Linux Controlled Autonomous Vehicle (codename: "Grumpy Snail")

[wossname]

Ok for all you lot who haven't heard of it already see here: lcav.blogspot.com (http://lcav.blogspot.com)

I'm going to reserve my blog for writing things about the ideas that I'm actually going to use after careful consideration.

This thread is for general discussion and ideas, good ideas here will end up in the project and the blog. Anyone who comes up with interesting/useful ideas or helps in any other way will get credit for their contribution.

This is a non-profit project and nobody (not even me) is getting paid for it. I may even make the software open-source (and probably any CAD drawings if I get around to making any).

So anyway, read the blog and let me know what you guys think.

Cheers

Wosser.

[wossname]

Not sure if you are looking to upgrade your hardware selection but if so you could look Here (http://www.via.com.tw/en/products/mainboards/motherboards.jsp?motherboard_id=472) and Here. (http://www.via.com.tw/en/products/mainboards/accessories.jsp#power-board) That would save a lot of space and power. It can also include a watchdog for fault tolerance if you need it. If you wish to continue with the other PC then that can also be done. The options there are another off the shelf supply such as (http://www.thecarpc.com/) or I can come up with a custom design which might give some more flexibility for driving motors etc.

The low voltage circuit will be easy. Hard part there will be selecting from the multitude of solutions depending on your requirements and what is available to you.

Stepper control should also be easy depending on the number and type of motors required. The parallel port makes for the easiest interface. Software only has to control the bits on the port and the hardware only has to level shift the electrical signals. Downside is that you will only get two basic motors per port. There are options but we will need to know a bit more about the drive requirements first.


Changing my motherboard is actually highly likely in the long run especially since the low spec machine I'm running now is not optimised for battery saving. I'll continue with this machine during the software development phase at least.

In fact selecting the motherboard will likely be the last thing that happens before the whole kit is assembled ready for trials. I can do things like motor controller logic on any PC as long as it has the same ports available as the final mobo I choose.

My current thoughts on a chassis are as follows. I reckon it would be nice if I can get access to a metalwork shop for a few days so i can throw together a simple steel frame to which I can mount steppers, batteries and of course the encased computer itself. In addition to this I will need some sort of modular arrangement that will allow me to clip on/off any sensors I end up designing so they can be moved to new positions on the chassis to allow different modes of operation.

I reckon this thing will be about 10kg all in and running. So the chassis and the steppers will have to be pretty beefy. I'm not expecting this thing to break any land speed records though. I was thinking of a pair of steppers mounted side by side under the centre-of-gravity of the vehicle and a pair of lightweight 360 degree casters (front and rear) to keep it level.

[dsheller]

10 kg? Are you powering it with SLABs? Why use two motors under Cg and two casters, I'm just curious why you chose this over rear mounted motors and one caster in front.

[wossname]

See my blog for details of SLAB usage (its only a dozen or so blog entries so it won't take long).

Rear mounted motors make the robot swing around when it tries to turn. I want to be able to turn within its own footprint (like a tank).

Also having a caster that shares more than a small percentage of the weight of the robot will cause excess friction with the ground surface and will make turning jerky. Main wheels under Cg means that the casters will only ever turn when it is the trailing caster, meaning that any obstacles like small rocks will be met by the main wheels. A loaded front caster will probably slide when it hits a rock or something leading to navigation errors.