Patent GB-753700-A (GB)
Title: Turn control for automatic pilot systems
IPC: G05D1/04
Filed: 1954-05-11
Abstract: 753,700. Automatic control systems for aircraft. BENDIX AVIATION CORPORATION. May 11, 1954 [June 5, 1953], No. 13741/54. Class 38 (4). When an aircraft banks, a signal is applied to the elevators to compensate for loss of lift, the signal depending on the magnitude of the bank and increasing with the persistence of the bank. In the embodiment described below, the bank signal developed at 151 is applied over a thermal device 213 to the elevator servomotor 103. As shown, the elevator 109 may be controlled directly by a stick 113 or, upon operation of a lever 111 a clutch 107 is engaged so that the elevator is controlled by a two-phase servomotor 103. Phase winding 119 of servomotor 103 is energized by the output of a combined thermionic and magnetic amplifier 77 whose input is supplied with 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 Y-Y of a gyro-vertical 1; (b) a signal from a potentiometer 45 produced by an inductive device 31 controlled by a twophase servomotor 37 energized simultaneously with servomotor 103 when a switch 101 is closed; (c) a signal from a winding 65 of a transformer 62 which is dependent on altitude as detected by the output of an inductive pickoff 58 associated with an aneroid bellows 51 ; (d) a signal from a potentiometer 68 across a winding of transformer 250 fed from an amplifier 56 fed from the roll pick-off of gyro 1 ; the amplifier 56 receives a signal whose phase depends on the direction of roll and whose magnitude depends on extent of roll; this signal is applied to discriminator 212 feeding a heater 235, thus varying the resistance of resistance 240 to vary the potential of tap 248 and produce a signal in transformer 250 of constant phase and of amplitude depending on extent of roll, and on persistence of bank; adjustment of potentiometers 231, 232 allows the signal in transformer 250 to be higher for a bank in one direction to compensate for the gyroscopic effect of propellers; (e) a signal from transformer 73 derived as described below. The signal at (e) above is produced by the algebraic addition of the following signals:- (f) the combination from potentiometer 145 of a signal dependent on the position of the elevator 109 as detected by the output of an inductive device 123 coupled to the elevator, 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; (g) a signal from potentiometer 143 dependent on the rate of pitch as detected by an inductive pick-off 137 associated with a rate gyro 124; (h) a signal from resistance 159 across a second winding on transformer 250; (i) a signal from a winding 163 of transformer 62. The signals (f)-(h) above are applied through a potentiometer 169 to an amplifier and delay circuit 167 incorporating a bridge circuit including a thermal delay tube 179 in which temperature-variable resistances 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 transformer 197 so that the signal at (e) above is reduced to zero. Circuit 167 also derives a signal dependent on rate of change of altitude from the signal at (i) above. The gyro vertical is monitored by a pendulum 14 controlling an inductive pick-off 11, the difference between the signals from pick-off 11 and pitch pick-off 3 (controlled by the gyro 1) being applied to amplifier 15 controlling a two-phase servomotor 19 for erecting the gyro. When the elevator is under servomotor control, the gyro thus maintains level flight at an altitude determined by aneroid 51. To climb or dive, a button on the control stick 29 is pressed to release stick 29 so that rotor 27 of inductive device may be moved in the appropriate direction; simultaneously a switch 205 disengages clutch 53 so that rotor 57 of induction device 58 is centred by spring. When the new chosen altitude is reached stick 29 is re-centralized and operation of switch re-engages clutch 53 so that the aneroid 51 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 the inductive devices 25, 31 from the input to amplifier 77. When clutch 107 is disengaged by handle 111 a switch 101 is closed so that turns made by the stick 113 are followed by a servomotor 37 which produces such a signal across potentiometer 45 that when clutch 107 is re-engaged the craft is maintained on its new course without shock. Specifications 603,610, [Group XXXVI], 662,853, 663,891, 679,560, 684,445 and 698,534 are referred to.