Delay-compensated maximum likelihood estimation method for quadrotor UAV

This paper considers a maximum likelihood estimation problem for a quadrotor UAV under the existence of sensor delays. Since the state equation of the UAV is nonlinear, we propose an approximated method consisting of the following two steps. The first step is devoted to estimation of the past state based on the delayed output. We use an extended Kalman filter for this purpose. As the second step, an estimate of the present state is calculated by simulating the linear approximated system from the past to the present time. It is proved that the proposed method provides an approximated maximum likelihood estimation. The effectiveness of the estimator is verified by an experiment.