pass ros param as argument to another param

asked 2020-10-11 11:56:31 -0500

wintermute
180 ●38 ●52 ●54

Hello,

On my launch file I have a:

<rosparam command="load" file="$(find myrobot)/config/robot.yaml" />

statement which loads the parameters from my yaml file. again I have a node like:

<node name="controller" pkg="pid" type="controller" ns="left_wheel" output="screen" >
   <param name="Kp" value="4.8" />
    <param name="Ki" value="3.2" />
    <param name="Kd" value="0.02" />
</node>

how can i make the second statement, take arguments from the yaml file. in the yaml file I have my parameters as /myrobot/params/kP ... etc, and I need to pass those parameters as an argument to the node config.

Any ideas greatly appreciated,

~Best

answered 2020-10-12 05:19:13 -0500

Weasfas
1695 ●12 ●91 ●41

His @wintermute,

For this to work you will need to use the ROS parameter server.

For the node to be able to access those parameters you can do several things:

1) Either you process the parameters as public parameters; this is done by using the <rosparam command="load" file="$(find myrobot)/config/robot.yaml" /> command and then retrieving those param in the node as public params with functions like nh.getParam("param_name", param).

2) Or process those parameters as private ones by passing directly the config file to the node.

<node name="controller" pkg="pid" type="controller" ns="left_wheel" output="screen" >
 <rosparam command="load" file="$(find myrobot)/config/robot.yaml" />
</node>

and reading them like explained before.

Hope this helps you.

Regards.

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Hi @Weasfas,

is it possible to remap parameters? If it was possible to remap from /mybot/kP to /left_wheel/controller/kP I would be set.

Best

wintermute ( 2020-10-12 09:03:04 -0500 )edit

@wintermute There is no posibility to remap a parameter. If you want to change from one parameter name to another you will need to delete it from the param server using rosparam delete and then load/ set again your updated parameter with rosparam load/rosparam set. Load is for files and set is for individual parameters and those are command line tools. Besides you can also use these directives programatically in roscpp with nh.setParam("param_name", param); and nh.deleteParam("param_name");.

Weasfas ( 2020-10-12 11:45:21 -0500 )edit

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