工学：太陽電池で動く小型飛行ロボット

An ultra-lightweight, solar-powered micro aerial vehicle capable of sustained flight is described in a paper published in Nature. The device is lighter and smaller than existing sunlight-powered aerial vehicles, and may enable long-distance and long-duration aerial reconnaissance applications.

Micro aerial vehicles have the potential to be useful for communications and environmental rescue and monitoring. However, current micro aerial vehicles have short endurance — those weighing less than 10 grams often have a flight time of less than 10 minutes, which limits their usefulness. Traditional aerial vehicles use electromagnetic motors, the efficiency of which decreases as the size of the vehicle shrinks. Sunlight is an alternative power source; however, current solar-powered devices are unable to achieve untethered flight using this method.

To address these challenges, Mingjing Qi and colleagues designed ‘CoulombFly’, an ultra-lightweight, solar-powered micro aerial vehicle capable of untethered flight. CoulombFly weighs 4.21 grams and achieved sustained flight under natural sunlight conditions. The device combines an electrostatic propulsion system consisting of a motor and a 10-centimetre propeller with a high-voltage power convertor and solar cells. This enables the device to have a high lift-to-power efficiency as well as low power consumption. The solar cells generate low direct current (d.c.) power that is then converted into a high d.c. voltage by the power convertor. This high d.c. power is then transferred to the motor, causing the rotor to rotate and generate torque to drive the propeller and the device to lift. In a durability test, the device was able to sustain flight for one hour without experiencing performance degradation.

The authors suggest CoulombFly is the lightest and smallest sunlight-powered aerial vehicle designed so far. They argue that their system increased the endurance of these devices, which could expand their potential future applications.