A velocity observer for exterior ballistics using an embedded frequency detection of pitch and yaw aerodynamics
Résumé
This article proposes a methodology for estimating the velocity (w.r.t the air) of a high-velocity flying shell from low- cost embedded sensors. The novelty is to exploit aerodynamics models in combination with a frequency detection approach, through a state observer. Besides its main rotation (spin), the shell has gyroscopic precession and nutation motions, which are measured by inertial sensors as pseudo-periodic signals. The instantaneous frequencies of these time-varying signals give direct information on the aerodynamics of the shell, and in particular, its velocity w.r.t the air. The frequency content of the signal of the strapdown sensors is exploited by means of a two-step approach consisting of frequency detection reconciled with the aerodynamic models by an observer. A switching gain is used to deal with the transition of the shell in the transonic regime. A proof of convergence is given. Experimental results are exposed.