A semi-global model-based state observer for the quadrotor using only inertial measurements

Abstract : We propose a nonlinear observer to estimate the state (orientation and in-plane velocity vector) of the quadrotor, based on a drag-force-enhanced model. It is a simpler and more robust alternative to recent works using a similar model together with an Extended Kalman Filter (EKF). A particular state over-parametrization leads to a linear time-varying model with a nonlinear state-constraint that serves for the observer design. The proposed observer is able to ensure the uniform semi-global asymptotic stability of zero estimation error by in- corporating the nonlinear constraint into the correction terms.