Solar Energy Harvesting for a Land-to-Recharge Tiltrotor Micro Aerial Vehicle

This work addresses the problem of self-sufficient long-term operation of UAVs in the context of multi-day mission profiles, by proposing the key innovation of onboard solar en-ergy harvesting while the vehicle remains grounded. Relying on a custom-developed small-sized energy harvesting module and a solar cell array embedded in its wings, the Micro Aerial Vehicle becomes capable of recharging its depleted battery levels during a days's cycle while idly sitting on the ground. During the self-recharge operation the vehicle's high-level electronics remain in hibernation, and the system is woken up once adequately charged, proceeding to enter into a mission, executing take-off, waypoint following, and landing autonomously. The cycle can be repeated indefinitely as long as solar energy is available. The presented system, the MiniHawk-VTOL is a rapidly prototyped Tricopter Tiltrotor designed to accommodate the aforementioned needs, aiming to achieve autonomous migratory mission patterns (land-to-recharge-and-resume). The power electronics used to accomplish this mission cycle are detailed, and the results are shown for a typical recharge cycle in near-optimal conditions, and for instances of typical broken and overcast cloud cover. Additionally, we present an experimental sequence of suspend-to-charge and wakeup-to-resume with autonomous GPS-based takeoff, mission execution, and landing.