[Robotgroup] Robot platforms

[vkonradi]

On these 4-wheel platforms with differential drive, the tires have to scrub a lot to turn.  On a high traction surface such as carpet this really uses up a lot of battery energy.  And it isn't nice to floors either.  On gravel for instance this is less of a problem.  The scrub turn is not so predictable, so turns aren't done on a dime.  Odometry suffers from wheel slippage.
 
Differential drive through 2 wheels does not have these problems.  The tradeoff is decreased stability, since the system has to balance between the differential pair and one or more idler wheels.  These don't do so well over big bumps and on steep hills.
 
There is also the system where you have 3 wheels all driven and steered.  I forget the proper name.  Ultimate in maneuverability, but a delicate mechanical nightmare, and priced accordingly.  In some sense the directional control is too perfect, nice as a platform for high level navigation, but too simple to use for teaching nuts and bolts of motion control.
 
In general if you are going to operate outside in sand and gravel, consider the 4-wheel.  If your work is going to be indoors, go with a 2-wheel differential drive setup.
 
Sorry, I'm not current on the larger commercial dual-differential drive setups.  I'll see what I can find.
 
Of course the Segway, though not really a great idea for human transportation, has got to be the most bitchin dual-differential drive platform available, and I'm really looking forward to when they hit the secondary market.
 
-Vadim

----- Original Message ----
From: "thecomers at juno.com" <thecomers at juno.com>
To: robotgroup at puremagic.com
Sent: Thursday, October 5, 2006 12:20:07 AM
Subject: [Robotgroup] Robot platforms


I have tentative approval to buy one or two robotic platforms to be 
used for special projects in our Robotics Fundamentals course and to 
promote the Robotics and Automation Program. I am looking for 
something more impressive than a Lego robot or BOE-bot.

I have been looking at platforms like:

the Machine Lab: the MMP-5 and MMP-8 platforms:

http://themachinelab.com/

Lynxmotion: the 4WD2 and 4WD2 platforms, and the track units:

http://www.lynxmotion.com/Category.aspx?CategoryID=30 

SuperDroid Robots: All Terrain or Heavy Duty All Terrain Robot Kit

http://www.superdroidrobots.com/shop/category.asp?catid=51

Does anyone have suggestions about other platforms to consider or 
comments about these platforms?

Thanks,
Bob Comer


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