Drones are very advanced aerial vehicles but they come with their own set of vulnerabilities. System malfunctioning is a common problem faced by drone pilots. This freezes the drone and it plummets down to a crash. Harsh weather may also damage some rotors thereby resulting in a crashed drone. To prevent such problems several companies are developing methods to safely land the drone in case of failure. Parachute modules have already been developed which deploy when a drone loses altitude. Another technology has been invented by researchers from the Netherlands’ Delft University of Technology which allows the drone to hover even when one or two of its rotors fail in mid-air. Generally a quadcopter requires all four rotors to function smoothly, failure of a single rotor may inhibit the drone from flying altogether.

This technology is of vital use as it requires no additional components or modules and can practically be applied to any drone. At the recent International Conference on Intelligent Robots (IROS 2018) in Spain, the TU DELFT team demonstrated the “fault tolerance controller” which allows a quadrotor to continue flying at high speeds, even if a rotor has broken or a motor has failed. The quadcopter may not retain its primary features while using this technology but it will save the drone and prevent loss to life and property. An interesting part about this fail-proof system is that the drone retains forward momentum while trying to remain airborne. This can greatly help the drone to land safely or return to base. Researchers from DELFT used data from the drone’s built in Gyroscope and accelerometer to work out a method to keep the drone airborne despite multiple rotor failure.

A modified version of Parrot Bebop 2 with a missing rotor. This was the drone in which the technology was first incorporated.

“Imagine that when a quadrotor is delivering an important package over water where strong wind blows. All of sudden one motor malfunctions,” Sihao Sun, a researcher on the project, said. “Normally in this case, the drone will crash into the water together with the package. But with our technology, it is able to continue flying at a considerable speed to fly back to a safe landing place. This could save the package and the drone itself.”

Watch how the drone corrects its flight despite a rotor failure in a wind tunnel: