Researchers at The Human Computer
Interaction Lab at Hasso-Plattner-Institut in Potsdam, Germany, proposed a
novel solution to the problem of wearable haptics for augmented reality. Using
a lightweight, mobile electrical muscle stimulation (EMS) device that provides
low-voltage to arm muscles, the idea is to let AR headset-users stay
hands-free, but also be able to experience force-feedback when interacting with
virtual objects, and feel extra forces when touching physical objects in their
environment too. Using a HoloLens headset, researchers show their proposed
solution in action, which is made up of a backpack, a laptop computer running
Unity, a battery-powered EMS machine, electrode pads, and visual markers to
better track hand gestures. The researchers say their system adds physical
forces while keeping the users’ hands free to interact unencumbered. The
EMS-based system actuates the user’s wrists, biceps, triceps and shoulder
muscles with a low-voltage to simulate a sort of ‘virtual pressure’. This
perceived pressure can be activated when you interact with virtual objects such
as buttons, and even physical objects like real-world dials and levels to
create an extra sense of force on the user’s arms.
There are some trade-offs when
using this sort of system though, making it somewhat less practical for
long-term use as it’s configured now. Two of the biggest drawbacks: it requires
precise electrode placement and per-user calibration before each use, and it
can also cause muscle fatigue, which would render it less useful and probably
less comfortable. But maybe a little muscle stimulation can go a long way. The
paper discusses using EMS sparingly, playing on the user’s keen sense for
plausibility while in a physical (and not virtual) environment. It’s an
interesting step that could prove effective in a multi-pronged approach to
adding haptics to AR wearables, the users of which would want to stay
hands-free when going about their daily lives. Actuator-based gloves and vests
have been a low-hanging fruit so far, and are quickly becoming a standard go-to
for VR haptics, but still seem too much of a stretch for daily AR use.
Force-feedback exoskeletons, which stop physical movements, are much bulkier
and are even more of a stretch currently. There’s no telling what the
prevailing AR wearable will be in the future, but whatever it is, it’s going to
have to be both light and useful—two aspects EMS seems to nail fairly well out
of the gate.
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