Global_planner package with A* planner question.

asked 2013-11-06 09:52:45 -0600

Raptor
377 ●12 ●20 ●29

updated 2014-01-28 17:18:28 -0600

ngrennan
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According to this post the global_planner package is a refactoring of the NavFn package.

The global_planner package also has an A* planner implemented and seems to be much cleaner than the NavFn package.

What is the status of the global_planner package?
Is it going to eventually replace the navfn package as the default global_planner?
Is the global_planner package a drop in replacement for the navfn package?
- If not, how should the global_planner package be setup?

I noticed that the global_planner package does not get pulled down with the navigation stack and needs to be pulled separately with "sudo apt-get install ros-hydro-global-planner". For using with move_base the package does not have the pluginlib xml file that goes with it and it does not export the library as a nav_core plugin in its package.xml. Is there a reason for this? Is this something that is going to be added?

Thank you.

answered 2013-11-06 10:40:45 -0600

David Lu

10932 ●123 ●219 ●250 http://MetroRobots.com/

Status of Global_planner - I'm not sure if the latest version is in the debs yet, but the global_planner is stable and supported.

Replacement - I intended it as a replacement, but did not delete navfn for backwards compatibility. It should be a drop-in replacement.

The exclusion of the pluginlib xml is an oversight and shall be updated soon. I will also try to make a wiki page.

Important Note - Although you think it would, A* does NOT provide the same path as using Dijikstra's, which I discovered only recently. The potential field calculations that Navfn performs require a wide swath of values in the grid, and thus A* does not provide enough values to get a similarly smooth path. I'll try to include an illustration of this on the wiki.

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Thank you for the update. Do you know when the latest might be apart of the debs build? Would you be able to update this page when a wiki page is created? I am going to see if I can get it working probably sometime next week. I will let you know if I have any questions.

Raptor ( 2013-11-06 11:14:00 -0600 )edit

Hey Raptor. I finally updated the wiki page. Enjoy: http://wiki.ros.org/global_planner

David Lu ( 2013-12-16 05:06:45 -0600 )edit

(Although not all versions have the fixes yet...notably the old_navfn_behavior is the default and the parameter is not implemented)

David Lu ( 2013-12-16 05:08:10 -0600 )edit

Awesome! I will check it out. Thank you.

Raptor ( 2013-12-17 08:28:14 -0600 )edit

@David Lu I am trying to use the global_planner, I added it in move_base parameters as base_global_planner: global_planner/PlannerCore but it keeps saying this planner is not registered. I've used it from debs and git repo. Is there an example of a launch file with yamls? Thanks!

martimorta ( 2014-01-21 04:25:45 -0600 )edit

Marti - Can you please post this as its own question?

David Lu ( 2014-01-21 08:26:50 -0600 )edit

Yes, sorry :)

martimorta ( 2014-01-21 21:32:16 -0600 )edit

@David Lu I've found out why A* gives a different path from Dijkstra. The issue is that you use the Manhattan distance has heuristic, if you use the Euclidean distance the paths will be almost identical.

mateus03 ( 2014-10-08 08:25:04 -0600 )edit

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