27-09-2011 20:21

Hector

Re: paper: Mecanum Wheel Summary

Hi all,
Please note THIS IS A WORK IN PROGRESS
This document is a draft version of an idea, the outcome is close but not totally accurate to what we are looking for which is a bump free design.

Within the following days, I will post a more detailed and accurate document.

The mecanum wheel resulting from this process is CLOSE to the desired wheel but NOT accurate enough yet.

Take that into consideration when using this method.

Hector

27-09-2011 20:32

Ether

Re: paper: Mecanum Wheel Summary

Hector and I have been discussing this offline.

Cutting a cylinder with a plane at 45 degrees creates an ellipse which gives an approximately correct roller profile which should suffice for most applications.

But if you are a perfectionist, there's a mecanum roller design calculator available here which generates a theoretically correct XY data file so that the rollers create a perfectly circular wheel circumference. Hector has been kind enough to test this by running the calculator and CAD'ing up a model to verify the algorithms used in the calculator.

The user enters the desired radius of the effective wheel circumference, the desired roller radius at the center of the roller, and the desired number of rollers per wheel. The program then calculates the roller clearance, the rotor length for no gaps at the circumference, the roller end-radius at this no-gap length, and an XY data file for the roller profile. It is easy to iterate the radius to find the largest radius that still leaves an acceptable clearance between the rollers.

I believe Hector is working on a CAD-only process to achieve the same result.

27-09-2011 22:24

Hector

Re: paper: Mecanum Wheel Summary

Right Ether,
The goal is to find a CAD-only design procedure as accurate as the mathematical approach you presented.

Right now the problem is to create a parabolic contour using basic CAD tools only.

I was thinking on slicing a cone instead of a cylinder to get the right profile for the roller.

But at this point, Ether Calculator is really accurate and the roller CAD from the raw data on the XY.txt file generated follows the circular shape perfectly. I tested the calculator data on SolidWorks 2008. So far so good.

Hector.