Re: Testing a Theory, by Pete
Smith in the March 2015 Combat
I really appreciate that Mr. Smith
took the time to document his work,
even though it ended in failure. If I
may offer some experience: Brushless
motors require active commutation
and are typically servoed in speed
mode; that is, the R/C signal into the
controller commands an RPM.
The odds of all three controllers
matching is low, so ultimately one
motor strayed, the belt jumped a
tooth, and then catastrophically failed.
The solution to ganging servoed
motors is to use torque mode, one
domain lower in the control system.
It's akin to riders on a tandem
bike where each rider varies their own
effort to match a desired speed, and
what you do with the gas pedal of
your car to reach a desired MPH.
Dan, thanks for the advice on
how to help make multiple brushless
motors work together. The cheap
hobby ESCs do not offer "torque"
mode, however, so a solution at a
reasonable cost may still be elusive.
Hey! I wanted to say that the
FIRST Things First article written by
Aleksandr Savchenkov way back in the
November 2014 issue was a great
idea! I read the article and thought
the project was awesome. I am also a
high school student and it just so
happens that we are in the process of
building a life size robot. I showed my
teacher what Aleksandr did and he
wants to do it! Great work, man!
FINALLY! An article about one of
my favorite books by David Heiserman
(refer to Camp Peavy’s article in the
February 2015 issue; you’ll find Part 2
in this magazine). I have always been
curious how Heiserman's algorithms
would translate to modern hardware.
Looking forward to building this bot.
Techie67 via email
SERVO 05.2015 7
Kokomo, Indiana • www.AndyMark.com • 877-868-4770
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PCNC 1100 Series 3
Shown here with
Shown below is an articulated humanoid
robot leg, built by researchers at the
Drexel Autonomous System Lab (DASL)
with a Tormach PCNC 1100 milling
machine. DASL researcher Roy Gross
estimates that somewhere between 300
and 400 components for “HUBO+” has
been machined on their PCNC 1100.