Due to power-after-launch mode of guided munitions of high rolling speed, initial attitude of munitions cannot be determined\naccurately, and this makes it difficult for navigation and control system to work effectively and validly. An in-flight self-alignment\nmethod aided by geomagnetism that includes a fast in-flight coarse alignment method and an in-flight alignment model based on\nKalman theory is proposed in this paper. Firstly a fast in-flight coarse alignment method is developed by using gyros, magnetic\nsensors, and trajectory angles. Then, an in-flight alignment model is derived by investigation of the measurement errors and\nattitude errors, which regards attitude errors as state variables and geomagnetic components in navigation frame as observed\nvariables. Finally, fight data of a spinning projectile is used to verify the performance of the in-flight self-alignment method. The\nsatisfying results show that (1) the precision of coarse alignment can attain below 5?; (2) the attitude errors by in-flight alignment\nmodel converge to 24???? at early of the latter half of the flight; (3) the in-flight alignment model based on Kalman theory has better\nadaptability, and show satisfying performance.
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