Energy-aware trajectory planning considering multi-physics dynamics for fuel cell-powered rotary-wing unmanned aerial vehicles

Abstract Electric vertical take-off and landing (eVTOL) unmanned aerial vehicles (UAVs) have limited flight time and range due to energy and power constraints in their power system components. This paper proposes a novel energy-aware trajectory generation method for rotary-wing UAVs powered by hydrogen that optimises fuel cell energy consumption by considering the dynamic behaviour of the propulsion system. The proposed method incorporates multi-physical effects of the fuel cell, electronic speed controller, motor, UAV dynamics and propeller. After validating the fuel cell propulsion model based on literature, the energy-aware trajectory optimisation problem is formulated and solved using the upper C a s upper A upper D i C a s A D i $ CasADi$ and upper O p t i m upper T r a j O p t i m T r a j $ OptimTraj$ frameworks. The study examines energy-optimal trajectory planning for two fuel cell-powered topologies: semi-active (Setup A) and direct (Setup B). The key characteristics of the fuel cell, voltage drop ( upper E Subscript d E d $ {E}_{d}$ ) and voltage of the fuel cell capacitor voltage ( upper V Subscript d V d $ {V}_{d}$ ), are considered to represent the dynamic behaviour of two different fuel cells during a mission starting at 40 m in the x direction and 20 m in the z direction. The simulation results show that Setup B has lower transient current fluctuations and a more stable power profile than Setup A, as evidenced by the decreased derivative of fuel cell current and hydrogen consumption rate. Energy-aware trajectory generation has been shown to reduce cumulative energy consumption by optimising vertical and forward velocity profiles, increasing the endurance of rotary-wing UAVs. To summarise, this study presents a novel methodology for energy-aware trajectory optimisation in fuel cell-powered UAVs by incorporating propulsion system dynamics into flight planning, which has been largely overlooked in the existing literature on hydrogen-powered rotary-wing UAVs.