Crab-drive steering modes?

[sgreco]

Originally Posted by gorrilla

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 )

any Input is helpful(wanted!!)

If you are going to steer left and right as opposed to front and back, it's going to be a lot harder to program in a differential. Your robot will likely have to be facing sideways in this instance because your number 5 mode won't work if unless you are constantly driving sideways. Your left wheels will always be in the same diection in comparison to the other and your right side will work the same way. So number 5 can't work, because of the way you have steering set to two wheels on the same side. The wheels sharing the same side, left or right, physically cannot face in opposite directions. Your number 4 won't work either if you steer left and right, because when you turn the two front wheels to face in the same direction, your back wheels will have to move too because they are conected to the front ones. I would steer front and back, because that way, you turn the two front wheels (without steering the back) when you want steering like a car. When you want four wheel steer where the front and back wheels go in opposite directions you can do that as well. If you steer front and back it shouldn't have any difference of effect on steering modes 1,2,3. Steering the front modules together and the back modules together makes a lot more sense than left and right, given the steering modes that you want.

+$.02