WO2022220837A1

WO2022220837A1 - Control of papermaking processes with respect to square point conditions

Info

Publication number: WO2022220837A1
Application number: PCT/US2021/027589
Authority: WO
Inventors: Shih-Chin Chen; Mike BUTYNSKI; Changyuan LIU; Donald STANLEY III; John Schroeder
Original assignee: ABB Schweiz AG
Current assignee: ABB Schweiz AG
Priority date: 2021-04-16
Filing date: 2021-04-16
Publication date: 2022-10-20
Anticipated expiration: 2023-10-16
Also published as: EP4323582A1; FI4323582T3; EP4323582B1; US20240328087A1; CA3215656A1

Abstract

A system, method, and/or apparatus is provided for establishing targets or setpoints of speed parameters for the operation of a papermaking machine that is based on the square point of the paper sheet being produced. The square point of the paper sheet is determined in response to one or more speed parameters and associated one or more fiber distribution parameters for the paper sheet that are measured a plurality of times during the papermaking process and analyzed to determine the square point based on the measurements.

Description

CONTROL OF PAPERMAKING PROCESSES WITH RESPECT TO SQUARE

POINT CONDITIONS

BACKGROUND

[0001] The present disclosure relates in general to papermaking process controls, and, more particularly, to control of papermaking processes with respect to square point conditions to achieve desired paper properties.

[0002] FIG. 1 is a schematic representation of the wet-end (paper forming process) of an exemplary prior art papermaking machine 10. A continuous papermaking process forms paper sheet by pushing pulp slurry through a narrow slice opening of a headbox 12 onto a running drainage wire 14, which may be known as a Fourdrinier wire. The drained water is called “white water”. The drainage wire 14 is positioned over a wire pit 16, which includes a white water silo 18. The output from white water silo 18 is mixed with thick stock supplied through a valve 22, which is then pumped by a fan pump 20 to centrifugal cleaners 24. The output from centrifugal cleaners 24 is supplied to pressure screens 26 upstream of headbox 12. The thick stock flow of pulp furnish comes from a machine chest 28 which holds mixture of various pulps, chemicals, and other raw materials.

[0003] The speed of pulp slurry pushed out from headbox 12 is called a “jet speed” and the drainage wire 14 movement speed is called a “wire speed”. The speed difference between the jet speed and the wire speed is known as a “rush- to-drag speed difference” or simply “R-D speed difference”, and the speed ratio between the jet speed and the wire speed is known as a “jet-to-wire speed ratio” or simply “J/W speed ratio”. Jet speed, wire speed, R-D speed difference, and/or J/W speed ratio together is known as “speed parameters (SDP)”. FIGs. 2A-2D illustrate an exemplary set of speed parameters of a papermaking machine. Speed parameters of a wet-end process affect the fiber distribution, also known as fiber orientation (FO), in the paper sheet being produced. Fiber distribution in the paper sheet impacts paper sheet strength and sheet width. When more fibers distributed along a particular direction, such as a machine direction (MD), the paper sheet is stronger in that direction but weaker in other directions, such as the cross-machine direction (CD). When fibers are uniformly distributed in all directions, which is known as a “square point (SP)”, the paper sheet strength is uniform in all directions and sheet width is wider. Fiber orientation (FO), sheet width, and sheet strength are related to each other. Together, they are called “fiber distribution parameters (FDP)”. FIGs. 2E-2G illustrate an exemplary set of fiber distribution parameters.

[0004] For most paper production, particularly for packaging grades of paper, uniform fiber distribution in all directions, i.e. square point, is highly desirable. Flowever, for some grades of paper, such as paper for high-speed printing, higher fiber distribution in the MD direction may be more desirable. Therefore, papermakers may rely on past experience and/or trial-and-error to setup their papermaking machines to operate at a condition that is either at square point or away from square point, depending on the specifications and/or grades of the paper sheet to be produced. Papermakers’ past experience and/or trial-and- error most likely won’t achieve the desired conditions they want to operate their papermaking machines. As a result, papermakers may use more fiber material than needed to ensure strength requirements are met, or may not accurately setup the machine, incurring unnecessary cost and waste.

[0005] One prior-art approach described in U.S. Patent No. 6,799,083 tries to resolve the above production needs with an online FO measurement to control paper sheet production to a specified FO ratio target. Examples of online FO measurements are provided in U.S. Patent Nos. 5,640,244 and 7,164,145.

There are challenges to this approach. First, online FO measurements are typically noisy, not accurate, not reliable, difficult to calibrate, and hard to correlate to actual sheet strength. Second, while a papermaking process is operating near its square point, online FO measurements often become significantly noisier and more unstable. If the square point is the target to be achieved, online FO measurement is not reliable to be used while the process is operated near the square point. In addition, the majority of papermakers do not even have online FO measurements available for use.

[0006] The control techniques such as described in the Ό83 patent may therefore be of little use, or very expensive, if an online FO measurement is required. The cost and usability of the prior-art techniques may be difficult for papermakers to justify. Therefore, further improvements in the control of papermaking processes are needed.

SUMMARY

[0007] In accordance with the present disclosure, a system, method, and/or apparatus is provided for control of papermaking processes with respect to their square point conditions. The present disclosure identifies and controls production of a paper sheet based on the square point. The square point is determined in response to one or more speed parameters and one or more fiber distribution parameters measured during the papermaking process. The present disclosure provides an automated way to control the fiber distribution with respect to its square point during the papermaking process to provide the desired sheet strength performance. Also presented in accordance with the present disclosure is a computer system that is operable to perform the foregoing.

[0008] In the present disclosure, fiber distribution parameters (FDP) may be provided by a sheet width, FO ratio and/or sheet strength measurements if they are available. The speed parameters (SPD) may be provided by a jet speed, a wire speed, a jet-to-wire (J/W) speed ratio, a rush-to-drag (R-D) speed difference of the papermaking machine, and/or other combinations. When the speed parameters are changed during the papermaking process, the fiber distribution parameters will change as well. FIGs. 3A-3C illustrate an example of this characteristic of papermaking machines.

[0009] By adjusting the speed parameters, such as the jet speed, wire speed, J/W speed ratio, and/or R-D speed difference, the square point can be identified where the sheet strength and the sheet width reach their maximum and/or the FO ratio reaches its minimum. In practice, when a papermaking process changes its running condition, such as different machine speeds or different paper grades, the square point for the paper sheet may appear at different speed parameter settings. The present disclosure provides a technique to find the actual square point under various machine running conditions. After the actual square point is determined, a papermaking machine can be set at the speed parameters that correspond to the square point or be offset away from the square point, depending on the specification of the paper grade being produced. [0010] This summary is provided to introduce a selection of concepts that are further described below in the illustrative embodiments. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter. Further embodiments, forms, objects, features, advantages, aspects, and benefits shall become apparent from the following description and drawings

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The features, aspects, and advantages of the present disclosure will become better understood with regard to the following description, appended claims, and accompanying drawings where:

[0012] FIG. 1 shows a schematic view of a wet-end of an exemplary papermaking machine;

[0013] FIGs. 2A-G illustrate exemplary sets of speed parameters and fiber distribution parameters.

[0014] FIGs. 3A-3C show fiber distribution and sheet width at different papermaking machine conditions;

[0015] FIG. 4 is a block diagram of an execution sequence for square point control according to the present disclosure;

[0016] FIG. 5 is an exemplary flow diagram of a square point determination;

[0017] FIGs. 6A-6C illustrate exemplary J/W speed ratio, sheet width data, and model of sheet width versus J/W speed ratio;

[0018] FIGs. 7A-7D illustrate an exemplary jet speed, wire speed, sheet width data and model of sheet width versus jet speed and wire speed;

[0019] FIGs. 8A-8D illustrate an exemplary jet speed, wire speed, FO ratio data and model of FO ratio versus jet speed and wire speed;

[0020] FIGs. 9A-9D illustrate an exemplary jet speed, wire speed, sheet strength data and model of sheet strength versus jet speed and wire speed;

[0021] FIG. 10 illustrates a square point and associated offsets for setting a J/W speed ratio of a papermaking machine;

[0022] FIG. 11 illustrates a square point and associated offsets for setting jet speed and wire speed of a papermaking machine; and [0023] FIG. 12 is a block diagram illustrating a schematic diagram of a computer control system for square point control.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0024] For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, any alterations and further modifications in the illustrated embodiments, and any further applications of the principles of the invention as illustrated therein as would normally occur to one skilled in the art to which the invention relates are contemplated herein.

[0025] Referring to FIGs. 3A-3C, there is shown headbox 12 with a paper sheet being output therefrom during a papermaking process, along with various parameters that may be measured to determine a square point for the paper sheet, according to the present disclosure. In the present disclosure, online fiber orientation or sheet strength measurements are not required, but the use of the same is not excluded. Measurements of one or more speed parameters (SPD) along with one or more associated measurements of fiber distribution parameters (FDP) are employed in the present disclosure. For example, when the speed parameters, such as jet speed, wire speed, J/W speed ratio, and/or R-D speed difference, are changed on a papermaking machine during the papermaking process, the resulting fiber distribution parameters, such as the sheet width, FO ratio, and/or sheet strength in the paper sheet, will also change.

[0026] In FIG. 3A the jet speed is greater than the wire speed so the papermaking machine is operating at a higher J/W speed ratio, or in a “rush” condition of the R-D speed difference. In this condition, the paper sheet fibers are distributed more in the MD than the CD, and the sheet width 30 shrinks away from its square point, such that the FO ratio is greater than the minimum ratio, the sheet width (also known as trim) is less than the maximum width, and the sheet strength is less than the maximum strength. [0027] In FIG. 3B the jet speed is equal to, or about equal to, the wire speed so the papermaking machine is operating in a “square” condition. In this condition, the paper sheet fibers are distributed equally in all directions. The sheet width 30 expands from FIG. 3A to its square point in FIG. 3B such that the FO ratio is equal to the minimum ratio, the sheet width (trim) is equal to the maximum width, and the sheet strength is at the maximum strength.

[0028] In FIG. 3C the jet speed is less than the wire speed so the papermaking machine is operating at a lower J/W speed ratio and in a “drag” condition of the R-D speed difference. In this condition, the paper sheet fibers are distributed more in the MD than the CD, and the sheet width 30 shrinks away from its square point in FIG. 3B such that the FO ratio is greater than the minimum ratio, the sheet width (trim) is less than the maximum width, and sheet strength is less than the maximum strength.

[0029] Referring to FIG. 4, a control apparatus 100 is shown that is operable to execute a sequence of operations for square point control of the papermaking process by determining the square point 110 and adjusting the speed parameters 108 of the papermaking machine, such as papermaking machine 10 or any other papermaking machine, relative to its square point. During the operation of the papermaking machine, the square point of the paper sheet is identified by control apparatus 100 by adjusting the speed parameters of the papermaking machine and measuring the resulting speed parameters and associated fiber distribution parameters. The measured parameters are analyzed to determine the speed parameters at which the paper sheet width and/or sheet strength reach their maximums, and/or the FO ratio reaches its minimum, i.e. the square point. After the actual square point is determined, the papermaking machine can be set either to run at speed parameters, so that it operates at its actual square point or at an offset from its actual square point depending on the specification of the paper grades to be produced.

[0030] Control apparatus 100 is configured to execute various operations. For example, in the illustrated embodiment these operations include start conditions monitoring at operation block 102, parameter probing execution at operation block 104, square point analysis at operation block 106, and speed parameters setting at operation block 108. These operation blocks may be executed sequentially in a loop.

[0031] In an embodiment, operation block 102 may continuously monitor two sets of “start conditions” to determine whether the next operation block 104 is ready to be started or not. The start conditions may include “AND” conditions and “OR” conditions. In one embodiment, the “AND” set of conditions must be all met before operation block 104 can be executed. For the “OR” set of conditions, only one needs to be met in order to proceed to operation block 104.

[0032] Examples of the “AND” set of conditions at operation block 102 may include, for example: 1) the papermaking machine process being in a stable condition, for example, no change of operating conditions, no grade change transition, no sheet breaks; 2) paperweight and moisture averaged values and variations are at a steady-state, i.e. product measurements are near their set targets, variability is within steady-state boundaries; and 3) the papermaking process is shortly after reel turn-up, i.e. at the beginning of a new reel.

[0033] Examples of the “OR” set of conditions at operation block 102 may include, for example: 1 ) the timer being set for probing execution, for example, when a specified time has elapsed from the initial startup or the reset from the completion of operation 108 from the previous iteration; 2) a specified time has elapsed since the end of the latest change of operating conditions; 3) a specified time has elapsed since the latest ON grade is activated; 4) a specified time has elapsed since the latest manual sheet width change; 5) a specified time duration has elapsed since the sheet width change exceeded a specified limit and stayed there; or 6) execution requested from an operator: Any one of the above “OR” conditions being met together with all the “AND” conditions being met allows execution to proceed from operation block 102 to operation block 104, either automatically or with operator acknowledgement. [0034] In response to the monitoring conditions being satisfied at operation block 102, control apparatus 100 can continue execution at operation block 104 to probe the papermaking process for the square point data, such as by making adjustments to the speed parameters during papermaking process within an allowable range while measuring the resulting speed parameters and associated fiber distribution parameters. The speed parameters such as jet speed, wire speed, J/W speed ratio and/or R-D speed difference are changed by increasing or decreasing by a few small steps in one direction. The speed parameters are then maintained during each step for a duration that is sufficient for the changes of the fiber distribution parameters such as the sheet width, the sheet strength, and/or FO ratio to reach a steady state. When steady state is achieved, the speed parameters and associated fiber distribution parameters are recorded for evaluation. The probing of speed parameters 104 can be performed manually, automatically, or their combination. The probing steps of speed parameters can be executed in a selected order or randomly. For probing of speed parameters, the speed parameters such as jet speed, wire speed, R-D speed different, or J/W speed ratio can be manipulated directly or indirectly through headbox total-head pressure or machine speed. Similarly, R-D speed difference and/or J/W speed ratio can be manipulated either directly or indirectly via changes to the jet speed and/or the wire speed.

[0035] FIG. 5 illustrates an exemplary flow diagram or square point determination 200 providing exemplary sequences of the monitoring of start conditions 202, the execution of probing steps at operation blocks 204 and 206 to obtain data of the speed parameters and fiber distribution parameters for the square point modelling of operation block 208. If the sheet width and/or sheet strength increases and/or the FO ratio decreases after an incremental or decremental step change in speed parameters, fiber distribution parameters are approaching or moving toward its square point. If the sheet width and/or sheet strength decreases and/or the FO ratio increases after an incremental or decremental step change in speed parameters, the fiber distribution is moving away from its square point. [0036] For example, at probing sequence 204, if the fiber distribution is determined to be approaching toward its square point, the speed parameters at which the papermaking machine is operating are stepped in the same direction and the speed parameters and associated fiber distribution parameters are measured continuously at probing sequence 204. If the fiber distribution parameters are determined to be moving away from its square point at probing sequence 204, then the speed parameters are switched to be stepped in the opposite direction at probing sequence 206 and the resulting speed parameters and associated fiber distribution parameters are measured continuously. Once it is determined at probing sequence 204 or probing sequence 206 that fiber distribution approaches and passes its square point, which means the sheet width reaches and passes its maximum width, the sheet strength reaches and passes its maximum strength, or the FO ratio reaches and passes its minimum value the probing sequences 204 or 206 are completed and the collected data are used to model fiber distribution parameters for identifying the square point in block 208.

[0037] The probing operation blocks 204 and 206 can be terminated after completion of a predetermined number of speed parameter steps and corresponding speed parameters and fiber distribution parameters are recorded, or after meeting predefined limits for the probing sequences. The recorded speed parameter measurements (SPD) together with the recorded fiber distribution parameter measurements (FDP) are then available at output of 206 to be employed at operation block 208.

[0038] During operation block 104 of FIG. 4, a papermaking process may encounter various unexpected or abnormal conditions such as sheet breaks, process transition, operator intervention, etc. In order to ensure reliable speed parameter and fiber distribution parameter measurements that are captured properly, the papermaking process can be monitored for conditions to suspend or abort operation block 104. [0039] An example, non-exclusive list of conditions that are monitored for suspending operation block 104 include one or more of the following: 1) sheet width measurement, sheet strength measurement, or FO ratio measurement is temporarily unavailable such as sheet width measuring device is not available momentarily; 2) manual sheet draw adjustment is performed; and/or 3) paper measurement variations (i.e. weight, moisture, etc.) exceed specified limits. An example, non-exclusive list of conditions that are monitored for aborting operation 104 include one or more of the following: 1 ) sheet breaks occur; 2) machine operating condition change; 3) paper grade change; 4) manual sheet width change; and/or 5) manual speed parameters change. If operation block 104 is suspended, it will resume after the suspend conditions are clear. If operation block 104 is aborted, the current speed parameters setting may remain, or be reset to their settings prior to operation block 104 to reset the entire square point control process.

[0040] In response to the completion of operation block 104, control apparatus 100 can continue at operation block 106 to conduct a square point analysis to determine the relationship between the speed parameters (SPD) and the fiber distribution parameters (FDP) measured and recorded at operation block 104. FIGs. 2A-2G provide exemplary graphs of the types of data that may be recorded during operation block 104 for use in the analysis at operation block 106.

[0041] The relationship between the speed parameters (SDP) and fiber distribution parameters (FDP) recorded during operation block 104 can be modelled with a multivariable quadratic polynomial function in operation block 106 as:

[0042] = trace (

Equation 1

[0043] where y is a fiber distribution parameter such as sheet width, sheet strength, or FO ratio; x is a column vector of speed parameters such as jet speed, wire speed, J/W speed ratio, R-D speed difference, or their combinations; c₂ is a square triangular matrix of quadratic modelling parameters; q is a column vector of linear modelling parameters; ¾ is a scalar of zero-order modelling parameter; and trace{Z) is the sum of all diagonal elements of a square matrix å. The relationship between the speed parameters (SDP) and fiber distribution parameters (FDP) recorded during operation block 104 can be also modelled with multivariable higher order polynomial functions, for example, a 4^th order polynomial function in operation block 106.

[0044] FIGs. 6A-6C show an example of a second order polynomial modelling sheet width as a function of the J/W speed ratio. The quadratic function relationship is:

[0045]

Equation 2

[0046] where y is sheet width, x is J/W speed ratio or R-D speed difference,

are modelling parameters. If sheet strength or FO ratio data is available, y can be sheet strength or FO ratio as well. With this second order polynomial, the fiber distribution square point will be at the maximum point for sheet width. Optionally, the relationship can also be modelled with higher order polynomial functions, for example, a 4^th order polynomial as:

[0047]

Equation 3

[0048] where y is sheet width, x is J/W ratio or R-D speed difference,

are modelling parameters. If sheet strength or FO ratio data is available, y can be sheet strength or FO ratio as well.

[0049] FIGs. 7A-7D show another example of a multivariable quadratic polynomial modelling sheet width as a function of jet speed and wire speed as:

[0050]

Equation 4

[0051] where y is sheet width, is jet speed, ._¾·, is wire speed,

are modelling parameters. With this multivariable polynomial model, the square point is located at the peak point of the polynomial surface as shown in FIG. 7D. [0052] FIGs. 8A-8D show one other example of a multivariable quadratic polynomial modelling FO ratio as a function of jet speed and wire speed as:

Equation 5

[0054] where y is FO ratio, ^ is jet speed, ._¾-2 is wire speed,

are modelling parameters. With this multivariable polynomial model, the square point is located at the minimum point of the polynomial surface as shown in FIG. 8D.

[0055] FIGs. 9A-9D shows yet another example of a multivariable quadratic polynomial modelling sheet strength as a function of jet speed and wire speed as:

Equation 6

[0057] where y is sheet strength, x_L is jet speed, ₂ is wire speed, e_{f i} are modelling parameters. With this multivariable polynomial model, the square point is located at the maximum point of the polynomial surface as shown in FIG. 9D.

[0058] These examples are not an exclusive list of all possible combinations. Other examples of combination could be extended from the above examples depending on the availability of speed parameters and fiber distribution parameters are contemplated herein.

[0059] After the square point analysis is completed at operation block 106, the control apparatus 100 can continue execution at operation block 108 and establish setpoints for the speed parameters of operation of the papermaking machine based on the square point determined in operation block 106. FIG. 10 shows an example of the speed parameters of R-D speed difference or J/W speed ratio at the square point and associated R-D speed difference or J/W speed ratio offsets from the square point based on sheet width and/or FO ratio model. The target J/W speed ratio or R-D speed difference can be set at the square point, or set offset a predetermined amount or threshold from the square point, depending on the specification for the paper grade to be produced. FIG. 11 shows another example of the speed parameters of jet speed and wire speed at the square point and associated offsets from the square point based on sheet width or sheet strength model. The target jet speed and wire speed can be set at the square point, or set offset a predetermined amount or threshold from the square point, depending on the specification for the paper grade to be produced.

[0060] For paper grades in which the specification requires uniform fiber distribution, the target speed parameters, such as the jet speed, wire speed, J/W speed ratio and/or R-D speed difference, can be moved and/or set to the square point, which will produce sheets with the maximum sheet width, maximum sheet strength, and/or uniform fiber distribution in all directions. For paper grades that require fiber distribution more aligning with a machine direction or other directions, the speed parameters can be set a specified offset away from its square point. At operation 108, the target speed parameters are changed either to the square point or offset away from the square point by a pre-determ ined amount or threshold from the square point, depending upon the paper grade to be produced. After the speed parameters reach their targets, all timers and enabling conditions are reset so that execution returns back to operation 102. This continuous operation of the illustrated process can be manually enabled or disabled at any time.

[0061] The present disclosure can be readily applied to nearly every papermaking machine. The present disclosure can be implemented in a control apparatus 100 that is, for example, a distributed control system (DCS) controller, or in server/client computers with open platform communication (OPC) access. The following papermaking process variables, which are typically readily available from existing papermaking machines, are needed for implementing the present disclosure: 1 ) the jet speed, wire speed, J/W speed ratio and/or the R-D speed difference control loop for monitoring of speed parameters and change of control mode and target (setpoint) of speed parameters; 2) sheet width measurements while speed parameters are probed or set; 3) optionally, if online FO measurements and/or sheet strength measurements are available, the FO ratio and/or sheet strength can be recorded while speed parameters are probed or set; 4) machine speed, sheet weight, and moisture measurements for monitoring; and/or 5) grade change event, on-grade status, sheet break status, sheet width (trim) change indicator, draw change indicator, user on-demand indicator for monitoring, suspension and abortion conditions.

[0062] Paper strength is directly affected by paperweight and its moisture content. In order to ensure a produced paper sheet that meets target strength specifications, papermakers often produce paper products by using more fibers than needed, which increases costs and waste. The present disclosure allows papermakers to produce desired paper strength without a need to apply additional fiber materials in the production process. The present disclosure provides a cost-effective means to make paper strength meet its target specification without using the additional amounts of fibers by forming a paper sheet so that the fiber distribution is either uniform in all directions, or optimized in the direction according to its specification. The reduction of fiber usage through application of the present disclosure provides significant cost savings since the fiber distribution of a paper sheet is tightly controlled relative to its square point to provide a desired paper strength.

[0063] The schematic diagrams and procedures described above are generally set forth herein. As such, the depicted order and labeled steps are indicative of representative embodiments. Other steps, orderings, combinations of steps, and methods may be conceived that are equivalent in function, logic, or effect to one or more steps, or portions thereof, of the methods illustrated in the schematic diagrams.

[0064] Additionally, the format and symbols employed are provided to explain the logical steps of the schematic diagrams and are understood not to limit the scope of the systems, apparatus, and methods illustrated by the diagrams. Additionally, the order in which a particular method occurs may or may not strictly adhere to the order of the corresponding steps shown. It will also be noted that each block of the block diagrams and/or flowchart diagrams, and combinations of blocks in the block diagrams and/or flowchart diagrams, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and program code.

[0065] Many of the functional units described in this specification have been labeled in order to more particularly emphasize the possibility of implementation independence. For example, one or more aspects of control apparatus 100, or the databases and/or servers in communication therewith, may be implemented in whole or in part as shown in FIG. 12, designated as processing system 400. Processing system 400 can be implemented as a hardware circuit comprising custom VLSI circuits or gate arrays, off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. Processing system 400 may also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices or the like.

[0066] With reference to FIG. 12, processing system 400 includes a processing device 402, an input/output device 404, memory device 406, and operating logic 408. Furthermore, the processing system 400 communicates with one or more external devices 410, including other databases, servers, or computer processing systems. Processing system 400 may be a stand-alone device, an embedded system, or a plurality of devices structured to perform the functions described with respect to the systems described herein.

[0067] Input/output device 404 enables processing system 400 to communicate with local field devices or other agents or control systems. Input/output device 404 may include a network adapter, interface, or a port (e.g., a USB port, serial port, parallel port, an analog port, a digital port, VGA, DVI, HDMI, FireWire, CAT 5, Ethernet, fiber, or any other type of communication port or interface), to name but a few examples. Input/output device 404 may include more than one of these adapters, interfaces, or ports, such as a first port for receiving data and a second port for transmitting data. [0068] Processing device 402 may include one or multiple processors, Arithmetic-Logic Units (ALUs), Central Processing Units (CPUs), Digital Signal Processors (DSPs), or Field-programmable Gate Arrays (FPGAs), to name but a few examples. For forms of processing devices with multiple processing units, distributed, pipelined, or parallel processing may be used. Processing device 402 may be dedicated to performance of only the operations described herein or may be used in one or more additional applications. Processing device 402 may be of a programmable variety that executes algorithms and processes data in accordance with operating logic 408 as defined by programming instructions (such as software or firmware) stored in memory 406. Alternatively or additionally, operating logic 408 for processing device 402 is at least partially defined by hardwired logic or other hardware. Processing device 402 may comprise one or more components of any type suitable to process the signals received from input/output device 404 or elsewhere, and provide desired output signals. Such components may include digital circuitry, analog circuitry, or a combination of both.

[0069] Memory device 406, also known as a computer readable medium, may be of one or more types of memory, such as a solid-state variety, electromagnetic variety, optical variety, or a combination of these forms, to name but a few examples. Furthermore, memory device 406 may be volatile, nonvolatile, transitory, non-transitory or a combination of these types, and some or all of memory device 406 may be of a portable variety, such as a disk, tape, memory stick, or cartridge, to name but a few examples. In addition, memory device 406 may store data that is manipulated by operating logic 408 of processing device 402, such as data representative of signals received from and/or sent to input/output device 404 in addition to or in lieu of storing programming instructions defining operating logic 408, just to name one example. Memory device 406 may be included with processing device 402 and/or coupled to processing device 402. [0070] One or more aspects of processing system 400 may also be implemented in machine-readable medium for execution by various types of processors. In some instances, the machine-readable medium for execution by various types of processors may be implemented in the aforementioned hardware circuit. An identified module of executable code may, for instance, comprise one or more physical or logical blocks of computer instructions, which may, for instance, be organized as an object, procedure, or function. Nevertheless, the executables of an identified circuit need not be physically located together, but may be comprised of disparate instructions stored in different locations which, when joined logically together, comprise the circuit and achieve the stated purpose for the processing system 400.

[0071] For example, computer readable program code may be a single instruction, or many instructions, and may even be distributed over several different code segments, among different programs, and across several memory devices. Similarly, operational data may be identified and illustrated herein within a module, monitor, or circuit, and may be embodied in any suitable form and organized within any suitable type of data structure. The operational data may be collected as a single data set, or may be distributed over different locations including over different storage devices, and may exist, at least partially, merely as electronic signals on a system or network. Where a module, monitor, or circuit or portions thereof are implemented in machine-readable medium (or computer-readable medium), the computer readable program code may be stored and/or propagated on one or more computer readable medium(s).

[0072] The computer readable medium may be a tangible computer readable storage medium storing the computer readable program code. The computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, holographic, micromechanical, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. [0073] More specific examples of the computer readable medium may include but are not limited to a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read only memory (EPROM or Flash memory), a portable compact disc read-only memory (CD-ROM), a digital versatile disc (DVD), an optical storage device, a magnetic storage device, a holographic storage medium, a micromechanical storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, and/or store computer readable program code for use by and/or in connection with an instruction execution system, apparatus, or device.

[0074] The computer readable medium may also be a computer readable signal medium. A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electrical, electro-magnetic, magnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport computer readable program code for use by or in connection with an instruction execution system, apparatus, or device. Computer readable program code embodied on a computer readable signal medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, Radio Frequency (RF), or the like, or any suitable combination of the foregoing.

[0075] In one embodiment, the computer readable medium may comprise a combination of one or more computer readable storage mediums and one or more computer readable signal mediums. For example, computer readable program code may be both propagated as an electro-magnetic signal through a fiber optic cable for execution by a processor and stored on RAM storage device for execution by the processor.

[0076] Computer readable program code for carrying out operations for aspects of the present disclosure may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++, C#, or the like and conventional procedural programming languages, such as the "C" programming language, Python,

Matlab, R, or similar programming languages. The computer readable program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone computer-readable package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

[0077] The program code may also be stored in a computer readable medium that can direct a controller, computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function/act specified herein.

[0078] Various aspects and embodiments of the present disclosure are contemplated. One or more these aspects and/or embodiments may be combined with one or more other of the aspects and/or embodiments.

[0079] For example, according to one aspect of the present disclosure, a method is provided for producing a paper sheet with a papermaking machine. The method includes determining a square point for the paper sheet from a plurality of measurements of one or more speed parameters for the papermaking machine and a plurality of measurements of one or more fiber distribution parameters for the paper sheet. The plurality of measurements for the one or more speed parameters and the plurality of measurements for the one or more fiber distribution parameters are taken during operation of the papermaking machine. The method further includes setting one or more speed parameters for the papermaking machine to produce the paper sheet based on the determined square point.

[0080] In an embodiment, the one or more speed parameters are set at values corresponding to the determined square point for the paper sheet. In an embodiment, the one or more speed parameters are set at values offset from the determined square point for the paper sheet.

[0081] In an embodiment, the one or more speed parameters include at least one of a jet speed, a wire speed, a jet-to-wire speed ratio, and a rush-to-drag speed difference of the papermaking machine. In an embodiment, the one or more fiber distribution parameters include at least one of a width of the paper sheet, a strength measurement of the paper sheet, and a fiber orientation ratio of the paper sheet.

[0082] In an embodiment, determining the square point includes stepping the one or more speed parameters of the papermaking machine depending on the one or more fiber distribution parameters of the paper sheet moving toward the square point or away from the square point.

[0083] In an embodiment, determining the square point includes modelling a relationship between the plurality of measurements of the one or more speed parameters and the plurality of measurements of the one or more fiber distribution parameters with second order polynomial functions.

[0084] In an embodiment, determining the square point includes modelling a relationship between the plurality of measurements of the one or more speed parameters and the plurality of measurements of the one or more fiber distribution parameters with fourth order polynomial functions. [0085] In an embodiment, the method includes determining a plurality of start conditions are satisfied before taking the plurality of measurements of the one or more speed parameters and the one or more fiber distribution parameters.

[0086] In an embodiment, determining the square point includes: monitoring start conditions to initiate probing of the papermaking machine; probing the papermaking machine by making a plurality of adjustments to at least one of the one or more speed parameters with the start conditions being met; obtaining the plurality of measurements of the one or more speed parameters and the plurality of measurements of the one or more fiber distribution parameters while probing the papermaking machine by making the plurality of adjustments to the at least one of the one or more speed parameters; and modeling a relationship between the plurality of measurements of the one or more speed parameters with the plurality of adjustments to the at least one of the one or more speed parameters and the plurality of measurements of the one or more fiber distribution parameters.

[0087] In an embodiment, the start conditions include a set of AND conditions and a set of OR conditions. In an embodiment, probing the papermaking machine is started in response to the AND conditions and the OR conditions being satisfied.

[0088] According to another aspect of the present disclosure, a control apparatus is provided for a papermaking machine to produce a paper sheet. The control apparatus includes at least one computer processor that operates on the papermaking machine to determine a square point for the paper sheet from a plurality of measurements of one or more speed parameters for the papermaking machine and a plurality of measurements of one or more fiber distribution parameters for the paper sheet. The plurality of measurements for the one or more speed parameters and the plurality of measurements for the one or more fiber distribution parameters are taken during operation of the papermaking machine. The at least one computer processor sets one or more speed parameters for operation of the papermaking machine based on the determined square point. [0089] In an embodiment, the one or more speed parameters include at least one of a jet speed, a wire speed, a jet-to-wire speed ratio, and a rush-to-drag speed difference of the papermaking machine. In an embodiment, the one or more fiber distribution parameters include at least one of a width of the paper sheet, a strength measurement of the paper sheet, and a fiber orientation ratio of the paper sheet.

[0090] In an embodiment, at least one computer processor operates on the papermaking machine to step at least one of the one or more speed parameters of the papermaking machine depending on the one or more fiber distribution parameters of the paper sheet moving toward its square point or away from its square point.

[0091] In an embodiment, at least one computer processor operates on the papermaking machine to determine the square point by modelling a relationship between the plurality of measurements of the one or more speed parameters and the plurality of measurements of the one or more fiber distribution parameters with at least one of second order polynomial or fourth order polynomial functions.

[0092] In an embodiment, the one or more speed parameters are set at values corresponding to the determined square point for the paper sheet. In an embodiment, the one or more speed parameters are set at values offset from the determined square point for the paper sheet.

[0093] In an embodiment, at least one computer processor operates on the papermaking machine to: monitor start conditions to initiate probing of the papermaking machine; probe the papermaking machine by making a plurality of adjustments to at least one of the one or more speed parameters with the start conditions being met; obtain the plurality of measurements of the one or more speed parameters and the plurality of measurements of the one or more fiber distribution parameters while probing the papermaking machine by making the plurality of adjustments to the at least one of the one or more speed parameters; and model a relationship between the plurality of measurements of the one or more speed parameters with the plurality adjustments to the at least one of the one or more speed parameters and the plurality of measurements of the one or more fiber distribution parameters.

[0094] In an embodiment, the start conditions include a set of AND conditions and a set of OR conditions. In an embodiment, probing the papermaking machine is started in response to the AND conditions and the OR conditions being satisfied.

[0095] According to another aspect of the present disclosure, a method for determining a square point for a paper sheet produced by a papermaking machine includes: a) measuring one or more speed parameters and associated one or more fiber distribution parameters of the paper sheet during operation of the papermaking machine; b) stepping at least one of the one or more speed parameters of the papermaking machine in a first direction; c) measuring, after stepping the at least one of the one or more speed parameters in the first direction in step b), the one or more speed parameters and associated one or more fiber distribution parameters of the paper sheet; d) in response to the one or more fiber distribution parameters moving away from the square point in step b), stepping the at least one of the one or more speed parameters of the papermaking machine in a second direction opposite the first direction and measuring the one or more speed parameters and the associated one or more fiber distribution parameters of the paper sheet; and e) in response to the one or more fiber distribution parameters approaching the square point in step b) or step d), repeatedly stepping the at least one of the one or more speed parameters of the papermaking machine and measuring the one or more speed parameters and associated one or more fiber distribution parameters of the paper sheet until the one or more fiber distribution parameters move away from the square point.

[0096] In an embodiment, the method includes determining the square point by modelling the measurements of the one or more speed parameters and the associated one or more fiber distribution parameters with one of second order polynomial or fourth order polynomial functions. In an embodiment, the method includes setting one or more speed parameters for the papermaking machine to produce the paper sheet based on the determined square point.

[0097] According to another aspect of the present disclosure, a control apparatus for determining a square point for a paper sheet produced by a papermaking machine is provided. The control apparatus is configured to: a) measure one or more speed parameters and associated one or more fiber distribution parameters of the paper sheet during operation of the papermaking machine; b) step at least one of the one or more speed parameters of the papermaking machine in a first direction; c) measure, after stepping the at least one of the one or more speed parameters in the first direction in step b), the one or more speed parameters and the associated one or more fiber distribution parameters of the paper sheet; d) in response to the one or more fiber distribution parameters moving away from the square point in step b), step the at least one of the one or more speed parameters of the papermaking machine in a second direction opposite the first direction and measure the one or more speed parameters and the associated one or more fiber distribution parameters of the paper sheet; and e) in response to the one or more fiber distribution parameters approaching the square point in step b) or step d), repeatedly step the at least one of the one or more speed parameters of the papermaking machine and measure the one or more speed parameters and the associated one or more fiber distribution parameters of the paper sheet until the one or more fiber distribution parameters move away from the square point.

[0098] In an embodiment, the control apparatus is configured to determine the square point by modelling the measurements of the one or more speed parameters and the associated one or more fiber distribution parameters with one of second order polynomial or fourth order polynomial functions. In an embodiment, the control apparatus us configured to set one or more speed parameters for the papermaking machine to produce the paper sheet based on the determined square point.

[0099] Reference throughout this specification to "one embodiment," "an embodiment," or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment," "in an embodiment," and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

[0100] Accordingly, the present disclosure may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the disclosure is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

[0101] While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only certain exemplary embodiments have been shown and described. Those skilled in the art will appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims.

[0102] In reading the claims, it is intended that when words such as “a,” “an,” “at least one,” or “at least one portion” are used there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. When the language “at least a portion” and/or “a portion” is used the item can include a portion and/or the entire item unless specifically stated to the contrary.

Claims

What is claimed is:

1 . A method for producing a paper sheet with a papermaking machine, the method comprising: determining a square point for the paper sheet from a plurality of measurements of one or more speed parameters for the papermaking machine and a plurality of measurements of one or more fiber distribution parameters for the paper sheet, wherein the plurality of measurements for the one or more speed parameters and the plurality of measurements for the one or more fiber distribution parameters are taken during operation of the papermaking machine; and setting one or more speed parameters for the papermaking machine to produce the paper sheet based on the determined square point.

2. The method of claim 1 , wherein the one or more speed parameters are set at values corresponding to the determined square point for the paper sheet.

3. The method of claim 1 , wherein the one or more speed parameters are set at values offset from the determined square point for the paper sheet.

4. The method of claim 1 , wherein the one or more speed parameters include at least one of a jet speed, a wire speed, a jet-to-wire speed ratio, and a rush-to-drag speed difference of the papermaking machine.

5. The method of claim 1 , wherein the one or more fiber distribution parameters include at least one of a width of the paper sheet, a strength measurement of the paper sheet, and a fiber orientation ratio of the paper sheet.

6. The method of claim 1 , wherein determining the square point includes stepping the at least one of the one or more speed parameters of the papermaking machine depending on the one or more fiber distribution parameters of the paper sheet moving toward the square point or away from the square point.

7. The method of claim 1 , wherein determining the square point includes modelling a relationship between the plurality of measurements of the one or more speed parameters and the plurality of measurements of the one or more fiber distribution parameters with second order polynomial functions.

8. The method of claim 1 , wherein determining the square point includes modelling a relationship between the plurality of measurements of the one or more speed parameters and the plurality of measurements of the one or more fiber distribution parameters with fourth order polynomial functions.

9. The method of claim 1 , further comprising determining a plurality of start conditions are satisfied before taking the plurality of measurements of the one or more speed parameters and the one or more fiber distribution parameters.

10. The method of claim 1 , wherein determining the square point includes: monitoring start conditions to initiate probing of the papermaking machine; probing the papermaking machine by making a plurality of adjustments to at least one of the one or more speed parameters with the start conditions being met; obtaining the plurality of measurements of the one or more speed parameters and the plurality of measurements of the one or more fiber distribution parameters while probing the papermaking machine by making the plurality of adjustments to the at least one of the one or more speed parameters; and modeling a relationship between the plurality of measurements of the one or more speed parameters with the plurality of adjustments to the at least one of the one or more speed parameters and the plurality of measurements of the one or more fiber distribution parameters.

11. The method of claim 10, wherein the start conditions include a set of AND conditions and a set of OR conditions.

12. The method of claim 11 , wherein probing the papermaking machine is started in response to the AND conditions and the OR conditions being satisfied.

13. A control apparatus for a papermaking machine to produce a paper sheet, the control apparatus including at least one computer processor that operates on the papermaking machine to: determine a square point for the paper sheet from a plurality of measurements of one or more speed parameters for the papermaking machine and a plurality of measurements of one or more fiber distribution parameters for the paper sheet, wherein the plurality of measurements for the one or more speed parameters and the plurality of measurements for the one or more fiber distribution parameters are taken during operation of the papermaking machine; and set one or more speed parameters for operation of the papermaking machine based on the determined square point.

14. The control apparatus of claim 13, wherein the one or more speed parameters include at least one of a jet speed, a wire speed, a jet-to-wire speed ratio, and a rush-to-drag speed difference of the papermaking machine.

15. The control apparatus of claim 13, wherein the one or more fiber distribution parameters include at least one of a width of the paper sheet, a strength measurement of the paper sheet, and a fiber orientation ratio of the paper sheet.

16. The control apparatus of claim 13, wherein at least one computer processor operates on the papermaking machine to step at least one of the one or more speed parameters of the papermaking machine depending on the one or more fiber distribution parameters of the paper sheet moving toward its square point or away from its square point.

17. The control apparatus of claim 13, wherein at least one computer processor operates on the papermaking machine to determine the square point by modelling a relationship between the plurality of measurements of the one or more speed parameters and the plurality of measurements of the one or more fiber distribution parameters with at least one of second order polynomial or fourth order polynomial functions.

18. The control apparatus of claim 13, wherein the one or more speed parameters are set at values corresponding to the determined square point for the paper sheet.

19. The control apparatus of claim 13, wherein the one or more speed parameters are set at values offset from the determined square point for the paper sheet.

20. The control apparatus of claim 13, wherein at least one computer processor operates on the papermaking machine to: monitor start conditions to initiate probing of the papermaking machine; probe the papermaking machine by making a plurality of adjustments to at least one of the one or more speed parameters with the start conditions being met; obtain the plurality of measurements of the one or more speed parameters and the plurality of measurements of the one or more fiber distribution parameters while probing the papermaking machine by making the plurality of adjustments to the at least one of the one or more speed parameters; and model a relationship between the plurality of measurements of the one or more speed parameters with the plurality adjustments to the at least one of the one or more speed parameters and the plurality of measurements of the one or more fiber distribution parameters.

21. The control apparatus of claim 20, wherein the start conditions include a set of AND conditions and a set of OR conditions.

22. The control apparatus of claim 21 , wherein probing the papermaking machine is started in response to the AND conditions and the OR conditions being satisfied.

23. A method for determining a square point for a paper sheet produced by a papermaking machine, the method comprising: a) measuring one or more speed parameters and associated one or more fiber distribution parameters of the paper sheet during operation of the papermaking machine; b) stepping at least one of the one or more speed parameters of the papermaking machine in a first direction; c) measuring, after stepping the at least one of the one or more speed parameters in the first direction in step b), the one or more speed parameters and associated one or more fiber distribution parameters of the paper sheet; d) in response to the one or more fiber distribution parameters moving away from the square point in step b), stepping the at least one of the one or more speed parameters of the papermaking machine in a second direction opposite the first direction and measuring the one or more speed parameters and the associated one or more fiber distribution parameters of the paper sheet; and e) in response to the one or more fiber distribution parameters approaching the square point in step b) or step d), repeatedly stepping the at least one of the one or more speed parameters of the papermaking machine and measuring the one or more speed parameters and associated one or more fiber distribution parameters of the paper sheet until the one or more fiber distribution parameters move away from the square point.

24. The method of claim 23, further comprising: f) determining the square point by modelling the measurements of the one or more speed parameters and the associated one or more fiber distribution parameters with one of second order polynomial or fourth order polynomial functions.

25. The method of claim 24, further comprising: g) setting one or more speed parameters for the papermaking machine to produce the paper sheet based on the determined square point.

26. A control apparatus for determining a square point for a paper sheet produced by a papermaking machine, the control apparatus being configured to: a) measure one or more speed parameters and associated one or more fiber distribution parameters of the paper sheet during operation of the papermaking machine; b) step at least one of the one or more speed parameters of the papermaking machine in a first direction; c) measure, after stepping the at least one of the one or more speed parameters in the first direction in step b), the one or more speed parameters and the associated one or more fiber distribution parameters of the paper sheet; d) in response to the one or more fiber distribution parameters moving away from the square point in step b), step the at least one of the one or more speed parameters of the papermaking machine in a second direction opposite the first direction and measure the one or more speed parameters and the associated one or more fiber distribution parameters of the paper sheet; and e) in response to the one or more fiber distribution parameters approaching the square point in step b) or step d), repeatedly step the at least one of the one or more speed parameters of the papermaking machine and measure the one or more speed parameters and the associated one or more fiber distribution parameters of the paper sheet until the one or more fiber distribution parameters move away from the square point.

27. The control apparatus of claim 26, wherein the control apparatus is configured to: f) determine the square point by modelling the measurements of the one or more speed parameters and the associated one or more fiber distribution parameters with one of second order polynomial or fourth order polynomial functions.

28. The control apparatus of claim 27, wherein the control apparatus us configured to: g) set one or more speed parameters for the papermaking machine to produce the paper sheet based on the determined square point.