[EricH]

Originally Posted by Alan Anderson

Drive systems using Mecanum (note spelling) wheels are holonomic (note spelling). The only real difference between Mecanum and omniwheel systems is in the orientation of the axles. Nearly everything else can be analyzed identically. For example, I don't see how a Mecanum wheel sees greater side forces than a traditional omniwheel. Can you explain your reasoning more completely?

I think I see where he's coming from.

Mecanum:

/// \\\ or \\\ ///
\\\ /// /// \\\

depending on how easily you want to turn.

Omni (45-degree setup):

----
l l
l l
l l
----

The mecanums are always pushing, but a lot of the force is directed sideways by the rollers. However, omni's are often off, so their rollers take the load. The pushing omni's are only pushing one direction. For a mecanum, they are pushing in two directions, unless the robot is moving diagonally.

Some other things to take into consideration: how easy is it to push you? Omni's are a little easier (two-wheel drive in any given direction save diagonal). Mecanums may be set up in two orientations ("easy-spin", which looks like an X, and "hard-spin", which looks like an O) and are harder to push because you have to fight all four wheels.

Ease of building: Mecanums are easier to build. Given four AM planetaries, a set of mecanums, and a kit of parts, it is possible to put one together other than programming in about an day. Omni's need a custom(ized) frame.

Maneuverability: there is a slight difference (I think). Mecanums may be programmed to allow turning while strafing, enabling large arcs. I'm not sure an omni-wheeled robot can do that without spinning.

Traction: Most teams that use mecanums have relatively high-traction rollers (often rubber). Most teams that use omnis do not (often plastic). It's a little harder to push a mecanum robot partly due to this and partly due to four-wheeled resistance.