SU1135510A1 - Low-pass filter for suppressing resonance of rolling process control circuit - Google Patents

Abstract

A LOW FREQUENCY FILTER FOR THE ADJUSTMENT OF THE RESONANCE OF THE REGULATION REGULATION OF THE ROLLING PARAMETER, containing a signal symbol meter, a module meter and a gain corrector, the corrected input of which is connected to the signal meter input of the signal, and the corrective input with the modulator output of the meter and the one that in order to more fully suppress the resonance and increase the speed of the control loop, a nonlinear integrator of the accruing signal is introduced into it with the restriction of the integration results, the velocity meter , a nonlinear converter, an adder, and a device for differentiating the falling signals, the nonlinear integrator input is connected to the output of the signal meter, and its output is connected to the input of the module meter, the nonlinear converter input is connected to the speed meter, and its output is to the signal level input O) a sign meter, the input of the device for differentiating the falling signals is connected to the output of the gain corrector, and its output is connected to the first input of the adder, the second input of which is connected to the output of the corrector usi Yeni. to eat

Description

The invention relates to elements of a process control system, namely, a strip thickness and tension control system for a rolling mill. The peculiarity of controlling the thickness and tension of the strip during its rolling is the periodic variation of these parameters, which inevitably occurs due to the eccentricity of the rolling and supporting rolls of the mill stands. These changes impose on the perturbation of the controlled oscillation parameters, the frequency of which depends on the speed of the band. The corresponding regulators do not have time to work out these oscillations. Moreover, the regulators increase their amplitude by about 2 times. Such a resonance affects the quality of regulation, reduces the stability of the rolling process, and increases the wear of the mill mechanisms, which are controlled by regulators. It is required to completely suppress the resonance of the control loop, but so as to co-store the response speed of the control. A linear filter is known which is capable of suppressing resonance, but at the same time the quality of testing slowly varying disturbances deteriorates. This degradation is due to the fact that the filter shifts the phase of oscillatory perturbations to the sides of the lag, which is equivalent to introducing an additional delay into the control loop, which requires a decrease in the control speed. The phase shift is especially harmful for suppressing resonance, since a phase lag leads to a shift of the resonant frequency towards lower frequencies. Fl Therefore, to satisfy both requirements at the same time (suppress resonance and maintain speed), a filter is needed that would not shift the phase of oscillation. lag behind. The shift to the side of operation is allowed, as the compensator is available in the delay control system, it contributes to the suppression of resonance. Closest to the present invention is a non-linear filter with a small phase shift, containing a corrector (multiplier), the corrected input of which is connected to the input of a signal sign meter (element with a two-digit relay characteristic), and the correction input 101 is connected to the output of a signal modulator meter. The output of the sign meter is connected to the input of the module meter via an aperiodic link. This filter attenuates the amplitude of oscillations with increasing frequency, not shifting half cycles of oscillations. In this case, the attenuation process does not depend on the initial amplitude of oscillations. The attenuation effect is due to the filtering action of the aperiodic link. The stability of all half-periods of oscillations in time was obtained by multiplying the filtering results by the original oscillations, which preserve the zeros of these oscillations (multiplying by zero gives zero). The absence of dependence on the initial amplitude is obtained by filtering the results of measuring the sign of the oscillations without controlling their amplitude 2J. However, the known filter not only preserves the zeroes of the oscillations, but also additionally introduces a false zero, which corresponds to zero of the signal of the aperiodic link and is shifted relative to the zeros of the original oscillations. The false zero shift varies with the frequency of oscillations by changing the shape of each half-period of oscillations, including breaking its symmetry. Such a distortion is equivalent to a shift in the phase of the first harmonic of the oscillations. This shift interferes with the complete suppression of the resonance and requires a decrease in the speed of working out slowly varying disturbances. In addition, spurious zero and the corresponding distortion of the waveform do not allow the use of forcing couplings by derivative, as a means of shifting the phase shift towards the leading side. The filter is not adapted to suppress resonance under conditions where the parameters of the control loop (thickness and tension of the strip) and the oscillation frequency (eccentricity) depend on the same parameter — the rolling speed. Filter rebuild required. The purpose of the invention is to more fully suppress the resonance and increase the speed of the control loop. This goal is achieved by the fact that the low-pass filter for suppressing the resonance of the rolling parameter control loop, contains a signal symbol meter, a module meter and a gain corrector, the adjustable input of which is connected to the signal meter meter input, and the correction input with the module meter output, additionally contains a non-linear incremental signal integrator with limited integration results, speed meter, nonlinear converter, adder and decay differentiation device signals, the nonlinear integrator input is connected to the output of the signal meter meter, and its input is connected to the module meter input, the nonlinear converter input is connected to the velocity meter, and its output is connected to the signal level signal level input input, the falling differentiation device input is connected to output of the gain corrector, and its output is connected to the first input of the adder, the second input of which is connected to the output of the gain control. The nonlinearity of the integrator consists in the presence of a constraint and in dropping the results of integrating into zero when the sign of the input signal is changed. The absence of a false zero allows the filter to force the filter results into the filter. Figure 1 is given a functional scheme of the proposed filter; in Fig.2 -4 graphics filter; Figures 5 and 6 are simplified diagrams of an exemplary embodiment of non-linear filter elements. The filter is (Fig. 1 corrector 1 (multiplier), the corrected input 2 of which is connected to the input of the meter with 3 digits of the signal, and correction input 4 with the output of the meter of the 5 module whose input is connected to the output of the integrator 6, and measurer 7 the speed of the stand, which determines the change in the loop latency, is connected via a nonlinear converter 8 to an input of a signal level setting of a 3-character meter. The output of the corrector I is connected to the output of the filter as a whole through the adder 9 directly and through the link 10 of the differentiation of falling signals. The device also contains a non-linearity converter of the converter 8, a regulator of tempo 12 of integrator 6 and one O4 sensor 13 of the forcing coefficient of the link 10. The nonlinear converter 8 implements the following function of the bandwidth and .. where K, j is the parameter, V v / nin manually set; total inertial lag of the control loop (sensor and actuator), s; minimum value: transport lag, from the stand to the sensor (at the maximum runway speed), s; U- and u. - Signals expressed as a fraction of the maximum value. The delay Tj is determined experimentally using probe signals. Nonlinearity (I) maintains the optimal filter setting at all bandwidths by varying the signal level of block 3, the integral of which is formed by block 6. The filter operates as follows. Figure 2 shows the filter operation for suppressing oscillations in the passband, at about the cutoff frequency (Fig. 3) and in the suppression bandwidth. (figure 4). Per unit of signals, their maximum value is taken. The action of the filter in each half period is the same, starting with zero. Curve D is the signal at the output of offset 1 (Fig. 1), multiplying the non-similarly oscillation (curve B) by the signal (curve B) generated by integrator 6. At the time of the change of the sign of the original oscillation (curve B), the meter 3 signs jumps the signal at the input of integrator 6, which begins to integrate this signal from zero (after the change of sign, only the increasing signal is integrated). The result, integration (curve C) is limited by violence at the level (curve D). During the saturation period, the original signal (curve B) is repeated at the output of corrector 1 without distortion. At the end of the half-cycle, at the time of the change of the initial oscillation (curve 5), the result is integ5

The calibration is reset to zero, the falling signal (curve D1 passes without integration. Therefore, everything repeats in the next half-period, starting with zero. Unit 11 and meter 7 through nonlinear converter 8 set the integration rate (curve B) and thereby the oscillation period from which the suppression is practically started, and the oscillation period, after which the oscillations can be considered practically suppressed. At the beginning of the suppression process, the integration rate (curve B) can be taken to coincide with the rate of growth of the original signal ( curve B) at the beginning of the half-period (Fig. 2). The middle of the process is the accumulation of integration at the end of the half-period (close to the process of Fig. 3). To determine the total suppression, you need to set the allowable remainder that corresponds to the increase in the integration results (Fig. 4, segment 0,2).

The amplitude attenuation by the proposed filter starts asymmetrically - from the leading edge (curve A) of each half period. Therefore, the phase shift of the first harmonic of filtering results in the direction of lag is inevitable. The link 10 for differentiating the falling signals compensates for this lag in phase (FIG. 3) by adding, using the adder 9 to the filter signal, the results of its differentiation. The sum signal is represented by curve B. Differentiation of only the falling signals provides no effect on the suppression process, which is carried out mainly by limiting the increasing signal. Fig. 5 shows an example of the implementation of a nonlinear integrator 6, and in Fig. 6 an element 10 of a nonlinear

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differentiation on the basis of operational amplifiers U. Integrating only the rising signal (FIG. 3) is obtained using two same-sex signals

5 (zener diodes D7 and D8) of amplifiers U1 and U2 due to the fact that in the feedback of each amplifier U1 (U2) the diodes D1 (D2) and DZ (D4) pass only the charging current of the integrating capacitor C1 (C2). The discharge of this capacitor passes outside the feedback of the amplifier V1 (V2) through the DZ diode (D6) and the resistor R3 (R4), having a sufficiently small resistance to provide the lowest time constant. Adjustable resistors 1 and 2 set the initial integration rate.

T the differentiation of only the falling signal (Fig. 6) is obtained using two one-way active capacitors C1 and C2 associated with the summing point of amplifier Y, which is also the adder 9 adding the differentiation results to the filter signal (resistor R3). Each capacitor C1 (C2) is charged through diodes D1 (D2) and DZ (DB) past the amplifier Y, and discharged through the summing point of the amplifier Y, the diode DZ (D4) and the resistor Pi (R2), which has a low resistance. Resistors R1 and R2, in addition, set the required forcing ratio of the filter.

The effectiveness of the proposed filter is to improve the quality of the rolled strip, reducing just the mill and the wear of its mechanisms.

These advantages are achieved by more fully suppressing the resonance and increasing the speed of the control loop containing the filter, which leads to a decrease in the high-frequency components of the thickness variation of the rolled strip.

Claims (1)

LOW FREQUENCY FILTER FOR SUPPRESSING THE RESONANCE OF THE ROLLING PARAMETER CONTROL CIRCUIT, containing a signal sign meter, module meter and gain corrector, ^{J the} corrected input of which is connected to the signal sign meter input, and the correcting input - with the output of the module meter, characterized in that in order to more fully suppress resonance and increase the speed of the control loop, a nonlinear integrator of the rising signal with restriction of integration results, a speed meter, non-linear An inverter, adder and differentiator of falling signals, the input of the nonlinear integrator connected to the output of the signal meter and the output to the input of the module meter, the input of the nonlinear converter connected to the speed sensor and its output to the input of the signal level of the sign meter , the input of the device for differentiating the decaying signals is connected to the output of the gain corrector, and its output is connected to the first input of the adder, the second input of which is connected to the output of the gain corrector. 1