GB1425092A - Gyroscope devices - Google Patents

Abstract

1425092 Gyroscopic apparatus GYROSYSTEMS Inc 31 Jan 1973 4941/73 Heading G1C A gyroscope device, in particular, a gyroscopic compass, comprises a gyroscope 20 mounted within a housing 19 on a two gimbal system, and means which defines a reference spin axis which is fixed relative to the housing 19, wherein the reference spin axis and the rotor spin axis are, in use, maintained coaxial or substantially parallel. The means defining the reference spin axis comprises an inertia flywheel 21 mounted on a shaft 22 which is driven by a motor 52, the gyro rotor 20 also being coupled thereto but via a universal joint 23. The inertia flywheel 21 thus provides a reference axis which is maintained stable under minor dynamic disturbances of the base or deck 14 thereby isolating the rotor 20 from the base 14. In the described embodiment, magneto resistive pick-offs 24, 25 are situated adjacent a magnet 30 carried by the rotor 20 and sense relative movement between the rotor 20 and housing 19. The resultant signals are applied to torquing motors 39, 38 mounted on frames 40, 13 so as to apply a torque to the housing 19 about shafts 15, 16 and 11, 12 respectively. The inertia flywheel, therefore, precesses so as to cause the housing 19 to follow any movement of the rotor spin axis and thereby reducing the output from pick-offs 24, 25 to zero. The initial tilting of a horizontally rotated rotor which results when the rotor 20 is not along a meridian thus causes similar tilting of the housing 19 which is detected by a pendulum 17. The output from a pendulum pickoff 17a energizes a torquing coil 26 to cause the rotor 20 to precess to the meridian, a small portion of the output from pick-up 17a, via voltage divider 28, energizing a second torquing coil 27 which causes the rotor 20 to precess in a horizontal plane thereby effecting vertical damping of the rotor 20. In order to ensure that the rotor 20 precesses toward the meridian, the torques must be applied in the vertical and horizontal axes. Any tilting of the support member 14 is, therefore, sensed by a second pendulus device 18 which applies a correction to the signals from pick-off 17a before being applied to the torquer coils 26, 27, so that the axes of effective application of the torques are rotated out of the tilted axes and into the true horizontal and vertical. The elimination of various errors is described. Intercardinal rolling error is eliminated by selecting the time constant of the pendulum 17 to be significantly longer than the reciprocal of the natural frequency of the ships roll motion. Error caused by acceleration in the north-south direction is minimized by choosing a rate of application of torquing effect due to the pendulum 17 which is as small as possible consistent with allowing the compass to settle in a reasonable time period. Velocity in the north-south direction requires a correcting voltage to be applied to torquing coils 27 proportional to V/R where V is velocity north and R is the radius of the earth.