Method and apparatus for controlling dither in a multiple gyro system
First Claim
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1. 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;
thenb) measuring the resulting rotations;
thenc) demodulating said resulting rotations to determine the cross-axis frequency content of each;
thend) deriving virtual drive signal components for each axis at said cross-axis frequencies;
thene) combining said virtual drive signal components with said predetermined frequency for each axis to create a new drive signal for each axis;
thenf) driving said gyroscopes with said new drive signals; and
theng) repeating steps a through f above.
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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.
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13 Claims
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1. 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:
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a) driving each of said gyroscopes at a distinct frequency whereby a predetermined drive frequency is associated with an axis of rotation;
thenb) measuring the resulting rotations;
thenc) demodulating said resulting rotations to determine the cross-axis frequency content of each;
thend) deriving virtual drive signal components for each axis at said cross-axis frequencies;
thene) combining said virtual drive signal components with said predetermined frequency for each axis to create a new drive signal for each axis;
thenf) driving said gyroscopes with said new drive signals; and
theng) repeating steps a through f above. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. 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:
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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. - View Dependent Claims (9, 10, 11, 12, 13)
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Specification