Robohub.org
 

Quadrocopter failsafe algorithm: Recovery after propeller loss

by
04 March 2014



share this:
Drone-Failsafe-Algorithm

UPDATE 04/03/2014:

In this video update, we show that a quadrocopter can be safely piloted by hand after a motor fails, without the aid of a motion capture system. This follows our previous video, where we demonstrated how a complete propeller failure can be automatically detected, and that a quadrocopter can still maintain stable flight despite the complete loss of a propeller. 

In the earlier video, we relied on an external motion capture system to measure the quadrocopter’s position and orientation.  By moving more of the algorithm onto the vehicle, the quadrocopter can now be piloted by hand after the failure. The algorithm is executed on the quadrocopter’s onboard micro-controller, and the only sensors required are the quadrocopter’s angular rate gyroscopes. We use blinking LEDs, mounted on the quadrocopter’s arms, 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, by using more sophisticated algorithms, the system could be made to work using only the rate gyroscopes.

ORIGINAL STORY 02/12/2013

The video in this article shows an automatic failsafe algorithm that allows a quadrocopter to gracefully cope with the loss of a propeller. The propeller was mounted without a nut, and thus eventually vibrates itself loose. The failure is detected automatically by the system, after which the vehicle recovers and returns to its original position. The vehicle finally executes a controlled, soft landing, on a user’s command.

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.

Failsafe_algorithm_sequence
(A) shows the quadrocopter in normal operation. In (B) the propeller detaches due to vibrations, and the quadrocopter starts pitching over in (C) – (E). In (F) the vehicle has regained control, and is flying stably.

The key functionality of the failsafe controller is a novel algorithm that I developed as part of my doctoral research at the Institute for Dynamic Systems and Control at ETH Zurich. This new approach allows such a vehicle to remain in flight despite the loss of one, two, or even three propellers. Having lost one (or more) propellers, the vehicle enters a continuous rotation — we then control the direction of this axis of rotation, and the total thrust that the vehicle produces, allowing us to control the vehicle’s acceleration and thus position.

Even if the vehicle can no longer produce sufficient thrust to support its own weight, this technology would still be useful: one could, for example, try to minimize the multicopter’s velocity when it hits the ground, or steer the multicopter away from dangerous situations such as water, or people on the ground.

This control approach can also be applied to design novel flying vehicles — we will be releasing some related results soon.

This technology is patent pending.

For more information, have a look at the Flying Machine Arena website, the IDSC research page, or just post your question in the comments below.

 

If you liked this article, you may also be interested in:

See all the latest robotics news on Robohub, or sign up for our weekly newsletter.



tags: , , , , , , , , , , , , , , , ,


Mark Mueller is a researcher at ETH Zurich's Flying Machine Arena.
Mark Mueller is a researcher at ETH Zurich's Flying Machine Arena.





Related posts :



A robot that finds lost items

Researchers at MIT have created RFusion, a robotic arm with a camera and radio frequency (RF) antenna attached to its gripper, that fuses signals from the antenna with visual input from the camera to locate and retrieve an item, even if the item is buried under a pile and completely out of view.
18 October 2021, by

Robohub gets a fresh look

If you visited Robohub this week, you may have spotted a big change: how this blog looks now! On Tuesday (coinciding with Ada Lovelace Day and our ‘50 women in robotics that you need to know about‘ by chance), Robohub got a massive modernisation on its look by our technical director Ioannis K. Erripis and his team.
17 October 2021, by
ep.

339

podcast

High Capacity Ride Sharing, with Alex Wallar

In this episode, our interviewer Lilly speaks to Alex Wallar, co-founder and CTO of The Routing Company. Wallar shares his background in multi-robot path-planning and optimization, and his research on scheduling and routing algorithms for high-capacity ride-sharing. They discuss how The Routing Company helps cities meet the needs of their people, the technical ins and outs of their dispatcher and assignment system, and the importance of public transit to cities and their economics.
12 October 2021, by

50 women in robotics you need to know about 2021

It’s Ada Lovelace Day and once again we’re delighted to introduce you to “50 women in robotics you need to know about”! From the Afghanistan Girls Robotics Team to K.G.Engelhardt who in 1989 ...
12 October 2021, by and

Join the Women in Robotics Photo Challenge

How can women feel as if they belong in robotics if we can't see any pictures of women building or programming robots? The Civil Rights Activist Marian Wright Edelson aptly said, "You can't be what yo...
12 October 2021, by

Sense Think Act Podcast: Melonee Wise

In this episode, Audrow Nash speaks with Melonee Wise, former CEO of Fetch Robotics and current VP of Robotics Automation at Zebra Technologies. Melonee speaks about the origin of Fetch Robotics, her ...
11 October 2021, by and





©2021 - ROBOTS Association


 












©2021 - ROBOTS Association