GB1262711A - Optimising controller for process plants - Google Patents

Abstract

1,262,711. Optimising control. FOXBOROYOXALL Ltd. April 9, 1970 [Jan. 23, 1969], No.3975/69. Heading G3R. In a system for automatically maximising or minimising a process variable, a step change is made in the value of a controlling variable and, after a delay, the new magnitude of a controlled variable is stored and compared with its previous value so that the controlling variable is correctively adjusted in dependence on the difference, the step change being removed or retained as appropriate before the next control sequence. In atransistorized control system, Fig. 1, a multivibrator 6 periodically controls a logic circuit 5 so that an adjustable step signal is applied through a lead 14 to a control unit 9 to produce a step change in a variable MV controlling a process P. After an interval sufficient for the change to become effective, logic circuit 5 operates switches in a measuring unit 2 so that the value of a dependent process variable CV, filtered and capacitively stored at 2, is compared with its previous value similarly stored. The difference, stored at 3, is applied to control unit 9 to change the controlling variable by acorresponding amount in a corresponding sense. A discriminator 4 determines whether the difference exceeds a predetermined adjustable value, in such sense as to approach the maximum or minimum value desired and, if so, prevents, through a line 17 or 18, removal of the step change until the improvement is insufficient or negative. The step change is finally applied and removed alternately to maintain the system oscillating about the maximum or minimum. Detailed circuits which include manually adjustable controls are described.