System Identification of a Nonlinear UAV Model with Distributed Aerodynamics and Flexible Structure

Benjamin Herrmann; Julian Theis; Frank Thielecke

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CEAS EuroGNC 2022

System Identification of a Nonlinear UAV Model with Distributed Aerodynamics and Flexible Structure

Benjamin Herrmann	Research Engineer, Institute of Aircraft Systems Engineering, Hamburg University of Technology, Nesspriel 5, 21129 Hamburg, Germany.
Julian Theis	Lecturer, Institute of Aircraft Systems Engineering, Hamburg University of Technology, Nesspriel 5, 21129 Hamburg, Germany.
Frank Thielecke	Professor, Institute of Aircraft Systems Engineering, Hamburg University of Technology, Nesspriel 5, 21129 Hamburg, Germany.

Abstract:
This paper presents the nonlinear system identification of a slightly flexible 25kg fixed-wing UAV in the time domain using a computationally efficient distributed aerodynamics model and a linear structural dynamics representation. The equations of motion are formed by making use of the free vibration modes of the structure and the mean axis formulation. The structural modes and mode shapes are determined from ground vibration tests. The distributed aerodynamics, accounting for elastic deformations, are modeled using a quasi-steady stability and control derivative approach and by applying strip theory. Initial distributions for the derivatives are obtained from vortex-lattice-method calculations. For matching the model response to the measured response, parameters for scaling the initial derivative distributions are introduced. The flexible model is subsequently identified based on flight test data using the output error method in the time domain and maximum likelihood estimation. A good overall identification result is achieved with a close match of the fast aircraft dynamics. Lastly, an evaluation is given on the suitability of the identified model for real-time simulation, loads estimation and active load control law design.

Keywords: System Identification; Nonlinear Flexible Aircraft Modeling; UAV

View PDF CEAS-GNC-2022-012

Benjamin Herrmann, Julian Theis, Frank Thielecke: System Identification of a Nonlinear UAV Model with Distributed Aerodynamics and Flexible Structure. Proceedings of the 2022 CEAS EuroGNC conference. Berlin, Germany. May 2022. CEAS-GNC-2022-012.

BibTeX entry:

@Incollection{CEAS-GNC-2022-012,

    authors = {Herrmann, Benjamin and Theis, Julian and Thielecke, Frank},

    title = {System Identification of a Nonlinear UAV Model with Distributed Aerodynamics and Flexible Structure},

    booktitle = {Proceedings of the 2022 {CEAS EuroGNC} conference},

    address = {Berlin, Germany},

    month = may,

    year = {2022},

    note = {CEAS-GNC-2022-012}

}