Compensation Signals

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