EP0803011B1 - Process and device for determining the effect of adjustement of final control elements - Google Patents

Abstract

A method for determining the effect of an adjustment of actuators used in the manufacture of web of material which are arranged spatially over the width of the web and influence the properties of the web of material, the method being characterized by the fact that, upon the adjustment of one actuator, a prediction as to the effect of the adjustment of the actuator which is derived from detection values on the behavior of the cross section of the property of the web upon the change of actuators is made; that at least one cross section of a property of the web is measured before and after the adjustment of the actuators; that the prediction as to the effect of the actuator adjustments is compared with the measured effect; and that the existing detection values are modified until better agreement is obtained between predicted effect and measured effect.

Description

The invention relates to a method and a device to determine the effect of the adjustment of actuators according to the preambles of Claims 1 and 20 (see DE-A-4 238 037, US-A-5 400 247).

In the production of material webs, for example of paper or cardboard webs, must Cross section of the material web properties and the Offset of the web of material to be determined to Certain setting of a desired cross profile Actuators to be able to adjust the manufacturing the material web are used over the web width is distributed and the material web properties influence.

It is known material web sections of the manufacturing machine to be taken and examined in the laboratory, around the cross section of certain web properties to investigate. This process is very complex and shows the disadvantage that undesirable properties can be determined very late. Avoiding these properties can be very difficult done much later, so often large portions of Material webs have quality defects or as Committee must be worked up again.

It is also known to determine a cross shrink cross profile a paper web with suitable Devices to apply markings on the web and this with the help of suitable facilities, For example sensors to detect (DE 40 08 282 A1). The paper machine must therefore be designed in this way be that both the marker and also introduced the appropriate detection devices can be. Often this is necessary Space is not available or for space reasons not available. In addition, the costs increase for such a paper machine. The procedure to determine cross shrinkage is also very expensive because additional markers are used Need to become. Marking is also undesirable, because it reduces paper quality.

It is finally known to help identify the local area Assignment of actuator positions to measuring positions so-called "bump tests" on the paper web perform. These are test adjustments individual far enough apart Actuators with the aim, based on cross profile measurements the locations and the geometric shape of the Effects of these actuators on paper properties ascertain. Such test adjustments then automatically become periodic, for example or carried out at the operator's request to make a change Recognize process behavior. The test adjustments must be chosen so large that the Finds the result of the adjustment in the paper clearly and after suitable measurement filtering stands out from the process noise and measurement noise. The So tests disrupt the production process. While The bump tests and their evaluation can of course be done not at the same time with the help of this Actuators are acted on the process to for example to compensate for current process disturbances. A possible web property cross profile regulation must be switched off during the test. The accuracy with which the impact locations of the adjusted actuators are determined is determined by the number of transverse profile measurements are available, or by the distance individual data values. This distance is usually 1 cm to 10 cm. In any case, it is achieved accuracy is not sufficient to get out of determined locations an exact cross-shrink cross profile to determine as the following sample calculation shows:

The locations of the control elements are exactly known across the width of the production machine. Two actuators that are as far apart as possible are adjusted. The distance x _{s of} these actuators is known. The distance between the profile changes x _p can be measured.

The percentage transverse shrinkage is then: Shrinkage = ((x s - x p ) / x s ) 100%.

With a paper web width of, for example 5000 mm, a typical shrinkage of 5% = 250 mm and a measurement data distance of 25 mm is a total shrinkage determination possible enough.

The measuring task is, for example, the Clarify question at which point of the paper web the shrinkage is minimal, whether it is symmetrical, how the edges of the paper web compared to the Behave in the middle etc. The shrinkage must therefore be as possible small areas on the paper web if possible be measured precisely to create a meaningful cross-shrink cross profile to obtain.

For example, in a 500 mm wide area determine the shrinkage to 0.5% absolute accuracy To be able to do so is a measuring accuracy in paper 500 x 0.005 mm = 2.5 mm required. At a Measurement data distance of 25 mm is easy Bump testing is nowhere near possible.

In a method for elimination known from DE-A-42 38 037 of residual errors in the cross section of a material web are as possible many operating states using statistical methods, mathematical models created. For a particular operating state that occurs during operation this becomes the closest from these mathematical models upcoming selected. Based on the selected model, a is then Correction vector is determined and introduced into the production process. The the selection of a suitable mathematical model and the determination steps relating to a correction vector are carried out up to the desired step Repeat adjustment. The measured during operation Results can be used to improve the mathematical models created be used.

In a method of manufacture known from US-A-5 400 247 A paper web becomes several actuators distributed over the web width via a control system in which the individual process impact of each actuator from the process impact of the others Actuators are separated or decoupled, so that a process control is possible via independent channels. The Actuators based on a theoretical dynamic model of the Paper machine controlled without coupling effect. Measured via sensors Output signals are generated using a mathematical decoupling model evaluated in the form of an adjustable decoupling matrix. The initial values of the theoretical model of the paper machine without Coupling effect with the output values of the adjustable Decoupling model compared. The decoupling matrix is then in the Continuously adjusted to align these values.

It is therefore an object of the invention to provide a method and a device for determining the impact an adjustment of actuators to accomplish, that do not have the disadvantages mentioned.

This task is solved with the help of a procedure comprising the steps mentioned in claim 1 and in terms of control technology in a broader sense can be described as a "process observer". The Place where the adjustment of an actuator affects that in the manufacture of the material web can be used at any time can be determined without special use Marking devices or additional sensors would need to capture these markings. The production is not through test adjustments and by switching off an existing one Cross profile control disrupted. Through the iterative Procedure and by considering at the same time many actuator adjustments and related Profile measurements is a much more accurate one local assignment of the actuator positions possible to positions on the material web, so that a meaningful shrinkage curve can be determined can.

The calculation of the impact is made using cognitive values about the Behavior of the material web properties. The arithmetic Determination of the impact is compared with actually before and after an actuator adjustment Measured values obtained from a web property cross profile, in order to coordinate the knowledge values that the calculation results are as accurate as possible with the measured results on the impact to match.

In which a prediction of the place of impact the actuator adjustment is the procedure relatively easy to implement and optimize.

Alternatively or in addition a prediction about the Form of impact will be taken, for example about the extent of the impact at the impact location or the amplitude of the change in web properties at the place of impact. This procedure too is relatively easy to carry out and leads to make the prediction about the place of impact is very easy to optimize.

A method is particularly preferred in which such actuators are taken into account that anyway used to manufacture the material web and for setting the cross profile of the material web properties are needed. Such a thing The process is characterized in that there is none additional devices or actuators needs that the installation space of the facility Enlarge the production of the material web, the construction and increase production costs and if necessary also require additional maintenance. In addition, the ongoing production of the Material web not through an actuator adjustment disturbed, which is used only for measuring purposes. The ongoing production therefore remains unaffected.

A method in which the Actuators are only adjusted as much as during the production to correct the process disturbances through an automatic cross profile control is required. Larger adjustments would Disrupt production and reduce paper quality.

A method is preferred in which the predictions be gradually modified in such a way that First a general statement about the Behavior of the material web properties met which is particularly characterized by that even with a bad "noise to useful signal Ratio "still with good accuracy can be hit quickly.

A simple statement could be, for example: The The edges of the paper web are a certain amount shifted from the position they are in Machine should have at the measuring point if there is there would be no shrinkage and no lateral running. The two amounts of the shift are to be determined.

A first refinement of this statement would be, for example: The cross shrink is on the edges stronger than in the middle and the resulting Cross shrink cross profile has a bowl-shaped Contour whose amplitude is to be determined.

It can be seen, therefore, that with this method auxiliary devices for measuring the position of the edge section devices and the paper edges are eliminated can.

Furthermore, a method is preferred in which the Prediction of web properties determination of the transverse shrinkage behavior as accurate as possible includes.

Finally, a method is particularly preferred, in which an averaging of the results in the determination the cross shrink cross profile for a number of predictions and / or for a number of Actuator adjustments is carried out. A such averaging causes the error to occur the mathematical determination of the impact on a Minimum is reduced.

Further embodiments of the method result from the other subclaims.

The above task is also accomplished by a facility solved that mentioned in claim 20 Features includes. The fact that the computing unit Predictions or knowledge values about the behavior of the web properties at Adjustment of an actuator processed and based of these knowledge values and by means of an assignment rule calculates the impact, it is possible at any time, the place of change an actuator can be assigned to predict online and an exact cross profile of a material web property to determine and / or a lateral To determine the offset of the path.

Figur 1

ein schematisches Blockschaltbild einer Einrichtung zur Ermittlung der Auswirkung von Stellgliedverstellungen;

Figur 2

Diagramme zur Erläuterung des Verfahrens zur Ermittlung eines Querprofils;

Figur 3

einen schematischen Aufbau einer Papierherstellungsmaschine und

Figur 4

einen Zweischichten-Stoffauflauf zur Erzeugung einer Faserstoff-Bahn mit einem schematisch dargestellten Leitungssystem.

The invention is explained below with reference to the drawing. Show it:

Figure 1

a schematic block diagram of a device for determining the effect of actuator adjustments;

Figure 2

Diagrams for explaining the method for determining a cross profile;

Figure 3

a schematic structure of a paper manufacturing machine and

Figure 4

a two-layer headbox for producing a fibrous web with a schematically illustrated line system.

In the case of a material web, different material web properties can be used be detected, for example the weight per unit area, the moisture, the transverse shrinkage, the fiber layer, the roughness, the strength, the Elasticity, opacity, smoothness, filler content, the thickness, the formation. As a cross section are recorded across the width of the web Called measured values.

It is assumed that for the production of a material web a water-pulp suspension via a headbox, which may also include fillers comprises, introduced into a wire section (former) and that the fibrous web formed there -for example paper-web- over a press section Dryer section is fed. The headbox can be designed so that actuators intended to influence the material properties are. For example, the water-fiber suspension a so-called secondary material flow are supplied, for example from dilution water or from a second type of paper stock, but with a different, preferably less Consists of consistency. The transverse distribution in Headbox is through multiple sectional feed lines set, each one as an actuator have designated control valve. At the Merging of the water-fiber suspension with the secondary material flow can in turn be used as actuators designated mixing valves may be provided. Actuators of the type mentioned here can also in other places on the paper machine, for example in a steam box in the press or dryer section or in an aftertreatment facility, for example in one Coating machine can be provided.

In Figure 1 is a device 1 for determination the effect of actuator adjustments, which here in addition to determining a Cross-shrink cross-profile and to record the lateral course serves. The material web 3 is shown from left to right by the representation in Figure 1 directed, which is indicated by an arrow is. A headbox is dashed on the left in FIG 5 drawn, the numerous across the Material web 3 has distributed actuators 7, only one of which is shown here. The others are outside the display level of Figure 1. The actuators 7 are via a control line 9 connected to a computing unit 11. In a distance to the headbox 5 is at any Location of the device for producing the Material web 3 a measuring device 13 for determination of web property cross sections. This can for example at the end of a paper making machine be arranged beyond the dryer section. However, it is also possible to use several such measuring devices inside the paper making machine to provide.

The measuring device 13 is via a measuring line 15 connected to the computing unit 11. Via an input line 17 can add -bottom more detailed dealt with - information about the cross section the material web 3 into the computing unit 11 can be entered. Be on an output line 19 the calculation results of the computing unit 11 are output.

1 shows a schematic bar diagram 21 are drawn, indicated on the basis of this supposed to be the different across that of the web 3 distributed actuators 7 different Have settings.

In addition to the measuring device 13 is a schematic Diagram 23 reproduces the one from the measuring device reproduces the measured signal. Corresponding the various settings of the actuators 7 and other process parameters result different measurement signals across the web width. The jagged line indicates that the Measurement signal strongly from measurement noise and process disturbances is superimposed.

The relationship between the setting of various actuators 7 and the measurement signal in diagram 23 are explained in more detail.

For this purpose, several diagrams are shown one above the other in FIG. In the uppermost diagram 1, the distance x of an actuator 7 to an imaginary reference line 25, which for example lies outside the paper web and runs along the paper-making machine, is indicated, which is shown here in broken lines. In the second diagram below, from above, a number of actuators indicated by crosses are shown. An actuator 7/1 is located, for example, at a distance x ₁ from this reference line 25 and here has a "positive" setting with a corresponding "width effect". Another actuator 7/2 has a distance x ₂ from the reference line 25. Here, purely by way of example, a "negative" setting with a corresponding "width effect" of this actuator is assumed. The "width effect" here denotes the width of the effect of the actuator adjustment at the point of impact.

Below the second diagram, in which the individual actuators are marked by crosses, the expected reaction in the transverse profile of the material web 3 or the predicted effect is shown in the third diagram marked as curve a. Due to the "positive" settings of the actuator 7/1, depending on which web property influences the actuator, a locally increased moisture or a locally greater material thickness could result in the cross profile, which leads to a locally increased basis weight, also known as the base weight. Correspondingly, due to the "negative" setting of the actuator 7/2, a reduced moisture or reduced material thickness would occur at a location which is assigned to this second actuator. In curve a, it is assumed in the context of a first prediction or first hypothesis based on knowledge values that the locations x ' ₁ and x' ₂ corresponding to the setting of the actuators 7/1 and 7/2 or positions of the answers or effects in the material web or paper web exactly correspond to the actuator positions x ₁ and x ₂ . The expected response positions or impact locations are therefore at a distance x ' ₁ or x' ₂ from the reference line 25. This is indicated here by arrows.

A change in the actuators 7/1 and 7/2, which according to the first diagram are located at the positions x ₁ and x ₂ , results in a change in the transverse profile detected by the measuring device 13 shown in FIG. 1, which is shown in curve b is reproduced, and that was shown in Figure 1 in diagram 23. It is also indicated in FIG. 2 that the measurement signal corresponding to the cross section is superimposed by measurement noise and process disturbances. A local increase in the cross profile, which can be attributed to an adjustment of the actuator 7/1, is recognizable, as is a local decrease in the cross profile, which is based on a change in the actuator 7/2. However, it becomes clear that, for example, as a result of a transverse shrinkage when the web is drying or a lateral run of the web, the reaction in the cross profile is shifted from the reference line 25 once to the right and once to the left. The shift in the reaction is indicated here by ▵x ₁ and ▵x ₂ .

It turns out that the prediction shown in curve a that the reaction in the transverse profile, that is to say the place of impact exactly corresponds to the actuator positions, does not exactly apply. There are therefore made several further predictions based on modified knowledge values with regard to the expected effect in the cross profile. The best prediction is shown in curve c. It can be seen that the response of the actuator 7/1 takes place approximately at the location x " ₁ and that the response to an adjustment of the actuator 7/2 occurs approximately at the location x" ₂ . The underlying knowledge values were optimized so that the correspondence between the measurement signal in curve b and the location calculated on the basis of the prediction according to curve c is optimal. Additional knowledge values or knowledge values that led to the first prediction a can be input into the computer 11, for example via the line 15 shown in FIG. 1. However, the computer can also generate the knowledge values completely automatically and use them to calculate predictions regarding the effects. Knowledge can be used a priori for the initial cognitive values and for the rules for coordinating the cognitive values or can be entered into the computer.

• Es gibt ein seitliches Verlaufen der Bahn, dessen Amplitude zu bestimmen ist.
• Es gibt einen Querschrumpf der Bahn während des Fertigungsprozesses, der zunächst an allen Orten der Bahn als gleich groß (prozentual) angenommen wird, und dessen Größe zu bestimmen ist.

It is possible that the knowledge values about the locations of the effects of actuator adjustment are initially based only on the following simple statements:

• There is a lateral run of the path, the amplitude of which has to be determined.
• There is a transverse shrinkage of the web during the manufacturing process, which is initially assumed to be the same size (percentage) at all locations on the web, and the size of which has to be determined.

• Der Querschrumpf ist an den Rändern stärker als in der Mitte und das sich ergebende Querschrumpf-Querprofil hat eine schüsselförmige Kontur, deren Amplitude zu bestimmen ist.
• Der Querschrumpf tritt auf der einen Maschinenhälfte stärker auf als auf der anderen. Die Größe des Unsymmetriefaktors ist zu bestimmen.

The knowledge values can be refined step by step in an advanced process step, for example by statements:

• The cross-shrink is stronger at the edges than in the middle and the resulting cross-shrink cross-section has a bowl-shaped contour, the amplitude of which has to be determined.
• Cross shrinkage occurs more strongly on one half of the machine than on the other. The size of the asymmetry factor must be determined.

The basic principle of that addressed here is therefore from FIG Procedure for determining a cross-shrink cross profile clear. So first of all when adjusting an actuator, here the Actuator 7/1 or 7/2, using one first prediction, the expected response in the cross profile calculated (see curve a). In curve a for example, the prediction is made that the position of the answers in the cross section the locations that are also the actuator positions corresponds. It turns out that there is a deviation between the calculated value of curve a and the actual measured value of curve b is given, caused by cross shrinkage or lateral run the web is caused.

The knowledge values or the prediction are therefore modified and the expected reaction is recalculated. The calculation made using the best prediction is shown in curve c. The present prediction assumes that the response to the adjustment of the actuator 7/1 takes place at the location x " ₁ and that the response from the actuator 7/2 takes place at the location x" ₂ . The following relationship is assumed: x "= x '+ ▵ x. It turns out that with the prediction c chosen here, the deviation between the measurement signal shown in curve b and the calculated signal of curve c is very small.

One way to get to curve c corresponding to this prediction would be to test many hypotheses about locations x " ₁ and x" ₂ that differ only slightly and to find the hypothesis that best matches the curve b select the measurement signal shown.

The procedure is refined by a priori knowledge of shrinking behavior, for example and the course of the path in the calculation to incorporate the hypotheses. This can the number of hypotheses to be examined clearly be reduced.

The following results from what has been said for FIG. 2: If a deviation, for example, of the local basis weight from a required dimension, is found at point x " ₁ , then the manipulated variable resulting from the deviation must be supplied to the actuator 7 that is at a distance x ₁ = x " ₁ -Δx ₁ from the reference line 25. It is therefore possible in a simple manner to assign a local material web property to an actuator and thus to take into account a transverse shrinkage or a lateral run of the web.

It is obvious that this is described Procedure for an online determination of a lateral course of the paper web is suitable.

As a particularly suitable calculation method for arithmetical determination of the degree of agreement the curve b and c has the procedure the correlation calculation. Another measure would be the mean square deviation of the two Curves.

Preferably in the method described here only such actuators are taken into account to the usual ongoing setting of the Cross profile are required. So it can here, for example, are actuators that affect the headbox. So it can be as Actuator a control valve or a mixing valve in the headbox supply lines become. But it is also conceivable that as actuators Facilities are used, for example the heating capacity of the dryer section in zones can influence the web width differently. The procedure described here or Establishment for determining the impact of a Actuator adjustment is in all cases can be used in the same way. According to what has been said here can therefore also be used actuators that the weight per unit area, the moisture, the density or another property of material respectively Affect paper web.

When choosing the predictions or hypotheses to determine the different curves in Figure 2 is preferably carried out step by step. First, a prediction is made where on the one hand only a few sizes can be determined and on the other hand, a lot of manipulated values and profile measurements be available. This applies, for example for a prediction of the total transverse shrinkage the paper web and the cross to the paper web measured- place in the cross profile where shows the change in an actuator. In the Such prediction can be taken into account a reliable determination of the locations very quickly happen, even if the manipulated variables are very small Are compared to process noise.

A further prediction can be a little more accurate Determination of the shrinkage behavior made become. Example: Assume that there is a Production machine 50 cross-section actuators 150 measured cross-profile data values. With everyone Intervention of a cross profile control are usually all actuators by a small amount adjusted to compensate for the process disturbances. After the adjustment and after comparing the Stand cross profiles before and after the adjustment So 150 + 50 information is available to be evaluated can be. For example, only one Statement about the total shrinkage and the amount made a statement about the lateral course of the web are only two pieces of information respectively two numerical values from the available standing 200 information to determine. This is even with a very large process and measurement noise still possible. The more statements are made must, for example, additionally over the width of the Process response to an actuator adjustment, the more the "noise to useful signal ratio" becomes less favorable, so that the information too Numerical values that are determined with a Errors.

It is preferred to have the most accurate possible cross-shrink cross-section to be able to calculate after everyone Adjustment of an actuator 7 the cross-shrink cross-section determined with the aid of the computing unit 11, by comparing the predicted impact with the impact actually measured and the knowledge values based on the deviations be modified until there is a better one or best possible match between predicted and calculated impact.

To further increase the accuracy of the process are special processes for the preparation of the Cross-section measurements before and after the adjustment conceivable. Common procedures would be, for example Use of filter algorithms around the noise component to reduce. If a statement about the temporal Course of the noise or statistical parameters can be taken, for example under Using measured quantities that cause the noise or which arise on the side, it is possible the measured cross profile subsequently partially from the known part of the noise again free, or to adjust the filter optimally.

Local transformations are also promising and weights of the measured profiles with the Aim to add those proportions in the measured profile dampen that for determining the impact of Actuators are not very profitable.

In order to be able to reduce the errors based on measurement noise and process disturbances to a minimum, the calculated results x " _n , as shown, for example, in curves a and c in FIG. 2, are determined taking into account many actuator adjustments. The fact that a number of Predictions and a large number of actuator adjustments are taken into account, it is possible to largely eliminate the measurement errors, even if the amplitude of the actuator adjustments is very small.

It makes sense in the sense of the proposed gradation only as many consecutive in time To use positioning operations as necessary to sufficient accuracy for the desired statement to achieve.

For example, for the determination of the total shrinkage little or no averaging required. So the total shrinkage is within very few adjustments of all actuators determined exactly. A finer resolution of the cross-shrink cross profile accordingly needs more information from more pretenses. The investigation accordingly takes longer.

Instead of averaging, as suggested here of course, more complex filter or estimation algorithms can be used.

The device shown in Figure 1 only a measuring device 13. However, it is also possible within a manufacturing device respectively Paper machine several measuring points Direction of conveyance of the material web seen - one behind the other to arrange. It can then be the cross-shrink cross-section in several places within the machine can be calculated, so that conclusions can be derived from how the transverse shrinkage changed between different measuring points Has.

Another application of the invention is the influence of a special treatment of the material web in a suitable after-treatment facility, for example sizing or rewetting a paper web, on the cross shrink on-line to observe. Then are out of the shrinkage change other process variables, for example glue pick-up of the paper, derivable. These process variables can then be used to determine further intervention be used.

From the description of Figures 1 and 2 is without further apparent that the procedure to determine a cross-shrink cross profile Material web property in the manufacture of a Fiber web from a water-fiber suspension great advantages result: It is straightforward possible at various points on a paper making machine across the width of a web of material capture and target different properties certain actuators of the paper making machine to address the web properties to influence specifically. To this Cross sections for the basis weight, the moisture, the transverse shrinkage and / or the thickness the path is precisely adjusted and influenced, for example, even the cross-shrink cross profile targeted by moistening the web locally to be changed.

Other influencing factors on shrinkage that are targeted Production process parameters, for example, could be adjusted in the area of the wet part, the press, the dryer section. Be exemplary called here: local temperature distribution of the paper web during the drying process that Moisture cross profile within the drying process or right after the press, the fiber orientation, locally varying degrees of disability Shrinking process by suitable different strong fixation of the web in the web transverse direction. Other influencing factors are conceivable. What influencing factors are practically usable, will look after one longer use of the presented method for on-line Measurement of cross-shrink cross-section automatically point out.

In modern papermaking machines they are Actuators, especially the control valves for Setting the specific basis weight in large number at a very short distance from each other intended. It is therefore extremely important, exactly to be able to predict which actuator to influence a local web property must be addressed. This is exactly what with the The procedures described here and the details shown facility possible without further notice.

Applications of the invention are in following explained with reference to Figures 3 and 4.

Figure 3 shows a paper making machine 31 with a headbox 33 that matches the headbox 5 according to FIG. 1 is comparable. Furthermore the papermaking machine 31 also has one sieve section 35 referred to as former, a press section 37 and a dryer section 39. This is adjustable with at least one zone Steam box 41 provided, with the help of that Cross profile of the material web 43, for example that Dryness cross profile can be influenced.

The paper making machine 31 also has a computing unit 45 which corresponds to the one in FIG computing unit 11 shown is comparable. The headbox 33 is with the computing unit 45 connected via signal lines 47 and 49, via the on the one hand, for example, the actual position of various Actuators of the headbox 33 detected can be and which on the other hand serve Forward control signals to the actuators.

The paper making machine 31 is also still provided with a measuring device 51 which the in Figure 1 corresponds to the measuring device 13 shown and the 53 measurement signals via a signal line the computing unit 45 delivers. This can be done with a Monitor 55 be provided on which both measuring and control signals can also be displayed.

From Figure 3 it is clear that with the help of the measuring device 51 cross profiles of the material web 43 detected can be. A particularly important field of application the invention is the so-called basis weight cross section control, with the help of one as uniform a mass distribution as possible the material web is to be adjusted. If with the help of the measuring device 51 deviations in the desired basis weight of the material web, i.e. deviations in the basis weight cross-section, can be determined via the computing unit 45 certain actuators of the headbox 33 so can be controlled that the desired thickness the material web or the desired one Weight per unit area. So it's a local one Influencing the amount of fibers possible, which over the Headbox 33 is delivered.

It is also possible with the aid of the computing unit 45 to control the steam blower box 41 so that individual zones of the material web 43 more or less be heated. In this way, one can specific moisture cross profile of the material web 43 set and ultimately that too Control the cross-shrink cross-section in a targeted manner.

It becomes clear after all that with the help of here described invention a cross profile of a material web can be influenced because the local Material web properties through a targeted Adjustment of various actuators, be it from Actuators in the headbox or in a steam blower box, can be influenced.

With the help of FIG. 4, the special important application of the invention be, namely on the basis weight cross profile control or on the hiring of a predetermined basis weight cross-section of a material web on a headbox.

Figure 4 shows a two-layer headbox purely by way of example 33, together with a schematic shown line system for feeding various Fibrous suspensions.

The headbox 33 comprises a nozzle 57 which is known in the art Way by two yourself across the width of the Papermaking machine 31 extending current guiding walls 57a and 57b is limited. The power supply walls 57a, 57b are known each Turbulence generator 59 with a medium stationary Partition 61 connected. At the outlet end the partition 61 is in turn by means of a joint 63 a slat 65 pivotally attached. Deviating the slat can also be rigidly attached to the partition 61 be attached.

A first main stream, which consists of a first Paper grade exists, passes through a cross distribution line 67 and branched off from one of them Row of sectional feed lines 69 to one of the two turbulence generators 59.

Deviating from the illustration chosen in FIG. 4 can be in each of the sectional feed lines 69 an actuator designed as a volume flow controller be provided.

A second main stream consisting of one other paper stock, comes through a cross distribution line 71 and branched off from one of them Row of sectional feed lines 73 to the other Turbulence generator. If necessary, that basis weight cross section of the to be manufactured Paper or material web corrected is a third cross distribution line 75 provided, via which a so-called secondary material flow is fed. This exists, for example from dilution water or from a second Kind of paper, but with another, preferably lower consistency. From the cross distribution line 75 are several sectional feed lines 77 with one each designed as a control valve 79 branched off.

Each of the feed lines 77 thus carries a controllable one sectional side stream to one Mixing point 81, where it with one of the sectional Main material flows is mixed.

In the case of a three-layer headbox you will the line system 71 to 77 with the control valve 79 and the mixing points 81, preferably the middle one Assign shift.

Deviating from the illustration in Figure 4 could In addition, the following are also provided: Others Feed lines for individually controllable sectional Secondary material flows could be in the sectional Feed lines 69 for the first main stream flow into.

Already from the schematic diagram shown in Figure 4 it becomes clear that the actuators in be arranged relatively close to each other can. While with conventional types of headbox, their aperture adjustment in particular is made with adjusting spindles, the influence of Adjustment of an adjusting spindle to the basis weight cross section more than four times the actuator distance corresponds, the adjustment affects of an actuator influencing the secondary material flow on the basis weight cross section in about Range of two and a half times the actuator distance out.

With the help of the invention it is possible, despite the short distance of the actuators, at a local Deviation of the cross section of the material web, to address exactly the actuator with its help the desired cross profile can be set. there due to the relatively high density of the Actuators a significantly improved paper quality can be achieved.

Overall, it follows from the description that the Procedure for determining the impact of a Actuator adjustment is easy to carry out, and that doing the process of making a web of material is not disturbed in any way, in particular no disadvantages based solely on the measurement stand up for the web properties. It only needs predicting the expected impact based on knowledge. By comparison the theoretically predicted impact with measured Railway Properties Cross Profile Values Can made an improvement in knowledge until the prediction with the measured values largely coincides.

The method is suitable for prediction on the one hand about the place of impact of an actuator adjustment but also on the other hand about the course of the web properties near the place of impact, so about the form of impact. The predictions about the form of the impact, i.e. across the width of the Impact at the point of impact and via the amplitude changes in web properties on Impact, are measured by comparison with Values gradually improved. In this way, an overlay of the Effect of an actuator adjustment with the effects neighboring actuator adjustments predicted become. It turns out that the Range of effects of adjusting an actuator is often so wide that it spans several Actuators extends.

Using the procedure to determine the impact the actuator adjustments can, according to The above, both a cross shrink cross profile a material web can be determined exactly as well the lateral run of the material web within the manufacturing machine. The cross shrink cross profile is an important quality parameter the generated web of interest, on the other hand, enables it also draws conclusions about the function of the Production machine.

It shows that the impact is based on knowledge be roughly predicted first can and that when adjusting several spindles and in determining the impact of the adjustments the prediction about the impact so can be coordinated that both a cross-shrink cross-section as well as a sideways run the web can be detected.

In particular, that after each adjustment an actuator pre-determines the impact and is checked by measurement, you get an abundance of measured values so that the knowledge values are optimal can be coordinated. The multitude of investigations the best way to understand the effects implement an automatic execution of the method, so that finally an online determination the impact is possible.

From the above, the goals of the described Cross shrinkage measurement clear: First, should a cross profile control are made possible with their Help assign the actuator positions to the measuring element positions is given, so that the for the optimal influencing of the cross profile to be addressed actuator can be located.

In addition, a technological process assessment should be possible, for example in the dryer section uniform drying across the web width or even fiber orientation in the wet end and an even longitudinal to transverse tensile strength ratio over the web width or the like.

When it comes to technological process assessment, the exact curve shape of the cross-shrink cross-section is significant. When realizing a cross profile control the error must be at every actuator position be less than 0.5 times the actuator distance, so that regulation is possible. In the event of an error, less than 0.2 times the actuator distance a sensible regulation can be realized.

Claims (23)

1. Process for determining the effect of an adjustment to final control elements (7) which are employed in the production of a material web (3), are arranged distributed over the web width and influence the properties of the material web, where, during the adjustment of at least one final control element (7), a prediction is made about the effect of the adjustment to the final control element, derived from empirical values relating to the behaviour of the web property transverse profile in the case of a change to final control elements (7), at least one web property transverse profile is measured before and after the adjustment to the final control elements (7), the prediction relating to the effect of the adjustments to the final control elements is compared with the measured effect and the existing empirical values are modified until the result is better agreement between predicted and measured effects, characterized in that a prediction is made about the effect locations of adjustments to final control elements and/or a prediction is made about the geometric shape of the effects.
2. Process according to Claim 1, characterized in that a prediction is made about the geometric shape of the effects, and the width of the effect at the respective effect location is predicted.
3. Process according to Claim 1 or 2, characterized in that a prediction is made about the geometric shape of the effects, and the amplitude of the change in the material web properties at the respective effect location is predicted.
4. Process according to one of the preceding claims, characterized in that the transverse shrinkage transverse profile is determined from the effect locations.
5. Process according to one of the preceding claims, characterized in that the lateral course of the material web (3) from the effect locations is determined.
6. Process according to one of the preceding claims, characterized in that account is taken only of the adjustment to the final control elements (7) which are needed for the continuous setting of the web property transverse profiles.
7. Process according to one of the preceding claims, characterized in that the adjustment to the final control elements (7) is selected only in the manner which is needed for the continuous setting of the web property transverse profiles.
8. Process according to one of the preceding claims, characterized in that the final control elements (7) are adjusted by means of an automatic web property transverse profile control system.
9. Process according to one of the preceding claims, characterized in that the process is carried out automatically by a control computer (11).
10. Process according to one of the preceding claims, characterized in that the process is carried out online.
11. Process according to one of the preceding claims, characterized in that account is taken of the adjustment to the final control elements (7) in order to influence grammage, moisture content and/or density of the material web (3).
12. Process according to one of the preceding claims, characterized in that the empirical values relating to the behaviour of the material web properties are initially obtained on the basis of general, simple statements about the behaviour of the material web properties.
13. Process according to one of the preceding claims, characterized in that the empirical values are modified step by step, first of all the most general, simple statement about the behaviour of the material web properties being made and subsequently a prediction being made which reproduces the actual transverse profile of the material web (3) as accurately as possible.
14. Process according to one of the preceding claims, characterized in that following each adjustment to the final control elements (7), the process according to one of Claims 1 to 13 is carried out.
15. Process according to one of the preceding claims, characterized in that averaging or filtering of the results is carried out when determining the effect for a number of predictions and/or for a number of chronologically successive adjustments to final control elements and/or for a number of individual transverse profile measurements.
16. Process according to one of the preceding claims, characterized in that the degree of agreement of measurement and prediction is determined by computation, preferably by means of a correlation calculation or by evaluating the mean square deviation.
17. Process according to one of the preceding claims, characterized in that the determined effects of adjustments to final control elements are taken into account during the production of a material web (3), such as in particular a paper or board web, from a water/fibrous material suspension, in which a number of final control elements (7) which are arranged distributed over the web width and influence at least one of the web properties (for example the specific grammage) are employed, and in which, by means of a measuring device (13), the transverse profile of the aforementioned web properties is measured and the measured values are used to obtain final control variables which act on the final control elements (7) in such a way that the desired web property transverse profile is established.
18. Process according to Claim 17, characterized in that the determined transverse shrinkage transverse profile is the basis for online monitoring and influencing the transverse shrinkage transverse profile itself.
19. Process according to Claim 17, characterized in that the transverse grammage profile is regulated by means of a sectionally adjustable quantity of fibrous material in a headbox (5).
20. Device (1) for determining the effect of the adjustment to final control elements (7) which are employed in the production of a material web (3), are arranged distributed over the web width and influence the properties of the material web, in particular for carrying out a process according to one of Claims 1 to 18, having a measuring device (13) for registering the transverse profile of a material web property, having final control elements (7) for influencing the transverse profile of the material web property, and having a computing unit (11) for determining the effect of an adjustment to a final control element, characterized in that, in the computing unit (11), empirical values relating to the behaviour of the material web properties during adjustment of a final control element (7) are processed in order to make a prediction about the effect locations of adjustments to final control elements and/or to make a prediction about the geometric shape of the effects.
21. Device according to Claim 20, characterized in that the computing unit (11) determines the effect online by using the empirical values.
22. Device according to Claim 20, characterized in that a number of measuring devices (13) are provided one behind another in the running direction of the material web.
23. Device according to one of the preceding claims, characterized in that the final control elements (7) are provided for the production of a material web (3) such as, in particular, a paper or board web.

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