I wonder if it is possible to construct a for loop to build N wheels sub-assemblies for a mobile robot in a xacro.urdf file.
I have already created an URDF using Xacro for the mobile robot and the wheel sub-assembly but I need to generate N wheels on each side of the mobile robot.
Any ideas, turnarounds or out-of-the-box solutions?
Thanks,
An alternative to xacro with urdf is to use SDF with embedded ruby (see the rigid_cart model for an example).
Use the following command to generate the sdf file from the rsdf template:
erb model.rsdf > model.sdf
If you have an if statement and you can call a macro within itself, you can build recursion with a counter which breaks the recursion as it reaches zero.
<xacro:macro name="loop" params="links_qty">
<!-- call some macros or do other things -->
<xacro:if value="${links_qty}">
<xacro:loop links_qty="${links_qty-1}" />
</xacro:if>
</xacro:macro>
<xacro:loop links_qty="15" />
I just tested if this works and it does.
To my knowledge, "if" statements are the only logic expressions currently implemented in xacro. I think having a wheel macro and using a single line for each wheel is the best you can do using just xacro, which isn't too bad.
Can you explain the reason you need this capability? If I really had to have something like this, I would probably attempt to use python to generate the single line macro calls and insert them into the xacro file.
Asked: 2014-08-20 05:00:02 -0500
Seen: 3,803 times
Last updated: Feb 04 '17
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