WO2008040845A1 - Method and apparatus for analysing and controlling the manufacturing process of a web-like material - Google Patents

Method and apparatus for analysing and controlling the manufacturing process of a web-like material Download PDF

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Publication number
WO2008040845A1
WO2008040845A1 PCT/FI2007/050524 FI2007050524W WO2008040845A1 WO 2008040845 A1 WO2008040845 A1 WO 2008040845A1 FI 2007050524 W FI2007050524 W FI 2007050524W WO 2008040845 A1 WO2008040845 A1 WO 2008040845A1
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WIPO (PCT)
Prior art keywords
measurement
profile
web
variables
analysing
Prior art date
Application number
PCT/FI2007/050524
Other languages
French (fr)
Inventor
Mika SUOJÄRVI
Original Assignee
Savcor Wedge Oy
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Savcor Wedge Oy filed Critical Savcor Wedge Oy
Publication of WO2008040845A1 publication Critical patent/WO2008040845A1/en

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Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F7/00—Other details of machines for making continuous webs of paper
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21G—CALENDERS; ACCESSORIES FOR PAPER-MAKING MACHINES
    • D21G9/00—Other accessories for paper-making machines
    • D21G9/0009—Paper-making control systems
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B19/00—Programme-control systems
    • G05B19/02—Programme-control systems electric
    • G05B19/418—Total factory control, i.e. centrally controlling a plurality of machines, e.g. direct or distributed numerical control [DNC], flexible manufacturing systems [FMS], integrated manufacturing systems [IMS] or computer integrated manufacturing [CIM]
    • G05B19/41875—Total factory control, i.e. centrally controlling a plurality of machines, e.g. direct or distributed numerical control [DNC], flexible manufacturing systems [FMS], integrated manufacturing systems [IMS] or computer integrated manufacturing [CIM] characterised by quality surveillance of production
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F17/00—Digital computing or data processing equipment or methods, specially adapted for specific functions
    • G06F17/10—Complex mathematical operations
    • G06F17/15—Correlation function computation including computation of convolution operations

Definitions

  • the present invention relates to a method, according to the preamble of Claim 1, for analysing and controlling the manufacturing process of a web-like material.
  • the invention also relates to an apparatus for analysing and controlling the manufacturing process of a web-like material.
  • profile measurements of the paper web is generally used, with the aid of which variations in the paper quality both in the machine direction and in the cross direction can be determined.
  • Profile measurement is generally made using beam measurement, in which the measuring unit travels backwards and forwards over the paper web, while at the same time measuring one or more quality variables, for example, the moisture content, grammage, or ash content of the paper.
  • One pass over the paper web is referred to as a scan.
  • Profile measurement can also be implemented using a fixed measuring device extending over the entire web.
  • the invention is intended to eliminate the defects of the state of the art described above and for this purpose create an entirely new type of method and apparatus for analysing and controlling the manufacturing process of a web-like material.
  • the invention is based on combining profile-measurement information with other process measurements, with the aid of computational methods.
  • models of different degrees are formed for the results of the profile measurement, correlations with which are sought in the measurement results of the other stages of the process.
  • the apparatus according to the invention is, for its part, characterized by what is stated in the characterizing portion of Claim 7.
  • profile variations can be combined with other process measurements, so that the reasons for the profile variations can be found.
  • the aid of the invention it is possible to create connections between the complicated process's measurement data and the properties of the product in the final stage of the process and to control and/or analyse the process with the aid of the connections that are found.
  • Figure 1 shows graphically one result of a profile measurement according to the prior art, in which the paper's moisture value is shown with the aid of grey tones.
  • Time (machine direction) is on the x-axis and the paper's cross direction on the y-axis.
  • Figure 2 shows graphically some measurement and modelling results according to the invention.
  • Figure 3 shows graphically other measurement and modelling results according to the invention.
  • Figure 4 shows graphically details of Figure 3.
  • Figure 5 shows graphically a third set of measurement and modelling results according to the invention.
  • Figure 6 shows graphically details of Figure 5.
  • Figure 7 shows graphically a fourth set of measurement and modelling results according to the invention.
  • Figure 8 shows graphically a fifth set of measurement and modelling results according to the invention.
  • Figure 9 shows graphically other measurement results obtained from the process simultaneously with Figure 8.
  • Figure 10 shows schematically the measuring environment according to the invention.
  • profile measurements of the paper web are used, with the aid of which variations in the paper quality can be revealed both in the machine direction (longitudinal) and in the cross direction.
  • Profile measurement is usually performed using beam measurement, in which the measuring unit travels backwards and forwards over the paper web, measuring at the same time one or more quality variables, for example, the moisture content, grammage, or ash content of the paper.
  • One pass over the paper web is referred to as a scan.
  • One alternative form of profile measurement is also a measuring beam extending over the entire web width, in which case there is no need to move the measuring device.
  • the measurement result is typically displayed as a 'profile mat', in which the measurement value is shown with the aid of colours or grey tones, so that the areas, in which the measurement value is at a high or low level, can be seen from the image.
  • the objective is for the profiles to be as even as possible. If they are not, it is good to detect this as quickly as possible and to find the reason for the change in profile, so that the quality of the end product can be returned to an acceptable level. Though variation in a quality variable can be seen with the aid of the profile mat, this does not assist in determining the origin of the variation. At present, there is no method available, by means of which changes observed in profile measurements can be linked to the mill's process measurements.
  • mill process measurements are, for example, temperatures at different points, consistencies, pressures, chemical variables such as pH, running speed, stock ratios, grammage, stock grinding conditions (pressure, energy consumption), time passed since some operation (changing of a coating blade, time since previous break or shutdown), errors in measuring devices, including creeps.
  • the invention exploits, for example, besides the absolute values of the aforementioned process variables, also the change over time in the variables in question.
  • One objective of the invention is to determine the origin of profile variations.
  • the variations can be combined with other process measurements, so that reasons for the profile variations can be found.
  • the parameter series are compared with the other process measurements and reasons for the profile variation are sought.
  • Figure 2 shows examples of individual scans, in which 1 st - 4 th order deviations of a flat profile can be observed (skewed, U-shaped, S-shaped, W-shaped).
  • Figure 3 is an example of the profiles' 1 st - 4 th order parameters. Uppermost is a profile measurement as a time series and the polynomial adaptations corresponding to it temporally.
  • Figure 4 shows the period of time, in which the skew index has high values.
  • Figure 5 shows a profile measurement and the moment parameters corresponding to it temporally.
  • the origin of the profile change is sought with the aid of correlation calculation.
  • the period of time in which some parameter has changed significantly is examined.
  • the measurements are found that correlate most strongly with the parameter and which thus have most probably influenced the profile change.
  • Figure 8 shows the period of time marked in Figure 7.
  • the invention can be applied, for example, in connection with a paper machine 1, in which case the profile-measuring device is located at the end of the paper machine 1 (in this case at the right-hand side).
  • the various process measuring devices 3, as well as the profile-measuring device 2 have been combined in a computation unit 4, which takes care of the implementation of the methods described above.
  • the computation unit 4 can be, for example, a computer equipped with suitable software.
  • the block 4 can also provide output information on the basis of calculations made in the control systems 5 of the paper machine.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Mathematical Physics (AREA)
  • General Engineering & Computer Science (AREA)
  • Mathematical Analysis (AREA)
  • Mathematical Optimization (AREA)
  • Pure & Applied Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Data Mining & Analysis (AREA)
  • Computational Mathematics (AREA)
  • Software Systems (AREA)
  • Computing Systems (AREA)
  • Databases & Information Systems (AREA)
  • Algebra (AREA)
  • Manufacturing & Machinery (AREA)
  • Quality & Reliability (AREA)
  • Automation & Control Theory (AREA)
  • Paper (AREA)
  • Preliminary Treatment Of Fibers (AREA)

Abstract

The present publication discloses a method and an apparatus for analysing and controlling the manufacturing process of a web- like material. According to the method several variables (3) of the manufacturing process are measured and the data recorded in a time plane, cross-direction profile information (2) is measured in the final stage of the process from the web and the data recorded in the time plane. According to the invention the cross- direction profile information (2) is processed by computational methods using several modelling methods of different orders, the reasons for profile deviations are sought by searching for correlations with other measurement information on the process, and when a correlation is found with some other measurement variable, the process is controlled on the basis of the measurement result.

Description

Method and Apparatus for Analysing and Controlling the Manufacturing Process of a Web-Like Material
The present invention relates to a method, according to the preamble of Claim 1, for analysing and controlling the manufacturing process of a web-like material.
The invention also relates to an apparatus for analysing and controlling the manufacturing process of a web-like material.
Apparatuses and methods of this kind are used particularly in the paper industry.
According to the prior art, devices measuring the entire process and also profile measurement of the product at the end of the process are used.
In the monitoring of the quality of the paper produced by a paper machine, profile measurements of the paper web is generally used, with the aid of which variations in the paper quality both in the machine direction and in the cross direction can be determined. Profile measurement is generally made using beam measurement, in which the measuring unit travels backwards and forwards over the paper web, while at the same time measuring one or more quality variables, for example, the moisture content, grammage, or ash content of the paper. One pass over the paper web is referred to as a scan.
Profile measurement can also be implemented using a fixed measuring device extending over the entire web.
The invention is intended to eliminate the defects of the state of the art described above and for this purpose create an entirely new type of method and apparatus for analysing and controlling the manufacturing process of a web-like material.
The invention is based on combining profile-measurement information with other process measurements, with the aid of computational methods. In a preferred embodiment of the invention, models of different degrees are formed for the results of the profile measurement, correlations with which are sought in the measurement results of the other stages of the process.
More specifically, the method according to the invention is characterized by what is stated in the characterizing portion of Claim 1.
The apparatus according to the invention is, for its part, characterized by what is stated in the characterizing portion of Claim 7.
Considerable advantages are gained with the aid of the invention.
With the aid of the method, profile variations can be combined with other process measurements, so that the reasons for the profile variations can be found. With the aid of the invention it is possible to create connections between the complicated process's measurement data and the properties of the product in the final stage of the process and to control and/or analyse the process with the aid of the connections that are found.
In the following, the invention is examined with the aid of examples and with reference to the accompanying drawings.
Figure 1 shows graphically one result of a profile measurement according to the prior art, in which the paper's moisture value is shown with the aid of grey tones. Time (machine direction) is on the x-axis and the paper's cross direction on the y-axis.
Figure 2 shows graphically some measurement and modelling results according to the invention.
Figure 3 shows graphically other measurement and modelling results according to the invention.
Figure 4 shows graphically details of Figure 3. Figure 5 shows graphically a third set of measurement and modelling results according to the invention.
Figure 6 shows graphically details of Figure 5.
Figure 7 shows graphically a fourth set of measurement and modelling results according to the invention.
Figure 8 shows graphically a fifth set of measurement and modelling results according to the invention.
Figure 9 shows graphically other measurement results obtained from the process simultaneously with Figure 8.
Figure 10 shows schematically the measuring environment according to the invention.
Thus, when monitoring the quality of paper produced by a paper machine, profile measurements of the paper web are used, with the aid of which variations in the paper quality can be revealed both in the machine direction (longitudinal) and in the cross direction. Profile measurement is usually performed using beam measurement, in which the measuring unit travels backwards and forwards over the paper web, measuring at the same time one or more quality variables, for example, the moisture content, grammage, or ash content of the paper. One pass over the paper web is referred to as a scan.
One alternative form of profile measurement is also a measuring beam extending over the entire web width, in which case there is no need to move the measuring device.
The measurement result is typically displayed as a 'profile mat', in which the measurement value is shown with the aid of colours or grey tones, so that the areas, in which the measurement value is at a high or low level, can be seen from the image. The objective is for the profiles to be as even as possible. If they are not, it is good to detect this as quickly as possible and to find the reason for the change in profile, so that the quality of the end product can be returned to an acceptable level. Though variation in a quality variable can be seen with the aid of the profile mat, this does not assist in determining the origin of the variation. At present, there is no method available, by means of which changes observed in profile measurements can be linked to the mill's process measurements.
These mill process measurements are, for example, temperatures at different points, consistencies, pressures, chemical variables such as pH, running speed, stock ratios, grammage, stock grinding conditions (pressure, energy consumption), time passed since some operation (changing of a coating blade, time since previous break or shutdown), errors in measuring devices, including creeps. Naturally the invention exploits, for example, besides the absolute values of the aforementioned process variables, also the change over time in the variables in question.
One objective of the invention is to determine the origin of profile variations.
With the aid of the method, the variations can be combined with other process measurements, so that reasons for the profile variations can be found.
Stages of the method:
1. Parameters, with the aid of which the information contained in the profiles can be converted into time series depicting the profile variation, are calculated from consecutive scans,
2. The parameter series are compared with the other process measurements and reasons for the profile variation are sought.
Stage 1. Calculation of the parameters
From the consecutive scans various parameters, which are, for example, * polynomial adaptions, with the aid of which the shape of the scan can be characterized: skewed, U-shaped, S-shaped, W-shaped,
* moment calculations, with the aid of which information is obtained on the distribution of the scanning values: mean, mean dispersion, skewness, kurtosis.
Figure 2 shows examples of individual scans, in which 1st - 4th order deviations of a flat profile can be observed (skewed, U-shaped, S-shaped, W-shaped).
Figure 3 is an example of the profiles' 1st - 4th order parameters. Uppermost is a profile measurement as a time series and the polynomial adaptations corresponding to it temporally.
hi Figure 3", a circle marks the point at which the value of the parameter of the first order has increased, which tells that skewness has been observed in the profile scans. This point is shown in greater detail in Figure 4, in which eight consecutive scans are shown. The skews in the scans can be observed clearly from the image, i.e. the measurement values at the left-hand edge of the paper web are lower than those at the right-hand edge.
Figure 4 shows the period of time, in which the skew index has high values.
Figure 5 shows a profile measurement and the moment parameters corresponding to it temporally.
In Figure 5, a circle marks the point at which the value of the moment 4 has increased.
The positive values of this 4th moment indicate that strong peaks can be observed in the profile scans. This point is shown in greater detail in Figure 6, in which the consecutive scans can be seen 14. From the figure, the peaks in the scan values, i.e. values that deviate from the other measurement values either upwards or downwards, can be observed clearly in the scan values. Figure 6 shows the period of time in which the 4th moment has high values.
Stage 2. Determining the origin of a profile change
A period of time is examined, in which the skewness index has increased. Two vertical lines, between which the index of the 1st order has increased greatly, are marked in Figure 7. This means that at the start of the marked period of time the profile has been quite even, but at the end the scan values are considerably higher at one edge of the paper web compared to the other edge. Such a change in profile should be observed quickly and, on the other hand, the reason for it should also be found, so that the quality of the end product can be returned to an acceptable level.
In Figure 7, the values of the polynomial adaptation of the first order have increased in the marked period of time.
In the method disclosed, the origin of the profile change is sought with the aid of correlation calculation. In the calculation, the period of time in which some parameter has changed significantly is examined. By calculating the correlations between the parameter time series and the process measurements, the measurements are found that correlate most strongly with the parameter and which thus have most probably influenced the profile change. Figure 8 shows the period of time marked in Figure 7. As a result of the method, it was observed that, of the group of measurements analysed, the measurement of the consistency of the wire water correlated most strongly with the skewness index. This consistency measurement is in Figure 9. The correlation coefficient between these time series was -0.91.
According to Figures 8 and 9, the consistency of the wire water has decreased and at the same time the values of the polynomial adaptation of the first order have increased.
By means of the method disclosed, it is possible to automate the detection of profile changes and facilitate the search for the reasons for a profile change, by reviewing a large number of process measurements. As a result, the operator is informed of the most probable reasons for profile changes. However, the operator himself must make the final conclusions on the correctness of the reasons for the variations.
The above is an examination of quality-variable profiles. Another important application for the method is operating-device profiles. It is then possible to search for changes in the process measurements that force large changes to be made in the control values of a profile operating device, which can on the other hand cause problems in the quality of the end product. According to Figure 10, the invention can be applied, for example, in connection with a paper machine 1, in which case the profile-measuring device is located at the end of the paper machine 1 (in this case at the right-hand side). The various process measuring devices 3, as well as the profile-measuring device 2, have been combined in a computation unit 4, which takes care of the implementation of the methods described above. The computation unit 4 can be, for example, a computer equipped with suitable software.
The block 4 can also provide output information on the basis of calculations made in the control systems 5 of the paper machine.

Claims

Claims:
1. Method for analysing and controlling the manufacturing process of a web-like material, in which method
- several variables of the manufacturing process are measured and the data recorded in a time plane, and
- cross-direction profile information is measured in the final stage of the process from the web and the data recorded in the time plane,
characterized in that
- the cross-direction profile information is processed by computational methods using several modelling methods of different orders, - the reasons for profile deviations are sought by searching for correlations with other measurement information on the process, and
- when a correlation is found with some other measurement variable, the process is analysed or controlled on the basis of the measurement result.
2. Method according to Claim 1, characterized in that the other measurement information is analysed by the methods of the 1st order.
3. Method according to Claim 1 or 2, characterized in that the other measurement information is temperatures, consistencies, pressures, chemical variables, running speeds, stock ratios, grammages, stock grinding conditions (pressure, energy consumption), the time elapsed since some operation (changing of a coating blade, time from previous break or shutdown), creeps including errors of measuring devices, or a temporal change in the aforementioned variables, or the direction of the change, at various points in the process.
4. Method according to Claim 1, 2, or 3, characterized in that it is used for quality- variable profiles.
5. Method according to any of the above Claims, characterized in that it is used in device profiles.
6. Method according to any of the above Claims, characterized in that the skewness index of the profile measurement is applied to consistency measurement.
7. Apparatus for analysing and controlling the manufacturing process of a web-like material, which apparatus comprises means
- for measuring several different variables of the manufacturing process (3) and recording them in a time plane, and
- for measuring cross-direction profile information (2) in the final stage of the process from the web and recording the data in the time plane,
characterized in that the apparatus comprises in addition means
- for processing (4) the cross-direction profile information by computational methods using several modelling methods of different orders,
- for searching (4) for the reasons for profile deviations by searching for correlations with other measurement information on the process, and
- when a correlation with some other measurement variable is found, for analysing or controlling (4, 5) the process on the basis of the measurement result.
8. Apparatus according to Claim 7, characterized in that it comprises means (4) for analysing the other measurement information by the methods of the 1st - 4th orders.
9. Apparatus according to Claim 7 or 8, characterized in that it comprises means (4) for processing the following variables: temperatures, consistencies, pressures, chemical variables, running speeds, stock ratios, grammages, stock grinding conditions (pressure, energy consumption), the time elapsed since some operation (changing of a coating blade, time from previous break or shutdown), creeps including errors of measuring devices, or a temporal change in the aforementioned variables, or the direction of the change, at various points in the process.
PCT/FI2007/050524 2006-10-03 2007-09-27 Method and apparatus for analysing and controlling the manufacturing process of a web-like material WO2008040845A1 (en)

Applications Claiming Priority (2)

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FI20065628 2006-10-03
FI20065628A FI20065628L (en) 2006-10-03 2006-10-03 Method and apparatus for analyzing and adjusting the manufacturing process of a web-like substance

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2013087972A1 (en) 2011-12-15 2013-06-20 Metso Automation Oy A method of operating a process or machine
US9733626B2 (en) 2011-07-11 2017-08-15 Valmet Automation Oy Method of monitoring an industrial process
WO2017144785A1 (en) * 2016-02-25 2017-08-31 Valmet Technologies Oy Method, system and a computer program product for condition monitoring of a fiber web or paper finishing machine

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1995031602A1 (en) * 1994-05-16 1995-11-23 Valmet Corporation System for overall control of the different transverse profiles in a paper web manufactured by means of a machine for the manufacture of a web material, such as a board or paper machine and/or a finishing machine
WO1997039182A1 (en) * 1996-04-18 1997-10-23 Valmet Corporation Method for overall regulation of the headbox and/or the former of a paper machine or equivalent
WO1999042656A1 (en) * 1998-02-23 1999-08-26 Valmet Corporation System of regulation for a paper machine

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1995031602A1 (en) * 1994-05-16 1995-11-23 Valmet Corporation System for overall control of the different transverse profiles in a paper web manufactured by means of a machine for the manufacture of a web material, such as a board or paper machine and/or a finishing machine
WO1997039182A1 (en) * 1996-04-18 1997-10-23 Valmet Corporation Method for overall regulation of the headbox and/or the former of a paper machine or equivalent
WO1999042656A1 (en) * 1998-02-23 1999-08-26 Valmet Corporation System of regulation for a paper machine

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9733626B2 (en) 2011-07-11 2017-08-15 Valmet Automation Oy Method of monitoring an industrial process
WO2013087972A1 (en) 2011-12-15 2013-06-20 Metso Automation Oy A method of operating a process or machine
WO2017144785A1 (en) * 2016-02-25 2017-08-31 Valmet Technologies Oy Method, system and a computer program product for condition monitoring of a fiber web or paper finishing machine
US11008190B2 (en) 2016-02-25 2021-05-18 Valmet Technologies Oy Method, system and a computer program product for condition monitoring of a fiber web or paper finishing machine

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FI20065628A0 (en) 2006-10-03

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