Structural design of a compact foldable coaxial twin-rotor UAV

The coaxial twin-rotor unmanned helicopter features a compact structure, high payload capacity, and efficient hovering performance, making it a highly versatile aircraft with broad application prospects. Traditional coaxial helicopters employ complex gear systems and inner/outer shaft mechanisms to drive the dual rotors, resulting in intricate mechanical structures and control systems that hinder miniaturization and lightweight development. This paper presents a novel compact coaxial twin-rotor foldable unmanned helicopter. The design innovatively adopts dual electric direct-drive motors to power the counter-rotating rotors, significantly simplifying the mechanical transmission while enabling rotor wing folding. A functional prototype has been successfully developed, demonstrating its potential as a military-operations-capable platform for payload deployment.