AGC System Research Articles

Development of the production of high thickness-uniformity sheet in the new tandem cold strip mill at Kashima Steel Works

The new cold strip mill at Kashima Steel Works has been designed for high-thickness uniformity and strip flatness. Stands 1 to 3 use the pair-cross technology. For the gauge accuracy in the longitudinal direction, an advanced AGC system combining newly developed technologies is used. It is characterized by a non-interactive control of gauge and tension. Strip profile is mainly controlled at the three PC stands. A numerical simulation model of profile and flatness is used to optimize the setting of the actuators. The system can operate in two modes : “flatness” mode or “edge drop-free” mode.

Direct conversion-how to make it work in TV tuners

The problems of direct conversion tuners are briefly discussed and solutions are presented to automatically correct the inherent gain and phase errors using digital signal processing. We have built a hardware prototype for reception of analog and digital signals to carry out experiments. The direct conversion affects also the design of the preselection in the RF and IF filters, the local oscillator and to some extent the AGC system (automatic gain control). Novel ideas are discussed that perform an important advance towards an alignment-free tuner.

The Computer Control System and Algorithm for Plate Mill

Since 1988, We have made computer control reforming of hydraulic screwdown in five plate mills, and have achieved a series of satisfied system performance such as rapid response, the two side of rolls to move synchronistically, anti-interference etc., we also gained high—accuracy plate thickness. The statistics thickness variations within one plate are in range of 0.25 – 0.60 mm before reforming and are less than 0.03 – 0.15 mm after reforming. The errors of hitting aimed thickness less than ± 0.10 mm, The extreme variations of batch less than 0.07 mm. The techniques of reforming are mainly dynamic intelligent control of hydraulic screwdown system, synchronism control of hydraulic screwdown, eccentricity control method by rotary encoder, the curve of modulus of mill measured automatically, the control algorithm of reducing the variation within one plate, the hitting aimed thickness of plates and the application of stochastic process in AGC system etc. The techniques was fully and successfully industrialized to The Plate Mill of MaAnshan Iron & Steel Co. LTD and Steel Sheet Plant of Shanghai No.1 Iron & Steel Works.

Digital automatic gain control with lookahead, adaptive noise floor sensing, and decay boost initialization

An automatic gain controller for a digitized audio signal, comprising a buffer with a plurality of subframes. Each subframe contains digitized data samples of the signal, the subframes including at least one future subframe and a current subframe. Signal processing means (such as a DSP) is coupled to the memory for controlling gain of the audio signal represented by the current subframe in the buffer. The signal processing means includes means to control gain of the data samples using a stored program for computing a plurality of mean signal level values from the plurality of subframes, each mean signal level value in the plurality corresponding to one of the subframes. The program includes means for causing decay of gain on the signal represented by the current subframe when a first set of the mean values are each below a low threshold signal level. The program also has means for causing gain attack on the audio signal represented by the current subframe when a second set of the mean values are each above a high threshold signal level. The program also comprises means for shifting the data samples in one subframe in the future group into the current subframe for controlling gain of the audio signal after causing gain attack or decay. Thus, a voice messaging system under control of the program causes gain attack and decay on the audio signal represented by the subframes which attack and decay appear to occur without delay to a user of the audio signal. All control parameters are configurable. The AGC system is initialized using novel floor tracking and decay boost initialization methods which improve performance at the start of a call. Spike resistance can be set as high as desired.

水島No.1冷延タンデムミルにおける板厚精度向上対策

Recently, for thickness gauge of cold strip, higher accuracy is required by customers than ever. To supply high quality strip, we have developed a New AGC system, and have applied it to No.1 Cold Tandem Mill at Kawasaki steel's Mizushima Works in 1990.To decide revamping items, each item is evaluated using dynamic simulater. This revamping is composed of three functions as below. : (1)All stands back up roll roller type bearings as a substitute for oil film type bearings (mogoil bearings) (2)The new AGC controller (high-response AGC and non-interference fuzzy control) (3)The new sensors (strip speed meter of Laser Doppler Type)By this improvement, the thickness accuracy of strip is remarkably improved. The thickness accuracy is within 0.3% in the steady rolling and within 1.6% of finished thickness for a 0.8mm strip thickness in the unsteady rolling.

A parametrically driven PLL lock detector

A novel parametrically driven phase locked loop (PLL) lock detector is presented. The lock detector is described by a time-varying linear differential equation derived from the PLL's nonlinear dynamics. The time-varying nature of this detector equation results from the fact that it is parametrically driven by the output of the PLL's quadrature detector. A lock decision is made by comparing a detector equation state to a user-specified threshold. Also, the detector produces a D.C. voltage which may be capable of driving a phase locked receiver's coherent AGC system. Finally a laboratory experiment is described which demonstrates feasibility of the detector concept. Use of the new lock detector eliminates a class of problems associated with the simple phase quadrature lock detector. The problems result from the fact that the quadrature detector can produce a D.C. component under false lock conditions. This D.C. component may actually operate a phase locked receiver's coherent AGC system. It is possible that the AGC system could be fooled into adjusting receiver gain to produce a nominal (above lock detector threshold) value for the unwanted D.C. component. A positive lock indication would result, and the receiver would appear to be operating properly when, in fact, this was not the case.

Frequency‐dependent gain control by the minima in the temporal sound envelope

Conventional automatic gain control acts upon the average sound level, irrespective of whether there is a speech signal or not. As a result, during periods without a speech signal, background noise is amplified to levels experienced as “noisy” by the listener. This annoyance can be reduced by using the level of the temporal‐envelope minima, rather than the average sound level, to control the gain: the information‐bearing fluctuations typical for speech are preserved, whereas background noise, usually showing much less‐pronounced fluctuations, is presented at a nondisturbing level. This study investigates the effectiveness of a four‐channel AGC system in which the frequency‐dependent amplification factor is automatically controlled by the envelope minima in the respective frequency channel. The reference was a condition without gain control, but with the amplification in the different frequency bands adjusted to warrant 100% intelligibility in quiet. The effect of the gain‐control system on the signal appeared to be greatest in the case of stationary sounds, and smallest when a single speaker was present. Results for 10 listeners with a sensorineural hearing impairment show that, for various sounds frequently interfering in practice, with spectra that are comparable to that of the speech, the condition with gain control does not affect the speech‐reception threshold in noise, but substantially reduces the subjective impression of noisiness when no speech communication takes place.

Digital matched-correlator automatic gain control scheme applicable to MFSK modems

A new automatic gain control system designed specifically for MFSK modems is described. The AGC system developed has been designed to operate with the CABS MFSK modem. The gain control signal is derived directly from the noncoherent correlator outputs. A theoretical study of the behaviour of the AGC unit, under AWGN conditions, is also presented.

Optimum selection of speed regulation parameters for automatic generation control in discrete mode considering generation rate constraints

The paper deals with the optimum selection of a governor speed regulation parameter R in the design of an appropriate governor for automatic generation control of an interconnected power system in discrete mode taking into consideration the generation rate constraint (GRC). Investigations reveal that there is no necessity for a very low value of R as is usually the practice because under realistic operation of an AGC, a larger value of R can be acceptable and can even provide better dynamic responses. A governor designed with a larger value of R will be simpler and cheaper. A sensitivity analysis for an AGC system with a higher value of R reveals that the optimum integral gain setting obtained for nominal system parameters is quite robust for a ±25% change in system parameters.

冷延帯鋼製造技術の進歩

Since 20-high rolling mill and the other new equipments were installed, we have successfully improved the strip quality by means of AGC system, surface and shape controlling and others.Our experience of modernizing cold rolling lines, the progress of thickness control, the improvement of surface and shape and our view for future are introduced.

A radiation hard frequency reference IC

A high-stability radiation-hard crystal oscillator/divider fabricated in silicon-on-sapphire technology is described. Many analog functions are implemented in the chip, and an AGC system is used to reduce the influence of transistor parameter variations. Methods for obtaining radiation hardness by circuit design are discussed, and the particular problems associated with realizing analog circuits in SOS are addressed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A New AGC System Controlling Motor Current and Roll Position for Reversing Cold Mills

A New AGC System Controlling Motor Current and Roll Position for Reversing Cold Mills

High Quality Control in Hot Strip Mill

Construction on a new 1840 mm hot strip mill, at Nippon Steel’s Hirohata Works, began in June of 1982. This mill, replacing the existing mill, went into commercial operation on August 1, 1984. The mill’s high quality control systems have enabled us to achieve a high degree of accuracy in a number of areas, including, strip thickness, or strip crown and shape. The author and his team have developed an absolute mode AGC system that has allowed them to attain a greatly high degree of thickness accuracy for the full strip length. The system is comprised of four main subsystems organically combined, including several advanced techniques such as non-interferization between thickness and shape, a looper control of the optimum regulator type. Thickness accuracy has reached its highest level.

A New Roll Eccentricity Compensation System

A new roll eccentricity compensation system has been developed to guarantee the high gage accuracy of cold-rolled strip. The system uses the feedback of the gage deviations detected in the previous stages for controlling of the hydraulic screw-down. The controlling signals are optimized by an iteration procedure during rolling to ensure the stability of control and minimization of gage fluctuation.With a combination of the conventional AGC system, the system has been satisfactorily in operation since 1982 at the 5-stand tandem cold-rolling mill in the Sakai Works, Nisshin Steel Co., Ltd.

The performance of combined feedforward AGC and phase-locked AFC in a single sideband mobile radio receiver

The paper describes the results of a simulation of a coupled phase-locked AFC/feedforward AGC system with a two tone fading input. The theoretical predictions agree closely with those obtained under laboratory conditions, and show that considerable care should be exercised in the selection of the phase-locked loop bandwidth, normalised to twice maximum Doppler (ωn/2ωd). Failure to do so can result in nonoptimum feedforward AGC performance.

Feed forward AGC system for cold tandem mills.

Feed forward AGC system for cold tandem mills.

QNAR AGC systems for adaptive signal detection

In a previous paper we presented an NAR AGC system for regulation of noise power in presence of nonoverlapped signals and we showed its limitation in the case of overlapped signals. In this paper we consider the later case for which it is necessary to secure the NAR property all the time otherwise the receiver output will be attenuated. We show that it is possible to satisfy this condition only in a broad sense and the solution in this case is called a quasi-noise-alone reference (QNAR). We present a possible method to achieve a QNAR estimation of the noise power and show by computer simulation the important improvements in the performances of receivers using QNAR AGC circuits in detection systems.

Large signal performance of feedback automatic gain control systems

Feedback automatic gain control (FBAGC) is used to maintain the mean level of one or more signals throughout a signal processing system at a fixed value. The paper is particularly concerned with the application of FBAGC to receiver design and discusses the problem of attempting to suppress large unwanted envelope variations of an incoming signal without distorting any wanted modulation. A simple feedforward model of FBAGC systems predicts their effect on deep sinusoidal variations of the input signal&apos;s envelope. Experimental results confirming the predictions are presented, and a method of determining the parameters of an undefined AGC system given. Finally, the fundamental problems of FBAGC dynamics are discussed, and a technique is suggested for greatly improving them.

An experimental study of technical fluctuations in a quartz crystal oscillator with automatic gain control

The contribution of technical fluctuations of individual circuit components of a quartz crystal oscillator with AGC to the technical characteristics of the output signal is determined. The noise of the elements studied is simulated. It is demonstrated that the AGC system significantly improves the amplitude-frequency characteristics of the oscillator output signal. Requirements are determined for the noise characteristics of individual oscillator stage components for the purpose of obtaining high short-term frequency stability.

Design of an AGC System in a Transistorized VHF Receiver

Various AGC schemes for a transistorized VHF receiver (AM) have been considered. A detailed analysis and design of the AGC scheme by varying the collector load of the VHF and the mixer stage is presented here.