CA1326521C - Eccentricity compensator for rolling mill - Google Patents
Eccentricity compensator for rolling millInfo
- Publication number
- CA1326521C CA1326521C CA000569058A CA569058A CA1326521C CA 1326521 C CA1326521 C CA 1326521C CA 000569058 A CA000569058 A CA 000569058A CA 569058 A CA569058 A CA 569058A CA 1326521 C CA1326521 C CA 1326521C
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- CA
- Canada
- Prior art keywords
- signal
- eccentricity
- phase
- force
- frequency
- Prior art date
- Legal status (The legal status 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 status listed.)
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
- B21B37/58—Roll-force control; Roll-gap control
- B21B37/66—Roll eccentricity compensation systems
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Control Of Metal Rolling (AREA)
Abstract
ECCENTRICITY COMPENSATOR FOR ROLLING MILL
ABSTRACT OF THE DISCLOSURE
There is described an eccentricity compensating apparatus for determining and compensating for the eccentricity error introduced into a material by operative rolls in a rolling mill. The apparatus separates the roll eccentricity error from the force input signal which signal is used to control the thickness of the material being rolled. The apparatus uses the roll eccentricity signal to control the roll position and thereby remove the roll eccentricity error signal from the force input signal. Once the roll eccentricity signal component is removed from the force input signal the apparatus continues to generate a roll eccentricity signal that continues to compensate for roll eccentricity. The apparatus employs an oscillator whose frequency and phase are controlled to lock the oscillator onto the frequency of the eccentricity signal. The apparatus also compensates for the amplitude of the eccentricity error.
ABSTRACT OF THE DISCLOSURE
There is described an eccentricity compensating apparatus for determining and compensating for the eccentricity error introduced into a material by operative rolls in a rolling mill. The apparatus separates the roll eccentricity error from the force input signal which signal is used to control the thickness of the material being rolled. The apparatus uses the roll eccentricity signal to control the roll position and thereby remove the roll eccentricity error signal from the force input signal. Once the roll eccentricity signal component is removed from the force input signal the apparatus continues to generate a roll eccentricity signal that continues to compensate for roll eccentricity. The apparatus employs an oscillator whose frequency and phase are controlled to lock the oscillator onto the frequency of the eccentricity signal. The apparatus also compensates for the amplitude of the eccentricity error.
Description
1 32~52 1 Case 2983 ECCENTRICITY COMPENSATOR FOR ROLL:[NG MILL
ield Of The_I vention.
The present invention relates to the operation o~ a rolling mill and in particular relates to an apparatus that compensates for the eccentricity of the rolls used in the rolling mill.
Back~round of the In ention.
In a rolling mill it is common that the material passing between opposed rolls in the mill may vary in thickness along its length. Usually some ~orm o~ gauge control system is employed to make corrections in the thickness of the material passing through the mill. One gauge control system commonly used is ~he BISRA system (British Iron and Steel Research Association). In this system, during mill operation, the spacing between the rolls is equal ts the initial spacing between them whe~ unloaded plus an amount proportional to the separating force between thP rolls due to the material as it passes between the rolls. In this method, electrical signals representing the amount of separation between the rolls and the separating force are compared to generate an error signal which signal is used to control the thickness of the ; material.
While this method is effective for ,; ' . - ' ''~ :~ "' ' ;
13265~ t Case 2983 controlling the thickness of the material in response to variations in the thickness of the material entering between the rolls, the method is not designed to compensate for errors introduced in the thickness of the material due to roll eccentricity. The eccentricity of the rolls makes the sepaxating force signal undergo changes or variations without corresponding changes in the initial rol:L separation distance signal. The severity of the error introduced is dependent upon the magnitude of the eccentricity of the roll. The eccentricity error introduced may cause the gauge control system to alter the separating force signal without altering the separation setting between the rolls. As a consequence, the gauge control system may cause the separation force of the rolls to decrease ~or increase~ without an accompanying change in the separation distance between the rolls. This causes the control system to take the wrong corrective action introducing further error into the thickness of the material passing through the mill. Clearly, there is a need to remove the roll eccentricity signal component from the signal representing the thickness of the roll.
Ob~ects of the Present Inventio_.
It is an object of the present invention to provide an eccentricity compensating apparatus that determines and compensates for the eccentricity error introduced into a material by the operative rolls of a rolling mill.
It is another object of the present invention to provide an eccentricity compensating apparatus that compensates for roll eccentricity in a mill so as to allow the gauge thickness control to more accurately control the thickness of the material being worked in the mill~
Summary of the Invention.
In accordance with one aspect of the present , ~
, :, .. .
,:
1 32652~ case 2983 invention there is provided an eccentricity compensaking apparatus for determining and compensating for the eccentricity error introduced into a material by operative rolls in a rolling mill. The apparatus includes sensing means for generating a force signal.
The force signal represents the thicknes~; of the material passing through the rolls and includes a roll eccentricity signal component prior to the apparatus compensating for roll eccentricity error. The apparatus includes an oscillator which is capable of producing a first reference siynal whose frequency and phase correspond to the frequency and phase of the roll eccentricity signal present in the force signal and whose frequency and phase are stable and constant once the roll eccentricity signal component is removed from the force signal. The apparatus includes first signal modifying means for modifying the force signal with the first reference signal to derive an amplitude signal which is proportional to the roll eccentricity signal component when the component is present in the force signal and which is constant when the eccentricity signal component is not present in the force signal. A
second signal modifying means is provided for modifying the amplitude signal with the first reference signal to produce an error eccentricity signal. A roll positioning means is responsive to the error eccentricity signal for adjusting roll position to compensate for the roll eccentricity error thereby removing the eccentricity signal component from the force signal.
By employing an oscillator that generates a reference signal of the same frequency and phase as the eccen~ricity signal, the eccentricity compensator effectiYely tracks and locks onto the roll eccentricity. As the compensator locks onto the frequency and phase of the eccentricity signal ~ ^ :
., ,. ,, ,.' ' ~
- Case 2983 component, the compensator generate an error eccentricity signal that is used to adjust the roll separation to remove the effect of the roll eccentricity from the material being wor]ked. This results in the sensing means sensing a force signal that no longer has an eccentricity signal component.
It should be understood that the force signal may still have a very small eccentricity component but this error ~ill lie within acceptable tolerances. When there is no eccentricity signal component present in the force signal, the compensator is capable o~ generating constants so that an error eccentricity signal is still provided at the output of the compensator to control the roll separation.
In accordance with an additional aspect of the present invention the oscillator in response to the force signal is capable of producing a second reference signal whose frequency and phase correspond to the frequency and phase of the eccentricity signal when present in the force signal and whose frequency and phase are stable and constant once the roll eccentricity signal component is removed from the force signal. The compensator apparatus further including third signal modifying means for modifying the force signal with the second reference signal to produce at least one oscillator control reference signal for controlling one of the phase and frequency of the oscillator.
Brief Description of the Drawin~s For a better understanding o~ the nature and objects of the present invention reference may be had by way of example to the accompanying diagrammatic drawings in which:
Figure 1 is a schematic block diagram of tha eccentricity compensator of the present invention; and, Figure 2 is a more detailed block diagram of , ~ 3~5~t - Case 2983 the eccentricity compensator illustrated in figure 1.
Detailed Description of the Prasent~Invention.
Referring to figure 1 there is shown generally at 10 an apparatus for determining and compensating for roll eccentricity. It should be understood that this apparatus may comprise standard type of sensors used in roll milling applications and that the boxes of Figure 1 are illustrative of the functions that the compensating apparatus will perform. In particular most of the functions performed may be performed in a computer or electronic circuitry designed for this application.
A force signal is fed into the input 12 of force sensor 14. The force signal sensed by sensor 12 is passed through a high pass ~ilter (not shown) so as to eliminate DC offsets in the eccentricity compensating apparatus. The force signal is the measured stand force which comprises initially two components. The first component is the force due to the thickness of the material passing between th~ rolls of the mill. The second component of the signal is the force due primarily to the roll eccentricity. The roll eccentricity signal is generally a sinusoidal signal resulting from errors in centering the top and bottom ~-back up rolls of each stand. The sum of the two roll eccentricities may have a beat since the amplitude and the frequency of each roll may be different. It is the purpose of the eccentricity compensating apparatus to separate the roll eccentricity error ~rom the errors in strip thickness. Once this is accomplished the errors in strip thickness can be compensated for by the gauge control system of the rolling mill. It should also be understood that more than one eccentricity compensating apparatus may be needed in a mill. In particular a compensator may be needed at all stations in the mill where the material passes between opposing rolls of the !; ' '~
.
- ,: . `,, , ' ' , :
.': ' : .
t ~ t Case 2983 mill. The use of multiple filters in the mill system allows for the removal of multiple harmonics due to differences in the size of the back up rolls. One compensator may be reguired for each rol~L in that the rolls may not be symmetricalO
The eccentricity apparatus further includes a ~irst signal modi~ier 16, a second signa]L modifier 18, a roll positioner 20, a third signal modifier 22 and an oscillator 24.
In operation, the force signal at input 12 of sensor 14 initially includes a signal component that represents the roll eccentricity. This force signal is passed to the first signal modifying means or modifier 16 and the third signal modifying means or modifier 22.
The third signal modifier 22 modifies the force signal with a feedback or reference signal from the oscillator 24 to produce an oscillator control signal that controls the frequency and the phase of the oscillator. This control signal is used to set the frequency and phase of the oscillator to that of the eccentricity signal component con~ained in the force signal. The oscillator 24 also generates a first reference signal which it sends to first and second signal modifiers 16, 18.
Signal modifier 16 modifies the force signal with the first reference signal to produce an amplitude signal proportional to the amplitude of the roll eccentricity signal component contained in the force signal. The second signal modifier 18 modifies the proportional amplitude signal with the first reference signal from oscillator 24 to generate a signal that i5 proportional to the roll eccentricity errorO This error signal is fed to the roll position 20 which controls the position and separation between the rolls. The roll positioner moves the rolls in response , ~
: , :
.. , , ~ ~
,, .
: .. ;
1 32~ case 2983 to the proportional eccentricity signal which effectively removes the eccentricity component from the force signal being fed into the compensator.
In order for the compensator to continue to compensate for roll eccentricity after the eccentricity signal component has been removed form the force signal, the first signal modifier 16 and the third signal modifier 22 generate constants that allow the oscillator to provide a stable signal and the first modifier 16 to generate a constant amplitude signal.
As a result of tha constant and stable signal, the second signal modifier will continue to generate an error eccentricity signal as the compensator remains locked onto the frequency and phase of the eccentricity signal, Referring to Figure 2 a more detailed description of the operation of eccentricity compensating apparatus is presented. The signal entering at the upper left part of Figure 2 at 1~ is the high pass filtered force signal. This signal is the AC component of the BISRA force feedback. This ' '' signal can be treated as a sum of sinusoidal terms for the purpose of explaining the operation of the compensating apparatus lO. The force signal may then be given as:
F = A * sin~at + b), where A is the amplitude of the force signal, a is the radian frequency, b is the phase shift and t represents time.
The force signal F is fed to the inputs of multipliers 26 and 28. The other input 27 of multiplier 26 is fed a first reference signal from the sine output of oscillator 24 while the other input 29 of multiplier 28 is fed the second reference signal from,the cosine output of oscillator 24. The frequency and phase of the signals produced by oscillator 24 are :, ; , ,; : :. .
; , 1 326~ case 2983 dependent upon the input to the frequency input 30 and phase input 32 of the oscillator 24. The sine reference signal output of the oscillator may be represented as:
R1 = sin(ct+d), where c is the radian frequency of the oscillator, t represents time and d is the phase shift of the oscillator. Likewise, the cosine signal output of the oscillator may be represented by:
R2 = cos(ct+d), where c is the radian frequency of the oscillator, t represents time and d is the phase shift of the oscillator. '.
Referring back to the signal multiplier 26, this device multiplies the force signal F by the first oscillator reference signal Rl. This gives the following equation:
F * Rl = {A * sin~at + b~) * sin(ct+d) = A/2 * cos{(a-c)t + (b-d)}
- A/2 * cos((~+c)t + (b+d~}.
This multiplied signal is then passed through low pass filter which removes the sum frequencies of the multiplied signal leaving the following signal S:
S =A/2 * cos~(a-c)t + (b-d)~.
The amplitude cutoff frequency of the low pass filter is determined by controlling input 37 to filter 36. It should be understood that many of the operating properties of the compensator apparatus of the present invention are determined by the filter 36.
Decreasing the cutoff frequency of the filter 36 decreases the bandwidth of the compensator and increases the response time of the compensator. The shape of the filter has little effect on the response of the compensator and accordingly, a simple first order low pass filter is used.
The filtered signal is then fed to the ::
~ .
~ t Case 2983 _ g proportional plus integrator 38. The integrator converts the signal into an amplitude signal proportional to the amplitude of the eccentricity signal component contained in the force signal F. It should be understood that once the compensatsr locks onto the eccentricity signal, the terms a and c will be equal and the terms b and d will also be equal. ~s a result the output of the low pass filter 36 will be the A/2 * cos(Ot) which is equal to zero. Since the output of the low pass filter is zero, the integrator has no signal to integrate. As a result the proportional plus feature of the integrator produces a constant amplitude signal at its output. The gain of the integrator can be controlled as well as its lower and upper amplitude limits. The output of the integrator 38 i5 thus an amplitude signal that is representative of the amplitude of roll eccentricity. The integrator 38 provides an initial amplitude value based on calculated values from previous mill runs. The initialization of the integrator 38 is controlled through the input 39.
~his increases the response time of the compensator in locking onto roll eccentricity.
The output amplitude of the integrator 38 is then fed to the second modifier which is signal multiplier 18. The amplitude signal is multiplied with the sine output of the oscillator which represenks the frequency and phase of the eccentricity signal. The output error-signal fed to the roll positioner is in the form of ~ sin(at+c~ where ~ represents the amplitude of the roll eccentricity. The eccentricity signal is used to control the position of the rolls in the mill and, as the positions of the rolls are controlled in response to the eccentricity signal, the eccentricity signal component in the force signal is removed.
The frequency and phas~ of the oscillator , ~
j ',. ' .. ~ .' ~ . .' ". ' t 3~6~2t ~ - Case 2983 output signals are controlled by the third signal modifying means comprising multiplier 28, low pass filter 42 and proportional plus integrator 44 to provide a frequency control signal to the frequency input of the oscillator. The third signal modifying means or modifier also includes the multiplier 28, low pass filter ~2 and proportional plus integrator 46 to produce a phase control signal at the phase input of the oscillator.
The operation of this part of the compensator is similar to that of the multiplier 26, low pass filter 36 and integrator 38 described above. Briefly, however, force signal F is multiplied with the cosine output of the oscillator signal. This gives the following product signal:
F * R2 = (A * sin(at ~ b)~ * cos(ct+d) = A/2 * sin{ta-c)t + (b-d)}
- A/2 * sin{(a+c)t + (b+d)~.
The low pass filter filters out the upper freguency of the signal leaving A/2 * sin{(a-c)t +
(b-d)}. The gain of the frequency~phase cutoff of the filter is controlled at 43. The output of the filter is fed to integrators 44 and 46. Integrator 44 provides an amplitude signal at its output that controls the frequency of the oscillator at input 30.
A calculated or estimated center frequency for the eccentricity is fed to the oscillator input 30 through input 31 and the summing amplifier. The initial frequency signal is provided at input 31 during the operation of the rolling mill and eccentricity compensator. When the compensator is tracking the eccentricity of the rolls, the output of the low pass filter will be zero and the integrator will provide a constant in lieu of a signal. Integrator 46 provides an amplitude signal at its output that controls the phase of the oscillator. When the compensator is ,:
,
ield Of The_I vention.
The present invention relates to the operation o~ a rolling mill and in particular relates to an apparatus that compensates for the eccentricity of the rolls used in the rolling mill.
Back~round of the In ention.
In a rolling mill it is common that the material passing between opposed rolls in the mill may vary in thickness along its length. Usually some ~orm o~ gauge control system is employed to make corrections in the thickness of the material passing through the mill. One gauge control system commonly used is ~he BISRA system (British Iron and Steel Research Association). In this system, during mill operation, the spacing between the rolls is equal ts the initial spacing between them whe~ unloaded plus an amount proportional to the separating force between thP rolls due to the material as it passes between the rolls. In this method, electrical signals representing the amount of separation between the rolls and the separating force are compared to generate an error signal which signal is used to control the thickness of the ; material.
While this method is effective for ,; ' . - ' ''~ :~ "' ' ;
13265~ t Case 2983 controlling the thickness of the material in response to variations in the thickness of the material entering between the rolls, the method is not designed to compensate for errors introduced in the thickness of the material due to roll eccentricity. The eccentricity of the rolls makes the sepaxating force signal undergo changes or variations without corresponding changes in the initial rol:L separation distance signal. The severity of the error introduced is dependent upon the magnitude of the eccentricity of the roll. The eccentricity error introduced may cause the gauge control system to alter the separating force signal without altering the separation setting between the rolls. As a consequence, the gauge control system may cause the separation force of the rolls to decrease ~or increase~ without an accompanying change in the separation distance between the rolls. This causes the control system to take the wrong corrective action introducing further error into the thickness of the material passing through the mill. Clearly, there is a need to remove the roll eccentricity signal component from the signal representing the thickness of the roll.
Ob~ects of the Present Inventio_.
It is an object of the present invention to provide an eccentricity compensating apparatus that determines and compensates for the eccentricity error introduced into a material by the operative rolls of a rolling mill.
It is another object of the present invention to provide an eccentricity compensating apparatus that compensates for roll eccentricity in a mill so as to allow the gauge thickness control to more accurately control the thickness of the material being worked in the mill~
Summary of the Invention.
In accordance with one aspect of the present , ~
, :, .. .
,:
1 32652~ case 2983 invention there is provided an eccentricity compensaking apparatus for determining and compensating for the eccentricity error introduced into a material by operative rolls in a rolling mill. The apparatus includes sensing means for generating a force signal.
The force signal represents the thicknes~; of the material passing through the rolls and includes a roll eccentricity signal component prior to the apparatus compensating for roll eccentricity error. The apparatus includes an oscillator which is capable of producing a first reference siynal whose frequency and phase correspond to the frequency and phase of the roll eccentricity signal present in the force signal and whose frequency and phase are stable and constant once the roll eccentricity signal component is removed from the force signal. The apparatus includes first signal modifying means for modifying the force signal with the first reference signal to derive an amplitude signal which is proportional to the roll eccentricity signal component when the component is present in the force signal and which is constant when the eccentricity signal component is not present in the force signal. A
second signal modifying means is provided for modifying the amplitude signal with the first reference signal to produce an error eccentricity signal. A roll positioning means is responsive to the error eccentricity signal for adjusting roll position to compensate for the roll eccentricity error thereby removing the eccentricity signal component from the force signal.
By employing an oscillator that generates a reference signal of the same frequency and phase as the eccen~ricity signal, the eccentricity compensator effectiYely tracks and locks onto the roll eccentricity. As the compensator locks onto the frequency and phase of the eccentricity signal ~ ^ :
., ,. ,, ,.' ' ~
- Case 2983 component, the compensator generate an error eccentricity signal that is used to adjust the roll separation to remove the effect of the roll eccentricity from the material being wor]ked. This results in the sensing means sensing a force signal that no longer has an eccentricity signal component.
It should be understood that the force signal may still have a very small eccentricity component but this error ~ill lie within acceptable tolerances. When there is no eccentricity signal component present in the force signal, the compensator is capable o~ generating constants so that an error eccentricity signal is still provided at the output of the compensator to control the roll separation.
In accordance with an additional aspect of the present invention the oscillator in response to the force signal is capable of producing a second reference signal whose frequency and phase correspond to the frequency and phase of the eccentricity signal when present in the force signal and whose frequency and phase are stable and constant once the roll eccentricity signal component is removed from the force signal. The compensator apparatus further including third signal modifying means for modifying the force signal with the second reference signal to produce at least one oscillator control reference signal for controlling one of the phase and frequency of the oscillator.
Brief Description of the Drawin~s For a better understanding o~ the nature and objects of the present invention reference may be had by way of example to the accompanying diagrammatic drawings in which:
Figure 1 is a schematic block diagram of tha eccentricity compensator of the present invention; and, Figure 2 is a more detailed block diagram of , ~ 3~5~t - Case 2983 the eccentricity compensator illustrated in figure 1.
Detailed Description of the Prasent~Invention.
Referring to figure 1 there is shown generally at 10 an apparatus for determining and compensating for roll eccentricity. It should be understood that this apparatus may comprise standard type of sensors used in roll milling applications and that the boxes of Figure 1 are illustrative of the functions that the compensating apparatus will perform. In particular most of the functions performed may be performed in a computer or electronic circuitry designed for this application.
A force signal is fed into the input 12 of force sensor 14. The force signal sensed by sensor 12 is passed through a high pass ~ilter (not shown) so as to eliminate DC offsets in the eccentricity compensating apparatus. The force signal is the measured stand force which comprises initially two components. The first component is the force due to the thickness of the material passing between th~ rolls of the mill. The second component of the signal is the force due primarily to the roll eccentricity. The roll eccentricity signal is generally a sinusoidal signal resulting from errors in centering the top and bottom ~-back up rolls of each stand. The sum of the two roll eccentricities may have a beat since the amplitude and the frequency of each roll may be different. It is the purpose of the eccentricity compensating apparatus to separate the roll eccentricity error ~rom the errors in strip thickness. Once this is accomplished the errors in strip thickness can be compensated for by the gauge control system of the rolling mill. It should also be understood that more than one eccentricity compensating apparatus may be needed in a mill. In particular a compensator may be needed at all stations in the mill where the material passes between opposing rolls of the !; ' '~
.
- ,: . `,, , ' ' , :
.': ' : .
t ~ t Case 2983 mill. The use of multiple filters in the mill system allows for the removal of multiple harmonics due to differences in the size of the back up rolls. One compensator may be reguired for each rol~L in that the rolls may not be symmetricalO
The eccentricity apparatus further includes a ~irst signal modi~ier 16, a second signa]L modifier 18, a roll positioner 20, a third signal modifier 22 and an oscillator 24.
In operation, the force signal at input 12 of sensor 14 initially includes a signal component that represents the roll eccentricity. This force signal is passed to the first signal modifying means or modifier 16 and the third signal modifying means or modifier 22.
The third signal modifier 22 modifies the force signal with a feedback or reference signal from the oscillator 24 to produce an oscillator control signal that controls the frequency and the phase of the oscillator. This control signal is used to set the frequency and phase of the oscillator to that of the eccentricity signal component con~ained in the force signal. The oscillator 24 also generates a first reference signal which it sends to first and second signal modifiers 16, 18.
Signal modifier 16 modifies the force signal with the first reference signal to produce an amplitude signal proportional to the amplitude of the roll eccentricity signal component contained in the force signal. The second signal modifier 18 modifies the proportional amplitude signal with the first reference signal from oscillator 24 to generate a signal that i5 proportional to the roll eccentricity errorO This error signal is fed to the roll position 20 which controls the position and separation between the rolls. The roll positioner moves the rolls in response , ~
: , :
.. , , ~ ~
,, .
: .. ;
1 32~ case 2983 to the proportional eccentricity signal which effectively removes the eccentricity component from the force signal being fed into the compensator.
In order for the compensator to continue to compensate for roll eccentricity after the eccentricity signal component has been removed form the force signal, the first signal modifier 16 and the third signal modifier 22 generate constants that allow the oscillator to provide a stable signal and the first modifier 16 to generate a constant amplitude signal.
As a result of tha constant and stable signal, the second signal modifier will continue to generate an error eccentricity signal as the compensator remains locked onto the frequency and phase of the eccentricity signal, Referring to Figure 2 a more detailed description of the operation of eccentricity compensating apparatus is presented. The signal entering at the upper left part of Figure 2 at 1~ is the high pass filtered force signal. This signal is the AC component of the BISRA force feedback. This ' '' signal can be treated as a sum of sinusoidal terms for the purpose of explaining the operation of the compensating apparatus lO. The force signal may then be given as:
F = A * sin~at + b), where A is the amplitude of the force signal, a is the radian frequency, b is the phase shift and t represents time.
The force signal F is fed to the inputs of multipliers 26 and 28. The other input 27 of multiplier 26 is fed a first reference signal from the sine output of oscillator 24 while the other input 29 of multiplier 28 is fed the second reference signal from,the cosine output of oscillator 24. The frequency and phase of the signals produced by oscillator 24 are :, ; , ,; : :. .
; , 1 326~ case 2983 dependent upon the input to the frequency input 30 and phase input 32 of the oscillator 24. The sine reference signal output of the oscillator may be represented as:
R1 = sin(ct+d), where c is the radian frequency of the oscillator, t represents time and d is the phase shift of the oscillator. Likewise, the cosine signal output of the oscillator may be represented by:
R2 = cos(ct+d), where c is the radian frequency of the oscillator, t represents time and d is the phase shift of the oscillator. '.
Referring back to the signal multiplier 26, this device multiplies the force signal F by the first oscillator reference signal Rl. This gives the following equation:
F * Rl = {A * sin~at + b~) * sin(ct+d) = A/2 * cos{(a-c)t + (b-d)}
- A/2 * cos((~+c)t + (b+d~}.
This multiplied signal is then passed through low pass filter which removes the sum frequencies of the multiplied signal leaving the following signal S:
S =A/2 * cos~(a-c)t + (b-d)~.
The amplitude cutoff frequency of the low pass filter is determined by controlling input 37 to filter 36. It should be understood that many of the operating properties of the compensator apparatus of the present invention are determined by the filter 36.
Decreasing the cutoff frequency of the filter 36 decreases the bandwidth of the compensator and increases the response time of the compensator. The shape of the filter has little effect on the response of the compensator and accordingly, a simple first order low pass filter is used.
The filtered signal is then fed to the ::
~ .
~ t Case 2983 _ g proportional plus integrator 38. The integrator converts the signal into an amplitude signal proportional to the amplitude of the eccentricity signal component contained in the force signal F. It should be understood that once the compensatsr locks onto the eccentricity signal, the terms a and c will be equal and the terms b and d will also be equal. ~s a result the output of the low pass filter 36 will be the A/2 * cos(Ot) which is equal to zero. Since the output of the low pass filter is zero, the integrator has no signal to integrate. As a result the proportional plus feature of the integrator produces a constant amplitude signal at its output. The gain of the integrator can be controlled as well as its lower and upper amplitude limits. The output of the integrator 38 i5 thus an amplitude signal that is representative of the amplitude of roll eccentricity. The integrator 38 provides an initial amplitude value based on calculated values from previous mill runs. The initialization of the integrator 38 is controlled through the input 39.
~his increases the response time of the compensator in locking onto roll eccentricity.
The output amplitude of the integrator 38 is then fed to the second modifier which is signal multiplier 18. The amplitude signal is multiplied with the sine output of the oscillator which represenks the frequency and phase of the eccentricity signal. The output error-signal fed to the roll positioner is in the form of ~ sin(at+c~ where ~ represents the amplitude of the roll eccentricity. The eccentricity signal is used to control the position of the rolls in the mill and, as the positions of the rolls are controlled in response to the eccentricity signal, the eccentricity signal component in the force signal is removed.
The frequency and phas~ of the oscillator , ~
j ',. ' .. ~ .' ~ . .' ". ' t 3~6~2t ~ - Case 2983 output signals are controlled by the third signal modifying means comprising multiplier 28, low pass filter 42 and proportional plus integrator 44 to provide a frequency control signal to the frequency input of the oscillator. The third signal modifying means or modifier also includes the multiplier 28, low pass filter ~2 and proportional plus integrator 46 to produce a phase control signal at the phase input of the oscillator.
The operation of this part of the compensator is similar to that of the multiplier 26, low pass filter 36 and integrator 38 described above. Briefly, however, force signal F is multiplied with the cosine output of the oscillator signal. This gives the following product signal:
F * R2 = (A * sin(at ~ b)~ * cos(ct+d) = A/2 * sin{ta-c)t + (b-d)}
- A/2 * sin{(a+c)t + (b+d)~.
The low pass filter filters out the upper freguency of the signal leaving A/2 * sin{(a-c)t +
(b-d)}. The gain of the frequency~phase cutoff of the filter is controlled at 43. The output of the filter is fed to integrators 44 and 46. Integrator 44 provides an amplitude signal at its output that controls the frequency of the oscillator at input 30.
A calculated or estimated center frequency for the eccentricity is fed to the oscillator input 30 through input 31 and the summing amplifier. The initial frequency signal is provided at input 31 during the operation of the rolling mill and eccentricity compensator. When the compensator is tracking the eccentricity of the rolls, the output of the low pass filter will be zero and the integrator will provide a constant in lieu of a signal. Integrator 46 provides an amplitude signal at its output that controls the phase of the oscillator. When the compensator is ,:
,
Claims (10)
1. An eccentricity compensating apparatus for determining and compensating for the eccentricity error introduced into a material by operative rolls in a rolling mill, comprising:
sensing means for generating a force signal, the force signal representing the thickness of the material passing through the rolls, the force signal including a roll eccentricity signal component prior to the apparatus compensating for roll eccentricity error;
an oscillator responsive to the force signal for producing a first reference signal whose frequency and phase correspond to the frequency and phase of the roll eccentricity signal component when present in the force signal and whose frequency and phase are stable and constant once the roll eccentricity signal component is removed from the force signal;
first signal modifying means for modifying the force signal with the first reference signal to derive an amplitude signal which is proportional to the amplitude of the roll eccentricity signal component when present in the force signal and which is constant when the roll eccentricity signal component is removed from the force signal;
second signal modifying means for modifying the amplitude signal with the first reference signal to produce an error eccentricity signal;
roll positioning means for adjusting roll position in accordance with the error eccentricity signal to compensate for the roll eccentricity error thereby removing the eccentricity signal component from the force signal.
sensing means for generating a force signal, the force signal representing the thickness of the material passing through the rolls, the force signal including a roll eccentricity signal component prior to the apparatus compensating for roll eccentricity error;
an oscillator responsive to the force signal for producing a first reference signal whose frequency and phase correspond to the frequency and phase of the roll eccentricity signal component when present in the force signal and whose frequency and phase are stable and constant once the roll eccentricity signal component is removed from the force signal;
first signal modifying means for modifying the force signal with the first reference signal to derive an amplitude signal which is proportional to the amplitude of the roll eccentricity signal component when present in the force signal and which is constant when the roll eccentricity signal component is removed from the force signal;
second signal modifying means for modifying the amplitude signal with the first reference signal to produce an error eccentricity signal;
roll positioning means for adjusting roll position in accordance with the error eccentricity signal to compensate for the roll eccentricity error thereby removing the eccentricity signal component from the force signal.
2. The compensator apparatus of claim 1 wherein the oscillator, responsive to the force signal, tracking the eccentricity of the rolls, the output of the low pass filter will be zero and the integrator 46 will provide a constant to the phase input 32 in lieu of a signal. In this manner the frequency and phase of the oscillator will track the frequency and phase of the eccentricity of the rolls. The integrators 44 and 46 each provide an initial amplitude value based on calculated values from previous mill runs. The initialization of the integrators 44 and 46 is controlled through respective inputs 45 and 47. This increases the response time of the compensator in locking onto roll eccentricity.
produces a second reference signal whose frequency and phase correspond to the frequency and phase of the eccentricity signal component when present in the force signal and whose frequency and phase remains constant and stable once the roll eccentricity signal component is removed from the force signal, the compensator apparatus further including third signal modifying means for modifying the force signal with the second reference signal to produce at least one oscillator control reference signal for controlling one of the phase and frequency of the oscillator.
produces a second reference signal whose frequency and phase correspond to the frequency and phase of the eccentricity signal component when present in the force signal and whose frequency and phase remains constant and stable once the roll eccentricity signal component is removed from the force signal, the compensator apparatus further including third signal modifying means for modifying the force signal with the second reference signal to produce at least one oscillator control reference signal for controlling one of the phase and frequency of the oscillator.
3. The compensator apparatus of claim 2 wherein the third signal modifying means produces two oscillator control reference signals, one indicative of the phase of the roll eccentricity and the other indicative of the frequency of the roll eccentricity.
4. The compensator apparatus of claim 1 wherein the first signal modifying means includes a multiplier for multiplying the force signal by the first reference signal to provide a product signal having upper and lower frequency components, a low pass filter to eliminate the upper frequency component of the product signal and the lower frequency product signal being zero when the roll eccentricity signal component is removed from the force signal, and an integrator to produce the amplitude signal from the filtered output.
5. The compensator apparatus of claim 4 wherein the second signal modifying means includes a multiplier for multiplying the amplitude signal by the first reference signal to produce the error eccentricity signal.
6. The compensator apparatus of claim 2 wherein the first signal modifying means includes a multiplier for multiplying the force signal by the first reference signal to provide a product signal having upper and lower frequency components, a low pass filter to eliminate the upper frequency component of the product signal and the lower frequency product signal being zero when the roll eccentricity signal component is removed from the force signal, and an integrator to produce the amplitude signal from the filtered output.
7. The compensator apparatus of claim 6 wherein the second signal modifying means includes a multiplier for multiplying the amplitude signal by the first reference signal to produce the error eccentricity signal.
8. The compensator apparatus of claim 6 wherein the third signal modifying means includes a multiplier for multiplying the force signal by the second reference signal to provide a product signal having upper and lower frequency components, a low pass filter to eliminate the upper frequency component of the product signal, and an integrator to produce a frequency oscillator control reference signal representative of the frequency of the roll eccentricity from the lower frequency component of the product signal, the oscillator varying the center frequency of the first and second reference signals in response to changes in the frequency oscillator control reference signal, the output of the low pass signal being zero when the roll eccentricity signal component is removed form the force signal.
9. The compensator apparatus of claim 6 wherein the third signal modifying means includes a multiplier for multiplying the force signal by the second reference signal to provide a product signal having upper and lower frequency components, a low pass filter to eliminate the upper frequency component of the product signal, and an integrator to produce a phase oscillator control reference signal representative of the phase of the roll eccentricity from the lower frequency component of the product signal, the oscillator varying the phase of the first and second reference signals in response to changes in the phase oscillator control reference signal, the output of the low pass signal being zero when the roll eccentricity signal component is removed form the force signal.
10. The compensator apparatus of claim 8 wherein the third signal modifying means includes a multiplier for multiplying the force signal by the second reference signal to provide a product signal having upper and lower frequency components, a low pass filter to eliminate the upper frequency component of the product signal, and an integrator to produce a phase oscillator control reference signal representative of the phase of the roll eccentricity from the lower frequency component of the product signal, the oscillator varying the phase of the first and second reference signals in response to changes in the phase oscillator control reference signal, the output of the low pass signal being zero when the roll eccentricity signal component is removed form the force signal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000569058A CA1326521C (en) | 1988-06-09 | 1988-06-09 | Eccentricity compensator for rolling mill |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000569058A CA1326521C (en) | 1988-06-09 | 1988-06-09 | Eccentricity compensator for rolling mill |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1326521C true CA1326521C (en) | 1994-01-25 |
Family
ID=4138167
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000569058A Expired - Fee Related CA1326521C (en) | 1988-06-09 | 1988-06-09 | Eccentricity compensator for rolling mill |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1326521C (en) |
-
1988
- 1988-06-09 CA CA000569058A patent/CA1326521C/en not_active Expired - Fee Related
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