System Identification for a Subscale Tiltrotor eVTOL Aircraft from Hover Flight-Test Data

This paper describes the system identification process and hover flight-test modeling results for a subscale tiltrotor electric vertical takeoff and landing (eVTOL) vehicle built at NASA Langley Research Center. The vehicle, referred to as the Research Aircraft for eVTOL Enabling techNologies (RAVEN) Subscale Wind-Tunnel and Flight Test (SWFT) model, operates as a dynamic modeling and flight controls research testbed used to advance eVTOL aircraft technology. Expanding on previous eVTOL aircraft system identification research leveraging wind-tunnel testing and flight simulations, a modeling approach using flight data is presented for
the RAVEN-SWFT aircraft. The full system identification methodology is outlined, including the experiment design, flight testing, and model identification steps. An overview of the current flight-test envelope expansion status is included, alongside modeling results obtained from hover flight testing using two types of maneuvers employing multisine excitation inputs. The flight-derived model is shown to have a close model fit and good prediction performance in the hover flight regime. The methods discussed in the paper help to inform efficient flight-test-based modeling strategies for many current and future eVTOL aircraft.