EP0976674B2 - Web tension control device - Google Patents

Abstract

The rotation rate speed (revs) approaches a previously set, aimed-at or intended value. The controller is set for the intended rev. counter value (NSOLL) operated through the drive motor. The feed-path tension value is also set (FSOLL). A sensor measures the actual value of the paper tension (FIST) in the path. The tension controller is connected to this sensor and to the set intended values. The revolution speed controller is connected to the output (NSOLL) of the tension controller.

Description

The present invention relates to a web tension control device and is particularly suitable for shaftless web offset printing presses in tower construction, preferably for newspaper offset.

DE 43 44 896 C2 of the applicant discloses an embodiment of a shaftless driven web-fed rotary printing press with at least one color-transmitting cylinder pair with a blanket cylinder and a plate cylinder, which are mechanically coupled together for common drive by a first motor and a counter-pressure cylinder with the blanket cylinder a pressure nip for the web forms and is driven by a further motor, at least one ink roller assigned to the plate cylinder and at least one controller for the motors, wherein the first motor drives the blanket cylinder via a gearbox and the other motor drives the impression cylinder via another gearbox.

The precise adjustment and regulation of the web tension in web offset printing presses during the printing process is of great importance. The properly adjusted web tension is not only necessary for achieving a good print quality since e.g. Not only color and cut register are better adhered to, but also leads to an increase in print productivity, since less or no paper tears are caused. It is therefore common for the web tension to specify certain web tension profiles along the individual paper paths, i. that predetermined upper or lower limit values of the web tension should not be exceeded or fallen below.

However, the paper elastic modulus can vary greatly from paper roll to paper roll, which can lead to a sudden change in web tension. This occurs e.g. when changing the roles and has a very negative impact on the quality of the printed product. Furthermore, the modulus of elasticity of the paper may also change within the same roll of paper, because, for example, due to the storage, the outer and inner layers of the paper roll are differently moist. These changes in the modulus of elasticity of the paper, due to the resulting web tension variations and paper stretch, result in changes in the color and cut register during roll handling and thus in quality degradation. Also varying color and humidity assignments change the modulus of elasticity.

Another influencing factor for the paper web tension are transient processes, such. B. ramped speed changes of the paper web, or even moving a blanket cylinder between a pressure on and a pressure-off position. These transient events occur e.g. in non-corrugated web offset printing presses with a so-called "flying" disk change functionality often, whereby without stopping the printing machines successively different production runs take place. Each time, the web tension is strongly influenced and changed.

Since these changes in the web tension lead to a deterioration of the print quality, ever better rules for compliance with a predetermined web tension profile have been developed, which are described below.

1. Simple web tension control

Fig. 4a shows a known web tension control device. In this case, a target web tension value F _{SOLL is} predetermined by a machine control and a web tension controller determines from a difference between the target web tension value F _SOLL and a web tension actual value F _IST measured by a web tension measuring sensor a lag _target value ΔN DESIR

From a arranged at the end of the printing process folder a Drehzahlleitsollwert N _{SOLL is} tapped. Since the folder but functionally already has a non-steady mode, the determined speed reference N _SOLL can not be used directly for the web tension control, but must first be low-pass filtered to suppress higher-frequency interference components of the Drehzahlleitsollwert signal N _SOLL . The low-pass filtered speed reference setpoint N _SOLL is applied with the lag value ΔN _SOLL from the web tension controller and the actual speed value N _{IST of} the roller driven by the drive motor, and the signal obtained is fed to the speed controller, which controls the drive motor.

However, the mandatory low pass filtering of the speed command setpoint N _SOLL from the folder is disadvantageous because this low pass filtering results in inertia of the overall control, and the speed command setpoint N _SOLL greatly attenuated by the tefp pass filtering affects the overall control dynamics of the web tension control because the control parameters of the web tension controller are consistent with the control parameters the downstream speed controller must be tuned.

2nd lag control

The lag control is a simple and fast speed control.

As shown in Fig. 4b, the speed controller, a value .DELTA.N is supplied, which is determined from a difference of a Drehzahlleitsollwerts N _setpoint eg a bus system and a measured actual value N _actual speed, and a lag setpoint .DELTA.N _SET . This speed controller controls the drive motor in a known manner.

However, it is necessary to adjust the Nacheilungssollwerte .DELTA.N _SOLL before operation so that a desired web tension is achieved, where: .DELTA.N _SOLL = n · N _SOLL. Where n represents the lag.

Although the lag control is structurally very easy to implement, and avoids the disadvantages of the web tension control, due to the low-pass filtering, but the lag control also has disadvantages. For example, the resulting web tension is dependent on the speed of the paper web. This means that without post-corrections of the speed _reference setpoints N _SOLL the web tension can not be kept constant, eg during a speed ramp. This leads, as mentioned above, to a deterioration in the quality of the printed products. Furthermore, a strong fluctuation of the paper web tension z. B. at a normal stop. or an emergency stop of the printing press extremely negative, since in the pure speed control, the web tension can grow extremely strong, which can easily lead to a demolition of the paper web. Furthermore, the web tension also varies greatly in a pressure on or a print-off process of all pressure points, for example, a four-high tower, which is also not desirable.

3. Lag control with droop functionality

In order to overcome the disadvantages of the two above-mentioned control devices, a lag control with a so-called droop functionality has been proposed. In this case, the speed reference setpoint N _{SOLL is} corrected for the speed controller of the retractable drive as a function of the load torque, the load torque in the steady state is proportional to the web tension.

Fig. 4c shows such lag control with droop functionality. In turn fed to a speed controller is a difference .DELTA.N which value speed is _N, and a further correction variable N _M, which is determined from a measured engine load torque, and a Nacheilungssollwert .DELTA.N _SOLL is formed by a rotational-speed N _SOLL, a.

In contrast to the pure speed control, the control with droop functionality has the advantage that disturbances caused by changes in the paper elastic modulus or by pressure on or pressure off processes cause only minor deviations of the web tension. However, disturbances due to a change in the modulus of elasticity of paper cause a permanent deviation of the web tension if the value ΔN _{SOLL is} not corrected. As a result, a desired web tension value can not be maintained after a disturbance without a corresponding adaptation of the value ΔN _SOLL , since the current elastic modulus of the paper web is generally unknown.

Fig. 5 shows a linearized diagram in which the abscissa, the rotational speed N of the intake train is plotted at a certain engine speed, wherein the paper web tension F is plotted on the ordinate. For two different elastic moduli of a paper web, the straight lines E ₁ and E ₂ are shown, wherein the modulus of elasticity of a paper web can vary between these two straight lines shown by way of example. The qualitative characteristic of the simple web tension control device is marked with 1, the characteristic of the lag control with 2 and the characteristic of the lag control with droop functionality is marked with 3.

If, for example, the modulus of elasticity of the paper web changes from E ₁ to E ₂ , a lag control (characteristic 2) results in a difference ΔF _{2 of} the web tension, which is considerably greater than the web tension difference which occurs in the case of lag control with droop functionality, such as represented by ΔF ₃ in Fig. 5. This illustrates the advantage of this scheme.

However, even such minor variation in web tension is still detrimental, e.g. in terms of the quality of the resulting printed products due to the deviation of the color and cut register

From US 3,416,058 a control circuit for a motor is known, which can be used to control the tension of a paper web between two pairs of rollers, wherein a measured web tension and a predetermined web tension are fed to a controller which outputs a signal to a speed control, which continues Speed reference signal and a feedback speed signal receives. This speed control outputs a signal to a current controller for driving a drive motor of a roller of the roller pair.

It is the object of the present invention to provide a control device for the tension of a paper web of a shaftless driven printing machine, which avoids the disadvantages of the known arrangements. In particular, a control device and a control method are proposed with which the web tension can be controlled quickly and accurately.

This object is achieved by a control device having the features of claim 1 and a control method having the features of claim 5.

Advantageous embodiments will be apparent from the dependent claims.

The advantages associated with the invention be achieved in that both derDrehzahlleitsollwert N _SOLL and the web tension set value F _SOLL for example, by a machine controller can be set arbitrary. As a result, a speed _reference setpoint N _{SOLL can be} specified in real time, which does not have to be filtered and is available in its original form as a control variable. The control device can thus adjust the paper web tension immediately after the occurrence of a disturbance variable directly and without inertia. Similarly, the web tension setpoint F _SOLL can be selected freely and thus specified in terms of optimizing the print quality, so that the two important for the control setpoint variables F _SOLL and N _{SET of} the controller can be freely specified. A web tension control circuit allows changes in printing conditions due to, for example, a change in the paper elastic modulus or a print-on / print-off operation of blanket cylinders on the paper web to be quickly taken into account in the control, at a constant speed To ensure web tension during operation, while the speed can be adjusted quickly.

The simultaneous specification of the generated web tension setpoint value F _SOLL and the generated rotational speed _target setpoint value N _{SOLL also} enables a better control of the control device, since two setpoint values for the control can be freely selected and, for example, can be quickly changed by the machine control system without causing any occurrences of the normal printing process must be considered, which always leads due to run times to a sluggishness of the whole scheme.

The speed controller of the control device according to the invention is supplied to the difference between the rotational-speed N _SOLL and the lag setpoint .DELTA.N _SOLL, which was determined by the web tension controller from the web tension set value F _SOLL and _IS the web-tension actual value F to the motor to control so that a desired, preferably constant, web tension at a given speed can be obtained.

The web tension control device according to the invention thus enables better matching between web tension control loop and speed control loop by using an undisturbed speed reference setpoint signal for the subordinate speed control loop. As a result, disturbances of the web tension, e.g. be controlled in an optimal time before the infeed plant. This leads to very good dynamic properties of the control according to the invention, which are required in the above-mentioned changes in the operating conditions to maintain a constant web tension. Likewise, with the regulation according to the invention, changes in the web tension in the printing tower itself can be limited. Namely, the orders of magnitude of these changes can be estimated to be about the same regardless of the type of paper, moisture and other disturbances. Thus, the color register and cut register can be better kept with the scheme according to the invention, since the web strains can be limited to a certain small area. The web tension control according to the invention further has the advantage that the web tension can always be kept in a suitable range for the paper used, so that paper cracks can be avoided.

It is possible, the control device according to the invention either individually z. B. to provide the intake or extracting. Furthermore, it is also possible that the control according to the invention is used both for controlling the web tension at the feed train and for controlling the extension work. Such a control of the infeed and outfeed works of the printing tower has the advantage that the web tension over the entire length of the web can be controlled by the printing tower, so that there is a particularly favorable tension, preferably a constant web tension, from the infeed on the printing tower to the extraction plant , In such an embodiment of the invention, the web tension regulators are respectively arranged at the infeed unit or the extension unit or at both, which are to be controlled. The control according to the invention can also be arranged individually or together with other control devices at other locations of the paper web, such as e.g. in the printing tower itself or the funnel inlet roller.

It is advantageous to supply the web tension setpoint F _{SOLL to} the control device via a bus system. Particularly preferably, the speed reference setpoint N _{SOLL is} transmitted via a fast bus. In particular, this is a real-time bus system, such as a SERCOS bus. This control of the control device or control devices by such a bus system greatly simplifies the control of the control system on a printing tower, since all desired values can thus be predetermined by a remote machine control of the control system. Thus, the local input of desired values can be dispensed with. Furthermore, it is possible by such a bus system that different printing towers are controlled via a single bus, which in turn can specify different, but coordinated setpoints for the respective printing towers. The individual printing towers can thus be operated individually with different web tension or with different types of web paths.

In order to obtain a desired, preferably constant, web tension over the entire course of the paper web, it is advantageous to obtain more than one web tension sensor for determining various actual values as input variables of a single control device. Thus, for example, in the case of a web tension control at the infeed as an input to the control device in addition to the web tension, for example, at the infeed itself, the web tension on the extension work and / or the web tension at the hopper inlet roller or any other suitable measuring point can be used. Of course it is also conceivable, only the web tension z. B. at the extract works or to use on the funnel inlet roller for the web tension control of the feed train, which of course also one or more additional web tension sensor signals can be used. For example, the web tension control of the infeed unit can use the web tension at the extension unit and at the hopper infeed roller as the only actual variables of the control in order to control the paper web tension.

Corresponding embodiments apply analogously to the regulation of the web tension at the extension work, which can also regulate the paper web tension as a function of the web tension actual size of a single web tension sensor, which need not necessarily be arranged on the extension work itself. Any combination of two or more web tension actual value signals of individual web tension sensors can also be used for the regulation of the web tension on the extension work in order to regulate the paper web tension.

It is advantageous if the actual web tension values recorded by the one or more web tension sensors are first fed to a transmission element or different transmission elements with a suitable transmission function before they are used as input variables of the web tension control. In this case, the individual transmission elements can be used, for example, to weight the proportions of each actual value signal for a total actual trajectory voltage. Of course, each individual measured by a web tension sensor actual signal can be supplied only to a transmission element with a suitable dynamic transfer function, such as a PT ₁ or PT ₂ member before it is the web tension control is supplied with other possibly also weighted or dynamically altered Web tension actual variables is linked. Such consideration of multiple weighted and dynamically weighted web tension variables may account for changes within the printing tower due to, for example, the moisture of the paper and changes along the usually long paper paths between, for example, the pullout and the hopper roll for the control of the total web tension. By suitable parameterization and adjustment of the individual weighting or transfer function elements of the respective individual recorded web tension actual value signals, predefined web tension values along the entire paper web path can be maintained within certain limits, whereby predetermined limit values are not exceeded or undershot. The above explanations apply both to a single web tension control at the infeed station and to a single web tension control at the extension train, wherein both web tension control systems can also be used in combination. Each of these web tension controls can, for example, an actual value F _IST , which is detected by any Bahnspannungsmeßsensor, after passing through a corresponding transfer function block as input used, of course, a weighted sum of several signals for a single web tension control can be used.

Cross-coupled web tension values of, for example, the infeed unit, the outfeed unit and the hopper infeed roller, but also other measuring points of the paper web, can also advantageously be used to control a web tension. In particular, the web tension control at the infeed unit is supplied with a value F _EW , which is preferably determined from cross-coupling of the measured web tension values F _IST at the infeed station, at the extension unit and at the hopper entry roller. The same applies to the web tension control at the extension work. For the embodiment with two control devices, the following matrix notation results for the values F _EW and F _AW supplied to the web tension control systems in the case of, for example, three web tension actual values to be taken into account: $$\left(\begin{array}{c}{\mathrm{F}}_{\mathrm{EW}}\\ {\mathrm{F}}_{\mathrm{AW}}\end{array}\right)=\left(\begin{array}{c}{\mathrm{<figure-callout\; id="1"\; label="\alpha "\; filenames="imgf0004.png"\; state="\{\{state\}\}">\alpha </figure-callout>}}_1{\mathrm{<figure-callout\; id="2"\; label="\alpha "\; filenames="imgf0006.png"\; state="\{\{state\}\}">\alpha </figure-callout>}}_2{\mathrm{<figure-callout\; id="3"\; label="\alpha "\; filenames="imgf0006.png"\; state="\{\{state\}\}">\alpha </figure-callout>}}_3\\ {\mathrm{\alpha }}_4\mathrm{}{\mathrm{<figure-callout\; id="5"\; label="\alpha "\; filenames="imgf0006.png"\; state="\{\{state\}\}">\alpha </figure-callout>}}_5\mathrm{}{\mathrm{\alpha }}_6\end{array}\right)\mathrm{}\left(\begin{array}{c}{\mathrm{F}}_{\mathrm{IS}\mathrm{,}\mathrm{EW}}\\ {\mathrm{F}}_{\mathrm{IS}\mathrm{,}\mathrm{AW}}\\ {\mathrm{F}}_{\mathrm{IS}\mathrm{,}\mathrm{TW}}\end{array}\right)$$

The coupling matrix for eg two web tension control systems, each of which takes into account three web tension actual values, consists of 2 × 3 = 6 elements, which are designated α ₁ to α ₆ . In this case, a matrix element α _i does not necessarily have to be a constant, but can also represent a dynamic transfer function. By such a web tension control device, consisting for example of two local web tension control devices for the infeed and extraction work with a coupling member, which is composed of several transfer functions, advantages can be achieved in certain operating conditions. For example, it is possible to regulate the web tension locally at the entrance and exit of the printing tower while at the same time taking into account the respective web tension actual values at the inlet and outlet of the printing tower. The aim of such a cross-coupled web tension control is to ensure the optimum web tension throughout the entire printing process over the entire paper web and to minimize cut register deviations therebetween, so that the individual Elements α _{i of} the coupling matrix must be set appropriately. Of course, such cross-coupling of at least two input signals of two different web tension sensors can also be used for only a single web tension control, but also for three or more web tension controls, optionally also the cylinder inside the printing tower. The number of measured input variables of the cross coupling, ie the measured web tension actual values, is not limited to three. It is also possible to use only two or more than three input signal actual values, with the measuring sensors then being suitably arranged in each case.

In the method according to the invention for regulating the tension of the paper web of a printing machine, a speed reference setpoint N _SOLL and a web tension setpoint value F _{SOLL are} specified. A first web tension actual value F _IST is measured. From the difference .DELTA.F between the web tension setpoint F _SOLL and the measured web tension actual value F _IST is determined by a web tension controller, a pre- or lag setpoint .DELTA.N _SET , depending on whether it is the extract or intake. In this case, the difference formed .DELTA.F z. B. serve a PI control algorithm to win a Nach- or Voreilungswert. The forward or lag setpoint .DELTA.N _SOLL is added to the rotational-speed N _SOLL or subtracted therefrom, and the obtained result is the speed used as an input variable of a control of a drive motor, which _{is provided} as a further input variable and a measured actual rotational speed value N can take into account. This inventive design of the paper web tension control, the same advantages, as described above in the control device according to the invention, can be obtained.

Preferably, at least one measured actual web tension value F _{IST is used,} for example, at the infeed station, the extension unit or the hopper inlet roller, whereby, of course, any combination of these actual web tension values, if necessary with prior loading with a suitable transfer function, as described above, is used for web tension control can be. In this case, the individual web tension actual value can also be cross-coupled, as described above, before they are used as an input variable for the control method.

As mentioned above, it is of course also possible to regulate either locally the web tension at the infeed station or at the extension unit or at both, wherein for the individual control methods the various input variables mentioned above can be used.

Fig. 1

eine erfindungsgemäße Bahnspannungsregeleinrichtung einer ersten Ausführungsform der Erfindung;

Fig. 2

eine erfindungsgemäße Bahnspannungsregeleinrichtung einer zweiten Ausführungsform der Erfindung;

Fig. 3

eine erfindungsgemäße Bahnspannungsregeleinrichtung einer dritten Ausführungsform der Erfindung;

Fig. 4a bis 4c

Bahnspannungsregelungen gemäß dem Stand der Technik; und

Fig. 5

ein Diagramm zur Veranschaulichung der Wirkungsweisen der Bahnspannungsregelungen gemäß den Figuren 4a bis 4c.

The invention will be described below with reference to preferred embodiments with reference to the accompanying drawings. Show it:

Fig. 1

a web tension control device according to the invention of a first embodiment of the invention;

Fig. 2

a web tension control device according to the invention of a second embodiment of the invention;

Fig. 3

a web tension control device according to the invention of a third embodiment of the invention;

Fig. 4a to 4c

Web tension control according to the prior art; and

Fig. 5

a diagram illustrating the effects of the web tension control according to Figures 4a to 4c.

As can be seen from FIG. 1, the speed reference setpoint N _SOLL and the web tension setpoint value F _{SOLL are} fed to the web tension control device by a machine controller via a real-time bus system. The web tension setpoint can also be supplied via analog or digital inputs without the use of a bus system. The actual web tension value F _IST measured by a web tension measuring sensor is subtracted from the web tension setpoint value F _SOLL , from which the web tension control deviation ΔF is obtained. This web tension control deviation .DELTA.F is fed to the web tension controller at the infeed station, which converts this into a lag setpoint .DELTA.N _SET . This lag setpoint .DELTA.N _SOLL is the measured actual rotational speed value N _associated with the obtained from the real-time bus system speed master N _SOLL and and the result is fed to the speed controller, wherein the motor for driving a roller of the draw-in mechanism, drives. The Drehzahlleitsollwert N _SOLL for the subordinate speed control loop is the controller thus from a suitable real-time bus, eg SERCOS supplied, so that an undisturbed reference signal as Drehzahlleitsollwert available, so that the web tension controller and the speed controller can be optimally matched.

Fig. 2 shows a second embodiment of the present invention, wherein as input parameters of the web tension control at the intake EW not only the measurement signal of the web tension sensor at the intake EW, but also measured signals from web tension sensors on the funnel inlet roller TW and the extension work AW recorded and each with coefficients α _TW , α _AW or α _{EW are} applied. These coefficients α _i can be constants, but these can also represent dynamic transfer functions. From the output signals These three signal weighting units or dynamic transmission elements α ₁ , a weighted sum signal Σ _{F is} formed, which is used as an input value for the web tension control of the feed train. Thus, a web tension control can be done only at the feed train, which can be maintained within predetermined limits by the arrangement shown in Fig. 2 arrangement of Bahnspannungsmeßsensoren and with a suitable choice of the weighting factors or transfer functions α _i and the web tension at the extension work or funnel inlet roller, so that despite certain disturbances caused by varying modulus of elasticity of the paper web, moisture, speed ramps or the like, the web tension can be kept in an optimum for the color and cut register area and tearing of the paper web can be reliably prevented. The other elements of the control device have been described in FIG. 1 and are not shown in FIG. 2.

Fig. 3 shows a third embodiment of the present invention, wherein the actual web tension values of the infeed and extracting in a coupling member are linked or calculated, so that the web tension control at the infeed or extracting the respective output signals of the coupling element F _EW or F _{AW be} supplied. The coupling member may weight the measured infeed and outfeed train voltage readings, and the individual signals may also be subjected to dynamic transfer functions so as to obtain the respective output signals, each representing a dynamic function of one or all of the input signals of the coupling member. With such an embodiment of the invention, for example, the web tension can be regulated locally at the entrance and at the exit of the printing tower, whereby in each case the corresponding web tension actual values are taken into account in order to obtain web tension values within predefined limits over the entire course of the paper web, so that the color and cut register can be kept optimal due to the held within certain barriers web stretches.

As determined from simulations, in the control according to the invention according to FIG. 1, in contrast to the lag control according to the prior art, the web tension is independent of the rotational speed, so that it can be kept within certain predetermined limits. When passing through a ramp, the force in front of the tower increases in the acceleration phase of the control according to the invention according to FIG. 1. This force difference serves to accelerate the guide rolls. After the tower, the paper web hangs between two nips, the last impression cylinder and the draw roller. This web force is from the lead of the draw roller and the paper transport, leading to a dependent speed function of the web tension at the output of printing tower F _AFTER. However, this can be prevented with an embodiment of the inventive arrangements according to the embodiments shown in Fig. 2 and Fig. 3.

However, it has been found that with the web tension control according to the invention, the deviation of the individual web tension at different points of the paper path can be kept within certain limits and when passing through a run-up ramp is not subject to such great deviations as in the lag control according to the prior art.

In a simulated comparison of the control according to the invention with a lag control according to the prior art in a pressure-off or pressure-on process was found that the fluctuations in the web tension at different locations are kept within relatively small limits with the inventive control whereas with the prior art retard control, there are significant variations in web tension at the individual locations.

By coupling according to the embodiment shown in Figure 2 and in particular by the cross-coupling described in connection with Figure 3 even improvements could be achieved.

Claims (7)

1. A printing machine driven without shafts having a draw-in mechanism and a draw-out mechanism with a motor for driving purposes in each case,
   characterised by
   a regulating device for controlling the respective motor for tensioning a paper web of a printing machine, comprising:

   - a setting device for a freely selectable rotational-speed guide-reference value (N_SOLL); and

   - a rotational-speed regulator for a drive motor which is coupled to the setting device for the rotational-speed guide-reference value (N_SOLL);

   - a setting device for a freely selectable web-tension reference value (F_SOLL);

   - a sensor for measuring the web tension (F_IST);

   - a web-tension regulator which is coupled to the sensor for measuring the web tension (F_1ST) and to the setting device for the web-tension reference value (F_SOLL); and

   - wherein the rotational-speed regulator is coupled to an output (ΔN_SOLL) of the web-tension regulator.
2. The regulating device according to claim 1, wherein the setting device for the web-tension reference value (F_SOLL) is a real-time bus system and/or for the rotational-speed guide-reference value (N_SOLL) is a bus system, in particular a real-time bus system.
3. The regulating device according to any one of the preceding claims, wherein a transfer element with a linear or a dynamic transfer function is provided, which acts on the output signal of the sensor.
4. The regulating device according to any one of the preceding claims, wherein at least two sensors are provided for measuring the web tension (F_IST) at different positions of the paper web, wherein the output signals of the individual sensors are coupled together and acted on by transfer functions, before they are passed to a local web-tension regulating means.
5. A method for regulating the tension of a paper web of a printing machine driven without shafts having a draw-in mechanism and a draw-out mechanism with a motor for driving purposes in each case, wherein the respective motor is controlled by:

   - simultaneously pre-setting a freely selectable rotational-speed guide-reference value (N_SOLL) and a freely selectable web-tension reference value (F_SOLL);

   - measuring a first web-tension actual value (F_IST);

   - forming the difference (ΔF) from the web-tension reference value (F_SOLL) and the measured web-tension actual value (F_IST);

   - converting the difference (ΔF) formed into a trailing or leading reference value (ΔN_SOLL); and

   - forming a value (ΔN), which serves to regulate the rotational speed of the drive motor, from the pre-set rotational-speed guide-reference value (N_SOLL) and the trailing or leading reference value (ΔN_SOLL).
6. The method according to claim 5, wherein the measured web-tension value or values (F_IST) are each acted on by a transfer function.
7. The method according to any one of claims 5 or 6, wherein at least two measured web-tension values (F_IST) are cross-coupled in order to deliver a web-tension actual-value signal for regulating the web tension.

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