Sun, KerryRegan, Christopher DGebre-Egziabher, Demoz2023-10-042023-10-042019Sun, K., Regan, C. D., & Gebre-Egziabher, D. (2019). Observability and Performance Analysis of a Model-Free Synthetic Air Data Estimator. Journal of Aircraft, 56(4), 1471–1486. https://doi.org/10.2514/1.C035290https://hdl.handle.net/11299/257319The performance, accuracy, and observability of a model-free angle of attack and angle of sideslip estimator are presented. The estimator does not require an aircraft dynamic model; rather, it only relies on measurements from a GPS receiver, an inertial measurement unit, and a pitot tube. The estimator is an inertial navigation system (INS)/GPS extended Kalman filter augmented with the states to account for wind and an additional measurement from a pitot tube. It is shown that the estimator is conditionally observable. Conditions (maneuvers) that enhance its observability are identified. A bound on the angle of attack and angle of sideslip estimate uncertainties is derived. The effect of INS/GPS, horizontal and vertical wind uncertainty on the accuracy of angle of attack and angle of sideslip estimate is assessed. Simulation and flight-test results of the method are presented. The results show that the 1−σ bound on a small, slow-flying unmanned aerial vehicle for angle of attack and sideslip angle estimates are about 5 and 3 deg, respectively.enArticle10.2514/1.C035290