Patent GB-1097682-A (GB)
Title: Monitored rate gyroscope system
Inventor: HODSON ANTHONY EDWARD
IPC: G01C19/42
Filed: 1964-03-31
Abstract: 1,097,682. Gyroscopic apparatus; measuring faults electrically. ELLIOTT BROS. (LONDON) Ltd. March 31, 1965 [March 31, 1964; Oct.15, 1964], Nos. 13219/64 and 42049/64. Headings G1C and G1N. A rate gyroscope system includes electrical means for monitoring the movement of the rotor and for providing a warning of any departure from predetermined operational conditions. The rotor 11 is carried by a gimbal supported on a shaft 15 which is rotatable in bearings carried by supports 16, and in normal use rotation of the system about the axis 19 causes precession about the axis 18 of the shaft 15. The gimbal includes a rigid arm 23 carrying a magnetic shoe 24 which moves relative to an E-shaped magnetic core 27 when the rotor precesses and causes a change in the alternating current through windings 28. This change in current is demodulated in a phase sensitive demodulator 29, and the signal from the demodulator is amplified at 33 and fed over a line 34 to a winding 31 supported in a pot magnet 32 by an arm 30 rigid with the gimbal. The current in this winding causes a restoring torque the magnitude of which is directly proportional to the rate of rotation of the system about the axis 19. A second winding 31 provides a velocity feedback to the amplifier 33 over line 36. The accuracy of the system depends on the restoring torque remaining constant for a given rate of rotation of the system, and this will be affected by a variation in the speed or direction of rotation of the rotor, a failure in any of the components 28, 29, 31 or 33 which could allow the rotor to precess by an excessive amount, or the development of a high frictional resistance in the bearings carrying the gimbal shaft 15. The invention provides means for detecting any of these faults. Monitoring rotor movement. Two thin permanent magnets 37 are mounted side by side in contact on the periphery of the rotor, the north pole of one magnet being adjacent the south pole of the other. A magnetic pick-off 38 is disposed close to the rotor, the core 39 having a very small gap 41 which, in the null position of the rotor, is in line with the junction of the magnets 37. As the rotor rotates the two pairs of magnetic poles of the magnets 37 induce pairs of pulses in the pickoff winding 40, the pulses of each pair being in opposite directions. The frequency of these pairs of pulses is directly proportional to the speed of the rotor, and their amplitude, which falls away rapidly as the junction of the magnets 37 moves out of alignment with the gap 41, gives a measure of the deflection of the rotor from its null position. The pulses are fed to a detector unit 42 which detects any change in the speed of the rotor or any excessive precession and provides a signal to de-energize a relay 44 giving an indication that a fault has developed. The outer surfaces of the magnets 37 are cut away obliquely Fig. 6a (not shown) so that one pair of poles is further from the pick-off 38 than the other. The pulses of each pair are consequently of different amplitude, and the direction of rotation of the rotor is measured by determining whether the larger pulse follows or precedes the smaller. A circuit Fig. 7 (not shown) is described for measuring and reversing the direction of rotation. Monitoring friction at the gimbal bearings. A circuit Figs. 3 and 4 (not shown) includes a multivibrator (52) the output of which is fed through a scaling circuit (55) to the amplifier 33. The amplifier output is fed to the first winding 31 which tends to move the gimbal, and the consequential velocity signal from the second winding is fed to the amplifier where it normally offsets the applied signal so that the output on line 35 is very small. If, however, there is excessive friction at the gimbal bearings the velocity signal is reduced or absent and a signal of large amplitude appears on line 35. This is demodulated at (56) and is used to operate a relay (RL1) giving an indication that a fault has developed.