# No obstacles detected in particular region on the map?

Hi folks,

I've got another strange behavior here. Maybe somebody can help me figure out what's causing it. I'm simulating a robot that is moving in a mostly static environment. However, it's trying to detect obstacles by its IR sensors. That's working like a charm in most of the map except the region behind the black line in the following image:

20130922_obstacles_line.png

You can see the inflated obstacles in the picture as well. The robot has already been in the area behind the black line and should have detected the obstacles there as well (the map is completely symmetrical). The white points show the "pointcloud" that's generated by the IR sensors. So this data seems to be correct. But still they aren't interpreted as obstacles in the region behind the black line. And I'd really like to know why...

So if there's any code or configuration you need to see to help me solve this, just leave a comment and I'll append the corresponding file.

EDIT 1: I figured out that it isn't a specific region on the map but instead a specific distance from the frame the point cloud is assigned to.

pc.frame_id = "/odom";


The maximum distance from that frame in which obstacles are detected is about 2.5 meters (measured in rviz). Where do I set this value?

Thanks a lot!

Cheers, Hendrik

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Alright, I figured it out. The point cloud was hooked up to the wrong frame. I translated the points to the global frame before. Now I've put them into the frame of the robot, changing the translation accordingly and it's working. My robot now detects obstacles farther away than 2.5 meters from /odom (about 2.5 meters from /base_link that is, which is my robot's base frame).

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