Quote:
Originally Posted by Ether
Yes.
Look at Figure1 on Page2 of this document.
You will see that the ratio of forward motive force to traction force is the same for both omni and mec:
mec: (tau/r)/(tau*sqrt(2)/r) = 1/sqrt(2)
omni: (tau/(r*sqrt(2)))/(tau/r) = 1/sqrt(2)
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Okay, so then if I increase the gear ratio by sqrt(2)/2 to increase the available torque for the Omni-wheel drive, it should match the pushing force
and traction of the mecanum (minus larger friction loss of rollers for Omni). That leaves the major advantage of mecanum as the mechanical mounting being square. Omni has the advantage of lower weight, cost and complexity.
Do we assume that AndyMark included the sqrt(2)/2 in the CoF specification or is there a difference in materials? IFI reports CoF of 1.1 for Omni-wheels and 1.0 for mecanum - still an difference, but not the magic ratio.
That said, I have one extra design variable available with Omni-wheels because I am not locked into 45deg mounting by the wheel manufactures. If I build an asymmetric Killough with wheels at 30deg, I get 22% more forward torque
and traction (0.866 vs. 0.707) than can be achieved with mecanum. Am I missing something here? Of course this comes at a price, I get 0.5 vs. 0.707 = 30% less side torque and traction. More forward traction is highly desirable for better forward acceleration. Having even poor staffing capability has benefits over KOP 6-wheel tank drive, if the other tradeoffs can be managed.