Method and apparatus for controlling dither in a multiple gyro system
AssigneeLitton Systems, Inc.
InventorsJohn G. Mark, Ray D. Dykeman, Daniel A. Tazartes, William B. Ware
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Abstract
A method and apparatus for controlling dither in a multiple gyro system. Each gyro is driven at a distinct nominal frequency. The resulting gyro motions are measured, then demodulated to determine their cross-axis frequency content. Virtual drive signals are generated in light of the cross-axis interactions, then combined with the nominal drive frequencies in such a way that the measured cross-axis effects, resulting in either signal intermodulation or block coning, are nulled.
Claims13
A method for controlling cross-coupling in a navigation system of the type wherein a plurality of gyroscopes is dithered about a plurality of axes of rotation with respect to an instrument block, said method comprising the steps of:
- a) driving each of said gyroscopes at a distinct frequency whereby a predetermined drive frequency is associated with an axis of rotation;
- then
- b) measuring the resulting rotations;
- then
- c) demodulating said resulting rotations to determine the cross-axis frequency content of each;
- then
- d) deriving virtual drive signal components for each axis at said cross-axis frequencies;
- then
- e) combining said virtual drive signal components with said predetermined frequency for each axis to create a new drive signal for each axis;
- then
- f) driving said gyroscopes with said new drive signals;
- and then
- g) repeating steps a through f above.
Apparatus for controlling cross-coupling in a navigation system of the type wherein a plurality of gyroscopes is dithered about a plurality of axes with respect to an instrument block wherein the improvement comprises:
- a) means for driving each of said gyroscopes at a distinct frequency;
- b) means for generating a signal responsive q to the resulting movement of each of said gyroscopes;
- c) means for demodulating each of said signals to determine the cross-axis frequency content thereof;
- d) means for deriving virtual drive signal components at said cross-axis frequencies;
- and
- e) means for combining said virtual drive signal components with said distinct frequencies.
Dependencies are inferred from the claim text.