JP2024112697A - Wrinkle Monitoring System - Google Patents

Abstract

To provide a wrinkle monitoring system which can determine the quality of wrinkles by monitoring the condition of the wrinkles on paper subjected to crepe processing.SOLUTION: A wrinkle monitoring system A includes: a paper machine 1; an Illumination 2 which emits light to paper P formed with wrinkles with crepe processing in the paper machine 1; a monitoring camera 3 to monitor the paper P; and a control device 4 which is connected to the monitoring camera 3 via the network N, and is used for monitoring the condition of the wrinkles. The control device 4 includes: acquisition means 41 which acquires an image of any area of the paper P imaged by the monitoring camera 3 from the monitoring camera 3; processing means 42 which applies image processing to the image and obtains a processed image i1; calculation means 43 which calculates the apex density being the summit number per unit area to the processed image i1; and determination means 44 which determines the quality of the wrinkles on the basis of whether or not the apex density exceeds a preset apex threshold.SELECTED DRAWING: Figure 1

Description

The present invention relates to a wrinkle monitoring system that can monitor the wrinkle condition of paper that has been creped using a papermaking machine and determine whether the wrinkles are good or bad.

Paper is a widely used industrial product in daily life, and systems have been developed to monitor the quality of paper during its manufacturing process.
For example, the monitoring device in Patent Document 1 is characterized by comprising an emitting means for shining light on paper running on a roll inside a papermaking machine, an imaging means for imaging the light of the emitting means that passes through the paper, an image processing means for processing images from the imaging means, and a diagnostic means for quantitatively monitoring the amount of fluctuation in the peeling point of the paper from the roll based on the processing results of the image processing means, and diagnosing abnormalities in the papermaking machine.

Incidentally, creping, which creates wrinkles in the paper, is widely used for household paper such as tissue paper to give it a pleasant feel (for example, Patent Document 2).

Crepe processing is a process in which the rotation speed of the roller on the side where the paper is sent out is made faster than the rotation speed of the roller on the side where the paper is taken up, thereby forming wrinkles in the paper.
The ratio of the rotation speeds of the two rollers at this time is called the crepe rate. By adjusting the crepe rate, various types of wrinkles are formed.

Patent No. 3268276 JP 2005-213691 A

The properties of creped paper change depending on the state of the wrinkles.
However, the crepe ratio, which is widely used as a criterion for wrinkles in creping, is calculated only from the number of rotations of the rollers and does not take into account other factors that affect the formation of wrinkles. Therefore, the numerical value of the crepe ratio does not necessarily correspond to the state of wrinkles, and the crepe ratio cannot be said to be an appropriate evaluation of creped paper.

Furthermore, the monitoring device in Patent Document 1 monitors manufacturing abnormalities, and does not monitor the condition of wrinkles, which are a given in creping.

The present invention has been developed in response to the above-mentioned problems.
That is, an object of the present invention is to provide a wrinkle monitoring system capable of monitoring the wrinkle state of creped paper and determining whether the wrinkles are good or bad.

After extensive research, the inventors discovered that it is possible to directly determine the state of wrinkles by monitoring the apex density of an image of wrinkled paper that has been subjected to at least brightness/dark processing. The present invention is based on this finding.

The present invention resides in wrinkle monitoring system A for monitoring the state of wrinkles, which includes a papermaking machine 1, lighting 2 that irradiates light onto papermaking P on which wrinkles have been formed by creping in the papermaking machine 1, a surveillance camera 3 for monitoring papermaking P, and a control device 4 connected to the surveillance camera 3 via a network N. The control device 4 includes acquisition means 41 that acquires from the surveillance camera 3 an image of an arbitrary area of papermaking P photographed by the surveillance camera 3, processing means 42 that performs image processing on the image to produce a processed image i1, calculation means 43 that calculates the vertex density, which is the number of vertices per unit area, for processed image i1, and judgment means 44 that judges whether the wrinkles are good or bad based on whether the vertex density exceeds a preset vertex threshold.

The present invention resides in the above-described wrinkle monitoring system A, in which the processing means applies at least differential filter processing to the image.

The present invention resides in the above-described wrinkle monitoring system A, in which differential filter processing is performed on the image at least in the conveying direction of the paper P.

The present invention resides in the above-described wrinkle monitoring system A, in which the number of vertices is the number of consecutive pixel groups in the processed image i1 whose luminance values are in a given range.

The present invention resides in the wrinkle monitoring system A described above, in which the calculation means 43 further calculates the surface area increase rate of the paper P due to the creping process, and the judgment means 44 further judges whether the wrinkles are good or bad based on whether the surface area increase rate is within a preset surface area threshold range.

The present invention resides in the wrinkle monitoring system A described above, in which the monitoring camera 3 is a line scan camera 3.

The present invention resides in the wrinkle monitoring system A described above, in which the papermaking machine 1 has a dryer roll DR that guides the paper P while drying it, and a light 2 and a monitoring camera 3 are installed on the front side of the paper P immediately after it passes through the dryer roll DR.

The present invention may also be implemented by appropriately combining the above configurations.

In the wrinkle monitoring system A, by providing a calculation means 43 for calculating the vertex density, which is the number of vertices per unit area, for the processed image i1, it is possible to directly monitor the wrinkle state of the paper P that has been creped by the device.
As a result, proper production of the desired wrinkles can be monitored.
As a result, instead of relying on sensory evaluation using the five human senses, it is possible to judge the softness of the paper P to the touch, etc., and reliably obtain the desired paper.
In addition, by providing a judgment means 44 that judges the quality of wrinkles based on whether the number of vertices exceeds a preset vertex threshold, if the calculated vertex density does not exceed the vertex threshold or there are signs that it may do so, it is possible to adjust the papermaking machine and continue papermaking while maintaining a good wrinkle state.

In wrinkle monitoring system A, the processing means 42 performs differential filter processing on the image to generate processed image i1, which makes it possible to make the wrinkles formed in the paper P in processed image i1 more distinct, and by using processed image i1, the calculation means 43 is able to detect even fine wrinkles.

In wrinkle monitoring system A, differential filter processing is performed on the image at least in the transport direction of the paper P, so that the contours of wrinkles in the transport direction of the paper P become clear in the processed image i1.
That is, since wrinkles caused by creping extend in the width direction of the paper P, the longitudinal direction of the wrinkles can be detected by performing differential filtering in the paper transport direction, improving the detection accuracy. This enables the calculation means 43 to more reliably find the contours of wrinkles that have become convex, improving the accuracy of the calculation of the apex density.

In wrinkle monitoring system A, the number of vertices is set to the number of consecutive pixel groups in processed image i1 whose luminance values are within a given range, making it possible to accurately monitor wrinkles caused by creping while excluding wrinkles caused by manufacturing anomalies.

The wrinkle monitoring system A calculates the surface area increase rate of the paper P due to the creping process, making it possible to monitor not only the state of wrinkles caused by the creping process of the paper P, but also the change in the bulk of the entire paper due to the creping process.

In the wrinkle monitoring system A, lighting 2 and a monitoring camera 3 are installed on the front side of the paper P immediately after it has passed through the dryer roll DR, making it possible to eliminate other factors as much as possible and monitor the wrinkle condition immediately after creping.

FIG. 1 is an explanatory diagram showing a wrinkle monitoring system. FIG. 2 is an explanatory diagram showing the control device. FIG. 3 is a flowchart showing the operation of the control device. FIG. 4 shows an enlarged view of the combined image. FIG. 5 is an enlarged view showing the processed image. FIG. 6 is an explanatory diagram for explaining the calculation of the vertex density. FIG. 7 is a graph of the change in luminance in the combined image.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings as necessary.
In the drawings, the same elements are given the same reference numerals and duplicated explanations are omitted.
In addition, unless otherwise specified, positional relationships such as up, down, left, right, etc. are based on the positional relationships shown in the drawings.
Furthermore, the dimensional ratios of the drawings are not limited to those shown in the drawings.

FIG. 1 is an explanatory diagram showing a wrinkle monitoring system A.
The wrinkle monitoring system A of the present invention comprises a papermaking machine 1 that produces paper P and applies creping processing to the paper P, a light 2 that irradiates light onto the paper P, a surveillance camera 3 for monitoring the paper P, and a control device 4 connected to the surveillance camera 3 via a network N.
The wrinkle monitoring system A is a system for monitoring the state of wrinkles formed in the paper P by creping in the papermaking machine 1.

The papermaking process is carried out in the papermaking machine 1, which has at least a wire part that makes the raw material into paper P, a press part that presses the paper P to remove moisture, a dry part that dries the paper P that has been dehydrated by the press part, and a reel part that winds up the paper P. In Figure 1, the papermaking machine 1 shows the dry part and the reel part. The papermaking machine 1 transports the base paper and paper P between each process by guiding them with rollers.

The creping process is carried out in the dry part. As described above, in the dry part, the paper P is conveyed while being guided by the dryer roll DR. At this time, in the papermaking machine 1, the semi-dried paper P is peeled off from the dryer roll DR by bringing a blade B into contact with the dryer roll DR. This peeling by the blade B causes wrinkles (crepe) in the paper P.
In creping, wrinkles are generated in the paper P, causing a change in length in the conveying direction, so the take-up roller R is rotated at a slower speed than the delivery roller (dryer roll DR).

The wrinkle monitoring system A has a monitoring camera 3 arranged in a direction to photograph the paper sheet P on the front side of the paper sheet P immediately after it has passed through the dryer roll DR on the most downstream side of the papermaking machine 1.
The surveillance camera 3 is a line scan camera that captures bar-shaped images with one pixel vertically.
The image capturing speed of the monitoring camera 3 is preferably 55,000 times/second or more, and more preferably 65,000 times/second or more, when the conveying speed of the paper P is, for example, 0 to 700 m/minute.
This makes it possible to properly photograph the state of wrinkles over the entire length of the paper P in the transport direction.

In wrinkle monitoring system A, since the monitoring camera 3 is a line scan camera 3, it is possible to ensure the shooting speed and to monitor wrinkles over the entire length of the paper P.
In addition, in the wrinkle monitoring system A, the lighting 2 and the monitoring camera 3 are installed on the front side of the paper P immediately after it has passed through the dryer roll DR, so that it is possible to monitor the wrinkle state of the paper P immediately after creping while excluding other factors as much as possible. Therefore, the paper P that has been subjected to creping can be more appropriately judged.

The line scan camera 3 captures a monochrome image of the paper P. As a result, each pixel in the captured image has only brightness data, and the data volume is smaller than that of a color image having RGB data, reducing the processing load.
As a result, it is possible to ensure the above-mentioned shooting speed, and the image processing described below can also be performed at a high speed.

The lighting 2 is disposed so as to illuminate the shooting range of the monitoring camera 3 from the upstream or downstream side of the monitoring camera 3 in the conveying direction at an acute angle to the conveying direction.
This makes it possible to photograph the wrinkles in the paper P in a state where their contours in the transport direction are more prominent.
For the lighting 2, an LED can be suitably used in terms of light quantity and low power consumption.

FIG. 2 is an explanatory diagram showing the control device 4.
The control device 4 is connected to the monitoring camera 3 via a network N. The monitoring camera 3 photographs the paper P in response to a command from the control device 4. The network N may be wired or wireless.
The control device 4 comprises an acquisition means 41 that acquires from the surveillance camera 3 an image of any area of the paper P photographed by the surveillance camera 3, a processing means 42 that applies differential filter processing to the image to produce a processed image i1, a calculation means 43 that calculates the vertex density, which is the number of vertices per unit area, for the processed image i1, and a judgment means 44 that judges whether the wrinkles are good or bad based on whether the number of vertices exceeds a predetermined vertex threshold.

A computer having a storage unit, a calculation unit, and a control unit can be suitably used as the control device 4. In this case, the acquisition means 41 corresponds to the storage unit.
The processing means 42 and the calculation means 43 correspond to a calculation unit.

FIG. 3 is a flowchart showing the operation of the control device 4.
The acquisition means 41 acquires images captured by the surveillance camera 3 .
As described above, the image captured by the line scan camera 3 is in the form of extremely thin lines.
The processing means 42 arranges and combines the plurality of linear images to generate a rectangular combined image i0 (see FIG. 4).
The processing means 42 combines approximately 45,000 to 55,000 images captured by the line scan cameras 3 into one combined image i0.
For example, when the paper P is transported at 700 m/min, the combined image i0 is an image of the paper P in a range of about 950 cm in the transport direction. This corresponds to about one revolution of the dryer roll DR when the diameter of the dryer roll DR is 3 m.

The processing means 42 performs image processing such as brightness adjustment and differential filter processing on the combined image i0. Here, the differential filter is a filter matrix having the same number of rows and columns and having any components. The differential filter processing is a convolution operation of the combined image i0 with the differential filter, with the filter matrix having luminance as a component.
In the wrinkle monitoring system A of this embodiment, the contour of the wrinkle is detected in the conveying direction. Therefore, in the filter matrix of the differential filter, the components of each row except for the top and bottom rows are set to 0.
By performing the differentiation process in the transport direction of the paper P, wrinkles formed in the width direction of the paper P by creping can be detected in the longitudinal direction, improving the detection accuracy.
Furthermore, by performing differential filtering in the transport direction of the paper P, the contours of wrinkles become clear in the processed image i1. At the same time, the load on the processing means 42 is reduced, enabling high-speed processing.

The processing means 42 performs differential filtering on the image captured by the surveillance camera 3 to obtain a processed image i1 (see FIG. 5).
By performing differential filtering by the processing means 42, the contours of wrinkles become clearer in the processed image i1, which enables the calculation means 43 to find even minute wrinkles and reduces the processing load.

The calculation means 43 measures the vertex density.
Here, the apex of the paper P refers to the peak of the wrinkles formed on the paper P by creping.
In this embodiment, wrinkle monitoring system A calculates the number of peaks (mountain tops) in convex (i.e. mountain) portions of the unevenness, and measures the apex density.

FIG. 6 is an explanatory diagram for explaining the calculation of the vertex density.
The calculation means 43 detects a group of consecutive pixels whose luminance values are within a given range as a vertex.
Specifically, the number of vertices is calculated as the number of pixel groups that are equal to or greater than an arbitrary value, that is, the number of pixel groups that are displayed as white masses in the processed image i1.
More specifically, the calculation means 43 finds a pixel having a luminance equal to or greater than an arbitrary fixed value, and determines that a pixel (group) adjacent to that pixel, which also has a luminance equal to or greater than an arbitrary fixed value, is one pixel group.

Specifically, the calculation means 43 scans the processed image i1 at least in the width direction of the paper P, and judges a pixel M1 (white part in FIG. 6) whose luminance is higher than an arbitrary fixed value as part of a mountain. Among the pixels adjacent in an arbitrary direction to the pixel judged to be part of the mountain, a pixel M2 whose luminance is equal to or higher than an arbitrary fixed value is judged to be part of the same mountain as the pixel M1 judged to be part of a known mountain. On the other hand, a pixel whose luminance is lower than an arbitrary fixed value (black part in FIG. 6) is judged to be a flat or wrinkled concave part.
In this case, since the pixels are arranged in a grid, the pixel in question has eight adjacent pixels on all four sides, above, below, left, right, and diagonally.
For this reason, a maximum of eight trials are performed.
The direction of the adjacent pixels to be detected is numbered from 0 to 7 in a counterclockwise direction, starting with the direction to the lower left of the pixel in question as 0.
(Number of previously detected direction + 6)/8
The direction of the remainder obtained by the formula:
This makes it possible to reduce the number of trials and the processing load on the calculation means 43 .

By repeating this process, when it reaches the pixel that was first determined to be part of a mountain, the group of consecutive pixels that were determined to be part of a mountain are determined to be a single mountain.

The wrinkles caused by the creping process occur in the width direction of the paper P.
Therefore, by the calculation means 43 determining that a group of consecutive pixels whose brightness is higher than an arbitrary fixed value is a single peak, i.e., a single wrinkle, the wrinkle monitoring system A is able to accurately and directly monitor wrinkles caused by creping, excluding wrinkles caused by manufacturing anomalies.

After determining one peak, the calculation means 44 resumes the above-mentioned scanning in the width direction. This calculates the number of consecutive pixel groups whose luminance is equal to or greater than a given value, and the calculation means 43 counts up the number of peaks. The calculation means 43 further calculates the vertex density by dividing the number of peaks obtained by the unit area.

The determining means 44 determines that the condition of the crepe is good if the apex density calculated by the calculating means 43 exceeds a predetermined apex threshold value.
Furthermore, the determining means 44 determines that the condition of the crepe is poor if the apex density is equal to or less than a predetermined apex threshold value.
This allows one to monitor whether the desired wrinkles are being properly produced.
As a result, instead of relying on sensory evaluation using the five human senses, it is possible to judge the softness of the paper P to the touch, etc., and reliably obtain the desired paper.
Furthermore, if the apex density calculated by the calculation means 43 does not exceed the apex threshold value or there is an indication that it will, it is possible to adjust the papermaking machine and continue papermaking while maintaining a good wrinkle state.
In addition, by changing the apex threshold, it is possible to deal with different types of wrinkles. The apex threshold can be set arbitrarily, for example, 30 to 50/ ^cm2 or 90 to 110/ ^cm2 , depending on the type of paper P (crepe paper) to be manufactured.

7 is a graph showing the change in luminance in the combined image i0, with the pixels on the line XX in FIG. 4 plotted on the horizontal axis and the luminance of each pixel plotted on the vertical axis.
That is, the length of the horizontal axis corresponds to the length of the paper P in the transport direction.
The calculation means 43 further calculates the surface area increase rate of the paper P due to the creping process. As described above, pixels with high brightness in the combined image i0 are convex (mountain) parts due to wrinkles, and pixels with low brightness are concave parts. Based on this, a graph is created with brightness on the vertical axis and the length in the conveying direction on the horizontal axis.
In this case, if the length of the horizontal axis (length in the conveying direction) is L1 and the length of the graph line is L2,
(L2-L1)/L1
By calculating the above, the increase in surface area due to creping can be approximately calculated.
By carrying out the above series of calculations for all pixels in the width direction and accumulating them, the increase rate of the surface area of the entire paper P due to the creping process can be calculated.

However, it is difficult to directly calculate the length of L2.
On the other hand, since the above value (L2-L1) can be considered as the sum of the differences in luminance between adjacent pixels, it is possible to approximately calculate the value of (L2-L1) by calculating the sum of the absolute values of the differences.

As the surface area of the paper P increases, the bulk of the paper P as a whole increases.
That is, by monitoring the rate of increase in surface area using the wrinkle monitoring system A, it is possible to directly monitor the change in bulk of the paper P due to the crepe process.
The determination means 44 further determines whether the creping is good or bad depending on whether the surface area increase rate calculated by the calculation means 43 is within a predetermined surface area threshold range. If the surface area increase rate is within the surface area threshold range, the strength of the creping is appropriate.
On the other hand, if the surface area increase rate is outside the threshold value, it can be determined that the intensity of the creping process is too high or too low.
In addition, by using the combined image i0 at this time, minute changes in brightness before the differential filter processing are plotted as a graph as they are, so that the wrinkle state of the paper P can be monitored more accurately.

Furthermore, the calculation means 43 can calculate the maximum peak height and the average peak height based on the above-mentioned graph. Similarly, the curvature of each peak and valley (the inverse of the radius of the approximation circle of the apex) and the variation thereof can be calculated. From these, the variation of wrinkles caused by creping and the intensity of the wrinkles can be measured (see FIG. 7).
From these, the uniformity of the crepe processing in the paper P can be judged.
As a result, it becomes possible to monitor the physical characteristics of the paper P in more detail.

Although the above describes a preferred embodiment of the present invention, the present invention is not limited to the above embodiment.

In this embodiment, the wrinkle monitoring system A performs differential filtering in the conveying direction of the paper P, but it may also perform differential filtering in the width direction of the paper P. In this case, it is possible to more accurately monitor wrinkles in the crepe.

In this embodiment, a line scan camera was used as the surveillance camera 3, but other types of cameras may also be used.

In this embodiment, the differential filter is a filter matrix with the same number of elements as the top row and the bottom row, with all elements except the top row and the bottom row set to 0, but the size and each element of the filter matrix used as the differential filter are arbitrary.

In this embodiment, the processing means 42 performs differential filtering on the image, but may additionally perform brightness processing such as noise removal, etc. In this case, it becomes easier to visually perceive the state of wrinkles from the image.
The processing means 42 may further perform binarization processing in addition to the differential filter processing, which enables the calculation means 43 to calculate the wrinkle apex density of the paper P with a lower burden.

In this embodiment, the combined image i0 is used to calculate the surface area increase rate, but the processed image i1 may also be used. In this case, the processing load on the calculation means 44 is reduced, enabling faster processing.

In this embodiment, the calculation means 43 calculates the convex peaks of the paper to measure the peak density, but it may also be configured to calculate the concave peaks (valley peaks) to measure the peak density.
In this case, the valley apex is the number of consecutive pixel groups whose luminance is equal to or less than a certain value in the processed image i0.
Also, both the peaks and valleys may be calculated.

In this embodiment, the wrinkle monitoring system A monitors the bulk growth rate of the paper P in addition to the apex density, but monitoring the bulk growth rate is not essential.

In wrinkle monitoring system A, the determination result may be output to the outside.
As a result, the control device 4 can be equipped with an output section, and can output the judgment result in a manner that can be recognized by humans, or can feed back the judgment result to the papermaking machine 1 to control the production of the papermaking machine 1.

The control device 4 may further include a learning means that learns the determination result by the determining means and changes the vertex threshold and the surface area threshold.
This makes it possible to improve the accuracy of the judgment by continuing papermaking.

The wrinkle monitoring system A of the present invention can be widely used in the production of paper P.
It can also be used to monitor paper P in the manufacture of paper P having unevenness other than that of paper P, such as embossing.

A: Wrinkle monitoring system B: Blade 1: Paper machine DR: Dryer roll R: Roller on the winding side 2: Lighting 3: Surveillance camera (line scan camera)
4: Control device 41: Acquisition means 42: Processing means 43: Calculation means 44: Determination means N: Network i0: Combined image i1: Processed image M1, M2: Pixels P: Papermaking

Claims (7)

A wrinkle monitoring system for monitoring the state of the wrinkles, comprising: a papermaking machine; a light for irradiating light onto papermaking that has been creped by the papermaking machine; a monitoring camera for monitoring the papermaking; and a control device connected to the monitoring camera via a network,
The control device,
An acquisition means for acquiring an image of an arbitrary area of the paper taken by the surveillance camera from the surveillance camera;
A processing means for performing image processing on the image to generate a processed image;
A calculation means for calculating a vertex density, which is the number of vertices per unit area, for the processed image;
a determining means for determining whether the wrinkles are good or bad based on whether the mountain apex density exceeds a preset apex threshold value;
A wrinkle monitoring system comprising: The wrinkle monitoring system of claim 1, wherein the processing means performs at least differential filtering on the image. The wrinkle monitoring system of claim 2, wherein the differential filter processing is performed on the image at least in the conveying direction of the paper. The wrinkle monitoring system of claim 1, wherein the number of vertices is the number of consecutive pixel groups in the processed image whose luminance values fall within a given range. The calculation means further calculates a surface area increase rate of the paper by the crepe processing,
2. The wrinkle monitoring system according to claim 1, wherein the determining means further determines whether the wrinkles are good or bad based on whether the rate of increase in surface area is within a preset surface area threshold range. The wrinkle monitoring system of claim 1, wherein the surveillance camera is a line scan camera. The papermaking machine has a dryer roll that guides the paper while drying it,
The wrinkle monitoring system according to any one of claims 1 to 6, wherein the lighting and the monitoring camera are installed on the front side of the paper immediately after it has passed through the dryer roll.

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