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

Definitions

• the invention relates to a method for suppressing the influence of roll eccentricities on the control of the rolling stock thickness in a roll stand, the control providing a dead zone that is insensitive to signal fluctuations caused by the roll eccentricities, the zone width of which varies depending on the size of the signal fluctuations becomes.
• the rolling stock thickness As an interesting control variable, cannot be easily measured in terms of control technology at the point of its creation, namely the roll gap, and therefore cannot be used to directly correct faults, e.g. Eccentricities of the rollers can be used. According to the so-called gauge principle, however, the instantaneous rolling stock thickness ha in the area of the roll gap can be calculated from the
• AGC automatic gauge control
• the rolling force is detected on the basis of this relationship by means of a rolling load detector and used to regulate the thickness of the rolling stock. If the roll gap increases, for example due to an increase in the inlet thickness of the rolling stock, this leads to an increase in the rolling force F w ; This increase is detected, the control position s of the rollers being reduced by the control, so that the rolling force F w increases further and the rolling stock thickness is regulated back to its target value becomes.
• the rolling stock thickness ha is not available alone, but only together with the roll eccentricity ⁇ R, which causes a periodic increase and decrease in the rolling force F w during the rolling process.
• the increases and decreases in the rolling force F w caused by the eccentricities are, however, incorrectly interpreted by the AGC system as an increase or decrease in the roll gap, as a result of which the rolling force F w is automatically increased or decreased via the setting position s and so that the full extent of the eccentricities is rolled into the rolling stock.
• the object of the invention is to optimize the adaptation of the width of the dead zone as a function of the eccentricities that occur.
• this object is achieved in that, in the method of the type mentioned at the outset, the zone width is varied as a function of an ongoing statistical evaluation of the signal fluctuations.
• the zone width is varied as a function of an ongoing statistical evaluation of the signal fluctuations.
• the standard deviation of the signal fluctuations from their mean value is used to determine the zone width.
• the standard deviation is used to determine a variable that optimally reflects the current extent of the eccentricity-dependent signal fluctuations for setting the dead zone.
• the determination of the standard deviation is particularly simple to perform in terms of computation, as a result of which the hardware or software expenditure for realizing this computing function is comparatively low.
• the values continuously determined for the standard deviation are weighted with a predetermined factor of the order of about 1 to A, preferably 2 to 3.
• the statistical evaluation of the signal fluctuations is based on an observation period that is based on the roller circulation period or a multiple thereof of corresponds. In this way it is taken into account that the signal fluctuations, despite their unpredictable, A So correct statistical nature with the rotation of the roller.
• the signal fluctuations for their statistical evaluation determine base values with a sampling frequency which is in a fixed relationship to the roller speed. This results in a number of base values independent of the roller speed within the observation period, which makes it possible to predefine a specific computing capacity for statistical evaluation.
• signal fluctuations occurring at different points within the control can be used to set the width of the dead zone, provided that they correlate with the roller eccentricities.
• the signal values applied to the dead zone on the input side are preferably used for statistical evaluation.
• control system provides a zone which is insensitive to signal fluctuations caused by roller eccentricities and whose zone width is varied as a function of the signal fluctuations Improvement of the zone width and other influencing variables, for example for precontrol, on the basis of the techniques of processing unsharp certain input variables, in particular taking into account expert knowledge with regard to the process variable measurement value distribution and distribution occurring.
• a cost-effective, fast implementation of the improvement of the control which can be checked in particular by computer simulation, and the possibility of adapting the influence of the results of the control by the neural network or the fuzzy computing process is advantageously achieved by the in the further subclaims specified measures achieved.
• FIG. 1 shows a block diagram for the control of the rolling stock thickness in a rolling stand
• FIG. 2 shows an example for the setting of the width of the dead zone as a function of the standard deviation of the detected signal fluctuations
• FIG. 3 shows an example for the course of the signal fluctuation kung and and the adapted dead zone
• Fig. A an example of the computational procedure in a rolling process control
• Fig. 5 and 6 exemplary configurations of a neuro computer network value.
• FIG. 1 shows the block diagram of an AGC (auto atic gauge control) control for a roll stand 1 with an upper and lower support roll 2 or 3, two work rolls A and 5, and a hydraulic adjusting device 7 which can be actuated via a control valve 6 Setting the arrival Position s and a spring c «emulating the elasticity of the roll stand 1.
• the rolling stock 8, to which an equivalent material spring c M can be assigned in the roll gap, is rolled down by the two rolls A and 5 from an inlet thickness h to an outlet thickness h.
• the roll eccentricities can be described by an effective change in the roll radius ⁇ R.
• the setting position s is measured with a position sensor 9 on the setting device 7; the support roller speed n is recorded by means of a tachometer 10 on the support roller 3 and the rolling force F w is measured by means of a pressure sensor 11 on the roll stand 1.
• the measured actual value of the rolling force F w is fed to an adaptation amplifier 12 which reproduces the stand characteristic curve c r and which produces the actual springing value P w c G on the output side.
• the actual suspension value P w c G is supplied with a negative sign to a summing point 13 at which, according to equation (1) given above
• the summing point 13 is supplied with a value s ,, instead of the actual value of the setting position s.
• the difference signal at the output of the summing point 13 therefore not only contains
• the difference signal at the output of the summing point 13 is fed with a positive sign directly to another summing point 1A, which additionally has the same difference signal. is supplied via a limiter 15 with a negative sign.
• the limiter 15 transmits from the signal fed to it only those signal amplitudes which lie within a range x which preferably corresponds to the amplitudes of the eccentricities ⁇ R, so that precisely this amplitude range does not appear at the output of the summing element 1A.
• the limiter 15 thus forms, together with the further summing element 1A, a dead zone for all signal amplitudes which lie within the range b.
• the width b of the dead zone is set in such a way that it is suitable for those of the signal eccentricities R caused by signal fluctuations is insensitive.
• the signal at the output of summing point 1A which is free from the eccentricity-dependent signal fluctuations R, is fed to a roll gap controller 16 with a downstream correction amplifier 17, at the output of which a setpoint value s for the starting position appears.
• the output signal of the roll gap controller 16 is multiplied by the factor 1 + c ../ c G , so as to influence the path gain of the control loop
• the setpoint s at the output of the correction amplifier 17 is set via a delay device 18 with a delay corresponding to the natural time of the position control (position controller 22).
• the output signal s of the correction amplifier 17 has a positive identifier and the output signal of the limiter 15 is a further summing point via an adaptation amplifier 19 with a negative sign as an additional setpoint ⁇ s
• the final setpoint for the setting position at the output of the summing point 20 is compared at an additional summing point 21 with the actual value s supplied by the position transmitter 9, the comparison result via a position controller 22 and a downstream actuator 23 for actuating the control valve 6 and so that it is used to set the setting position s.
• base values x are first obtained from the difference signal at the output of the summing point 13 by means of a scanning element 2A. detected and a device 25 for statistical evaluation of the base values x. fed. Over a period of observation of N _ support values x1. whose standard deviation s from the mean x with
• the sampling is carried out as a function of the roller speed n.
• a control pulse generator 26 controlling the scanning element 2A is provided, the output-side control pulse frequency of which is dependent on that with the tachometer 10 measured roller speed n is controlled. Since the observation period on which the statistical evaluation of the signal fluctuations is based is based on a predetermined number of N base values x. there is, the observation period is automatically adapted to the respective roll circulation time.
• the determined value for the standard deviation ⁇ is multiplied in a correction element 28 arranged downstream of the device 25 by a predetermined factor in the range between 2 and 3 before it is sent to a control input 29 of the limiter 15 for setting the zone width b is supplied.
• FIG. 3 shows an example of the course of the signal fluctuations caused by the eccentricities ⁇ R at the output of the summing point 13 together with the zone width b regulated as a function thereof.
• FIG. 31 denotes the primary data input, for example the input dimensions, the material quality and the target values of the rolling process.
• the primary data will be Appropriately prepared in terms of control technology and a pre-calculation 32 is given, which calculates the rolling parameters and the setting values for the rolling mill. From the pre-calculation 32, the data arrive in a time-correct distribution 33 for the setting values of subordinate controls and controls 3A of the rolling mill 30, which is only shown schematically here.
• this feedback circuit is improved by the technique of regulating with unsharp input variables, in particular by neural networks, as shown by way of example in FIG. 5. A new self-learning behavior of the feedback circuit is achieved, which leads to a considerable improvement in the rolling technical result leads.
• 39 denotes a simple neural network which is well suited for strongly scattering values, the network nodes AO, as indicated, having a local influence in accordance with Gaussian curves. 6 have network nodes AI in the neural network A2 which are sigmoidally influenced. Networks of this type are also, but less well, suitable for the control and improvement of processes with less widely scattering measured values and input variables.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Control Of Metal Rolling (AREA)

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• 1992
  • 1992-09-22 DE DE4231615A patent/DE4231615A1/de not_active Withdrawn
• 1993
  • 1993-09-20 WO PCT/DE1993/000894 patent/WO1994006578A1/fr active IP Right Grant
  • 1993-09-20 AT AT93919021T patent/ATE147296T1/de active
  • 1993-09-20 US US08/403,920 patent/US5600982A/en not_active Expired - Lifetime
  • 1993-09-20 EP EP93919021A patent/EP0662017B1/fr not_active Expired - Lifetime
  • 1993-09-20 DE DE59305091T patent/DE59305091D1/de not_active Expired - Lifetime

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