Flying a drone with a single motor and propeller may be theoretically possible, but in practice control is nearly impossible; this is why helicopters need a second rotor for balance and steering. Single-rotor solutions, meanwhile, tend to be unwieldy because of their giant propellers. Joshua Bird wanted to develop a very small, single-propeller drone.
The key to the solution was a hinged propeller hub that provides pitch and roll control through very high RPM and by varying the blade angle. When standard ESCs, which do not measure motor speed directly and instead rely on back EMF, proved inadequate, custom control code and lengthy trials were required. The problem of the drone losing its position and crashing was overcome with an infrared beacon placed in the room and a sensor on the drone.
The project files are being shared on GitHub. Next up is adding a scanner so the drone can also fly outdoors by referencing features in its surroundings.
Why it matters
This project questions, albeit at hobby scale, the established assumption that balance and steering in drones can only be achieved with a second rotor. Controlling a single propeller through high RPM and variable blade angle is an engineering problem that standard motor drivers cannot handle and that also demands a rethink on the software side; for that reason, the solution serves as an example for those interested in control algorithms as much as in hardware. Making the files available on GitHub means that anyone wanting to tinker with the same problem does not have to start their experiments from scratch. However, the drone still owes its sense of position to the infrared beacon in the room; until the indoor dependency is removed, the design’s practical value remains limited. Whether the planned scanner addition will make outdoor flight possible will be the project’s next real test.