Hi Aswin,

I'm still coming up to speed with ROS so I'm not familiar with what's 
there but I did do a fair bit of research in this area (and am 
reasonably familiar with the Packbot) ... here's my 2c on this topic.

Depending on how hard your "highly undulating military environment" is, 
you might well have quite a challenge on your hands. Realtime, 
deployable path planning through "advanced mobility" terrain (terrain 
where you actually need to consider the 3D characteristics of the 
terrain in detail) is still largely an open research problem, especially 
with a small reconfigurable tracked vehicle such as the Packbot. The 
vast majority of such autonomous systems demonstrated in the real world 
"solve" the problem mostly by restricting the robot to terrain that its 
intrinsic mechanical design allows it to easily overcome, rather than 
via true 3D planning.

Unless you plan on turning this into a full blown research project in 
its own right, your best approach may be to keep to areas that you can 
easily detect as drivable in your pointcloud and then do 2D path 
planning over the resulting space. You won't max out the capabilities of 
the Packbot (and for a basic 2D planner that isn't able to move the 
flippers, a Packbot is often *less* mobile than a similarly sized 4WD 
robot such as a Pioneer AT or a Volksbot RT because the tracks can make 
it harder to turn and it can be more easily high-centred) but at least 
you'll have something working. Alternatively, if you can restrict your 
tasks to things like detecting and climbing stairs or kerbs or other 
detectable, structured objects and then 2D plan between them you might 
also be able to make some progress.

I'm not familiar with the modules available in ROS (that in itself is an 
active research topic) but it's possible there's something there you can 
start with but for a robot such as the Packbot, even detecting what is 
and isn't drivable in a meaningful fashion (ie. more than simply 
detecting flat ground but including steps and kerbs that the Packbot is 
able to drive over) in a natural environment is also rather non-trivial.

Best of luck! :-)

- Raymond

On 25/02/2011 4:31 PM, Aswin Thomas wrote:
>
> Hi all,
>
> Does anyone know of a reliable algorithm that can do path planning in 
> 3D? Assuming that a 3D point cloud is available in real time. Are 
> there any ROS packages are available?
>
> I have a packbot and am supposed to navigate it autonomously in a 
> highly undulating military environment. I have no idea how to go about 
> doing it.
>
> On another note, I am a new ROS user and have a hard time 
> understanding the navigation tutorials. Is there any ROS based project 
> I can take a look? A very very simplified one will do. Its just to 
> help me take off since I have a project deadline in a month.
>
>
> Thanks for your suggestions.
>
>
> Cheers
>
> Aswin
>
>
> _______________________________________________
> ros-users mailing list
> ros-users@code.ros.org
> https://code.ros.org/mailman/listinfo/ros-users


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