GB1095519A - - Google Patents

Abstract

1,095,519. Gyroscopic apparatus. SMITHS INDUSTRIES Ltd. Nov. 4, 1966 [Nov. 8, 1965], No.47342/65. Heading G1C. A rate gyroscope having a rotor 9 carried by a gimbal 1 for precession about an axis 3 against the action of a torsion bar 6, is provided with an arrangement for checking the freedom of the gimbal to precess comprising two annular electromagnets 20, 21 embracing the casing 2 of the gyroscope, each provided with a pair of diametrically opposed poles (not shown), the pair of poles of one electromagnet being angularly displaced about the precession axis 3 with respect to the other pair, the electromagnets being individually energizable to exert a torque on the gimbal structure by way of the rotor spindle 11 which is of steel, the sense of the torque and thus any resultant angular displacement of the gimbal about the axis 3 being dependent on which of the two electromagnets is energized and being detected by the gyroscope pick-off 7, 8. The gimbal 1 and rotor 9 are of non-ferromagnetic material and the rotor is driven by an internal three-phase synchronous hysteresis motor. Each electromagnet comprises an annular ferromagnetic yoke 25 with toroidal windings 26 the two yokes being in axial alignment along the axis 3. The diametrically opposed poles of each electromagnet extend towards the opposite electromagnet are arranged on lines which are equiangularly displaced from the axis perpendicular to the axis 3 and the rotor spin axis 12. Energisation of one or the other electromagnet from a D.C. supply causes precession of the gimbal 1 if this is free to do so and this precession is sensed by the pickoff 7, 8. The D. C. supply for energization of the electromagnets is connected through relay contacts which are only closed if the rotor 9 is rotating at its synchronous speed so that correct operation of the gyroscope can be completely checked. A resistor is included in one of the three phase leads to the rotor motor and this detects amplitude modulation of the A.C. supply which occurs when the rotor is rotating at its synchronous speed. The signal developed across this resistor is compared with the original supply in a demodulator the output of which is amplified and used to energize the relay allowing energization of the electromagnets. Electrical circuitry is given in the Specification.