Self-optimizing profiling system

Abstract

A method for the automated optimization of a quality profile (1) of a paper, cardboard, or fiber web (web) (2), comprising a quality measurement system (3), an actuator system (5), and a control system (8), wherein the following steps are performed: • a maximum value is set for at least one actuator (6), the effectiveness of the action being determined at the maximum value using the quality measurement system (3), • the actuator (6) is controlled stepwise to the minimum value, the effectiveness of the action being determined for each step using the quality measurement system (3), • a characteristic curve (12) for the actuator (6) is calculated, which is used by the control system (8) to achieve the required quality profile (1) of the web (2). The invention further relates to a profiling system.

Description

[0001] The invention relates to methods for the automated optimization of a quality profile of a paper, cardboard, or fiber web, comprising a quality measuring system designed to detect at least one moisture value and a value for an area-related mass of the web by means of measuring carriages across the web width in the machine transverse direction (CD), an actuator system designed to apply a different quantity of water or water vapor to the web across the web width (CD) via a plurality of actuators, and a control system designed to control the actuators of the actuator system individually. Furthermore, the invention relates to a profiling system for the automated optimization of a quality profile of a paper, cardboard, or fiber web.

[0002] Prior art includes quality control systems that improve web quality in the machine transverse direction (CD). EP1620766 A1 discloses a method for controlling quality values ​​according to the proportions in the machine transverse direction (CD) and the machine running direction (MD). In practice, however, the actuator systems used exhibit wear and are operated under varying conditions.

[0003] The object of the invention is to provide a method for achieving efficient operation of a control system for optimizing a quality profile in a plant for the production of paper, cardboard, or fiber webs. Furthermore, the object of the invention is to provide a profiling system that, even during extended operation, despite wear and tear and changing operating conditions, always operates within an optimal operating range.

[0004] The problem is solved according to the invention by an embodiment according to the independent claims. Further advantageous embodiments of the present invention are found in the dependent claims.

[0005] The problem is further solved according to the invention by a method in which the following method steps are carried out: for at least one actuator a maximum value is controlled, whereby the effectiveness of the order is determined at the maximum value using the quality measurement system, the actuator is controlled step by step to the minimum value, whereby the effectiveness of the order is determined for each step using the quality measurement system, a characteristic curve for the actuator is calculated, which is used by the control system to achieve the required quality profile of the railway.

[0006] Regularly testing a single actuator can be advantageous in demonstrating the efficiency of its steam application. For example, wear or contamination often prevents the full control range of an actuator from being utilized. The operating range of the actuator, determined in this way, can then be stored in the control system as a characteristic curve. This curve can show both extreme values ​​and a progression across the actuator's operating range. For instance, the characteristic curve for an actuator shows the range within which the actuator can move and assigns an efficiency value to each segment within that range. It is particularly advantageous if the actuator includes a valve to store the valve opening and flow rate in the characteristic curve.It has been shown that this characteristic curve changes over the lifespan of an actuator. For example, deposits and / or wear can lead to varying efficiencies at different actuator positions. Furthermore, wear can restrict actuators within their maximum or minimum ranges. This can result in a valve no longer closing completely and / or opening fully. Therefore, a maximum value is not necessarily an absolute maximum but may only apply to the specific actuator in question. Other possible values ​​for the characteristic curve include the effectiveness of steam application, the throughput of applied water, and / or flow rates. It is also possible to represent wear as a characteristic value in the curve, for example, by comparing the proportion of the currently available control range with the control range of a new actuator.

[0007] The effectiveness of steam application is particularly advantageous with regard to energy efficiency, whereby the proportion of steam condensed on the web, compared to the proportion released into the environment, can influence the effectiveness as a function of the web's basis weight and / or production speed. Thus, a characteristic curve relating the valve opening degree to the effectiveness of steam application can be advantageously incorporated into a control system.

[0008] A further advantage is a method in which the web width in the machine transverse direction (CD) is measured using a quality measuring system, whereby the measured value is taken into account for the control of the actuators.

[0009] While monitoring the web edge is possible and known via quality measurement systems, this information is not currently used to update the dampening control during operation. For example, a format change on the paper machine can alter the edge position, affecting the efficiency of the actuators in the edge area. Changes in basis weight or paper grade can also lead to changes in the edge area due to shrinkage during drying. Here, too, separate monitoring of the edge actuators is advantageous to prevent over-drying of the edge, which can otherwise lead to disruptions and / or tears in paper production.

[0010] A further advantageous method is wherein the actuator system is supplied with water and / or steam via a supply line, wherein the supply line includes a supply valve and at least one pressure measurement, wherein the effectiveness of the application is determined as a function of the measured value of the pressure measurement and the valve position of the supply valve.

[0011] When steam is applied to the web using the actuator system, the control system can advantageously perform an efficiency test of the steam pressure used. For this purpose, the steam pressure and temperature are recorded and transmitted to the control system. The efficiency of the actuators is then evaluated taking the steam pressure and / or temperature into account. It has been shown that this method can partially compensate for actuator wear by changing the steam pressure and / or temperature.

[0012] A further advantage is a method in which a calibration of the characteristic curve is carried out at regular intervals for each individual actuator, whereby a maximum value, a minimum value and at least one intermediate value are controlled and whereby the effectiveness of the application of water and / or steam is determined for the positions of the actuator in CD using the quality measurement system.

[0013] Regular automatic calibration of the actuator characteristic curves is advantageous to ensure the actuators always operate within their optimal range. Calibration can be performed, for example, once per shift (8 hours), once per day, and / or once per week. Targeted repetition at shorter intervals is also beneficial, especially if the values / characteristic curves of individual actuators show significant deviations. This allows for the early identification of signs of damaged actuators. Calibration of the characteristic curves can be particularly advantageous when no marketable paper is being produced, such as during drum changes. A corresponding signal from the paper machine's control system can be conveniently provided to the control system for this purpose.

[0014] A further advantage is a method in which a setpoint of an actuator is changed by at least 5%, wherein the quality measurement system determines at least a basis weight and a moisture content for the position in CD of the web on which the actuator is positioned.

[0015] A precise analysis of individual values ​​for different positions across the width of the path is crucial for determining efficiency. Averaging these values ​​can lead to inaccurate results, hindering a precise efficiency assessment. An excessively fine step size for actuator positions has also proven detrimental, as it can distort the results due to other factors. A step size of 5% to 50% for actuator position changes is particularly advantageous, especially a range of 10% to 30%. This allows the quality measurement system to accurately detect changes, enabling a more effective evaluation of the actuators' function and / or efficiency.

[0016] Furthermore, a method is advantageous in which those actuators (6) of the actuator system are moved whose effect on the path can be directly measured by a suitable position of the measuring carriage of the quality measuring system in the machine transverse direction (CD).

[0017] The quality measurement systems used in the paper industry employ measuring carriages that traverse the web in the machine's transverse direction (CD). Creating a quality profile therefore typically takes one minute or more. Only one current measurement of the web in CD is recorded at a time. It is therefore particularly advantageous to coordinate the position of the measuring carriage and the actuator under test. This allows for targeted testing of the actuator whose position in CD the measuring carriage is currently recording. Conversely, it is also particularly advantageous to keep the measuring carriage in the CD position until the actuator test is completed, and / or until the calibration of an actuator's characteristic curve in the same position is finished.

[0018] Coordinating the position of the measuring carriage with the actuator under test can significantly accelerate the actuator test and thus reduce the disruptive influence on the paper web. Calibrating the characteristic curves of multiple actuators can be particularly advantageous when performed concurrently with a traversal of the measuring carriage.

[0019] A further advantage is a method wherein the control system includes at least two of the following values ​​and is used to control the actuator system: Speed ​​of the web, basis weight of the web, moisture content of the web, temperature, pressure and / or amount of water applied

[0020] The calibrated actuator system can advantageously utilize additional parameters to achieve precise control of the cross-sectional profile. A linear consideration of the basis weight and / or speed values ​​is particularly effective. These values ​​are advantageously used jointly for all or a majority of the actuators to adjust the amount of applied steam and / or water to the production conditions. The primary control objective of the actuator system is usually to achieve a balanced moisture profile; therefore, using the measured moisture level is always beneficial for the described process. Furthermore, correcting the actuators based on the temperature and / or pressure of the application medium is particularly advantageous, as these factors directly influence the condensation potential of the steam that can condense on the web.The pressure and temperature of the applied steam and / or water can be used to account for the potentially achievable application rate. For example, the condensation potential can be calculated, i.e., how much steam can condense on the web at most. Measuring and using the web temperature can also improve the precision of the control system. The values ​​used can always contribute to ensuring that the moisture profile is controlled as precisely and quickly as possible.

[0021] A further advantage is a method in which the control system includes the characteristic curves of the actuators and is designed to store and / or modify them.

[0022] For the method according to the invention, it is advantageous to combine and store the characteristic curves and / or correction values ​​of the control system in a digital control system. If new characteristic curves are determined or new correction values ​​are calculated through calibration and / or by running a test program, these can be stored in the controller and used as control parameters. For this purpose, it is particularly advantageous to maintain the relationships between the measured values, the actuator behavior, and setpoints as a physical and / or empirical model in the controller. Threshold values ​​and / or safety values ​​can also be stored in such a model to prevent overriding and / or malfunctions of the controller.

[0023] A further advantageous profiling system for the automated optimization of a quality profile of a paper, cardboard or fiber web (web) comprises a quality measurement system configured to record a quality profile across the web width (CD) for at least the moisture content and basis weight of the web, an actuator system configured to apply a different quantity of water or water vapor to the web via a plurality of actuators across the web width (CD), a control system configured to control the actuators of the actuator system individually, wherein the quality profile values ​​of the quality measurement system for at least basis weight and moisture are transmitted to the control system, wherein the control system includes a measured value of the web speed and a characteristic curve for the efficiency of the actuators, and wherein the control system is configured to control the actuator system taking into account at least these values.

[0024] Controlling the quality profile can be particularly effective if the control system incorporates a characteristic curve that includes the effectiveness of the actuators. This allows the system to determine the optimal application range of steam or water to the web for each individual actuator. Furthermore, depending on operating conditions, such as web speed or basis weight, different condensation potentials may exist during steam application. Here, too, a characteristic curve and / or a simplified physical model in the control system is advantageous for consistently achieving the best possible control results.

[0025] A further advantage is a profiling system in which the actuator system includes at least pressure and temperature measurements and is designed to transmit the measured values ​​to the control system. Particularly when the actuator system applies steam to the web, it is advantageous to adjust the application values ​​depending on the steam conditions. For example, when using superheated steam, condensation on the web and / or the behavior of the actuators may differ. Control of the quality profile is thus improved by appropriately considering the pressure and temperature of the application medium. Similarly, when applying water, the viscosity and surface tension change with temperature, and the behavior of the actuators with respect to flow rates, pressure drop, and / or behavior at spray nozzles changes accordingly.

[0026] A profiling system is also advantageous, in which the actuators of the actuator system include position measurement and the actuator system is designed to transmit the measured values ​​to the control system. An important correction of the control values ​​can also be made from the position measurement of the actuators. It has been shown that the setpoint used to control the actuator can lead to a variable actual value at the actuator. Particularly with valves used as actuators, the precision of the control can decrease over time due to deposits or wear. By comparing the actual position with the effect of the actuator, a characteristic curve can be created, which can also be used in the control system to improve control performance.

[0027] A further advantage is a profiling system in which the control system uses the measured values ​​from the quality measurement system and the actuator system, as well as the web speed, to create and / or modify a characteristic curve for individual actuators. The control system can be particularly advantageously implemented as a digital control system, in which the characteristic curves and / or more complex models are stored. During corresponding test or calibration runs of the actuators, the characteristic curves can thus be easily adjusted, and calibrations can be performed automatically by the control system.

[0028] The invention will be explained below with the aid of figures. The figures show, in detail: Fig. 1 : Device for carrying out the inventive method.

[0029] Figure 1Figure 1 shows a schematic representation of a profiling system 20 of a machine for producing a paper, cardboard, or fiber web (web) 2, comprising an actuator system 4 for steaming and / or moistening the web 2 and a quality measurement system 4. The actuator system comprises a plurality of actuators 6, each of which symbolically includes a valve and an application zone. The application zone can thus apply water or steam 7 to the web 2. This modifies the quality profile 1 and the varying moisture content 15, since additional moisture is introduced into the web 2 in the area in the machine transverse direction (CD) where the actuator applies water or steam. If steam 7 is applied to the web by an actuator, the web is heated by condensation of the steam 7. The altered temperature of the web at this point can, in turn, lead to increased dewatering, since the viscosity of water decreases with increasing temperature.When steam is applied, a lower moisture content 14 of the web can be achieved at position CD. The profiling system comprises a central control system 8, which is advantageously designed as a digital control system 8, and includes information for the calibration and control of the actuators 6, in particular a characteristic curve 12 which can be stored in the control system 8 for each actuator 6 and is advantageously used to control the actuator system 5. The control system 8 is designed such that a change in the characteristic curve 12 can be detected and stored, thus enabling automatic calibration. Furthermore, the control system 8 is designed to receive measured values ​​from a quality measurement system 3 and, in particular, to receive a speed value 13 of the web 2 from a machine control system (not shown graphically).The quality measurement system 3 comprises a measuring carriage 4 that travels across the web in CD and can create a quality profile 1 for each measured value using individual sensors. The measuring carriage 4 advantageously includes a sensor for the basis weight, which measures the basis mass of the web in g / m². Furthermore, the measuring carriage advantageously and optionally includes a moisture sensor 15, which can measure the moisture content of the web, the moisture content 15, whereby the moisture content is determined in gH₂O / m² or calculated as % moisture relative to the basis weight. The measured values ​​are advantageously processed in the control system or in the quality measurement system to create quality profiles via CD.

[0030] The control system 8 also includes individual measurements from the actuator system 5, which, in particular during steam application, include a pressure measurement 11 and / or a temperature measurement 16 in the supply line 9. These values ​​can be used to control the steam pressure 11 in the actuator system 5, whereby the supply line valve 10 can be used as a manipulated variable or actuator in the control system. Reference symbol list

[0031] 1 Quality profile 2 Paper, cardboard or fiber web, web 3 Quality measuring system 4 Measuring carriage 5 Actuator system 6 Actuator 7 Water / steam 8 Control system 9 Supply line 10 Supply valve 11 Pressure measurement 12 Characteristic curve 13 Web speed 14 Basis weight [g / m² < ] 15 Moisture content [gH₂O / m² < , %] 16 Temperature sensor / Temperature 20 Profiling system CD Web width, machine cross direction (Cross Direction) MD Machine direction (Machine Direction)

Claims

1. Method for the automated optimization of a quality profile (1) of a paper, cardboard or fiber web (web) (2), comprising a quality measurement system (3) designed to record at least one moisture value and one area-related mass value of the web (2) by means of measuring carriages (4) across the web width in the machine transverse direction (CD), an actuator system (5) designed to apply a different quantity of water or water vapor (7) to the web (2) across the web width (CD) via a plurality of actuators (6), and a control system (8) designed to control the actuators (6) of the actuator system (5) individually. characterized by the fact that the following process steps are carried out,• wherein a maximum value is controlled for at least one actuator (6), the effectiveness of the order is determined at the maximum value using the quality measurement system (3), • the actuator (6) is controlled stepwise to the minimum value, the effectiveness of the order is determined for each step using the quality measurement system (3), • a characteristic curve (12) for the actuator (6) is calculated, which is used by means of the control system (8) to achieve the required quality profile (1) of the track (2).

2. Method according to claim 1, characterized by the fact that The web width in the machine transverse direction (CD) is measured using a quality measuring system (3), taking into account the measured value for the control of the actuators (8).

3. Method according to claim 1 or claim 2 , characterized in thatthe actuator system (8) is supplied with water and / or steam (7) via a supply line (9), wherein the supply line (9) includes a supply valve (10) and at least one pressure measurement (11), wherein the effectiveness of the application is determined as a function of the measured value of the pressure measurement (11) and the valve position of the supply valve (10).

4. Method according to any of the preceding claims, characterized by the fact that At regular intervals, a calibration of the characteristic curve (12) is carried out for each individual actuator (6), whereby a maximum value, a minimum value and at least one intermediate value are controlled, and whereby the effectiveness of the application of water and / or water vapor (7) is determined for the positions of the actuator (6) in CD using the quality measurement system (3).

5. Method according to any of the preceding claims, characterized by the fact thata setpoint of an actuator (6) is changed by at least 5%, wherein the quality measurement system (3) determines at least a basis weight (14) and a moisture content (15) for the position in CD of the web (2) where the actuator (6) is positioned.

6. Procedure according to any of the preceding claims, characterized by the fact that Those actuators (6) of the actuator system (5) are moved whose effect on the path (2) can be directly measured by a suitable position of the measuring carriage (4) of the quality measuring system (3) in the machine transverse direction (CD).

7. Procedure according to any of the preceding claims, characterized by the fact that the control system (7) includes at least two of the following values ​​and is used to control the actuator system (5): • Speed ​​of the web (13) • Basis weight of the web (14) • Moisture content of the web (15) • Temperature (14), pressure and / or amount of water applied 8. Method according to any of the preceding claims, characterized by the fact that the control system (8) includes the characteristic curves (12) of the actuators (6) and is designed to store and / or modify them.

9. Profiling system (20) for the automated optimization of a quality profile (1) of a paper, board or fiber web (web) (3), comprising, (1.1) a quality measurement system (3) configured to record a quality profile (1) across the web width (CD) for at least the moisture content (15) and basis weight (15) of the web (2), (1.2) an actuator system (4) configured to apply a different quantity of water or water vapor (6) to the web across the web width (CD) via a plurality of actuators (5), (1.3) a control system (8) configured to control the actuators (5) of the actuator system (4) individually characterized by the fact thatthe values ​​of the quality profiles (1) of the quality measurement system (3) for at least basis weight (14) and moisture (15) are transmitted to the control system (7), wherein the control system (7) includes a measured value of the speed of the web (13) and a characteristic curve (12) for the efficiency of the actuators (6), and wherein the control system (8) is designed to control the actuator system (5) taking into account at least these values.

10. Profiling system (20) according to claim 9, characterized by the fact that the actuator system (5) includes at least a pressure measurement (11) and a temperature measurement (16) and is designed to transmit the measured values ​​to the control system (8).

11. Profiling system (20) according to claim 9 or claim 10, characterized by the fact that the actuators (6) of the actuator system (5) include position measurement and the actuator system (5) is designed to transmit the measured values ​​to the control system (8).

12. Profiling system (20) according to one of claims 9 to 11, characterized by the fact that the control system (8) is executed, the measured values ​​from the quality measurement system (3) and actuator system (5) as well as the speed of the web (13) are used to create and / or modify a characteristic curve (12) for individual actuators (6).

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