For drones with four propellers – also known as quadcopters – the failure of one motor is a big problem. When one rotor fails, the drone begins to spin on itself like a ballerina. This high-speed rotational motion means that once it starts spinning, the drone is no longer able to estimate its position in space and eventually crashes.
University of Zurich researchers used information from onboard cameras to stabilize the drone and keep it flying autonomously after one rotor suddenly gives out. The cameras can be used to keep damaged quadcopters in the air and flying stably, even without GPS. Algorithms combine information from the two cameras to track the drone’s position relative to its surroundings, enabling the onboard computer to control the drone as it flies – and spins – with only three rotors.