URDF conversion problem for intermediate fixed joints

asked 2014-05-14 09:18:23 -0600

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Hi guys,

I'm improving and adding new features in the URDf/Xacro file of HyQ robot but I found a bug, at least I think that this a bug, when we define intermediate fixed joints, i.e. something like this:

<joint name="my_base_joint" param="fixed"> <parent link="base_footprint"/> <child link="trunk_link"/> </joint>

<joint name="ptu_joint" param="fixed"> <parent link="trunk_link"/> <child link="ptu_base_link"/> </joint>

<joint name="ptu_pan_joint" param="revolute"> <parent link="ptu_base_link"/> <child link="ptu_pan_link"/> </joint>

<joint name="ptu_tilt_joint" param="revolute"> <parent link="ptu_pan_link"/> <child link="ptu_tilt_link"/> </joint>

When I spawn my model I can see that apparentely everything is OK in Gazebo, but when run RVIZ I have problems for computing some transformation (TF). In addition, I realised that Gazebo defined two fixed frame, i.e. basefootprint and ptujoint. Thus, tf cannot find the transformation between for example ptutiltlink and base_footprint. According to my understanding is due Gazebo defined two fixed frames, but I'm not completely sure about this.

If we guess that this is the problem so we can suspect that the root of the problem could be the conversion between URDF and SDF.

For your information I'm using Gazebo 1.9.5 in ROS Hydro. I hope that this can help to improve the Gazebo project. Let me know if someone has an idea about the problem.

Thanks in advance, Carlos

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