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 gyro heading 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;
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 acceptable threshold value of change for enabling adjustment of said gyro heading 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.
27 Citations
40 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 gyro heading 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; 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 acceptable threshold value of change for enabling adjustment of said gyro heading 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, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
- said method comprising the steps of;
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18. 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;
providing an iterative control loop for controlling an output heading value corresponding to true magnetic north, and providing a compensated output heading reference value to said heading reference system from said iterative control loop for compensating for soft iron magnetic disturbances above a predetermined acceptable threshold value, said iterative control loop comprising the steps of reading and processing a value of data from said magnetometer and said heading gyro for providing a change in each of said values from an immediately previous reading of said values;
comparing said change in magnetometer value with said change in gyro value since said immediately previous reading;
determining whether any difference in said compared values exceeds an expected gyro drift over a period since said immediately previous reading;
providing a new heading value comprising said gyro change in value plus the immediately previous heading value as an output to said gyro when said difference exceeds said expected gyro drift over said period since said immediately previous reading, said predetermined acceptable threshold value comprising said expected gyro drift;
whereby said gyro heading is capable of maintaining said accurate heading in the face of said soft magnetic disturbances - View Dependent Claims (19, 20, 21)
- said method comprising the steps of;
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32. In a heading reference system for providing an accurate heading relative to magnetic north, said system comprising a heading gyro disposed along a heading measurement axis and a magnetometer coupled to said heading gyro for providing said heading;
- the improvement comprising means for detecting changes in said magnetometer output due to soft iron magnetic disturbances during a detection period for providing a first detected magnitude of change signal;
means for detecting changes in said gyro heading relative to magnetic north during said detection period for providing a second detected magnitude of change signal;
means coupled to said magnetometer and said gyro detection means for receiving and comparing said first and second detected magnitude of change signals for providing a potential difference value of change signal;
means for providing a predetermined acceptable threshold value of change connected to said potential difference value of change signal for receiving said signal and determining if the value of said potential difference value of change signal exceeds said predetermined threshold value of change for providing a heading correction signal to said heading reference system when said predetermined threshold value is exceeded, and means for receiving said heading correction signal for adjusting said gyro heading for maintaining said accurate heading in the face of said soft iron magnetic disturbances in response to said heading correction signal. - View Dependent Claims (33, 34, 35, 36, 37, 38, 39, 40)
- the improvement comprising means for detecting changes in said magnetometer output due to soft iron magnetic disturbances during a detection period for providing a first detected magnitude of change signal;
Specification