Multiple robots with ROS plugins (Sensor plugin vs. model plug-in)

asked 2013-10-30 15:43:00 -0600

Markus Bader
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updated 2013-10-30 15:44:21 -0600

I am using gazebo 2.0.0 and ROS hydro on Ubuntu 12.04 64bit
I like to have multiple robots within gazebo but with xacro/urdf file.
The idea was to use the name under which the robot model was spawned as prefix. This worked with some code rewriting by telling the gazebo_ros model (diffdrive) plug-in by using the physics::ModelPtr::GetName() function to access the model instance name. But the laser model uses receives a sensors::SensorPtr on Load?

How can I get the model instance name?
Is there a other way to do this?

Greetings Markus

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answered 2013-10-31 11:57:33 -0600

jbohren
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The idea was to use the name under which the robot model was spawned as prefix.

Just about every gazebo_ros plugin supports the <robotNamespace> configuration tag. You can use this to have them create their publishers and subscribers on namespaced topics.

See here for an example: https://github.com/ros-simulation/gazeborosdemos/blob/master/rrbot_description/urdf/rrbot.gazebo#L7

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Thanks Jonathan. But that’s not the solution I am looking for. Because I do not like to touch my xacro or sdf file after I fixed it. I just want to spawn the robot with a different model name. Using the <robotNamespace> looks to me like a design flaw or workaround.

Markus Bader ( 2013-11-04 08:29:50 -0600 )edit

Yeah, I see what you mean. It would be interesting to standardize plugin namespacing configuration so that you could tell a sensor plugin to be scoped to the model's spawn name. I also agree that the <robotNamespace> tag is sort of sloppy, but I personally tend to propagate these things with xacro arguments anyway.

jbohren ( 2013-11-04 21:22:10 -0600 )edit

Yes I know that xacro is able to forward variable and therefore also the robotNamespace but people are starting to build workarounds as long as there is no standard with a documentation. Honestly thing there must be a solution for SDF otherwise it won't be used.

Markus Bader ( 2013-11-05 04:34:59 -0600 )edit

While this is still a hackish solution, you don't normally need to touch the xacro/urdf file. robotNamespace is automatically added to URDF models before sending them to Gazebo: https://github.com/ros-simulation/gazebo_ros_pkgs/blob/hydro-devel/gazebo_ros/src/gazebo_ros_api_plugin.cpp#L2119

piyushk ( 2014-03-25 12:31:42 -0600 )edit

piyushk you are right, but the current (March 2014) gazeboros plugins especially the sensor plugins are not taking care of the robotNamespace. Thats way a created a pull request to get that problem fixed. https://github.com/ros-simulation/gazeboros_pkgs/pull/141

Markus Bader ( 2014-03-28 05:06:28 -0600 )edit

@Markus Bader: I understand now. Great work on the PR. I've definitely used laser and camera with namespaces and multi-robot scenarios. The laser one with current debs is still working for me. Could you specify which sensor plugin is broken, and I'll try and reproduce the issue.

piyushk ( 2014-03-28 18:04:40 -0600 )edit

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answered 2013-11-01 18:00:46 -0600

nkoenig
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The full (aka scoped) name of a sensor is: world_name::model_name::link_name::sensor_name

That string is returned by Sensor::GetScopedName().

So, you could parse the sensor's scoped name for the model_name.

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With GetScopedName() I am getting default::pioneer2dx::base_link::laser. The question is now can I assume that the model name is always the one after default?

Markus Bader ( 2013-11-04 08:25:53 -0600 )edit

The model name always follows the world name. It is the nature of the model hierarchy.

nkoenig ( 2013-11-07 15:48:16 -0600 )edit

Thanks, but now the question rises how important is it to get the model name? Should I implement in the Sensor class or in my plugin?

Markus Bader ( 2013-11-08 06:06:30 -0600 )edit

Are you using the model name to prefix ROS topics? If so, you can get the model name inside the plugin.

nkoenig ( 2013-11-13 16:28:44 -0600 )edit

Hi Nate! Worked it now out how you suggested. I made a merge request forked gazeborospkgs where I appied this changes on the gazeboroslaser sensor. I am now able to spawn on a very simple way to robots with the same xacro as shown in merge request.

Markus Bader ( 2014-03-20 10:45:44 -0600 )edit

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Multiple robots with ROS plugins (Sensor plugin vs. model plug-in)

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