DPRG mailing list archives: [DPRG] Robot platforms

Thu Feb 22 17:00:34 CST 2007

Hello,

I would like to second this approach of off-the-shelf vehicle
platforms. For me, it has been a very different experience
from a fully custom build. Please allow me to elaborate.

Last month, I picked up a $15 RC toy car from Walmart. One
month later, the radio and motor control are fully hacked with
an ARM9 single board computer inside (software will take
months more work, though). This did not require many
sleepless nights of work either. The only machine tool needed
is a mill/drill press to modify a SPST switch with an extra
terminal (so as to pull three IC pins to ground when pressed).
But otherwise, everything was done with hand tools.

So last night I am in a parking lot walking beside the robot car
and driving it with the remote. There is no way I could make
something like this from scratch in a month. I don't think it
will take very long to add semi-autonomous and fully autonomous
capability either. The reason is that everything just works so
software development is more about control and intelligence
rather than uncovering design flaws in the electro-mechanical
systems.

It is really astounding how much faster this approach is.

And it can be cheaper too. The $15 RC toy car has around $300
more invested into it. Most of that is a $200 ARM9 single board
computer. But I think it is possible to go much cheaper with
the same approach. I only need the computer as this robot is
for testing computer vision ideas.

With a microcontroller, I think that it is possible to hack a RC
toy for a total cost of $50 to $100. That includes a remote
control. One advantage of the cheap non-proportional RC toys
is that no PWM or PWPS pulse modulation is required for motor
or servo control. The combination radio and motor control board
can be hacked and a microcontroller connected to it directly or
through a buffer. You don't even need a new power supply. Just
use the supply on the toy's own electronics board (probably is 4
volts?). You'll have to solder wires onto the underside of the toy's
electronics board and use a knife to break some circuit traces. I
must admit this is pretty fiddly. But it is not that difficult to do.

Sure, such a robot is limited. But I believe that non-proportional
steering can be enough. Things like laser-guided bombs make
due with bang-bang control. It can work. There is one major
downside though - no encoders so no odometry without work. If
your control strategy relies on bump switches, IR range sensors,
SONAR or computer vision, then this might work for you anyway.

Chris

-----Original Message-----
>From: "David P. Anderson" <dpa at io.isem.smu.edu>
>Sent: Feb 22, 2007 11:49 AM
>To: dprglist at dprg.org
>Subject: [DPRG] Robot platforms
>
>Howdy
>
><http://www.superdroidrobots.com/ATR.htm>
>
>has some interesting pre-built robot platforms,
>for those who might like a leg up on the mechanical
>end of things.
>
>dpa
>
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