GB839180A - Improvements in or relating to control systems, especially aircraft control systems - Google Patents

Abstract

839,180. Automatic control systems. MINNEAPOLIS-HONEYWELL REGULATOR CO. Oct. 17, 1958 [Oct. 17, 1957], No. 33300/58. Class 38 (4). In a system for automatically controlling a variable in which two independent devices produce signals dependent on the magnitude of the variable, combinations of the two signals are applied to two separate channels, the output of one channel being utilized to correct the variable while the outputs of the two channels are compared to detect any malfunctioning of the system. As shown, D.C. signals from potentiometer pick-offs 43, 82 associated with identical linear accelerometers 41, 87 responsive to acceleration of an aircraft along its pitch axis are applied through resistances 101, 102 and a lag network 110 to a modulator 40 in which they are combined with a signal from a rate gyro 50. The A.C. output of modulator 40 is applied to an electronic amplifier 30 and, if a manual switch 153 has been operated to energize a self-holding relay 21, relays of amplifier 30 control a reversible D.C. servomotor 15 operating the rudder 11 to automatically stabilize the aircraft about its yaw axis. Servomotor 15 also operates a potentiometer 54 to apply positional feedback signals to modulator 40. The signals from the two accelerometers are also applied through resistances 104, 105 and a lag network 120 and combined with the signal from rate gyro 50 to control a second similar servosystem in which a servomotor 71 only operates a positional feedback potentiometer 73. The signals from the two feedback potentiometers 54, 73 are compared in a modulator and amplifier 140 so that any difference, due to malfunctioning of the system, is effective to energize a relay 131 and thereby release relay 21. In consequence the input is disconnected from servomotor 15 and an electromagnetic clutch 16 between the servomotor and the rudder disengaged. A second modulator and amplifier 146 comparing the signals from potentiometers 54, 73 and controlling a relay 135 is provided for reliability. If each pair of resistances 101, 102 and 104, 105 are unequal in inverse ratios, failure of one or other of the accelerometers is effective to disengage the automatic pilot but if all the resistances are equal the effect of such a failure is minimized by the lag networks and the automatic pilot may be disengaged by manual operation of a switch 166.