Estimation of the Roll Angle in a Spinning Guided Munition Shell

Ruth Kreichauf and Erik Lindquist

Abstract:	A projectile in flight follows a trajectory defined by an interaction of gravity, aerodynamics, and mechanical forces due to spin, shape and possible steering fins. The projectile’s flight phases can be described in terms of a pre-launch phase, launch phase, and ballistic phase. Generally the navigation system cannot navigate through the high-g launch phase. However, after the high-g launch phase, at the start of the ballistic phase, the navigation system has to be aligned before it can navigate. Pre-launch, parameters such as elevation angle, muzzle velocity, heading and typical spin rate for the type of shell are known. After the short launch phase these pre-launch parameters’ errors are still small enough in pitch and heading to adequately initialize the navigation system. Due to the projectile's spin, its rapidly changing roll angle is however not known. The process of estimating the roll angle in a spinning projectile is usually referred to as ‘upfinding’. Honeywell has developed innovative methods to provide solutions to the upfinding problem in spinning projectiles by using Phase-Lock Loop and correlator algorithms that can be enhanced with complementary filters to dampen aerodynamic effects. This paper presents a new upfinding solution that is simple and work by using either gyro data or a combination of both accelerometer and gyro data in the upfinding process. This solution establishes the roll angle to a degree that is sufficient for a successful subsequent fine alignment and navigation phase. This algorithm can be applied to gun-launched guidance and navigation systems in ballistic trajectories to align the inertial navigation system.
Published in:	Proceedings of IEEE/ION PLANS 2006 April 25 - 27, 2006 Loews Coronado Resort Hotel San Diego, CA
Pages:	1 - 5
Cite this article:	Kreichauf, Ruth, Lindquist, Erik, "Estimation of the Roll Angle in a Spinning Guided Munition Shell," Proceedings of IEEE/ION PLANS 2006, San Diego, CA, April 2006, pp. 1-5. https://doi.org/10.1109/PLANS.2006.1650580
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