GB1061902A - Improvements in or relating to automatic control apparatus - Google Patents

Abstract

1,061,902. Automatic control. NORTH AMERICAN AVIATION Inc. Oct. 11, 1963 [Oct. 5, 1962], No. 37853/62. Heading G3R. In a system in which a variable dependent on an independent variable is automatically adjusted towards a value at which its rate of change with respect to the independent variable is zero, adjustment is terminated when the difference between successive values of the dependent value falls below a predetermined value, and restarted when a function of the two variables changes by a predetermined amount. As described, material is supplied to a reaction vessel at a constant rate and the heat input (an independent variable) is automatically varied until the output yield (a dependent variable) is approximately a maximum. Thereafter, control ceases and the ratio between the two variables is monitored. Should this ratio deviate by more than a predetermined amount, control to achieve maximum yield is resumed. A detailed embodiment involving flip-flop circuits and transistors and utilizing an electrical circuit to simulate a controlled system is described. In this embodiment the dependent variable varies the repetition frequency and the pulse width of an integrating type pulse generator. A timing circuit causes the pulse generator periodically to gate, from an independent source, a number of pulses which is inversely proportional to the magnitude of the dependent variable. Each number so obtained is compared by a forward/backward counter with the previous number which is reproduced by a delay circuit. Any difference above a predetermined magnitude causes operation of a reversible servomotor to adjust the independent variable in such sense that the dependent variable moves nearer to an optimum value. Periodic comparison between counts and delayed counts continues until the difference becomes less than the predetermined magnitude whereupon control of the independent variable ceases. The independent variable is then caused to vary pulse width instead of the dependent variable and the comparison between counts and delayed counts indicates variations in the ratio of the two variables. If this ratio deviates by more than a predetermined extent operation of the system to achieve an optimum is resumed.