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Agile, high performance aircraft are based more and more on flight mechanical unstable airframes with control laws stabilizing the air vehicle. It requires among others an accurate knowledge of the center of gravity position, particularly during agile maneuvering. Thus, this investigation is intended to serve a systematic framework in form of a fuel system which tries to cover all aspects of defueling during flight and which is formulated as a state space model. Measurement and process noise as well as biases are accounted for in the performance characteristics of fuel pumps and fuel probes. A simple maneuver simulation delivers the rates and accelerations exerted on the tanks which are typical for maneuvering. Various approaches such as an output and stabilized output error approach are compared with a simulated fuel probe measurement with respect to their fuel state prediction capability where all of them do not show the necessary reliability. Main outcome is that an open unguided integration of nominal pump rates as done in the output error method will not give acceptable results due to the presence of process and measurement noise. Stabilizing this method with measurement information improves the accuracy but still shows drawbacks particularly for lateral cg because the introduced measurement information is not fully harmonized with the time integration of the nominal pump rates which does not account the presence of process and measurement noise and any biases. Probe data gives robust fuel state information with average accuracy but still lacks the required local accuracy when content rates and fuel inclination angle increase at half empty tank contents. Thus, all approaches fail to provide the necessary accuracy particularly during maneuvering conditions so that future works must focus on approaches which can fuse all available sensor and fuel system information in an optimal way.
Deutscher Luft- und Raumfahrtkongress 2014, Augsburg
Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn, 2014
21,0 x 29,7 cm, 15 Seiten
Stichworte zum Inhalt:
parameter estimation, sensor fusion