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Bots / The Ultimate Palm Robot/ Mukhar & Johnson / 222880-6 / Chapter 2

34 The Ultimate Palm Robot

Under My Wheels

By this time you may have noticed that the PPRK only has three wheels.
(If you haven’t noticed yet, congratulations! You have the observational skills
of Dave.) That’s not such a big deal, right? Tricycles, bicycles, and three-wheel
all terrain vehicles do just fine with three wheels. The difference is that the
PPRK’s wheels are not aligned linearly; they are oriented in a triangular pat-
tern such that no single wheel lines up with either of the other two wheels!
Don’t believe us? Check out Figure 2-7.

Figure 2-7
The PPRK’s
wheels are
spaced
around the
frame of the
robot in a
triangular
pattern.

This is the point where, if you have an alter ego, it is no doubt asking you,
“Self, how does the robot travel in a straight line if none of the wheels are
aligned?” We’d like to say the answer involves ten-dimensional string theory
andquantumelectrodynamics,butintruth,theanswerismuchmoremundane.
The secret lies in the type of wheels that are used. These wheels are
designed so that they can roll along two perpendicular dimensions. When the
axle is rotating, the wheel rotates like a normal wheel, and the wheel moves,
more or less, in the direction of rotation. However, at other times, the robot
may be pushing or pulling the wheel in line with the axle. When this happens,
rollers that are embedded along the radius of the wheel allow the wheel to
move in line with the axle. In other words, the wheels can actually move

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