Engine Choice & Speed

Hi Everybody
Although I'm new to Arduino and only 17 I signed up for a robotics competition with a friend that is turning out to be a little more complex than we first thought. In a nutshell, we have to go around a 3m square and collect candle-light sized 10 colored wooden chips and bring them back to ''base".

I happened to have a 10 year old Boe-Bot from school and the first question was if we could modify it... but no matter how we tested around with the code, we couldn't make it go quicker than like 20 cm/s, which was slower than some of last year's competition according to YouTube. So the question is:

  1. can we drive a small robot with an arduino uno and a battery pack run up to 50 cm/s (think it's around 20 inches/s) with Servos?
  2. Is there a better alternative and in which case what would it be? Traditional DC engines, we also have a few old stepper engines in school

we have access to a laser cutter and a milling machine, so we were thinking of building a new chassi from scratch.

any help is greatly appreciated :slight_smile:

can we drive a small robot with an arduino uno and a battery pack run up to 50 cm/s (think it's around 20 inches/s) with Servos?

With the right servos and the right batteries, yes. Servos are not really designed for speed, though. Using geared motors would result in a faster robot.

Is there a better alternative and in which case what would it be?

Yes. Geared motors.

manfredj:
Is there a better alternative and in which case what would it be? Traditional DC engines, we also have a few old stepper engines in school

Nitpick: They're called "motors" - not "engines"; then again, depending on where you're at in the States, an engine is sometimes called a motor - why this is, I don't know. All I do know is that when I think about an "engine" - I think "steam", "internal combustion", "external combustion", and "jet"; while when I think about the word "motor" - I think "electricity of some sort involved"; of course, all of that get's confused when you bring in ideas like "pneumatic engines" and "water motors"...sigh. :slight_smile:

Something to keep in mind for your project (learned from participating in engineering competitions when I was in high school):

Think smarter, not harder (providing no explicit rules of the competition are broken): Long before there was public access to the internet, I was involved in a competition to build what was called a "golfapult" (basically a catapult to launch a golf ball); there were two main challenges - distance (long range) and accuracy (short range).

The machine had to fit in a "box" of 1 foot to the side (no metric here!), and use only stored potential energy.

I unfortunately didn't pay close attention to the rules (that is, where the loopholes were), and so built my machine to those specs. I learned two things at that competition:

  1. Read the rules carefully (apparently it was legal to use latex rubber tubing as a launch mechanism - even if it stretched several feet from your machine), and
  2. Think outside the box (in the adult/college playfield, people built some amazing pneumatic launchers using small propane tanks and ball-cock valves).

I did, however, manage to beat the majority of entries in the accuracy portion, as my machine was waaay underpowered - whereas the over-powered entries tended to have problems.

Something tells me such a similar thing may apply in your situation (and had been done in the past); I was involved in a different competition where the goal was to move a small mass so many meters, and stop as close to the end point as possible; go over, you lose points - go under, you lose points. The faster you got there, the better (but you'd better be able to stop. That year I paid better attention. My machine used a simple rubber band, and I would wind it up the -exact- distance needed to the "line". Worked every time, and I placed fairly well (and later placed using the same machine for my Physics Day contests in school).

In the adult/college/open tier, though, was a guy we all thought would sweep the competition (for his tier). His machine used a stepper motor, and 555 timer plus some other electronics to act as a counter; He would just sit his down, punch in the numbers, and away it would go - dead stop every time, at least in the trial runs. When it came time for his turn, his machine failed, and kept moving along, and he had no way to fix it. He was so sure he would win, that he forgot to bring tools, a backup, etc. Not only that, but his machine was overly complex (being electronic/electrical - which in the open tier you could do), and thus couldn't be easily repaired "in the field" without those tools.

So keep that in mind as well: Sometimes simpler is better. You might be able to come up with something that uses little or no code (or extremely "dumb" code) to accomplish the task whereas others try to do something much more complex, getting lost in the complexities where simpler solutions work better (check out the history of the first "micro-mouse" maze-running competitions in the early 1970s; a very dumb "mouse" beat out the more complex entries - theres also a similar situation in the old "game" called "Core Wars"; if I remember right, one of the best "programs" was a fairly simple piece of code, but in that simplicity could beat much more complex entries).

Good luck with your robot and your competition!

:smiley:

All I do know is that when I think about an "engine" - I think "steam", "internal combustion", "external combustion", and "jet"; while when I think about the word "motor" - I think "electricity of some sort involved";

I would agree with that, but originally (apparently) the word motor was used to describe the first internal combustion engine powered vehicles, as distinct from steam powered ones.

A servo can be speed hacked like below to increase the rotation speed. As to "motor", I always understood that the term derived from the "motive" part of EMF that makes it work.