JointStates with only velocity #243
Description
Hello!
Apologies if this has been previously answered but I couldn't find any mention of it.
Currently robot_state_publisher will only use a JointState message if the position field is populated.
For a lot of the machines my team works on, we only get joint velocity. For example we only get wheel speeds rather than wheel position. This may be more common with continuous joints, but maybe it is relevant to others.
As previously discussed in #64, JointState messages are valid without position data. I was wondering if this project would consider a pull request which adds the ability to use a JointState message that only contains velocity data as a valid input and integrate this velocity over the time difference to the next received message to provide a valid transform.
I understand this would have integration error and may not be the most accurate, but I do think it would be quite useful for vehicle visualisation and would be an improvement over ignoring a velocity only message entirely.