omniwheel design in urdf

Question

Do you know any ros-package including an omni-wheel urdf? Or does anyone happen to design an omniwheel in urdf? I just don't want to re-invent the wheel :)

By the way, what I mean by omni-wheel is the one having a main wheel and several roller wheels -mostly perpendicularly aligned-. Like the ones on the robotino platform. I don't prefer using two motors for each wheel that can imitate an omniwheel (=omni-drive) or changing the friction properties of the surfaces in gazebo. These are some of the tricks that I'm aware of.

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Originally posted by Tully on ROS Answers with karma: 1145 on 2011-02-14

Post score: 4

Answer 1

As far as I know, no one has done something like this yet. However, I looked up the design of the robotino and it should be pretty easy to do! Certainly much easier than other mecanum wheels....

You'll first want to start learning the basics of URDF. I suggest that you read through David Lu!'s excellent tutorials on Learning URDF Step by Step.

Your robot has 6 rollers on each wheel, distributed 2Pi/3 away from eachother with an offset of 2Pi/6 it looks like per side. We're lucky that they are orthogonal. The only tricks I would encourage you to use would be to remember to set each roller as a continuous joint and to use the XACRO shortcuts for each roller to make changing the physics and inertias simpler if you have to. You may also want to only connect the rollers to one side. You will probably end up with something simple like three "L" shapes per side connected in the center around a hub.

Good luck! This will be a good learning experience for URDF and XACRO. I had to make an offset caster for my robot. :)

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Originally posted by Chad Rockey with karma: 4541 on 2011-02-20

This answer was ACCEPTED on the original site

Post score: 4

Answer 2

Hi,

@Tully: Thank you for posting this question from ros.users list to here.

@Chad: Thank you for letting me know that my question is posted here and answered :) I have done what you have mentioned in VRML for the simulator Webots for some reason. But, I am planning to do similar thing for Gazebo as well in a month or so, by heavily using XACROs for URDF.

When I asked this question, my concern was how to deal with the bounding boxes of the main wheel and the rollers since they are both cylinders and one within the other. Then, I thought that why bother yourself putting a bounding box for the main wheel! It doesn't collide with anywhere in my application.

The simulated robot has a little drift but it is not gonna cause that much trouble in the closed loop control.

Cheers

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Originally posted by Kadir Firat Uyanik with karma: 288 on 2011-02-20

This answer was NOT ACCEPTED on the original site

Post score: 3