Sperry Marine NAVIGAT 100, Руководство по эксплуатации, установке и обслуживанию

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NAVIGAT 100 056373/D
Operating Principle 1-9
1.4 Operating Principle
The north-seeking element used in the NAVIGAT 100 system is the gyro-
sphere, a hermetically sealed unit with a funnel-shaped recess, reaching
from the outer skin down to its centre.
Inside the gyrosphere, two mechanically linked gyroscopes are
mounted with their spin axes horizontal in a carrying frame. The gyro-
scopes are allowed to turn around the vertical, but torsion bands effect a
defined rest position, while a mechanical linkage ensures that the result-
ant spin vector of the gyros remains stationary relative to the gyro-
sphere. This twin gyro arrangement eliminates intercardinal roll error.
Once the gyros have run up to speed, their resultant spin vector, and
with it the gyrosphere, settles in the direction of true North.
Figure 1-8:
Gyrosphere
The top of the gyrosphere contains an annular damping trough, half
filled with a viscous fluid. The fluid damps azimuthal oscillations of the
gyroscope system. The oscillation period is tuned to the Schuler period
of 84.4 minutes, so that heading errors during horizontal acceleration
due to changes in speed and/or direction are prevented.
The gyrosphere floats in a supporting fluid inside the gyrosphere con-
tainer. Because the buoyancy of the gyrosphere is a little greater than its
weight, a bearing cup at the bottom of the recess is pressed against the
centering pin and keeps the gyrosphere exactly centered in the con-
tainer.
In order to make the gyroscope system pendulous, that is, to provide the
gravity controlling moment, the gyrosphere is designed so that its cen-
tre of gravity lies slightly below the centre of buoyancy.
The gyroscopes are in fact squirrel-cage induction motors, which attain
a speed of nearly 20000 rpm at a voltage of 100 VAC @ 333 Hz.
In the Mod. 10/4 and Mod. 10/3 container, their supply power is applied
through the electrolytically conducting supporting fluid, via the top and
bottom contacts.
A follow-up control circuit keeps the container aligned with the gyro-
sphere at all times, thus heading can be derived from the container’s ori-
entation.
The gyrosphere container Mod. 10/4 and Mod. 10/3 systems employ
optical pick offs to provide the follow-up control signal.
centering pin
N gyro
gyro linkage
damping trough
S gyro
gyrosphere shell