Crab-drive steering modes?

[gorrilla]

There seems to be alot of talk going around about crab-drives...

So my team is currently working on our(first)crab drive,

We have the module itself designed and everything....

So,now we are talking about how we want to control it,
We are planning on having the 2 Left-side wheels turned by the same motor(probobly a globe) and the 2 Right-side wheels turned together,

Which would give us(we hope) 5 different steering modes out of the same setup,

1. Full 3dof Crab

2. "Long" with tank steering

3. "Wide" with tank steering

4. "Ackerman" steering(is it possible to "code" a differential?)

5. And what we have dubbed "slalom"(aka "warthog")
(In which the the back wheels would turn opposite the front)hopefully allowing the robot to swerve around in big "S bends"(I dont know if this might be as practical as we think )

I've been told controlling a crab drive is the hardest part(hopefully Im not about to find out the hard way ) but this is becoming more evident to me as we continue to simplify the modules themselves...

so basically, I was just wondering if you guys had any input on this?
(I searched around but I couldent seem to find a thread that fit)

like maybe there is an easier way to do this than we are thinking about...

Sorry, I dont have any pictures of our modules(yet )
Partly because we havent actually built them yet,but one of our mentors is trying to teach me to think things through all the way before we "just do" them(then maybe I'd loose this nickname they've given me )

any Input is helpful(wanted!!)