Our resident expert on all things
robotic is merely an email away.
roboto@servomagazine.com
Tap into the sum of allhumanknowledge and get your questions answered here!
From software algorithms to material selection, Mr. Roboto strives to meet you
where you are — and what more would you expect from a complex service droid?
by
Dennis Clark
It’s May and I’m not ready for the winter to be over.
Springtime means that I need to shift into high gear to get
robots ready for school demos and upcoming summer and fall
robot competitions. Sigh, so many projects and so little time!
Enough whining. Let’s get to those projects and
questions!
Q. I have a biped robot that I’m trying to get to walk. My problem is that I have to pick it up while I’m testing a stepping gait or it might shred itself
with a movement that is too fast. I know that some kits
come with a stand of some kind to help with this. How
should I make one?
— Pete S., Denver, CO
Figure 1. Biped rack.
A. Pete, not all kits come with a stand. I have a few bipeds and only ONE of them came with a stand to test movement on. Your best and cheapest route is
good ol’ PVC pipe from your local home improvement
store. I used 1/2” Schedule 40 PVC. To build this stand, you
will need five corner joints and two T joints, along with a
single 10 foot length of 1/2” PVC pipe. I got the store to
cut it in half to fit in my car. The total cost was under $7
for all the pipe. The most expensive part was the PVC
primer and cement; get the smallest and cheapest ones you
can, it isn’t that important as long as the joints stick.
Construction is very simple. Normally, I don’t bother to
glue my PVC construction creations, but in this case, we’re
hanging a fairly heavy robot and the pipe joints will slip.
You will only need to glue the joints that
hold the vertical post (the joints marked
in purple in Figure 1).
I’ve marked my chosen dimensions
in Figure 1. They aren’t critical; just
make everything match up and be large
enough to be stable. Make sure your
vertical pipe is long enough! My first
attempt wasn’t. Figure 2 shows my
RoboPhilo hanging; it has holes on its
chassis just for this purpose. Neither my
RoboBuilder nor Bioloid have those
holes; I had to jury-rig them. I use wire
clothes hanger wire for the actual hooks.
Have fun!
Q. I have been researching robot motion — mostly what type of wheel mechanism to use. I keep
running into references to encoders that
are intended to sense how fast/far the
robot is moving.
Why not take the sensor/circuitry
from an infrared mouse and monitor it
with a low cost processor (BASIC Stamp)
Figure 2. The rack in use.
14 SERVO 05.2011
