A Non Conventional UAV In Ground Effect: Synthesis of a Robust Flight Control System,

ABSTRACTThis paper discusses the synthesis of an Extended Kalman Filter (EKF) to perform both wind velocities and stateestimation for a non conventional UAV flying in ground effect. Since, in IGE flight, motions into the symmetryplane are of primary concern, the study focuses on the longitudinal aircraft dynamics. The proposed estimatorrequires measurement of few flight variables, easily obtainable by means of conventional sensors; besides, itdoes not use Inertial Measurement Unit (IMU). To simulate a low cost sensing equipment, the model outputs arecorrupted by white noise of relatively high standard deviation. Furthermore, to cope with the low rate of theGPS with respect to the other sensors, the EKF algorithm is modified to allow for a dual rate measurementmodel. State propagation is obtained by means of an accurate, highly non-linear mathematical model of theUAV dynamics which allows to cope with both the non conventional configuration and ground effect. Combinedestimation of the UAV state and wind velocity is obtained by augmenting the system state vector with the windvelocity components. Numerical simulations show the effectiveness of the proposed method in widely differentmaneuvering conditions mixing IGE and OGE flight stages and in presence of largely dissimilar winddisturbance characteristics. The performance advantages with respect to a classical, computationally simplerestimation scheme are also highlighted. Closed loop simulations have shown the suitability of the obtained stateestimates for control purposes.