Patent GB-647723-A (GB)
Title: Improvements in or relating to stable reference apparatus
IPC: G01P9/04
Filed: 1947-08-01
Abstract: 647,723. Electric automatic control systems. SPERRY GYROSCOPE CO., Inc. Aug. 1, 1947, Nos. 21027 and 21028. Convention dates, Aug. 2, 1946. [Class 38 (iv)] [Also in Groups XX, XXXVI and XXXVIII] In stable reference apparatus of the kind in which a stretched wire is maintained in vibration at its natural frequency in a direction perpendicular to a magnetic field, the field may be maintained horizontal by a system of barmagnets in a gravity-controlled casing, and a plurality of such devices may be mounted on a Cordan-suspended frame to detect and correct rotation about each axis. The bar-magnets 31, 33, 35, 37 (Fig. 3), are mounted in a rotatable assembly, and maintained horizontal by two weights 51, 53 (Fig. 2). The vibration of the wire 19 takes place in the field of a pair of coils 57, 59 supplied by a high-frequency generator 61 (Fig. 1) and any difference between the axis of the coils and the plane of vibration of the wire produces an induced current in the wire at the high frequency modulated at the frequency of vibration, and is used to drive a servomotor 87 to restore the normal direction of the axis of the coils. Universal stabilization system.-Three mutually perpendicular vibrating-wire sensitive devices 211, 213, 215 (Fig. 6), may be mounted in a frame 217 for universal suspension through Cordan elements 219, 221 for freedom of movement about three mutually perpendicular axes, and each operates servo-gear for correcting for rotation about its axis. The two horizontal elements 211, 213 are as described above, and the vertical element 215 is similar, except that the horizontal component of the earth's magnetic field is used instead of that from a barmagnet system. Positional data transmitters 229, 231, 233 are provided for supplying control signal data to an auto-pilot or similar device. The vertical element 215 and its associated frame are controlled as described in Specification 639,577, [Group XX]. The horizontal elements 211, 213 are coupled to the input and output circuits of amplifiers 329, 330 which thereby oscillate when the strand is vibrating, to feed back energy into the strand, thus sustaining vibrations in a plane perpendicular to the axis of the magnet. Additional apparatus is provided for obtaining a voltage from a phase-sensitive amplifier 359, 360 of polarity and magnitude depending on the relationship of the plane of vibrations of the strands and the axis of HF coils round the envelope. This voltage is mixed with a 400-cycle voltage from a generator 363 in modulator 361, 362 to be fed through a resolver 234, adjusted by the vertical frame, to motors 223, 225. The resolver determines which modulator feeds which motor. As shown in Fig. 6, modulator 361 from element 211 feeds motor 223, which operates to restore frame 219 to vertical, and modulator 362 from element 213 feeds motor 225 which operates to restore frame 217 to vertical. With a 90 degree change in orientation between frames 217, 219 the resolver reverses the inter-coupling between modulators 361, 362 and motors 223, 225 and with intermediate changes in orientation each motor is controlled partly by each sensitive device, the relative extent depending on the angles between the axes of the devices and the motors. Each of the sensitive devices 211, 213, 215 may be rotated round its own axis for initial adjustment, and locked by a thumbscrew. Specifications 600,165, [Group XXXVI], 601,051, 610,530, 646,794 and 647,895, [all in Group XX), also are referred to.