[ros-users] Core robot controller manager

Stuart Glaser sglaser at willowgarage.com
Sun Nov 7 21:14:52 UTC 2010

Hi Daniel,

The RealtimePublisher will work fine on a non-realtime system.  It may
be slightly less efficient than normal ROS publishing, but I don't
think you'll notice any difference.


On Sun, Nov 7, 2010 at 6:03 AM, Daniel Stonier <d.stonier at gmail.com> wrote:
> Hi all,
> I've been working over the last few weeks to put together a core robot
> subsystem for one of our robots - it's pr2 like with a mobile base, a
> manipulator and various other motor driven mounts (14 motors in all),
> but on an a real budget and I was wondering what experiences others
> have had doing something similar.
> The primary challenges with ours are two fold:
> 1) It isn't running an ethercat based system. i.e. it's non-real time,
> though thats something I would like to upgrade on this particular
> robot in the future, however its not something that all of our robots
> will have. This means the motors are often driven on multiple loops,
> some fast and some slow (so not to burden the low spec embedded
> board). Also, the controllers in ros are using a real time publisher -
> and I made the assumption that is not usable for non real time (please
> correct me if I'm wrong!), so rebuilt all the
> controllers/transmissions we had to use.
> 2) We're running on a low spec intel atom (the lowest), so topic
> communication and loop frequencies need to be kept down. Since its not
> centralised, it needed some care designing to ensure callback
> frequencies didn't escalate and control loop periods weren't consuming
> too much horsepower. Most of it is interrupt driven now too because
> different subsystems are cycling at different speeds.
> Finally, its roughly working, but its quite ad-hoc and took alot of
> building in the long run and am wondering if there's an easier way to
> do it, or a way to genericise components so that they can be recycled
> for both non-realtime and realtime systems.
> Regards,
> Daniel Stonier
> --
> Phone : +82-10-5400-3296 (010-5400-3296)
> Home: http://snorriheim.dnsdojo.com/
> Yujin Robot: http://www.yujinrobot.com/
> Embedded Ros : http://www.ros.org/wiki/eros
> Embedded Control Libraries: http://snorriheim.dnsdojo.com/redmine/wiki/ecl
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Stuart Glaser
sglaser -at- willowgarage -dot- com

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