[ros-users] Generic interface for Ackermann Steering based robots

Piyush piyushk at gmail.com
Sun Jan 29 00:05:53 UTC 2012

Thanks for everyone's feedback on this. I was not aware that a version
of the local planner for ackermann navigation existed. Austin, if you
think your solution is reusable, would you mind adding your solution
as one of the answers here:
(I suspect this would directly follow up on Chad's answer)

The initial port of our navigation code will be completely independent
of the navigation stack. However if we can decide on a common
interface, then with a bit of effort we may be able to choose between
different navigation solutions. Stefan, I for one would definitely be
interested if you moved your solution to open source. We probably
won't be working with a terrain as difficult as RoboCup Rescue, but it
might be useful nonetheless to take a look at it.

Jack, what is the best place on the wiki to setup a group for this?


On Sat, Jan 28, 2012 at 11:18 AM, Jack O'Quin <jack.oquin at gmail.com> wrote:
> On Sat, Jan 28, 2012 at 10:52 AM, Stefan Kohlbrecher
> <stefan.kohlbrecher at googlemail.com> wrote:
>> Hi,
>> we use a Ackermann-driven based UGV for search and rescue scenarios.
>> It is based on a Kyosho Twinforce RC chassis (image for example here:
>> http://www.gkmm.tu-darmstadt.de/rescue/?q=node/8 ). We also use the
>> sbpl_lattice_planner for generating motion plans, but found the
>> navigation stack to be suboptimal for our application, as the vehicle
>> dynamics plus harsh terrain of the NIST standard arenas used for
>> RoboCup Rescue violates some of the assumptions made in the navigation
>> stack. For a 100kg+ platform moving on flat ground, the assumption
>> that odometry provides a stable short term reference frame for example
>> is very reasonable. For a <10kg vehicle going over pitch/roll ramps
>> OTOH there basically is no trustable odometry (see for example 1:05 in
>> this video: http://www.youtube.com/watch?v=nI1DWboC73w ,shows only
>> reactive driving as our planner back then did not work correctly)
>> So our current approach is to use SBPL based plans and not use a local
>> planner as provided by the navigation stack. The whole plan (generated
>> from SBPL or another planner) is sent to the vehicle controller, which
>> then closely follows it. The low level control system of the UGV
>> incorporates  a EKF-based INS that fuses data from inertial/magnetic
>> (IMU) sensors, SLAM pose estimates and wheel encoders and thus can
>> follow the plan nicely. I'll try to make a video of it in simulation
>> in the next few days. The code is not available in our open source
>> repository, but that might change if interest is there.
> I think there is definitely enough interest to justify creating an
> Ackermann steering interest group. There are many aspects to it,
> including navigation, interfaces and simulation.
> As a start, I suggest creating a wiki page to share links to code and
> techniques. Perhaps it could evolve into a project team to develop and
> maintain ROS packages for dealing with that type of vehicle.
> --
>  joq
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