Dynamic Performance Analysis of Hybrid-Electric Propulsion Systems for an Urban Air Mobility
Creators: name:  D. LEE 
name:   H. BANG 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: SYSTEM INTEGRATION
AERONAUTICS

description: In the last two decades, Urban Air Mobility (UAM) has obtained a lot of interest because UAM can reduce travel time by expanding the operation path in three dimensions. According to the regulation about the emission of carbon dioxide,1 many aerospace companies and institutions have developed the full-electric UAM system to make a difference from conventional aircraft, which is used the Internal Combustion Engine (ICE). For example, Airbus Vahana, Ehang 184, Kitty Hawk Cora, Lilium Jet and Volocopter are a popular UAM that uses electricity as the power source.2 However, lithium-ion battery, mainly used as a source in the full-electric system, has low energy density and a long recharging time. This property makes it impossible for UAM to operate the long-endurance mission. Therefore, it is essential to use additional power sources such as gasoline,3 fuel cell,4 photovoltaic cell5 to solve this problem. In particular, the gasoline-battery type hybrid system is widely used because the response of fuel cell to the instant required power is slower than gasoline hybrid propulsion system6 and the photovoltaic cell can not produce enough power to sustain the UAM.7 The hybrid propulsion systems generally consist of motors, engines, generators, power management unit and battery. Although much literature about the design of the powertrain for UAM exists, choosing the appropriate component is still challenging because each property of component for UAM is unknown and unpredictable due to a shortage of commercial platforms and components. Furthermore, it is difficult to analyze how each component affects the entire hybrid system because hybrid parts are closely intertwined. Moreover, most hybrid system design scheme is based on the required power equation, not a dynamic simulation analysis. Osita N. Ugwueze was proposed the eVTOL design approach to estimate the initial motor.8 The sizing of the engine pack for a distributed series hybrid-electric propulsion system is addressed to choose the engine in five options.9 Jianan Zong was analyzed the maximum takeoff mass and fuel consumption of VTOL UAVs with different hybrid propulsion systems to meet the same performance requirements and designed mission profiles.10 Therefore, we propose the initial sizing method for each component and dynamic analysis framework based on mathematical modeling to check the feasibility of the designed hybrid propulsion system considering the transient response in the mission profile. First, the empty weight as a function of maximum take-off weight (MTOW) and each component weight as a function of required power is derived using the least square fitting method from the data. Second, the mathematical model and simplified data-based model for motor and electric signal controller are proposed to make the series and parallel hybrid-electric propulsion system model. Third, the carrot-chasing guidance law and feedback linearization controller is used to implement the simulation to consider the fuel mass reduction and transient required power in real-time. Finally, the state of charge (SOC) and the fuel mass, called a performance metric, are used to evaluate the validity of the hybrid-electric propulsion system through the integrated dynamic simulation.