On Sat, Jan 28, 2012 at 10:52 AM, Stefan Kohlbrecher
<stefan.kohlbrecher@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