advices needed on chassis for mini itx powered robot

[zeograd]

Hi all,
  this is my first post so I hope I'm doing it right.

I want to build a small robot based around a mini itx pc motherboard. I have good software skills (doing linux kernel programming for living and developping for 20+ years in C, asm, ...) but I'm new to robotics itself.
I would like to be able to mount a mini itx mobo on a wheeled platform and only focus on sensor and dc driving and not much motor choice/mounting and the like.
My goal would be to prototype an indoor robot doing location and mapping thanks to computer vision mainly.
After reading the linux robot book from D. Jay Newman, I thought that the platform used in this book was suitable for me ( https://www.zagrosrobotics.com/shop/item.asp?itemid=519&catid=1 ). I would then add either phidgets or axon,... to read sensors via usb and actuate via a serial or usb driven H-bridge

My problem is that Zagros does not seem to ship internationally for a reasonable price (ie for the parts I needed, I ended up with a 260$+ S/H fee) and they don't seem to have resellers.

I was then looking for other potential mobile robot platform, but I either found smaller, 4WD chassis, like from lynx motion, or "clunkly" looking ones in robotshop ( http://www.robotshop.ca/base-mobile-hcr-dfrobot-1.html ).

I don't recall seeing in the forum someone else using mini itx mother board to build a robot around, but you probably have some ideas on which mechanically-ready chassis could be use to support this.

Thanks in advance,
Olivier

[blackbeard]

to start with you're going to need a power source. for this the easiest thing would be to run it on the smallest possible psu and run an inverter. that whole setup alone would likely be too big for that platform anyway. luckily you can make your own very easily and for less then a third of the price. the chassis can be made from plywood in a pinch but you can get acrylic in most major cities which is what all those chassis are made of anyway. making your own will also save you the trouble of making a pre built chassis compatible. motors are pretty cheep too and you can get them pretty much anywhere. the easiest way i can think of would be to get gear motors between 30 and 60 rpm and run them off a pre built motor controller. others might suggest servos which may also work (if they're big enough). the simplest positioning of the motors is to have 1 motor for either side and a swiveling wheel in the front like below. for controlling it you can probably use the same principal as the many laptop based robots

[madchimp]

to start with you're going to need a power source. for this the easiest thing would be to run it on the smallest possible psu and run an inverter.

You can get a psu that runs off DC so that you don't need the inverter which just adds extra weight and cuts into the efficiency of you power system.

[blackbeard]

to start with you're going to need a power source. for this the easiest thing would be to run it on the smallest possible psu and run an inverter.

You can get a psu that runs off DC so that you don't need the inverter which just adds extra weight and cuts into the efficiency of you power system.

ya that's probably more efficient. i've only seen them for nano and pico itx though but i'm sure they're out there

[Ro-Bot-X]

I have an old Via Epia Mini-ITX motherboard (800MHz) that is powered by a DC-DC ATX power source and takes 12V DC input. So there are adequate solutions for any kind of boards. I also have that book you mention but Linux is not my forte (neither is programming computers) so I didn't do anything usefull with it. I did use the motherboard for my Eric butler robot, but I got stuck at programming. Eric uses a ER1 kit for locomotion, so I didn't need to buy a base, but I decided that I will try to build a new base anyway and use geared DC motors (with encoders) instead of steppers. A Sabertooth would work fine but I am still debating what motors should I use, since I still am not sure what force they will need to put out. It all depends on what the bot will be required to do and that is not yet set in stone. I want fast motors ( I will halve the speed by using toothed belt and PWM) because I want the bot to be able to walk with me (bot at top speed) and I also want it to be able to climb regular inclines for handicapped people. As for the base, I am looking at baby strollers, some of them have nice tripod like chassis with inflatable wheels and a caster, I'm amazed nobody used one yet for a robot.

So it all depends what you want your bot to do or to look when is done.

Also check these projects:
http://leafproject.org/
http://www.linuxpcrobot.org/
http://oap.sourceforge.net/

[zeograd]

Thanks for all your answers.
  For the PSU, indeed, I'll use a DC-DC converter ( http://www.mini-box.com/s.nl/it.A/id.417/.f?sc=8&category=981 ). So I can put 12V batteries on it and still power the mother board correctly.
  I've checked the chassis of the 3 projects mentioned : The leaf project uses a custom made base that I wanted to avoid due to my poor skills, same goes for the linuxpcrobot. The oap project also uses a prebuilt base from Zagros...
  So, I guess I'll give a try building my own, thanks to your advises.
Take care,
  Olivier

[blackbeard]

Thanks for all your answers.
  For the PSU, indeed, I'll use a DC-DC converter ( http://www.mini-box.com/s.nl/it.A/id.417/.f?sc=8&category=981 ). So I can put 12V batteries on it and still power the mother board correctly.
  I've checked the chassis of the 3 projects mentioned : The leaf project uses a custom made base that I wanted to avoid due to my poor skills, same goes for the linuxpcrobot. The oap project also uses a prebuilt base from Zagros...
  So, I guess I'll give a try building my own, thanks to your advises.
Take care,
  Olivier

oh don't worry about skills! just measure often and you're likely not going to make a mistake. even a hand saw can cut lexan