Method and system for compensating for soft iron magnetic disturbances in a heading reference system
First Claim
1. A method for compensating for soft iron magnetic disturbances in a heading reference system, said system comprising a heading gyro disposed along a heading measurement axis and a magnetometer coupled to said heading gyro for providing an accurate heading relative to magnetic north;
- said method comprising the steps of;
detecting changes in said magnetometer due to soft iron magnetic disturbances during a detection period for providing a first detected magnitude of change;
detecting changes in said heading gyro relative to magnetic north during said detection period for providing a second detected magnitude of change;
comparing said first and second detected magnitude of changes for providing a potential difference value of change;
providing a predetermined acceptable threshold value of change based on a gyro drift;
determining if said potential difference value of change exceeds said predetermined acceptable threshold value of change; and
providing a heading correction value to said heading reference system when said potential difference value of change exceeds said predetermined acceptable threshold value of change for enabling adjustment of said heading gyro to maintain said accurate heading in the face of said soft iron magnetic disturbances.
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Abstract
A method and system for compensating for significant soft iron magnetic disturbances in a heading reference system, such as an aircraft heading reference system, such as an integrated standby unit; or a vehicle inertial system, provides a heading correction signal to the heading reference system when a detected difference in value between a gyro heading relative to magnetic north and a magnetometer reading during a defined measurement period exceeds a predetermined acceptable threshold value of change, such as one based on the expected gyro drift over that period. Upon receipt of the heading correction signal, the gyro heading is adjusted to maintain an accurate heading relative to true magnetic north. If this threshold value is not exceeded, then the magnetometer reading is used for the heading value. This method is iteratively repeated in order to continually maintain an accurate heading and may be employed for each heading measurement axis.
29 Citations
36 Claims
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1. A method for compensating for soft iron magnetic disturbances in a heading reference system, said system comprising a heading gyro disposed along a heading measurement axis and a magnetometer coupled to said heading gyro for providing an accurate heading relative to magnetic north;
- said method comprising the steps of;
detecting changes in said magnetometer due to soft iron magnetic disturbances during a detection period for providing a first detected magnitude of change; detecting changes in said heading gyro relative to magnetic north during said detection period for providing a second detected magnitude of change; comparing said first and second detected magnitude of changes for providing a potential difference value of change; providing a predetermined acceptable threshold value of change based on a gyro drift; determining if said potential difference value of change exceeds said predetermined acceptable threshold value of change; and providing a heading correction value to said heading reference system when said potential difference value of change exceeds said predetermined acceptable threshold value of change for enabling adjustment of said heading gyro to maintain said accurate heading in the face of said soft iron magnetic disturbances. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
- said method comprising the steps of;
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27. A heading reference system for compensating for soft iron magnetic disturbances and providing an accurate heading relative to magnetic north, the system comprising:
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at least one magnetometer capable of measuring a first magnetic data; at least one heading gyro capable of measuring a first angle rate data; an electronic storage device capable of storing the first magnetic data and the first angle rate data; and a microprocessor coupled to the at least one magnetometer, the at least one heading gyro and the electronic storage device being adapted to; receive the first magnetic data, the first angle rate data, a second magnetic data and a second angle rate data; compute a first magnetic magnitude of change between the first and the second magnetic data; compute a second angle rate magnitude of change between the first and the second angle rate data; compare a change between the first magnetic magnitude of change and the second angle rate magnitude of change to a threshold value based on a gyro drift; compute a calibration value for the at least one magnetometer or the at least one heading gyro based on the comparison; and calibrate the at least one magnetometer or the at least one heading gyro using the calibration value. - View Dependent Claims (28, 29, 30, 31, 32, 33, 34, 35, 36)
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Specification