Macro for nodes in launch file

asked 2017-01-18 09:26:49 -0500

Stian
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I'm trying to use the PID package to control the joints of a snake robot. Since each node will be single controller, I need to start several nodes to control all the joints. The pid nodes have several parameters, so I hope to be able to write some form of macro that can make my launch file more compact and manageable. I found out that launch files are written in XML and not Xacro, so I can't use macros like you can for the URDF files. Does anyone know a clever way to do this?

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launch files are written in XML and not Xacro, so I can't use macros like you can for the URDF files

This is incorrect. xacro should be able to generate any xml format, and xacro is also in xml format.

130s ( 2021-01-07 01:36:30 -0500 )edit

Specifically for include-ing a .launch file so this isn't exactly for node, but #q229489 is a good option that doesn't require customization (i.e. needed functionality is in the library).

130s ( 2021-01-07 01:42:35 -0500 )edit

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answered 2017-01-19 22:28:06 -0500

Thomas D

4347 ●33 ●65 ●86 http://denewiler.us/cv

I don't know of a way to have macros or for loops in launch files.

One option is to have a separate yaml file for each controller that contains the parameter values for a single controller. In your launch file you would have to list out each <node> separately but you could have something like this that uses the rosparam tag:

<node pkg="pid" type="controller" name="pid1">
  <rosparam command="load" file="$(arg your_package)/config/pid1.yaml"/>
</node>

Repeat that block N times and have N yaml files. The pid1.yaml file would look like (follow the link above for more examples):

Kp: 1.0
Ki: 0.1
Kd: 0.2
upper_limit: 5.0
lower_limit: 0.2
windup_limit: 10.0

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Macro for nodes in launch file

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