Multidisciplinary Design Optimization of the Actuation System of a Hybrid Electric Aircraft Powertrain

In the context of hybrid electric and full electric powertrains for future less-pollutant aircrafts, this paper focuses on the multidisciplinary design optimization (MDO) of the actuation system, including a surface-mounted PMSM in order to maximize the power density of the device: this study is a preliminary approach before integrating the whole powertrain. After an introduction of the MDO context, the analytical model of the electric motor is detailed. It integrates multi-physical aspects (electric, magnetic, mechanical, thermal, partial discharges and insulation, control and flight mission) and takes several heterogeneous design constraints into account. The optimization method involves a genetic algorithm allowing the reduction of the actuation weight with regard to a wide set of constraints. The results show the crucial sensitivity of the electro-thermal coupling, especially the importance of transient modes during flight sequences due to thermal capacitance effects. Another major point is related to the performance of the thermal cooling, which requires the introduction of an “internal cooling” in the stator slots in addition to the “base cooling” for stator and rotor. Gathering these analyses, the MDO leads to high power density actuators beyond 15 kW/kg with high-voltage–high-speed solutions, satisfying all design constraints (insulation, thermal, magnet demagnetization) over the flight mission.