Patent GB-900933-A (GB)
Title: Improvements relating to gyro magnetic compass systems
Inventor: BISHOP ROGER IVAN
IPC: G01C19/36
Filed: 1959-12-08
Abstract: 900,933. Measuring electrically. SMITH & SONS (ENGLAND) Ltd., S. Nov. 23, 1960 [Dec. 8, 1959], No. 41771/59. Class 40 (1). [Also in Group XX] In a gyroscope system in which an indicator attached to the shaft of a resolver is positioned by a gyroscope via a servo link and in which the stator of the resolver is fed with a signal from a magnetic compass and in which the output of the resolver is employed to precess the gyro until the indicator is correctly aligned with the magnetic compass heading, the gyro may be switched out of the loop and the indicator aligned, via a differential synchro, directly to the magnetic compass heading. In addition, the servo loop may be broken to allow the indicator to be driven direct from the gyro with no correction from the magnetic compass but with provision, via a differential synchro, to drive the indicator at a slow rate in order to compensate for the effects of the earth's rotation, and also provided with means whereby the operator may adjust the indicator relative to the gyro in order to set the course required. In the gyromagnetic compass system of the Figure, indicator 7, and hence the rotor of resolver 5, is positioned in accordance with the heading of gyro 12 by motor 22 controlled by the synchro link comprising synchro transmitter 13, synchro receiver 20 and differential synchro 15. The stator windings of resolver 5 are fed from the magnetic compass 1 and the resolver rotor signal is therefore dependent on the misalignment between the setting of indicator 7 and the aircraft heading as derived by the magnetic compass. This signal is fed via amplifier 9 to precession motor 10 to precess the gyro to reduce the misalignment to zero. Operation of button 19 closes the sync. contact and the misalignment signal from the resolver is fed direct to motor 17 which drives the stator of differential selsyn 15 to align the indicator directly to the magnetic compass heading without the intervention of the gyroscope. The system may be converted to function as a straight directional gyro by operation of switch 23. In any position of this switch other than that of " compass " as shown, relay DG is operated by switch contact 24, contacts DG1 open to break the feed-back loop between the resolver 5 and the gyro 12, contacts DG3 close and connect the output of potentiometer 26 to amplifier 27 which energizes motor 28 to drive the rotor of differential selsyn 15 at a slow rate, determined by the setting of potentiometer 26, to compensate for the effects of the earth's rotation, the rate of rotation of motor 28 being stabilized by applying feed-back from the tachometer generator 29, driven by motor 28, to a second input to amplifier 27. In the position of switch 23 labelled DG the input of motor 17 is earthed, the positions S and F either side of this position give, from transformer winding 30, various degrees of energization of motor 17 in one direction or the other, in order that the indicator may be reset by driving the stator of the differential synchro in the appropriate direction at a fast or slow rate, as desired by the operator.