Hi all,

I would like to fuse data from different sensors in ROS. Exact timing is
critical and unfortunately not all of the sensors can be synchronized
through hardware trigger lines. A simple example consists of registering
laser range-finder scans in a 3D map based on the range-finder
orientation as estimated from IMU measurements.

To synchronize both data sources in software the best technique I'm
aware of is to calibrate and track the measurement frequency of each
source, recover timestamps based on sequence numbers to keep jitter to a
minimum, and fuse based on these "rectified" timestamps.  Is there any
generic component in ROS that does this?

Secondly, in my experience the above strategy only gives satisfying
results if all the driver nodes involved run under a realtime scheduling
priority with recent Linux kernels (preferrably with the -rt patchset
applied). This requires acquiring relevant capabilities, setting the
respective scheduling parameters and monitoring realtime processes with
a watchdog/canary approach. Is there any infrastructure in ROS to handle
that?

Cheers,

Rene

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Dipl.-Inf. René Wagner                     Junior Researcher
DFKI Bremen                           Enrique-Schmidt-Str. 5
Safe and Secure Cognitive Systems             D-28359 Bremen

Phone: (+49) 421-218-64224       Fax: (+49) 421-218-98-64224
Web: http://www.informatik.uni-bremen.de/agebv/en/ReneWagner
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