METHOD AND SYSTEM FOR COMPUTER-IMPLEMENTED TRACKING OF PRODUCTION HISTORY OF A CONTINUOUS WEB

Abstract

A method for computer-implemented tracking of production history of a continuous web is provided, which is-processed in a production system, including a sub-system applied to perform specific operation(s). The web is transported along a curved given path through the production system by winding/unwinding from/onto a coil. The following are performed: obtaining measured data of the web while being transported along the path, the measured data being current time-stamped measured data acquired a sensor or a measuring device installed at the production system along the path, where a spatial position of each sensor and measuring device with respect to the given path determined by a one-time reference calibration; obtaining movement information of the web; determining production-relevant features of the web by processing the time-stamped measured data and the movement information of the web by mapping the time-stamped measured data to physical points of regions of the web.

Claims

1. A method for computer-implemented tracking of production history of a continuous web, which is processed in a production system, comprising at least one sub-system applied to perform one or more specific operations, where the continuous web is transported along a given path through the production system by winding/unwinding from/onto a coil, wherein at each time point of one or more time points during the operation of the production system the following steps are performed: a) obtaining measured data of the continuous web while being transported along the given path, the measured data being current time-stamped measured data acquired by at least one of a sensor or a measuring device installed at or in the vicinity of the production system along the given path, where a spatial position of each sensor and measuring device with respect to the given path has been determined by a one-time reference calibration; b) obtaining movement information of the continuous web; c) determining production-relevant features of the continuous web by processing the time-stamped measured data and the movement information of the continuous web by mapping the time-stamped measured data to physical points of regions of the continuous web.

2. The method according to claim 1, wherein the spatial position of each sensor and measuring device with respect to the given path is determined by the one-time reference calibration, in which the following steps are performed: a1) attaching spatial markers on the continuous web; a2) moving the continuous web during calibration at a given velocity; a3) acquiring timestamps whenever a position of a certain sensor or a measuring device is crossed; a4) transforming time gaps between two adjacent positions into relative spatial distances or absolute coordinates of a first frame using a pre-defined first point of origin, the first frame being a coordinate system of the production system.

3. The method according to claim 2, wherein the first point of origin corresponds to a part of the production system, optionally being marked with a unique marker placed within the field of view of an optical sensor.

4. The method according to claim 2, wherein the first point of origin corresponds to a fixed marker observable in the field of view of the sensor located at an end of the given path.

5. The method according to claim 4, wherein projected positions of each sensor and measuring device along the given path are stored.

6. The method according to claim 1, wherein a pre-defined second point of origin of a second frame of the continuous web is obtained by processing measured data of a certain sensor or measuring device, the second frame being a web coordinate system.

7. The method according to claim 6, wherein the second point of origin corresponds to a visible characteristic of the continuous web observable in the field of view of the sensor located at the end of the given path.

8. The method according to claim 6, wherein the second frame refers to the continuous web fully unwound along its length dimension, where each physical point can be identified by coordinates along the unwound, length dimension and perpendicular to the length dimension, that runs along a width direction of the continuous web.

9. The method according to claim 8, wherein coordinates in the second frame comprise information about an upper side or a lower side of the continuous web.

10. The method according to claim 1, wherein in step c) the following steps are performed: c1) computing for each physical point or region of points on the continuous web the moment in time when the corresponding sensor or measuring device position along the direction of movement was crossed; c2) querying the time-stamped measured data to obtain the features which are associated to the corresponding sensor or measuring device; c3) storing the set of retrieved features for each point or region on the continuous web in a data base

11. The method according to claim 10, wherein the spatial position of the certain sensor or measuring device or a spatial interval between two adjacent sensors and, optionally, the side information are processed as a unique identifier.

12. The method according to claim 1, wherein the method is performed for a second subsequent production step, where a particular physical point or region of points on the continuous web is reidentified by matching a resulting feature vector which exhibits the highest similarity score in their corresponding feature domains.

13. An apparatus for computer-implemented tracking of production history of a continuous web, which is processed in a production system, comprising at least one sub-system applied to perform one or more specific operations, where the continuous web is transported along a given path through the production system by winding/unwinding from/onto a coil, wherein the apparatus comprises a processor configured to perform a method comprising the following steps: a) obtaining measured data of the continuous web while being transported along the given path, the measured data being current time-stamped measured data acquired by at least one of a sensor or a measuring device installed at or in the vicinity of the production system along the given path, where a spatial position of each sensor and measuring device with respect to the given path has been determined by a one-time reference calibration; b) obtaining movement information of the continuous web; c) determining production-relevant features of the continuous web by processing the time-stamped measured data and the movement information of the continuous web by mapping the time-stamped measured data to physical points of regions of the continuous web.

14. The apparatus according to claim 13, wherein the apparatus is configured to perform a method for computer-implemented tracking of production history of a continuous web, which is processed in production system, comprising at least one sub-system applied to perform one or more specific operations, where the continuous web is transported along a given path through the production system by winding/unwinding from/onto a coil, wherein at each time point of one or more time points during the operation of the production system the following steps are performed: a) obtaining measured data of the continuous web while being transported along the given path, the measured data being current time-stamped measured data acquired by at least one of a sensor or a measuring device installed at or in the vicinity of the production system along the given path, where a spatial position of each sensor and measuring device with respect to the given path has been determined by a one-time reference calibration; b) obtaining movement information of the continuous web; c) determining production-relevant features of the continuous web by processing the time-stamped measured data and the movement information of the continuous web by mapping the time-stamped measured data to physical points of regions of the continuous web, wherein the spatial position of each sensor and measuring device with respect to the given path is determined by the one-time reference calibration, in which the following steps are performed: a1) attaching spatial markers on the continuous web; a2) moving the continuous web during calibration at a given velocity; a3) acquiring timestamps whenever a position of a certain sensor or a measuring device is crossed; a4) transforming time gaps between two adjacent positions into relative spatial distances or absolute coordinates of a first frame using a pre-defined first point of origin, the first frame being a coordinate system of the production system.

15. A production system comprising at least one sub-system applied to perform one or more specific operations, where the continuous web is transported along a given path through the production system by winding/unwinding from/onto a coil, thereby passing at least one of a sensor or a measuring device, each of them being adapted to acquire measured data, wherein the production system comprises an apparatus according to claim 13.

16. A computer program product comprising a computer readable hardware storage device having computer readable program code stored therein, said program code executable by a processor of a computer system, to implement a method according to one of claim 12 when the program code is executed on the computer system.

17. The apparatus for computer-implemented tracking of production history of claim 1, wherein the continuous web is a continuous electrode carrier material.

18. The apparatus for computer-implemented tracking of production history of claim 13, wherein the continuous web is a continuous electrode carrier material.

Description

BRIEF DESCRIPTION

[0038] Some of the embodiments will be described in detail, with references to the following Figures, wherein like designations denote like members, wherein:

[0039] FIG. 1 is a schematic illustration of a production system comprising a controller for performing an embodiment of the invention;

[0040] FIG. 2 is a schematic illustration showing the step of determining production-relevant features by mapping time-stamped measured data and movement information of the continuous web; and

[0041] FIG. 3 shows a schematic flow chart of the method according to embodiments of the invention.

[0042] Generally, web production machines are applied to printing, coating or laminating continuous flat materials such as paper, textiles and plastics. They are used in many product and industry segments such as packaging and foil materials, printing services or adhesive coatings. Web machines combine several processing steps such as cutting, rolling and positioning that often extend over the entire shop floor.

[0043] The following description will be based, by way of example, on a coating process, in which active materials, so called battery slurry, are applied to a continuous web, i.e., an electrode carrier material. It is to be understood that the same or similar concepts can be transferred to other processes, like subsequent calendaring, slitting or cell assembly steps as well.

DETAILED DESCRIPTION

[0044] FIG. 1 shows a schematic illustration of a system 1 according to an embodiment of the present invention. The production system 1 consists of a coating machine for coating of a continuous web 5 in form of a continuous electrode material. The continuous web 5 is transported along a given curved path P through the production system 1, thereby being unwound from an un-winding coil 11 and wound onto a winding coil 23. In between, the continuous web 5 passes a plurality of sub-systems 10 of the production system 1. In the order starting from the un-winding coil 11 to the winding coil 23 the following sub-systems 10 are passed along the path P which are relevant for coating and providing measurements of relevant production and condition parameters: corona 12, moving cylinder 13, edge control device 14, coating device (coater) 15, wet layer thickness measurement device 16, dryer unit 17, dryer unit 18, dryer unit 19, surface weight measurement device 20, moving cylinder 21, and edge control device 22. Each of these sub-systems 10 may comprise a number of cylinders along which the web 5 is guided and redirected.

[0045] The production system 1 furthermore comprises a number of sensors 31, 32, 33 and measuring devices where only sensor 33 at the end of the given path P is illustrated in FIG. 1. Sensor 33 located at the end of the path P is an optical and/or infrared camera and placed such that a unique marker 24 is in the field of view of the sensor 33. The marker 24 represents, as will be described below, a first point of origin of a first frame MF. The first frame MP corresponds to a machine coordinate system, where the machine is represented by the production system 1.

[0046] The sensors 31, 32, 33 and measuring devices are mounted along the path P of the given process of the production system 1. Generally, sensors may be optical and/or infrared cameras, and so on. Measuring devices may be adapted to determine a coating layer thickness or a humidity of the coated material in one or more of the dryer units 17, 18, 19. A sensor and/or measuring device may also be adapted to acquire data in the surrounding of the production system 1, such as temperature or humidity.

[0047] Each of the sensors 31, 32, 33 and the measuring devices is communicatively connected to an apparatus 40 comprising a processor PR. Measured data MD acquired by the sensors 31, 32, 33 and the measuring devices are transferred to the apparatus 40 and stored in a data base 50 which is connected to the apparatus 40.

[0048] In order to be able to track a production history of the continuous web 5, a one-time preparatory step has to be carried out in which information about the spatial positions and other measurement properties for each of the sensors 31, 32, 33 and measuring devices along the given path P is gathered. This preparatory step consists of determining a one-time reference calibration for measuring/determining the spatial positions of the sensors 31, 32, 33 and the measuring devices along the curved path P.

[0049] First, spatial markers (not illustrated) are attached on the continuous web 5. The spatial markers may be removable or generated by semi-invasive techniques, such as by applying laser-code print marks on the edges on the continuous web 5. Next, the web 5 is moved at the path P during this reference calibration at a given velocity. In an embodiment, the velocity does not change during the calibration process. In order to be able to have precise calibration information, it is desired to move the web 5 at slow velocity (i.e., at a velocity which is less than the usual moving velocity of the web 5 during regular operation of the production system 1). Whenever a certain sensor position is crossed, a timestamp is acquired. Then, time gaps between two adjacent positions can be transformed into relative spatial distances or absolute coordinates of the first frame MF (machine frame) using the already mentioned pre-defined first point of origin (marker) 24.

[0050] FIG. 2 illustrates this setup and the definitions in a simplified manner. At the upper part of FIG. 2 an unwound path UP along its length dimension is illustrated. Along the unwound path UP the sub-systems 10 of the production system 1 and the sensors 31, 32, 33 and measuring devices are arranged. In the illustration of FIG. 2, for simplification reasons, only the un-winding coil 11, the coating device 15 and sensors 31, 32, 33 are shown. Sensor 33 corresponds to the aforementioned sensor at the end of the path P. As further already mentioned, the fixed marker 24 which is observable in the field of view of sensor 33 constitutes the first point of origin of the first frame MF (machine frame).

[0051] Each of the sensors and the sub-systems has a respective position P0, P1, P2, where a timestamp is acquired if a respective position of a certain sensor or measuring device is crossed. In FIG. 2, position P2 is crossed at time T_0. Position P1 of sensor 32 is crossed at time t=T_1. As the velocity of the moving web 5 is known, the distance d between each two adjacent positions can be determined. The distance d between positions P1 and P2 is outlined as d(T_1, T_0). Starting from the predefined first point of origin 24, the spatial positions of each the sensors 31, 32, 33 and measuring devices can be obtained.

[0052] The spatial positions are transformed into absolute coordinates p(T_0), p(T_1) with respect to the origin of the marker 24. The projected positions P0, P1, P2 of each sensor 31, 32, 33 and measuring device along the path is then stored in the data base 50.

[0053] To be able to track production relevant features PRF of the web 5 a pre-defined second point of origin 6 of a second web frame WF corresponding to a web coordinate system of the web 5 is obtained by processing measured data MD of a certain sensor 31, 32, 33 or measuring device. A practical choice for designing such origin on the web 5 is the leading edge of the coating area CA, as it is easily recognizable by optical image processing of the measured data MD of the camera (sensor) 33. More generally, the second point of origin is a visible characteristic of the web 5.

[0054] In FIG. 2, the unwound web 5 along the unwound path UP is illustrated at two different times T_0 and T_1 along time-axis t. The coated area is denoted with CA on the web 5. As can be seen from the unwound web 5 at time t=T_0, the leading edge of the coating area CA crosses sensor 33 and the marker 24 in the field of view of the sensor 33, respectively. At t=T_1, web 5 has moved according to the measured velocity of transport of the web 5 such that a physical point of web PPW which crossed sensor 31 at time t=T_0 now crosses sensor 32 at t=T_1.

[0055] For identification of physical points of regions of the web 5 it must be considered that electrode carrier material typically consists of two sides, namely an upper side 5u and a lower side 5l. In the coating process of FIG. 1, for example, the two sides are typically processed subsequently. An additional identifier s is used to distinguish between both sides 5u, 5l. Also, for some sensor measurements, like optical images, positions on the web 5 are not solely defined by the coordinate along the direction of movement (x-axis) but also along the orthogonal axis (y-axis).

[0056] The second frame DF refers to the continuous web fully unwound along its length direction. Each physical point, PPW can be identified by coordinates along the unwound, length dimension x and perpendicular to the length dimension x, which runs along a width direction y of the continuous web 5. A coordinate in the second frame WF therefore consists of three values x, y, s as attached to the physical point PPW in FIG. 2. The origin of the second frame thus has the coordinate (0,0, s).

[0057] Computer-implemented tracking of the production history of the web 5 is made by performing the following steps at each time point of one or more time points during the operation of the production system.

[0058] In a first step (S1 in FIG. 3), measured data MD of the web 5 are obtained while the web 5 is transported along the path P (see FIG. 1). The measured data are current time-stamp measured data MD which are acquired by the sensors 31, 32, 33 and any measuring device installed at or in the vicinity of the production system 1 along the path P. The measurements can comprise complex data structures, such as RGB images or hyperspectral infrared measurements. They also can comprise simple scalar values, such as temperature, humidity readings, or coating layer-thickness, or any combination thereof. It is to be noted that some of the sensors and measurement devices may be arranged in a room where the production system is built. For example, temperature, humidity values can be measured in the surrounding of the production system 1.

[0059] While being transported along the given path, a movement information MI of the continuous web 5 is obtained (S2 in FIG. 3). The movement information MI of the web 5 is continuously measured, e.g., via angular encoders or bar code scanning systems. The movement information is also stored as high-resolution time-series data. This allows to compute the distance travelled by the web 5 along the path P at any moment in time.

[0060] With these pre-requisites, production-relevant features PRF of the web 5 can be determined (S3 in FIG. 3). The determination takes place by processing the acquired time-stamped measured data MD and the movement information MI of the web 5 by mapping the time-stamped measured data MD to physical points or regions of the continuous web. This mapping corresponds to a coordinate transfer between the coordinates of the first frame MF to the coordinates of the second frame WF. As a result, a virtual electrode web representation containing production-relevant features PRF of physical points of regions of the continuous web 5 can be achieved. The production-relevant features PRF can be stored in the database 50.

[0061] To do so, for each physical point or region of points on the web 5 one can compute the moment in time when the corresponding sensor 31, 32, 33 or measurement device position along the direction of movement of the web 5 was crossed. This can be achieved by applying the measurement of movement as a function of time. Next, time-series measured data MD acquired beforehand can be queried to obtain the features which are associated to the corresponding sensor 31, 32, 33 or measuring device. Finally, the set of retrieved features is stored for each point or region on the continuous web 5 in the data base 50. The data base structure can be either centrally or at a shop-floor-level. The spatial position or spatial interval plus (upper/lower) side information can be used as a unique identifier.

[0062] Mapping of the movement of the web 5 along the path P, as observed from the web frame, is made as follows: first, an origin T.sub.0 along the time axis t is introduced. T.sub.0 is conveniently defined as the moment in time, when the origin 6 of the x-axis in the web frame WF (i.e., the leading edge of the coating area CA) coincides with the origin 24 along the web's path in the machine frame MF (i.e., the position of the marker 24 in the field of view of the sensor 33 at the end of the path P). In this moment all coordinate values of x correspond to the position along the path P.

[0063] Assuming that a measurement of the web velocity v(t) in the machine frame MF is available, by using a sensor measuring the velocity of the web 5, it can be calculated how much the web 5 has moved in time interval t=tT.sub.0:

[00001]$p\left(t\right)={}_{T_0}^{t}v\left(t^{}\right){\mathrm{dt}}^{}$

[0064] Thus, the position along path P at a certain point x.sub.0, y.sub.0, s.sub.0 of the web 5 for any moment in time can be computed by:

[00002]$p_{x_0}\left(t\right)=p_{x_0}\left(T_0\right)+p\left(t\right)=x_0+{}_{T_0}^{t}v\left(t^{}\right){\mathrm{dt}}^{}$

[0065] Thereby, p.sub.x.sub.0(T.sub.0)=x.sub.0 is assumed since x-axis and path P overlap at t=T.sub.0 by definition. In practice, the time integral over the velocity may be approximated by summation over discrete measurements of the velocity of the web v(t).

[0066] In order to map features like temperature or camera images according to the calculations above, the positions of the corresponding sensors 31, 32, 33 and measuring devices relative to the origin of the path P are used. As described above, relative distances are calculated by using the calibration run.

[0067] With the method described above, recording and mapping production features onto the electrode web within each dedicated process is possible. A (re-)identification and tracking of web positions or segments across separate processes can be made as follows. Assuming that a set of features has been correctly mapped to a physical point or point of regions of the web 5 in some production step A) (e.g., coating as described above), that particular segment can be re-identified by applying a similar procedure along a different production step B (e.g., calendaring) and then matching resulting feature vectors. In particular, given the spatial position and corresponding feature vector from the representation of step B, it can be searched for the spatial position during step A which exhibits the highest similarity in the corresponding feature domains. Such a solution can be used as a refinement or fine-calibration of physical positions across distinct processes where other solutions (e.g., laser markers as defined position) would only provide a coarse spatial resolution. Laser markers can simplify the search complexity in the features space by providing reasonable position interval limits, however.

[0068] Improving the accuracy of position determination or (re-)identification of feature patterns to provide a link between the frame production processes can be approached via Bayesian methods, such as Kalman Filters or Particle Filters: starting from rough conventional knowledge, e.g., the approximate location of web segments according to printed bar codes, each additional feature provides further information to recalibrate the matching score between web segments observed at different stages along the production, eventually allowing positioning accuracy in the range of a few centimeters, or better.

[0069] Although the present invention has been disclosed in the form of embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.

[0070] For the sake of clarity, it is to be understood that the use of a or an throughout this application does not exclude a plurality, and comprising does not exclude other steps or elements.