UAM Vehicle Design with Emphasis on Electric Powertrain Architectures

Abstract

The research on the system architecture of Urban Air Mobility (UAM) vehicles is a vital part within the DLR internal project HorizonUAM. One of the project goals in HorizonUAM is the development of a system concept for an air taxi. This includes research on safe and certifiable onboard systems. The aim of this article is to present results and findings with emphasis on electric powertrain architectures in the multirotor air taxi design. A preliminary design methodology was developed therefor, which enables the examination of full-electric, turbo-electric and hybrid-electric powertrains. This methodology was used in a design study to investigate the influence of different powertrain architectures on the multirotor design. Different evaluation parameters, parameter sweeps and technology exploration of batteries and fuel cell systems were applied to analyze and evaluate their impact on the UAM vehicle design. The main design drivers are the mass of the energy sources and the overall powertrain efficiency, which have a direct impact on the evaluation parameters like power and energy efficiency, maximum take-off mass, and payload fraction. The study showed that different powertrain architectures could lead to opposite vehicle design criteria. Therefore, a clear solution for an advantageous powertrain architecture could not be found. Hybrid-electric solutions, e.g. fuel cell and battery systems or parallel hybrid-electric systems, offer the possibility of increasing efficiency in different flight phases through suitable power management while increasing system complexity. The disadvantage of a high battery mass of a full-electric solution could thus be at least partially reduced.