Hi Ugo,

I just tried running your xml file through an xml validator (www.xmlvalidation.com).  I'm getting an error:

55: 8 The string "--" is not permitted within comments.

Maybe this is causing robot state publisher to fail quietly.

Vijay

On Wed, Apr 7, 2010 at 3:08 AM, Ugo Cupcic <ugo@shadowrobot.com> wrote:
Wim,

The urdf model which doesn't work contained two links and a joint. I tried it once more and I don't get a warning in the rxconsole. Still the robot_state_publisher didn't subscribe to the /joint_states topic.

The dummy.xml file I attached is my simplified urdf model that doesn't work. I have a more complete urdf model which works fine.

Cheers,

Ugo


Wim Meeussen wrote:
Ugo,

I figured it out. My urdf model didn't have the same number of joints as
my published joint_states messages.

I don't think this was your problem. The robot state publisher does
not care about additional/missing joints in the joint_states message.


rostopic info /joint_states
Type: sensor_msgs/JointState
Publishers:
 * /shadowhand_publisher (http://ulster:35258/)
Subscribers: None

The output above shows the problem: no node is subscribed to the
joint_states topic. So the robot state publisher is not receiving any
messages. This should only happen when you give the robot state
publisher a urdf with no or only one link. In that case, the robot
state publisher couldn't possible publish anything, and it therefore
does not subscribe to the joint_states topic.

But, you should have seen a warning in 'rxconsole'. It should have
shown either "Robot state publisher got an empty tree and cannot
publish any state to tf" or "Robot state publisher got a tree with
only one segment and cannot publish any state to tf". After it shows
this warning, the robot state publisher just sits there, unable to do
anything. I guess that is quite a confusing state. We had a discussion
about this here <https://code.ros.org/trac/ros-pkg/ticket/3224>.  Feel
free to add comments based on your experience with the robot state
publisher.

Wim










--
Wim Meeussen
Willow Garage Inc.
<http://www.willowgarage.com)
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--
Ugo Cupcic         |  Shadow Robot Company | ugo@shadowrobot.com
Software Engineer      251 Liverpool Road
need a Hand?           London  N1 1LX       | +44 20 7700 2487
http://www.shadowrobot.com/hand/              @shadowrobot


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