GB930695A - Improvements in or relating to gyro-magnetic compass systems - Google Patents

Abstract

930,695. Gyro-magnetic compasses. S. SMITH & SONS (ENGLAND) Ltd. Feb. 23, 1962 [Feb. 24,1961), No. 6796/61. Class 40 (1). A gyro-magnetic compass system for an aircraft has a servo-loop including a gyroscope 1, a course defining device to generate signals representing the aircraft heading relative to a reference direction provided by the gyroscope, a magnetic detector 17 generating a signal representing the aircraft heading relative to the direction of the horizontal component of the earth's magnetic field, means 13 for generating a discrepancy signal representing any difference between the two aircraft heading signals, and means for controlling the course defining device to reduce any discrepancy towards zero, and the system further includes means 25 (Fig. 2) for measuring the vertical component of the earth's field, means 21, 22, 24 for modifying the signal in accordance with the angle of tilt of the detector caused by Coriolis' force and means for combining the modified signal with the signals from the magnetic detector so as to compensate for errors thereof due to tilting by Coriolis' force. Associated with gyro 1 is a synchro transmitter 3 connected to synchro control transformer 7 arranged in a subsidiary seivo loop 10, 11 so that the position of shaft 9, registered at 12, indicates the aircraft heading relative to the gyro reference. Magnetic heading detector 17 is gimbal mounted to normally lie horizontally and feeds to the stator windings of synchro resolver 14 a signal representing the aircraft heading relative to the horizontal component of the earth's field. Shaft 9 positions the rotor of rotor 14 and any discrepancy output is applied to torque motor 2 to precess the gyro and reduce the discrepancy. Alternatively the resolver output may be applied to a motor driving one part of a differential synchro between transmitter 3 and transformer 7. A corrector circuit (Fig. 2) is connected in series with transverse winding 16 of detector 17 and includes, in series with vertical field coil 25, a potentiometer 24 tapped in accordance with the aircraft speed V. Further potentiometer 22 is tapped in accordance with the sine of the latitude A of the aircraft. The angle of tilt of detector 17 caused by Coriolis' force is stated to be proportional to V sin # and the consequent error in output from the magnetic detector is stated to be proportional to the sine of this angle, or since it is small, to the angle itself. The speed and latitude may be set manually or automatically. The speed-setting potentiometer may be a switchable network, rather than continuously variable, and a network of this type, having substantially constant input and output impedance is described (Fig. 3, not shown).