Crab Steering on Regolith

[sdcantrell56]

So based off of the transverse frictional value a crab drive could actually be effective. It seems like the programming might be even more difficult than a normal crab drive though to get full performance from the system.

[Otaku]

How would the direction of the wheels dictate the friction any more than normal? Technically your "contact patch " doesn't grow or shrink any, and the wheels have no lip (read: they're rounded), so you don't have any edge to dig in to.

[sdcantrell56]

That is something I dont understand either. The wheels are molded from a uniform material and there is no tread pattern so I dont see how friction would be different. Maybe it is due to the plastics grain or something like that.

[cj.reeves]

you need to use momentum sustained in an independent body from the robot and then transfer the momentum to the robot from the independent body.

[Otaku]

Originally Posted by cj.reeves

you need to use momentum sustained in an independent body from the robot and then transfer the momentum to the robot from the independent body.

You need to hit a wall or another robot?

[Dan2081]

Originally Posted by sdcantrell56

That is something I dont understand either. The wheels are molded from a uniform material and there is no tread pattern so I dont see how friction would be different. Maybe it is due to the plastics grain or something like that.

Yeah, I was playing with a wheel yesterday and the only non uniform part i noticed was the grain of the plastic, to me it seemed like there was a substantial difference between the wheel sliding inline with itself and it sliding along its axis


Well, now that I think about it, would just running your wheels backwards give u better stopping than turning your wheels sideways???

[dtengineering]

I haven't got my hands on a wheel yet, but those who have tell me that it is slightly rounded to give a "high centre".

This could cause the change in friction published in the manual section 10.2.4.1

Jason

Running the wheel backwards (dynamic inline friction... 0.5) would be worse than just turning the wheel sideways (dynamic transverse friction 0.10) according to the published values.

[Mike Schreiber]

Do you mean .05? or 0.5? for the dynamic inline friction?

Originally Posted by sdcantrell56

That is something I dont understand either. The wheels are molded from a uniform material and there is no tread pattern so I dont see how friction would be different. Maybe it is due to the plastics grain or something like that.

I'm no physics master, but I'll take a guess.

Could this have anything to do with the coefficient of static friction being greater than that of kinetic? That is, when the wheel is in the forward direction it is rolling and therefore applies static friction, while the wheel is turned perpendicular to the direction of travel it slips and applies kinetic friction. Feel free to correct me if I'm wrong.

I don't know if this theory works because the wheel may also be slipping while the robot goes forward as either way there is barely any friction.