[ros-users] robot_state_publisher question

[Tully Foote]

Ben and David,
robot_state_publisher does not have persistence currently because if you
have persistence you must have policies about how long to persist things
before erroring etc.  These persistence models are very robot and
application specific.

If you need persistence for a specific application it actually makes sense
to keep that knowledge outside of the robot state publisher in something
like David's aggregator.

in general republishing old data is not very good thing to do.  That
information has already been sent out and has been recorded in tf buffers
around the system.

One thing which I think might help your use cases is to allow publishing of
partial trees not starting at the root.  Such that if you provide data about
M of N  links it will publish data about the M links even if they are
disjoint and skip the remaining links.

Would this handle your use cases?
Tully

On Fri, Oct 1, 2010 at 6:35 AM, David Lu!! <davidvlu at gmail.com> wrote:

> This is a problem I've run into as well. The way I usually fix it is
> to write a node that aggregates the joint state messages and send out
> a new stream with all the joints. But I agree, robot_state_publisher's
> lack of memory is a problem sometimes.
> -DL!!
>
> On Fri, Oct 1, 2010 at 8:07 AM, Axelrod, Benjamin <baxelrod at irobot.com>
> wrote:
> > I am using the robot_state_publisher to convert my joint angles to tf
> > transforms.  However, it seems that the robot_state_publisher doesn’t
> like
> > it when you send it different joints at different times.  In other words,
> > robot_state_publisher doesn’t maintain any state…
> >
> >
> >
> > For example, my urdf has 2 joints:
> >
> > Base -> joint1 -> link1 -> joint2 -> link2
> >
> >
> >
> > If I send it joint1, then at a later time I send it joint 2, I get this
> > error:
> >
> >
> >
> > Node: /robot_state_publisher
> >
> > Time: 1285876513.251897000
> >
> > Severity: Error
> >
> > Location:
> >
> /home/arm_user/darpa_arm_software/stacks/robot_model/robot_state_publisher/src/robot_state_publisher.cpp:RobotStatePublisher::publishTransforms:78
> >
> > Published Topics: /rosout, /tf
> >
> > Could not compute link poses. The tree or the state is invalid.
> >
> >
> >
> > But if I send both joints at once, then everything is fine.  This seems
> like
> > a major limitation to me.  Am I missing something?
> >
> >
> >
> > I am using boxturtle.  And am using robot_state_publisher running as a
> node.
> >
> >
> >
> > Thanks,
> >
> > -Ben
> >
> >
> >
> > Ben Axelrod
> >
> > Research Scientist
> >
> > iRobot Corporation
> >
> > 8 Crosby Drive, Mail Stop 8-1
> >
> > Bedford, MA 01730
> >
> > (781) 430-3315 (Tel)
> >
> > (781) 960-2628 (Fax)
> >
> > baxelrod at irobot.com
> >
> >
> >
> > _______________________________________________
> > ros-users mailing list
> > ros-users at code.ros.org
> > https://code.ros.org/mailman/listinfo/ros-users
> >
> >
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-- 
Tully Foote
Systems Engineer
Willow Garage, Inc.
tfoote at willowgarage.com
(650) 475-2827
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