Tech Briefs Magazine - October 2021 - MD-18

With existing prosthetic devices, electrical
measurements of a person's muscles
are obtained using electrodes that
can be either attached to the surface of
the skin or surgically implanted in the
muscle. The latter procedure is highly
invasive and costly but provides somewhat
more accurate measurements. In
either case, electromyography (EMG)
offers information only about muscles'
electrical activity, not their length or
speed.
The new strategy is based on the idea
that if sensors could measure what muscles
are doing, those measurements
would offer more precise control of a
prosthesis. To achieve that, the re -
searchers inserted pairs of magnets into
muscles. By measuring how the magnets
move relative to one another, they
can calculate how much the muscles
are contracting and the speed of contraction.
For
control of a prosthetic limb, these
measurements could be fed into a computer
model that predicts where the
patient's phantom limb would be in
space, based on the contractions of the
remaining muscle. This strategy would
direct the prosthetic device to move the
way that the patient wants it to, matching
the mental picture that they have of
their limb position. Through mathematical
modeling of the entire limb, the
researchers can compute target positions
and speeds of the prosthetic joints
to be controlled and then a simple
robotic controller can control those
joints.
The researchers envision that the sensors
used to control the prosthetic limbs
After inserting small magnetic beads into muscle tissue within the amputated residuum, researchers can precisely
measure the length of a muscle as it contracts and this feedback can be relayed to a bionic prosthesis within milliseconds.
(Courtesy of the researchers)
could be placed on clothing, attached to
the surface of the skin, or affixed to the
outside of a prosthesis.
MM could also be used to improve
the muscle control achieved with a
technique called functional electrical
stimulation, which is now used to help
restore mobility in people with spinal
cord injuries. Another possible use for
this kind of magnetic control would
be to guide robotic exoskeletons,
which can be attached to an ankle or
another joint to help people who have
suffered a stroke or developed other
kinds of muscle weakness.
Essentially, the magnets and the exo -
skeleton act as an artificial muscle that
will amplify the output of the biological
muscles in the stroke-impaired
limb. Another advantage of the MM ap -
proach is that it is minimally invasive.
Once inserted in the muscle, the beads
could remain in place for a lifetime
without needing to be replaced.
For more information, contact Abby
Abazorius at abbya@mit.edu; 617-253-2709.
Faster Path Planning for Rubble-Roving Robots
In a collapsed building or on rough terrain, a robot could balance itself and move forward with just
its feet.
University of Michigan, Ann Arbor
Robots that need to use their arms to
make their way across treacherous
terrain are being equipped with an
algorithm that found successful paths
three times as often as standard algorithms,
while needing much less processing
time. The new algorithm
speeds up path planning for robots
18
Cov
ToC
that use arm-like appendages to maintain
balance on treacherous terrain
such as disaster areas or construction
sites.
The research enables robots to de -
termine how difficult the terrain is
before calculating a successful path
forward, which might include bracing
on the wall with one or two hands
while taking the next step forward.
Machine learning was used to train the
robot on different ways it can place its
hands and feet to maintain balance
and make progress. Then, when
placed in a new, complex environment,
the robot can use what it
Motion Design, October 2021

http://info.hotims.com/79418-936

Tech Briefs Magazine - October 2021

Table of Contents for the Digital Edition of Tech Briefs Magazine - October 2021