Wearables

Smart ring tech magnetically tracks its user's finger

Smart ring tech magnetically t...
The AuraRing prototype, seen here being used to hand-write a simple message
The AuraRing prototype, seen here being used to hand-write a simple message
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The AuraRing prototype, seen here being used to hand-write a simple message
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The AuraRing prototype, seen here being used to hand-write a simple message
The AuraRing, with the wristband visible in the background – the copper wire is wrapped around the ring 800 times
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The AuraRing, with the wristband visible in the background – the copper wire is wrapped around the ring 800 times
A closer view of the wristband – the white square at the left is one of its three sensors
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A closer view of the wristband – the white square at the left is one of its three sensors
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Although there are already complex prototype interfaces that track all five of the fingers on a computer-user's hand, let's be honest – it's mostly just the index finger that matters. That's where the experimental AuraRing system is designed to come in.

Developed by a team at the University of Washington, AuraRing consists of two parts: the index-finger-worn ring itself, and an accompanying electronic wristband worn on the same arm.

The ring is in turn made up of a 3D-printed body, around which is wound a coil of copper wire. A current running through that wire generates an oscillating magnetic field, which is picked up by three sensor coils in the wristband. As the finger moves, the voltage that's induced in each of those coils changes.

Therefore, by continuously comparing the voltage in the three sensors, the system is able to ascertain where the ring is relative to the wristband, and thus the position of the finger that's wearing the ring. Additionally, the system can detect distinctive finger movements such as taps, flicks and pinches. The current prototype has a sensor resolution of a tenth of a millimeter, and is typically accurate to within 4.4 mm.

The AuraRing, with the wristband visible in the background – the copper wire is wrapped around the ring 800 times
The AuraRing, with the wristband visible in the background – the copper wire is wrapped around the ring 800 times

"To have continuous tracking in other smart rings you’d have to stream all the data using wireless communication. That part consumes a lot of power, which is why a lot of smart rings only detect gestures and send those specific commands," says doctoral student Farshid Salemi Parizi, co-lead author of a paper on the study. "But AuraRing’s ring consumes only 2.3 milliwatts of power, which produces an oscillating magnetic field that the wristband can constantly sense."

Already, the system has been successfully used for tasks like hand-writing simple messages, and selecting objects in virtual reality environments.

Down the road, the wristband electronics could conceivably be incorporated into existing smartwatches, with the actual ring being the only piece of extra hardware required. The technology might then find use in applications such as controlling wirelessly-linked smartphones, relaying movements to video game avatars, or even assessing hand tremors in people with Parkinson's disease.

The paper was published last month in the journal Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies – its other co-lead author was doctoral student Eric Whitmire. You can see a demo of the AuraRing system, in the following video.

Source: University of Washington

AuraRing: Precise Electromagnetic Finger Tracking

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