GB1301696A - - Google Patents

Abstract

1301696 Automatic control systems WERKZEUGMASCHINENKOMBINAT "FRITZ HECKERT" 23 Feb 1970 8583/70 Heading G3R In a closed loop automatic control system for a variable, the desired value is set by adjusting a signal which is fed back in dependence upon the measured value of the variable and compared with a fixed reference, so that the change in gain in the feedback path compensates for the change in gain of the forward path with change in the magnitude of the variable. Thus the feedback stage comprises an amplifier in parallel with a series chain of resistors which are switchable so as to provide a feedback amplification which is inversely proportional to the desired value, a comparator stage being arranged to establish a difference between the output of the feedback stage and a constant magnitude supplied to another input of the comparator. In Fig.2 an output signal Y of a control amplifier F R is supplied to a controlled system F S and signals X therefrom, dependent upon the magnitude of a variable to be maintained at a desired value, are fed back through an amplifier R to one input of a comparator D. Therein the feedback actual value signal, related to the desired value, is compared with a constant magnitude equal to one unit e.g. 1 Volt. The relation of the actual value to the desired value is achieved in that the amplification of the feedback stage is determined by selecting appropriate by-pass resistors for amplifier R, and is inversely proportional to the desired value. When the desired value and actual value coincide a control deviation of zero exists at the input of the control amplifier F R .