Extending the Lifetime of Nano-Blimps via Dynamic Motor Control

Abstract

Nano-sized unmanned aerial vehicles (UAVs), e.g. quadcopters, have received significant attention in recent years. Although their capabilities have grown, they continue to have very limited flight times, tens of minutes at most. The main constraints are the battery’s energy density and the engine power required for flight. In this work, we present a nano-sized blimp platform, consisting of a helium balloon and a rotorcraft. Thanks to the lift provided by helium, the blimp requires relatively little energy to remain at a stable altitude. This lift, however, decreases with time as the balloon inevitably deflates requiring additional control mechanisms to keep the desired altitude. We study how duty-cycling high power actuators can further reduce the average energy requirements for hovering. With the addition of a solar panel, it is even feasible to sustain tens or hundreds of flight hours in modest lighting conditions. Furthermore, we study how a balloon’s deflation rate affects the blimp’s energy budget and lifetime. A functioning 68-gram prototype was thoroughly characterized and its lifetime was measured under different harvesting conditions and different power management strategies. Both our system model and the experimental results indicate our proposed platform requires less than 200 mW to hover indefinitely with an ideal balloon. With a non-ideal balloon the maximum lifetime of ∼400 h is bounded by the rotor’s maximum thrust. This represents, to the best of our knowledge, the first nano-size UAV for long term hovering with low power requirements.