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Gmapping Issue

I am trying to create a 2D map of a hallway using slam_gmapping and I have not been successful in getting an accurate map.

From what I see, the Odometry appears to be drifting and the slam algorithm is not able to close the loop.

I am trying to figure out if the problem is with the settings of the slam_gmapping parameters or the Odometry data coming from the robot. Any leads, suggestions?

Asked by pnambiar on 2014-07-08 11:19:46 UTC

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It would help to state your current parameter set, the computation power you have, which sensor you use, and how the environment looks.

Asked by dornhege on 2014-07-08 11:34:10 UTC

Hokuyo URG-04LX. 2.4GHz dual-core Intel Core i5 processor. The environment is a long hallway with an intersecting side hallway. During mapping, the Robot was tele-operated from one end of the hallway and was brought back to the same location. In the resulting map, the side hallway did not match(there were two - one next to another). I have a schematic. But cannot post it due to insufficient karma.

This is default parameters in segbot_navigation 

<param name="odom_frame" value="odom"/>
<param name="map_update_interval" value="30.0"/>
<param name="maxUrange" value="5.0"/>
<param name="sigma" value="0.05"/>
<param name="kernelSize" value="1"/>
<param name="lstep" value="0.05"/>
<param name="astep" value="0.05"/>
<param name="iterations" value="5"/>
<param name="lsigma" value="0.075"/>
<param name="ogain" value="3.0"/>
<param name="lskip" value="0"/>
<param name="srr" value="0.01"/>
<param name="srt" value="0.02"/>
<param name="str

Asked by pnambiar on 2014-07-09 07:58:46 UTC

Not able to post the parameters for some reason. But you can view it on gmapping.launch (segbot_navigation) package

Asked by pnambiar on 2014-07-09 08:01:13 UTC

Define long. Long hallways are a common problem for laser-based SLAM. If there are no features it will rely on odometry.

Asked by dornhege on 2014-07-09 08:23:54 UTC

228ft X 7.5 ft. Does that mean the odometry is not accurate? Will a UTM-30LX give better results?

Asked by pnambiar on 2014-07-10 07:05:27 UTC

Answers

The first thing you need to do before try to make a SLAM is to calibrate. Here in ROS Answers there are several topics about that. Since your problem is that the map is not closing, you can run some tests: Try to go forward into a corridor, rotate 180º and go back to the start point while running gmapping. If the robot creates another corridor on the way back, the problem is the calibration. and you should run it several times until get better results for laser and odometry. If you already have a map, try to send a GOAL to the robot while using amcl_demo and watch the laser in the map (the white line). Again, if the laser exceed the wall, i'm almost sure the problem is with the laser and you need to calibrate it.

Asked by Thiagopj on 2014-07-08 11:42:18 UTC

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Yes I have done that. Started from one location and brought it back to the same location and the side corridor appears twice. How do you calibrate the laser?

Asked by pnambiar on 2014-07-09 08:03:32 UTC

I don't know how this work for Hokuyo, but for sure thats the problem and when you calibrate it correctly you'll get better results. Try to find tutorials and search more about your laser. Good luck! :)

Asked by Thiagopj on 2014-07-09 08:09:22 UTC

<param name="

Asked by pnambiar on 2014-07-09 07:59:17 UTC

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