Ultra-Light Solar-Powered VTOL Drone Achieves Continuous Flight In Sunlight
19 July, 2024 – Researchers at China’s Beihang University and the Center of Advanced Aero-Engine have introduced CouloumbFly, an exceptionally lightweight miniature rotorcraft capable of indefinite flight under sunlight. Weighing only 4.21 grams (0.15 ounces)—comparable to four paperclips—this palm-sized drone features a rotor diameter of 20 cm (7.9 inches), making it 600 times lighter than any other small solar-powered drone.
During tethered tests in natural sunlight, CouloumbFly achieved lift-off within a second and sustained flight for an hour without any loss of power. This endurance feat is especially remarkable for a miniature helicopter, which relies entirely on generating lift rather than gliding.
The drone’s exceptional VTOL (Vertical Take-Off and Landing) endurance is attributed to its propulsion system, which includes a minimalistic electric motor weighing just 1.52 grams (0.054 ounces) that drives the 0.44-gram (0.02-ounce) top rotor. The drone’s electrostatic motor features positive and negative stator plates and 64 thin vertical tabs acting as the rotor.
The team of researchers stated that whenever one of the brushes gets contacted by a rotor blade on the electrode plate, a capacitor gets generated between the next electrode plate and the rotor. The charge gets recorded by this capacitor and transferred each time. The charged rotor blade moves toward the subsequent electrode plate because of the electrostatic force. When the blade passes through, charge exchange occurs, ensuring consistent driving torque for continuous rotation.
Electrostatic motors, typically used as sensors in microelectromechanical systems (MEMS), are ideal for this drone as these eliminate the weight of magnetic coils and rotors. The drone’s base holds two ultra-thin solar panels, each about 4 cm square, generating 4.5 volts in sunlight. A 12-stage voltage multiplier and transformer increase this to nearly 9,000 volts, powering the stator panels. The rest of the drone consists of a minimalistic frame and a rotor shaft.
The VTOL drone continued to fly continuously throughout the whole 1-hour durability test, according to the researchers. The electrostatic motor proceeded to function smoothly and sustain steady performance, according to post-test data. This experiment demonstrates the motor’s excellent stability and durability, laying a foundation for future long-endurance MAVs (Micro Aerial Vehicles).
While still in its infancy, CouloumbFly has the potential to be utilized for long-term communications, surveillance, as well as search-and-rescue missions. The researchers aim to increase the drone’s payload capacity to accommodate small sensors and controllers, currently limited to 1.59 grams (0.056 ounces).
Future improvements may include a combination of rechargeable batteries and solar cells, potentially enabling 24-hour operations and enhancing adaptability to low-light and no-light conditions. Despite current limitations with sunlight availability and humidity, CouloumbFly represents a significant step forward in the development of ultra-light, long-endurance drones.
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