Patent GB-760642-A (GB)
Title: Automatic pilot system
IPC: G05D1/06
Filed: 1954-07-13
Abstract: 760,642. Automatic steering control systems. BENDIX AVIATION CORPORATION. Julv 13, 1954 [July 27, 1953], No. 20476/54. Class 38 (4). In an automatic steering control system the magnitude of one signal controlling steering is varied in dependence on the sum of that signal and one or more other signals also controlling the steering. In Fig. 1 the rudder 13 of an aircraft is automatically .controlled by a servomotor 62 energized from an amplifier 53. The input to amplifier 53 may be a combination of signals from variable inductive devices 36, 55, 16 associated with an earth inductor compass 14, a rate-of-turn gyro 15 and a servomotor 62 respectively. Under these conditions relays (not shown) in a unit 11 couple the output of inductive device 36 to leads 43, 56 and disconnect the D.C. output of a localizer beam radio receiver 10 from the system. When it is desired to track a radio beam a switch 77 is moved manually to operate the above-mentioned relays so that the output of radio receiver 10 is connected to input leads 88, 90, Fig. 2, of a magnetic inverter amplifier 92 so that a signal dependent on the angle between the axis of the radio beam and a line from the aircraft to the transmitter is applied through valves 100, 109 to a resistor 118. This signal is combined with the output of inductive device 36, which under these conditions is connected to leads 124, 125 and applied through a valve 215 to leads 224, 228 connected to leads 43, 56. There is thus an additional signal controlling rudder 13 tending to steer the aircraft toward the axis of the beam. The beam signal applied through a transformer 148 and combined with the signal from inductive device 36 supplies a rectifier 139 to bias a valve 132 so that when the aircraft has approached the axis of the beam to a predetermined extent the bias is reduced and a relay 130 is operated to close a contact 130H and connect an integrating circuit 159 to the system. Integrating circuit 159 employs thermal delay devices 178, 179 having different time constants and develops across resistors 126, 127 correeponding signals which are injected into the grid circuit of valve 215. These signals, the magnitudes of which are dependent on time only, serve to cancel the effect of any signal from inductive device 36 resulting from a craft heading which is not parallel to the beam axis, e.g. due to a cross wind. With relay 130 operated, the combined signal from the secondary of transformer 148 is also applied through contact 130D and valves 246, 253 to control the energization of a resistor 256 heating a grid resistor 111 having a negative temperature coefficient, so that the beam signal developed across resistor 118 is decreased as the aircraft approaches the beam transmitter. Resistor 111 has another heater 267 which is energized with the valve heaters when a preliminary contact 78 of switch 77 is connected. This ensures that the beam signal is small to prevent shock when beam tracking is initiated. The subsequent cooling of resistor 267 when it is disconnected by the relays in unit 11 allows the beam signal to rise to its normal value. In modifications alternative locations and arrangements for temperature variable resistor 111, some involving bridge circuits, are described. Specifications 603,610, 647,961, [both in Group XXXIX], 662,831 and 675,760 are referred to.