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Unread 09-01-2013, 12:18
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Re: Mecanum vs Treads

Experience is important, and often trumps theory. But it is possible to go wrong tracing back from practical experience to theoretical root causes.

There are challenges in getting a holonomic drive to go straight, but they probably have more to do with how computed wheel speeds map to actual wheel speeds than with traction under low/moderate force. In particular, motors tend to be non-linear, and since holonomic drives regularly run different motors at different speeds/loads, the final wheel speeds relative to one another end up different than the ratios the drive calculations ask for.

Closed loop motor controls can prevent this problem; gyro feedback can compensate for it. Without some such mechanism, it's hard to get these things to drive straight, no matter how good the weight distribution.

Weight distribution matters (for other reasons), and driving straight is a challenge (for other reasons), but they're not linked quite so directly as it might appear.