Engineer develops single-motor 3D-printed drone using hinged propeller and rapid motor speed changes

Single-Motor Drone Design

Joshua Bird, a software engineer, developed a single-motor drone that uses a unique control method. Unlike most rotary-wing aircraft that require mechanisms like swashplates or secondary propellers to manage torque and direction, this drone achieves stability and maneuverability with just one motor and propeller.

The design incorporates a hinged propeller and relies on rapid adjustments to the motor's rotation speed. Accelerating the motor produces more reaction torque, while decelerating applies opposite reaction torque, allowing the drone to balance these forces to control body torque.

Directional Control Mechanism

Directional control is also managed by the hinged rotor. Each rotor blade is mounted on a 45-degree hinge, causing it to pivot when the motor accelerates. This action makes one blade pitch up for increased lift and the other pitch down for reduced lift. By precisely accelerating and decelerating the motor, the drone can control its roll and pitch movements.

Yaw control is achieved through a combination of main rotor torque, motor adjustments, and 3D-printed stabilizing fins.

Technical Implementation

The drone utilizes custom flight controller and motor controller firmware. This firmware enables the motor to react to necessary changes in under 0.2 milliseconds, which is critical for maintaining stability and control with this method. The rapid response time allows for the continuous balancing act required by the single-motor design.

Development and Testing

During development, Bird encountered and resolved several issues. This included building a high-speed camera using a Sony camera and a flash unit to analyze propeller behavior, which revealed that the initial propellers were too soft and needed replacement with sturdier 3D-printed versions. Extensive test flights were conducted, involving numerous crashes and fine-tuning of the drone's programming.