Method for reducing bias error in a vibrating structure gyroscope
First Claim
1. A method for reducing bias error in a Vibrating Structure Gyroscope having a vibrating structure, primary drive means for putting the vibrating structure into carrier mode resonance, primary pick-off means for sensing carrier mode motion, secondary pick-off means for sensing response mode vibration of the vibrating structure in response to applied rotation rate, secondary drive means for applying a force to control the response mode motion, closed loop primary control loops for maintaining a fixed amplitude of motion at the primary pick-off means and for maintaining the drive frequency at the resonance maximum, and secondary control loops for maintaining a null at the secondary pick-off means, in which the ratio SFQUAD divided by SFIN-PHASE is measured from the secondary control loop to provide a direct measurement of Sin (φ
-
SD+φ
PPO), according to the relationship;
SFQUAD=SFIN-PHASE×
Sin (φ
SD+φ
PPO)where SFQUAD is the quadrature scalefactor, SFIN-PHASE is the in-phase scalefactor, φ
SD is the phase error in the secondary drive means and φ
PPO is the phase error in the primary pick-off means, the total phase error φ
E is obtained directly from the measured Sin (φ
SD+φ
PPO) according to the relationship;
φ
E=φ
SD+φ
PPO and phase corrections are applied to one of the secondary drive means and the primary pick-off means to reduce the phase error φ
E and hence the quadrature bias error to enhance the performance of the gyroscope.
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Abstract
A method for reducing bias error in a Vibrating Structure Gyroscope having a vibrating structure, a primary drive for putting the vibrating structure into carrier mode resonance, a primary pick-off device for sensing carrier mode motion, a secondary pick-off for sensing response mode vibration of the vibrating structure in response to applied rotation rate, a secondary drive for applying a force to control the response mode motion, closed loop primary control loops for maintaining a fixed amplitude of motion at the primary pick-off device, for maintaining the drive frequency at the resonance maximum, and secondary control loops for maintaining a null at the secondary pick-off device. In the method the ratio SFQUAD over SFIN-PHASE is measured from the secondary control loop to provide a direct measurement of Sin (φSD+φPPO), according to the relationship SFQUAD=SFIN-PHASE×Sin (φSD+PPO) where SFQUAD is the quadrature scalefactor SFIN-PHASE is the in-phase scalefactor, φSD is the phase error in the secondary drive and φPPO is the phase error in the primary pick-off device. The total phase error φE is obtained directly from the measured Sin (φSD+φPPO) according to the relationship; φE=φSD+φPPO and phase corrections applied to the secondary drive and/or primary pick-off device to reduce the phase error φE, and hence the quadrature bias error, to enhance the performance of the gyroscope.
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Citations
9 Claims
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1. A method for reducing bias error in a Vibrating Structure Gyroscope having a vibrating structure, primary drive means for putting the vibrating structure into carrier mode resonance, primary pick-off means for sensing carrier mode motion, secondary pick-off means for sensing response mode vibration of the vibrating structure in response to applied rotation rate, secondary drive means for applying a force to control the response mode motion, closed loop primary control loops for maintaining a fixed amplitude of motion at the primary pick-off means and for maintaining the drive frequency at the resonance maximum, and secondary control loops for maintaining a null at the secondary pick-off means, in which the ratio SFQUAD divided by SFIN-PHASE is measured from the secondary control loop to provide a direct measurement of Sin (φ
-
SD+φ
PPO), according to the relationship;
SFQUAD=SFIN-PHASE×
Sin (φ
SD+φ
PPO)where SFQUAD is the quadrature scalefactor, SFIN-PHASE is the in-phase scalefactor, φ
SD is the phase error in the secondary drive means and φ
PPO is the phase error in the primary pick-off means, the total phase error φ
E is obtained directly from the measured Sin (φ
SD+φ
PPO) according to the relationship;
φ
E=φ
SD+φ
PPOand phase corrections are applied to one of the secondary drive means and the primary pick-off means to reduce the phase error φ
E and hence the quadrature bias error to enhance the performance of the gyroscope. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
-
SD+φ
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9. A Vibrating Structure Gyroscope having a vibrating structure, primary drive means for putting the vibrating structure into carrier mode resonance, primary pick-off means for sensing carrier mode motion, secondary pick-off means for sensing response mode vibration of the vibrating structure in response to applied rotation rate, secondary drive means for applying a force to control the response mode motion, closed loon primary control loops for maintaining a fixed amplitude of motion at the primary pick-off means and for maintaining the drive frequency at the resonance maximum, and secondary control loops for maintaining a null at the secondary pick-off means, in which the ratio SFQUAD divided by SFIN-PHASE is measured from the secondary control loon to provide a direct measurement of Sin (φ
-
SD+φ
PPO), according to the relationship;
SFQUAD=SFIN-PHASE×
Sin (φ
SD×
φ
PPO)where SFQUAD is the quadrature scalefactor, SFIN-PHASE is the in-phase scalefactor, φ
SD is the phase error in the secondary drive means and φ
PPO is the phase error in the primary pick-off means, the total phase error φ
E is obtained directly from the measured Sin (φ
SD+φ
PPO) according to the relationship;
φ
E=φ
SD+φ
PPOand phase corrections are applied to one of the secondary drive means and the primary pick-off means to reduce the phase error φ
E and hence the quadrature bias error to enhance the performance of the gyroscope.
-
SD+φ
Specification