Control of at least one component of a press and / or drying section of a paper machine

Abstract

A method for controlling at least one component of a press and / or dryer section of a paper machine comprises the repeatedly repeated steps: varying (S10) a first control variable of a first component of the press and / or dryer section to approach different operating points of the paper machine, determining (S20) values ​​of a quality criterion for operating points approached in the process, determining (S30) a first direction of a shift of the first control variable in which the quality criterion is expected to improve, on the basis of these determined values ​​of the quality criterion, and shifting (S10) the first control variable in the first direction.

Description

[0001] The present invention relates to a method and a control system for controlling at least one component of a press and / or drying section of a machine for producing paper, cardboard, board or the like ("paper machine"), to such a paper machine and to a computer program or software.

[0002] Computer program product for carrying out a method described here.

[0003] An object of an embodiment of the present invention is to improve the operation of a paper machine and / or a product produced thereby.

[0004] This object is achieved by a method having the features of claims 1 and 8, respectively. Claims 9-11 protect a control system, a paper machine, a computer program, or a computer program product for implementing a method described herein. The subclaims relate to advantageous developments.

[0005] According to one embodiment of the present invention, a paper machine, which in the present case is understood to be a machine, in particular a plant, which is designed or used for producing fibrous webs from paper, cardboard, paperboard or the like, has a device or assembly which in turn a press section which dewaters the fibrous web under mechanical pressure or is designed or used for this purpose and preferably has one or more press nips; and / or a drying section, preferably downstream of or downstream of the press section, which thermally removes (further) water from the fibrous web or is designed or used for this purpose and preferably has one or more drying cylinders; and is therefore referred to herein as a "press and / or drying section". Accordingly, a press and / or drying section within the meaning of the present invention can in particular be such a press section or such a drying section or a combination of such a press section and such a dryer section. In addition, the paper machine can, in a manner known per se, have a wire section upstream of the press and / or dryer section and / or a headbox upstream of the press and / or dryer section or optionally the wire section and / or a so-called approach flow system upstream of the press and / or dryer section or optionally the wire section or optionally the headbox for providing, cleaning and / or diluting a starting material for the paper machine, preferably a fiber suspension, and / or a processing section downstream of the press and / or dryer section, which preferably has a reel, in particular can be

[0006] According to one embodiment of the present invention, the paper machine has a control system that controls at least one component of the press and / or dryer section, referred to herein as the first component, or is configured or used to do so. The terms "first," "second," and the like do not represent any limitation of generality, in particular, they do not indicate a position, priority, or the like.

[0007] According to one embodiment of the present invention, a method for controlling one or more components of the press and / or dryer section of the paper machine comprises the steps, which are repeated several times, in one embodiment continuously: Varying a (first) control variable of the first component of the press and / or dryer section to approach different working or operating points of the paper machine; determining values ​​of a quality criterion for the operating points approached in the process; determining a (first) direction of a shift of the first control variable in which the quality criterion is expected to improve, in one embodiment of a gradient of the quality criterion, a sign of the shift, or the like, based on these determined values ​​of the quality criterion; and shifting the first control variable in the first direction.

[0008] One embodiment of the present invention is based on the recognition that model-based control of a component of a dryer section, and particularly of a press section of a paper machine, is difficult due to the process being difficult to model and constantly changing, particularly with varying and difficult to capture environmental conditions, starting materials, mechanical wear, and the like. The underlying idea is to sample a characteristic curve field of a quality criterion (continuously, quasi-continuously, or time-discretely) by varying the operating point of the paper machine (by varying the first control variable). This makes it possible to determine, in particular to estimate, orto calculate in which the quality criterion is likely to improve, in one embodiment to determine, in particular to estimate or calculate a gradient of the quality criterion, a sign of the shift or the like. Then the operating point of the paper machine is shifted in this first direction (by correspondingly shifting the first control variable), which should generally improve the quality criterion. In one embodiment, during this shifting of the operating point or the corresponding shifting of the first control variable, this shift is in particular superimposed and / or on a smaller scale compared to this shift, and / or in the (thereby approached) new operating point or at the corresponding new value of the first control variable, the operating point of the paper machine is varied further or again (by further or renewed variation of the first control variable). In this way, the family of characteristics can be varied again orat the respective current operating point. Now a (new first) direction of a shift of the first control variable is determined again. The operating point of the paper machine is then shifted in this (new first) direction (by shifting the first control variable accordingly). In one embodiment, these steps are repeated several times in normal or production operation, preferably continuously, preferably also at a quasi-stationary operating point, so that when the conditions change, a temporarily optimal operating point that has been reached once is shifted to or in the direction of a new (then optimal) operating point. In this way, in an embodiment without a model of the process, the control of the first component can be continuously adapted to the real process and improve it.

[0009] In a particularly simple embodiment, the first direction can be determined, for example, on the basis of a comparison of at least two determined values ​​of the quality criterion J and the corresponding values ​​of the first control variable S 1 : if the quality criterion has a value J(t 1 ) for a value S 1 (t 1 ) of the control variable S 1 and a value J(t 2 ) that is better than J(t 1 ) for another value S 1 (t 2 ) of the control variable S 1 , the first direction can be a direction away from the value S 1 (t 1 ) towards the value S 1 (t 2 ). Conversely, if the quality criterion for the value S 1 (t 1 ) of the control variable S 1 has a value J(t 1 ) and for the other value S 1 (t 2 ) of the control variable S 1 has a value J(t 2 ) that is worse than J(t 1 ), the first direction can be a direction away from the value S 1 (t 2 ) towards the value S 1 (t 1 ).If the quality criterion has the same value for both values ​​S 1 (t 1 ), S 1 (t 2 ) of the control variable (within a predetermined tolerance), the first direction can be zero or arbitrary and a shifting of the first control variable (correspondingly) is omitted until an improvement is again determined. In general, in one embodiment of the present invention, a shifting of the first control variable in the first direction or, if appropriate, an overlay of the - still carried out - variation with such a shifting of the first control variable in the first direction is omitted if or as long as (within a predetermined tolerance) no improvement is determined between the approached operating points for which the quality criterion is determined, or only the variation is continued.

[0010] The invention is expressly in no way limited to this simple example, but can also be implemented in various other ways. Thus, in a particularly preferred embodiment, the values ​​of the quality criterion are demodulated, preferably after a high-pass filter, preferably by multiplication by a periodic function, for example a sine function; the result is integrated, preferably after a low-pass filter and / or amplification, preferably multiplication by a gain factor; and the result is then modulated again, preferably by adding a corresponding periodic function, for example a sine function, with the same periodicity as during demodulation, to the current value of the control variable. This means that an improvement in the quality criterion due to a variation of the control variable in one direction automatically leads to a further shift of the control variable in that direction.In general, in a particularly preferred embodiment of the present invention, the first component is controlled based on extremum-seeking control, preferably by an extremum-seeking controller, or the first control variable is varied and shifted, determined, and / or adjusted using extremum-seeking control. As is particularly clear from this, controlling a component by (shifting) a control variable can include determining this control variable by means of a closed-loop control. Accordingly, "control" or "regulation" is not understood here as the opposite or different from "regulation" or "control," but can, on the contrary, encompass such "regulation" or "control" or refer to the "control" in "feedback control." In one embodiment, a shift within the meaning of the present invention is a displacement or so-called "shifting," preferably on a larger scale than variation.An improvement of a quality criterion within the meaning of the present invention can, as is generally customary, in particular be an increase in the value of a quality criterion if larger values ​​are more advantageous or desirable, or a decrease in the value of a quality criterion if smaller values ​​are more advantageous or desirable. Accordingly, an extreme value of an extreme value control can, in particular, be a maximum or minimum, in particular at least a local one. For example, if the quality criterion is defined as the magnitude of a line load and its reduction is desired because this reduces energy consumption and mechanical stress, an improvement of such a quality criterion can comprise, in particular be, a reduction, preferably minimization.If, again purely by way of example, the quality criterion is defined as the inverse or negative amount of a line load or the like, an improvement of such a quality criterion can accordingly comprise, in particular be, an enlargement, preferably maximization.

[0011] In one embodiment, the first component has one or more press nips of the press section (the press and / or dryer section), preferably one or more press roll pairs, particularly preferably one or more shoe presses, and can in particular consist of these. In particular, due to the significant influence of the press nips on operation, in particular energy consumption, and the fibrous web, in particular its mechanical stress, and due to the process dynamics, in particular the reaction time of the process to changes in the pressing pressure of the press nips, the present invention is particularly advantageous for controlling one or more press nips.

[0012] In one embodiment, the first component comprises a felt conditioning device of the press section or dryer section (the press and / or dryer section), in a further development at least one felt suction device for suctioning a felt that is guided circumferentially and together with the fibrous web through the press or dryer section, and / or at least one spray pipe for cleaning and / or moistening the felt and / or at least one tensioning roller, and can in particular consist of these. In particular due to the direct contact of the felt with the fibrous web, the mechanical stress and the process dynamics, in particular the reaction time of the process to changes in felt conditioning, the present invention is also particularly suitable for controlling (also) a felt conditioning device of the press section.

[0013] In one embodiment, the first component comprises, and can in particular consist of, at least one steam blow box in the press and / or dryer section for applying steam to the fibrous web. Due in particular to the highly complex process dynamics and interactions with other components, the present invention is also particularly advantageous for controlling (also) at least one steam blow box in the press section.

[0014] In one embodiment, the first component comprises, and may in particular consist of, one or more drying cylinders of the drying section (the press and / or drying section), preferably one or more steam-heated drying cylinders. In particular, due to the significant influence of the drying cylinders on operation, in particular energy consumption, and the fibrous web, and due to the process dynamics, in particular the reaction time of the process to changes in the operating point of one or more drying cylinders and their interaction with other components, the present invention is particularly advantageous for controlling (also) one or more drying cylinders of the drying section.

[0015] In one embodiment, the first component comprises one or more dewatering elements of the press and / or dryer section, preferably: one or more dewatering elements for reducing the water content ("dewatering") of a felt that is guided circumferentially and together with the fibrous web through the press or dryer section ("felt dewatering element"), wherein such a felt dewatering element may in particular comprise, or be, a tube suction device or the like and / or the or one of the felt conditioning devices; and / or one or more dewatering elements for dewatering or reducing the water content of a or the fibrous web that is guided through the press or dryer section ("fibrous web dewatering element"), can consist in particular of this or these elements. Due to the highly complex process dynamics and interactions with other components, the present invention is also particularly advantageous for controlling at least one dewatering element.

[0016] Two or more components of the press and / or dryer section can be controlled according to the invention with particular advantage. Additionally or alternatively—in addition to the first component and optionally one or more other components of the press and / or dryer section—one or more other components of the paper machine upstream of the press section and / or one or more other components of the paper machine downstream of the dryer section can be controlled according to the invention or in the manner described here. One or more such components are referred to herein, without restriction of generality, as a "second component." As already explained, in a particularly preferred embodiment, the second component(s) or at least one of the second components is also a component of the press and / or dryer section.The control system according to the invention is particularly advantageous for controlling components of the press and / or dryer section, particularly due to its influence on the process and / or its responsiveness. In a likewise particularly advantageous embodiment, the second component, or additionally or alternatively at least one of the second component(s), is a component located upstream of the press section or downstream of the dryer section. In one embodiment, this allows the entire process to be controlled particularly advantageously.Thus, "controlling at least one component of a press and / or dryer section of a paper machine" within the meaning of the present invention can expressly comprise, in particular be, "controlling at least two components of a press and / or dryer section of a paper machine" and / or "controlling at least one component of a press and / or dryer section of a paper machine and (also) at least one component upstream of the press section of the paper machine and / or at least one component downstream of the dryer section of the paper machine".

[0017] Accordingly, in one embodiment, the method for one or more second components of the paper machine, in particular the press and / or dryer section, comprises (respectively) the steps: Varying a second control variable of the (respective) second component to approach different operating points of the paper machine; determining values ​​of the quality criterion for the operating points approached in the process; determining a second direction of a shift of this second control variable, in which the quality criterion is expected to improve, based on these determined values ​​of the quality criterion; and shifting this second control variable in this second direction.

[0018] The following explanations apply accordingly to (one of) the second component(s) both to the components upstream of the press section and downstream of the dryer section and in particular to second components of the press and / or dryer section itself, especially if only the latter is mentioned.

[0019] In one embodiment, when the (respective) second control variable is shifted, in particular this shift is superimposed and / or on a smaller scale compared to this shift, and / or at the new operating point reached by the shift or at the corresponding new value of the (respective) second control variable, the operating point of the paper machine is varied further or again (by further or renewed variation of the second control variable) as described above with reference to the first control variable. In general, in a particularly preferred embodiment of the present invention, the or one or more of the second component(s) is / are controlled on the basis of an extreme value control, preferably by an extreme value controller, preferably together with the first component in or the same extreme value control or by the same extreme value controller or also in a separate or dedicated extreme value control or by a separate orown extreme value controller, or the or one or more of the second control variable(s) are varied and shifted or determined and / or set using an extreme value controller, preferably the same or its own.

[0020] In one embodiment, the first component is a component of the press section and the or at least one of the second component(s) is another component of the press section (the press and / or dryer section). In a further development, the first component has one or more press nips of the press section and the or at least one of the second component(s) has one or more other press nips or a felt conditioning device or at least one steam blow box of the press section. In one embodiment, the first component has one or more press nips of the press section, at least one of the second components has one or more other press nips and at least one other of the second components has a felt conditioning device or at least one steam blow box of the press section.In particular due to the large proportion of the components, in particular press nips, of the press section on the operation, in particular the energy consumption, and the fibrous web, in particular its mechanical stress, and due to the process dynamics, in particular reaction time and corresponding interactions, the present invention is particularly advantageous for the control of at least two components, in particular press nips, of the press section.

[0021] In one embodiment, the first component is a component of the drying section and the or at least one of the second component(s) is another component of the drying section (the press and / or drying section). In a further development, the first component has one or more drying cylinders of the drying section and the or at least one of the second component(s) has one or more other drying cylinders of the drying section. In particular, due to the large impact of the components, in particular drying cylinders, of the drying section on operation, in particular energy consumption, and the fibrous web, and the process dynamics, in particular reaction time and corresponding interactions, the present invention is particularly advantageous for controlling at least two components, in particular drying cylinders, of the drying section.

[0022] In one embodiment, the first component is a component of the press section, and the second component(s) or at least one of them is a component of the drying section (the press and / or drying section). The present invention can be particularly advantageous for joint control of components of the press section and the drying section, particularly due to the process dynamics, especially reaction times and interactions.

[0023] In one embodiment, the first component is a component of the press and / or drying section and the or at least one of the second component(s) is a component upstream of the press section or downstream of the drying section, in a further development the or at least one of the second component(s) is / are a component of a wire section upstream of the press section; and / or the or at least one of the second component(s) is / are a component of a headbox upstream of the press section or optionally the wire section; and / or the or at least one of the second component(s) is / are a component of a so-called approach flow system upstream of the press section or optionally the wire section or optionally the headbox for providing, cleaning and / or diluting a starting material for the paper machine, preferably a fiber suspension; and / or the or at least one of the second component(s) is / are a component of a processing section or forming section downstream of the drying section, which preferably has a reel.

[0024] For the joint control of one or more components of the press and / or dryer section together with one or more components upstream of the press section and / or one or more components downstream of the dryer section, the present invention can be particularly advantageous, particularly due to the process dynamics, in particular reaction times and interactions. In a particularly advantageous embodiment, the second component(s) or at least one of them has one or more dewatering elements upstream of the press section, preferably the wire section, preferably one or more dewatering elements for dewatering or reducing the water content of a fiber material from which the fiber web is produced ("fiber material dewatering element"), preferably at least one vacuum box or the like, and can in particular consist of this or these elements.In particular due to highly complex process dynamics or interaction with other components, the present invention is also particularly advantageous for the control of at least one dewatering element.

[0025] In one embodiment, when the paper machine is approached to different operating points as a result of varying the first control variable or to determine the first direction and / or when the paper machine is approached to different operating points as a result of varying the or one of the second control variables or to determine the or one of the second directions, at least one further component of the paper machine is controlled by a separate controller, in particular separate from the shifting of the first and optionally second control variable, on the basis of a measurement signal from one or more sensors of the paper machine. In one embodiment, the controller is supplied with the measurement signal from the sensor or the measurement signals from the sensors and / or calculated values ​​based thereon. Values ​​based on measurement signals, in particular calculated values, can be processed in particular by signal processing such as filtering, averaging, extreme value determination, scaling, addition orSubtraction, multiplication or division, convolution or the like can be determined. Values ​​from a model-based observer who carries out a simulation based on measurement signals can also be fed to the controller as values ​​based on measurement signals from sensors. Thus, in a particularly advantageous embodiment, at least one, preferably most downstream, press nip can be controlled by a separate controller on the basis of a measurement signal from at least one sensor of the paper machine, preferably a measurement signal indicative of a dry content, a speed and / or a weight of the fibrous web, and one or more, preferably more upstream, press nips and / or a steam blow box of the press section can be controlled on the basis of the quality criterion or to improve the quality criterion or towards an improvement of the quality criterion.As a result, in one embodiment, the separate controller can advantageously control the other component of the paper machine quickly, robustly and / or reliably and the first and, if applicable, second component(s) can react thereto and thus, in one embodiment, control, regulate or manage the paper machine or the process particularly sensitively and / or robustly.

[0026] The quality criterion can be one-dimensional or multi-dimensional. In one embodiment, the quality criterion J is a mixed quality criterion that includes or simultaneously considers several partial quality criteria J i , in a further development in the form of a weighted sum, Pareto optimality or the like, for example in the form J = Σw i ·J i or the like. In one embodiment, the value of the quality criterion based on a measurement signal from a sensor or the measurement signals from multiple sensors of the paper machine; and / or based on one or more parameters of a fibrous web produced in the paper machine; and / or based on a parameter indicative of energy consumption and / or wear of the first component, particularly preferably based on a drive load, preferably a hydraulic pressure, of at least one press nip; and / or a steam quantity and / or temperature, in particular steam temperature, and / or a steam pressure of a steam blow box; and / or a suction (negative) pressure of the felt conditioning device; and / or a heating and / or temperature, in particular a steam quantity and / or temperature / or a steam pressure, of at least one drying cylinder; of the first component;and / or based on a parameter indicative of energy consumption and / or wear of the or at least one of the second components, particularly preferably based on a drive load, preferably a hydraulic pressure, of at least one press nip; and / or a steam quantity and / or temperature, in particular steam temperature, and / or a steam pressure of a steam blow box; and / or a suction (negative) pressure of the felt conditioning device or the vacuum box or another dewatering element; and / or a heating and / or temperature, in particular a steam quantity and / or temperature / or a steam pressure, of at least one drying cylinder; of this second component;and / or based on a parameter indicative of energy consumption and / or wear of the or at least one of the further components controlled by the or one of the separate controllers, particularly preferably based on a drive load, preferably a hydraulic pressure, of at least one press nip; and / or a steam quantity and / or temperature, in particular steam temperature, and / or steam pressure of a steam blow box; and / or a suction (negative) pressure of the felt conditioning device; and / or a heating and / or temperature, in particular a steam quantity and / or temperature / or steam pressure, of at least one drying cylinder; of this further component; and / or based on at least one parameter indicative of energy consumption and / or wear of another component, particularly preferably based on a drive load, preferably a hydraulic pressure, of at least one press nip;and / or a steam quantity and / or temperature, in particular steam temperature, and / or steam pressure of a steam blower box; and / or a suction (negative) pressure of the felt conditioning device; and / or a heating and / or temperature, in particular a steam quantity and / or temperature / or steam pressure, of at least one drying cylinder; of this other component; and / or on the basis of the first and / or second control variable; and / or on the basis of a determined drive or roller pressure, preferably a line load, of one or more press nips; and / or on the basis of at least one speed, in particular a speed of at least one roller of a press nip and / or of a felt and / or a speed of the fibrous web produced in the paper machine;and / or determined on the basis of at least one determined temperature, in particular at least one temperature of the fibrous web produced in the paper machine, and / or a temperature of at least one press nip and / or felt of the press and / or dryer section and / or a temperature of at least one drying cylinder. ;

[0027] By implementing such a quality criterion, in particular two or more of the aforementioned partial quality criteria, the service life of paper machine components, in particular felts in the press section, can be improved and / or the quality of the produced fibrous web can be improved and / or energy can be saved. (Partial) quality criteria can also have several of the aforementioned properties.

[0028] In one embodiment, the first control variable and, in a further development, also the or one or more of the second control variables (each) are shifted taking into account a predetermined safety limit, which is parameterized in a further development, in particular by corresponding user inputs or the like. This can preferably be achieved by taking into account corresponding penalty functions in the quality criterion, which worsen it when approaching the respective safety limit, by corresponding boundary conditions and / or search region(s) and / or a corresponding limitation or restriction of the control variable(s) used or implemented for control, without the invention being restricted thereto. In this way, in one embodiment, optimal control within the framework of the safety limit(s) can be realized.

[0029] According to one embodiment of the present invention, according to or during a method for operating the paper machine having the press and / or dryer section, a fibrous web is produced in the paper machine and the first component of the press or dryer section and optionally also the second component(s) and / or optionally also the further component of the paper machine are controlled according to a method described here.

[0030] According to one embodiment of the present invention, a control system and / or paper machine is configured, in particular in terms of hardware and / or software, in particular programming, to carry out a method described here.

[0031] According to one embodiment of the present invention, a control and / or paper machine comprises: Means for varying a first control variable of a first component of the press and / or dryer section to approach different operating points of the paper machine; means for determining values ​​of a quality criterion for the operating points approached in the process; means for determining a first direction of a shift of the first control variable, in which the quality criterion is expected to improve, based on these determined values ​​of the quality criterion; and means for shifting the first control variable in the first direction.

[0032] In one embodiment, the control or paper machine or its means comprises: Means for varying a second control variable of at least one second component of the paper machine, in particular the press and / or dryer section, to approach different operating points of the paper machine; means for determining values ​​of the quality criterion for operating points approached in the process; means for determining a second direction of a shift of this second control variable, in which the quality criterion is expected to improve, based on these determined values ​​of the quality criterion; and means for shifting this second control variable in this second direction.

[0033] In a further development, the control or paper machine or its means has at least one separate controller for controlling a further component of the paper machine, in particular the press and / or dryer section, on the basis of a measurement signal from at least one sensor of the paper machine.

[0034] In a further development, the control system or paper machine or its means has: Means for determining the quality criterion based on a measurement signal from at least one sensor of the paper machine; and / or at least one parameter of a fibrous web produced in the paper machine; and / or a parameter indicative of energy consumption and / or wear of the first component; and / or a parameter indicative of energy consumption and / or wear of the second component; and / or a parameter indicative of energy consumption and / or wear of the further component; and / or at least one parameter indicative of energy consumption and / or wear of another component of the paper machine; and / or the first and / or second control variable; and / or a determined drive or roller pressure of at least one press nip of the press section; and / or at least one speed; and / or at least one determined temperature;and / or means for shifting the first control variable taking into account a predetermined safety limit.;

[0035] A means within the meaning of the present invention can be designed in hardware and / or software, in particular at least one, in particular digital, processing unit, in particular a microprocessor unit (CPU), graphics card (GPU) or the like, preferably connected to a memory and / or bus system for data or signals, and / or one or more programs or program modules. The processing unit can be designed to execute instructions implemented as a program stored in a memory system, to detect input signals from a data bus, and / or to output output signals to a data bus. A memory system can have one or more, in particular different, storage media, in particular optical, magnetic, solid-state, and / or other non-volatile media. The program can be designed in such a way that it embodies the methods described here oris capable of carrying out, so that the processing unit can carry out the steps of such methods and thus in particular can control or operate the paper machine or component(s). In one embodiment, a computer program product can have, in particular be, a storage medium, in particular a computer-readable and / or non-volatile one, for storing a program or instructions or with a program or instructions stored thereon. In one embodiment, execution of this program or these instructions by a system or a controller, in particular a computer or an arrangement of several computers, causes the system or the controller, in particular the computer(s), to carry out a method described here or one or more of its steps, or the program or the instructions are configured to do so.

[0036] In one embodiment, one or more, in particular all, steps of the method are fully or partially computer-implemented or one or more, in particular all, steps of the method are fully or partially automated, in particular by the control or paper machine or its means.

[0037] Further advantages and features emerge from the subclaims and the exemplary embodiments. The following shows, partly schematically: Fig. 1A : a paper machine with a control for controlling at least one component of a press and / or dryer section of the paper machine according to an embodiment of the present invention; Fig. 1B : a paper machine with a control system for controlling at least one component of a press and / or dryer section of the paper machine according to a further embodiment of the present invention; Fig. 2 : a method for controlling at least one component of a press or dryer section of the paper machine of the Fig. 1A oder 1B ; Fig. 3 : a block diagram of part of the control system; Fig. 4A, 4B : a quality criterion depending on a first control variable; and Fig. 5 : a quality criterion depending on a first and second control variable.

[0038] Fig. 1A shows a paper machine with a press section 10, a dryer section 20 and a control system 30.

[0039] The press section 10 has a plurality of press nips, of which two press nips 11, 12 are indicated by way of example, a felt conditioning device 13 for conditioning a felt (not shown), and a steam blow box 14. The dryer section 20 has a plurality of drying cylinders that can be heated or are heated by steam D supplied via a steam control device 2, of which two drying cylinders 21, 22 are indicated by way of example.

[0040] The paper machine has one or more sensors 41 for detecting a dry content xp , a speed v and / or a dry weight w of a fibrous web 5 produced in the paper machine between the press section and the dryer section, one or more sensors 42 for detecting a dry content x' p , a speed v' and / or a dry weight w' of the fibrous web after the dryer section and one or more sensors 43 for detecting a steam pressure for heating the drying cylinders.

[0041] The controller receives sensor signals from these sensors. One or more of the sensors can be omitted and / or one or more other sensors can be provided or used.

[0042] In one embodiment, the control system comprises a separate controller 31 which controls a pressure of the press nip 12, in one embodiment a line load P 12 , on the basis of the dry content xp between the press section and the dryer section or the corresponding measurement signal, and a further separate controller 32 which controls steam for heating the drying cylinders 21, 22 on the basis of the dry content x' p after the dryer section or the corresponding measurement signal.

[0043] In addition, the controller 30 or a means 33 of the controller 30 set up for this purpose, for example a program (module) or an extreme value controller preferably implemented thereby, determines a quality criterion J in the form of a, optionally weighted, sum of a function f 1 of the line load P 12 and the speed v (f 1 = f 1 (P 11 , v)), and a function f 2 of a corresponding line load P 11 of the press nip 11 and the speed v (f 2 = f 2 (P 12 , v); J = f 1 + f 2 ). The functions f 1 , f 2 can, for example, each be the product of the corresponding line load and speed or the like and thus reflect a load on the fibrous web. Likewise, for example, the speed can also be omitted (in each case).

[0044] As in Fig. 3 As indicated, the control or means 33 continuously varies a first control variable in the form of the line load P 11 of the press nip 11 ( Fig. 2 : step S10) and thereby an operating point of the paper machine, in one embodiment periodically over time t by adding a sine function b·sin(ωt).

[0045] As a result, the value of the quality criterion J, which is determined in step S20, also varies accordingly. The controller or means 33 demodulates these values ​​by high-pass filtering 110 and subsequent multiplication of the result by a sine function a sin(ωt) of the same periodicity. The result of the demodulation is then low-pass filtered by a low-pass filter 120, multiplied by a gain factor k, and integrated by an integrator 130 to obtain the new value of the first control variable. The press nip 11 is then controlled using this updated control variable value, with the variation being superimposed by the sine function b sin(ωt) (cf. Fig. 3 ).

[0046] How Fig. 4A, 4B illustrate, a first direction of a shift of the first control variable P 11 , in which the quality criterion J is expected to improve, is continuously determined ( Fig. 2 : step S30), wherein in step S10 the first control variable is shifted in the first direction while superimposing the above-explained sinusoidal variation in order to improve the quality criterion: if an increase in the line load P 11 results in an improvement in the quality criterion J and a reduction in the line load P 11 results in a deterioration in the quality criterion J, the line load P 11 is increased due to the demodulation described above ( Fig. 4A ). If, however, an increase in the line load P 11 results in a deterioration of the quality criterion J and a reduction in the line load P 11 results in an improvement of the quality criterion J, the line load P 11 is reduced ( Fig. 4B ). Thus, Fig.3 The modulation or addition of the sine function b sin(ωt) represents a variation of the first control variable, and the demodulation with subsequent updating by amplification and integration represents a determination of the first direction and a shift of the first control variable in the first direction. As is particularly clear from this exemplary embodiment, the variation and shift of the first or second control variable can also coincide, or a (further) variation can be superimposed on the shift. Of course, this control can also be implemented in other ways.

[0047] In a Fig. 1A To clarify the modification already shown, the control 30 or the means 33 of the control 30 determines a quality criterion J in the form of a, if necessary weighted, sum of the functions f 1 , f 2 as well as a function f 3 of a steam pressure p 14 in the steam blower box (f 3 = f 3 (p 14 )) and a function f 4 of a steam pressure p 20 for heating the drying cylinders (f 4 = f 4 (p 20 ); J = f 1 + f 2 + f 3 + f 4 ). Thus, the corresponding signal paths of the steam pressure p 14 and / or steam pressure p 20 in Fig. 1A can also be omitted and the means 33 of the control 30 can, for example, only use the line loads P 11 , P 12 as partial quality criteria (J = P 11 + P 12 ).

[0048] In a modification, the control or means 33 also continuously varies a second control variable in the form of the steam pressure p 14 in the manner described above during (normal or production) operation and also continuously shifts these control variables in the manner described above in order to improve the quality criterion.

[0049] Additionally or alternatively, in a modification, the felt conditioning device 13 can be controlled in the manner described above and / or a parameter indicative of its energy consumption can be taken into account in the quality criterion.

[0050] These variations are in Fig. 1A already indicated by corresponding bidirectional signal paths between the means 33 and the felt conditioning device 12 or the steam blow box 14. Thus, the corresponding signal paths from and / or to the felt conditioning device and / or from and / or to the steam blow box can also be omitted.

[0051] Fig. 1B shows a further embodiment of the present invention. Corresponding features are identified by identical reference numerals, so that reference is made to the preceding description and only differences are discussed below.

[0052] In the execution of the Fig. 1B the press nip 12 is controlled not by the separate controller 31 but also by the means 33 of the control system 30 on the basis of the quality criterion J, which may contain, for example, the dry content of the fibrous web 5 between the press section and the dryer section and / or after the dryer section as a partial quality criterion, so that an optimum of dry content, energy consumption (which is largely determined by the line loads and steam pressures), and mechanical load (which is largely determined by the line loads and speeds) is reached - determined by the weighting of the partial quality criteria, whereby by continuously varying the control variables, even after reaching a temporary optimum, the control system reacts to a change in conditions and adjusts the operating point of the paper machine accordingly. As described above with reference to Fig. 1A As explained, the control of the felt conditioning device and / or the steam blow box and / or the consideration of the steam pressure p 14 and / or the steam pressure p 20 and / or the energy consumption of the felt conditioning device in the quality criterion can also be omitted here.

[0053] Fig. 5 illustrates a corresponding gradient search for the quality criterion J (which is Fig. 5 by several concentric curves of constant values ​​for J) depending on two control variables in the form of the two line loads P 11 , P 12 . By varying the control variables, a (in Fig. 5 The gradient of the quality criterion (characteristic field) is determined or estimated (indicated by dashed lines) and the control variables are shifted in the direction of this gradient (cf. Fig. 5 the sequence of operating points "A" -> "B" -> "C"). "R" also indicates a search region within which this gradient search ("gradient descent line search") takes place.

[0054] In the present disclosure, "has an X" generally does not imply an exhaustive list, but is a shortened form of "has at least one X" and also includes "has two or more Xs" and "has Y in addition to X".

[0055] Although exemplary embodiments have been explained in the preceding description, it should be noted that a large number of modifications are possible.

[0056] In particular, a vacuum box or another dewatering element of a wire section (not shown) can additionally or alternatively be (co-)controlled in the manner described above.

[0057] Furthermore, it should be noted that the exemplary embodiments are merely examples and are not intended to limit the scope of protection, applications, or structure in any way. Rather, the preceding description provides the skilled person with a guide for implementing at least one exemplary embodiment. Various modifications, particularly with regard to the function and arrangement of the described components, may be made without departing from the scope of protection as defined by the claims and equivalent combinations of features. Bezugszeichenliste

[0058] 2Steam control device 5Fibrous web 10Press section 11, 12Press nip 13Felt conditioning device 14Steam blow box 20Dryer section 21, 22Drying cylinder 30Control system 31, 32Separate controller 33Program (module) / Extreme value controller (control means) 41, 42, 43Sensors 110High-pass filtering 120Low-pass filtering 130Integrator A, B, COperating point Dsteam kAmplification factor P 11 , P 12 Line load RSearch region p 14 Steam box pressure p 20 Drying cylinder / section steam pressure v; v'Speed ​​w; w'Dry weight xp ; x' p Dry content

Claims

1. Method for controlling at least one component of a press and / or dryer section of a paper machine, comprising the repeatedly repeated steps of: - varying (S10) a first control variable of a first component of the press and / or dryer section to approach different operating points of the paper machine; - determining (S20) values of a quality criterion for operating points approached in the process; - determining (S30) a first direction of a shift of the first control variable, in which the quality criterion is expected to improve, on the basis of these determined values of the quality criterion; and - shifting (S10) the first control variable in the first direction.

2. Method according to claim 1, characterized in that the first component comprises - at least one press nip; and / or - a felt conditioning device; and / or - at least one steam blow box; and / or - at least one drying cylinder; and / or - at least one dewatering element.

3. Method according to one of the preceding claims, characterized by the steps: - varying a second control variable of at least one second component of the paper machine, in particular the press and / or dryer section, to approach different operating points of the paper machine; - determining values of the quality criterion for the operating points approached in the process; - determining a second direction of a shift of this second control variable, in which the quality criterion is expected to improve, on the basis of these determined values of the quality criterion; and - shifting this second control variable in this second direction.

4. Method according to claim 3, characterized in that the second component comprises - at least one press nip; and / or - a felt conditioning device; and / or - at least one steam blow box; and / or - at least one drying cylinder; and / or - at least one dewatering element.

5. Method according to one of the preceding claims, characterized in that When starting up different operating points of the paper machine, at least one further component of the press and / or dryer section is controlled by means of a separate controller on the basis of a measuring signal from at least one sensor of the paper machine.

6. Method according to one of the preceding claims, characterized in thatthe value of the quality criterion is determined on the basis of - a measurement signal from at least one sensor of the paper machine; and / or - at least one parameter of a fibrous web produced in the paper machine; and / or - a parameter indicative of energy consumption and / or wear of the first component; and / or - a parameter indicative of energy consumption and / or wear of the second component; and / or - a parameter indicative of energy consumption and / or wear of the further component; and / or - at least one parameter indicative of energy consumption and / or wear of another component of the paper machine; and / or - the first and / or second control variable; and / or - a determined drive or roller pressure of at least one press nip of the press section; and / or - at least one speed; and / or - at least one determined temperature.

7. Method according to one of the preceding claims, characterized in that the first control variable is shifted taking into account a given safety limit.

8. A method for operating a paper machine having a press and / or dryer section, wherein a fibrous web is produced in the paper machine and at least one component of the press and / or dryer section is controlled according to a method according to one of the preceding claims.

9. A controller for controlling at least one component of a press and / or dryer section of a paper machine, the controller being configured to carry out a method according to one of the preceding claims and / or comprising: - means for varying a first control variable of a first component of the press and / or dryer section to approach different operating points of the paper machine; - means for determining values of a quality criterion for operating points approached in the process; - means for determining a first direction of a shift in the first control variable, in which the quality criterion is likely to improve, on the basis of these determined values of the quality criterion; and - means for shifting the first control variable in the first direction.

10. A paper machine comprising a press and / or dryer section and a control system for controlling at least one component of the press and / or dryer section according to one of the preceding claims.

11. Computer program or computer program product, wherein the computer program or computer program product contains instructions, in particular stored on a computer-readable and / or non-volatile storage medium, which, when executed by one or more computers or a controller or paper machine according to one of the preceding claims, cause the computer(s) or the controller or paper machine to carry out a method according to one of the preceding claims.

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