|Title of Invention||
AN APPARATUS FOR THE MONITORING OF TEXTILE SURFACE STRUCTURES
|Abstract||The invention concerns an apparatus for the automatic monitoring of textile surface structures, particularly sheets of fabric, with an electro-optical device for the continuous scanning of a surface structure (7, 8, 9). In order to create an apparatus which permits a more complete, more discriminating and more rapid detection of defects on textile surface structures and which is also suitable for the monitoring of a small number of looms, the apparatus has a group of several electro-optical devices (4, 5, 6), each device being assigned to a loom (1, 2, 3) and connected to a central processing unit (15) via a device for the transfer of data (12, 13, 14).|
|Full Text||The invention concerns an apparatus for the monitoring of textile surface structures, particularly sheets of fabric, with an electro-optical device for the continuous scanning of a surface structure.
In addition to the purely visual inspection of textile surface structures by the human eye which is still currently practised, there are also facilities for automated monitoring. Such an automated monitoring system is known from |N 163312. -—. In the case of this known apparatus, the sheet of fabric is linearly scanned on the loom by a scanning head which is transversely displaceable relative to the sheet of fabric, a signal being produced which has a relationship to the surface of the fabric. This signal is then processed and compared with reference parameters, so that a possible defect on the fabric can be detected from the signal. Such defects actuate an alarm on the loom or result directly in the stoppage of the loom. The operator thus receives a prompt to attend specifically to the machine concerned and to eliminate the cause of the fault if possible.
Various other possibilities for the inspection of fabrics are known from the literature listed below:
Meilland Textilberichte (Meilland Textile Reports) 1/1993, Dr. Bertram Nickolay, Dipl. Ing. Karlheinz Schicktanz, Dr. Harald Schmalfuss, "Automatische Warenschau - Utopie oder mogliche Realitat?" ("Automatic Goods Inspection - Utopia or Possible Reality?")
Computer Vision and Image Understanding Vol. 61, No. 2, March, pp. 231-262, 1995, Timothy S. Newman and Anil K. Jain, "A Survey of Automated Visual Inspection"
Textile Research Journal 65(4), 196-202, 1995, S. Sette, L. Boullart and P. Kiekens, "Self-Organizing Neural Nets: A New Approach to Quality in Textiles"
Helsinki University of Technology, November 1990, Ari Visa, "Texture Classification and Segmentation Based on Neural Network Methods"
Textile Research Journal 65(3), 123-130, 1995, I-Shou Tsai, Chung-Hua Lin and Jeng-Jong Lin, "Applying an Artificial Neural Network to Pattern Recognition in Fabric Defects"
However, although known goods inspection systems which check the fabric automatically have a high performance capability, they are also costly. A single goods inspection system, for example, can check the output from several dozen looms. In simpler and less expensive systems, however, inspection continues to be performed by the human eye.
A disadvantage of such known goods inspection systems is the fact that, in cases where they operate automatically without visual inspection, they are only financially worthwhile for a larger number of looms. Such goods inspection systems are too costly for monitoring the production of a few looms. On the other hand, in the case of inspection by the human eye in such systems, approximately only 70% of the defects on a sheet of fabric can be found. In particular, defects which are not pronounced are not detected by the eye. Known goods inspection systems are not really suitable for the inspection of brightly coloured fabrics.
In the case of the known automatic monitoring of fabrics on the loom, the nature and sequences of the defect can only be directly detected by the operator at the machine. Consequently, the decision concerning the measures to be taken also requires the operator to be present at the loom. If it is considered that an operator has to supervise and service 20
to 3 0 looms, then it is obvious that, in the event of a defect occurring on one of the looms, some time can elapse before the defect is detected and possibly eliminated and before the loom can resume operation. However, excessively long stoppages of a loom again result in defects in the fabric and in productivity losses. It is thus clear that both automatic defect detection and visual defect detection are problematical. For this reason, such systems have also not been widely adopted.
The invention, as characterized in the claims of the patent, now achieves the object of creating an apparatus which permits a more complete, more discriminating and more rapid detection of defects on textile surface structures and which is also suitable for the monitoring of a small number of looms.
The object is achieved in that each loom has an electro-optical device for the continuous scanning of a fabric, a group of electro-optical devices therefore being provided in which each electro-optical device is connected, through a device for the transfer of data, to a central evaluating unit.
The further advantages achieved by the invention are that it is possible to separate the monitoring of the quality and the machine-minding for the loom. Consequently, the defect types can be evaluated for all looms at a higher order station, for example by a specialist such as the head of the weaving workshop. The defects which can be detected on a loom can be evaluated immediately and, depending on the result of the evaluation, the loom can be stopped very rapidly following the occurrence of the defect. If various defects occur simultaneously on several machines or in rapid succession, then the defects can be weighted according to the damage anticipated or already caused and processed in the correct temporal sequence, or other measures of a preventive or other nature appropriate to the situation can be implemented. In the same way, and with the same apparatus according to the
invention, it is also possible to monitor warp-knitted fabrics or other textile surface structures such as knitted goods or nonwovens which are not produced by weaving on a loom but by an appropriate production method.
Accordingly, the present invention provides an apparatus for the monitoring of textile surface structures, particularly sheets of fabric, with an electro-optical device for the continuous scanning of a surface structure, characterized by a group of several electro-optical devices, each device being assigned to a loom and connected to a central evaluating unit through a device for the transfer of data.
The invention is described more fully below with the aid of examples and with reference to the accompanying figures, wherein
Figure 1 shows a simplified representation of the apparatus according to the invention,
Figure 2 shows a schematic representation of a part of the apparatus, and
Figures 3 and 4 each show, in the same manner as in Figure 1, a further embodiment of the invention.
Fig. 1 shows an apparatus according to the invention for three known looms 1, 2 and 3. Each loom 1, 2, 3 is fashioned and provided with an electro-optical device 4, 5, 6 for the continuous scanning of a textile surface structure, such as, in this case, a fabric 7, 8, 9. Each electro-optical device 4, 5, 6 consists, for example, of a sensor 10 and a
mounting 11. This sensor 10 can be disposed in a fixed manner on its mounting 11 and scan the entire width of the fabric 7, 8, 9, or it can be movably disposed and driven on its mounting 11 and, transversely relative to the longitudinal direction of the fabric, sweep over the entire width of the fabric with one movement. Also, the provided sensor 10 being in itself fixed, can be movable but not driven and mounted so that it can be set to the width of the fabric just woven, so that it can be centred above the fabric. The sensor 10 can scan a punctiform, linear or planiform portion or section of the surface structure or fabric 7, 8, 9 with, obviously, only a sensor capable of scanning a planiform or linear portion of the fabric or, if possible, the entire fabric, being capable
of being disposed in a fixed manner. The sensors 10 can be all known sensors, such a photocells, laser scanners, cameras, etc. If necessary, there is assigned to all sensors a first evaluating unit which generates an image or an image signal from the sensor signals, i.e., from lines or picture elements. In each case, therefore, the electro-optical device 4, 5, 6, which is known and therefore not described more fully here, is capable of delivering an image of a portion of the fabric 7, 8, 9 to a device for data transfer which, in this case, consists of a line or a bus 12, 13, 14. Each bus 12, 13, 14 is also connected to a central evaluating unit 15 which, in this case, in addition to a processor 16, also comprises a data output device 17 and a data input device 18. The central evaluating unit 15 comprises known means such as memories for the purpose of enabling the image signals to be retrieved for display on the data output device 17 and enabling a selection to be made from the available images from each loom 1, 2, 3. The looms 1, 2, 3 can also have lighting devices for the fabric 7, 8, 9, which are not described here but are known in the art.
Fig. 2 shows a possible configuration of a part of the central evaluating unit 15. It shows a sensor 19 connected via lines 20 to a high-pass filter 21 and a low-pass filter 22, which are thus connected in parallel. Signal detectors 23 and 24 are connected in circuit after the filters 21, 22 and connected to a switching element 25. The latter is connected to the signal detectors 23, 24 via control lines 26 and 27. A further switching element 28 is connected to one of the switching elements 23, 24 via a line 29. A comparable system is also conceivable without the filters 21, 22 but with the signal detectors 23, 24, which respond to threshold values which are set above and below the normal signal characteristic.
The apparatus described above operates as follows:
The electro-optical devices 4, 5, 6 deliver data continuously, via the lines 12, 13, 14, to the processor 16 which, if necessary, processes this data into image data which is displayed on the data output device 17, in the form of a monitor, as images of the fabric 7, 8, 9 and which can be selected via the data input device 18. Depending on the number of looms involved and the size of the scanned portion of the fabric 7, 8, 9, an operator can visually monitor the fabric on several looms at the same time, on the data output device. If too many looms are connected or in operation, it is advantageous to preselect the image data.
A simple preselection is possible by means of the system according to Fig. 2. In this case, image data is filtered in the high-pass filter 21 and the low-pass filter 22, to which it is delivered via the line 20. Depending on the design, the high-pass filter 21 filters out higher-frequency signals and delivers a signal to the signal detector 2 3 in which are amplified certain characteristics which are to be emphasized. The signal detector 23, which actuates the switching elements 25 and 28 via the lines 26 and 29, acts, for example, as a threshold detector. This means, for example, that the switching element 25 is closed when the signal from the high-pass filter 21 exceeds a set threshold value. Unfiltered image data can thus be selectively output for inspection, via the line 30, if the signal exhibits a peculiarity. In addition, the signal detector 2 3 can optionally control a switching element 28, via the line 26, so that, for example, a defect message or a special identification can be injected into the image data in the line 30. Following the delivery of a quantity of data which produces an entire image, the switching elements 25, 28 return automatically, for example, to the position indicated.
Likewise, particularly low-frequency signal components are captured in the low-pass filter 22 and exceptional signal components detected in the signal detector 24, as a result of
which at least the switching element 25 is closed. If the filters 21, 22 are included and operate digitally, it is necessary to provide a signal time-delay circuit 31 which delays the last image to be viewed and, consequently, the image data, for as long as this also occurs in the filters 21, 22. In this way, the viewer at the data output device 17 receives only those images which show fabrics in which there is a suspicion of defects. The filters 21, 22 and the signal detectors 23, 24 are to be designed so that the system reacts in a highly sensitive manner, so that even small variations in the fabric cause an image to be transmitted in the line 30. Any defect is then definitively evaluated by the operator. For the purpose of simplification, it is also possible to provide only one of the two filters 21, 22. This arrangement as in Fig. 2 can also be achieved analogously by appropriate programming of the processor 16.
However, other known methods of image processing, from other fields, are also applicable for the purpose of preselection. These include, for example, so-called gradient methods, texture analysis or the threshold value method. All can be executed in microprocessors using known digital signal processing. Whereas threshold value analysis is very simple although not very reliable, texture analysis operates reliably but involves a large degree of technical sophistication. Such methods, however, can extend beyond the bounds of preselection and even be used for detection of defects.
For the purpose of defect detection, it is also possible to create in the evaluating unit 15 a neural network to which are supplied, in a learning phase, known samples of defect-free fabrics and of corresponding defective fabrics, these samples being scanned as images in the network by an electro-optical device 4, 5, 6. The anticipated defects are specified by input via the data input device 18. In operation, images which include defects are then displayed automatically on the data output device 17. Instead of responding to entire
images, the neural networks can also respond to specific image parameters and combinations. Such parameters are constituted by, for example, the weft or warp thread sett, the weave type, the yarn thickness, etc.
Fig. 3 shows an embodiment in which each loom 1, 2, 3 has its own evaluating unit or its own processor 32, 33, 34 which can execute a first evaluation of the signals from the electro-optical device in respect of possible defects in the fabric. These processors can execute an evaluation in the sense of the arrangement depicted in Fig. 2, or execute higher-performance and more complex processes, as described above for preselection or actual automatic detection of fabric defects.
Fig. 4 again shows an embodiment with processors 32, 33, 34 as in Fig. 3, in which the device for data transfer has the processors connected in series, rather than in parallel as in Fig. 3. It is thus particularly simple to connect the central evaluating unit 15 to the looms 1, 2, 3 via a bus system 35 for the purpose of detecting defects in the fabrics. This can be achieved without difficulty due to the data reduction effected in the processors 32, 33, 34. The further evaluating units or processors 32, 33, 34 are preferably attached directly to the loom 1, 2, 3, as shown in Fig. 3.
The central evaluating unit 15 preferably has a device for the preselection of the image material delivered via each bus 12, 13, 14. This device is in the form of a simple filter. Such a filter can be of an analog or digital type and have, for example, a high-pass characteristic, so that the majority of the signal components are filtered out and signal components with a higher frequency are passed. Such signal components indicate a defect. Via the data input device 18 it is also possible to output signals to the processors 32, 33, 34 or to the electro-optical devices 4, 5, 6, for example to change parameters for the preselection of data or simply to stop the loom.
If defects have been detected on a fabric by the central evaluating unit 15 in any of the said forms, the defect must be rectified or at least removed. This may require it to be marked. For this purpose, the electro-optical device 4, 5, 6 can have a marking device which can likewise be controlled by the central evaluating unit 15 via the device for the transfer of data 12, 13, 14, 35. Another possibility is to deliver to the evaluating unit 15, via inputs 36, the current sett density, which is continuously determined in the loom in the known manner. By this means, in addition to the presence of a defect, its position on the fabric is also known, at least approximately, and can be captured in the central evaluating unit 15.
1. An apparatus for the monitoring of textile surface structures, particularly sheets of fabric, with an electro-optical device for the continuous scanning of a surface structure (7, 8, 9), characterized by a group of several electro-optical devices (4, 5, 6), each device being assigned to a loom (1, 2, 3) and connected to a central evaluating unit (15) through a device for the transfer of data (12, 13, 14).
2. The apparatus as claimed in claim 1, wherein the central evaluating unit has memories for the storage of images.
3. The apparatus as claimed in claim 1, wherein the electro-optical device is disposed so that it is capable of moving transversely relative to the longitudinal direction of the surface structure.
4. The apparatus as claimed in claim 1, wherein to each loom (1, 2, 3) there is in each case assigned one further evaluating unit (32, 33, 34) which effects a preselection or a detection of defect patterns and delivers these to the central evaluating unit (15).
5. The apparatus as claimed in claim 1, wherein the central evaluating unit (15) has a data output device (17), in the form of a monitor, by means of which images of the fabric can be visually evaluated.
6. The apparatus as claimed in claim 1, wherein the central evaluating unit (15) has filters (21, 22) for the filtering and selection of image data.
7. The apparatus as claimed in claim 1, wherein the device for the transfer of data
and the central evaluating unit (15) are designed for the output of signals to the loom.
8. The apparatus as claimed in claim 1, wherein the electro-optical device is disposed in a fixed manner.
9. An apparatus for the monitoring of textile surface structures, substantially as herein described with reference to the accompanying drawings.
|Indian Patent Application Number||336/MAS/1997|
|PG Journal Number||20/2006|
|Date of Filing||19-Feb-1997|
|Name of Patentee||M/S. USTER TECHNOLOGIES AG|
|Applicant Address||WILSTRASSE 11, CH-8610 USTER|
|PCT International Classification Number||GO1N 21/89|
|PCT International Application Number||N/A|
|PCT International Filing date|