Active model-based nonlinear system identification of quad tilt-rotor UAV with flight experiments

To propose an accurate and less complex model of a special unmanned aerial vehicle (UAV), namely tilt-rotor UAV (TRUAV), this study identifies the active model-based nonlinear system of a quad-TRUAV. First, a nominal nonlinear model of the vehicle is formulated. Some unstructured nonlinearities are ignored to reduce the complexity of the model. Then, due to the unstable dynamics of the open-loop system, the format of this nominal model is considered to design an innovative smooth-switch attitude control via interconnection and damping assignment passivity-based control (IDA-PBC). Active model-based nonlinear system identification is studied for the vehicle with the designed control method and flight experiments. The model error vector is defined and estimated by the unscented Kalman filter (UKF) to improve the accuracy of the model. The main contribution of this paper is to identify the nominal nonlinear model and to develop an active model method of the quad-TRUAV. The attitude control method with an innovative smooth-switch structure is another contribution to flight experiments. Numerical results are displayed to present the experimental results and effectiveness of the proposed nonlinear models.