Quote:
Originally posted by Andy Baker
M.Krass and others - I am not sure what you mean by the stall issue. This device works REALLY well when both small drive wheels are moving. The urethane ball drives nicely at a 45 degree angle, but it drives less efficiently at 0 degrees or 90 degrees. It works, but has less power. Also, at straight forward or backward, the lateral drive wheel does not spin. The main reason we decided to do this was to use the shifting gearbox for the front & back drive direction. Optimally, we would rather use 4 gearboxes (one on each aluminum drive wheel) and have each drive wheel positioned at a 45 degree angle. That way, if both wheels are turning, the robot will go straight forward and backward. But, we could not afford (weight, cost, time, etc.) 4 gearboxes. Thanks for your comments.
Andy B.
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Andy, thanks for taking the time to answer so many questions
"Stall" was probably the worst choice of words in the history of the English language, but I still can't come up with anything better. I guess that's what happens when you're discussing something that's never been seen before.
Akin to what you mentioned to JosephM. . . .there exists the possibility that the losses in the two unique components of the drive train aren't equal. That is, whatever losses the omniwheels experience in the gearing, chain, sprockets, contact with the carpet, etc. may not be equivalent to the losses that exist in the ball mechanism; the six points of contact on each ball, the gearboxes, etc.
As the ball's forward rotation is tied to the omniwheels rotation since they're in powered by the same gearbox, I was wondering how you accounted for any imbalance in losses that might exist. After all, if there are more losses on the ball than there are in the omnwheel, wouldn't it spin slower? ...and then, wouldn't it just be dragging and do nothing to "power" the robot?
It just seems like whenever there exists a chance that one "wheel" in a side of 4WD drive system might turn slower than the others, it'd be better off to make that "wheel" unpowered, or otherwise find some way to balance the losses so that they all spin at the same speed.
Does that make more sense?