Patent GB-911490-A (GB)
Title: Improvements in or relating to gyroscopes
Inventor: BOWDEN BERTRAM VIVIAN
IPC: G01C19/00
Filed: 1958-03-18
Abstract: 911,490. Gyroscopic apparatus. NATIONAL RESEARCH DEVELOPMENT CORPORATION. March 16, 1959 [March 18, 1958], No. 8692/58. Class 97 (3). [Also in Groups XXXIV and XXXVIII] In a gyroscope which includes a rotor mounted within a gimbal system providing freedom for rotation about each of two mutually perpendicular axes, the rotor comprises two concentrated masses m, m 1  mounted at opposite ends of a diameter perpendicular to the axle of the rotor and the rotor axle is journalled in one of the gimbal rings by bearings which permit a limited amount of displacement of the axle relative to the gimbal ring in directions perpendicular to the rotor axis. An alternating current signal representative of such displacements is derived and compared in frequency and phase relationship with a reference alternating current having a frequency and phase which is directly and continuously related to the rotation of the rotor. The rotor which is mounted within the gimbal rings 27, 28, Fig. 4, is shown diagrammatically to provide capacitances a, b, c, d, between fixed plates 11a, 11b, 12a, 12b, provided near the ends of the rotor axle 10. A radio-frequency source of alternating current 14 is connected in circuit with capacitances b, c, and load impedance 15 so that a signal appears across the latter which is applied to a demodulator-filter 18 which selects current at the frequency 2#, where Q is the angular velocity of the rotor axle 10, and applies it to amplifier 19 and two similar phase-sensitive rectifier circuits 20, 21. Reference alternating currents of frequency 2# from sources 22, 23 are supplied to the circuits 20, 21 and the outputs employed to drive the servo systems 24, 25. The sources 22, 23 are closely connected with the rotor, one method being to provide the rotor axle with two spaced bands of alternate reflecting and non-reflecting zones, each band comprising two 90-degree reflecting segments in diametrically opposed relationship with intervening 90-degree non-reflecting segments and with the segments of one band displaced circumferentially by 45 degrees with respect to those of the other band. Light is directed on to each band and therefrom on to photo-electric cells so that the latter provides two alternating voltages whose frequency is 2# and which are 90 degrees out of phase with one another. Similarly current from a second source 16, of frequency different from that of source 14, may be in circuit with capacitances a, d and load impedance 17 to provide a second output which after demodulation and filtering is used as a second input to a subsequent amplifying and phase detecting arrangement which together with the output from the demodulator-filter 18 operates in push-pull. The capacitances a, b, c, d may be formed between fixed plates and the rotor axle 10 or between fixed plates and a sleeve 30, Fig. 7, which is so held by springs that it may float to follow the lateral movement of the rotor axle but is non-rotatable. In a suitable demodulator-filter, the radio-frequency input signal is applied to the floating sleeves 30 at opposite ends of the rotor axle and thence through the capacitances a, c, to the windings P1, P4 which are each connected to one stator plate of differential condensers DC1, DC2, and also through the capacitances b, d, to the similar windings P2, P3 connected to the other stator plates of the differential condensers. The windings P1, P2, P3, P4 are the primary windings of transformers whose secondary windings S1 S2 are tuned by condensers C1, C2 to the frequency of the input signal. The output voltages are rectified by diodes D1, D2 and fed to potentiometer network R5, R6. The outof-balance potential is applied through filter network FN to amplifier 19 and the phase-sensitive rectifier circuits 20. By adjusting condensers DC1, DC2 the output voltages developed across the secondary windings of the transformers can be made independent of any signal produced by unbalance of the gyroscope rotor. The bearings for the rotor axle may comprise a ball race 50, Fig. 11, supported within a housing by springs 52. The springs may be tuned to provide resonance at frequency 2#. Alternatively gas bearings may be used. The rotor may comprise sheet metal shells 43, 44, Fig. 12, defining a hollow chamber 42 containing two diametrically opposed weights 40, 41, the shells being secured to a hollow sleeve 61 which rotates about an axle pin 64. Compressed air flows from pin 64 through ports 68 and past flow-directing blades 69 on to blades 63 which cause rotation of the rotor. The air then forms the bearings at each end of the sleeve 61.