ply from the number of parts required
to replicate the reduction four times.
Conversely, automotive drive trains
really require only one motor to drive the
wheels by virtue of the differential. The
rack and pinion steering may also require
a separate power source to drive the
steering, but this belt-driven pump does
not need to be nearly as beefy as the
motor to drive the entire vehicle. Tank
style drives require at least two motors
of equal strength to drive each side.
Robot vs. Wild vs.
Robot
Both of our robots would need
some major modifications to be ready
to tackle the rough terrain of the
wilderness. The tank, unfortunately,
would likely need to lose the omni
wheels — the rollers that make the
wheels omni wheels would be too
prone to jamming after picking up sand
or dirt or other hazards of the wild.
The automotive bot was off to a
good start, but to go off-roading it
would definitely need to be sealed up to
protect things like gear trains from the
elements. That sounds like a lot of work,
so what’s the use of experimenting with
these drive trains on Vex robots?
The answer is that even though
Vex robots are in a totally different
arena than the super sophisticated
robots that compete in the DARPA
Grand Challenge, they are still viable
platforms for experimentation. Even
though Vex robots are vastly simpler
than DARPA bots, the same basic
principles apply to both designs.
Power transmission through a
differential abides by the same
principles whether the pumpkin is
made out of green plastic or cast iron.
And even though integrating touch
sensors with Easy C on a Vex robot is
infinitely easier than putting Lidar on
an off-road vehicle, working with
sensors and programming in the Vex
medium is still great practice.
The Vex parts are limited by their
Robot vs. Wild
regularly spaced holes and other
constraints on prefabricated parts, but
adjustable grooves and a hacksaw can
give tinkerers a little wiggle room. The
gear and omni wheel expansion sets
don’t come with instructions, but they
are easy to implement, and they really
do open up a whole new host of
possible designs with the kit.
While the roboteers working with
Vex are certainly closer to the novice end
of the spectrum and the Grand
Challenge competitors inhabit the expert
end, experts were novices once too. The
Vex Robotics Design System is a great
learning tool, and even though super
tough off-road vehicles and intelligent
autonomy aren’t very plausible, a solid
foundation in the basic principles behind
even the Grand Challenge winners is.
And a solid foundation is what is
needed for the roboteers that will build
the Grand Challenge vehicles of the
future. Who knows what grand
challenges the folks at DARPA will
come up with in the years ahead. SV
SERVO 09.2007 71
