Figure 3-22.--Functional diagram of the stabilized platform assembly.

and used to drive the output in a direction to reduce the

Platform Configuration

error.

The stable platform consists of a flat top plate to

Assuming the input and output pots are initially

which the GSI is affixed. The top plate is attached to the

equal, then the difference in voltage is zero and there

base plate through a universal joint and a center post and

is no error. If the input command pot is moved, then

is moved by two hydraulic actuators that are coupled to

an error is generated. The amplifier amplifies the error

the top plate with two axis rod ends. The universal joints

and drives the power actuator that moves the output

and rod ends allow the platform to tilt in two axes. These

pot in a direction to reduce the error. Thus, in a

are designated pitch and roll to match ship motions for

feedback system, the output can be made to follow the

which the platform compensates. Figure 3-22 illustrates

input. This type of feedback system is often referred

a platform compensating for a roll motion, showing the

to as a servo loop.

major components of the platform.

The GSI stable platform uses two servo loops in

each axis, the gyro loop and the LVDT loop. In the gyro

SERVO LOOPS

loop, the gyro is used as an error detector sensing the

downward pull of gravity at its particular location. his

To understand the system operation, you need to

is termed earth's local gravity vector. The gyro lines

have an understanding of feedback control systems. A

itself up with this downward pull and any difference

feedback control system is a system where an input

between the gyro case and its internal reference provides

an output. This output is used as an error signal to correct

signal is compared with the system output and an error

the platform top to earth level.

signal is generated. This error signal is then amplified

Figure 3-22.--Functional diagram of the stabilized platform assembly.

3-16