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Understanding navigation stack

asked 2011-04-19 18:50:13 -0500

Jack Sparrow gravatar image

Hi,

I have trouble of understanding how navigation stack works. After days of debugging code to work with navigation stack I have concluded that its either problem in tf or I dont really understand how navigation stack work. Specifically I have a couple of questions/problems:

  1. When I change tf to some reasonable parameters from my initial parameter, that should work, I get that my laser sensor is out of range, exactly - on some negative x or y positions. Does navigation work only with positive x and y?
  2. My simulation is left oriented, so this might be problem with getting to work with navigation. But, when I left x an y signed positive or negative as I get from my odometry or change x to -x to compensate left-right orientation my robot's footprint moves in rviz always in the same direction. Should't be that in opposite direction? Is navigation right oriented? What problem I might get with left-right orientations?
  3. My main problem is that when the robot in, let's say, position (x,y,orient)=(5,5,0) /map frame, and I send goal from rviz in /map frame to (6,5,0), robot gets positive x command velocity from navigation, but when the goal point is reached robot remains to move in +x direction, the output from navigation (cmd_vel) remains the same as before reaching goal. Same problem with y direction, both + and -y.

Some help needed, thanks.

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answered 2011-04-20 04:58:19 -0500

eitan gravatar image

To add a little bit of clarification on item #1:

The navigation stack will work with negative values for coordinates in a given frame depending on the configuration of its costmaps. Is sounds like perhaps your robot is not localized properly, causing the laser sensor to be outside of the specified map. If you're using AMCL, have you made sure to set the "initialpose" of the robot?

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Yes, 1. was a problem with localization :)
Jack Sparrow gravatar imageJack Sparrow ( 2011-04-28 09:22:25 -0500 )edit
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answered 2011-04-19 23:57:13 -0500

dornhege gravatar image
  1. Navigation should work with negative values.
  2. Have a look at the Coordinate Conventions. You will have to send out data in a right-handed coordinate system.
  3. I guess when you fixed 2., this might resolve.
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Asked: 2011-04-19 18:50:13 -0500

Seen: 283 times

Last updated: Apr 20 '11