GB1267754A - Auxiliary systems for the control of regulating members which in normal operation are controlled automatically by a digital computer - Google Patents

Abstract

1,267,754. Automatic control. INSTITUT FRANCAIS DU PETROLE DES CARBURANTS ET LUBRIFIANTS. Dec.24, 1969 [Dec.30, 1968], No.62903/69. Heading G3R. A digital computer which normally supplies the error signal in a closed-loop system controlling a variable also supplies a signal through a memory to a comparator in which it is compared with a signal dependent on the magnitude of the variable so that, if the computer fails, control of the variable continues without shock. In Fig.2, a signal 1, corresponding to the measurement at I n of a variable of a production unit U, is applied to a digital computer C which compares it with a desired value so that any error produced at 2 is effective to control a valve V a and thereby correct the variable. Signal 1 corresponding to the measured variable is also applied at 10 to a comparator R n . While computer C is in control, it also applies, through a memory M n to the other input 14 of comparator R n , such a reference signal that the output of the comparator at 12 is equal to control signal 2. Then, if the computer fails, causing switches K 1 K 3 to change over, the control signal 12 initially applied to valve V n is the same as that previously applied by the computer. Thereafter comparator R n controls the production unit U and the desired value reference signal may be varied manually from the control desk P through line 6. Control desk P also serves for monitoring and controlling the computer C and the production unit U. In a modification (not shown), a plurality of production unit variables are measured and controlled in succession by a multiplex system involving a single computer associated with analogue-digital and digital-analogue converters, smooth changeover to standby comparators being provided for selected variables in the case of computer failure.