Patent GB-698534-A (GB)
Title: Control system for craft, particularly aircraft
IPC: G05D1/00
Filed: 1952-01-15
Abstract: 698,534. Automatic steering control systems. BENDIX AVIATION CORPORATION. Jan. 15, 1952 [March 28, 1951], No. 1181/52. Class, 38 (iv). In a system for automatically controlling a craft about an axis, control signals for a servomotor operating a control surface are derived from a generator producing signals dependent on the altitude of the craft about the axis, and a generator producing signals dependent on the position of the control surface, the servomotor is disconnectable from the control surface, and persistent signals produced by the secondmentioned generator are attenuated. As shown, the elevator 109 of an aircraft may be controlled directly by a stick 113 or, upon the operation of a lever 111 a clutch 107 is engaged so that the elevator is controlled by a twophase servomotor 103. Phase winding 119 of servomotor 103 is energized by the output of a combined thermionic and magnetic amplifier, 77 to the input line 73a of which is applied the algebraic sum of the following signals : (a) a signal, from the rotor 27 of an inductive device 25, which is dependent on the pitch attitude of the craft as detected by the output of an inductive pick-off 3 associated with the pitch axis of a gyro vertical 1 ; (b) a signal, from a winding 65 of a transformer 63, which is dependent on altitude as detected by the output of an inductive pick-off 58 associated with an aneroid bellows 51 ; (c) a signal, from a potentiometer 45, produced by an inductive device 31 adjusted by a two-phase servomotor 37 energized simultaneously with servomotor 103 when a switch 101 is closed; (d) a signal from a transformer 75, the source of which is described below. The signal at (d) above is produced by the algebraic addition of the following signals: (e) the combination, from a potentiometer 145, of a signal dependent on the position of the control surface as detected by the output of an inductive device 123 coupled to the control surface, and a signal dependent on the speed of servomotor 103 as detected by the output of winding 127 of a tachometer generator 121 coupled to servomotor 103; (f) a signal, from a potentiometer 143, dependent on the rate of pitch as detected by an inductive pick-off 137 associated with a rate gyro 135; (g) a signal, from a transformer 155 supplied through an amplifier 153, which is dependent on bank of the craft as detected by the output of an inductive device 147 associated with the bank axis of gyro vertical 1 to give the necessary upelevator during turn; (h) a signal, from a winding 163 of transformer 63, which is dependent on altitude as detected by the output of an inductive pick-off 58 associated with an aneroid bellows 51. The signals (e)-(h) above are applied through a potentiometer 169 to a thermionic amplifier and delay circuit 167 incorporating a bridge circuit including a time delay tube in which temperature-variable resistors 185, 187 are associated with heaters 181, 183 in the anode circuits of a double-triode valve 177 so that, after a predetermined delay any signal still applied to circuit 167, and which is therefore persistent or of low frequency, is cancelled by negative feed-back through a transformer 197 so that the signal at (d) above is reduced to zero. Circuit 167 also derives a signal dependent on rate of change of altitude from the signal at (h) above. The gyro vertical is monitored by a pendulum controlling an inductive pick-off 11, the difference between the signal from this pick-off and that from pick-off 3 associated with the pitch axis of the gyro vertical being applied to an amplifier 15, which may include a multivibrator, controlling a two-phase servomotor 19 for erecting the gyro. When the control surface is under servomotor control the gyro vertical thus normally maintains level flight at an altitude determined by aneroid 51. To climb or dive a button (not shown) is pressed to release a stick 29 so that rotor 27 of inductive device 25 may be moved in the appropriate direction. Simultaneously a switch 205 disengages a clutch 53 so that rotor 57 of induction device 58 is centralized by a spring. When the new chosen altitude is reached stick 29 is recentralized and operation of switch 205 reengages clutch 53 so that the aneroid maintains the craft at the new altitude. Operation of switch 69 from the position shown will level the craft during climb or dive by disconnecting inductive devices 25 and 31. When clutch 107 is disengaged by handle 111 a switch 101 is closed so that turns made by the stick 113 are followed by servomotor 37 which produces such a signal across potentiometer 45 that when clutch 107 is re-engaged the craft is maintained in its new coarse without shock. A similar system for controlling the craft about its bank axis is referred to. Specifications 662,853, 679,560, 684,445 are referred to.