A Stable Coin-sized Helicopter Design with Enough Lift for Autonomy
K.
Johnson
,
V.
Arroyos
,
G.
Donahoe
, and
6 more authors
Science Advances, Mar 2026
Hovering robots near the 1 g scale offer considerable advantages in safety, cost, and energy harvesting, but practical applications have been hindered by flight instability and limited or nonexistent payload capacity. We present Coin-Copter, a near-gram helicopter with a high-lift rotor and laser-microfabricated stabilizing flybar that achieves passive stability and sufficient lift to carry an onboard power source and control electronics. Using a single lift motor, instead of multiple smaller motors or electrostatic-actuated flapping wings, avoids unfavorable scaling in motor efficiency and the drawbacks of high-voltage systems. The miniaturized flybar-rotor mechanism is folded from a single composite sheet, with flexures replacing the spherical joints and curved airfoils used in larger helicopters. A dynamics model and free flight tests show the flybar couples gyroscopic forces to the cyclic angle of attack and teetering angle of the main rotor to provide attitude stability in flight. A small tail rotor controls the system’s heading. We characterized Coin-Copter’s performance with different main motors and flat-foldable rotor airfoil geometries, yielding vehicle masses from 0.69 g to 1.6 g. Including the estimated power-electronics mass, the platform achieves a maximum lift-to-weight ratio of 3.5 at a total vehicle mass of 1.2 g, exceeding that of similarly sized flapping-wing robots and insects. These findings demonstrate the feasibility of untethered helicopter flight at the near-gram scale, opening a path towards fully untethered near-gram aerial robots.