Method and apparatus for compensating a magnetic compass
First Claim
1. The method of compensating a magnetic compass in a vehicle for magnetic deviation of the earth'"'"'s magnetic field comprising the steps of:
- (1) orienting the vehicle in any selected direction relative to magnetic north,(2) measuring the angle between a direction reference axis of the vehicle and the direction indicated by said magnetic compass in said vehicle,(3) adding a magnetic field at a known angle relative to said direction reference axis of the vehicle and memorizing the strength of the added magnetic field required to displace the direction indicated by said compass through a first predetermined angle,(4) and calculating the strength of the resultant magnetic field using the measured angle, the first predetermined angle and the memorized strength of the added magnetic field,(5) orienting the vehicle with said direction reference axis pointing one hundred eighty degrees away from said selected direction,(6) measuring the angle between the direction reference axis of the vehicle and the direction indicated by said magnetic compass,(7) adding a magnetic field at a known angle relative to said direction reference axis of the vehicle and memorizing the strength of the added magnetic field required to displace the direction indicated by said compass through a second predetermined angle,(8) calculating the strength of the resultant magnetic field using the last measured angle, the second predetermined angle and the last memorized strength of the added magnetic field,(9) and using the values of said resultant magnetic fields to determine the compensation required for said magnetic deviation.
1 Assignment
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Accused Products
Abstract
Method and apparatus are disclosed for compensating a magnetic compass in a vehicle for magnetic deviation. With the compass installed, the angle indicated by the magnetic compass relative to a direction axis of the vehicle is measured. A test magnetic field is added at a known angle relative to the direction axis of the vehicle. The strength of the test magnetic field required to displace the direction indicated by the compass through a predetermined angle is memorized. Then, the strength of the resultant magnetic field is calculated using the measured angle, the predetermined angle and the memorized strength of the magnetic field. After determining the strength of the resultant magnetic field with the vehicle oriented in any selected direction, the vehicle is then reoriented in a direction one hundred eighty degrees away from the selected direction and the strength of the resultant magnetic field in that orientation is determined in the same way. The value of the deviating magnetic field is calculated as one-half the vector sum of the two resultant magnetic fields.
242 Citations
14 Claims
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1. The method of compensating a magnetic compass in a vehicle for magnetic deviation of the earth'"'"'s magnetic field comprising the steps of:
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(1) orienting the vehicle in any selected direction relative to magnetic north, (2) measuring the angle between a direction reference axis of the vehicle and the direction indicated by said magnetic compass in said vehicle, (3) adding a magnetic field at a known angle relative to said direction reference axis of the vehicle and memorizing the strength of the added magnetic field required to displace the direction indicated by said compass through a first predetermined angle, (4) and calculating the strength of the resultant magnetic field using the measured angle, the first predetermined angle and the memorized strength of the added magnetic field, (5) orienting the vehicle with said direction reference axis pointing one hundred eighty degrees away from said selected direction, (6) measuring the angle between the direction reference axis of the vehicle and the direction indicated by said magnetic compass, (7) adding a magnetic field at a known angle relative to said direction reference axis of the vehicle and memorizing the strength of the added magnetic field required to displace the direction indicated by said compass through a second predetermined angle, (8) calculating the strength of the resultant magnetic field using the last measured angle, the second predetermined angle and the last memorized strength of the added magnetic field, (9) and using the values of said resultant magnetic fields to determine the compensation required for said magnetic deviation. - View Dependent Claims (2, 3, 4)
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5. The method of determining the strength of a resultant magnetic field in a vehicle which results from a deviating magnetic field and the earth'"'"'s magnetic field, said method comprising the steps of:
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(1) measuring the angle between a direction reference axis of the vehicle and the direction indicated by said magnetic compass in said vehicle, (2) adding a magnetic field at a known angle relative to said direction reference axis of the vehicle and memorizing the strength of the added magnetic field required to displace the direction indicated by said compass through a predetermined angle, (3) and calculating the strength of the resultant magnetic field using the measured angle, the predetermined angle and the memorized strength of the added magnetic field.
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6. The method of compensating a magnetic compass in a vehicle for magnetic deviation, said compass having a pair of compensating coils, said method comprising the steps of:
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(1) orienting said vehicle in any selected direction relative to the magnetic north direction whereby the rotor orients itself with said polar axis in alignment with a first resultant magnetic field resulting from a deviating magnetic field in the vehicle and the earth'"'"'s magnetic field, and thereafter,; (2) measuring the first uncompensated heading angle between said polar axis and a direction reference axis of the vehicle, (3) applying a first current to one of the compensation coils to generate a first test magnetic field to displace the rotor through a first predetermined angle to a first displaced orientation in which said polar axis is at a first test angle with said first test magnetic field, (4) memorizing the value of said first current, (5) calculating said first test angle using said first uncompensated heading angle and said predetermined angle, (6) calculating the strength of said first resultant magnetic filed using said first predetermined angle, said first test angle and the strength of said first test magnetic field, (7) orienting the vehicle with said direction reference axis pointing one hundred eighty degrees away from said selected direction whereby the rotor orients itself with said polar axis in alignment with a second resultant magnetic field resulting from said deviating magnetic field in the vehicle and the earth'"'"'s magnetic field, and thereafter, (8) measuring the second uncompensated heading angle between said polar axis and the direction reference axis, (9) applying a second current to one of the compensation coils to generate a second test magnetic field to displace the rotor through a second predetermined angle to a second displaced orientation in which said polar axis is at a second test angle with said second test magnetic field, (10) memorizing the value of said second current, (11) calculating said second test angle using said second uncompensated heading angle and said second predetermined angle, (12) calculating the strength of said second resultant magnetic field using said second predetermined angle, said second test angle and the strength of said second test magnetic field, (13) calculating the respective X-axis and Y-axis components of said first and second resultant magnetic fields, (14) and calculating the strength of the X-axis and Y-axis components of the X-axis and Y-axis components, respectively, of said deviation magnetic field as one-half the sum of said first and second resultant magnetic fields. - View Dependent Claims (7, 8, 9, 10, 11)
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12. Apparatus for compensating a magnetic compass in a vehicle for magnetic deviation, said compass having a magnetic rotor and having a known orientation relative to the direction reference axis of the vehicle and having compensation coils, said apparatus comprising:
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(1) means for measuring the angle between said direction reference axis and the direction indicated by said magnetic compass, (2) means for adding a magnetic field at a known angle relative to said direction reference axis, (3) means for memorizing the strength of the added magnetic field required to displace the direction indicated by said compass through a first predetermined angle, (4) and means for calculating the strength of the resultant magnetic field using the measured angle, the predetermined angle and the memorized strength of the added magnetic field. - View Dependent Claims (13, 14)
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Specification