to a second embodiment, image sequences are created and further processed in the manner of a stream.

It should be emphasized that the markers are stationary on the conveyor device, for example on the edge of the conveyor belt. These are therefore not markers attached to the corrugated cardboard. For example, the markers define the corner points of the test area.

The conveyor device is in particular a section of the corrugated cardboard system in the area of the so-called drying end. Specifically, the conveyor device is part of a storage system, which is arranged downstream of a cross cutter, which divides the endless corrugated cardboard produced into individual sheets. The sheets are placed in the storage system on one or more conveyor belts, which are also referred to as storage belts, and are further conveyed, for example to a stacking device. The individual sheets are stored and conveyed overlapping one another. They therefore lie on top of each other like scales. This is also referred to below as a scaled arrangement.

Often several conveyor belts are provided, which are arranged next to one another and in particular running one above the other. In such a case, such a camera system is installed on each conveyor belt. The at least one camera is aimed at a specific subarea of the conveyor device and specifically of the conveyor belt, which forms the test area of the conveyor device. This means that the camera images a portion of the conveyor device in a respective recorded image. The camera is adjusted in such a way that at least part of the recorded image depicts the test area.

If it is said here that the camera system is designed to detect the position of the markers, this is understood to mean an optical detection of the position of the individual markers. This is preferably done with the camera, which also images the test area.

Alternatively or in addition to this, there is also the possibility that separate additional optical sensors, for example additional cameras, are provided, with their position being firmly correlated to the position of the at least one camera that images the test area, so that one Correlation can be established between the position of the markers detected by these additional optical sensors and the image recorded by the camera.

Preferably, a predetermined target orientation is specified for the imaged test area, with the evaluation unit being set up to check the recorded images based on the recorded position of the markers to see whether the target orientation corresponds to the orientation of the imaged test area.

In particular, it is checked whether one or more edges of the test area are depicted in the image in the desired orientation. The markers are generally arranged opposite one another, in particular in pairs, along a connecting line transverse to the longitudinal direction. The connecting line therefore defines a predetermined orientation of the test area, which - when correctly adjusted - is oriented horizontally in the recorded image.

If a deviation from the target orientation is identified, in a preferred embodiment the recorded image is subjected to an image transformation using the evaluation device in such a way that the imaged test area assumes the predetermined target orientation. For this purpose, the image is subjected to a suitable image transformation. If, for example, it is recognized that the imaged test area is twisted or distorted relative to the target orientation, the image is rotated and/or rectified so that the imaged test area is brought into accordance with the target orientation. As a result of this measure, the image prepared in this way is available for subsequent further image evaluation, in particular with regard to the evaluation of the flatness (warp detection).

In a preferred embodiment, a recording area of the at least one camera is selected such that both the test area and the markers are simultaneously included in a respective recorded image. This makes particularly simple evaluation and checking possible, since the position of the markers is already included directly in the recorded image. With the help of automatic image evaluation, the position of the markers in the image is recognized and the actual test area shown in the image is determined. This is then compared in particular with the specified target orientation.

The optical markers have generally defined optical properties. Such optical properties are, for example, the color, a light intensity, a defined geometry of the marker or, when using active light pulses as markers, a predetermined pulse frequency. Furthermore, a filter is provided which is sensitive with regard to the respective optical properties. The filter can be an optical filter for the camera. This is, for example, temporarily moved in front of the camera and thus alternately, or alternatively it is permanently attached.

The filter is preferably an electronic filter which is integrated in the evaluation unit, specifically within the automatic image evaluation. “Sensitive to the respective optical property” is understood to mean that the filter is designed in such a way with regard to the optical property and, for example, has a certain bandwidth so that (only or mainly) the respective optical property (for example color) is passed through. With an electronic filter, the respective property is preferably highlighted and other image information that does not correspond to the optical property is at least partially suppressed.

This measure makes the individual markers clearly identifiable and, in particular, clearly distinguishable from the other image content, so that the automatic image evaluation becomes more reliable. Overall, such filtering ensures a clear assignment of the markers in terms of their position and thus a reliable identification of the test area in the recorded image.

In an expedient further development, the various markers differ in terms of their optical properties, such as those mentioned above, and the evaluation unit is designed to also identify these different optical properties, in particular with the help of automatic image analysis. This ensures that the position of the markers is recorded exactly and that, for example, the position of two markers is not accidentally swapped and assigned incorrectly.

According to a preferred, first embodiment variant, the markers are reflection elements, also referred to as reflectors, or luminescent elements. Specifically, these are, for example, glued-on films that are designed in particular as reflection films or are luminescent. Reflection elements are generally understood to mean that they have a degree of reflection greater than 0.8 or 0.9. Reflectance is the ratio between incident and reflected light.

In a preferred development, active illumination of the markers is provided in the embodiment variant with the reflection elements, so that Due to their high degree of reflection, these appear as luminous image elements in the captured image and can therefore be clearly identified.

If we are talking about reflection films here, this refers in particular to so-called retroreflective films, in which the incident light is reflected back at least largely independently of the angle of incidence in the direction of the irradiating light source and thus in particular back to the camera.

Such reflection elements or luminescent elements are also referred to here as passive markers because they do not have their own light source. The advantage of these special passive markers compared to other passive markers such as simple color marking is the improved visibility, so that the risk of evaluation errors during automatic image evaluation is reduced.

In a preferred development, the markers are active markers with at least one (active) lighting element. These are therefore also referred to as light-active markers. The lighting element forms an active, in particular controllable light source and is designed, for example, as an LED or as several LEDs. The use of active markers increases their visibility and identification in the captured image, so that image evaluation is reliable.

In an expedient embodiment, the lighting elements are designed to emit light pulses, i.e. H. a pulsating light signal is emitted by the active marker. A constant, predetermined pulse frequency is preferably set.

In the embodiment variant with the different optical properties of the different markers, in a preferred development, different markers have different pulse frequencies.

Especially when using variable markers, such as B. through the light pulses, a video or a stream is recorded and evaluated with the camera, so that the temporal changes, especially the pulsation/flashing and in particular the pulse frequency(s) are recorded and evaluated.

When using active markers, the lighting element is oriented in the direction of the camera in a preferred embodiment. This ensures reliable detection of the position of the marker.

In a preferred embodiment, an adjusting element for aligning the lighting element and/or a diaphragm is provided in the active marker. This is used in particular to align the lighting element in the direction of the camera or when aligning a diaphragm to align the light emitted by the lighting element.

In a preferred embodiment, the active marker has a diffuser or an optical filter which is arranged in front of the lighting element. Studies have shown that in certain situations overexposure can occur in the captured image due to the active lighting element, which is detrimental to further image analysis. The diffuser therefore reduces the light intensity that occurs. As an alternative to the diffuser, a suitable filter can be used, for example to reduce the light intensity.

The markers are preferably placed on the edge next to the conveyor belt of the conveyor device and in particular mark the corner points of the testing area. Alternatively, they have a fixed location relationship to the corner points of the edge area.

The test area is preferably a rectangular area. Preferably, at least four markers are provided, i.e. two on each edge side. Each marker is preferably assigned to a corner point of the test area.

The camera is preferably arranged at a distance from the test area opposite a conveyor device and thus against the longitudinal direction of the conveyor system. The camera is, for example, spaced from the test area in the range between 1 m and 4 m. Furthermore, the camera is preferably arranged above the conveyor belt, so that it is directed at the test area at an oblique angle.

In a preferred embodiment, the at least one camera is arranged centrally with respect to the conveyor belt, i.e. at half the width of the conveyor belt.

In a preferred further development, the evaluation unit is further set up to make statements about a property of the sheets, in particular about the flatness of the sheets, based on the recorded images. For this purpose, automatic image recognition methods are used. The course of an edge of the sheet is preferably evaluated with regard to curvature. The edge of the sheet is positioned in the specified image area and therefore in the test area.

According to the invention, a corrugated cardboard system with the features of claim 15 is also designed. This combination of features represents an independent invention. The right to file a divisional application based on this remains reserved. The aspects described below in connection with this further invention also represent preferred developments of the previously described corrugated cardboard system and the previously described method.

According to this aspect, an enclosure is attached in the area of the test area, which at least partially covers the conveyor device, at least the conveyor belt, and spans in the transverse direction transversely to the longitudinal direction. With the help of this enclosure, the test area is specifically shaded from the surroundings, so that the test area is at least partially protected and shaded from light coming in from the side or above. Furthermore, a lighting element is arranged which illuminates the test area and especially the front edge in a defined manner. This measure improves the visibility of the test area and in particular of the markers or end edges of the end edge arches, so that the automated image evaluation is more reliable and more accurate.

Thanks to the improved and dedicated illumination, for example, markers to identify the test area can be dispensed with. However, these are preferably still used as described above. The targeted lighting makes the markers easier to recognize, especially when using passive markers.

Another advantage of the enclosure is that, in addition to optical shading, the test area is also protected from contamination, for example.

In a preferred embodiment, the lighting element is dimmable, so that the luminosity can be adjusted. This enables the luminosity to be adjusted to the ambient lighting conditions and is also carried out during operation.

Alternatively or additionally, the light color can be adjusted. This can specifically improve the visibility of structures in the inspection area for the camera. Especially when using passive markers, the visibility of the markers can be improved by selecting the light color.

The lighting element is preferably attached to the housing, in particular to an inside. In a preferred embodiment, the enclosure generally has at least one side wall and preferably two side walls and a top wall. The top wall preferably spans the entire width of the conveyor belt. In particular, it connects the two side walls. These are, for example, attached to the edge of the conveyor device. Overall, the enclosure - in a view looking in the longitudinal direction - is L-shaped and preferably U-shaped. Due to the arrangement on an inside and in particular on the inside of the top wall, targeted illumination of the area shaded by the enclosure is achieved.

In a preferred embodiment, the lighting element is attached and/or shaded in such a way that the lighting element is not visible to the camera and/or that the light emitted by the ventilation element does not shine into the camera. The term “not visible” means that the lighting element cannot be seen in the image captured by the camera. At least the lighting element, especially a light cone emitted by the lighting element, is aligned in such a way that it does not shine into the camera. This ensures good visibility of the illuminated test area, in particular without overexposure (high brightness) of partial areas in the image recorded by the camera. In order to achieve this shading of the lighting element in the direction of the camera, for example, a diaphragm is arranged.

To ensure the best possible shading of the test area, the enclosure is made of an optically non-transparent, opaque material.

The enclosure is preferably only formed in the area of the test area, and therefore only extends over a section of the conveyor device. Specifically, it is adapted in the longitudinal direction to the length of the test area and, for example, has a length that corresponds to a range between 0.5 times and twice the length of the test area. The length preferably corresponds, for example, to 0.7-1.5 times the length of the test area.

The height of the enclosure is preferably in the range between 0.2 m and, for example, up to a maximum of 1 m and is preferably in the range of less than 0.7 m or even less than 0.5 m - based on the height of the conveyor belt. Overall, this means that a comparatively narrow area of the conveyor device is shaded and is therefore protected as well as possible from ambient light.

In a preferred embodiment, the lighting element extends transversely to the longitudinal direction and has several individually controllable areas. The individually controllable areas mean that specifically defined transverse areas can be illuminated. This is particularly useful if the entire width of the conveyor device is not used, i.e. if the sheets lying on it do not cover the entire width.

In particular, the lighting element has several lighting elements. Individual LEDs are preferably used as lighting elements. The lighting elements can be controlled either individually or in groups in order to form the controllable areas.

The different options described above, for example dimmability to set a suitable illuminance, setting the light color (especially through the use of RGB lamps) are preferably also implemented during the operation of the system, i.e. when carrying out the method, individually or in any combination carried out.

• 1 eine Fördereinrichtung als ein Teil einer Wellpappenanlage in einer seitlichen Querschnittsdarstellung,
• 2 eine perspektivische Aufsicht auf ein Förderband in Blickrichtung einer Kamera,
• 3 eine schematisierte Blockbild-Darstellung einer Kamera, einer Auswerteeinheit sowie von Markern,
• 4A, 4B Darstellungen zur Erläuterung der Korrektur eines aufgenommenen Bildes sowie
• 5 eine beispielhafte, stark vereinfachte Darstellung eines lichtaktiven Markers mit Kamera.

An exemplary embodiment of the invention is explained in more detail below in connection with the figures. These show in partly very simplified representations

• 1 a conveyor device as part of a corrugated cardboard system in a side cross-sectional view,
• 2 a perspective view of a conveyor belt in the direction of a camera,
• 3 a schematic block image representation of a camera, an evaluation unit and markers,
• 4A , 4B Illustrations to explain the correction of a captured image and
• 5 an exemplary, highly simplified representation of a light-active marker with a camera.

1 and 2 show in highly simplified representations as a section of a corrugated cardboard system 2 a portion of a conveyor device 4, by means of which individual sheets 6 made of corrugated cardboard are conveyed and transported in a conveying direction. The conveying direction also defines a longitudinal direction 8 of the conveying device 4. The conveying device 4 has a conveyor belt 10, which is guided by a belt carrier 11.

The individual sheets 6 lie on the conveyor belt 10, namely they each overlap a section in the longitudinal direction 8. During operation, the conveyor belt 10 runs continuously, so that the sheets 6 are continuously conveyed in the longitudinal direction 8. The conveyor belt 10 has a width transverse to the longitudinal direction 8, which is typically in the range between 100cm and 400cm and in particular in the range between 250cm and 350cm. This width defines the maximum corrugated board width that can be produced with the corrugator 2. In the exemplary embodiment, the width of the sheets 6 is significantly smaller than the width of the conveyor belt 10.

The conveyor 4 is assigned a predetermined sub-area as a test area 12. This one is in the 2 shown by dashed lines. It is preferably a rectangular partial area of the conveyor device 4, especially of the conveyor belt 10. In the exemplary embodiment, markers 14 are arranged at the corner points of the test area 12, namely on the edge of the conveyor belt 10. For example, they are integrated in a flange 16 on the edge. They are basically mounted in a stationary manner on the conveyor device 4.

The conveyor 4 also generally has a support frame 18 (see 1 ), via which the conveyor device 4 is attached to a floor, for example, and which is also designed to mechanically hold the conveyor belt 10. In the exemplary embodiment, only one conveyor belt 10 is shown. However, conveyor devices 4 often have several conveyor belts 10, which are arranged, for example, one above the other or next to one another. Typically, a respective conveyor belt 10 is arranged at an oblique angle and conveys the sheets 6 to a higher level. Following the conveyor belt 10, a stacking device for stacking the individual sheets 6 is usually arranged

A respective conveyor belt 10 is also assigned a camera system 20, which has at least one camera 22 and is formed by this in the exemplary embodiment. The camera 22 is positioned opposite the longitudinal direction 8 in front of the test area 12 and slightly above the conveyor belt 10. The camera 22 is oriented towards the test area 12, i.e. a detection area of the camera 22 is aligned with the test area 12.

The conveyor device 4 usually has a lighting device 24 with at least one lighting element, with the help of which at least a partial area and in particular the test area 12 is suitably illuminated. In the exemplary embodiment 1 Several lighting elements are shown. The illumination of the test area 12 ensures that the images I1 recorded by the camera 22 (compare, for example 4A) have sufficient quality for the intended image evaluation. Depending on the design of the markers 14, especially if they are designed as reflection elements or as luminescent elements, the lighting also ensures that the markers 14 can be easily recognized in the recorded image 11. In a preferred embodiment, it is specifically provided that a lighting element is positioned in the area of the camera 22 and irradiates the markers 14 from there.

• Die Papierbahnen werden von einem Abroller abgerollt und den weiteren nachfolgenden Komponenten der Wellpappenanlage 2 zugeführt. Für einen unterbrechungsfreien Betrieb sind beispielsweise sogenannte Splicer vorgesehen, mit deren Hilfe der unterbrechungsfreie Lauf auch bei einem Wechsel von Papierrollen ermöglicht ist.

A corrugator 2 is generally composed of several components. With the help of the corrugated cardboard system 2, continuous corrugated cardboard is first produced from paper webs, which is then cut to produce the individual sheets 6. The structure and mode of operation of such a corrugated cardboard system 2 is basically known and typically as follows:

• The paper webs are unrolled from a dispenser and fed to the other subsequent components of the corrugator 2. For example, so-called splicers are provided for uninterrupted operation, with the help of which uninterrupted running is possible even when changing paper rolls.

Using a so-called single-sided machine (single facer), a single-sided sheet of corrugated cardboard is first created. One of the paper webs is curled using a corrugated roller and then glued to one side with a first cover web. This is usually fed to other machines via a so-called bridge for further processing, and a second cover web is usually glued to the corrugated layer of the one-sided corrugated cardboard web opposite the first cover web. For this purpose, it is typically first fed to a so-called preheater. A glue unit is provided for gluing. In order to enable quality and trouble-free operation, heating devices, pulling devices and other belt guides are preferably provided for guiding the paper webs and/or the corrugated cardboard web produced. The section of a corrugator up to the production of the double-sided corrugated cardboard is referred to as the so-called wet end.

This is followed by the drying end. This involves processing and cutting the previously created endless corrugated cardboard web. Typically, a so-called short cross cutter is initially provided, with the help of which the so-called start-up waste is removed, for example when changing formats. Furthermore, the dry end, in particular downstream of the short cross cutter, has a cutting and creasing machine, which cuts or at least creases the corrugated cardboard web in the longitudinal direction and thus inserts defined click areas.

Finally, a so-called cross cutter is arranged below, which cuts the corrugated cardboard web in the transverse direction to produce the individual sheets 6. The storage system, which has the previously described conveyor device 4, is also arranged downstream of the cross cutter. The stacking device for stacking the individual sheets 6 is typically arranged downstream of the conveyor device 4.

• Gemäß 3 ist die Kamera 22 mit einer Auswerteeinheit 26 verbunden. Im Ausführungsbeispiel ist weiterhin dargestellt, dass die Auswerteeinheit 26 mit den Markern 14 verbunden ist, um diese beispielsweise anzusteuern. Dies ist insbesondere im Falle von sogenannten aktiven Markern 14 vorgesehen, welche ein aktives Leuchtelement 28 (vergleiche hierzu 5) aufweist.

The special design of the corrugated cardboard system 2 as well as the method for determining the test area 12 in images I1 recorded by the camera 22 will be discussed below in particular in connection with 3 , 4A as well as 4B explained in more detail:

• According to 3 the camera 22 is connected to an evaluation unit 26. The exemplary embodiment also shows that the evaluation unit 26 is connected to the markers 14 in order to control them, for example. This is particularly provided in the case of so-called active markers 14, which have an active lighting element 28 (see also 5 ) having.

During operation of the corrugated cardboard system 2, the camera 22 continuously records images and transmits the recorded images 11, i.e. the corresponding electronic image data, to the evaluation unit 26. The evaluation unit 26 is suitably set up to carry out automatic image evaluation and image processing. For this purpose, the evaluation unit 26 has at least one suitable processor and one or more suitable algorithms as well as a memory.

• Zunächst werden im aufgenommenen Bild I1 mithilfe einer automatischen Bilderkennung die im aufgenommenen Bild I1 dargestellten Marker 14 identifiziert und damit wird auch der im aufgenommenen Bild 11 dargestellte Prüfbereich 12 bestimmt.

The evaluation unit 26 carries out the following steps in particular, which are also related to: 4A and 4B be explained in more detail:

• First, the markers 14 shown in the captured image I1 are identified in the captured image I1 using automatic image recognition and the test area 12 shown in the captured image 11 is thus also determined.

In the next step, it is automatically checked whether the test area 12 shown occupies a predetermined target orientation 27. This is in the 4A and 4B represented by a thick dashed line and as a rectangle. When correctly adjusted, the camera 22 is typically oriented in such a way that a horizontal line in the image I1 shown runs parallel to a connecting line between two opposite markers 14. One Deviation of the connecting line from the horizontal indicates a rotation of the camera 22. During image evaluation, the connecting line is automatically determined based on the determined positions of two opposing markers 14.

Additionally or alternatively, it is also checked whether the angular position of the individual markers 14 relative to one another corresponds to an expected target angle. Due to the arrangement of the camera 22 above the conveyor belt 10 and in front of the test area 12, a vanishing point perspective results, which leads to a rectangular test area 12, for example, being shown in a trapezoidal shape in the picture 11 shown. A deviation from the expected target angles, for example, indicates a distortion.

If a deviation of the test area 12 shown in the recorded image 11 from the target orientation 27 is identified during this check, an image correction is preferably carried out automatically, in which an image transformation is carried out so that the test area 12 shown in the image assumes its predetermined target orientation.

In the 4A For example, a deviation from the target orientation 27 is shown by a rotation. During the image transformation, the test area 12 shown is rotated and brought into the desired sol orientation. As a result of this image processing, a corrected image I2 is obtained, which is preferably output and/or saved. The corrected image I2 is exemplary in the 4B shown.

The result of this image processing, especially the corrected image I2, forms the basic template for further automatic image evaluation, in particular for checking the flatness of the individual sheets 6. Due to the previous checking and, if necessary, correction of the orientation of the test area 12 shown in the image, a reliable automatic, camera-based Checking the flatness of the individual sheets 6 is possible.

In the 5 An example of an embodiment of a marker 14 is shown as an active marker 14. This has the already mentioned lighting element 28, specifically an LED, which emits light in the direction of the camera 22. The active marker 14 is preferably set up and/or positioned in such a way that the emitted light is oriented towards the camera 22. The light emitted is in the 5 represented by a light beam 30.

In the exemplary embodiment, the active marker 14 has a lens 32 connected upstream of the lighting element 28 and a diffuser 34. These elements are used to specifically set the desired bundling or expansion of the emitted light.

In the 5 A diaphragm 36 is also shown, which in the exemplary embodiment is designed as a circular ring segment which surrounds the lighting element 28 and which has a defined opening area.

Furthermore, in a preferred embodiment, an adjusting element 38, shown in a very simplified manner, is provided, with the help of which the aperture 36 can be adjusted and, in particular, rotated. This defines the orientation and/or expansion of the light beam 30.

In a preferred embodiment, the lighting element 28 emits light pulses with a defined frequency. A respective active marker 14 therefore flashes with a predetermined flashing frequency.

Preferably, 14 different frequencies are set and provided for the different markers, so that the markers can be distinguished based on the flashing frequencies.

The evaluation unit 26 is suitably set up to record and evaluate these flashing frequencies. For this purpose, in particular, several recorded images 11 are compared with one another. Furthermore, the image recording frequency of the camera 22 is sufficiently high to be able to identify and, in particular, evaluate the sequence of light pulses.

The camera takes a total of 22 images at a suitable capture rate (refresh rate). The recording rate, for example, is in the range of 30 to 60 frames per second (30Hz-60Hz). In principle, cameras with higher or lower recording rates can also be used.

The frequency for the light pulses is preferably matched to the recording rate of the camera and in particular coupled to it. For example, it is possible to determine the frequency of the light pulses based on the number of images between two light pulses. The frequency of the light pulses is therefore generally preferably smaller than the recording rate of the camera.

The camera 22 is preferably generally a CCD camera with a suitable CCD sensor with a suitable pixel density. A resolution of the camera 22 is sufficiently high. In particular, the resolution is in the millimeter range, ie two neighboring pixels in the recorded image I1 represent a real one Distance (of the test area 12) in the range of a few millimeters, in particular in the range of 1-5 mm.

In connection with the 2 As a preferred development but also as an independent invention, an enclosure 40 is designed in the area of the test area 12. This housing 40 is U-shaped in the exemplary embodiment and has two side walls 42 and a top wall 44, which connects the two side walls 42 to one another. The enclosure 40 spans the entire width of the conveyor 4 in the test area 12. In the exemplary embodiment, the enclosure 40 has a length in the longitudinal direction 8 which corresponds to the length of the test area 12. On the inside of the top wall 44, a lighting element 46 is arranged, which extends transversely over the conveyor belt 10. The lighting element 46 has, as individual lighting elements, in particular individual LEDs, which are lined up next to one another in the transverse direction. The lighting element 46 is therefore a type of LED bar. The lighting element 46 is dimmable and is preferably also dimmed depending on the current lighting situation during operation. Furthermore, in a preferred further development, there is also the possibility of setting the color, which is preferably selected during operation in order to make the visibility of desired structures within the test area 12 clearly visible in the camera image. In particular, this improves the visibility of end edges of the sheets 6 and/or the markers 14. The lighting element 46 has individually controllable areas or segments, which are preferably arranged next to one another in the transverse direction. These areas are in particular groups of individual LEDs.

Through this configuration, the test area 12 is suitably illuminated depending on the current requirements and lighting situation, with the intensity and/or the color being suitably adjusted for this purpose. The enclosure 40 with the defined illumination of the test area 12, for example, improves the visibility of the markers 14 or the end edges of the individual sheets 6, on the basis of which WARP detection is preferably carried out. The enclosure 40 protects the test area 12 from scattered light incident from the outside and other sources of interference as well as from contamination. A cone of light emitted by the lighting element 46 is preferably oriented obliquely in the downward direction, and overall preferably in such a way that a shadow cast by the front edge 26 is as prominent as possible.

Reference symbol list

2

Corrugator plant

4

funding facility

6

arc

8th

Longitudinal direction

10

conveyor belt

11

Ribbon carrier

12

Test area

14

marker

16

flange

18

support structure

20

Camera system

22

camera

24

lighting device

26

Evaluation unit

27

Target orientation

28

Lighting element

30

beam of light

32

lens

34

diffuser

36

cover

38

Control element

40

Enclosure

42

Side wall

44

Upper wall

46

lighting element

I1

captured image

I2

corrected image

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1473147 A1 [0003]
• DE 102015204407 A1 [0004]

Claims (17)

Corrugated cardboard plant (2), in which - at least one conveyor device (4) extending in a longitudinal direction (8) is arranged for conveying sheets (6) made of corrugated cardboard, - a defined area of the conveyor device (4) is specified as a test area (12), - several markers (14) are fixedly attached to the conveyor device (4), which are correlated to the test area (12), - a camera system (20) with at least one camera (22) is arranged, which is designed to record images (11) and which is aligned in the direction of the test area (12) in such a way that the test area (12) is depicted in the respective recorded image is, - wherein the camera system (20) is further designed to record the position of the markers (14), - An evaluation unit (26) is arranged, which is set up to determine the test area (12) in the recorded image (11) based on the detected position of the markers (14). Corrugated cardboard plant (2) according to the preceding claim, characterized in that a predetermined target orientation (27) is specified for the test area (12) shown, the evaluation unit (26) being set up to evaluate the recorded images (11) based on the recorded position of the Marker (14) to check whether the target orientation (27) matches the orientation of the imaged test area (12). Corrugated cardboard plant (2) according to the preceding claim, characterized in that the evaluation device is designed such that in the event of a mismatch between the target orientation (27) and the orientation of the imaged test area (12), the recorded image (I1) is subjected to an image transformation, such that the test area (12) shown assumes the specified target orientation (27). Corrugated cardboard plant (2) according to one of the preceding claims, characterized in that a recording area of the at least one camera (22) is selected such that both the test area (12) and the markers (14) are simultaneously in a respective recorded image (11). are included. Corrugated cardboard plant (2) according to one of the preceding claims, characterized in that the markers (14) have defined optical properties and that a filter is provided which is sensitive with regard to these optical properties. Corrugated cardboard plant (2) according to one of the preceding claims, characterized in that the different markers (14) differ in terms of their optical properties and the evaluation unit (26) is designed to distinguish the markers (14) based on the different optical properties. Corrugated cardboard system (2) according to one of the preceding claims, characterized in that the markers (14) are reflection elements and/or luminescent elements. Corrugated cardboard plant (2) according to one of the Claims 1 until 6 , characterized in that the markers (14) are active markers (14) with at least one lighting element (28). Corrugated cardboard system (2) according to the preceding claim, characterized in that the lighting elements (28) are designed to emit light pulses. Corrugated cardboard plant (2) according to the preceding claim, characterized in that the lighting elements (28) of different markers (14) differ in terms of frequency. Corrugated cardboard plant (2) according to one of the Claims 8 until 10 , characterized in that one or more of the following properties are fulfilled in the active marker (14), - the lighting element (28) is directed towards the camera (22), - it is an adjusting element (38) for aligning the lighting element ( 28) and/or a diaphragm (36), - a diffuser (34) or a filter is assigned to the lighting element (28). Corrugated cardboard plant (2) according to one of the preceding claims, characterized in that the markers (14) are each placed on the edge next to a conveyor belt (10) of the conveyor device (4) and in particular mark corner points of the test area (12). Corrugated cardboard plant (2) according to one of the preceding claims, characterized in that the at least one camera (22) is arranged above the conveyor belt (10) and at a distance from the inspection area (12) counter to the longitudinal direction (8). Corrugated cardboard plant (2) according to one of the preceding claims, characterized in that the evaluation unit (26) is set up on the basis of the recorded images (11). say about a property of the arches (6), in particular about the flatness of the arches (6). Corrugated cardboard plant (2), in particular according to one of the preceding claims, in which - at least one conveyor device (4) extending in a longitudinal direction (8) is arranged for conveying sheets (6) made of corrugated cardboard, - a defined area of the conveyor device (4) is specified as a test area (12), - preferably several markers (14) are fixedly attached to the conveyor device (4), which are correlated to the test area (12), - a camera system (20) with at least one camera (22) is arranged, which is designed to record images (11) and which is aligned in the direction of the test area (12) in such a way that the test area (12) is depicted in the respective recorded image is, - wherein the camera system (20) is preferably designed to record the position of the markers (14), whereby - In the area of the test area (12) an enclosure (40) covering the conveyor device (4) is attached, with a lighting element (46) being arranged which illuminates at least part of the test area (12). Corrugated cardboard plant (2) according to the preceding claim, in which one or more of the following features is/are implemented a) the lighting element (46) is dimmable and/or the light color is adjustable, b) a light cone emanating from the lighting element (46) is oriented obliquely towards the test area (12), c) the lighting element (46) is attached to an inside of the housing (40), d) the housing (40) has at least one side wall (42), preferably two side walls (42) and a top wall (44), e) the lighting element (46) is attached and/or shaded in such a way that the lighting element (46) is not visible to the camera (22) and/or the light emitted by the lighting element (46) does not shine into the camera (22), f) the enclosure (40) is made of an opaque material, g) the enclosure (40) is formed only in the area of the test area (12) and has a length in the longitudinal direction (8) which is in particular adapted to the length of the test area (12), for example in the range from 0.5 times to 2 - times the length of the test area (12), h) the lighting element (46) extends transversely to the longitudinal direction (8) and has a plurality of individually controllable areas, in particular a large number of individual LEDs, which can preferably be controlled individually or in groups. Method for monitoring a corrugated cardboard plant (2), in particular according to one of the preceding claims, in which - a defined area of a conveyor device (4) of the corrugated cardboard plant (2) is specified as a test area (12), - a camera system (20) with at least one camera (22) is arranged, with which images (11) are recorded and which is aligned in the direction of the test area (12) in such a way that the test area (12) is depicted in the recorded image (11). is, - The position of the markers (14) is recorded with the help of the camera system (20) and the test area (12) in the recorded image (11) is determined based on the recorded position.

Images