Utilization of a magnetic sensor to compensate a MEMS-IMU/GPS and de-spin strapdown on rolling missiles
First Claim
1. A method for compensating the roll attitude error in the navigation solution for a rolling vehicle, comprising:
- sampling navigation data for a rolling vehicle;
generating an inertial attitude error estimate from the sampled navigation data;
monitoring an output of a magnetic field sensor, the magnetic field sensor having a sensitive axis being disposed perpendicular to an axis of rotation of the rolling vehicle, the output of the magnetic field sensor being generated as the rolling vehicle passes through a local magnetic field;
detecting a zero crossing point in the output of the magnetic field sensor;
calculating a measurement residual based on the navigation data at a time corresponding to the zero crossing point; and
updating the inertial attitude error estimate with the calculated measurement residual whereby the navigation solution remains stable.
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Abstract
A magnetic sensor that measures the angle of the sensor'"'"'s sensitive axis relative to a local magnetic field compensates the navigation solution of a MEMS-IMU/GPS navigation system. A stable navigation solution is thereby maintained. The magnetic sensor is mounted on a body axis of the vehicle perpendicular the spin axis of the vehicle. As the vehicle spins, the magnetic sensor provides an analog output voltage that varies sinusoidally with vehicle roll with the zero crossings occurring when the sensor'"'"'s sensitive axis is perpendicular to the local magnetic field. The magnetic sensor measurements combined with knowledge of the local magnetic field relative to the local level reference are used to correct the navigation solution'"'"'s roll error. Following high rate sampling of accelerometers and gyros, and algorithm to computational de-spin in the navigation solution is executed whereby navigation processing may be implemented with a non-rolled vehicle body frame algorithm.
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Citations
20 Claims
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1. A method for compensating the roll attitude error in the navigation solution for a rolling vehicle, comprising:
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sampling navigation data for a rolling vehicle;
generating an inertial attitude error estimate from the sampled navigation data;
monitoring an output of a magnetic field sensor, the magnetic field sensor having a sensitive axis being disposed perpendicular to an axis of rotation of the rolling vehicle, the output of the magnetic field sensor being generated as the rolling vehicle passes through a local magnetic field;
detecting a zero crossing point in the output of the magnetic field sensor;
calculating a measurement residual based on the navigation data at a time corresponding to the zero crossing point; and
updating the inertial attitude error estimate with the calculated measurement residual whereby the navigation solution remains stable. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for computationally de-spinning strapdown inertial sensor measurements for navigation on a rolling vehicle, comprising:
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sampling navigation data of a rolling vehicle, the sampled data including accelerometer data, roll data, pitch data and yaw data for the rolling vehicle;
integrating roll data of the sampled data over a predetermined interval;
computing a roll angle change transform;
updating the roll angle change transform with incremental roll change data;
transforming and integrating accelerometer data with the roll angle change transform whereby the accelerometer data is de-spun;
transforming and integrating pitch and yaw data with the roll angle change transform whereby the pitch and yaw data are de-spun; and
computing a navigation solution strapdown at a predetermined navigation processing rate. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16)
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17. A method for computing a navigation solution in a rolling vehicle, comprising:
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sampling navigation data of a rolling vehicle, the sampled data including accelerometer data, roll data, pitch data and yaw data for the rolling vehicle;
calculating a measurement residual based upon the output of a magnetic sensor that detects the orientation of the rolling vehicle with respect to a local magnetic field;
updating an inertial attitude error estimate with the calculated measurement residual whereby the navigation solution remains stable;
computationally de-spinning accelerometer and pitch and yaw data; and
computing a navigation solution strapdown at a predetermined navigation processing rate with the de-spun accelerometer, pitch and yaw data. - View Dependent Claims (18, 19, 20)
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Specification