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bubble level. Deceleration will cause a displacement in
counteract or compensate for certain effects that would
the opposite direction. As a result, tilt signals will be
otherwise produce azimuth or leveling errors in the
produced even though there is no gyro tilt.
master compass.
Acceleration compensation is obtained for the meridian
These effects may be classified as ship, earth, and
gyro by the north-south acceleration computer and for
constant torque effects. The ship effects include speed,
the slave gyro by the east-west acceleration computer.
course, and acceleration changes. The earth effects are
from horizontal and vertical earth rate. Constant torque
The east-west acceleration computer operates in the
effects are caused by a mechanical unbalance of the
same manner as the north-south acceleration computer. Its
master compass, or any other mechanical defects that
input is east-west speed from the speed component computer,
would cause the compass to settle with a tilt.
and its output is the east-west acceleration compensa-
tion signal to the slave gyro gravity reference system.
Northerly or southerly ship speed produces a gyrocom-
pass error due to gyro tilt as the ship follows the curva-
The effect of vertical earth rate on the meridian gyro
ture of the earth. The rate of this gyro tilt is proportional
is proportional to the product of earth rate at the equator
to the product of ship's speed (S), and the cosine of own
and the sine of the ship's latitude. The effect of horizon-
ship's course (C) and a constant of 0.0166. Easterly
tal earth rate on the slave gyro is proportional to the
speed, however, produces an error equal to the product
product of the earth rate at the equator and the cosine of
of ship's speed (S), and the sine of own ship's course
the ship's latitude. As the effect of vertical earth rate is
(C). Easterly or westerly speed does not cause the merid-
caused by the speed of the earth's rotation about its north-
ian gyro to tilt; however, as the slave gyro is aligned
south axis, a ship traveling in an easterly or westerly
east-west it is affected by easterly or westerly speed in
direction will either add to or subtract from the earth's rota-
the same manner as northerly or southerly speed affects
tion. This apparent change in the speed of the earth's rota-
the meridian gyro. Therefore, speed (any direction)
tion will, in effect, produce a comparable change in
causes tilt of one or both gyro elements. Tilt of the
vertical earth rate. This change, which is the meridian gyro
meridian gyro causes precession away from the merid-
east-west speed error, is proportional to the product of the
ian, causing azimuth, roll, and pitch errors. The tilt of
ship's east-west speed and the tangent of the ship's latitude.
the slave gyro causes only errors in roll and pitch. The
slave gyro tilt signal is not applied to the azimuth servo-
To compensate for these effects on the meridian
loop. The slave gyro vertical ring is positioned by the
gyro, we need a compensating signal voltage
azimuth servo follow-up motor. The slave gyro is made
proportional to the product of earth rate, at the equator
to follow the vertical ring by the slaving control system.
and the sine of the ship's latitude, and a compensating
signal voltage proportional to the product of east-west
The Mk 19 compass is compensated for speed errors
speed and the tangent of the ship's latitude.
by applying a compensation signal (north-south speed
and drift) to the meridian gyro leveling control system,
To compensate the slave gyro for the effect of horizontal
and a signal (east-west speed) to the slave gyro leveling
earth rate, we need a compensating signal voltage propottional
control system. (See fig. 4-27.) Thus, both gyros are main-
to the product of earth rate and the cosine of the ship's
tained in a level position for any speed or course. These
latitude. These compensating signals are obtained from
signals arc obtained from the own ship's speed repeater
the latitude and tangent latitude computers (fig. 4-27).
and speed component computer (shown in fig. 4-27).
If the sensitive elements were perfectly balanced, and
The ship's heading may differ from the true course
there were no other factors that would cause a constant tor-
due to an error caused by the north-south drift of the
que on either of the two gyros, the tilt signals from the elec-
ship. The north-south speed signal is compensated for
trolytic bubble level, over a period of time, would average
drift by a manual corrector located on the front of the
out to zero. This is true because the gyro controls are de-
control cabinet. This drift setting is made by the compass
signed to keep the gyro axles level at all times. As it is not
operator after obtaining the necessary information from
possible to keep the gyros perfectly balanced at all times
because of wear, a constant torque compensation system
the ship's navigator.
is provided for both the meridian and slave gyros.
Changes in the ship's speed will cause compass
If the magnitudes and durations of accelerations are
errors if not compensated. A tilt signal to compensate
for errors from acceleration is produced by the elec-
excessive, during high-speed turns and maneuvers for
example, it is desirable to cut out the tilt signal to the
trolytic bubble level. When the ship accelerates in speed,
integrator. This is accomplished by the north-south
the inertia will displace the electrolyte in the electrolytic
4-23

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