Dynamic Modeling and Analysis of Tilt-Wing Electric Vertical Take-Off and Landing Vehicles

Abstract

Electric vertical take-off and landing (eVTOL) aircraft enable new transport options in regional and urban air mobility. One promising but only little investigated and understood subcategory comprises tilt-wing eVTOLs. They offer high efficiency and long flight ranges but come with a trade-off in increased complexity. Consequently, a critical step towards market entry is the development of mature and safe hybrid pilot-autonomy control systems, including fault detection, identification, and recovery (FDIR) concepts. That requires a mid-fidelity dynamic model with sufficient accuracy, which is not yet available despite a long history of tilt-wing research. Without a representative model, no detailed analysis and identification of a trimmed transition trajectory could be performed. This, however, is a crucial step in the development of a control system. We approach the problem by applying and combining current modeling approaches. Furthermore, a trim analysis of different flight phases, including the transition, is conducted. The identified model lays the foundation for a representative and detailed development and investigation of future control designs, bringing tilt-wing eVTOLs closer to airworthiness.

Tilt-Wing Control Design for a Unified Control Concept

“…This work proposes a unified control function for an integrated six-degree-of-freedom rigid body model based on [10]. Relevant flight control requirements for the unified control scheme (e.g., decoupling capabilities) and UAM operations and certification (e.g., according to air-and rotorcraft standards) are identified.…”

“…The tilt-wing eVTOL dynamic model is based on a simplified version of the model published in [10]. The basis of the integrated dynamic model consists of the 6-DOF rigid body flight mechanical equations of motion and the relevant forces and moments acting during the different flight phases, i.e., mainly propulsive and aerodynamic forces and moments.…”

“…Furthermore, pm denotes the torque difference between clockwise and counter-clockwise rotating rotors to zero, fr the difference between front and rear rotors to zero, and lr the difference between left and right rotors to zero. The aerodynamic forces and moments B f and B m are defined according to [10] as…”

“…with the rotation matrix B R W from wind frame to body frame, the reference span width = 6.87 m, mean chord length = 0.65 m, and the reference wing area = 8.93 m, as well as the dynamic pressure = 1 2 2 with = 1.225 kg m −3 . The angle of attack , the sideslip angle , and the airspeed are defined according to [10]. A and E are the aileron and elevator deflections, respectively.…”

“…Additionally, the vehicle design consists of mostly known parts and does not require, for instance, little studied propulsion concepts. The used aircraft configuration is shown in [10] and consists of a fuselage and tandem tilt-wings with two canard wings in the front and two main wings in the back, each carrying two propeller engines and one control surface.…”