Crab-drive steering modes?

[sgreco]

Originally Posted by gorrilla

why do we actually need these?

Couldent we just use limit switches on each module? since the 2 wheels on each side are linked together,

Like in full-crab mode, have one joystick for "gas" and one that turns both sets of wheels the direction you point it? and the same for "ackerman"and "Slolam" modes?

And maybe have something coded so they return to the middle if you let off the sticks?
or is there something im missing?

also what motor could we use to turn the modules? ive seen alot of teams use globes,but they're not the fastest thing...only 100rpm

You could get away with limit switches, but the modules won't center unless you have feedback sensors. If you want a limit on both sides and one to find center, that's 3 sensors and at that point, it's probably easier to just use a rotational sensor. My team finds that it is a little bit easier to use rotational sensors because that way one sensor takes care of every angle. It also makes driving with precision to certain angles easier. If you use switches, the robot won't know where the wheels are pointing when they aren't touching a limit switch, and if you have wheels pointing in slightly opposite directions, it can be a problem when trying to go straight. It may not seem that bad, but it can turn into a problem.

As for motors, my team has used the window motors the past two years, but they're kind of weak. I would use globe motors, they should work just fine. If you are really careful about friction between the module and the ground and the bearings that support it, you should be able to gear globes to be fast enough. You could also use FPs. They require a lot of reduction, but are more powerful than globes. The only reason I wouldn't use FPs is because they are typically good to have for game piece manipulation.