Quote:
Originally Posted by Nate Laverdure
Less wheels are better than more
Each wheel needs to be individually powered and controlled. You can't couple any of the wheels together and still retain holonomic motion. If you're going to spend resources (time, money, anguish) on an 8-motor omnidirectional drivetrain, why not make a fully independent swerve instead?
For number of wheels N > 3, you must design your chassis to be flexible enough to load the wheels approximately evenly. For N = 3, the chassis can be as rigid as you wish.
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I agree that more wheels (and motors) is unnecessary complication.
We competed with what I believe is a unique Kilough variant last year. We used four wheels with 30deg toe-in (thin diamond) instead of 45deg. This gave us better traction (closer to tank) in the fwd/rev direction and worse in left/right. The expected fwd traction improvement vs. Mechanum is cos(30)/cos(45) or 22% (and -30% sideways). We used two undriven Vex 2.75" omniwheels with encoders to measure actual movement instead of driven wheel speed. The system performed very well. We did use a stiff frame, but the closed loop control detected and corrected for any wheel slip.
This year, there is no apparent preferred direction of travel so we are designing a more traditional Mechanum system. Given the potentially slippery platforms and wheels loosing contact on the ramps, we will again use instrumented following wheels to correct for wheel slip.