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trouble getting an accurate map with TurtleBot

asked 2011-11-11 04:14:10 -0500

hxorn00b gravatar image

updated 2011-11-11 16:54:17 -0500

mmwise gravatar image

Any tips on getting an accurate map with the turtlebot gmapping app. All the maps I have made so far don't ressemble the actual room. Does the bot need to be calibrated every time before you make a map? I've been calibrating it against a wall and then picking it up to another area to map. Is that OK? Also are there any limitations to the volume of space it can map? Can it map for instance a large hall like room / gym?

Thanks in advance for your help.

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How to integrate VSALM map with semantic map, so robot be able to navigate in the envitroment and also know load seamntics in visualization convas ??!

آمال gravatar image آمال  ( 2012-12-01 12:59:55 -0500 )edit

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answered 2011-11-11 16:52:40 -0500

mmwise gravatar image

updated 2011-11-12 07:02:21 -0500

Before mapping with the TurtleBot calibration is required. At this point I would suggest upgrading your TurtleBot to electric (http://www.ros.org/wiki/Robots/TurtleBot/electric/Robot%20Upgrade), it will make storing calibration much easier.

Once you upgrade, sudo service turtlebot start will be launching the turtlebot.launch file in /etc/ros/electric. All you need to do is edit this file after calibration and your calibration paramenters will be stored permanently. You shouldn't need to calibrate your TurtleBot very often.

After you calibrate you can make a map. It is important to note that the TurtleBot has difficulty staying localized in large open spaces (anywhere it can not see a wall or furniture with in 2-3 meters). In my home I have a relatively open floor plan and was able to map the 500 sq ft without trouble.

When making a map you need to remember that the algorithm is doing scan matching (trying to match up scans as it moves and checking to see if it's closed the loop). So it is important to be methodical when making a map especially with a TurtleBot since it has poor odometry.

To start when making a map with the TurtleBot, you should drive the perimeter (near walls and furniture) of a room several times in one direction at an average pace (don't go too slow, the TurtleBot odometry is the worst when driving slow). In the map you should see the walls and the like filling in and looking consistent after 3 or 4 laps around a room. Then branch out into another area and do some laps there and then come back to your original area. Basically you are trying to see the same features over and over again as you make the map.

After you've driven in one direction around your house, then turn the TurtleBot around and drive in the counter direction to fill in the missing areas. Then finally your map should look pretty good and you can roam a little to fill in the middle area of a room away from the perimeter.

It may take several attempts to get it right but don't give up. Many people have made nice maps of their homes. Below is the map of my home and you can see other people's maps if you search on youtube. As you can see in my home I have a very large room that is about 20ft x 15ft and was able to make a decent map. image description

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How to integrate between this map and semantic map ?!

آمال gravatar image آمال  ( 2012-12-05 05:48:45 -0500 )edit
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answered 2011-11-11 11:37:03 -0500

Mac gravatar image

GMapping (and, in fact, all 2D-scan-based mapping techniques) are deeply dependent on the quality of the data that they work with; in particular, it's very important that the scans be unambiguous, which is quite hard when using a Kinect for gmapping (where the short range and narrow field of view make it very hard to get unambiguous scans).

While mapping, do your best to always be able to see things (say, a wall) and have non-trivial structures, like wall corners, in view while you do this. Anecdotal evidence suggests that mapping anything larger than a medium-sized room with Turtlebot (using the Kinect in this way) is impractical, because of the sensor limitations.

On the other hand, if you mount up a laser rangefinder, that's an entirely different story...

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answered 2012-05-03 12:25:26 -0500

rohan gravatar image

I tried mapping a square room and the maps are not at all good.

One thing that I noticed was that when the turtlebot returns back to the same place in the room , it doesn't come back to the same point in the map.

Is it a localization problem? or it is a square room so it is having problems doing it?

I mapped it by going around the perimeter and then the other way round but still cant achieve a good map.

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Asked: 2011-11-11 04:14:10 -0500

Seen: 7,479 times

Last updated: May 03 '12