WO2012001211A1 - A method and a system for determining eccentricity - Google Patents

A method and a system for determining eccentricity Download PDF

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Publication number
WO2012001211A1
WO2012001211A1 PCT/FI2010/050557 FI2010050557W WO2012001211A1 WO 2012001211 A1 WO2012001211 A1 WO 2012001211A1 FI 2010050557 W FI2010050557 W FI 2010050557W WO 2012001211 A1 WO2012001211 A1 WO 2012001211A1
Authority
WO
WIPO (PCT)
Prior art keywords
machine reel
torque
eccentricity
indicative
temporal cycle
Prior art date
Application number
PCT/FI2010/050557
Other languages
French (fr)
Inventor
Teppo Kojo
Petri Enwald
Original Assignee
Metso Paper, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Metso Paper, Inc. filed Critical Metso Paper, Inc.
Priority to PCT/FI2010/050557 priority Critical patent/WO2012001211A1/en
Publication of WO2012001211A1 publication Critical patent/WO2012001211A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
    • B65H23/00—Registering, tensioning, smoothing or guiding webs
    • B65H23/04—Registering, tensioning, smoothing or guiding webs longitudinally
    • B65H23/18—Registering, tensioning, smoothing or guiding webs longitudinally by controlling or regulating the web-advancing mechanism, e.g. mechanism acting on the running web
    • B65H23/182—Registering, tensioning, smoothing or guiding webs longitudinally by controlling or regulating the web-advancing mechanism, e.g. mechanism acting on the running web in unwinding mechanisms or in connection with unwinding operations
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
    • B65H2301/00—Handling processes for sheets or webs
    • B65H2301/40—Type of handling process
    • B65H2301/41—Winding, unwinding
    • B65H2301/414—Winding
    • B65H2301/4148—Winding slitting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
    • B65H2511/00—Dimensions; Position; Numbers; Identification; Occurrences
    • B65H2511/10—Size; Dimensions
    • B65H2511/16—Irregularities, e.g. protuberances
    • B65H2511/166—Irregularities, e.g. protuberances relative to diameter, eccentricity or circularity
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
    • B65H2513/00—Dynamic entities; Timing aspects
    • B65H2513/10—Speed
    • B65H2513/11—Speed angular
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
    • B65H2513/00—Dynamic entities; Timing aspects
    • B65H2513/20—Acceleration or deceleration
    • B65H2513/23—Acceleration or deceleration angular
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
    • B65H2515/00—Physical entities not provided for in groups B65H2511/00 or B65H2513/00
    • B65H2515/30—Forces; Stresses
    • B65H2515/32—Torque e.g. braking torque
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
    • B65H2601/00—Problem to be solved or advantage achieved
    • B65H2601/50—Diminishing, minimizing or reducing
    • B65H2601/52—Diminishing, minimizing or reducing entities relating to handling machine
    • B65H2601/524—Vibration

Definitions

  • the invention relates to a method and a system for determining eccentricity of a machine reel.
  • the invention relates also to an unwinding station.
  • the measured information is utilized in detecting possible too large vibrations exceeding a predetermined threshold value and then reducing the speed of the unwound fibre web in order to avoid possible damages or fibre web breaks.
  • the vibration sensors may be, however, sensitive components and furthermore special mechanical constructions are usually needed for the vibration sensors. Especially, it might be challenging to install the vibration sensors as retrofits into existing, already commissioned systems. Also publications JP63267650 and WO2004/044316 disclose technical solutions based on the vibration sensors.
  • a new method for determining eccentricity of a rotating machine reel comprises:
  • the quantity indicative of the eccentricity can be determined from the torque signal using suitable signal processing methods, e.g. by multiplying the torque signal with a sinusoidal signal having a temporal cycle equal to the temporal cycle of revolu- tion of the machine reel and low-pass filtering the result of the multiplication.
  • An estimate of the vibration prevailing at each situation can be obtained on the basis of the quantity indicative of the eccentricity, and if the estimate of the vibration exceeds a pre-determined threshold value, the speed of the unwound fibre web can be reduced in order to avoid possible damages or fibre web breaks. It is also possible to control the rotational speed and/or angular acceleration of the machine reel directly on the basis of the quantity indicative of the eccentricity using suitable pre-stored information.
  • the torque acting on the machine reel can be monitored, for example but not necessarily, with the aid of a control circuitry of an electrical drive connected to the machine reel.
  • the electrical drive can comprise, for example but not necessarily, an alternating current motor fed and controlled with a frequency converter. In this case, the torque can be monitored with the frequency converter.
  • the method according to the invention can be more easily taken into use also in conjunction with existing, already commissioned systems than the prior art methods based on the vibration sensors.
  • a new sys- tem for determining eccentricity of a machine reel comprising:
  • - processing equipment for determining, from the torque signal, a quantity proportional to an amplitude of an alternating torque component having a temporal cycle equal to a temporal cycle of revolution of the machine reel, wherein the determined quantity is indicative of the eccentricity of the machine reel.
  • the device for monitoring the torque and the processing equipment can be, for example but not necessarily, sensors and processors of a frequency converter of an electrical drive connected to the machine reel.
  • the unwinding station comprises:
  • a braking generator for maintaining tension of a fibre web to be unwound from a machine reel
  • a device for monitoring torque of the braking generator and producing a torque signal representative of the torque as a function of time and - processing equipment for determining, from the torque signal, a quantity proportional to an amplitude of an alternating torque component having a temporal cycle equal to a temporal cycle of revolution of the machine reel, wherein the determined quantity is indicative of the eccentricity of the ma- chine reel.
  • the unwinding station comprises the braking generator for maintaining the tension of the fibre web to be unwound from the machine reel and a system according to the invention for determining the eccentricity of the machine reel.
  • figure 1 shows a schematic illustration of an unwinding station according to an embodiment of the invention
  • figure 2 shows a schematic illustration of a system according to an embodiment of the invention for determining eccentricity of a machine reel
  • figure 3 shows a flow chart of a method according to an embodiment of the invention for determining eccentricity of a machine reel.
  • Figure 1 shows a schematic illustration of an unwinding station 100 according to an embodiment of the invention.
  • Figure 1 shows also schematic illustrations of a winding station 1 10 and a slitter 120 situated between the unwinding station and the winding station.
  • the winding station comprises an electrical motor 1 14 for rotating a roll 1 1 1 so that a fibre web 107 is unwound from a machine reel 101 of the unwinding station and wound to the roll of the winding station.
  • the electrical motor 1 14 driving the roll 1 1 1 is connected to an electrical grid 105 with a control unit 1 12.
  • the unwinding station 100 comprises a braking generator 104 for maintaining tension T of a fibre web.
  • the braking generator 104 is mechanically connecter to the machine reel and electrically connected, with a control unit 108, to the electrical grid 105.
  • the unwinding station comprises a device 102 for monitoring instan- taneous torque of the braking generator and for producing a torque signal representative of the torque as a function of time.
  • the unwinding station comprises processing equipment 103 for determining, from the torque signal, a quantity proportional to amplitude of an alternating torque component having a temporal cycle equal to a temporal cycle of revolution of the machine reel 101 .
  • the determined quantity is indicative of the eccentricity of the machine reel 101 and it can be determined from the torque signal using suitable signal processing methods. Two examples of suitable signal processing methods are given below.
  • the processing equipment 103 is arranged to multiply the torque signal with a sinusoidal signal having a temporal cycle equal to the temporal cycle of revolution of the machine reel and to low-pass filter the result of the multiplication.
  • the result of the low-pass filtering is the quantity indicative of the eccentricity of the machine reel.
  • the processing equipment 103 is arranged to band-pass filter the torque signal so that a center frequency of the band-pass filtering corresponds to the temporal cycle of revolution of the machine reel.
  • the amplitude of the result of the band-pass filtering is the quantity indicative of the eccentricity of the machine reel.
  • the electrical motor 1 14 of the winding station can be driven in a speed controlled mode so as to keep the speed v of the fibre web sufficiently near to its reference value, and the braking generator 104 of the unwinding station can be driven in a torque controlled mode so as to keep the tension T of the fibre web sufficiently near to its reference value.
  • the quantity proportional to the amplitude of the alternating torque component having the temporal cycle equal to the temporal cycle of revolution of the machine reel can be extracted, for example, from an error signal supplied to a torque regulator of the control unit 108, wherein the error signal is the difference between the torque and its reference value.
  • the torque regulator can be tuned to be so slow that an alternating component of the error signal having a temporal cycle equal to the temporal cycle of revolution of the machine reel is not suppressed too much, or the torque regulator can be otherwise prevented from suppressing the said alternating component of the error signal too much, e.g. by band-stop filtering the error signal so as to make the torque regulator blind for the said alternating component of the error signal.
  • the electrical motor 1 14 of the winding station is driven in the torque controlled mode so as to keep the tension T of the fibre wed sufficiently near to its reference value, and the braking generator 104 of the unwinding station is driven in the speed controlled mode so as to keep the speed v of the fibre web sufficiently near to its reference value.
  • the quantity proportional to the amplitude of the alternating torque component having the temporal cycle equal to the temporal cycle of revolution of the machine reel can be extracted from the estimated or measured torque that is preferably used in an inner control loop the speed regulation of the braking generator 104.
  • the torque directed to the machine reel 101 can be estimated, for example, using values of electrical currents and voltages supplied to the braking generator 104. At least in principle, it is also possible to provide a shaft 106 between the braking generator and the machine reel with a strain gauge and with slip rings for taking out a signal representative of the torque. In the exemplifying case shown in figure 1 , the torque is estimated from the values of the electrical currents and voltages supplied to the braking generator with the device 102 that is a part of the control unit 108. As evident from above, this is, however, not the only possible implementation.
  • the braking generator 104 can be, for example, an alternating current machine such as an induction machine or a permanent magnet machine, and the unwinding station may comprise a frequency converter for controlling the braking generator.
  • the control unit 108, the device 102 for monitoring torque, and the processing equipment 103 are, preferably but not necessarily, implemented with processing and sensor circuitries of the frequency converter.
  • the braking generator 104 can be a direct current commutator machine controlled with rectifying bridges.
  • the processing equipment 103 is arranged to control a rotational speed and/or an angular acceleration of the machine reel on the basis of the quantity indicative of the eccen- tricity of the machine reel in order to limit the rotational speed and/or the angular acceleration when vibrations caused by the eccentricity would otherwise, i.e. without limiting the rotational speed and/or the angular acceleration, cause a fibre web break and/or other damages.
  • a signal for controlling the rotational speed and/or the angular acceleration is supplied to the control unit 1 12 of the winding station.
  • the control- ling of the rotational speed and/or the angular acceleration can be carried out locally in the unwinding station.
  • FIG. 2 shows a schematic illustration of a system according to an embodiment of the invention for determining eccentricity of a machine reel 201 .
  • the system comprises a device 202 for monitoring torque acting on the machine reel and producing a torque signal representative of the torque as a function of time.
  • the system comprises processing equipment 203 for determining, from the torque signal, a quantity proportional to the amplitude of an alternating torque component having a temporal cycle equal to a temporal cycle of revolution of the machine reel.
  • the determined quantity is indicative of the eccentricity of the machine reel.
  • the processing equipment 203 is arranged to multiply the torque signal with a sinusoidal signal having a temporal cycle equal to the temporal cycle of revolution of the machine reel and to low-pass filter the result of the multiplication.
  • the result of the low-pass filtering is the above-mentioned quantity indicative of the eccentricity of the machine reel.
  • the processing equipment 203 is arranged to band-pass filter the torque signal so that a center frequency of the band-pass filtering corresponds to the temporal cycle of revolution of the machine reel.
  • the amplitude of the result of the band-pass filtering is the above-mentioned quantity indicative of the eccentricity of the machine reel.
  • the device 202 for monitoring the torque is arranged to monitor the torque from a braking generator of an unwinding station for unwinding a fibre web from the machine reel.
  • the system can be a part of the unwinding station as illustrated in figure 1
  • the processing equipment can be further arranged to control a rotational speed and/or an angular acceleration of the machine reel on the basis of the quantity indicative of the eccentricity of the machine reel.
  • the system is not only a system for determining the eccentricity but a system for controlling the rotation of the machine reel.
  • Figure 3 shows a flow chart of a method according to an embodiment of the invention for determining eccentricity of a rotating machine reel. The method comprises: - monitoring, in a phase 301 , torque acting on the machine reel,
  • the determining of the quantity indicative of the eccentricity of the machine reel comprises multiplying the torque signal with a sinusoidal signal having a temporal cycle equal to the temporal cycle of revolution of the machine reel and low-pass filtering the result of the multiplication, wherein the result of the low-pass filtering is the quantity indicative of the eccentricity of the machine reel.
  • the determining of the quantity indicative of the eccentricity of the machine reel comprises band-pass filtering the torque signal with a band-pass filter having a center frequency corresponding to the temporal cycle of revolution of the machine reel, wherein the amplitude of the result of the band-pass filtering is the quantity indicative of the ec- centricity of the machine reel.
  • the torque is monitored from a braking generator of an unwinding station when a fibre web is being unwound from the machine reel.
  • the method may further comprise controlling a rotational speed and/or an angular acceleration of the machine reel on the basis of the quantity indicative of the eccentricity of the machine reel.
  • the method is not only a method for determining the eccentricity but a method for controlling the rotation of the machine reel.
  • the quantity indicative of the eccentricity of the machine reel is determined prior to an unwinding- winding process, and the quantity indicative of the eccentricity is later used for controlling the unwinding-winding process.

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Abstract

A method for determining eccentricity of a machine reel comprises: monitoring (301) torque acting on the machine reel, producing (302) a torque signal representative of the torque as a function of time, and determining (303) from the torque signal a quantity proportional to an amplitude of an alternating torque component having a temporal cycle equal to a temporal cycle of revolution of the machine reel. The determined quantity is indicative of the eccentricity of the machine reel and can be used for controlling the rotational speed and/or the angular acceleration of the machine reel so as to avoid damages and fibre web breaks which otherwise might be caused by vibrations due to the eccentricity.

Description

A method and a system for determining eccentricity
Field of the invention
The invention relates to a method and a system for determining eccentricity of a machine reel. The invention relates also to an unwinding station.
Background
The eccentricity of a machine reel is a considerable source of vibrations which, in turn, may cause for example breaking of a fibre web, shortening of life-times of devices, and various other undesirable effects. In conjunction with an unwinding station, the control of vibrations and ensuing effects has traditionally been dependent on the skills and reaction speeds of the personnel running and monitoring the unwinding station. Therefore, there has been a tendency to develop technical solutions for automatic control of rotational speed and/or angular acceleration of the machine reel so as to avoid the harmful effects caused by the eccentricity. Publication EP2014591 A2 discloses a system in which an unwinding station is provided with vibration sensors arranged to measure vibrations in one or more directions perpendicular to the rotating axis of a machine reel. The measured information is utilized in detecting possible too large vibrations exceeding a predetermined threshold value and then reducing the speed of the unwound fibre web in order to avoid possible damages or fibre web breaks. The vibration sensors may be, however, sensitive components and furthermore special mechanical constructions are usually needed for the vibration sensors. Especially, it might be challenging to install the vibration sensors as retrofits into existing, already commissioned systems. Also publications JP63267650 and WO2004/044316 disclose technical solutions based on the vibration sensors.
Summary
The following presents a simplified summary in order to provide a basic understanding of some aspects of various invention embodiments. The summary is not an extensive overview of the invention. It is neither intended to identify key or critical elements of the invention nor to delineate the scope of the invention. The following summary merely presents some concepts of the invention in a simplified form as a prelude to a more detailed description of exemplifying embodiments of the invention.
In accordance with the first aspect of the invention there is provided a new method for determining eccentricity of a rotating machine reel. The method according to the invention comprises:
- monitoring torque acting on the rotating machine reel, - producing a torque signal representative of the torque as a function of time, and
- determining, from the torque signal, a quantity proportional to an amplitude of an alternating torque component having a temporal cycle equal to a temporal cycle of revolution of the machine reel, wherein the determined quantity is indicative of the eccentricity of the machine reel.
The quantity indicative of the eccentricity can be determined from the torque signal using suitable signal processing methods, e.g. by multiplying the torque signal with a sinusoidal signal having a temporal cycle equal to the temporal cycle of revolu- tion of the machine reel and low-pass filtering the result of the multiplication.
An estimate of the vibration prevailing at each situation can be obtained on the basis of the quantity indicative of the eccentricity, and if the estimate of the vibration exceeds a pre-determined threshold value, the speed of the unwound fibre web can be reduced in order to avoid possible damages or fibre web breaks. It is also possible to control the rotational speed and/or angular acceleration of the machine reel directly on the basis of the quantity indicative of the eccentricity using suitable pre-stored information. The torque acting on the machine reel can be monitored, for example but not necessarily, with the aid of a control circuitry of an electrical drive connected to the machine reel. The electrical drive can comprise, for example but not necessarily, an alternating current motor fed and controlled with a frequency converter. In this case, the torque can be monitored with the frequency converter.
As there is no need to install vibration sensors, the method according to the invention can be more easily taken into use also in conjunction with existing, already commissioned systems than the prior art methods based on the vibration sensors.
In accordance with the second aspect of the invention there is provided a new sys- tem for determining eccentricity of a machine reel. The system according to the invention comprises:
- a device for monitoring torque acting on the machine reel and producing a torque signal representative of the torque as a function of time,
- processing equipment for determining, from the torque signal, a quantity proportional to an amplitude of an alternating torque component having a temporal cycle equal to a temporal cycle of revolution of the machine reel, wherein the determined quantity is indicative of the eccentricity of the machine reel.
The device for monitoring the torque and the processing equipment can be, for example but not necessarily, sensors and processors of a frequency converter of an electrical drive connected to the machine reel.
In accordance with the third aspect of the invention there is provided a new unwinding station. The unwinding station according to the invention comprises:
- a braking generator for maintaining tension of a fibre web to be unwound from a machine reel, and
- a device for monitoring torque of the braking generator and producing a torque signal representative of the torque as a function of time, and - processing equipment for determining, from the torque signal, a quantity proportional to an amplitude of an alternating torque component having a temporal cycle equal to a temporal cycle of revolution of the machine reel, wherein the determined quantity is indicative of the eccentricity of the ma- chine reel.
Therefore, the unwinding station according to the invention comprises the braking generator for maintaining the tension of the fibre web to be unwound from the machine reel and a system according to the invention for determining the eccentricity of the machine reel. A number of exemplifying embodiments of the invention are described in accompanied dependent claims.
Various exemplifying embodiments of the invention both as to constructions and to methods of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplifying em- bodiments when read in connection with the accompanying drawings.
The verb "to comprise" is used in this document as an open limitation that neither excludes nor requires the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Brief description of the figures
The exemplifying embodiments of the invention and their advantages are explained in greater detail below with reference to the accompanying drawings, in which: figure 1 shows a schematic illustration of an unwinding station according to an embodiment of the invention, figure 2 shows a schematic illustration of a system according to an embodiment of the invention for determining eccentricity of a machine reel, and figure 3 shows a flow chart of a method according to an embodiment of the invention for determining eccentricity of a machine reel.
Description of the exemplifying embodiments
Figure 1 shows a schematic illustration of an unwinding station 100 according to an embodiment of the invention. Figure 1 shows also schematic illustrations of a winding station 1 10 and a slitter 120 situated between the unwinding station and the winding station. The winding station comprises an electrical motor 1 14 for rotating a roll 1 1 1 so that a fibre web 107 is unwound from a machine reel 101 of the unwinding station and wound to the roll of the winding station. The electrical motor 1 14 driving the roll 1 1 1 is connected to an electrical grid 105 with a control unit 1 12. The unwinding station 100 comprises a braking generator 104 for maintaining tension T of a fibre web. The braking generator 104 is mechanically connecter to the machine reel and electrically connected, with a control unit 108, to the electrical grid 105. The unwinding station comprises a device 102 for monitoring instan- taneous torque of the braking generator and for producing a torque signal representative of the torque as a function of time. The unwinding station comprises processing equipment 103 for determining, from the torque signal, a quantity proportional to amplitude of an alternating torque component having a temporal cycle equal to a temporal cycle of revolution of the machine reel 101 . The determined quantity is indicative of the eccentricity of the machine reel 101 and it can be determined from the torque signal using suitable signal processing methods. Two examples of suitable signal processing methods are given below.
In an unwinding station according to an embodiment of the invention, the processing equipment 103 is arranged to multiply the torque signal with a sinusoidal signal having a temporal cycle equal to the temporal cycle of revolution of the machine reel and to low-pass filter the result of the multiplication. The result of the low-pass filtering is the quantity indicative of the eccentricity of the machine reel.
In an unwinding station according to another embodiment of the invention, the processing equipment 103 is arranged to band-pass filter the torque signal so that a center frequency of the band-pass filtering corresponds to the temporal cycle of revolution of the machine reel. The amplitude of the result of the band-pass filtering is the quantity indicative of the eccentricity of the machine reel.
The electrical motor 1 14 of the winding station can be driven in a speed controlled mode so as to keep the speed v of the fibre web sufficiently near to its reference value, and the braking generator 104 of the unwinding station can be driven in a torque controlled mode so as to keep the tension T of the fibre web sufficiently near to its reference value. The quantity proportional to the amplitude of the alternating torque component having the temporal cycle equal to the temporal cycle of revolution of the machine reel can be extracted, for example, from an error signal supplied to a torque regulator of the control unit 108, wherein the error signal is the difference between the torque and its reference value. The torque regulator can be tuned to be so slow that an alternating component of the error signal having a temporal cycle equal to the temporal cycle of revolution of the machine reel is not suppressed too much, or the torque regulator can be otherwise prevented from suppressing the said alternating component of the error signal too much, e.g. by band-stop filtering the error signal so as to make the torque regulator blind for the said alternating component of the error signal. It is also possible that the electrical motor 1 14 of the winding station is driven in the torque controlled mode so as to keep the tension T of the fibre wed sufficiently near to its reference value, and the braking generator 104 of the unwinding station is driven in the speed controlled mode so as to keep the speed v of the fibre web sufficiently near to its reference value. In this case, the quantity proportional to the amplitude of the alternating torque component having the temporal cycle equal to the temporal cycle of revolution of the machine reel can be extracted from the estimated or measured torque that is preferably used in an inner control loop the speed regulation of the braking generator 104.
The torque directed to the machine reel 101 can be estimated, for example, using values of electrical currents and voltages supplied to the braking generator 104. At least in principle, it is also possible to provide a shaft 106 between the braking generator and the machine reel with a strain gauge and with slip rings for taking out a signal representative of the torque. In the exemplifying case shown in figure 1 , the torque is estimated from the values of the electrical currents and voltages supplied to the braking generator with the device 102 that is a part of the control unit 108. As evident from above, this is, however, not the only possible implementation.
The braking generator 104 can be, for example, an alternating current machine such as an induction machine or a permanent magnet machine, and the unwinding station may comprise a frequency converter for controlling the braking generator. The control unit 108, the device 102 for monitoring torque, and the processing equipment 103 are, preferably but not necessarily, implemented with processing and sensor circuitries of the frequency converter. In conjunction with older unwind- ing-winding systems, the braking generator 104 can be a direct current commutator machine controlled with rectifying bridges.
In an unwinding station according to an embodiment of the invention, the processing equipment 103 is arranged to control a rotational speed and/or an angular acceleration of the machine reel on the basis of the quantity indicative of the eccen- tricity of the machine reel in order to limit the rotational speed and/or the angular acceleration when vibrations caused by the eccentricity would otherwise, i.e. without limiting the rotational speed and/or the angular acceleration, cause a fibre web break and/or other damages. In cases, where the electrical motor 1 14 of the winding station is driven in the speed controlled mode and the braking generator 104 of the unwinding station is driven in the torque controlled mode, a signal for controlling the rotational speed and/or the angular acceleration is supplied to the control unit 1 12 of the winding station. In other cases, wherein the electrical motor 1 14 of the winding station is driven in the torque controlled mode and the braking generator 104 of the unwinding station is driven in the speed controlled mode, the control- ling of the rotational speed and/or the angular acceleration can be carried out locally in the unwinding station.
The above-described principle for obtaining the quantity indicative of the eccentricity of the machine reel can be applied also off-line with respect to an unwinding- winding process. The quantity indicative of the eccentricity can be obtained basi- cally at any site where the machine reel can be rotated and the instantaneous torque acting on the machine reel can be monitored. Afterwards, the quantity in- dicative of the eccentricity can be used for controlling an unwinding-winding process or some other process related to the machine reel. Figure 2 shows a schematic illustration of a system according to an embodiment of the invention for determining eccentricity of a machine reel 201 . The system comprises a device 202 for monitoring torque acting on the machine reel and producing a torque signal representative of the torque as a function of time. The system comprises processing equipment 203 for determining, from the torque signal, a quantity proportional to the amplitude of an alternating torque component having a temporal cycle equal to a temporal cycle of revolution of the machine reel. The determined quantity is indicative of the eccentricity of the machine reel.
In a system according to an embodiment of the invention, the processing equipment 203 is arranged to multiply the torque signal with a sinusoidal signal having a temporal cycle equal to the temporal cycle of revolution of the machine reel and to low-pass filter the result of the multiplication. The result of the low-pass filtering is the above-mentioned quantity indicative of the eccentricity of the machine reel.
In a system according to another embodiment of the invention, the processing equipment 203 is arranged to band-pass filter the torque signal so that a center frequency of the band-pass filtering corresponds to the temporal cycle of revolution of the machine reel. The amplitude of the result of the band-pass filtering is the above-mentioned quantity indicative of the eccentricity of the machine reel.
In a system according to an embodiment of the invention, the device 202 for monitoring the torque is arranged to monitor the torque from a braking generator of an unwinding station for unwinding a fibre web from the machine reel. In this case, the system can be a part of the unwinding station as illustrated in figure 1 The processing equipment can be further arranged to control a rotational speed and/or an angular acceleration of the machine reel on the basis of the quantity indicative of the eccentricity of the machine reel. In this case, the system is not only a system for determining the eccentricity but a system for controlling the rotation of the machine reel. Figure 3 shows a flow chart of a method according to an embodiment of the invention for determining eccentricity of a rotating machine reel. The method comprises: - monitoring, in a phase 301 , torque acting on the machine reel,
- producing, in a phase 302, a torque signal representative of the torque as a function of time, and
- determining, in a phase 303, from the torque signal, a quantity proportional to an amplitude of an alternating torque component having a temporal cycle equal to a temporal cycle of revolution of the machine reel, wherein the determined quantity is indicative of the eccentricity of the machine reel.
In a method according to an embodiment of the invention, the determining of the quantity indicative of the eccentricity of the machine reel comprises multiplying the torque signal with a sinusoidal signal having a temporal cycle equal to the temporal cycle of revolution of the machine reel and low-pass filtering the result of the multiplication, wherein the result of the low-pass filtering is the quantity indicative of the eccentricity of the machine reel. In a method according to another embodiment of the invention, the determining of the quantity indicative of the eccentricity of the machine reel comprises band-pass filtering the torque signal with a band-pass filter having a center frequency corresponding to the temporal cycle of revolution of the machine reel, wherein the amplitude of the result of the band-pass filtering is the quantity indicative of the ec- centricity of the machine reel.
In a method according to an embodiment of the invention, the torque is monitored from a braking generator of an unwinding station when a fibre web is being unwound from the machine reel. The method may further comprise controlling a rotational speed and/or an angular acceleration of the machine reel on the basis of the quantity indicative of the eccentricity of the machine reel. In this case, the method is not only a method for determining the eccentricity but a method for controlling the rotation of the machine reel.
In a method according to another embodiment of the invention, the quantity indicative of the eccentricity of the machine reel is determined prior to an unwinding- winding process, and the quantity indicative of the eccentricity is later used for controlling the unwinding-winding process.
The specific examples provided in the description given above should not be construed as limiting. Therefore, the invention is not limited merely to the embodi- ments described above, many variants being possible.

Claims

What is claimed is:
1 . A method for determining eccentricity of a rotating machine reel, the method comprising monitoring (301 ) torque acting on the machine reel and producing (302) a torque signal representative of the torque as a function of time, character- ized in that the method further comprises determining (303), from the torque signal, a quantity proportional to an amplitude of an alternating torque component having a temporal cycle equal to a temporal cycle of revolution of the machine reel, wherein the determined quantity is indicative of the eccentricity of the machine reel.
2. A method according to claim 1 , wherein the determining of the quantity comprises multiplying the torque signal with a sinusoidal signal having a temporal cycle equal to the temporal cycle of revolution of the machine reel and low-pass filtering the result of the multiplication, the result of the low-pass filtering being the quantity indicative of the eccentricity of the machine reel.
3. A method according to claim 1 , wherein the determining of the quantity comprises band-pass filtering the torque signal with a band-pass filter having a center frequency corresponding to the temporal cycle of revolution of the machine reel, an amplitude of the result of the band-pass filtering being the quantity indicative of the eccentricity of the machine reel.
4. A method according to any of claims 1 -3, wherein the torque is monitored from a braking generator of an unwinding station when a fibre web is being unwound from the machine reel.
5. A method according to claim 4, wherein the method further comprises controlling a rotational speed of the machine reel on the basis of the quantity indicative of the eccentricity of the machine reel.
6. A method according to claims 4 or 5, wherein the method further comprises controlling an angular acceleration of the machine reel on the basis of the quantity indicative of the eccentricity of the machine reel.
7. A system for determining eccentricity of a machine reel (201 ), the system comprising a device (202) for monitoring torque acting on the machine reel and producing a torque signal representative of the torque as a function of time, characterized in that the system further comprises processing equipment (203) for de- termining, from the torque signal, a quantity proportional to an amplitude of an alternating torque component having a temporal cycle equal to a temporal cycle of revolution of the machine reel, wherein the determined quantity is indicative of the eccentricity of the machine reel.
8. A system according to claim 7, wherein the processing equipment is arranged to multiply the torque signal with a sinusoidal signal having a temporal cycle equal to the temporal cycle of revolution of the machine reel and to low-pass filter the result of the multiplication, the result of the low-pass filtering being the quantity indicative of the eccentricity of the machine reel.
9. A system according to claim 7, wherein the processing equipment is arranged to band-pass filter the torque signal so that a center frequency of the band-pass filtering corresponds to the temporal cycle of revolution of the machine reel, an amplitude of the result of the band-pass filtering being the quantity indicative of the eccentricity of the machine reel.
10. A system according to any of claims 7-9, wherein the device for monitoring the torque is arranged to monitor the torque from a braking generator of an unwinding station for unwinding a fibre web from the machine reel.
1 1 . A system according to claim 10, wherein the processing equipment is arranged to control a rotational speed of the machine reel on the basis of the quantity indicative of the eccentricity of the machine reel.
12. A system according to claim 10 or 1 1 , wherein the processing equipment is arranged to control an angular acceleration of the machine reel on the basis of the quantity indicative of the eccentricity of the machine reel.
13. An unwinding station (100) comprising:
- a braking generator (104) for maintaining tension of a fibre web to be unwound from a machine reel (101 ), and
- a device (102) for monitoring torque of the braking generator and producing a torque signal representative of the torque as a function of time, characterized in that the unwinding station further comprises processing equipment (103) for determining, from the torque signal, a quantity proportional to an amplitude of an alternating torque component having a temporal cycle equal to a temporal cycle of revolution of the machine reel, wherein the determined quantity is indicative of the eccentricity of the machine reel.
14. An unwinding station according to claim 13, wherein the processing equipment is arranged to control a rotational speed of the machine reel on the basis of the quantity indicative of the eccentricity of the machine reel.
15. An unwinding station according to claim 13 or 14, wherein the processing equipment is arranged to control an angular acceleration of the machine reel on the basis of the quantity indicative of the eccentricity of the machine reel.
PCT/FI2010/050557 2010-06-29 2010-06-29 A method and a system for determining eccentricity WO2012001211A1 (en)

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EP2837589A1 (en) * 2013-08-16 2015-02-18 KÜHNE + VOGEL Prozessautomatisierung Antriebstechnik GmbH System with a brake generator
IT201800009236A1 (en) * 2018-10-08 2020-04-08 A Celli Paper Spa REWINDING MACHINE AND METHOD FOR CHECKING THE SPEED OF MOTORS IN A REWINDING MACHINE

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JPS63267650A (en) 1987-04-27 1988-11-04 Mitsubishi Heavy Ind Ltd Web winder
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EP2837589A1 (en) * 2013-08-16 2015-02-18 KÜHNE + VOGEL Prozessautomatisierung Antriebstechnik GmbH System with a brake generator
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IT201800009236A1 (en) * 2018-10-08 2020-04-08 A Celli Paper Spa REWINDING MACHINE AND METHOD FOR CHECKING THE SPEED OF MOTORS IN A REWINDING MACHINE
WO2020075018A1 (en) * 2018-10-08 2020-04-16 A.Celli Paper S.P.A. Rewinding machine and method for controlling the speed of the motors in a rewinding machine
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