GB1580066A

GB1580066A - Control circuitry for use in regulating the thickness of material rolled in a roll stand

Info

Publication number: GB1580066A
Application number: GB4020877A
Authority: GB
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1976-09-28
Filing date: 1977-09-27
Publication date: 1980-11-26
Also published as: DE2643686C3; DE2643686A1; JPS5343064A; JPH0156842B2; SE7710798L; DE2643686B2

Description

(54) CONTROL CIRCUITRY FOR USE IN REGULATING THE THICKNESS OF MATERIAL ROLLED IN A ROLL STAND (71) We, SIEMENS AKTIENGESELLSCHAFT, a German company, of Berlin and Munich, Germany (fed rep), do hereby declare the invention, for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to control circuitry for use in regulating the thickness of material rolled in a roll stand which comprises roll gap control mechanism, the circuitry comprising a load roll gap controller arranged to operate in dependence upon the roll force, and a threshold-value setting device for presetting an insensitivity range to prevent the load roll gap controller being affected by roll force fluctuations produced by eccentricities of the rolls.

There is disclosed in the supplement to the Siemens-Zietschrift 1973 "Antriebstechnik und Prozessautomatisierung in Hiitten- und Walzwerken" an apparatus for regulating the thickness of the material issuing from the roll stand, wherein the load roll gap is formed of the no-load or empty position of the roll gap control mechanism and of the springing up or positional fluctuations of the roll stand, which is derived from the measured roll force. There is provided a threshold, in the region of which any roll force fluctuations occurring have no effect on the controller. For suppressing these roll force fluctuations, which are due to eccentricities of the rolls, the threshold values are defined by storing in a counter the maximum values of the fluctuation amplitudes which occur during at least one revolution with the rolls run together.The position of the rolls as controlled by the roll gap control mechanism is varied during operation only when the roll force falls below or exceeds the lower or upper reading of the counter.

There is disclosed in German Patent Specification 2 036 965 an arrangement for determining and evaluating during operation roll force fluctuations which are caused by roll eccentricities, which arrangement, instead of presetting constant threshold values, renders possible a continuous automatic adaptation of the threshold values to the momentary (i.e. instantaneous) roll force fluctuations. For this purpose, there is connected in parallel with the input amplifier of an analog-digital converter which determines the measured roll force a variable resistor whose resistance value is varied in dependence upon the momentary amplitude of the roll force fluctuations by means of an evaluating logic circuit connected to the output side of limit-value signalling devices which are connected to the output of the amplifier and adjusted in pairs to different response values.Consequently, only those roll force variations emanating from the material being rolled which exceed the momentary amplitude of the roll force fluctuations are passed on to a device for regulating the thickness of the material being rolled.

According to the present invention there is provided control circuitry for use in regulating the thickness of material rolled in a roll stand which comprises roll gap control mechanism the circuitry comprising a load roll gap controller arranged to operate in dependence upon the roll force, and a threshold-value setting device for presetting an insensitivity range to avoid the regulation being affected by roll force fluctuations produced by eccentricities of the rolls, there being slaved to said load roll gap controller a position controller for the roll gap control mechanism, and there being a further controller for correcting minor roll force or position fluctuations, including those produced by eccentricities of the rolls, by supplying a further desired value to influence the position controller, said threshold value setting device being arranged to limit the magnitude of said further desired value and being operable automatically to adapt its threshold-value to the momentary amplitude of the periodic roll force fluctuations caused by the eccentricities of the rolls.

For a better understanding of the invention and to show how it may be carried into effect reference will now be made, by way of example, to the accompanying drawings in which: Figure 1 shows a first embodiment of the invention; Figure 2 shows a second embodiment of the invention; Figure 3 shows a first form of threshold-value setting device; Figure 4 shows a second form of threshold-value setting device; and Figure 5 shows a third form of threshold-value setting device.

In accordance with Figure 1, a position controller 3 is slaved to a load roll gap controller 1.

A position desired value S* is formed from the no-load position S o* and from the output quantity AS T of the load roll gap controller at an interposed addition point. The actual values of the position and of the roll force are measured by means of the piston 10 of an hydraulic screw-down gear or roll gap control mechanism.

A further controller 2 operates for the purpose of a simple desired value formation, not as a roll force controller, but as a spring-up or position fluctuation controller. A desired value C.F * is formed of the difference of the load roll gap actual value h (or load roll gap desired value h *) and from the position desired value S t delayed in a delay device 8 to the extent of the inherent response time of the position regulation. The spring-up or position fluctuation actual value is formed in a matching amplifier 7 which takes account of the characteristic curve of the stand. The controller 2 also acts on the input of the position controller 3.In this way, the position controller 3 receives an additional desired value AS 2* which so adjusts the position in the opposite sense that the periodic fluctuations which are produced in the roll force F and in the spring-up or position C.F. respectively by the roll eccentricities, and hence the load roll gap fluctuations, are corrected.

This arrangement in itself does not initially effect any improvement in the dynamic behaviour. However, since the spring-up or position fluctuation controller 2 is not slaved to the load roll gap controller 1, it is permissible to limit its controller output and hence the additional position desired value A 5*2 by means of a limiter 4 to the value necessary for the correction of the periodic fluctuations owing to eccentricities in the rolls. In this way, it is possible to avoid unnecessary adjustments of the piston position. The limitation for AS2 is preset by a threshold-value setting device 6 and adjusted by way of a matching stage 5.

The threshold-value device 6 has in addition the function of withholding the periodic fluctuations of the load roll gap actual value from the load roll gap controller 1. The actual-value fluctuations consist of the fluctuations of the position S and the residual fluctua tions of the spring-up or position fluctuation magnitude C.F. The position fluctuations arise owing to the action of the spring-up controller 2 and compensate for the roll gap fluctuations caused by the rolls.

The threshold-value setting device 6 is so constructed that it automatically adjusts itself to the level of the periodic actual value fluctuations. The output quantity E of the thresholdvalue device must correspond to the mean of the input value. There may be employed as the threshold value device, for example, the arrangement disclosed in German Patent Specifica tion 2 036 965. Owing to the slaved position regulation, but the threshold magnitudes E and the additional desired value AS 2 have the same dimension, namely that of a travel. The limitation of AS 2* can therefore be readily derived from E. For taking account of the residual ripple of the spring-up or position fluctuation actual value, E is corrected to E' in the matching stage 5. The correction is readily effected by an adjustable correction factor.The magnitude of the correction factor depends upon the gain of the spring-up or position fluctuation controller 2.

The threshold magnitude E' reduced to the extent of the residual ripple determines the magnitude of the limitation. The controller 2 is consequently given a working range in which only those position changes which occur for correcting the periodic load roll gap fluctuations on the basis of its own regulating action are carried out.

The controller arrangement according to Figure 1 operates as follows: If, in addition to the periodic roll force fluctuations caused by roll eccentricities or defective roundness of the rolls. an additional roll force variation occurs due to a variation of the resistance of the material or of the thickness of the material, the additional desired value AS 2* first reaches the limit values of the limiter 4 and the position S, which corresponds to the sum S * - AS 2*, is not further changed. However, the spring-up or position fluctuation actual value C.F. and the roll gap actual value h do change.

The load roll gap controller 1 thereby intervenes without the position actual value first having had to be necessarily brought into the incorrect direction. The formation of the desired value C.F * for the spring-up controller 2 with the aid of the position desired value S * has the effect that the spring-up controller 2 is cleared as rapidly as possible from the limitation after the action of the load roll gap controller 1.

The position desired value S * used for the formation of C.F * is delayed in the delay device 8 by the inherent response time of the position regulation to S .. It therefore also corresponds dynamically to the mean of the position actual value. In this way, an additional mean value formation for the position actual value is rendered unnecessary.

The described regulating arrangement affords an accurate separation of the working ranges of the load roll gap and the roll force or spring-up (position fluctuation) regulations. In addition, the arrangement affords the following advantages: - A position regulation can be supplemented stepwise by a load roll gap regulation and a spring-up (position fluctuation) regulation.

- The regulating arrangement may also be operated stepwise. The regulations superimposed upon the position regulation can be simply tested by release during current operation.

- The no-load position is simply set with the load roll gap and spring-up (position fluctuation) control blocked. A change-over of controller functions and a follow-up of the controllers are unnecessary.

There is illustrated in Figure 2 a regulating arrangement in which the desiredvalue/actual-value comparison points of the load roll gap and spring-up (position fluctuation) controllers 1 and 2 are combined at one point. A comparison is made between * andh, wherein h = C.F. e S *v if formed. Since in addition h * must be equal to C.F. * = S *, this comparison also holds good for C.F. * and C.F. is S * if equal to S *v. This condition is satisfied within the regulating range of the spring-up or position fluctuation control, because in this case the output of the load roll gap controller 1 does not change, and hence the delay is of no importance.

The spring-up (position fluctuation) controller 2 is constructed as a controller having a proportional action. The load roll gap controller 1 is constructed as a controller having integral action and is connected on the output side of the spring-up (position fluctuation) controller 2 in accordance with the proposed arrangement.

The threshold-value or desired-value setting device 6, of which the output quantity is automatically adapted to the periodic fluctuations, only serves to determine the eccentricity.

It adjusts the level of the limitation. The mean of the actual value of the thickness h, which is reflected in the threshold value setting device, is a pure auxiliary magnitude which is not required for the regulation itself.

The limiter 4 has the amplification factor 1 below the limiting value, and inverts the sign.

Manner of operation: As long as the limit values in the limiter have not been reached, the control signals at the input of the controller 1, which are inverse in relation to one another, add together to form zero and only AS *2 is effective (spring-up or position fluctuation control). When the limit value is reached, the controller 1 receives an input signal owing to preponderance of the direct output of the controller 2, and it shifts the position S by means of AS ,* until equilibrium again exists by way of the revertive Signal S *v at the input of the controller 2. In this way, the mean value deviation is corrected (= load roll gap regulation).

The proposed arrangement avoids zero-point errors by a number of comparison points and renders possible a simple construction. By avoidance of the use of a mean actual value of the thickness, a good dynamic action is obtained.

Secondary conditions, such as allocation of the regulating arrangement to the two pistons of the hydraulic roll gap control mechanism of a rolling mill stand with corresponding parallel guiding, optionally additional slaving of a speed regulation, all release conditions, corrections, indications, etc., are not shown.

The arrangement for automatically determining the eccentricity as proposed in German Patent Specification 2 036 965 is, in principle, suitable for the proposed regulating arrangements. In accordance with Figure 3, however, there is applied to the input amplifier 12 of an analog-digital convertor 11, instead of the spring-up or position fluctuation C.F, the instan taneousvalueofthe load roll gaps + C.F. Limitvaluesignalllingdevices 15 and 16 provided on the output side of the input amplifier 12 test the instantaneous value as to increase or reduction and activate a logic circuit 17, which converts the input signal momentarily present into a pulse train which is applied to a counter 13.The reading of the counter is fed back to the input amplifier through a digital-analog convertor 14. limit-value signalling devices 19 to 24 succeed the input amplifier 12 either directly or with the interposition of an amplifier 18. The response values of the devices 19 to 24 are graded in pairs, while the limit-value signalling devices 23 and 24 are adjusted to the lowest response value and apply their output quantities either directly or through time stages 25 and 26 to an evaluating logic circuit 27. The output quantity E of the evaluating logic circuit 27 controls a variable resistor 28, for example a digital-analog convertor, which is connected in parallel with the input amplifier 12. The mean value of the load roll gap is consequently represented in the counter 13 of the analog-digital convertor 11.The eccentricity E is available at the output of the evaluating logic circuit 27.

A disadvantage of this arrangement is that, due to the action of the digital-analog convertor 28 and the resultant change in the amplification of the amplifier 12, the sensitivity of the limit-value signalling devices 15, 16 and 19 to 24 for the extent to which the ascertained eccentricity band is exceeded or fallen below depends upon the extent of the eccentricity itself.

In accordance with Figure 4, therefore, a fixed amplification is advantageously provided for the amplifier 12 and the limit-value signalling devices 15, 16 and 19 to 22 are preceded by comparison points at which the voltage to be detected is compared with the output of the digital-analog convertor 28. The fixed adjustment value of the limit-value signalling devices then only corresponds to the deviation from the instantaneously detected eccentricity band.

The response direction of the limit-value stages is fixed whether the band is exceeded or fallen below. For the purpose of the comparison, the limit-value stages 15, 16 and 19 to 22 are preceded by amplifiers 29 and 30. The comparison voltage is preset by an amplifier 31.

There is set up at the output of the amplifiers 29 and 30 a voltage which corresponds to the deviation from the eccentricity band. For defining the response point, a fixed comparison voltage is desirably also applied to the limit-value stages. The response point can be fixed by variation of this voltage or of the amplification factors of the amplifiers 29 and 30. If limit-value signalling devices responding to a comparison of the input voltages are used, it can be defined by the polarity of the fixed comparison voltage whether the limit-value signalling devices respond above or below the eccentricity band.

For a further simplification in accordance with Figure 5, there is provided instead of the analog-digital convertor, a unit 11 operating on an analog basis for the formation of the mean value with the aid of an integrator 32. The eccentricity band determined controls for both signal directions the limitation of the limiter 33 by way of the amplifiers 34 and 35. The output signal of the amplifier 12 is present directly and inversely at an amplifier 36 preceding the integrator 32.

As long as the value at the output of the amplifier 12 has a magnitude which does not cause the limiter 33 of the amplifier 36 to become operative, the signals at the input of the amplifier 36 balance one another and the integrator 32 does not change its output. When the input value of 12 changes by more than the amplitude of the fluctuation band determined, the limiter 33 becomes operative and, due to the predominance of the direct input of the amplifier 36, the integrator 32 is fed until the new mean value has been stored.

It is to be appreciated that. in embodiments in which the arrangement of Figure 3, 4 or 5 is employed as the threshold-value setting device 6, the load roll gap actual value h can be provided by the signal S + C.F.

The embodiments prevent false control signals for the regulation of the load roll gap, dnd also correct the fluctuations in thickness without impairment of the dynamic behaviour of the control.

WHAT WE CLAIM IS: 1. Control circuitry for use in regulating the thickness of material rolled in a roll stand which comprises roll gap control mechanism, the circuitry comprising a load roll gap controller arranged to operate in dependence upon the roll force, and a threshold value setting device for presetting an insensitivity range to avoid the regulation being affected by roll force fluctuations produced by eccentricities of the rolls, there being slaved to said load roll gap controller a position controller for the roll gap control mechanism, and there being a further controller for correcting minor roll force or position fluctuations, including those produced by eccentricities of the rolls, by supplying a further desired value to influence the position controller, said threshold value setting device being arranged to limit the magnitude of said further desired value and being operable automatically to adapt its threshold-value to the momentary amplitude of the periodic roll force fluctuations caused by the eccentricities of the rolls.

2. Control circuitry according to claim 1, wherein the threshold-value device is coupled via a matching stage. having a correction value which is adjustable, to a limiter which succeeds said further controller.

3. Control circuitry according to any one of the preceding claims which is arranged such that. when the circuitry is in operation. a desired value for said further controller will beformed from values consisting of or including an actual or desired value for said load roll gap controller, and a position desired value delayed in a delay device by the inherent response time of said position controller.

4. Control circuitry according to any one of the preceding claims, wherein said further controller and said load roll gap controller are connected in series.

5. Control circuitry according to claims 3 and 4 combined, wherein the desired value for said further controller will be formed from said desired value for the load roll gap controller, said delayed position desired value, and an actual value of the stand force or position fluctuations.

6. Control circuitry according to claim 5 when claim 3 is appendent to claim 2, wherein the output of said further controller is connected to the load roll gap controller both through the limiter and bypassing the limiter. the limiter providing polarity inversion.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. eccentricity band is exceeded or fallen below depends upon the extent of the eccentricity itself. In accordance with Figure 4, therefore, a fixed amplification is advantageously provided for the amplifier 12 and the limit-value signalling devices 15, 16 and 19 to 22 are preceded by comparison points at which the voltage to be detected is compared with the output of the digital-analog convertor 28. The fixed adjustment value of the limit-value signalling devices then only corresponds to the deviation from the instantaneously detected eccentricity band. The response direction of the limit-value stages is fixed whether the band is exceeded or fallen below. For the purpose of the comparison, the limit-value stages 15, 16 and 19 to 22 are preceded by amplifiers 29 and 30. The comparison voltage is preset by an amplifier 31. There is set up at the output of the amplifiers 29 and 30 a voltage which corresponds to the deviation from the eccentricity band. For defining the response point, a fixed comparison voltage is desirably also applied to the limit-value stages. The response point can be fixed by variation of this voltage or of the amplification factors of the amplifiers 29 and 30. If limit-value signalling devices responding to a comparison of the input voltages are used, it can be defined by the polarity of the fixed comparison voltage whether the limit-value signalling devices respond above or below the eccentricity band. For a further simplification in accordance with Figure 5, there is provided instead of the analog-digital convertor, a unit 11 operating on an analog basis for the formation of the mean value with the aid of an integrator 32. The eccentricity band determined controls for both signal directions the limitation of the limiter 33 by way of the amplifiers 34 and 35. The output signal of the amplifier 12 is present directly and inversely at an amplifier 36 preceding the integrator 32. As long as the value at the output of the amplifier 12 has a magnitude which does not cause the limiter 33 of the amplifier 36 to become operative, the signals at the input of the amplifier 36 balance one another and the integrator 32 does not change its output. When the input value of 12 changes by more than the amplitude of the fluctuation band determined, the limiter 33 becomes operative and, due to the predominance of the direct input of the amplifier 36, the integrator 32 is fed until the new mean value has been stored. It is to be appreciated that. in embodiments in which the arrangement of Figure 3, 4 or 5 is employed as the threshold-value setting device 6, the load roll gap actual value h can be provided by the signal S + C.F. The embodiments prevent false control signals for the regulation of the load roll gap, dnd also correct the fluctuations in thickness without impairment of the dynamic behaviour of the control. WHAT WE CLAIM IS:

1. Control circuitry for use in regulating the thickness of material rolled in a roll stand which comprises roll gap control mechanism, the circuitry comprising a load roll gap controller arranged to operate in dependence upon the roll force, and a threshold value setting device for presetting an insensitivity range to avoid the regulation being affected by roll force fluctuations produced by eccentricities of the rolls, there being slaved to said load roll gap controller a position controller for the roll gap control mechanism, and there being a further controller for correcting minor roll force or position fluctuations, including those produced by eccentricities of the rolls, by supplying a further desired value to influence the position controller, said threshold value setting device being arranged to limit the magnitude of said further desired value and being operable automatically to adapt its threshold-value to the momentary amplitude of the periodic roll force fluctuations caused by the eccentricities of the rolls.

7. Control circuitry according to any one of claims 4 to 6, wherein said load roll gap

controller has integral action.

8. Control circuitry according to any one of the preceding claims, wherein, in use, there will be applied to the threshold-value setting device as input quantity the sum of the actual value of the stand position and of the actual value of the fluctuations, derived from the roll force.

9. Control circuitry according to any one of the preceding claims, wherein the thresholdvalue setting device comprises an analog-digital convertor, direction-sensitive limit-value signalling devices which are adjusted pair-wise to different response values, an evaluating logic circuit succeeding the limit-value signalling devices, and a variable resistance controlled by said logic circuit and connected via an amplifier to provide an output of the thresholdvalue setting device and to one input of respective comparison members in the analog-digital convertor which each precede some of said limit-value signalling devices and also limit-value stages also contained in the analog digital convertor, the other input of said respective comparison members being connected to the output of an input amplifier in the analog-digital convertor, the threshold-value setting device being such that in use a comparison voltage of preset value will be applied to said limit-value signalling devices and to said limit-value stages.

10. Control circuitry according to any one of claims 2 to 8, wherein the threshold-value setting device comprises: a mean value former which is arranged to operate on an analog basis and which comprises an input amplifier and an integrator; direction-sensitive limit-value signalling devices which are adjusted pair-wise to different response values; an evaluating logic circuit succeeding the limit-value signalling devices; a variable resistance which is controlled by said logic circuit and which is connected via an amplifier to provide an output of the threshold-value setting device, to one input of respective comparators each of which precedes a part of said limit-value signalling devices, and to a series arrangement comprising two amplifiers which control a limiter in the mean value former; the output of the input amplifier of the mean value former being connected on the one hand directly to one input of an inverting amplifier which precedes the integrator, and on the other hand to the other input of the inverting amplifier via the last-mentioned limiter and to the other input of each of said comparators.

11. Control circuitry substantially as hereinbefore described with reference to Figure 1 or 2 of the accompanying drawings.

12. Control circuitry according to claim 11, when incorporating a threshold value setting device substantially as hereinbefore described with reference to Figure 3, 4 or 5 of the accompanying drawings.

13. Control circuitry according to any one of the preceding claims, when operably connected to a roll gap control mechanism for a roll stand.

14. Control circuitry according to claim 13, wherein the roll gap control mechanism is hydraulically operated.