EP0412448B1 - Drafting arrangement with meshed control - Google Patents

Description

The invention lies in the field of the textile industry and relates to a procedure for the control of a drafting system according to the generic terms of claims 1 and 7 respectively.

Various devices are available for making slivers even and regulations known based on the principle of warping the belts are based. As a rule, the tapes are relined and in a two-stage process Default process, a preliminary and a main default, evenly. As part of the default process, the production of one is possible homogeneous sliver aimed. In the corresponding drafting systems fall on the input side with irregularities or faults afflicted tapes, the output side to a tape with as much as possible uniform, predetermined cross section should be merged. This requirement requires regulation of the stretching process. To the booth The technology includes various drive arrangements as well as control and Control devices that address this problem.

So are open and closed control loops and their combinations known, which by measuring the output side cross-section or the cross-sections at the inlet supply the corresponding measurement parameters control or regulate the delay of the route by means of actuators. The Problems that arise when using open control loops are generally within the scope of control engineering and for the control of Stretching processes in particular known. It refers to Difficulties arising from the runtime between the measurement site and the actuator but also result from the missing feedback information, in which Process-specific problems also arise in connection with drafting systems. On the other hand, closed control loops are also problematic, because here e.g. because of the dead time between the measured variable and the actuator short-term failures cannot be compensated. Besides are measurement-related difficulties in the field of strip processing to overcome.

For example, a process is known from European patent application 0 176 661 and a device for optimizing the stretching process in regulating sections the textile industry with an open and a closed Loop known. Based on the difficulties mentioned above it is suggested in that document to have a feedback path between output measuring point and control circuit to provide and the Use feedback information to influence the control parameters. The generally known control concept sees a mathematical one Linking the input and output measurements using a cross correlation.

The consideration of both an output and one input-side measurand, as the state of the art shows basically to better regulate the uniformity of a sliver to lead. Meanwhile, by the known devices and Processes the technical and, above all, metrological special features disregarded, so these regulations despite additional Measures only deliver limited results. Such peculiarities when regulating routes also led to the plants be monitored during operation and certain parameters manually had to be adjusted or corrected. So there was a particular disadvantage in that dead time and / or gain is usually set manually and required adjustment during operation. This required continuous monitoring by an operator.

Further problems arise from the previous design of the drive arrangements and devices. The caused by the drives Disruptions and fluctuations were caused by the known regulations considered. However, it turns out that considering the corresponding disturbances within the scope of a single main or overall regulation a compensation of very large control ranges required which overwhelmed conventional devices. At the same time there is a disadvantage in that the entire computing load was concentrated and time dependencies the regulation were not optimized.

It is therefore an object of the invention, a route and a method for To create regulation of a route, which after setting the command variables for the control with an automated process flow allow optimized leveling of the belt.

This object is achieved in the characterizing part of the claims 1 or 7 mentioned features solved.

In the present invention, drive arrangement, control and Measuring system optimally coordinated, so that optimization equalization is achieved. At the same time it is possible that To regulate the system so that manual intervention is largely unnecessary. The previously required adjustments and adjustments of parameters during operation, made by operating personnel had to be and therefore an additional susceptibility to errors in itself salvage, largely eliminated.

Fig. 1 zeigt ein Streckwerk mit einem Vor- und Hauptverzugsabschnitt und den prinzipiellen Messeinrichtungen.

Fig. 2 zeigt einen Messwandler für das Einlaufmessorgan 9.1.

Fig. 3 zeigt das Funktionsprinzip des erfindungsgemässen Verfahrens

The method according to the invention and an exemplary embodiment of the device are explained in more detail with reference to the following figures.

Fig. 1 shows a drafting system with a preliminary and main drafting section and the basic measuring devices.

2 shows a measuring transducer for the inlet measuring element 9.1.

3 shows the principle of operation of the method according to the invention

Figure 1 shows a schematic representation of an embodiment the way. Several slivers 15.1-15.6, six in the example, are grouped together in a loose fleece and passed through several roller systems 1-6. Because of the peripheral speed of the rollers in the direction of transport of the fiber material in increases two stages, this is advanced over the first stage (early default), further warped to the desired cross-section (Main default). The fleece 18 emerging from the route is thinner than the fleece of the fed tapes 15.1-15.6 and correspondingly longer. The fact that the warping depending on the cross section of the fed tapes can be regulated, the tapes or the fleece is evened out as it passes through the route, this means that the cross-section of the emerging fleece is more even than the cross section of the fed fleece or the tapes. The present Route has a pre-default area 11 and a main default area 12 on. Of course, the invention can also be used in context with routes with only one or more than two warpage areas in be used in an analogous manner.

The belts 15.1-15.6 are fed into the line by two systems 1 and 2 of conveyor rollers. A first system 1 consists, for example, of two rollers 1.1 and 1.2, between which the fed belts 15.1-15.6, which are combined to form a looser fleece, are transported. In the transport direction of the belts, a roller system 2 follows, which here consists of an active conveyor roller 2.1 and two passive conveyor rollers 2.2, 2.3. During the feeding through the roller systems 1 and 2, the fed tapes 15.1-15.6 are brought together to form a fleece 16. The peripheral speeds v ₁ and v ₂ (= v _in ) of all the rollers of the two roller systems 1 and 2 of the feed are the same, so that the thickness of the fleece 16 essentially corresponds to the thickness of the strips 15.1-15.6 fed.

The two roller systems 1 and 2 of the feed are followed in the transport direction of the fleece 16 by a third system 3 of pre-drafting rollers 3.1 and 3.2, between which the fleece is transported on. The peripheral speed v _{3 of} the pre-drafting rollers is higher than that of the infeed rollers v _1,2 , so that the fleece 16 is stretched in the pre-drafting area 11 between the infeed rollers 2 and the pre-drafting rollers 3, its cross-section being reduced. At the same time, a pre-warped fleece 17 is created from the loose fleece 16 of the fed-in belts 17. The pre-drafting rollers 3 are followed by a further system 4 of, for example, an active conveyor roller 4.1 and two passive conveyor rollers 4.2, 4.3 for further transport of the fleece. The peripheral speed v _{4 of} the conveyor rollers 4 for further transport is the same as v _{3 of} the pre-drafting rollers 3.

The roller system for further transport 4 is followed by a fifth system 5 of main drafting rollers 5.1 and 5.2 in the transport direction of the fleece 17. The main drafting rollers in turn have a higher surface speed v ₅ than the preceding transport rollers 4, so that the pre-drawn fleece 17 between the transport rollers 4 and the main drafting rollers 5 is further drawn in the main drafting area 12 to the finished drawn fleece 18, the fleece 18 being closed via a funnel T. a volume is brought together.

Between a pair 6 of outlet rollers 6.1, 6.2, the circumferential speed v ₆ (= v _out ) of which is the same as that of the preceding main drafting rollers (v ₅ ), the finished stretched belt 18 is guided away from the draw frame and placed, for example, in rotating cans 13.

The roller systems 1, 2 and 4 are driven by a first motor 7.1 via a gear or preferably via toothed belts. The pre-drawing rollers 3 are mechanically coupled to the roller system 4, it being possible for the ratio with respect to the roller systems 1 and 2 to be adjustable or for a target value to be predetermined. The gear (not visible in the figure) determines the ratio of the peripheral speeds of the inlet rollers (v _in ) and the peripheral speed v _{3 of} the pre-drafting rollers 3.1, 3.2, hence the pre-drafting ratio. The inlet rollers 1.1, 1.2 can also be driven by the first motor 7.1 or optionally by an independent motor 7.3.

The roller systems 5 and 6 are in turn powered by a second motor 7.2 driven. The two motors 7.1 and 7.2 have according to the invention each with its own controller 8.1 or 8.2. The regulation takes place via a closed control loop 8.a, 8.b or 8.c, 8.d. It can also the actual value of one motor the other motor in one or both Directions are transmitted over a control link 8.e so each can react accordingly to the other's setpoint deviations.

The total cross-section of the fed-in is at the entrance of the line Bands 15.1-15.6 measured by an inlet measuring element 9.1. At the exit the cross section of the emerging belt 18 is then from an outlet measuring element 9.2 measured.

A central computer unit 10 transmits an initial setting of the Target size for the first drive 7.1 via 10.a to the first controller 8.1. The measured variables of the two measuring elements 9.1, 9.2 are during the Stretching process via the connections 9.a and 9.b continuously to the central Computer unit transmitted. From these measurement results and from the target value for the cross section of the emerging band 18 is in the central Computer unit and any other elements by means of the inventive The setpoint for the second drive 7.2 is determined. This setpoint is continuously sent to the second controller 8.2 via 10.b. given. With the help of this control system, fluctuations in Cross-section of the fed tapes 15.1 - 15.6 through appropriate regulation the main default process compensated or a leveling of the tape can be achieved.

Position controllers (not Speed controller), as this also works if the Motor ensure the regulation. The corresponding controllers 8.1, 8.2 (or any other controllers in the design variants) can separate computing units (e.g. with digital computing elements; Microprocessors) or as a module of the central Computer unit 10 can be executed.

The measuring principle will be explained in more detail below. In the illustrated embodiment of a controlled route, there should be a constant advance. The regulation of the strip cross-section or its equalization is thus essentially achieved by changing the warpage in the main warping area 12. The inlet measuring element 9.1 supplies the input-side measurement signal with the information about the cross section of the fed strips 15.1-15.6. Obtaining the desired run-in measurement signal is known to present measurement difficulties. A cross-sectional measurement without impairing the material and with high dynamics is difficult to do in the conventional way. As a consequence, an indirect measurement procedure must be carried out with a transducer. Various conventional converters provide insufficient results for the desired purpose. A measuring capacitor 21 according to FIG. 2 is therefore used in connection with this invention, through which the fed strips 15.1-15.6 run. This takes advantage of the fact that the volume of the strips between the capacitor plates, which fluctuates during the passage, causes a change in the dielectric. When these bands pass through the capacitor 21, a conclusion can be drawn about the dielectric when an alternating current U is applied, for example by measuring the voltage U across the capacitor. However, it must be taken into account that the moisture content of the tapes and other disturbances can have a major impact on the measurement, but the dielectric constant ε _Ψ of water is 81 compared to the dielectric constant of, for example, cotton ε _B , which is of the order of 4. In other words, the difficulty lies in obtaining the desired signal directly via the measuring transducer via the volume present in the capacitor at a certain point in time, which represents the total cross section of the tapes fed in. According to the invention, the voltage U across the capacitor is measured and the signal obtained is split into a real part R _x and an imaginary part C _x . As will be explained further below, these signals R _x and C _x are evaluated as part of the regulation, the outflow measurement signal being used in the process. The difficulties in the measurement on the input side are one reason why the control according to the invention is designed in such a way that measurement errors are compensated for in the context of an adaptive control.

The outlet measuring element 9.2 can be a conventional measuring instrument which delivers a signal A _out with the information about the cross section of the emerging belt 18. This signal is also subsequently used for the control. It should be noted that the required measurements can not only be carried out directly at the inlet and outlet, but it is only necessary that one measuring element is arranged before and one after the controlled system (in the control-technical sense), ie here the main warpage area 12. With regard to a favorable time dependency of the regulation, it would also be advantageous, for example, to arrange the input-side measuring element directly in front of the main delay area 12.

vorgesehen.It is assumed that both high and low frequency changes or unevenness of the belt should be corrected for an optimized control. The regulation is intended to keep the mean value of the strip as constant as possible (first priority) and to regulate unevenness. The relevant deviations in the controlled variable can be recorded as high- and low-frequency components of the measured controlled variables within the scope of the control. In terms of measurement and control technology, there is the problem of obtaining information about these variables and converting them into the desired manipulated variable. Especially in the case of the high-frequency changes, the running time between the measuring and actuator elements must be taken into account. On the input side, ie with the inlet measuring element 9.1, it is possible to obtain the high-frequency signal components. Because of the dead time of the regulation dependent on this output-side measurement by means of the outlet measuring element 9.2, only the low-frequency components of the signal can be compensated for in the context of the regulation. Problems and errors caused by measurement technology are now also taken into account in the control according to the invention by taking the measurement signals of the outlet measuring element 9.2 into account to adapt the control to measurement errors on the inlet side or other deviations. According to the invention, a map is preferably determined empirically and continuously adapted during operation

intended.

FIG. 3 illustrates the control principle and the method according to the invention in a schematic overview of the main control. The distance is indicated by arrows which indicate the direction of travel of the belt, as well as by two blocks for the pre-draft 11 and the main draft 12. The actual cross-section m _{E of} the strips at the inlet is represented by the size m _e , the actual cross-section m _{A of} the finished warped strip by the size m _a , which in the present example are the masses for a short strip gate Δl defined in each case. The belts are fed _in at the speed v _in at the inlet and the finished belt exits at the speed v _out . The size of the early draft K1 can be adjusted by means of a specification element 19. The controlled system (in the technical control sense) is formed here by the main delay area 12. The running time between the inlet measuring element 9.1 and the main drafting area 12 is identified by t1, that between the main drafting area and the outlet measuring element 9.2 by T2. The measured variables A _out , R _x and C _{x of} the measuring elements 9.1, 9.2 represent input variables of a control system. This contains a central computer unit 10 which contains the measured variables C _x , R _x , the temperature I _T and any further information I _1-n , such as humidity. The size A target _is specified as the reference variable.

For the sake of clarity, the control system is shown in the illustration in structured several "paths" 1-4. A first path 1 contains the central one Computer unit 10 with inlets and outlets as well as several timing elements Z1.1-Z3 and, according to the invention, is used to prepare the measurement data. On second path 2 is used to optimize the delay time t1. A third Path 3 is used to optimize the keeping of the band average and compensation for long-term disturbances. After all, is a fourth path 4 is provided, which optimizes short-term compensation Provides for disturbances. It is anticipated that preferably a digital control is used in the context of the invention. In order to it becomes possible to have all elements of the control system in one computer to realize. To illustrate the rule principle, the essential elements necessary for the explanation of the invention in FIG 3 schematically broken down.

Beginning at path 3 (constant of the average value) is a comparator 35 is provided the formation of a difference between the outlet signal A _out and the target value A _is performs. The deviation dA determined in this way is fed via an I-link 38 to an addition point 36. The signal Δm is formed by integrating the mean value deviations in an I element 38 and adding 1. In a second addition point 37, this deviation and the deviations Δh caused by short-term disturbances, which are determined in path 1 and 4 according to the following explanations, are added and finally the factor 1 + Δm + Δh multiplied in a multiplication point 39 by the predetermined nominal value K3 of the main delay. In the present exemplary embodiment, the variant with a multiplication point 39 was preferred, since the manipulated variable y is to be used here in the context of a division element (x / y) for controlling the main delay. The corresponding multiplication results in the manipulated variable y required for controlling the main delay.

The outflow measurement signal A _out is further fed to a high-pass element 47 of path 2. The filtered signal is squared at a multiplication point 40 and the signal ΔH is obtained therefrom, which indicates the high-frequency component of the mean value fluctuations. The high-frequency components, which in this exemplary embodiment are up to approximately 300 Hz, are taken into account for this path. The signal ΔH is fed to a first control element R1 with a transfer function to minimize ΔH. The output of the control element R1 forms the signal S _t1 , which optimizes the delay time of various time elements Z1.1, Z1.2, Z4 or is fed directly to the central computer unit (10). In a preferred embodiment of the method, an additional correction element (not shown here) is provided in path 2 for determining the delay time t1. This makes it possible, under certain conditions at the input, in particular in the event of a band break, to carry out a corrective control intervention by a certain, short time Δt1 reduced delay time t1 on the actuator. This enables a complete correction to be achieved in the event of abrupt irregularities in the inlet-side bands, with any overcompensation being accepted.

According to the invention, a map element 50 is provided as the connecting core of paths 1 and 4. This can be designed, for example, as a readable and readable memory and in turn can be integrated into the central computer unit 10. An empirically determined output map is in this map element stored with respect to the sizes R _x and C _x and refers to the size m e = f (R x , C x ) . The measured value pairs R _x , C _{x are} supplied to the map element 50 and this supplies the quantity m _e as the output signal. The map is continuously adjusted during operation. This adaptation takes place in path 1. In this exemplary embodiment, the signals R _x , C _x are fed into the central computer unit 10 with a delay in corresponding timing elements Z1.1-Z2.2. The timing elements Z1.1-Z2.2 serve to take into account the total running time t1 + T2 from the inlet to the outlet measuring element. The filtered variable m _{e / t1} , delayed taking into account the running time t1 and adjusted for delay in a division element 43, is fed to a further input of the central computer unit via a timing element Z3. The signal A _out with the information about the outlet band cross section m _A , represented by the measured quantity m _a , also forms an input of the computer unit 10. The quantity m _a is preferably also filtered before it is fed to the central computer unit 10, wherein in a corresponding filter 46 of path 1, the low-frequency signal components are cut. Instead of using these timing elements Z1.1-Z3, the transit time t1 can also be taken into account directly by the central computer unit by supplying the output signal S _t1 of path 2 to it.

All signals supplied to the computer unit are used in the following for cleaning the map of the map element 50 is used by the output of the computer unit 10 in the map element 50, the (effective) size m _e determined by evaluating the measurement data being transmitted to the respective pair of values C _x , R _x . This is a permanent adaptation of the map guaranteed changes within the control process. It can be seen that the central computer unit 10 must at least evaluate the signals m _e , R _x , C _x and m _{a in} order to ensure the map adaptation. The mentioned additional measurement data I _T , I _1-n can, however, bring about a further improvement in the control under certain conditions.

Similar to path 2, path 4 provides for filtering the signal A _out , but this time with a bandpass element 48 instead of a highpass element. A multiplication point 41 and a control element R2 for minimizing the corresponding signal ΔB are connected downstream of the ban element 48. The control element R2 provides at its output a factor f _B , which is linked in a multiplication point 42 with the signal m _{e / t1} . This signal m _{e / t1} is present at the output of a filter 49, to which the signal m _e from the map element 50 is fed via a timing element Z4. This filter 49 cuts the low-frequency signal components. Path 4 further contains a threshold switch 25 with an adjustable default value δ. If the signal m _{e / t1 is} below this preset value δ, the switch is in a first position p1. As soon as the specified value δ is exceeded, ie large fluctuations of m _e around the mean value occur, the switch switches to a position p2 in which the signal m _{e / t1} is looped directly to path 3, so that these fluctuations are fully taken into account for the main delay . However, if the values for m _{e / t1} are below this default value δ, path 4 is optimized. The signal m _{e / t1} is multiplied in the multiplication point 42 by the factor f _B determined by means of the minimization function of the control element R2 and the output signal of the multiplication point is fed to the path 3 via the switch 25. The switchover by means of the threshold switch 25 and the consideration of the optimization by the control element R2 prevents that, in the case of small and very small, short-term mean value deviations, any interference, for example caused by noise, is introduced into the path 3.

At the same time, the threshold switch serves to switch the optimization on or off by means of the control elements R1, R2. If m _e lies above the preset value δ, the optimization of the control elements R1, R2 is switched off, otherwise switched on. It is not absolutely necessary to switch off the respective optimization brought about by the control elements R1, R2 when the preset value δ is exceeded, since the corresponding regulation can also run away by means of compensation elements. In the context of digital regulation, however, the corresponding regulations can be switched on and off as simply as possible, so this variant is preferred.

The threshold switch can also be implemented by a non-linear element or in the map be integrated. In the latter case, in addition to the output variable m _e , the map element 50 also supplies the signal required for activating or deactivating the optimization of the control elements R1, R2 or an amplitude-dependent parameter.

In the present embodiment, the high pass member of the path 2 for example frequencies above 100 Hz, the bandpass those in the range of 10-100 Filter Hz. The frequency ranges depend on the throughput speed of the tapes in the area above around 600 m / min. was accepted.

It must be noted that the transfer functions of the control elements R1, R2 can vary depending on the design of the control system. In a preferred embodiment of the invention, the filters of the paths 2 and 4 are omitted and the transfer functions are determined instead that the frequencies in question are required be taken into account. Of course, the filter 46 of the Path 1 is omitted and the filtering can be done as part of the central Computer unit 10 can be realized. Because of the possibility of change the parameters of the corresponding transfer functions also exist the advantage of being able to adapt to different operating conditions (e.g. variable throughput speed of the belts) can be.

A special embodiment sees an adaptive adaptation in this sense the control parameters. The parameters of the transfer functions the control elements R1, R2 are changed in the course of the control, so that the variation of the manipulated variable is minimized. The parameters of the transfer functions are in such an embodiment by the Central computer unit 10 determined from the measurement parameters. With the adaptive Regulation must attach great importance to stability.

The central computer unit 10 is preferably a digital one Computing element realized. It is obvious that the explanation of the principle of the method, the functions of the various functions explicitly shown Paths 1-4 in Figure 3 partially or entirely in a uniform Computer can be integrated.

The output map for _me can be determined, for example, by static measurements on the measuring capacitor 21 and then stored in tabular form. It should be noted that in the case of modified measuring methods, other characteristic maps must be determined. The principle according to the invention can therefore also be carried out with corresponding characteristic maps for other inlet and outlet measurement signals.

The control principle according to the invention ensures very good evenness even in the event of unforeseen changes in operating conditions. In particular, there are also measurement errors in the frame on the inlet side the regulation compensated. Both short-term disruptions as well slow changes can be optimally compensated within the scope of this regulation become. If the described procedure for the main regulation of the Drafting system in connection with the auxiliary regulation of the independent Drive groups combined and a correspondingly meshed control provided, there are particularly favorable conditions. By the control variable y determined is therefore the setpoint for the controller 8.2 of the drive used for the main warping area 12.

For the sake of completeness, it should only be mentioned here that the Process according to the invention Regulation for all devices of the textile industry own, which require regulation of a stretching process and not on the route mentioned in the description is limited.

Claims (15)

1. Procedure for controlling a drafting unit with a measuring element at the inlet of the drafting unit and a measuring element at the outlet of the drafting unit, supplying measuring signals for a closed-loop and an open-loop control circuit, where the outlet measuring signal (A_out) is used for the purpose of adapting the control parameters of least one control element (50, R₁, R₂), characterized such that the measuring signal (A_out) on the outlet side is used for adapting a family of characteristics (R) for the measuring signal (C_x, R_x) of the measuring element (9.1) on the inlet side.
2. Procedure in accordance with claim 1 characterized by the following steps:

   a. The inlet measuring signal (R_x, C_x) is fed in the form of an input variable to a family of characteristics (R) and a central processor unit (10);

   b. The outlet measuring signal (A_out) is routed to the central processor unit;

   c. With the family of characteristics (R), the inlet measuring signal (R_x, C_x) is converted into a signal (m_e) representing the inlet band cross section and indicating the short-term irregularities of the bands at the inlet;

   d. This signal (m_e) is corrected with regard to the draft section and routed to the central processor unit (10);

   e. By using this signal (m_e), the outlet measuring signal (A_out) as well as the inlet measuring signal (R_x, C_x), the effective dependency of the inlet band cross section (m_e) on the inlet measuring signal (R_x, C_x) is determined in the central processor unit (10) and to the family of characteristics (R) is adapted.
3. Procedure in accordance with claim 2 characterized such that additional input variables (I_T, I_1-n) that are used for the purpose of adaptation of the family of characteristics are routed to the central processor unit (10).
4. Procedure for controlling a drafting unit in accordance with one of the claims 1 to 3 characterized such that the outlet measuring signal (A_out) is used for controlling the short-term mean fluctuations of the band as follows:

   a. The outlet measuring signal (A_out) is routed to a first control element (R1) having a transmission function that minimizes the high frequency components of this signal (A_out) for the purpose of determining the dead time (t1);

   b. The outlet measuring signal (A_out) is routed to a second control element (R2) having a transmission function that minimizes the mean frequency components of this signal (A_out) for the purpose of determining the gain factor (f_B)
5. Procedure in accordance with claim 4 characterized such that a high-pass filter is used in the 100 - 300 Hz range for the purpose of obtaining the high frequency components for the first control element (R1).
6. Procedure in accordance with claim 4 or 5 characterized such that a bandpass filter is used in the 10 - 100 Hz range for the purpose of obtaining the mean frequency components for the second control element (R2).
7. Procedure for controlling a drafting unit with a measuring element at the inlet of the drafting unit and a measuring element at the outlet of the drafting unit supplying measuring signals for a closed-loop and an open-loop control circuit characterized such that

   a. a signal (m_e) representing the inlet band cross section is either routed directly back to the control element by means of a trigger (25) dependent on a setpoint (δ), provided this setpoint (δ) is exceeded, or is multiplied by a control gain factor (f_B) in a logic element (42) and the resulting signal is routed back to the control element provided the setpoint (δ) is not reached;

   b. optimisation of the control gain as well as the delay time is deactivated as soon as the signal (m_e) representing the inlet band cross section exceeds the setpoint δ) and is activated as soon as this signal (m_e) falls short of this setpoint (δ);

   c. the optimised outputs signal (Δh) representing short-term deviations and determined in accordance with a. and a signal (Δm) representing the slow deviations of the outlet band diameter (m_A) are added and influence the control variable (HV(1+Δm+Δh).
8. Procedure in accordance with claim 4 and 7 characterized such that the optimisation achieved by the two control elements (R1, R2) is switched off as soon as the signal (m_e) representing the inlet band cross section exceeds the setpoint (δ) and is switched on as soon as this signal (m₂) falls short of this setpoint (δ).
9. Procedure in accordance with claim 1 or 7 characterized such that the measuring element (9.1) on the inlet side is designed as a measuring capacitor (21), with which the change in the dielectric caused by the passing of the fed bands (15.1 - 15.6) is measured by measuring the voltage U across the capacitor.
10. Procedure in accordance with claim 9 characterized such that the measured change in voltage is split into a real component (R_x) and an imaginary component (C_x) of the signal that is routed to the family of characteristics (R) and to the central processing unit.
11. Procedure in accordance with one of the claims 1 - 10 characterized such that the inlet measuring signal (R_x, C_x) as well as the draft-corrected signal (m_e/t1) representing the inlet band cross section (m_e) is routed to the central processor unit (10) with a delay (t1, t2) corresponding to the running period between the inlet measuring element (9.1) and the outlet measuring element (9.2).
12. Procedure in accordance with one of the claims 1 - 11 characterized such that the operating time (t1) between the inlet measuring element (9.1) and the main draft area (12) and/or the running period (t2) between the main draft area (12) and the outlet measuring element (9.2) is taken into account by the central processor unit (10).
13. Procedure in accordance with one of the claims 1 - 12 characterized such that the controlled variable (HV(1+Δm+Δh)) of the main control influences the setpoint for at least one secondary controlled drive group of a draft area (12) with a specified nominal draft (K3).
14. Procedure in accordance with one of the claims 1 - 13 characterized such that a drafting unit is controlled in accordance with one of the claims 1 to 5 by means of the procedure.
15. Procedure in accordance with one of the claims 1 - 13 characterized such that a drafting unit integrated on a tie-up jacquard is controlled by means of the procedure.

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