Patent GB-1225074-A (GB)
Title: Improvements relating to gyroscopes
Inventor: BROOKS WILLIAM NEWCOMBE JUNIOR
IPC: G01C19/36
Filed: 1969-10-13
Abstract: 1,225,074. 074. Gyroscopic apparatus. SPERRY RAND CORP. Oct.13, 1969 [Cct.24, 1968], No. 50153/69. Heading G1C. A method of correction for the tendency of a directional gyroscope to process in azimuth during banked turns of an aircraft in which is mounted due to friction at the vertical trunnions of the gyroscope caused by friction in the bearings and due to slip ring contacts comprises deriving asignalrepresenting the bank angle of the aircaft, e. g. from a gyro-vertical, and deriving from this a compensational signal representing the torques tending to effect the precession, the compensation signalbeing applied to a torque motor on the gyroscope to oppose the precession. The gyro 10 shown in the figure comprises a rotor 11 mounted in a case 12 for spinning about a normally horizontal axis 13. The case is journalled in a vertical ring 14 for rotation about an axis 15, the ring being carried in a fixed housing for rotation about an axis 18. A liquid level 19 with associated electrodes is mounted in a plate 20 rotatable about the axis 15 with the case 12, and together with a torque motor 21 maintains the spin axis 13 horizontal. In the described embodiment a directional reference is imposed on the gyroscope by a flux valve 25 whose signal is compared with that from a synchro 27 and fed to a torque motor to process the spin axis 13 about the vertical axis 18 to a desired orientation parallel to earth's magnetic field. The electrical supply to the gyro components is effected through a slip ring assembly 35 which together with the vertical journal bearings 16, 17 of the ring 14 produce an error torque during banked turns, especially after extended turns in the same direction. Since the vertical ring 14 tilts with the aircraft, the precession of the spin axis 13 will no longer be in a horizontal plane and this results in an azimuth component giving a turn error which remains after the aircraft resumes level flight. A vertical gyro 40 having a roll signal generator provides a bank angle signal. This signal is applied to an amplifier 43 controlling a relay 44 which operates when a very low voltage exists at the output of the amplifier 43. The relay controls switches 45, 46 serving to break the contacts between the level 19 and torque motor 21 and to substitute the compensation signal therefor. For small bank angles the azimuthal error will be negligible, so that the compensation signal is not applied to the torque motor 21 until the bank angle exceeds a set value, say 6 degrees. To this end a signal level detector is coupled to the synchro 41 of the vertical gyro 40, and when the detected angle exceeds 6 degrees it operates a switch 50 to supply power to the amplifier 43. The output of the synchro 41 will have a phase dependent on the direction of bank and the switches 45, 46 are arranged to supply the compensating signal to only one phase 21a, or 21b of the torque motor 21. In the described embodiment the signal level detector 41 also controls a switch 57 which renders ineffective the torque 29 slaving the gyroscope to the flux valve 25 during turns of the aircraft.