Hybridized attitude determination techniques to improve ballistic projectile navigation, guidance and control

Ballistic projectiles accuracy depends on measurement systems for position and attitude determination. Precise rotation determination is an expensive task in aircraft, as it is usually determined by strap-down sensors such as fiber optic gyros or MEMS. Particularly in ballistic projectiles, these gyro determination devices increase their price as they need to bear enormous accelerations during the initial stages but not during the ballistic flight. A new approach to improve ballistic projectile navigation, guidance and control, which integrates hybrid attitude determination methods and gravity vector estimation method, is presented in this paper. Measurements of accelerometers, GNSS-sensors and Semi-Active photo-detectors are hybridized to get such a result. The attitude determination method, avoiding the use of gyroscopes, measures pairs of vectors, i.e., gravity, velocity and line of sight vectors, in a pair of reference systems, i.e., body fixed and north-east-down reference frames. Gravity vector estimation is based on flight mechanics and aerodynamics of a ballistic projectile, which involves a deeply nonlinear behavior, but it may be extrapolated to any aircraft, and later employed in an attitude determination algorithm. Modified proportional navigation techniques and previously developed control methods are employed during flight. The presented approach is tested on a realistic nonlinear model flight simulations to prove accuracy of proposed algorithms.