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Should I choose to write a URDF manually or export URDF by Solidworks?

asked 2017-01-12 10:59:15 -0500

shawnysh gravatar image

I wonder what is the normal process of the development of a robot, this would be a broad question and not specific enough.

What I want to know urgently is dependent on what I choose to get URDF by hand OR by Solidworks export plugin.

I heard that using sw_urdf_exporter would introduce error of coordinate etc. and sometimes not work, and the code format is not good for maintenance if exported automatically without xacro. In addition, I notice that the URDF of pr2 robot is written manually, which easier to understand the code.

However, writing a bunch of URDF to develop a robot seems not normal intuitively.

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answered 2017-01-13 11:07:35 -0500

renarded gravatar image

updated 2017-01-13 11:09:03 -0500

I first tried to use SW to URDF and had many problems with meshes coordinates, and some other problems I don't remember now.

By the time I almost fixed everything I had a good understanding of how URDF was working, and I discovered xacro. Now I am only using xacro to produce my URDF.

Some points against using this SW to URDF :

  • everytime you update your file on Solidworks you need to export everything again. In my case I am running Ubuntu on my computer, and am not the one doing the mechanical design. It means I had to install SW on my Windows, and everytime I had to change something I had to restart my computer, go to Windows, run the plugin, etc, etc.

  • The development of the plugin is not supported anymore

  • One day you will need to debug something in your URDF. It will be harder if you don't know how it's made

  • With this plugin you can't use xacro, which is a great tool and will save you some time in the future

The SW to URDF plugin has both positive points and negative points. I think it can be very useful in some cases. But personally, from my experience, I would suggest to create a xacro file instead of using the plugin.

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I wonder how to make mesh file to coincident with the urdf you write manually. I think the key to urdf file is the relation of link and joint, which mainly includes origin tag and axis tag. So, the mesh for links should be exported by blender one by one through modifying coordinates, right?

shawnysh gravatar imageshawnysh ( 2017-01-14 07:41:52 -0500 )edit

@shawnysh Each joint origin depends on the parent link. The origin of a link (in visual) is the origin of the visual part depending on the specific link (it's kind of a local offset origin). You have to export each mesh with a local origin (zero)

renarded gravatar imagerenarded ( 2017-01-16 09:01:03 -0500 )edit

thanks, gotcha

shawnysh gravatar imageshawnysh ( 2017-01-17 23:16:35 -0500 )edit

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Asked: 2017-01-12 10:59:15 -0500

Seen: 1,135 times

Last updated: Jan 13 '17