Abstract

With multiple startups and Original Equipment Manufacturers (OEMs) competing to develop conceptual vehicles for Urban Air Mobility (UAM), new tools and methods are necessary to streamline the design process to meet the ambitious goals of this emerging industry. Determining appropriate lightweight configurations for the airframe structure is a challenging task, as it requires close collaboration between different disciplines, such as design, structural optimization and flight mechanics. The focus of this paper is on proposing an efficient workflow for conceptual structural sizing, which benefits from the tight integration of parametric design, simulation and optimization capabilities. To obtain the optimized lightweight design, parametric and non-parametric optimization techniques are combined. The workflow is entirely based on parametric design data, generated through a combination of graphical visual scripting and interactive 3D modeling. This method enables the engineer to create logic to parametrically build all required components of the internal structure, including ribs, spars, frames, and stringers. Fully associated with this parametric design model, a structural model of the UAM vehicle is built, allowing for design space exploration. In any given flight condition, the vehicle is subjected to aerodynamic loads, rotor forces, gravity and inertia loads. Aerodynamic loads are determined using a Computational Fluid Dynamics model, which is again fully associated with design, while rotor forces are computed to ensure flight loads equilibrium. Considering two exemplary load cases representing critical flight conditions, parametric and non-parametric structural optimization techniques are then combined, aiming at minimal weight for a targeted stress level. Based on results from a parametric design study, an optimized configuration of the parametric UAM vehicle is determined. In addition, non-parametric sizing techniques are applied, allowing for further reduction of mass by optimizing the distribution of skin thicknesses and stiffener properties. In a final step, structural requirement checks for buckling and strength are performed to validate the optimized configuration.