EP2371748A2 - Method for determining at least one regulating parameter of a dancer controlling element - Google Patents

Abstract

The method involves detecting a stepper position (Xist) of a stepper, and specifying speed (nv) of a winding device based on the detected stepper position. Control parameters (KP, TN) are automatically determined in dependence of a diameter of the winding device during operation of a processing machine. Speed of the winding device is specified for winding or unwinding a material web e.g. paper or card board. Speed of an impact tool i.e. transport roller, is specified for transporting a material web. An independent claim is also included for a control unit for automatically determining a control parameter of a stepper position-control element in a processing machine.

Description

The present invention relates to a method for determining at least one controller parameter of a dancer position control element and to a computing unit configured for carrying out the method.

Although the invention is described below essentially with reference to printing presses, it is not limited to such an application, but rather usable in all types of machine tools in which the web or material web passes through a so-called dancer, whose position is controlled. The web can be made of paper, cloth, cardboard, plastic, metal, rubber, in foil form, etc.

State of the art

The present invention relates to the field of web tension control in processing machines. In processing machines, in particular printing machines, a web is moved along driven axes (web transport axes), such as draw rolls or feed rolls, and non-driven axes, such as deflection, guide, drying or cooling rolls. The web will be at the same time processed by means of mostly likewise driven processing axes, for example printed, punched, cut, folded, etc.

In processing machines, such as printing machines, in addition to, for example, a longitudinal and / or page register often the web tension is regulated or adjusted in order to achieve an optimal processing result. A known possibility for web tension adjustment, in particular for a winder (winding or unwinding device), uses a dancer, in which a movable dancer roll impresses the web tension. The position of the dancer roll, the so-called dancer position, is kept at a setpoint value by the dancer position control. As long as the dancer is within its mobile mechanical limits, the web tension is essentially maintained by the impression of force, for example, a pneumatic. Dynamic processes will not be explained further here. The dancer has the advantageous property of being able to absorb irregularities in the web run within relatively large limits, without there being any significant change in the web tension.

Known regulators, such as P controllers, D controllers, I controllers, etc., and any combinations thereof, include controller parameters that must be set. Typical control parameters are the proportional gain K _P, the integral gain K _I, the differential gain K _D, the reset time T _N, the derivative-action time T _V, T delays etc.

• Bspw. ist in der EP 1 790 601 A2 dargestellt, dass Reglerparameter in Abhängigkeit von Warenbahnparametern (z.B. E-Modul), Maschinenparametern (z.B. Warenbahnlänge, Warenbahngeschwindigkeit oder Trägheitsmoment) und Betriebsparametern (z.B. Regelabweichung) bestimmt werden können.

In the prior art, no methods are known to simplify the parameterization of the dancer position control or even to automate. Although a number of methods have been developed by the Applicant to simplify the parameterization of web tension controllers:

• For example. is in the EP 1 790 601 A2 shown that controller parameters depending on web parameters (eg E-module), machine parameters (eg web length, web speed or moment of inertia) and operating parameters (eg control deviation) can be determined.

In the DE 10 2008 035 639 is shown that in addition to these variables and dead times in the controlled system are available and can be used to determine the controller parameters.

In the not pre-published DE 10 2009 019 624 is a controller parameter, depending on at least one parameter characterizing the web, such as the modulus of elasticity and / or cross-section, at least one parameter characterizing the machine, such as the web speed and / or the section length, and at least one, in particular constant (ie not web speed-dependent) and / or speed-dependent, dead time, such as a transmission time and / or a measurement time described.

However, the methods described in the cited documents are not transferable to a dancer position control, since in the dancer position control also changes the length of the web and thus a completely different behavior of the controlled system - namely an integral behavior - is present. The parameterization of a dancer position control therefore essentially takes place by hand. In this case, a step response of the controlled system is usually evaluated for determining the route parameters. The control parameters can then be determined by the operator by means of control-technical knowledge by the operator.

It is therefore desirable to specify a simplified and preferably automatable method for the parameterization of a dancer position control.

Disclosure of the invention

According to the invention, a method for determining at least one controller parameter of a dancer position control element for a processing machine as well as a computing unit for carrying out the method with the features of the independent patent claims is proposed. Advantageous developments are the subject of the dependent claims and the following description.

Advantages of the invention

The invention is essentially based on the recognition that a dancer position control element can be parameterized automatically if the diameter of the axis or roller controlled by the dancer position controller is taken into account for determining at least one controller parameter. On the one hand, in the case of a winder with dancer position control, this can be achieved by changing the diameter of the winding device during the winding process, i. Up or unwinding device, or on the other hand, in a web tension control with dancer position control the constant diameter of a web transport roller. The latter case can be found, for example, in the regulation of a collection or withdrawal plant. As a result, the parameterization can be automated, so that the operator of the machine no longer has to have control technical expertise. Setup trips that were previously necessary to determine the route parameters (for example via a step response) can be omitted. Although the discussion of diameter is essentially made, it should be understood that this also includes the consideration of equivalent or derivable quantities, e.g. Radius or circumference is included.

In known web tension controls with direct web tension measurement, eg. Via load cells, ie web tension controller without dancer, which on the speed of a limiting nip as a control signal, the controlled variable (web tension) directly For the controlled system, a PT1 element with dead time or a PT2 element can be used to a good approximation. If, on the other hand, a dancer position control is considered, the behavior of the controlled system is basically different, since here an integrating controlled system is present and the position of a dancer roller instead of the web tension is regulated.

The dancer position control element expediently comprises a proportional component and preferably also an integral and / or differential component. In particular, it therefore comprises a P, PI, PD or PID element. As control parameters a proportional gain K _P, and optionally a reset time T _N and / or a derivative-action time T _V are automatically determined.

In an embodiment, the at least one controller parameter is determined regularly or triggered during operation. The frequency of the determination process can thus be balanced out between optimal control with frequent parameterization on the one hand and low computational effort with less frequent parameterization on the other hand. If the speed of a variable diameter roller is used as the manipulated variable, a more frequent determination of the at least one controller parameter is expedient.

Expediently, when determining the at least one controller parameter, a measurement behavior of a dancer position detection device is taken into account. The dancer position detection device outputs the attitude actual value as a voltage or current value. This ratio of actual position value to measuring signal can show a linear or non-linear as well as a static or dynamic behavior. A static relationship is preferably taken into account via an input or output characteristic compensation (eg Wiener or Hammerstein model), whereas a dynamic relationship can be taken into account via a non-linear or adaptive controller.

It is advantageous that the at least one controller parameter is determined as a function of a predefinable weighting factor. Often, controller parameters calculated by a theoretical design are not optimal in practice. As reasons for this, additional, non-ascertainable delay times, nonlinearities, signal noise, incorrectly determined route parameters or the control quality or the web tension behavior in a constant run can be cited. In particular, the last point is usually disadvantageous. Although the control loop oscillates quickly, in the constant run it often results due to the discretization or quantization of the measurement results or manipulated variables a restlessness due to a relatively "strong" Proportionalanteils. Preferably, a method is proposed in which a weighting factor, for example, as a measure of a "controller sharpness" is specified as a further input variable. For example, one or all theoretically determined controller parameters can be multiplied by the weighting factor (eg between 0 and 1, but also greater than 1). With the help of this input parameter, the user can adjust the controller parameters as required. By way of example, this could be achieved in the case of a PI control element by multiplying the proportional gain and / or reset time by this percentage factor. Alternatively, in addition to the free specification of a weighting factor, a selection of predefined values may be possible (eg 20%, 40%, 50%, 60%, 70%, 80%, 85%, 90%, 95%, 100%, 105%). , ...). The user can find a suitable setting for his machine type and easily adapt it to other physical quantities. Also different types of machines can be set comparably. It results in a significant simplification for the user, since he only has to enter (known) physical variables and can cause a change in the automatically calculated controller parameters using this single factor "controller sharpness". Complex settings of the controller parameters are no longer necessary, which saves time-consuming test series and test runs.

In an embodiment, a design criterion for determining the at least one controller parameter is specified. For interpretation of controller parameters, various design criteria (e.g., symmetrical optimum, root locus design, magnitude optimum, or Ziegler-Nichols) are known in the literature. By specifying the criterion to be used, in particular in the arithmetic unit according to the invention, for determining the at least one controller parameter, the quality and speed of the determination can be influenced. These design criteria are partially interpretable also for leadership or disruptive behavior. Thus, it is possible for the user to switch between management behavior and disturbance behavior, depending on the machine requirement and machine condition (for example, set-up or production phase).

An arithmetic unit according to the invention, e.g. a control unit of a printing press, is, in particular programmatically, adapted to perform a method according to the invention.

Also, the implementation of the invention in the form of software is advantageous because this allows very low cost, especially if an executing processing unit is still used for other tasks and therefore already exists. Suitable data carriers for providing the computer program are, in particular, floppy disks, hard disks, flash memories, EEPROMs, CD-ROMs, DVDs and the like. It is also possible to download a program via computer networks (Internet, intranet, etc.).

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

It is understood that the features mentioned above and those yet to be explained not only in the combination specified, but can also be used in other combinations or in isolation, without departing from the scope of the present invention.

The invention is illustrated schematically by means of exemplary embodiments in the drawing and will be described in detail below with reference to the drawing.

figure description

FIG. 1

shows a section of a processing machine with an unwinding device, a dancer and an infeed mechanism, which may underlie the invention,

FIG. 2

shows a schematic representation of a control loop for the processing machine according to FIG. 1 .

FIGS. 3 to 6

show embodiments of functional modules for the determination of controller parameters according to different preferred embodiments of the invention.

Without limitation, a dancer position control for an unwinding process will be described below. It is understood, however, that the invention can also be used for the dancer position control for a winding operation or for the dancer position control of a feed or pull-out unit. The illustration is chosen so that both mechanisms, ie the control of a winding device with a changing diameter on the one hand and a tension roller with a constant diameter on the other hand can be explained on the basis of the example of a developer with dancer in combination with a subsequent driven roller.

In FIG. 1 a section of a web-processing machine 100 is shown schematically, wherein a web 101 is unwound from an unwinding device 102 as an upstream nip and via a dancer 110 a downstream nip, here an infeed 103, is supplied. The dancer 110 comprises two stationary deflection rollers 111 and a movable dancer roller 112, which imprints a force F ₀₁ and thus a web tension in the web. The distance between the clamping points is designated L ₀₁ . The dancer position actual value x _is detected by a dancer position detection device 140 shown schematically and transmitted to a computing unit 150, which is set up in particular for controlling the dancer position. The task of the dancer position control is to keep the position of the dancer roller 112 at a desired position x _nominal . The arithmetic unit 150 also determines according to an embodiment of the invention automatically the necessary controller parameters.

The speeds of the unwinding device 102 and of the intake system 103 can be controlled by the arithmetic unit 150, resulting in the peripheral speeds (web speeds, conveying speeds) v ₁ and v ₂ , respectively, depending on the respective diameter. In the present example v _{1 is used} for the dancer position control. During the unwinding process, ie, the diameter D of the unwinding device 102 or of the web of web winding located on the unwinding device is reduced.

The distance of the deflection rollers 111 of the dancer 110 is designated by L _Hypo and defines together with the actual dancer position value x _is a wrap angle β of the web 101 to the dancer roll 112. Frequently, the distance of the stationary deflection rollers is selected so that the wrap is 180 ° , However, a preferred embodiment of the invention is designed so that the controller parameterization also cope with arbitrary wrap angles β or any deflection roller distances L _Hypo . The length of the web from Vertex of the deflection roller 111 to the apex of the dancer roll 112 is denoted with l _web.

In FIG. 2 the dancer position control on which the invention is based is schematically illustrated by means of a control loop 200. The reference variable, x _set, is supplied to a comparator or subtracter, which also includes the control variable, ie the dancer position _is x, via links 205 and 204 will be discussed in more detail below on, is supplied. The resulting control deviation e is fed to a dancer position control element 201, which in the present case is designed as a PI element with a proportional gain K _P and a readjustment time T _N. Without limitation, the dancer position controller 201 may also be implemented as a P, PD, or PID member, or as another controller, such as a state controller. For the following description, however, a PI controller with the following transfer function is assumed: $${\mathrm{F}}_{\mathrm{R}}\left(\mathrm{s}\right)\mathrm{=}{\mathrm{K}}_{\mathrm{P}}\mathrm{\cdot }\left(\mathrm{1}\mathrm{+}\frac{\mathrm{1}}{{\mathrm{T}}_{\mathrm{N}}\mathrm{\cdot }\mathrm{s}}\right)\mathrm{,}$$

The control element generates in the present case as a control signal nv an additive speed setpoint, which is guided to a controlled system 202, which is designed here as an I-section. This control signal causes a speed adjustment - depending on the control sense - the unwinding device 102 or the infeed 103. In the illustrated I-section 202, a change in speed affects as a linear increase or decrease in the total length of the web 101 between unwinding 102 and retraction 103 and thus on the dancer position Actual value x _is off. The dancer position actual value x _is - as shown below - a function of the geometric variables D, L ₀₁ , L _Hypo .

The dancer position actual value x _is detected by the dancer position detection device 140, in which a certain relationship between detected actual position value and is present measured value. This ratio is represented by a linear or non-linear characteristic (eg static characteristic of a Hammerstein model) 205 in the return branch. Since the measuring signal is always subject to a transmission dead time and usually an additional signal filter, a PT1 element 204 is also present in the return branch.

The total length l _tot results from FIG. 1 based on the following consideration: $$l_{\mathit{train}}=\frac{L_{\mathit{Hypo}}}{2\cdot \cos \left(\alpha \right)}=\frac{L_{\mathit{Hypo}}}{2\cdot \cos \left(90\mathit{°}-\frac{\beta }{2}\right)}$$

The angle a can _is x over the dancer position actual value and to determine the distance of the deflection rolls L _Hypo to: $$\alpha =\arctan \left(\frac{2\cdot x_{\mathit{is}}}{L_{\mathit{Hypo}}}\right)$$

The total length of the _web results in l _ges = L ₀₁ - L _Hypo + 2 · l _lane .

By reshaping the dancer position actual value is obtained: x _ist = f ( l _ges , L ₀₁ , L _Hypo ).

wobei L_Umfang den Umfang der Tänzerrolle 112 und D_Tänze den Durchmesser der Tänzerrolle bezeichnen.In the widespread embodiment with a looping of the material web of β = 180 °, the total length of the material web results in: $$l_{\mathit{ges}}=L_{01}+2\cdot x_{\mathit{is}}+0.5\cdot L_{\mathit{scope}}-D_{T\ddot{a}\mathit{nzer}}$$

wherein L _periphery 112 and _dances D designate the diameter of the dancer roll the scope of the dancer roll.

Switching results in the actual position of the dancer position as a function of the geometry and the current total length. The impressed into the web force corresponds to half of the applied force F ₀₁ .

• wobei v ₁ die Umfangsgeschwindigkeit der stromaufwärtigen Klemmstelle 102,
• v ₂ die Umfangsgeschwindigkeit der stromabwärtigen Klemmstelle 103,
• ε₀₁ die Dehnung der Warenbahn 101 zwischen stromaufwärtiger Klemmstelle 102 und Tänzer 110 und
• ε₁₂ die Dehnung der Warenbahn 101 zwischen Tänzer 110 und stromabwärtiger Klemmstelle 103 ist.

The integrating controlled system 202 can be described by the following equation with a typical usual winding of 180 °. $$l_{\mathit{ges}}\left(s\right)=\frac{1}{2\cdot s}\cdot \left(v_1\left(s\right)\cdot \frac{1+{\epsilon }_{12}\left(s\right)}{1+{\epsilon }_{01}\left(s\right)}-v_2\left(s\right)\right)$$

• where v _{1 is} the peripheral speed of the upstream nip 102,
• v _{2 is} the peripheral speed of the downstream nip 103,
• ε ₀₁ the elongation of the web 101 between upstream nip 102 and dancer 110 and
• ε _{12 is} the elongation of the web 101 between the dancer 110 and the downstream nip 103.

It can be seen that an increase in the speed v ₁ (s) of the unwinder 102 causes an increase in the total _{web length} l _ges and opposite an increase in the speed v ₂ (s) of the infeed 103 causes a reduction in the total length of the web. As a result, a positive and negative control sense, as known in the art in a web tension control described. The positive control sense thus corresponds to the control by means of the unwinder as a control signal, since in this case causes an increase of the control signal at the same time an increase of the output signal. Conversely, an increase in the speed of the feeder causes a reduction of the output signal, which corresponds to a negative control sense.

In particular, it becomes clear that both circumferential speeds v ₁ (s) and v ₂ (s) enter into the controlled system. In real controls, however, it is not the peripheral velocity v ( s ) that is known, but the angular velocity u ( s ) from which the peripheral velocity v ( s ) results in a known manner: $$v\left(s\right)=2\cdot \pi \cdot r\left(s\right)\cdot u\left(s\right)$$

Thus, the track behavior depends on the radius r (s) of the limiting terminal points. Since the feed train 103 can be assumed to have a constant radius of the rollers, only the radius (or diameter D) of the unwinding device 102 is to be taken into account here and is taken into account in the automatic determination of both controller parameters K _P and T _N according to the preferred embodiment explained here , From the track behavior described above, the controller parameters K _P and T _N can be determined automatically and computer-implemented by means of conventional methods, such as symmetrical optimum, root locus interpretation, Chien-Rhones-Reswick (CHR), etc.

For arbitrary wrap angles β (and thus any a), the transfer function of the controlled system (without sensor, signal filtering and transmission dead times) results in: $$l_{\mathit{ges}}\left(s\right)=\frac{1}{f\left(\alpha \right)\cdot s}\cdot \left(2\cdot \pi \cdot r_1\left(s\right)\cdot u_1\left(s\right)\cdot \frac{1+{\epsilon }_{12}\left(s\right)}{1+{\epsilon }_{01}\left(s\right)}-2\cdot \pi \cdot r_2\left(s\right)\cdot u_2\left(s\right)\right)$$

In this case, the function f (α) may have a linear or nonlinear behavior as a function of the geometric conditions. Since this function represents only a static nonlinearity due to the trigonometric functions, this can be taken into account by an input or output characteristic compensation (eg Wiener or Hammerstein model).

The same applies to the sensor, which reproduces the actual position via a voltage or current value. The ratio of actual position value to measuring signal can in turn show a linear or non-linear as well as a static or dynamic behavior. A static relationship can, for example, be taken into account again via an input or output characteristic compensation (Wienerstein or Hammerstein model) become. A dynamic relationship can be taken into account, for example, via a nonlinear or adaptive controller.

When determining the controller parameters, the length L ₀₁ between unwinding device 102 and intake system 103 can be neglected in a first approximation if the controller is linearized at the operating point. Further simplification can be achieved by neglecting elements 204 and 205 in the return branch. As a result, according to a preferred embodiment, a determination of the controller parameters only takes into account the winding diameter D and control sense, optionally additionally taking into account delay times and optionally additionally taking into account the characteristic curve of the dancer bearing detection device

In the FIGS. 3 to 6 Function blocks 300, 400, 500 and 600 for determining the controller parameters K _P and T _N are shown. There are different input variables on the left side, which - optionally also optionally - are included in the determination of the controller parameters.

Preferably, it is provided to supply the control sense to the function block. The sense of control is denoted by +/- in the figures. The sense of control essentially influences the sign of the controller output variable and can therefore also be supplied to another location within the control loop. Furthermore, it is provided that the current diameter D of the winding device (or the constant diameter D of a tension roller) fed to each of the illustrated functional components.

Optionally, it is provided to supply the function blocks with the characteristic curve KL of the dancer position detection device and / or delay times T, the consideration of which - as described above - improves the determination of the controller parameters.

The function module 400 is provided for the determination of the controller parameters in cases in which the wrap angle β is not 180 °. To determine the controller parameters, the distance L _{Hypo of} the deflection rollers 111 of the dancer 110 and the length L ₀₁ are preferably also taken into account here. As an alternative to taking into account the variables L _Hypo and L ₀₁ , the angles a and β can also be taken into account.

According to another preferred embodiment, which is represented by the function module 500, a weighting factor w is used to determine the controller parameters, which is e.g. between 0 and 100% can be (also possible values greater than 100%). As explained above, the weighting factor w influences the so-called controller sharpness.

The function module 600 differs from the functional module 500 by the additional possibility of specifying the design criterion K, e.g. CHR, etc. (see above).

As explained, the controller parameters can be calculated automatically depending on physical quantities. Some of these sizes, in particular the diameter of the winding device, change during the machining process. In addition to the measurement of these quantities, a determination by means of control-technical observers and / or a parameter estimation method is also proposed.

Claims (13)

Method for the automatic determination of at least one controller parameter ( K _P , T _N ) of a dancer position control element (201) in a processing machine (100) comprising a dancer (110) whose dancer position ( x _is ) is detected, based on the detected dancer position ( x _is ) a speed (nv) of a roller (102, 103) is predetermined, wherein the at least one controller parameter ( K _P , T _N ) depending on a diameter (D) of the roller (102, 103) is determined automatically. The method of claim 1, wherein the rotational speed of a winding device (102) for winding or unwinding of the web (101) is specified and the at least one controller parameters ( K _P , T _N ) depending on the changing during the winding process diameter (D). the winding device (102) is determined automatically. The method of claim 1 or 2, wherein the rotational speed of a transport roller (103) for transporting the web (101) is specified and the at least one controller parameters ( K _P , T _N ) in response to the substantially constant diameter of the transport roller (103) automatically is determined. Method according to one of the preceding claims, wherein the dancer position control element (201) comprises a proportional component and the at least one controller parameter comprises a proportional gain ( K _P ). Method according to claim 4, wherein the dancer position control element (201) additionally comprises an integral component and / or a differential component and the at least one controller parameter additionally comprises an adjustment time ( T _N ) or a derivative time Method according to one of the preceding claims, wherein the determination of the at least one controller parameter ( K _P , T _N ) during the operation of the processing machine (100) is carried out regularly or triggered. Method according to one of the preceding claims, wherein in the determination of the at least one controller parameter ( K _P , T _N ) at least one delay time, dead time and / or signal smoothing time (T) is taken into account. Method according to one of the preceding claims, wherein in the determination of the at least one controller parameter ( K _P , T _N ) a measurement behavior (KL) of a dancer position detection device (140) is taken into account. Method according to one of the preceding claims, wherein the dancer (110) comprises two stationary deflection rollers (111) and a movable dancer roller (112) and in determining the at least one controller parameter ( K _P , T _N ) a distance ( L _Hypo ) of the two stationary deflection rollers (111) and / or a wrap angle (a, β) of the deflection rollers (111) and / or the dancer roller (112) by the web (101) is taken into account. Method according to one of the preceding claims, wherein a predeterminable weighting factor (w) is included in the calculation of the at least one controller parameter ( K _P , T _N ). Method according to one of the preceding claims, wherein in the calculation of the at least one controller parameter ( K _P , T _N ) enters a specifiable design criterion (K). The method of any one of the preceding claims, wherein the dancer (110) is between an upstream nip (102) and a downstream nip Clamping point (103) is arranged and the at least one controller parameter ( K _P , T _N ) is calculated on the basis of the track behavior $l_{\mathit{ges}}\left(s\right)=\frac{1}{2\cdot s}\cdot \left(v_1\left(s\right)\cdot \frac{1+{\epsilon }_{12}\left(s\right)}{1+{\epsilon }_{01}\left(s\right)}-v_2\left(s\right)\right).$

where v _{1 is} the peripheral speed of the upstream nip (102), v _{2 is} the peripheral speed of the downstream nip (103), ε _{01 is} the stretch of the web (101) between the upstream nip (102) and dancer (110) and ε _{12 is} the stretch of the web (101) between dancer (110) and downstream nip (103). Arithmetic unit (150) adapted to perform a method according to any one of the preceding claims.

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