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Is there a way to follow a trajectory with no collision detection ?

asked 2011-08-16 21:39:36 -0500

Guido gravatar image

updated 2011-08-17 00:34:56 -0500

Hi all,

Is there a way, in ROS, to do a simple trajectory following with no costmap and no collision detection ? The trajectory is specified in terms of (x,y) waypoints.

I can't figure out how to twick the navigation stack in order to do this, and I would like to avoid setting the objects perception distance (obstacle range) to 0.

Thanks for your help,

Guido

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answered 2011-08-17 01:51:22 -0500

Eric Perko gravatar image

There are a few things you'll have to do. Firstly, you'll need to configure the costmaps with either a fake laser scanner (as Lorenzo Riano mentioned) or, I believe, just leave the obstacle_sources empty so that the costmaps assume there are no sensors. I haven't tested the latter, so I'm not sure if the costmaps will actually update if there are no sensors.

Secondly, if you want it to follow a user defined set of x,y points with no planning in between those points, you'll have to write your own BaseGlobalPlanner that just forwards your set of input points to the local planner. If you only need to get to one point at a time, you could try using the carrot_planner for global planning.

Once you have the entire path being output properly, you'll need to tune whichever BaseLocalPlanner you are using (dwa_local_planner, base_local_planner, etc) to prefer following the path over heading directly towards the goal. See Tuning Guide for more info (specifically look for the path_distance_bias and goal_distance_bias parameters)

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I will try this solution. Thanks you for the answer.
Guido gravatar image Guido  ( 2011-08-17 02:22:12 -0500 )edit
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answered 2011-08-16 23:00:29 -0500

You could create a fake laser that always returns very far away obstacles, and feed it into the navigation stack. Beware that the laser has return some values, otherwise the costmap won't update and everything will stall.

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Thank you for your answer. The problem then is that the navigation will go straight to the goal, it won't follow a given trajectory. I updated my question to be more specific.
Guido gravatar image Guido  ( 2011-08-17 00:34:38 -0500 )edit

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Asked: 2011-08-16 21:39:36 -0500

Seen: 458 times

Last updated: Aug 17 '11