Patent GB-930505-A (GB)
Title: Improvements in or relating to automatic control apparatus, especially for aircraft
IPC: G05D1/06
Filed: 1959-06-25
Abstract: 930,505. Automatic steering control. MINNEAPOLIS-HONEYWELL REGULATOR CO. June 25, 1959 [June 25, 1958], No. 21850/59. Class 38 (4). In a system, e.g. for causing an aircraft to follow a beam, in which a first controlling variable is automatically corrected, a second controlling variable is automatically substituted for the first if the rate of change of the first variable exceeds a predetermined value. As shown, an aircraft automatic pilot 134 normally controls the rudder, ailerons and elevators to stabilize the aircraft in azimuth, bank and pitch. A gyro-vertical 140 of the automatic pilot also controls, through an amplifier 177, a reversible A.C. servomotor 193 provided with positional follow-up from a signal generator 190 so that a further signal generator 200 driven by the servomotor gives a D.C. output signal, proportional to the angle of bank, which is zero when the aircraft is level. Radio range control.-When it is desired to follow a course determined by an Omnidirectional Radio Range, the aircraft is set manually to approximately the desired course, a radio receiver 145 set to the correct frequency and radial, and a self-holding relay 22 energized by manual operation of a knob 16. The consequent energization of a relay 30 causes the input of amplifier 177 to be transferred from gyrovertical 140 to the amplified D.C. output of radio receiver 145 which has a rate component added by a network 160. The operation of relay 30 also applies the D.C. output of generator 200, which is then proportional to displacement from course, to the automatic pilot 134, so that the aircraft is caused to approach the beam by control of the rudder and ailerons. A thermally actuated switch 65, which operates after a delay sufficient to allow substantial course correction, energizes a relay 34 so that a condenser 204 is connected in the follow-up circuit of servomotor 193 to introduce an integral component of control into the final correction. The operation of relay 30 also applies the output of radio receiver 145 through a condenser 237 to control a follow-up servomotor 222 which positions a contact 95 in accordance with rate of change of the radio signals. When this rate of change exceeds a predetermined value, indicating that the aircraft is over the zone of confusion near the radio transmitter, engagement of a fixed contact 97 or 100 by contact 95 controls a Zener diode 126 and a transistor 130 to cause energization of a relay 37 and hence a relay 33. Relay 30 is thereupon de-energized to transfer control of servomotor 193 from radio receiver 145 to gyro vertical 140 and disconnect signal generator 200 from the automatic pilot. Control of servomotor 222 by rate of change of the radio signals persists until the zone of confusion is passed, a condenser-resistance network 128 maintaining relay 37 energized despite short term variations in the position of contact 95. After the zone of confusion is passed, however, relay 37 is de-energized and radio control of the automatic pilot is restored. Switch 13 may be opened manually at any time to disengage radio control. Instrument Landing System.-Towards the end of flight a switch 25 is closed to energize a relay 31 and thereby de-energize relay 22 to disengage Radio Range control. Radio receiver 145 is then retuned to the localiser frequency and a further radio receiver 146 tuned to the glide path frequency of an Instrument Landing System. Relay 31 connects the amplified D.C. output of glide path receiver 146, which has a rate component added by a network 206, to control servomotor 222 so that a D.C. signal is produced by a generator 224 proportional to the displacement from the glide path. Contact 95 is initially driven into engagement with contact 97 to energize a self-holding relay 36. Relay 22 is operated manually to introduce glide path control and stays in, provided a delayed relay 32 has had time to operate. Relay 30 is thus energized to cause the output of radio receiver 145, which is now proportional to displacement from the localises beam, to control the automatic pilot 134 so that the aircraft is maintained on its correct course, an integral component of control being introduced after operation of delay switch 65 as with Radio Range control. Relay 31 modifies network 160 to reduce the rate component under these conditions. As the aircraft steered manually towards the centre of the glide path contact 95 approaches contact 94 until, when contact is made, a relay 35 is energized to apply the output of generator 224 to the automatic pilot so that the aircraft is caused to follow the glide path by controlling the elevators. Under these conditions gain is reduced in the radio azimuth control system by the changeover of tappings on a potentiometer 165.