Drones

Drone safety system stops props before they cut fingers

Drone safety system stops prop...
The prototype Safety Rotor system
The prototype Safety Rotor system
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The Safety Rotor system consists of four plastic hoops, each one surrounding one of the rotors
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The Safety Rotor system consists of four plastic hoops, each one surrounding one of the rotors
The prototype Safety Rotor system
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The prototype Safety Rotor system

If there's one thing that's scary about quadcopter drones – besides their ability to invade peoples' privacy or fall on their heads – it's those fast-spinning and potentially skin-slicing rotor blades. An experimental new system, however, is designed to stop the rotors before they can do any cutting.

Known as Safety Rotor, the system was developed by a team from Australia's University of Queensland, led by Dr. Paul Pounds.

It incorporates four lightweight plastic hoops, each one of which is mounted on one of the drone's sets of rotors, extending out to surround the rotor blades. The spinning of the rotors causes the hoops to spin with them, but because the hoops are mounted via a low-friction bearing on the rotor shaft, they don't spin as fast (or thus as dangerously) as the rotors, and can be stopped independently of them.

The Safety Rotor system consists of four plastic hoops, each one surrounding one of the rotors
The Safety Rotor system consists of four plastic hoops, each one surrounding one of the rotors

Should an appendage such as a finger accidentally wander towards one of the rotors, it will get hit by the hoop before making contact with the rotor blade itself. This causes the hoop to stop rotating, which is instantly detected by an infrared optical sensor mounted below the hoop, on the drone's rotor arm.

That sensor subsequently prompts the microcontroller driving the rotor's motor to apply an electrodynamic braking system. This will stop the blades from spinning, in less than 0.06 of a second from the time that the finger touches the hoop.

In its present form, a complete Safety Rotor setup weighs about 20 grams. It could reportedly be retrofitted to an existing drone for around AUD$15 (US$11), only minimally obstructing air flow or reducing flight time. That said, if the system were mass-produced and built into drones, it could conceivably cost manufacturers less than $5 per unit.

Pounds' team recently presented Safety Rotor at the 2018 International Conference on Robotics and Automation, and is now looking for partners interested in commercializing the system. It's demonstrated in the video below.

Source: UniQuest via IEEE Spectrum

The Safety Rotor - an Electromechanical Rotor Safety System for Drones

5 comments
Brian M
Would have been more convinced with the video if the researchers had put their own fingers in the way. The braking in 0.06 of a second (60ms) seems very optimistic especially on a larger props required for commercial sized drones (lot of energy there)
Malatrope
The finger will <i>not</i> necessarily hit the hoop before hitting a blade. It's a statistical thing and it depends on the exact timing. While this system may reduce injuries, it will not eliminate them.
Dan Lewis
It's a nice idea I'd like to see married to a clam shell like wicker enclosure for all spinning blades. Some clever wicker industry head should be working on several different sizes of easy install, easy open wicker universal drone blade protectors.
ColinPearson
Myth busters tested it and it's not required. University of Queensland should watch TV more ;-) https://www.discovery.com/tv-shows/mythbusters/videos/drone-decapitation-high-speed
Gregg Eshelman
This is an extremely over-engineered solution, and has the problem that the hoops won't always be in contact with an unexpected intrusion before the prop blade. What would have a 100% safety contact first result is to have the hoops in a fixed, leading, relationship to the props. Upon contact, the hoop is stopped and actuates a mechanical clutch to disengage the prop from its shaft. It could also incorporate a brake, on the opposite side of the clutch. No extra electronics required, no extra electronics to take flight time from the battery, or potentially fail - to operate or to false positive and wrongly stop a motor when there's no obstruction.