The Institute for Dynamic Systems and Control (IDSC), ETH Zurich, Switzerland has developed an algorithm allowing a quadrocopter to maintain stable flight despite the complete loss of a motor/propeller. In a previous video they have shown this algorithm in use, where a motion capture system was used to measure the position and orientation of the quadrocopter.
In this video a pilot flies the quadrocopter. The algorithm is executed on the quadrocopter’s onboard micro-controller, and the only sensors required are the quadrocopter’s angular rate gyroscopes.
Blinking LEDs, mounted on the quadrocopter’s arms, were used to indicate a virtual yaw angle, so that the pilot can control the vehicle with the same remote control commands after the failure. As an alternative to the LED system, an onboard magnetometer could be used to track the vehicle’s yaw angle. Alternatively, using more sophisticated algorithms, the system could be made to work using only the rate gyroscopes.
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.
This technology is patent pending, and we hope that it will soon be available as a product on most commercial platforms.