[ros-users] Planning and joint state map cache

Lorenzo Riano lorenzo.riano at gmail.com
Fri Mar 4 21:04:08 UTC 2011

've been playing with arm motion planning (OMPL) on a non-PR2 robot for a
while now. I am currently working with a Schunk arm and a ShadowRobot hand
at the tip. Both devices are controlled on different computers, and a custom
made node fuses the joint information from both so that a single
robot_description (and robot state) is obtainable. The problem I am having
is that OMPL generates a collision-free plan, possibly even the Trajectory
Filter, but during the execution move_arm stops crying for collisions that
don't exist. The symptoms are:

   - Right after a goal is requested, all of the nodes that use the
   motion_planning_common stack complain that "Empty joint state map cache" and
   "Got joint state update but did not update some joints for more than 1
   second. Turn on DEBUG for more info"
   - If I send a MoveArmAction request where disable_collision_monitoring is
   true, somebody (OMPL? TrajectoryFilter?) decides that there are not
   obstacles and plans a perfect straight line trajectory.

In the past I have successfully generated plans with a hand-less 7dof arm,
now I don't understand what I am doing wrong! In particular, the warning
messages I receive are really puzzling...

Lorenzo Riano, PhD
Research Associate
Intelligent Systems Research Centre
University of Ulster
Magee campus
BT48 7JL

phone: +44 (0)28 71375187
email: l.riano at ulster.ac.uk, lorenzo.riano at gmail.com
skype: lorenzo.riano

Webpage: http://isrc.ulster.ac.uk/Staff/LRiano/Contact.html
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