Nonlinear attitude and gyroscope's bias estimation for a VTOL UAV

This paper addresses the problem of attitude and headingrestitution for a VTOL UAV. We describe an observation strategy torestitute the complete attitude matrix of the vehicle startingfrom Inertial Measurement Unit (IMU) and magnetometers. First, a measured orientation matrix iscalculated from both inertial vectors which are the gravity andthe earth magnetic field. Then, an estimated orientation is builtby integrating gyroscopic readings, and corrected by the measuredone. Nonlinear observer techniques are used to design anonlinear estimator of the orientation matrix and an adaptivefilter of the gyroscope's bias which ensure the convergence of theobserver. Such an observer is as efficient as classical ExtendedKalman Filtering based observers, and easier to implement in realtime. Simulations are proposed to illustrate the concept.