If you’ve flown a quadcopter, you’ll know what happens when a propeller stops or fails: the thing flips around and crashes. Using a new system from Mark W. Mueller, Simon Berger, and Raffaello D’Andrea at ETH Zurich, however, quadcopters can automatically right themselves after motor failure and can even allow a human operator to control the drone until it is safely on the ground.
When a motor or propeller fails, the fail-safe routine keeps the drone more or less upright. LEDs on the arms show the user a “virtual yaw angle” so they can handle the robot as it flies, but eventually the team will add a magnetometer to handle this automatically. The team writes:
The failsafe controller uses only hardware that is readily available on a standard quadrocopter, and could thus be implemented as an algorithmic-only upgrade to existing systems. Until now, the only way a multicopter could survive the loss of a propeller or motor is by having redundancy (e.g. hexacopters, octocopters). However, this redundancy comes at the cost of additional structural weight, reducing the vehicle’s useful payload. Using this technology, (more efficient) quadrocopters can be used in safety critical applications, because they still have the ability to gracefully recover from a motor/propeller failure.
The system can even right itself if more than one motor fails. Most important, however, is the fact that the system can work in software – there are no hardware modifications at all. This means your usual quadcopter can become a self-righting, self-flying super machine with just a firmware update.
