GB612307A - Improvements in or relating to control systems - Google Patents

Abstract

612,307. Automatic control systems for gyroscopes. SPERRY GYROSCOPE CO., Inc. Sept. 29, 1944, No. 18689. Convention date, May 29, 1943. [Class 38 (iv)] [Also in Group XX] Alignment.-In a closed sequence control system for a variable, an A.C. signal in response to error starts an oscillator, the output of which controls servo-means effecting correction. In Fig. 1, a three-legged flux valve 1, pendulously supported (Fig. 2, not shown) on a craft, has exciting coils 2, energized from an alternating current source 5, and output coils 3 giving a voltage dependent on their position relative to the earth's field. The output from coils 3 is applied to the three-winding stator 6 of a remote Selsyn type unit, the rotor 8 of which is fixed to the vertical gimbal ring of a directional gyro (Fig. 2, not shown). The arrangement is such that the field produced by the stator 6 is fixed in space despite movement of the craft in azimuth and, provided the vertical ring of the gyro also remains fixed in space, no voltage is induced in rotor 8. Wander of the gyro, however, displaces rotor 8 relative to the stator field and a voltage proportional to the displacement is induced in rotor 8, its frequency being that of source 5 and its phase being dependent on the sense of the displacement. Rotor 8 forms with a condenser 9 a tuned circuit, the voltage across which is applied to the grid circuit of a pentode oscillator valve 11 which oscillates at half the frequency of source 5 whenever the rotor voltage is above a value corresponding to a small displacement of the gyro. The output from the oscillator when oscillating is independent of the voltage, but dependent on the phase of the rotor output and is amplified by a triode valve 22 and applied to a phase-sensitive double-diode valve 26, the anode currents of which, derived from source 5, selectively operate a two-way relay 28 according to the phase of the rotor voltage to energize an electromagnet 38 precessing the gyro in the appropriate sense for correction. In a modification, Figs. 3-5 (not shown), a single-legged flux valve is pendulously supported by the vertical ring of the gyro and the Selsyn type transmission dispensed with. Any suitable D.C. amplifier and torque motor may be substituted for relay 28 and electromagnet 38 respectively. If a two-phase torque motor is employed to precess the gyro, one phase may be controlled and the other supplied from a constant source such as source 5. Application of the invention to preventing wander of a gyro relative to a vertical reference is referred to. Specifications 600,189 and 604,907, [both in Group XXXVI], are referred to.