EP0424709A2 - Method for compensating failures due to roll eccentricity - Google Patents

Abstract

When regulating the strip thickness, it has been found that the complex roller eccentricities resulting from the superimposition of several interfering influences are not adequately compensated for by the control methods which have become known to date. In order to also be able to compensate for complex roller eccentricities, it is proposed to determine the transfer function of the interference signal embodying the roller eccentricity and to derive controller parameters from this transfer function, on the basis of which roller eccentricity compensation signals can be calculated. This compensates for the roll eccentricities based on the adaptive control principle. <IMAGE>

Description

The invention relates to a method for regulating the thickness of rolled strip and for compensating for disturbances caused by roller eccentricities according to the preamble of claim 1 and a device for carrying out this method.

In recent years, the demands for increasingly narrow tolerances with regard to the thickness of rolled strips have been increasing. It was soon found that trying to meet these tight tolerances would adversely affect the influence of roll eccentricities. For this reason circuits have been developed which should compensate for the influence of roll eccentricities which minimizes the quality of the rolled strip.

It is known, for example, to first measure the eccentricity of the rolls when the rolls are moved together, to store these measured values and to use these measured values again during the rolling process to compensate for the roll eccentricity. Changes in the eccentricities of the rolls due to roll wear, thermally influenced changes, changes due to slippage, etc. can be caused by this compensation sationsverfahren are no longer recognized, so that compensation, if at all, can only be insufficient.

EP-PS 0170016 includes a method for compensating for the influence of roller eccentricities in the prior art, according to which an interference signal is filtered out from the actual value of the rolling force, the roller pitch and the stand spring constant with the aid of the backup roller speed and emulated by oscillators. The simulated interference signal is used to control the thickness controller for the roll stand.

The causes of eccentricities lie in grinding inaccuracies of the rolls, non-uniform wear, pressure fluctuations in the bearings of the rolls, thermally induced eccentricities and others. All of these disturbances can occur on each roller of the stand and are superimposed, so that very complex disturbance signal profiles result which can only be simulated to some extent exactly with considerable expenditure on oscillators. In addition, the rollers used have different diameters and are therefore operated at different speeds, so that a filter controlled by the backup roller speed cannot be set optimally for all rollers. This means that eccentricities cannot be compensated for adequately even with this method.

The invention is based on the object of demonstrating a method for regulating the thickness of rolled strip and for compensating for roller eccentricities, with which complex roller eccentricities resulting from superimposition of several interfering influences can be exactly compensated for. The invention lies further the object of further developing a device for performing the method for roller eccentricity compensation.

This object is achieved by the characterizing features of claims 1 and 5. Further features can be found in the subclaims.

• Figur 1 die schematische Darstellung eines Walzgerüsts mit Regeleinrichtungen,
• Figur 2 die schematische Darstellung des Walzenexzentri­zitäts-Kompensationskreises.

The invention is explained in more detail with reference to a drawing. Show

• FIG. 1 shows the schematic representation of a roll stand with control devices,
• Figure 2 is a schematic representation of the roller eccentricity compensation circuit.

In Fig. 1 a roll stand 1 is shown schematically. The rolling stand 1 has a sensor 2 for the actual rolling force F _i and a sensor 3 for the actual position S _i . The roll stand 1 is followed by a pick-up 4 for the actual strip thickness h _{i of} the strip that is running out. The scaffolding module M is represented by a spring. A thickness control system is assigned to the roll stand 1, which consists of a monitor control circuit 5, a gauge control circuit 6 and a position control circuit 7. In addition, a roller eccentricity compensation control loop 8 is provided. The nominal thickness h _{s of} the strip can be entered via an input unit E.

2 shows the schematic structure of the roller eccentricity compensation circuit 8. The compensation circuit 8 has an A / D converter 9 at the input and a D / A converter 10 at the output. A non-linear filter 11 is coupled to the A / D converter 9. At the same time is the exit of the gauge Meter circuit 6, on which a position preset value S _{AGC can be} tapped, connected to the filter 11 via a delay element 17, which impresses the position preset value S _{AGC on} the dynamic behavior of the position control loop 7. The A / D converter 9 continues to operate on a negator 12 which is connected to an adder 13. The output of the filter 11 is also connected to the adder 13. The output of the adder 13 is coupled to an identification element 14, which in turn works on a computing element 15 for calculating controller parameters. The outputs of the circuit 15 and the adder 13 are connected to a controller 16. The output of the controller 16 is routed via the limiter 18 and the filter 19 on the one hand to the identification element 14 and on the other hand to the D / A converter 10.

The function of the compensation control loop 8 is described below.
The compensation control circuit 8 requires the rolling force signal F _i as input signals and the position setting value S _AGC formed by the gaugemeter circuit 6. This only requires signals that are already available for conventional thickness control, so that additional transducers, for example for the speed, etc., are not necessary.

The analog rolling force actual signal F _i is digitized in the A / D converter 9 and applied to the filter 11. The filter 11 is a non-linear low-pass filter. In order to smooth the actual rolling force signal well, ie to separate the higher-frequency interference signal, but at the same time to be able to react quickly to changes in the amplitude of the input signal, the filter 11 is controlled by the position default value S _AGC , the dynamic behavior of the position control loop 7 being taken into account at the same time. The rolling force signal at the filter output is shown in the ad dierer 13 added to the actual rolling force signal F _i negated in the negator 12. The interference signal F _s caused by the roller eccentricities is thus present at the output of the adder 13.

wird ermittelt.
Die unbekannten Parameter a_1-m, b_1-n werden dabei mit Hilfe eines rekursiven Parameterschätzverfahrens geschätzt.The dynamic behavior of the interference signal F _{s is} identified in the identification element 14, ie the Z transfer function of the interference signal F _s

is determined.
The unknown parameters a _1-m , b _1-n are estimated using a recursive parameter estimation method.

Due to the many superimposed eccentricities, a very complex interference signal F _{s has to be} simulated, which would result in a high-order differential equation. By simplifying the order of the interference signal in the model (1) can be significantly reduced without major disadvantages in the simulation, so that the parameters of the signal model can be estimated on-line. Due to the simplification, the sampling frequency must be increased; however, modern computers meet these requirements.

The parameters of the controller 16 are calculated in the computing element 15 as a function of the interference signal transfer function (1) determined and with the aid of a controller synthesis method. The controller 16 is thus adapted to the current interference signal behavior, and compensation signals S _{k are} generated taking into account the desired control loop behavior and the determined interference signal F _s . So that the amplitudes of the compensation signal S _{n are} not too great If the thickness of the rolled strip could be adversely affected and switched to the position control loop 7, the compensation signal S _k in the limiter 18 is limited to definable maximum amplitudes. To calm the controller output, the compensation signal S _k can be smoothed with a filter 19. After D / A conversion, the compensation signal S _k at the position set value S _AGC de _s Gaugemeterkreises 6 is added. The compensation signal S _k is fed back to the identification circuit 14 at the same time.

Reference symbol overview t

• 1 roll stand
• 2 transducers F _i
• 3 transducers S _i
• 4 transducers h _i
• 5 monitor control loop
• 6 Gagemeter circle
• 7 position control loop
• 8 roller eccentricity compensation control loop
• 9 A / D converter
• 10 DA converters
• 11 filters
• 12 negators
• 13 adders
• 14 identification link
• 15 computing element
• 16 controllers
• 17 delay element
• 18 delimiters
• 19 filters

Claims (8)

1. Method for regulating the thickness of rolled strip using the gauge method and for compensating for disturbances caused by roller eccentricities, taking into account the size of the roll gap, the rolling force and the stand module.
marked by a) the known separation of the interference signal (F _s ) based on the eccentricity of rolls from the rolling force signal (F _i ), b) the identification of the interference signal (F _s ) thus obtained by determining its transfer function, c) the subsequent calculation of the controller parameters as a function of the ascertained interference signal transfer function and with the aid of a controller synthesis process, d) determining the compensation signal (S _k ) from the interference signal (F _s ) and the corresponding controller parameters in the adaptive controller (16) to compensate for the eccentricity error, e) and the connection of the compensation signal (S _k ) to the position control loop (7). 2. The method according to claim 1,
characterized,
that the interference signal (F _s ) is filtered out from the rolling force signal (F _i ) via a non-linear filter (11), which is controlled with the position _{setting value} (S _AGC ) taking into account the dynamic behavior (delay element 17) of the position control circuit (7), and
that the interference signal (F _s ) is determined by adding the rolling force signal thus obtained to the rolling force signal (F _i ). 3. The method according to claim 1 or 2,
characterized,
that the disturbance signal curve is simulated on-line as a transfer function in the course of the adaptive control by estimating the parameters by means of a recursive parameter estimation method. 4. The method according to at least one of claims 1 to 3,
characterized,
that which _(to S) to the position command is added to the preset position value (S _AGC) of the Gaugemeterkreises (6) is generated due to the disturbance signal (F _s) and derived from the transfer function of controller parameters, a position correction signal (S _k). 5. The method according to at least one of claims 1 to 4,
characterized,
that the position correction signal (S _k ) can be limited in its amplitude and
that high-frequency compensation signals can be smoothed by filtering the controller output. 6. Device for carrying out the method according to at least one of claims 1 to 5, with a monitor control loop (5), a gaugometer control loop (6), a position control loop (7) and an eccentricity control loop (8),
marked by
a filter (11), which filters out the interference signal (F _s ) from the rolling force signal (F _i ) as a function of the position value (S _AGC ) of the gaugemeter circuit (6), a delay element (17) giving the position value (S _AGC ) the dynamic Behavior of the position control loop (7)
an adder (13) which adds the negated rolling force signal (F _i ) to the rolling force signal thus obtained,
an identification circuit (14) in which the transfer function of the interference signal (F _s ) is determined,
a computing element (15) which derives control parameters from the transfer function of the interference signal (F _s ), and
an adaptive controller (16), which generates a position correction signal (S _k ) due to its controller structure of the controller parameters and the interference signal (F _s ), and whose output is switched to the position control circuit (7) with the output of the gaugemeter circuit (6) is. 7. The device according to claim 6,
characterized,
that an A / D converter (9) is provided which digitizes the rolling force signal (F _i ) and that a non-linear digital low-pass filter is used as the filter (11). 8. The device according to claim 6 or 7,
characterized,
that the adaptive controller (16) is followed by a limiter (18) for the position correction signal (S _k ) and a filter (19).

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