23rd International Symposium on Ballistics Tarragona, Spain 16-20 april 2007.
This article deals with a new system to ensure Guidance and Control (G&C) of an artillery projectile without the use of a complete standard Inertial Measurement Unit system (IMU). Nexter Munitions is interested in new technology based on magnetoresistive sensors due to their size, high resistance to extremely severe environments and their price. This new system replaces the three axis gyros of the inertial measurement unit by a three axis magnetic sensor unit (“gyrofree IMU”) strapped down in the principal axis of the projectile. It is called an “electronic compas” The system is based on the hypothesis that the “terrestrial magnetic field” vector, at a specific date, remains constant for several miles around the firing position. In flight, the real time comparison of this field and the magnetic field measured in projectile axis provides the attitude and rotation rate of the projectile. A real time algorithm has been developed to estimate and correct magnetic disturbances in flight. The performance of such a system is improved by the use of the accelerometers. First estimations show that miss distance precision could then be to less than a few meters in approximately more than 98% of the cases : as long as the longitudinal axis of the projectile is out side of a 10° cone around the local earth magnetic field vector. This level could be increased if the scenario is adjusted to geographic localisation of firing. In parallel with guidance and control algorithms development, Nexter Munitions has been conducting demonstrations.
