Tech Briefs Magazine - June 2024 - MD3

Birmingham, which has a specialty in
rail research. That academic concentration
led to the school's ingenious " blue
sky " research idea: Could there be a way
to measure the microgravity of a specific
point and, from those measurements,
construct a topographical map of the
world that could rival and potentially
replace the GPS system, if needed?
Furthermore, could those measurements
be taken from a moving train as it
crossed the land?
With such a grand scope, the line between
" blue sky " and " pie in the sky "
might be invisible. And that was before
contemplating the equipment involved.
Paul Riley explained, " Researchers
used to measure gravity by dropping a
ball, then another ball, and then, if you
could measure the acceleration between
the two, you could get an idea of
gravity. They could measure to an accuracy
of maybe times 10-4 to 10-5. But
now they have a new gravity system
where they take cold atoms in superposition,
position them with magnetic
fields,
and do essentially
the same
thing. They're dropping atoms and
measuring how far they've fallen with
lasers. The results are so precise that
they can get a gravitational 'fingerprint'
of an area. "
However, imagine trying to take such
atomic-level readings with apparatus on
a moving train (or an aircraft, which is
also in planning). Keeping the equipment
level would be like balancing a
brimming glass of water on a tray while
hurtling over rough terrain, only orders
of magnitude worse. The person holding
the tray would require superhuman
reflexes and precision.
Riley had worked with Delta Motion
on prior projects and expected they had
the expertise that it would take to successfully
tackle the train problem. His
initial concern was that many of the applications
for Delta's products revolved
around hydraulic motion control and
Riley expected that hydraulics would be
too large for the confined space of the
rail car or aircraft fuselage. After a little
more research, Riley was happy to find
that Delta's RMC motion controllers
were capable of precision control of the
electromechanical
actuators
that he
wished to use. His final concern was that
the magnetic fields of the electric motors
would interfere with the sensors
that measure and map the gravitational
Motion Design, June 2024
CCS Stewart platform - 6 DOF. (Image: Delta Motion)
The inverted Stewart platform devised for the terrestrial gravity mapping DOF 2 application. (Image: Delta
Motion)
field. After testing it was determined
that this would not pose an issue.
Any solution was likely to require
active stability to maintain a level system
during travel. Riley was very well
acquainted
with
Stewart
Riley knew from previous experience
platforms,
which often provide the six degrees of
freedom needed for platform-based
movement - much like our hypothetical
water tray.
working with Delta Motion that Delta's
expertise extended well beyond simple
point-to-point motion. For example, the
company had worked with controlling
Stewart platforms in applications such as
automotive testing and even in filmmaking,
where actors would jump onto a
platform that mimicked the action of a
moving vehicle. Riley suspected that the
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Tech Briefs Magazine - June 2024

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