pic: What's going on here?

[gblake]

Originally Posted by CraigHickman

While your concerns are valid, you're skipping a few factors. One being traction control, which will be clarified once we get it working. Another being individual wheel power. Individually powered wheels will be able to "power through" turns, much akin to an all-wheel drive car, or a vehicle with sufficiently advanced traction control.

A decently intelligent thing to do with a crab in Lunacy would be to keep the bot in 4 wheel steering mode, and have it act like a car. This allows for the options of doing "crab" (or side to side) motions whenever the situation requires it. A simple combination of a gyro and individual wheel motors will allow a crab to go in any direction regardless of the trailer.

I am focusing on the situation where a bot in motion wants to change its trajectory.

Driving in a in a straight line, traction control (keeping the torque on the wheels less than the torque that will cause them to begin to slip) does sound like a useful thing.

But any attempt to orient those wheels non-trivially away from the bot's motion vector means they have to (and most certainly will) start slipping sideways. Maybe I am wrong, but I'm thinking that if you are slipping sideways, traction control will be dealing with the slipping coefficient of friction, not the static one; and that will put a big crimp in its usefulness during turns.

Eventually the bot will stop sliding sideways and the traction control can be used to move efficiently in the direction the wheels are pointing now.

I can see that a crab drive might turn you a bit more tightly or quickly, but you can still color me dubious that a crab system will be worth the trouble and weight.

Separately, if a bot is standing still and uses a crab drive to head sideways from a standing start, I can see some advantage accruing to a team that needs that motion to carry out their strategy and builds a crab drive. I can also see the trailer wrecking havoc on any attempt to drive a crab sideways without having your wheels slip sideways (away from the direction you point them).

Blake