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Unread 09-12-2009, 23:09
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Re: crab drive vs. mecanum drive system

Quote:
Originally Posted by superbotman View Post
My team is debating on the drive system we want to use and I thought I would ask what has worked well for other teams.

1. Crab drive works best

2. Mecanum drive with each wheel having its own motor wins.

3. Use mecanum drive with one motor per side.

4. don't do any and use some other drive system
On a purely strategic level: (i.e. if you have a robot with a "perfect" crab drive and "perfect" mecanum drive side by side and you're deciding which to play in a match, in a fantasy scenario) A crab drive achieves omnidirectional motion while maintaining closer to 100% of motor force in the desired direction of movement, and with the benefit of traction in all directions to prevent easy pushing and spinning. A mecanum system achieves omnidirectional movement without module rotation at the expense of some motor efficiency (going straight forward only uses ~70% of motor force) and less traction / more vulnerability to being spun.

Basically, a perfect crab is almost always better than a perfect mecanum. That said, omnidirectional motion isn't always required or optimal, and there are tradeoffs to using crab over a standard 6 wheel (mainly in turning, weight, etc) that make the decision nontrivial.

And that's putting the building of said robots aside. Crab is very difficult to build for and even harder to program with. Mecanum is less challenging and if things go wrong you can theoretically just drop in 4 normal wheels.
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