.

view B, and figure 7-40, view B, show platform

Pendulous oscillation is periodic angular

motion with the gravity vector as its midpoint.

operation with proper earth-rate and aircraft-rate

Periodic motion around the local vertical produces

torquing corrections.

obvious errors from an inertial platform.

An analog or a digital computer develops

This happens because misalignment about the

the signals necessary to properly torque the

horizontal plane introduces gravity components

gyros. The corrections for earth rate depend

on accelerometer inputs. The system will interpret

on the aircraft's position on the earth's surface.

gravity accelerations as horizontal acceleration of

The analog corrections come from highly accurate

the aircraft. The Schuler pendulum is a specially

potentiometers that produce trigonometric func-

constructed pendulum without the unwanted

tions of aircraft position. Position integrator

shafts drive the potentiometers. To maintain the

oscillatory motions of non-Schuler pendulums. It

is a special case of both the simple and the

stable element oriented to the north reference,

compound pendulums, which are discussed in the

torquing corrections rotate the platform. The

following paragraphs.

rotation is about the vertical axis compensating

for vehicle velocity.

dulum consists of a small body suspended by a

weightless string. The motion of the simple

A pendulum is any suspended mass that is free

pendulum is both periodic and oscillatory. The

to rotate about at least one axis. However, its

center of gravity is NOT on the axis of rotation.

period of the simple pendulum is given by the

Therefore, any pivoted mass that is not perfectly

mathematical formula

balanced is, by definition, a pendulum. The

inertial platform is a pendulous device and,

therefore, behaves as all pendulums behave. It

aligns to the dynamic vertical when at rest. The

pivot axis and the center of gravity align with the

gravity vector. The center of gravity will be on

the bottom. Also, it tends to break into its natural

period of oscillation whenever the aircraft

accelerates.

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