WO1991005105A1 - Cross direction profile control for multiple station web forming machine - Google Patents

Cross direction profile control for multiple station web forming machine Download PDF

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Publication number
WO1991005105A1
WO1991005105A1 PCT/US1990/004888 US9004888W WO9105105A1 WO 1991005105 A1 WO1991005105 A1 WO 1991005105A1 US 9004888 W US9004888 W US 9004888W WO 9105105 A1 WO9105105 A1 WO 9105105A1
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WIPO (PCT)
Prior art keywords
subprofile
machine
signals
profile
web
Prior art date
Application number
PCT/US1990/004888
Other languages
French (fr)
Inventor
Shih-Chin Chen
Original Assignee
Abb Process Automation Inc.
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 Abb Process Automation Inc. filed Critical Abb Process Automation Inc.
Publication of WO1991005105A1 publication Critical patent/WO1991005105A1/en

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Classifications

    • 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
    • D21G9/0027—Paper-making control systems controlling the forming section
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F11/00—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines
    • D21F11/02—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines of the Fourdrinier type
    • D21F11/04—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines of the Fourdrinier type paper or board consisting on two or more layers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/34—Paper
    • G01N33/346—Paper paper sheets

Definitions

  • the present invention relates generally to multiple station web forming machines and, more particularly, to a method and apparatus for concurrently controlling the processing stations of such machines.
  • the present invention is particularly applicable to multiple headbox paper making machines to concurrently control the headboxes for more even application of pulp slurry to wire screens of the paper making machines to thereby prevent coverage problems and improve the quality of paper produced. Accordingly, the invention will be described with reference to a multiple headbox paper making machine.
  • Paperboard making machines commonly employ multiple headboxes to distribute pulp slurry onto an endless wire screen, normally referred to only as a "wire", which then, passes through presses and over dryers to calenders and reels of the machine.
  • CD cross direction
  • weight and moisture variations or profiles i. e. weight and moisture variations laterally across the paper webs being made by the machines, are the composite result of the slices of pulp slurry which are deposited by the headboxes.
  • the slices are defined by the shape of the "slice” or elongated slurry depositing opening of each headbox. While the percent contribution of the total weight from each headbox can be approximately estimated from the amount of pulp slurry delivered by the headbox, the profile contribution from each headbox is very difficult to identify.
  • control arrangement for use in multiple headbox paper making machines to concurrently control the slices of the multiple headboxes such that the headboxes work together to ensure even pulp slurry distributions.
  • control arrangement would equally apply or be easily adapted to control multiple stage machines having at least two processing stations for making a web of material or performing an operation on a web of material, for example to control the moisture profile by concurrently controlling multiple CD moisture actuators.
  • a web of material such as paper
  • being manufactured or processed is monitored to generate a profile signal which in turn is separated into a number of subprofile signals corresponding to the number of processing stations to be controlled.
  • the contributions of the individual processing stations, such as headbox slices for the manufacture of paper, to various CD profile characteristics of the resulting web of material are frequency dependent wherein frequency is to be understood as being frequency in space laterally across the web or in the machine CD direction referred to herein generally as frequency or spatial frequency.
  • the profile signal representative of the web of material can be divided into two or more subprofile signals corresponding to the processing stations based on the frequencies representative of the stations.
  • the subprofile signals are then applied to the processing stations to control them to maintain one or more desired CD profile characteristics.
  • a method for controlling a paper making machine having at least two headboxes for applying pulp slurry to a wire of the machine to form a web of paper comprises the steps of: monitoring the web of paper; generating a profile signal representative of one or more characteristics of the web of paper in the machine cross direction; separating the profile signal into at least two subprofile signals corresponding to the at least two headboxes of the machine; and, applying the subprofile signals to corresponding headbox controllers to concurrently control the headboxes whereby slurry is more evenly applied to the wire to prevent coverage problems and improve the quality of the web of paper.
  • a method for controlling a multiple stage machine having at least two processing stations for making a web of material or performing an operation on a web of material produced by the machine comprises the steps of: monitoring the web of material; generating a profile signal representative of one or more characteristics of the web of material in the machine cross direction; separating the profile signal into at least two subprofile signals corresponding to the at least two processing stations of the machine; and, applying the subprofile signals to corresponding processing station controllers to concurrently control the processing stations whereby the web of material is more evenly made or processed to improve the quality of the web of material.
  • the step of separating the profile signal into at least two subprofile signals corresponding to the at least two processing stations or headboxes of a machine is preferably performed based on spatial frequencies of components of the profile signal.
  • the step of separating the profile signal into at least two subprofile signals may comprise the steps of: combining frequency components of the profile signal below a defined frequency to generate a subprofile signal for the primary processing station; and, combining frequency components above the defined frequency to generate a subprofile signal for the secondary processing station.
  • the defined frequency may be that which corresponds to a wavelength of approximately 7 to 9 actuator widths.
  • the step of separating the profile signal into at least two subprofile signals corresponding to the at least two processing stations of the machine may comprise the steps of: taking the Fourier transform of the profile signal; combining selected components of the Fourier transform of the profile signal to obtain subprofile Fourier transforms, the selected components being selected to correspond to the at least two processing stations; and, taking the inverse Fourier transforms of the subprofile Fourier transforms to obtain the subprofile signals.
  • the method may further comprise the steps of: determining what portions of the subprofile signals can be effectively utilized by their corresponding processing station controllers; generating residual subprofile signals by separating the utilized portions of the subprofile signals determined in the preceding step from the corresponding subprofile signals; and, feeding the residual subprofile signals forward for combination with subprofile signals for subsequent processing station controllers.
  • This "feed forward" control arrangement provides still more accurate control of the web profiles.
  • a system for controlling a paper making machine having at least two headboxes for applying pulp slurry to a wire of the machine to form a web of paper comprises sensor means for monitoring the web of paper and generating a profile signal representative of one or more characteristics of the web of paper in the machine cross direction.
  • Profile divider means separate the profile signal into at least two subprofile signals corresponding to the at least two headboxes of the machine.
  • Headbox controller means are responsive to the subprofile signals for concurrently controlling the headboxes to cooperatively apply the slurry more evenly to the wire thereby reducing coverage problems and improving the quality of the web of paper.
  • a system for controlling a multiple stage machine having at least two processing stations for making or performing an operation on a web of material produced by the machine comprises sensor means for monitoring the web of material and generating a profile signal representative of one or more characteristics of the web of material in the machine cross direction.
  • Profile divider means separate the profile signal into at least two subprofile signals corresponding to the at least two processing stations of the machine.
  • Processing station controller means are responsive to the subprofile signals for concurrently controlling the processing stations such that the web of material is more evenly made or processed to improve the quality of the web of material.
  • the system for controlling a multiple stage machine having at least two processing stations or headboxes for paper manufacture preferably comprises a digital computer for processing the profile signal into the subprofile signals based on the spatial frequencies of components of the profile signal.
  • the profile divider means may comprise a digital computer programmed to combine the frequency components of the profile signal below a defined frequency to generate a subprofile signal for the primary processing station, and to combine the frequency components above the defined frequency to generate a subprofile signal for the secondary processing station.
  • the defined frequency may be that which corresponds to a wavelength of approximately 7 to 9 actuator widths.
  • the profile divider means may comprise a digital computer programmed to take the Fourier transform of the profile signal, to combine selected components of the Fourier transform of the profile signal to obtain a subprofile Fourier transform for the primary processing station, to combine the remaining components of the Fourier transform to obtain a subprofile Fourier transform for the secondary processing station, and to take the inverse Fourier transforms of the subprofile Fourier transforms for the primary and secondary processing stations to obtain corresponding subprofile signals.
  • the profile divider means may comprise a digital computer programmed to take the Fourier transform of the profile signal, to combine selected components of the Fourier transform of the profile signal to obtain subprofile Fourier transforms, the selected components being selected to correspond to the at least two processing stations, and to take the inverse Fourier transforms of the subprofile Fourier transforms to obtain the subprofile signals.
  • FIG. 1 is a schematic side view of a dual headbox paper making machine for which the present invention is particularly applicable;
  • Fig. 2 is a block diagram of a system in accordance with the present invention for concurrent control of web processing stations;_
  • Figs. 3A, 3B and 3C are perspective plan views of sections of a paper making machine illustrating a headbox, a steam profiler and a web sensor platform, respectively, and also various web conveying rollers, wires and reels;
  • Fig. 4 is a graph illustrating potential problems which can result if multiple headboxes of a paper making machine are not properly coordinated;
  • Fig. 5 is a graph illustrating basis weight and moisture profiles generated by monitoring a web of paper
  • Figs. 6 and 7 are graphs illustrating subprofiles generated in accordance with the present invention from the profiles of Fig. 5.
  • FIG. 1 is a schematic side view of a dual headbox paper making machine 100 including a primary headbox 102 and a secondary headbox 104.
  • the primary headbox 102 is shown in perspective in the machine of Fig. 3A which illustrates in more detail, although still schematically, the primary headbox 102.
  • a headbox slice 106 is defined by a slice lip 108 which is controlled along its length by basis weight actuators 110.
  • Pulp slurry is conveyed to the primary headbox 102 via a stock pipe 112 and to the secondary headbox 104 such that slurry can be applied to a wire 114 to form a paper web 116.
  • the web 116 passes along the wire 114 and other parts of the paper making machine 100, it is processed by passing over foils 118, deflectors 120 and suction boxes 122.
  • the web 116 may also be acted upon by one or more processing stations along the length of the machine 100, for example by a steam profiler 124 schematically shown in Fig. 3B.
  • a steam profiler 124 schematically shown in Fig. 3B.
  • the present invention can be directly applied or easily adapted to concurrently control two or more processing stations, such as steam profilers or other processing stations used to make or operate on webs of paper or other materials.
  • the web 116 may pass through a series of calenders 126, through sensor means comprising a machine cross direction (CD) web measurement platform 128 and a sensor 130 such as a nucleonic or other appropriate sensor supported by and moved along the platform 128, and is wound onto a web accumulating reel 132.
  • the sensor 130 generates a profile signal representative of one or more characteristics of the web in the machine CD to permit control of the characteristics to thereby improve the quality of the web 116.
  • the profile signal from the sensor 130 is passed to the two or more headboxes of a paperboard making machine to control the deposition of pulp slurry by the headboxes.
  • the headbox slices Prior to this time, only one of the headbox slices was controlled or the headbox slices were alternately controlled, one at a time, to control the CD profile of the web.
  • these approaches have resulted in relatively poor control and, in some instances, have even resulted in stability problems.
  • the slice settings can drift in opposite directions as shown by portions 134 of the graphs of Fig. 4 wherein the solid line graph 136 represents the settings of the basis weight actuators 110 of the primary headbox 102 and the dashed line graph 138 represents the settings of the basis weight actuators 110 of the secondary headbox 104.
  • the drifting of the slice settings illustrated in Fig. 4 results in existing uneven pulp slurry distributions not being corrected by the adjustments of the headbox slices and in fact the uneven distributions can be aggravated.
  • a multiple headbox paper making machine or multi-former machine can have either a single wire section as shown in Fig. 1 or can have multiple wires.
  • the first headbox such as the primary headbox 102
  • the secondary headbox(es) such as the headbox 104, has a shorter wire length and delivers relatively lower percentage(s) of slurry or stock to the web 116.
  • the dryline distance on the wire from the primary headbox is noticeably longer than the dryline distances on the wire from the one or more secondary headboxes. This observation is particularly true for the single wire configuration shown in Fig. 1.
  • Frequency and spatial frequency will be used interchangeably herein to refer to frequency in space laterally across the web or in the machine CD direction and will be understood to be in units of cycles per unit length across the web.
  • spatial frequency can be in units of a cycle or wavelength per a number of actuator widths as will be well known to those skilled in the art of paper making.
  • the drainage performance after the secondary headbox or headboxes is substantially lower because the nearly formed base sheet is already on the wire when the secondary headbox or headboxes distribute slurry on the wire. Due to this physical behavior, the moisture profile variation is mainly contributed by the secondary headbox(es), especially the higher-spatial- frequency/shorter-wavelength profile variations, also called moisture streaks, which primarily reflect the profile disturbance from the secondary headbox(es) . Due to the small percentage weight contribution from the secondary headbox(es) such that smaller amounts of slurry need to be dispersed and a shorter time is allowed for the slurry propagation, and their shorter dryline distances, the CD response width from an actuator on a secondary headbox is always narrower than the similar response from the primary headbox.
  • the machine CD profile control in accordance with the present invention as applied to a dual headbox paper making machine such as the machine 100 is illustrated in the block diagram of Fig. 2.
  • the crux of the present invention is the recognition that the contributions of the individual processing stations of a web processing machine or the slurry distributions by the headboxes 102, 104 of the machine 100 can be characterized by different spatial frequencies or groups of spatial frequencies which correspond to the individual stations. Accordingly, the profile signal generated by the sensor 130 is divided into two or more subprofile signals by combining the frequency components of the profile signal which correspond to the individual stations.
  • the resulting subprofile signals are applied to the corresponding stations to control their operation in accordance with existing control arrangements.
  • the resulting subprofile signals can be applied to headbox controller means comprising the headbox controls 140A, 140B of the headboxes 102, 104 which are then controlled by existing algorithms in response to the subprofile signals.
  • the headboxes 102, 104 are controlled in accordance with a control model presented in a paper entitled "Adaptive Profile Control for Sheetmaking Processes" by S.-C. Chen, R. M. Snyder and R. G. Wilhelm, Jr. which was presented at the 6th International
  • the measured profile signal from the sensor 130 is applied to profile divider means comprising a profile divider circuit 142 for separating the profile signal into at least two subprofile signals corresponding to the at least two processing stations such as the two headboxes 102, 104 of the machine 100.
  • the subprofile signals are passed to two or more process actuators such as the wide response actuator 144 and the narrow response actuator 146 which would correspond to the headbox controls 140A and 140B of the machine 100. If more than two processing stations are to be controlled in accordance with the present invention, the profile signal is divided into the corresponding number of subprofile signals which are then applied to the appropriate actuators represented generally in Fig. 2 by one additional narrow response actuator 148 and additional signal lines 150.
  • the profile divider circuit 142 preferably comprises a digital computer for processing the profile signal into the subprofile signals based on the spatial frequencies of components of the profile signal.
  • the digital computer is programmed to filter or otherwise combine the frequency components of the profile signal below a defined frequency to generate a subprofile signal for the primary headbox 102, and to filter or otherwise combine the frequency components above the defined frequency to generate a subprofile signal for the secondary headbox 104.
  • the defined frequency is that which corresponds to a wavelength of approximately 7 to 9 actuator widths.
  • n represent a profile with n points that describes a process property such as cross direction (CD) basis weight or moisture of a paper web being produced.
  • the value of y(k) at each point across the web is the actual measurement of the corresponding profile at the kth CD location.
  • the long wave length component or subprofile of the profile is calculated using the following equation:
  • a Q , a,, a_, ..., a f generally is a decreasing sequence.
  • the decreasing or decremental rate is related to the wavelength contents preserved in y (k) .
  • the high decremental rate produces shorter wavelength contents in y (k) .
  • the short wave length component or subprofile of the profile is calculated by subtracting y (k) from y(k) as:
  • the digital computer can be programmed to take the Fourier transform of the profile signal, to combine selected components of the Fourier transform of the profile signal to obtain a subprofile Fourier transform for the primary headbox 102, to combine the remaining components of the Fourier transform to obtain a subprofile Fourier transform for the secondary headbox 104, and to take the inverse Fourier transforms of the subprofile Fourier transforms for the primary and secondary headboxes 102, 104 to obtain corresponding subprofile signals.
  • the digital computer can be programmed to take the Fourier transform of the profile signal, to combine selected components of the Fourier transform of the profile signal to obtain subprofile Fourier transforms, the selected components being selected to correspond to the total number of processing stations such as headboxes, and to take the inverse Fourier transforms of the subprofile Fourier transforms to obtain the appropriate subprofile signals for control of the processing stations or headboxes. If the processing station cannot completely correct web profile errors represented by the subprofile signal, a residual profile signal can be generated by a process model circuit 152 and fed forward to subsequent process controllers. This feed forward process can be carried throughout up to all the processing stations, as is suggested in Fig. 2, if the preceding processing stations are unable to make the require corrections.
  • solid line graph 160 is a typical measured CD basis weight profile
  • dashed line graph 162 is a typical measured CD moisture profile.
  • the profile signals are divided into two or more components or subprofiles as shown by graphs 160A, 160B and 162A, 162B in Figs. 6 and 7.
  • the division of a profile signal into two or more corresponding subprofile signals is tuneable or selectable according to the particular process to be controlled and even according to the particular machine to be controlled.
  • the present invention fully utilizes the controllability of multiple processing station machines such as multiple headbox paperboard making machines since control is concurrently applied to all processing stations. Such concurrent or simultaneous control also produces rapid response times for the characteristic being controlled. Since the subprofile signals are generated to correspond to the nature of the variations for each of the processing stations, machine control made in response to the subprofile signals properly coordinates operation of the processing stations for accurate and effective overall machine control. By splitting the profile signal into subprofile signals in accordance with the present invention, the effects of individual processing stations are effectively identified and can be separately controlled to prevent cross coupling between and among the stations.
  • each headbox is controlled independently of the characteristics or subprofiles of the other headboxes such that it is unlikely that the slice shapes of the different headboxes will drift in the opposite directions interactively as shown in Fig. 4.
  • the secondary headbox(es) mainly contributes the short wavelength variations.
  • the slice shape on the secondary headbox(es) will not deviate too far from a flat shape and the chance of having an uneven slurry coverage from the secondary headbox(es) is thus significantly reduced.
  • the moisture streaks as previously noted are highly correlated with the high spatial frequency or short wavelength component of weight profile variations.
  • the secondary headbox(es) is controlled in accordance with the present invention to control the shorter wavelength component of the basis weight profile more effectively, the moisture streaks are also reduced.

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Abstract

A method and apparatus are disclosed wherein a web of material (116), such as paper, being manufactured or processed is monitored to generate a profile signal which is separated into a number of subprofile signals corresponding to a number of processing stations to be controlled. The contributions of the individual processing stations, such as headboxes (102, 104) for the manufacture of paper, to various cross direction (CD) profile characteristics of the web of material has been recognized as being spatial frequency dependent. Accordingly, the profile signal generated by monitoring the web of material is divided (142) into two or more subprofile signals corresponding to the processing stations based on the CD spatial frequencies characteristic of the operations performed by the stations. The subprofile signals are then applied to the processing stations (102, 104) to control them to maintain one or more desired CD profile characteristics. The division of the profile signal into subprofile signals can be performed by filtering, Fourier transforms or otherwise. Preferably, profile signal division is performed by a digital processor.

Description

CROSS DIRECTION PROFILE CONTROL FOR MULTIPLE STATION WEB FORMING MACHINE
Background of the Invention The present invention relates generally to multiple station web forming machines and, more particularly, to a method and apparatus for concurrently controlling the processing stations of such machines. The present invention is particularly applicable to multiple headbox paper making machines to concurrently control the headboxes for more even application of pulp slurry to wire screens of the paper making machines to thereby prevent coverage problems and improve the quality of paper produced. Accordingly, the invention will be described with reference to a multiple headbox paper making machine.
Paperboard making machines commonly employ multiple headboxes to distribute pulp slurry onto an endless wire screen, normally referred to only as a "wire", which then, passes through presses and over dryers to calenders and reels of the machine. For these machines, cross direction (CD) weight and moisture variations or profiles, i. e. weight and moisture variations laterally across the paper webs being made by the machines, are the composite result of the slices of pulp slurry which are deposited by the headboxes. The slices are defined by the shape of the "slice" or elongated slurry depositing opening of each headbox. While the percent contribution of the total weight from each headbox can be approximately estimated from the amount of pulp slurry delivered by the headbox, the profile contribution from each headbox is very difficult to identify.
Existing approaches to the control of CD profiles are either to control only one headbox slice or to alternately control the headbox slices one at a time. Unfortunately, these approaches have resulted in relatively poor control and, in some instances, have even resulted in stability problems. For example, when a single headbox slice is controlled or the headbox slices are controlled one-by-one, the slice settings can drift in opposite directions such that existing uneven pulp slurry distributions are not corrected by the adjustments of the headbox slices and in fact can be aggravated.
There is thus a need for an improved headbox control arrangement for use in multiple headbox paper making machines to concurrently control the slices of the multiple headboxes such that the headboxes work together to ensure even pulp slurry distributions. Preferably, the control arrangement would equally apply or be easily adapted to control multiple stage machines having at least two processing stations for making a web of material or performing an operation on a web of material, for example to control the moisture profile by concurrently controlling multiple CD moisture actuators.
Summary of the Invention.
This need is met by the method and apparatus of the present invention wherein a web of material, such as paper, being manufactured or processed is monitored to generate a profile signal which in turn is separated into a number of subprofile signals corresponding to the number of processing stations to be controlled. It has been recognized in the present invention that the contributions of the individual processing stations, such as headbox slices for the manufacture of paper, to various CD profile characteristics of the resulting web of material are frequency dependent wherein frequency is to be understood as being frequency in space laterally across the web or in the machine CD direction referred to herein generally as frequency or spatial frequency. Accordingly, the profile signal representative of the web of material can be divided into two or more subprofile signals corresponding to the processing stations based on the frequencies representative of the stations. The subprofile signals are then applied to the processing stations to control them to maintain one or more desired CD profile characteristics.
According to one aspect of the present invention, a method for controlling a paper making machine having at least two headboxes for applying pulp slurry to a wire of the machine to form a web of paper comprises the steps of: monitoring the web of paper; generating a profile signal representative of one or more characteristics of the web of paper in the machine cross direction; separating the profile signal into at least two subprofile signals corresponding to the at least two headboxes of the machine; and, applying the subprofile signals to corresponding headbox controllers to concurrently control the headboxes whereby slurry is more evenly applied to the wire to prevent coverage problems and improve the quality of the web of paper.
According to another aspect of the present invention, a method for controlling a multiple stage machine having at least two processing stations for making a web of material or performing an operation on a web of material produced by the machine comprises the steps of: monitoring the web of material; generating a profile signal representative of one or more characteristics of the web of material in the machine cross direction; separating the profile signal into at least two subprofile signals corresponding to the at least two processing stations of the machine; and, applying the subprofile signals to corresponding processing station controllers to concurrently control the processing stations whereby the web of material is more evenly made or processed to improve the quality of the web of material. _ z The step of separating the profile signal into at least two subprofile signals corresponding to the at least two processing stations or headboxes of a machine is preferably performed based on spatial frequencies of components of the profile signal. For example, where the machine has a primary processing station and a secondary processing station, the step of separating the profile signal into at least two subprofile signals may comprise the steps of: combining frequency components of the profile signal below a defined frequency to generate a subprofile signal for the primary processing station; and, combining frequency components above the defined frequency to generate a subprofile signal for the secondary processing station. For controlling a paper making machine having a primary headbox and a secondary headbox, the defined frequency may be that which corresponds to a wavelength of approximately 7 to 9 actuator widths.
Alternately, the step of separating the profile signal into at least two subprofile signals corresponding to the at least two processing stations of the machine may comprise the steps of: taking the Fourier transform of the profile signal; combining selected components of the Fourier transform of the profile signal to obtain subprofile Fourier transforms, the selected components being selected to correspond to the at least two processing stations; and, taking the inverse Fourier transforms of the subprofile Fourier transforms to obtain the subprofile signals.
In instances where the correction to be performed by subprofile signals cannot be completely performed by the corresponding processing stations, the method may further comprise the steps of: determining what portions of the subprofile signals can be effectively utilized by their corresponding processing station controllers; generating residual subprofile signals by separating the utilized portions of the subprofile signals determined in the preceding step from the corresponding subprofile signals; and, feeding the residual subprofile signals forward for combination with subprofile signals for subsequent processing station controllers. This "feed forward" control arrangement provides still more accurate control of the web profiles.
According to yet another aspect of the present invention, a system for controlling a paper making machine having at least two headboxes for applying pulp slurry to a wire of the machine to form a web of paper comprises sensor means for monitoring the web of paper and generating a profile signal representative of one or more characteristics of the web of paper in the machine cross direction. Profile divider means separate the profile signal into at least two subprofile signals corresponding to the at least two headboxes of the machine. Headbox controller means are responsive to the subprofile signals for concurrently controlling the headboxes to cooperatively apply the slurry more evenly to the wire thereby reducing coverage problems and improving the quality of the web of paper.
According to still another aspect of the present invention, a system for controlling a multiple stage machine having at least two processing stations for making or performing an operation on a web of material produced by the machine comprises sensor means for monitoring the web of material and generating a profile signal representative of one or more characteristics of the web of material in the machine cross direction. Profile divider means separate the profile signal into at least two subprofile signals corresponding to the at least two processing stations of the machine. Processing station controller means are responsive to the subprofile signals for concurrently controlling the processing stations such that the web of material is more evenly made or processed to improve the quality of the web of material. The system for controlling a multiple stage machine having at least two processing stations or headboxes for paper manufacture preferably comprises a digital computer for processing the profile signal into the subprofile signals based on the spatial frequencies of components of the profile signal. When the system has a primary processing station and a secondary processing station, the profile divider means may comprise a digital computer programmed to combine the frequency components of the profile signal below a defined frequency to generate a subprofile signal for the primary processing station, and to combine the frequency components above the defined frequency to generate a subprofile signal for the secondary processing station. For controlling a paper making machine having a primary headbox and a secondary headbox, the defined frequency may be that which corresponds to a wavelength of approximately 7 to 9 actuator widths.
Alternately, the profile divider means may comprise a digital computer programmed to take the Fourier transform of the profile signal, to combine selected components of the Fourier transform of the profile signal to obtain a subprofile Fourier transform for the primary processing station, to combine the remaining components of the Fourier transform to obtain a subprofile Fourier transform for the secondary processing station, and to take the inverse Fourier transforms of the subprofile Fourier transforms for the primary and secondary processing stations to obtain corresponding subprofile signals. More generally, the profile divider means may comprise a digital computer programmed to take the Fourier transform of the profile signal, to combine selected components of the Fourier transform of the profile signal to obtain subprofile Fourier transforms, the selected components being selected to correspond to the at least two processing stations, and to take the inverse Fourier transforms of the subprofile Fourier transforms to obtain the subprofile signals.
It is an object of the present invention to provide an improved method and apparatus for concurrently controlling multiple web processing stations such as headboxes, steam profilers, water sprays and the like used to make and process paper webs; to provide an improved method and apparatus for concurrently controlling multiple web processing stations by monitoring the web to generate a profile signal which is separated into a number of subprofile signals corresponding to the number of processing stations to be controlled; to provide an improved method and apparatus for concurrently controlling multiple web processing stations by generating a web profile signal which is digitally processed to define a number of spatial frequency dependent subprofile signals corresponding to the number of processing stations to be controlled; and, to provide an improved method and apparatus for concurrently controlling multiple web processing stations by generating a web profile signal which is Fourier transformed and selectively divided to define a number of spatial frequency dependent subprofile signals corresponding to the number of processing stations to be controlled.
Other objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.
Brief Description of the Drawings Fig. 1 is a schematic side view of a dual headbox paper making machine for which the present invention is particularly applicable;
Fig. 2 is a block diagram of a system in accordance with the present invention for concurrent control of web processing stations;_
Figs. 3A, 3B and 3C are perspective plan views of sections of a paper making machine illustrating a headbox, a steam profiler and a web sensor platform, respectively, and also various web conveying rollers, wires and reels;
Fig. 4 is a graph illustrating potential problems which can result if multiple headboxes of a paper making machine are not properly coordinated;
Fig. 5 is a graph illustrating basis weight and moisture profiles generated by monitoring a web of paper;
Figs. 6 and 7 are graphs illustrating subprofiles generated in accordance with the present invention from the profiles of Fig. 5.
Detailed Description of the Invention While the present invention is generally applicable to multiple station machines for making or processing webs of material, it is particularly applicable to paper making machines and accordingly will be described herein with reference to a multiple headbox paperboard making machine. Fig. 1 is a schematic side view of a dual headbox paper making machine 100 including a primary headbox 102 and a secondary headbox 104. The primary headbox 102 is shown in perspective in the machine of Fig. 3A which illustrates in more detail, although still schematically, the primary headbox 102.
A headbox slice 106 is defined by a slice lip 108 which is controlled along its length by basis weight actuators 110. Pulp slurry is conveyed to the primary headbox 102 via a stock pipe 112 and to the secondary headbox 104 such that slurry can be applied to a wire 114 to form a paper web 116. As the web 116 passes along the wire 114 and other parts of the paper making machine 100, it is processed by passing over foils 118, deflectors 120 and suction boxes 122.
The web 116 may also be acted upon by one or more processing stations along the length of the machine 100, for example by a steam profiler 124 schematically shown in Fig. 3B. In addition to concurrent control of two or more headboxes of a paper making machine, such as the headboxes 102 and 104, the present invention can be directly applied or easily adapted to concurrently control two or more processing stations, such as steam profilers or other processing stations used to make or operate on webs of paper or other materials.
Ultimately, the web 116 may pass through a series of calenders 126, through sensor means comprising a machine cross direction (CD) web measurement platform 128 and a sensor 130 such as a nucleonic or other appropriate sensor supported by and moved along the platform 128, and is wound onto a web accumulating reel 132. The sensor 130 generates a profile signal representative of one or more characteristics of the web in the machine CD to permit control of the characteristics to thereby improve the quality of the web 116.
Normally, the profile signal from the sensor 130 is passed to the two or more headboxes of a paperboard making machine to control the deposition of pulp slurry by the headboxes. Prior to this time, only one of the headbox slices was controlled or the headbox slices were alternately controlled, one at a time, to control the CD profile of the web. Unfortunately, these approaches have resulted in relatively poor control and, in some instances, have even resulted in stability problems.
For example, when a single headbox slice is controlled or the headbox slices are controlled one-by-one, the slice settings can drift in opposite directions as shown by portions 134 of the graphs of Fig. 4 wherein the solid line graph 136 represents the settings of the basis weight actuators 110 of the primary headbox 102 and the dashed line graph 138 represents the settings of the basis weight actuators 110 of the secondary headbox 104. The drifting of the slice settings illustrated in Fig. 4 results in existing uneven pulp slurry distributions not being corrected by the adjustments of the headbox slices and in fact the uneven distributions can be aggravated. A multiple headbox paper making machine or multi-former machine can have either a single wire section as shown in Fig. 1 or can have multiple wires. Generally, the first headbox, such as the primary headbox 102, delivers the backliner or the bottom layer of the web 116, has a longer wire or wire portion and contributes a higher percentage of the total basis weight. The secondary headbox(es), such as the headbox 104, has a shorter wire length and delivers relatively lower percentage(s) of slurry or stock to the web 116. The dryline distance on the wire from the primary headbox is noticeably longer than the dryline distances on the wire from the one or more secondary headboxes. This observation is particularly true for the single wire configuration shown in Fig. 1.
In the present invention it has been recognized that because of the shorter dryline distances for the secondary or top headboxes, the slurry coming from the secondary headboxes tends to be less evenly distributed and is more strongly linked to the higher spatial frequencies or shorter wavelength variations in the profile signal. Frequency and spatial frequency will be used interchangeably herein to refer to frequency in space laterally across the web or in the machine CD direction and will be understood to be in units of cycles per unit length across the web. For example, in the paper making arts, spatial frequency can be in units of a cycle or wavelength per a number of actuator widths as will be well known to those skilled in the art of paper making.
The drainage performance after the secondary headbox or headboxes is substantially lower because the nearly formed base sheet is already on the wire when the secondary headbox or headboxes distribute slurry on the wire. Due to this physical behavior, the moisture profile variation is mainly contributed by the secondary headbox(es), especially the higher-spatial- frequency/shorter-wavelength profile variations, also called moisture streaks, which primarily reflect the profile disturbance from the secondary headbox(es) . Due to the small percentage weight contribution from the secondary headbox(es) such that smaller amounts of slurry need to be dispersed and a shorter time is allowed for the slurry propagation, and their shorter dryline distances, the CD response width from an actuator on a secondary headbox is always narrower than the similar response from the primary headbox. The machine CD profile control in accordance with the present invention as applied to a dual headbox paper making machine such as the machine 100 is illustrated in the block diagram of Fig. 2. The crux of the present invention is the recognition that the contributions of the individual processing stations of a web processing machine or the slurry distributions by the headboxes 102, 104 of the machine 100 can be characterized by different spatial frequencies or groups of spatial frequencies which correspond to the individual stations. Accordingly, the profile signal generated by the sensor 130 is divided into two or more subprofile signals by combining the frequency components of the profile signal which correspond to the individual stations.
The resulting subprofile signals are applied to the corresponding stations to control their operation in accordance with existing control arrangements. For example, the resulting subprofile signals can be applied to headbox controller means comprising the headbox controls 140A, 140B of the headboxes 102, 104 which are then controlled by existing algorithms in response to the subprofile signals. Preferably, the headboxes 102, 104 are controlled in accordance with a control model presented in a paper entitled "Adaptive Profile Control for Sheetmaking Processes" by S.-C. Chen, R. M. Snyder and R. G. Wilhelm, Jr. which was presented at the 6th International
IFAC/IFIP/IMEKO Conference on Instrumentation and Automation in the Paper, Rubber, Plastics and Polymerization Industries (PRP-6), held on October 27-29, 1986 in Akron, Ohio, which paper is incorporated herein by reference.
As shown in Fig. 2, the measured profile signal from the sensor 130 is applied to profile divider means comprising a profile divider circuit 142 for separating the profile signal into at least two subprofile signals corresponding to the at least two processing stations such as the two headboxes 102, 104 of the machine 100. The subprofile signals are passed to two or more process actuators such as the wide response actuator 144 and the narrow response actuator 146 which would correspond to the headbox controls 140A and 140B of the machine 100. If more than two processing stations are to be controlled in accordance with the present invention, the profile signal is divided into the corresponding number of subprofile signals which are then applied to the appropriate actuators represented generally in Fig. 2 by one additional narrow response actuator 148 and additional signal lines 150. The profile divider circuit 142 preferably comprises a digital computer for processing the profile signal into the subprofile signals based on the spatial frequencies of components of the profile signal. In the case of the dual headbox paper making machine 100, the digital computer is programmed to filter or otherwise combine the frequency components of the profile signal below a defined frequency to generate a subprofile signal for the primary headbox 102, and to filter or otherwise combine the frequency components above the defined frequency to generate a subprofile signal for the secondary headbox 104. In one working embodiment of the present invention, the defined frequency is that which corresponds to a wavelength of approximately 7 to 9 actuator widths. One computer implementation of the present invention will now be described. Let y(k) with k=l,2,3, ... ,n represent a profile with n points that describes a process property such as cross direction (CD) basis weight or moisture of a paper web being produced. The value of y(k) at each point across the web is the actual measurement of the corresponding profile at the kth CD location. The long wave length component or subprofile of the profile is calculated using the following equation:
y1(k)=a0y(k)+a1[y(k-l)+y(k+l)]+a2[y(k-2)+y(k+2)]+... ...af[y(k-f)+y(k+f)] for all k=l,2,3, ... ,n
where the coefficients |a_J, jaJ, p , ... , ja are adjusted according to the characteristics of a process such as machine speed, production grade and the like. aQ, a,, a_, ..., af generally is a decreasing sequence. The decreasing or decremental rate is related to the wavelength contents preserved in y (k) . The high decremental rate produces shorter wavelength contents in y (k) . The short wave length component or subprofile of the profile is calculated by subtracting y (k) from y(k) as:
yS(k)=y(k)-y1(k) for all k=l,2,3, ... ,n
Alternately, the digital computer can be programmed to take the Fourier transform of the profile signal, to combine selected components of the Fourier transform of the profile signal to obtain a subprofile Fourier transform for the primary headbox 102, to combine the remaining components of the Fourier transform to obtain a subprofile Fourier transform for the secondary headbox 104, and to take the inverse Fourier transforms of the subprofile Fourier transforms for the primary and secondary headboxes 102, 104 to obtain corresponding subprofile signals. In accordance with broad aspects of the present invention, the digital computer can be programmed to take the Fourier transform of the profile signal, to combine selected components of the Fourier transform of the profile signal to obtain subprofile Fourier transforms, the selected components being selected to correspond to the total number of processing stations such as headboxes, and to take the inverse Fourier transforms of the subprofile Fourier transforms to obtain the appropriate subprofile signals for control of the processing stations or headboxes. If the processing station cannot completely correct web profile errors represented by the subprofile signal, a residual profile signal can be generated by a process model circuit 152 and fed forward to subsequent process controllers. This feed forward process can be carried throughout up to all the processing stations, as is suggested in Fig. 2, if the preceding processing stations are unable to make the require corrections.
Operation of the present invention is illustrated graphically in Fig. 5, 6 and 7. In Fig. 5, solid line graph 160 is a typical measured CD basis weight profile and dashed line graph 162 is a typical measured CD moisture profile. As previously described, when profile signals represented by the graphs 160, 162 are applied to the profile divider circuit 142, the profile signals are divided into two or more components or subprofiles as shown by graphs 160A, 160B and 162A, 162B in Figs. 6 and 7. The division of a profile signal into two or more corresponding subprofile signals is tuneable or selectable according to the particular process to be controlled and even according to the particular machine to be controlled.
The present invention fully utilizes the controllability of multiple processing station machines such as multiple headbox paperboard making machines since control is concurrently applied to all processing stations. Such concurrent or simultaneous control also produces rapid response times for the characteristic being controlled. Since the subprofile signals are generated to correspond to the nature of the variations for each of the processing stations, machine control made in response to the subprofile signals properly coordinates operation of the processing stations for accurate and effective overall machine control. By splitting the profile signal into subprofile signals in accordance with the present invention, the effects of individual processing stations are effectively identified and can be separately controlled to prevent cross coupling between and among the stations. As applied to a multiple headbox paper making machine this means each headbox is controlled independently of the characteristics or subprofiles of the other headboxes such that it is unlikely that the slice shapes of the different headboxes will drift in the opposite directions interactively as shown in Fig. 4.
The secondary headbox(es) mainly contributes the short wavelength variations. By controlling the secondary headbox(es) from a corresponding high spatial frequency or short wavelength subprofile signal, the slice shape on the secondary headbox(es) will not deviate too far from a flat shape and the chance of having an uneven slurry coverage from the secondary headbox(es) is thus significantly reduced. The moisture streaks as previously noted are highly correlated with the high spatial frequency or short wavelength component of weight profile variations. Thus, when the secondary headbox(es) is controlled in accordance with the present invention to control the shorter wavelength component of the basis weight profile more effectively, the moisture streaks are also reduced.
Having thus described the cross direction profile control for a multiple station web forming machine of the present invention in detail and by reference to preferred embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims. What is claimed is:

Claims

1. A method for controlling a paper making machine having at least two headboxes for applying slurry to a wire of the machine to form a web of paper, the method comprising the steps of: monitoring the web of paper; generating a profile signal representative of one or more characteristics of the web of paper in the machine cross direction; separating the profile signal into at least two subprofile signals corresponding to the at least two headboxes of the machine; and applying the subprofile signals to corresponding headbox controllers to concurrently control the headboxes whereby slurry is more evenly applied to the wire to reduce coverage problems and improve the quality of the web of paper.
2. A method for controlling a paper making machine having at least two headboxes as claimed in claim 1 further comprising the steps of: determining what portions of the subprofile signals can be effectively utilized by their corresponding headbox controllers; generating residual subprofile signals by separating the utilized portions of the subprofile signals determined in the preceding step from the corresponding subprofile signals; and feeding the residual subprofile signals forward for combination with subprofile signals for subsequent headbox controllers.
3. A method for controlling a paper making machine having at least two headboxes as claimed in claim 1 wherein the step of separating the profile signal into at least two subprofile signals corresponding to the at least two i 5 headboxes of the machine is performed based on the frequencies of components of the profile signal.
4. A method for controlling a paper making machine having at least two headboxes as claimed in claim 3 wherein the machine has a primary headbox and a secondary headbox and the step of separating the profile signal into at least
5 two subprofile signals comprises the steps of: combining the frequency components of the profile signal below a defined frequency to generate a subprofile signal for the primary headbox; and combining the frequency components above the 10 defined frequency to generate a subprofile signal for the secondary headbox.
5. A method for controlling a paper making machine having at a primary headbox and a secondary headbox as claimed in claim 4 wherein said defined frequency is that which corresponds to a wavelength of approximately 7 to 9 5 actuator widths.
6. A method for controlling a paper making machine having at least two headboxes as claimed in claim 1 wherein the step of separating the profile signal into at least two subprofile signals corresponding to the at least two headboxes of the machine comprises the steps of: taking the Fourier transform of the profile signal; combining selected components of the Fourier transform of the profile signal to obtain subprofile Fourier transforms, said selected components being selected to correspond to the at least two headboxes; and taking the inverse Fourier transforms of the subprofile Fourier transforms to obtain the subprofile signals.
7. A method for controlling a multiple stage machine having at least two processing stations for making a web of material or performing an operation on a web of material produced by the machine, ±he method comprising the steps of: monitoring the web of material; generating a profile signal representative of one or more characteristics of the web of material in the machine cross direction; separating the profile signal into at least two subprofile signals corresponding to the at least two processing stations of the machine; and applying the subprofile signals to corresponding processing station controllers to concurrently control the processing stations whereby the web of material is more evenly made or processed to improve the quality of the web of material.
8. A method for controlling a multiple stage machine having at least two processing stations as claimed in claim
Λ 7 wherein the step of separating the profile signal into at least two subprofile signals corresponding to the at least j 5 two processing stations of the machine is performed based on frequencies of components of the profile signal.
9. A method for controlling a multiple stage machine having at least two processing stations as claimed in claim 8 wherein the machine has a primary processing station and a secondary processing station, and the step of separating 5 the profile signal into at least two subprofile signals comprises the steps of: combining frequency components of the profile signal below a defined frequency to generate a subprofile signal for the primary processing station; and 10 combining frequency components above the defined frequency to generate a subprofile signal for the secondary processing station.
10. A method for controlling a multiple stage machine having at least two processing stations as claimed in claim 7 wherein the step of separating the profile signal into at least two subprofile signals corresponding to the at least 5 two processing stations of the machine comprises the steps of: taking the Fourier transform of the profile signal; combining selected components of the Fourier transform of the profile signal to obtain subprofile 10 Fourier transforms, said selected components being selected to correspond to the at least two processing stations; and taking the inverse Fourier transforms of the subprofile Fourier transforms to obtain the subprofile signals.
11. A method for controlling a multiple stage machine having at least two processing stations as claimed in claim 7 further comprising the steps of: determining what portions of the subprofile signals can be effectively utilized by their corresponding processing station controllers; generating residual subprofile signals by separating the utilized portions of the subprofile signals determined in the preceding step from the corresponding subprofile signals; and feeding the residual subprofile signals forward for combination with subprofile signals for subsequent processing station controllers.
12. A system for controlling a paper making machine having at least two headboxes for applying slurry to a wire of the machine to form a web of paper, the system comprising: sensor means for monitoring the web of paper and generating a profile signal representative of one or more characteristics of the web of paper in the machine cross direction; profile divider means for separating the profile signal into at least two subprofile signals corresponding to the at least two headboxes of the machine; and headbox controller means responsive to the subprofile signals for concurrently controlling the headboxes to cooperatively apply the slurry more evenly to the wire thereby reducing coverage problems and improving the quality of the web of paper.
13. A system for controlling a paper making machine having at least two headboxes as claimed in claim 12
* wherein said profile divider means comprises a digital computer for processing the profile signal into the
4 5 subprofile signals based on the frequencies of components of the profile signal.
14. A system for controlling a paper making machine having at least two headboxes as claimed in claim 12 wherein the machine has a primary headbox and a secondary headbox, and the profile divider means comprises a digital
5 computer programmed to combine the frequency components of the profile signal below a defined frequency to generate a subprofile signal for the primary headbox, and to combine the frequency components above the defined frequency to generate a subprofile signal for the secondary headbox.
15. - A system for controlling"'a paper making machine- having a primary headbox and a secondar headbox as claimed in claim 14 wherein said defined frequency is that which corresponds to a wavelength of approximately 7 to 9
5 actuator widths.
16. A system for controlling a paper making machine having at least two headboxes as claimed in claim 12 wherein the machine has a primary headbox and a secondary headbox, and the profile divider means comprises a digital
5 computer programmed to take the Fourier transform of the profile signal, to combine selected components of the Fourier transform of the profile signal to obtain a subprofile Fourier transform for the primary headbox, to combine the remaining components of the Fourier transform to obtain a subprofile Fourier transform for the secondary headbox, and to take the inverse Fourier transforms of the subprofile Fourier transforms for the primary and secondary headboxes to obtain corresponding subprofile signals.
17. A system for controlling a paper making machine having at least two headboxes as claimed in claim 12 wherein the profile divider means comprises a digital computer programmed to take the Fourier transform of the profile signal, to combine selected components of the Fourier transform of the profile signal to obtain subprofile Fourier transforms, the selected components being selected to correspond to the at least two headboxes, and to take the inverse Fourier transforms of the subprofile Fourier transforms to obtain the subprofile signals.
18. A system for controlling a multiple stage machine having at least two processing stations for making or performing an operation, on a web of material produced by the machine, the system comprising: sensor means for monitoring the web of material and generating a profile signal representative of one or more characteristics of the web of material in the machine cross direction; profile divider means for separating the profile signal into at least two subprofile signals corresponding to the at least two processing stations of the machine; and processing station controller means responsive to the subprofile signals for concurrently controlling the processing stations such that the web of material is more evenly made or processed to improve the quality of the web of material.
19. A system for controlling a multiple stage machine having at least two processing stations as claimed in claim 18 wherein said profile divider means comprises a digital computer for processing the profile signal into the subprofile signals based on the frequencies of components of the profile signal.
20. A system for controlling a multiple stage machine having at least two processing stations as claimed in claim 18 wherein the machine has a primary processing station and a secondary processing station, and the profile divider means comprises a digital computer programmed to combine the frequency components of the profile signal below a defined frequency to generate a subprofile signal for the primary processing station, and to combine the frequency components above the defined frequency to generate a subprofile signal for the secondary processing station.
21. A system for controlling a multiple stage machine having at least two processing stations as claimed in claim 18 wherein the machine has a primary processing station and a secondary processing station, and the profile divider means comprises a digital computer programmed to take the Fourier transform of the profile signal, to combine selected components of the Fourier transform of the profile signal to obtain a subprofile Fourier transform for the primary processing station, to combine the remaining components of the Fourier transform to obtain a subprofile Fourier transform for the secondary processing station, and to take the inverse Fourier transforms of the subprofile Fourier transforms for the primary and secondary processing stations to obtain corresponding subprofile signals.
PCT/US1990/004888 1989-10-02 1990-08-29 Cross direction profile control for multiple station web forming machine WO1991005105A1 (en)

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WO1995034810A1 (en) * 1994-06-14 1995-12-21 John Heyer Paper Ltd. Web monitoring for paper machines
DE19727460A1 (en) * 1997-06-27 1999-01-07 Voith Sulzer Papiermasch Gmbh Control and / or regulating system of a machine for producing a fibrous web
DE19733454A1 (en) * 1997-08-02 1999-02-04 Voith Sulzer Papiermasch Gmbh Method and device for detecting and correcting a fiber orientation cross profile change
WO1999064675A1 (en) * 1998-06-12 1999-12-16 Abb Industrial Systems, Inc. Methods for modeling two-dimensional responses of cross-machine direction actuators in sheet-forming processes
WO2003025283A1 (en) * 2001-09-14 2003-03-27 The Research Foundation Of State University Of New York Method and system for characterizing streak defects in web structures
US6953516B2 (en) * 2004-01-16 2005-10-11 Kimberly-Clark Worldwide, Inc. Process for making throughdried tissue by profiling exhaust gas recovery

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Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1995034810A1 (en) * 1994-06-14 1995-12-21 John Heyer Paper Ltd. Web monitoring for paper machines
US5745365A (en) * 1994-06-14 1998-04-28 John Heyer Paper Ltd. Web monitoring for paper machines
DE19727460A1 (en) * 1997-06-27 1999-01-07 Voith Sulzer Papiermasch Gmbh Control and / or regulating system of a machine for producing a fibrous web
US6845281B1 (en) 1997-06-27 2005-01-18 Voith Sulzer Papiermaschinen Gmbh Control and/or regulating system for a machine used for producing a fiber web
DE19733454A1 (en) * 1997-08-02 1999-02-04 Voith Sulzer Papiermasch Gmbh Method and device for detecting and correcting a fiber orientation cross profile change
US6174413B1 (en) 1997-08-02 2001-01-16 Voith Sulzer Papiermaschinen Gmbh Device for detecting and correcting a fiber orientation cross direction profile change
US6524441B2 (en) 1997-08-02 2003-02-25 Voith Sulzer Papiermaschinen Gmbh Process for detecting and correcting a fiber orientation cross direction profile change
WO1999064675A1 (en) * 1998-06-12 1999-12-16 Abb Industrial Systems, Inc. Methods for modeling two-dimensional responses of cross-machine direction actuators in sheet-forming processes
US6233495B1 (en) 1998-06-12 2001-05-15 Abb Automation, Inc. Methods for modeling two-dimensional responses of cross-machine direction actuators in sheet-forming processes
EP1473407A1 (en) * 1998-06-12 2004-11-03 Abb Industrial Systems Inc. Method for modeling two-dimensional responses of cross-machine direction actuators in sheet-forming processes
WO2003025283A1 (en) * 2001-09-14 2003-03-27 The Research Foundation Of State University Of New York Method and system for characterizing streak defects in web structures
US6953516B2 (en) * 2004-01-16 2005-10-11 Kimberly-Clark Worldwide, Inc. Process for making throughdried tissue by profiling exhaust gas recovery

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