[ros-users] Issues with rviz

Wim Meeussen meeussen at willowgarage.com
Thu May 20 17:06:41 UTC 2010


Jan,

When rviz receives laser scan messages, it only keeps the 10 most
recent messages in a buffer. So, if you send laserscans at 50 Hz (it
looks like that's the rate you use), that means rviz only stores 0.2
seconds worth of laser scans. So when your laser scans are more than
0.2 seconds ahead of your tf transforms, rviz would be unable to
transform any laser scans. To find out if this is the problem you hare
seeing, you should modify the timestamps of your laser scan messages,
by deducting something like 1 second from each timestamp before
sending out the message from the laser scanner driver. Or you could
create a node that takes in laser scanner messages, modifies the
timestamp, and send out the modified laser scans.

Wim


On Thu, May 20, 2010 at 9:33 AM, Jan Elseberg
<j.elseberg at jacobs-university.de> wrote:
> Hi,
>
> the issue occurs when using rviz on a seperate computer (synchronized to the
> robot with ntp) as well as when used only on the robot. The tf-tree of rviz
> is attached, it is the same as before.
>
> Jan
>
> Tully Foote wrote:
>>
>> Jan, Are you running rviz on a seperate machine?  If so make sure that the
>> clocks are synced using ntp or similar between the multiple machines.
>> To see the tf tree that rviz is using try running "view_frames
>> --node=rviz_******" where ******* is the UUID of the anonymous rviz process
>> which you can get from rosnode list.
>> Tully
>>
>> On Thu, May 20, 2010 at 9:19 AM, Jan Elseberg
>> <j.elseberg at jacobs-university.de <mailto:j.elseberg at jacobs-university.de>>
>> wrote:
>>
>>    Wim,
>>
>>    the timestamps of the laser scans are concurrent to the ones I'm
>>    getting
>>    with "rostopic echo /tf".
>>    I was under the impression that tf would give me an error of some kind
>>    in this scenario ?
>>    Also, if the issue lies with my tf-tree, shouldn't there be similar
>>    problems in my node
>>    that transforms the laser scans into the /map frame using the
>>    tf::TransformListener ?
>>
>>    Regards,
>>
>>    Jan
>>
>>
>>
>>    Wim Meeussen wrote:
>>    > Jan,
>>    >
>>    > Your tf tree looks fine, but it is possible that the timestamps of
>>    > your laser scans are wrong. Your tf buffer keeps a 10-seconds window
>>    > of transformations. When the timestamp of your laser scan does
>>    not fit
>>    > in that 10 seconds window, tf won't be able to transform it.
>>    From the
>>    > data you sent, it looks like your tf buffer is nicely synchronized
>>    > with the current time in your system, so I would suspect that your
>>    > laser scans have timestamps that are either more than 10 seconds in
>>    > the past, or some number of seconds in the future.
>>    >
>>    > You can check the timestamp of your laser scans using "rostopic echo
>>    > laser_scan/header/stamp".
>>    >
>>    > Wim
>>    >
>>    >
>>    >
>>    >
>>    >> I've attached the results of view_frames. I have also tried the
>>    other stuff
>>    >> on the troubleshooting guide. Transformations between the laser
>>    frame and
>>    >> every other frame work fine. Across the longest tf-chain
>>    (/front_laser to
>>    >> /map) the average delay is approx 25ms and the maximal delay is
>>    approx.
>>    >> 55ms. From this it appears to me that the tf-tree is correctly
>>    set up, but
>>    >> maybe there is something else I can check?
>>    >>
>>    >> Regards,
>>    >>
>>    >> Jan Elseberg
>>    >> Eitan Marder-Eppstein wrote:
>>    >>
>>    >>> Jan,
>>    >>>
>>    >>> It sounds like something may be wrong with your transform
>>    tree. Can you
>>    >>> try running "rosrun tf view_frames"? This will generate a PDF
>>    of the current
>>    >>> transform tree structure. You may also want to check the
>>    troubleshooting
>>    >>> link on the sidebar of this page: http://www .ros.org/wiki/tf
>>    <http://ros.org/wiki/tf>
>>    >>> <http://ros.org/wiki/tf> for more information on useful tf
>>    debugging
>>    >>> strategies.
>>    >>>
>>    >>> Hope this helps,
>>    >>>
>>    >>> Eitan
>>    >>>
>>    >>>
>>    >>>> On May 20, 2010 3:38 AM, "Jan Elseberg"
>>    <j.elseberg at jacobs-university.de
>>    <mailto:j.elseberg at jacobs-university.de>
>>    >>>> <mailto:j.elseberg at jacobs-university.de
>>    <mailto:j.elseberg at jacobs-university.de>>> wrote:
>>    >>>>
>>    >>>> Hi everyone,
>>    >>>>
>>    >>>> I am trying to get our robot to work with the navigation
>>    stack of ros.
>>    >>>> I've been following the tutorial on
>>    >>>> http://www.ros.org/wiki/navigation/Tutorials/RobotSetup .
>>    After setting
>>    >>>> up the robot with a tf-tree and sensor nodes , I have noticed
>>    a problem
>>    >>>> with rviz. I am unable to display the laserscan messages in
>>    any frame
>>    >>>> other than the laser coordinate system itself, i.e., whenever
>>    I select a
>>    >>>> <Fixed_Frame> other than /front_laser the status of the laser
>>    scan
>>    >>>> display shows the error:
>>    >>>>
>>    >>>> "Unknown reason for transform failure".
>>    >>>>
>>    >>>> Also, this warning appears in the bash:
>>    >>>>
>>    >>>> [WARN] 1274341043.701801000: MessageFilter [target=/base_link
>>    ]: Dropped
>>    >>>> 99.03% of messages so far. Please turn the
>>    [ros.rviz.message_notifier]
>>    >>>> rosconsole logger to DEBUG for more information.
>>    >>>>
>>    >>>> Doing so gives me these repeating debug messages:
>>    >>>>
>>    >>>> MessageFilter [target=/base_link ]: Added message in frame
>>    /front_laser
>>    >>>> at time 1274341252.994, count now 10
>>    >>>> MessageFilter [target=/base_link ]: Removed oldest message
>>    because
>>    >>>> buffer is full, count now 10 (frame_id=/front_laser,
>>    >>>> stamp=1274341252.813649).
>>    >>>>
>>    >>>> This suggests a problem with the tf-tree to me. However, when
>>    using the
>>    >>>> "transformPoint(...)" function of tf::TransformListener in my
>>    own nodes
>>    >>>> to transform the laser scan into the global frame everything
>>    works as
>>    >>>> intended with no errors/warnings.
>>    >>>>
>>    >>>> Does someone have an idea what I am doing wrong?
>>    >>>>
>>    >>>> Thank you for any help!
>>    >>>>
>>    >>>>
>>    >>>> Jan Elseberg
>>    >>>>
>>    >>>> _______________________________________________
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>>
>>
>> --
>> Tully Foote
>> Systems Engineer
>> Willow Garage, Inc.
>> tfoote at willowgarage.com <mailto:tfoote at willowgarage.com>
>> (650) 475-2827
>
>
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-- 
--
Wim Meeussen
Willow Garage Inc.
<http://www.willowgarage.com)



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