Nullspace-Based Wind Estimation for Unmanned Aerial Systems

A novel approach for in-flight wind estimation on small unmanned aerial systems (UAS) using the nullspace-based estimator design technique is presented. With this mode-based design technique, three individual wind estimators are derived, one for each wind velocity component. The nullspace-based approach allows synthesizing estimators such that their estimates are decoupled from each other, from any control inputs, and any modeled external disturbances. The resulting estimators have minimal dynamical system order, which is one of the major advantages of the proposed approach. Due to this minimal order, the dependence on the underlying design model is decreased, thereby increasing robustness against model uncertainties. The applicability of the method is demonstrated on a wind estimator design for TU Dresden’s research UAS, the Urban Condor, in two different sensor configurations. The first configuration makes use of the full sensor capabilities of Urban Condor, including GPS, an inertial measurement unit (IMU), and an air data system. The second configuration considers the more realistic scenario for commercial UAS by only using GPS and the IMU. The developed estimators are verified in a high-fidelity nonlinear simulation environment.