On Mon, Aug 16, 2010 at 1:19 PM, <jrousseau@aptima.com> wrote:

I'm trying to spawn several robots of the same type in gazebo through ros and am
hitting what seems to be a controller namespacing issue. What I would like is
for each robot to live in its own namespace like:

robot1/odom
robot1/cmd_vel
...
robot2/odom
robot2/cmd_vel
...

The urdf's I'm currently using (erratic_description/urdf/erratic_base.xacro from
ua-ros-pkg) take in a namespace directly inside the URDF file (example below):

<controller:diffdrive_plugin name="differential_drive_controller"
plugin="libdiffdrive_plugin.so">
<alwaysOn>true</alwaysOn>
<update>100</update>
<updateRate>100.0</updateRate>
<leftJoint>base_link_right_wheel_joint</leftJoint>
<rightJoint>base_link_left_wheel_joint</rightJoint>
<wheelSeparation>${caster_wheel_offset_y*2}</wheelSeparation>
<wheelDiameter>${wheel_radius*2}</wheelDiameter>
<torque>5</torque>
<interface:position name="position_iface_0"/>
<robotNamespace>robot1</robotNamespace>
<topicName>cmd_vel</topicName>
</controller:diffdrive_plugin>

So basically the problem is this: Since the controller converts gazebo objects
into ros topics and the controller is inside the definition of a robot, how do I
uniquely specify namespaces for multiple robots based on the same URDF?

I could just make several copies of the erratic_base.xacro and just change the
<robotNamespace> tag in each, but that seems kludgy. Is there some way to pass
in variables to a URDF from launch file or something?

if you look at the robot spawn script in gazebo,

rosrun gazebo spawn_model

there's an option to specify -namespace, it simply adds the <robotNamespace> tag to all the <controller>'s. This might be what you need, but double check and make sure the individual controller plugins parses and uses the robotNamespace tag.

PS is this even the general method for working with multiple robots with ros +
gazebo (ie spawning several robots under different namespaces?) or am I heading
in the wrong direction...

There's been some discussions on multi-robot + ros. Basically, multiple robots separately namespaced under one ros core should work in gazebo, but in reality network load for more than 3 robots might become a significant burden. See more discussions here:

https://code.ros.org/gf/project/ros/mailman/?action=ListThreads&mailman_id=20&_forum_action=ForumMessageBrowse&thread_id=27895

John

Jeff

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