Books like "Build Your Own All-Terrain Robot"?

I haven't seen the book, but I've chatted with the author Brad Graham a couple of times when he was active in the Yahoo robotics group. He's into things like custom bikes and teraring apart Buick differentials, home-based welding, and other related stuff. From what I can see, he's not as much into the technical end of selecting motors based on torque, power, and what-not.

If you analyze the problem, though, I think you'll find some suitable books that cover what you need. They just go by different names. For example, Pete Miles and Tom Carroll wrote an excellent book on building combat robots that does discuss motors, batteries, control circuitry, and many of the topics you'd like covered, and for robots in the same weight/size class as the ones in Brad's book. Seems to me that an all-terrain robot is about the same as a combat robot, but without a weapon.

To answer your question regarding DC or stepper motors: A stepper motor would be inapporpriate for an outdoor robot on uneven terrain. You want a honking DC motor with a solid all-metal gearbox.

Finally, try to catch the eye of Jay Newman here. He's into building bots with Mini-ITX boards, and is familiar with many of the issues involved.

-- Gordon Author: Constructing Robot Bases, Robot Builder's Sourcebook, Robot Builder's Bonanza

Matt Dibb wrote:

Thanks Gordon.

I liked the All-Terain Robots book, and my next large bot will be based on a used motorized wheelchair I bought.

My only problem is that I can't weld.

The problem with combat robots is that they are built to run for about five minutes, which means they usually have oversized motors, undersized batteries, and are usually too low to the ground for my taste.

Though I've read most of the combat robot books to get an idea about how they were built. And the reading was worth it.

The Mini-ITX boards are very nice. I run Gentoo Linux on mine with a couple of CF cards as disks. I'm still working on building a good I/O processor.

-- D. Jay Newman

Yes, one must extrapolate from the basic info that's in these books to build a general-purpose outdoor robot. Still, I think Pete and Tom do a good job in explaining how to calculate torque and power requirements for any motor, and they discuss the battery drain issue as well.

It's been a while since I read it, but I think Pete's book describes some basic measurements using wheelchair motors, which are basically going to be the standard for the average outdoor robot. When not re-wound to produce a higher speed (and higher curreent) I think most of these will function well for an all-terrain robot with a between-charge life of at least an hour. Otherwise they wouldn't be too useful as wheelchair motors...

NPC's site is a pretty good one for the basic parts, if you don't want to hunt arount. At $150-250 per motor I know I can't afford these (and they're rebuilds, from what I understand), but they seem pretty nice.

-- Gordon Author: Constructing Robot Bases, Robot Builder's Sourcebook, Robot Builder's Bonanza

Diverse Electronic Services

has wheelchair motors for about $100. They also have all the necessary electonics to drive them at reasonable prices.

-- D. Jay Newman

And somewhere around the time of 06/22/2004 17:02, the world stopped and listened as D. Jay Newman contributed the following to humanity:

Dumb question. What's a mini-ITX board? Is it some sort of SBC?

Its a fully function "mini" motherboard - rather like a shrunken down one you'll likely be able to find in a desktop PC. Benefits are that they are only 17cm by 17cm and generally consume on a very small amount of power.

They are pretty cute, but pretty expensive too. This page has some more information (and they also sell the boards too):

also sell the boards. Note that the CPUs included may be rated at 1GHz, but their performance is equivalent to something like a 600 or 700Mhz Celeron in "real world" applications.

Matt

A Mini-ITX board is a small PC motherboard form factor that is around 7.5 * 7.5 inches. VIA seems to be the main ones pushing these. They are a complete PC, with video, audio, and USB.

VIA makes most of them with low-power processors, some even for fanless operation.

You can see why these would be useful for robotics.

With the use of compact flash cards instead of hard-dirves the power consumption is minimal.

The next generation is the Nano-ITX form factor, which has a 4" * 4" footprint.

-- D. Jay Newman

Sounds very nice - do you know if any of these allow a single supply power input? The only major downside I can see to these boards is the ATX power supply with all those voltages.

The Nano-ITX board looks very nice. The photo I saw was not that great so I can't tell what kind of power connection it has. Maybe it just wants +5V :-)

-Brian

If you wanna see a complete overview of all available mini-itx maonboards, try this:

Sascha

There is a particular model that takes a single 12V input (it has an onboard DC-DC converter) which was designed for use in cars and so on, which I expect would be useful for robotics.

There are simple little DC-DC converters that plug directly into the ATX power socket which could be used also - the one that everyone seems to use/talk about is here:

That uses a "nano-atx" power connector or something - not sure what the inputs are but it looks like it needs a "real" power suply rather than just a single input.

Matt

Neither can I, so I use nuts, bolts, angle brackets, and other common hardware instead.

The gussetted plastic angle brackets sold on Gordon's website are lightweight and strong, and I'm finding more and more uses for them. They can even be used with no mounting hardware and no holes. Degrease the mating surfaces with rubbing alcohol, rough them up with sandpaper, and apply JB Weld (steel-filled epoxy). Wiggle the bracket as you push it firmly into place to ensure the epoxy gets into all the nooks and crannies. I used this a lot in a recent project, and the joints were strong enough to survive an accident which bent 1" x 1/8" aluminum angle.

Chris

Neither can I, so I use nuts, bolts, angle brackets, and other common hardware instead.

The gussetted plastic angle brackets sold on Gordon's website are lightweight and strong, and I'm finding more and more uses for them. They can even be used with no mounting hardware and no holes. Degrease the mating surfaces with rubbing alcohol, rough them up with sandpaper, and apply JB Weld (steel-filled epoxy). Wiggle the bracket as you push it firmly into place to ensure the epoxy gets into all the nooks and crannies. I used this a lot in a recent project, and the joints were strong enough to survive an accident which bent 1" x 1/8" aluminum angle.

Chris

DC-DC converter) which

Note that some of the 12-V to Mini-ITX power supplies are rated for

12V +/- 0.5V rather than "I stuck a lead-acid battery on this".

socket which could be

That one claims 12v +/- 15%, which is *much* nicer.

cheers, Rich