Identification and selection of rotorcraft candidate models to predict handling qualities and dynamic stability

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Wartmann, J.
Greiser, S.
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Current frequency-domain system identification methods require an open-loop experiment design for data collection to identify one model of a vehicle. This makes open-loop system identification for unstable systems like rotorcrafts challenging. The optimized Predictor-Based Subspace Identification method also estimates accurate models from closed-loop data. In this paper, a parameter study is conducted to identify a set of bare airframe models of the ACT/FHS research rotorcraft using this subspace method. A selection method is introduced to chose appropriate candidate models from the identified set. The selected candidate models differ slightly in terms of the model invariants and are all a valid approximation of the rotorcraft dynamics. Consequently, the selected candidate models can be used to predict the possible properties of the system and their uncertainties. Here, the candidate models are employed to estimate the dynamic stability and handling qualities of the ACT/FHS bare airframe and two control system of the ACT/FHS research rotorcraft.