Saturday, May 16, 2009

Interesting Facts About Rate Gyros

Momentum can be the cause of a force under certain circumstances.
One such circumstance involves the imposition of rotation of an angular momentum vector (i.e. the angular momentum vector is rotated at a certain angular velocity)- The force produced in this manner is called Coriolis Force.

When a rotation occurs, the angular momentum vector (representing the stored kinetic energy of the rotating element) causes an out-of-plane bending force (called Coriolis force) that can be successfully used to accurately measure and represent the rotation rate i.e., measuring the coriolis force, is equivalent to measuring the rotation rate.

Because rate gyros depend on angular momentum as their workhorse, they are constrained to measuring ABOUT an axis i.e., they serve to measure rotation correctly only if the rotation axis is perfectly perpendicular to the angular momentum vector doing the work in the rate gyro. If the rotation happens about an axis that has an angle different from 90degrees to the angular momentum vector, then a second rate gyro is required to acquire additional information in order to give an accurate reading of the rotation being imposed.

Thus, for 3-D motion, one pair of gyroscopes is sufficient to deduce full orientation-change information. (However, commercial technology incorporates redundancies. The Hubble telescope for instance has 3 pairs of rate gyros.)

In solid state rate gyros, the electron serves as a spinning object and the rotation is measured by measuring the magnetic force created by the electron's perturbation.

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