​Abstract: Electric unmanned rotorcraft are increasingly considered for aerial mobility applications, but their performance is limited by onboard energy storage, making energy efficiency a critical design consideration. This study investigates the effects of rotor speed scheduling and trajectory optimization on total mission energy consumption for a hover–ascent–cruise–descent profile. A mission-based energy model is developed to estimate rotor power and cumulative energy across all flight phases. A sequential optimization framework is adopted, in which rotor speed optimization is first performed to determine a phase-dependent rotor speed schedule, followed by trajectory optimization conducted under a fixed rotor speed profile obtained from the preceding stage, with only trajectory parameters allowed to vary. A joint optimization is then evaluated to assess the integrated effect of both strategies. Results show that rotor speed optimization reduces energy by 21.85 %, while trajectory optimization achieves a larger reduction of 24.99 %. The joint optimization yields the lowest energy consumption, with a total reduction of 25.01 %, providing only a marginal improvement over trajectory optimization. These findings indicate that trajectory design is the dominant contributor to energy savings, while rotor speed scheduling offers complementary benefits for improving rotorcraft endurance.

Keywords: Rotor speed scheduling, Trajectory optimization, Energy consumption, Energy-efficient flight, Electric rotorcraft, UAV, Mission energy optimization.

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