| 摘要 |
The invention relates to an apparatus for compensating the output of a pendulous induction compass transmitter to eliminate heading errors during turns due to the vertical component of the Earth's magnetic field as well as those due to the horizontal component of the Earth's magnetic field perpendicular to the axis of tilt. By compensating for the effects of the Earth's vertical field component, instabilities and anomalies such as "Northerly Turning Error" are eliminated or minimized. Compensation for vertical field error is provided by generating a signal proportional to the product of the Earth's magnetic field M, the sine of the magnetic dip angle D at the given latitude and the sine of the aircraft tilt or bank angle phi . A compensating signal proportional to cos phi is generated and used to compensate for two cycle error. These compensating signals are used to drive current through the transmitter windings to produce flux which opposes and cancels the flux sensed by the windings of the compass transmitter due to the vertical component of the Earth's field and which corrects that due to the horizontal component of the Earth's field which is perpendicular to the roll axis during turns. Since the magnitude of bank angle phi or its trigonometric function sin phi and cos phi can be readily obtained from the aircraft vertical roll gyroscope and dip angle D is known for any latitude and longitude, these two compensating signals can be easily generated and applied to the compass transmitter to achieve the desired result.
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