R.M. Leitner

A new method for linearising nonlinear helicopter dynamics has been developed which can handle periodic dynamics with non-minimum phase or all-pass response due to control inputs. Rotor blades that are elastically hinged to the rotor hub have the property of forcing the rotor hub and the fuselage downward during a collective control step input. The subsequent downward motion is of short duration and corresponds in its behavior to an all-pass. In this paper, a method based on the convolution integral is shown to linearise the dynamics despite non-minimum phase behavior. The linearisation computes the stability and control matrices of the time-invariant state-space model, which is used for stability studies and linear control design. The linearisation method is verified by comparing the eigenvalues of the linear state-space model with the eigenvalues of the Floquet state transition matrix and additionally by comparing the step responses of the nonlinear and linear models. For this purpose, two rotor configurations (one standard and one coaxial) are trimmed and linearised based on a nonlinear multibody model. Both the multibody model and trimming using a multi-dimensional secant method are explained to better understand the complexity of linearising helicopter dynamics.

Deutscher Luft- und Raumfahrtkongress 2022, Dresden

Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn, 2022

Conference Paper

englisch

21,0 x 29,7 cm, 8 Seiten

urn:nbn:de:101:1-2022121614165205625683

10.25967/570400

Helicopter, Linearisation, Stability Analysis, Multibody Dynamics

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Leitner, R.M. (2022): Convolution Integral-Based Linearisation of Helicopter Multibody Dynamics. Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V.. (Text). https://doi.org/10.25967/570400. urn:nbn:de:101:1-2022121614165205625683.

16.12.2022