GB1360805A - Signal processing - Google Patents

Abstract

1360805 Controlling rolled material thickness SIEMENS AG 23 July 1971 [25 July 1970] 34810/71 Heading G4H Apparatus for controlling the thickness of rolled material by adjusting the roll gap in response to rolling force includes an analogue to digital converter which receives analogue rolling force signals and produces digital control signals when the rolling force is outside a particular range. This range is varied by control of the gain of an amplifier in the converter, the gain control signal being generated by apparatus comprising two sets of threshold devices which respond to positive and negative excursions of the rolling force from a mean and the outputs of which provide a pattern from which the amplifier gain is varied; the direction of the variation depending on the extent of the positive and negative excursions of subsequent portions of the force signal. Load cells 4 produce a voltage proportional to roll force which is fed via summing amplifier 3 to variable gain amplifier 2. The apparatus comprises eight threshold devices, four of which 15,13,11 and 5 respond to voltages of relative magnitude 1, 2À5, 3À4, 3À5 respectively above a mean and the others 16, 14, 12 and 6 respond to like voltages below a mean. The amplified voltage from 2 is fed to threshold circuits 5 and 6 which, if actuated, operate circuit 7 which produces a train of positive circuit 5 or negative circuit 6 pulses which are fed to forward/backward counter 8 and to means for adjusting the roll gap. The counter contents is fed via digital to analogue converter 9 as a negative feedback to amplifier 2. The output of variable gain amplifier 2 is also connected via amplifier 10 to threshold circuits 15, 13 and 11 and directly to threshold circuits 16, 14 and 12. These threshold circuits are connected to evaluating circuit 17 which comprise logic units which serve to increase or decrease the count in counter 40 by one unit for each cycle of the load cell output variation. The counter reading is fed to digital to analogue converter 43 which varies the gain of amplifier 2 in steps of two. The circuit 17 operates so that if for one cycle of the analogue input: (a) all devices 11-16 respond the amplifier gain is decreased, (b) devices 15 and 16 respond but 13 and 14 do not, the amplifier gain is increased, (c) no devices respond, the amplifier gain is increased, (d) more devices in set 11, 13, 15 than in set 12, 14, 16 respond, the amplifier gain is increased. This serves to keep variations due to roll eccentricities in the range between the thresholds of devices 15 and 11 and prevents alteration of the roll gap unless the characteristics of the rolled material change.