Aeromechanical Stability of Tilting eVTOL Multirotor using Multi-Body Dynamics

Aim
This project aims to deliver in-depth research towards the development of a multibody dynamics model (MBD) for investigating the aeromechanical stability of a tilting multirotor electrical vertical take-off and landing (eVTOL) aerial vehicle during its transition stage from hover mode to forward flight mode.
Research Novelty
Tiltrotors hold great prospects for both civil and military applications due to their dual functionality to operate like an aircraft cruising at high cruise speed, as well as vertical takeoff, landing and hovering like a helicopter. The complex process of the transfiguration of the nacelle and rotors from hover to forward flight mode poses numerous challenges in accurately modelling the performance and stability of their Urban Air Mobility (AUM) vehicles. Existing research on modelling and stability analysis of tiltrotors has been limited to common simplifications of rigid body dynamics which often ignores the nonlinearities of the tilting mechanism arising due to the influence of follower forces, aeromechanical and aero-inertial coupling during the design stage.
This project falls within EPSRC's Engineering Design and Nonlinear Systems research areas. This research aims at formulating an MBD model to establish derivation, modelling, analysis and development of a higher-order mathematical model of tilting mechanism for a multirotor eVTOL by application of the Udwadia-Kalaba framework. Udwadia Kalaba framework constitutes dynamic modelling of multibody systems that have been connected by kinematic constraints. Once the mathematical model has been derived, research would be directed towards analysis and assessment of dynamic behaviour of the tilting mechanism and rotors through the transition stage from hover mode to forward flight and vice versa. This model would further be extended to conduct eigenvalue analysis and whirl flutter analysis for the rotor to determine the stability boundaries during early design stages.
Objectives
The objectives of the research are as follow:
I. Investigating state-of-the-art multi-body modelling approaches for tilting multirotor mechanisms.
II. Derivation and development of a higher-order mathematical model for a tilting multirotor using the Udwadia Kalaba framework.
III. Validation of the Udwadia Kalaba model with Finite Element Model and state-of-the-art MBD tools.
IV. Utilization of the developed MBD model to analyze the impact of transition from hover mode to forward flight mode on the stability margins and performance through eigenvalue analysis of rotor, determination of whirl flutter boundaries, etc.