Patent GB-503317-A (GB)
Title: Improvements relating to automatic steering systems for aircraft
IPC: G01C19/00
Filed: 1937-07-03
Abstract: 503,317. Automatic control systems. SPERRY GYROSCOPE CO., Ltd., NISBET, R. H., and HARDING, W..G. July 3, 1937, Nos. 18569 and 20443. [Class 38 (iv)] Steering.-In an automatic steering system the rudder is controlled from a direction-giving instrument and is additionally controlled in accordance with the indications of a drift detector this additional control being applied so slowly that it effects only slight correction of heading during a period of the order of the time of correction for yaw or like deviation of the craft. In one arrangement, Fig. 1, a directional gyroscope or gyro-magnetic compass controls the steering through a semicircular cut-off plate 1 co-operating with a follow up member 2 movement of the rudder 18 in accordance with movements of the plate 1 being effected through the hydro-pneumatic arrangement shown, which is of the type described in Specification 416,813, [Group XXXIII]. The drift detector comprises a wireless directionfinder having a vertical antenna 26 and a direction finding loop 25 the latter being attached to the casing of a directional instrument 30 and stabilized in azimuth. A receiver 27 is fed from 25, 26 and supplies a " right-left indicator " 28 and an electric servo-motor 36 which when energized produces a very slow movement of the follow-up member 2 through high ratio reduction gearing 38 and worm-wheel 24. The voltage applied to motor 36 is opposed by a " repeat-back " voltage obtained as shown from a potentiometer 37 so that the correction produced by 36 is proportional to the drift indication. In another arrangement, Fig. 2, a single direction giving instrument controlling the cut-off plate 1 stabilizes the loop 25<1> in azimuth through motor 41 and controls the rudder 118 through the gearing and hydropneumatic arrangement shown. The steering is controlled in accordance with the indications of the drift detector through differential 121 and, in addition to control by a motor 36<1> provided with a "repeat-back" arrangement as described above, further control is provided from the receiver 27<1> of the drift detector by an electric motor 47 energised from 27<1>, The motor 47 is not provided with a " repeatback " arrangement and provides a correction proportional to the integral of drift. It may be replaced by a reversible air-turbine. The loop 25 or 251 may be mounted 'fixedly on the craft the drift correction being effected in accordance with the output of the receiver to which has been added a further voltage derived from a pick-off on the directional instrument. The arrangement of Fig. 1 may have the loop 25 fixed and a second potentiometer similar to 37, with its pick off voltage inserted in series with motor 36, controlled in accordance with movement of member 2. Alternatively the loop may be provided with a system maintaining it in a fixed direction relative to the transmitting station. Specification 377,262, [Group XX], is referred to. The second Provisional Specification describes an arrangement comprising a directional gyroscope with two pick-off devices the rudder being operated from one device and the other device being maintained in alignment with the gyroscope by a servo-motor which is used to stabilize the direction finding loop. The output of the receiver may be altered by a manually controlled potentiometer as the craft approaches its objective. The control term proportional to drift may be obtained from a tachometer device, e.g. a special fluid pump, driven by a motor energized from the receiver. A mechanical rack and pinion arrangement driven in accordance with the drift and with the integral of drift and producing a correcting effect proportional to the sum of those values is also described.