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

This paper addresses the problem of attitude and heading restitution for a VTOL UAV. We describe an observation strategy to restitute the complete attitude matrix of the vehicle starting from Inertial Measurement Unit (IMU) and magnetometers. This study is a part of the development of the ducted fan UAV designed by Bertin Technologies. First, a measured orientation matrix is calculated from both inertial vectors which are the gravity and the earth magnetic field. Then, an estimated orientation is built by integrating gyroscopic readings, and corrected by the measured one. Nonlinear observation techniques are used to design a nonlinear estimator of the orientation matrix and an adaptive filter of the gyroscope’s bias which ensure the convergence of the observer. Such an observer is as efficient as classical Extended Kalman Filtering based observers, and easier to implement in real time. Simulations are proposed to illustrate the concept. Copyright c ©2005 IFAC