Quaternion-based global attitude tracking controller for a quadrotor UAV

In this work, the problem of quaternion-based global attitude stabilization is addressed, using the Backstepping technique. The proposed controller is conceived to be consistent in order to prevent the ambiguity in relating a given attitude to its two corresponding quaternions. The set of the two antipodal equilibrium error quaternions are rendered attractive and asymptotically stable. The error quaternion is then attracted by the nearest equilibrium in the set. In order to escape from the invariant and non attractive undesirable manifold, defined by attitude errors of 180°, the rigid-body attitude dynamics is augmented by a time varying dynamics. Simulation results illustrate the efficiency of the proposed controller, for attitude stabilization or tracking, even in the presence of a centred Gaussian noise, on angular velocity measurements.