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Ros Multiple machine Gmapping fails

asked 2013-02-04 18:24:12 -0600

snakehaihai gravatar image

updated 2013-02-04 18:24:51 -0600

I`m running one ground processing PC called snake. and another computer on Robot call UAV. Communication works fine. I can run hokuyo node on UAV and see the data on the data by using rostopic echo in PC snake

Problem is when I launch the laser scan matcher and Gmapping using launch file on PC snake. I can see laser on RVIZ by selecing /laser frame. but I can`t see the map at all.
After connect laser to PC snake and run hokuyo and mapping launchfile. It works fine

my launch file is <launch> <machine name="snake" address="snake" user="snake" password="snake" ros-root="$(env ROS_ROOT)" ros-package-path="$(env ROS_PACKAGE_PATH)" default="false"/>

<node pkg="laser_scan_matcher" type="laser_scan_matcher_node" name="laser_scan_matcher_node" output="screen"> </node>

<node pkg="tf" type="static_transform_publisher" name="laser_link" args="0.25 0.0 0.68 0.0 0.0 0.0 /base_link /laser 40"/> <node pkg="tf" type="static_transform_publisher" name="Base_odom_link" args="0 0.0 0 0.0 0.0 0.0 /base_link /odom 40"/>
<node pkg="gmapping" type="slam_gmapping" name="gmapping" output="screen">
</node> <node name="rviz" pkg="rviz" type="rviz"/> </launch>

And there is no error at all but

MessageFilter says that MessageFilter : Dropped 100.00% of messages so far. Please turn the [ros.gmapping.message_notifier] rosconsole logger to DEBUG for more information.

the map doesn`t comes out

any idea why?

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answered 2013-02-04 19:21:52 -0600

updated 2013-02-04 19:22:37 -0600

If multiple machines are involved the first thing to do (see also Network Setup) is always checking

  1. if basic communication works between them by sending data around on some topic. Seems to work from what you describe
  2. if the clocks of all computers are properly synchronized. This is commonly done using chrony. Some more info can be found here and here. A search on this site will probably also turn up some useful discussion.

To me your issue sounds like it could be related to a time offset between machines.

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  1. I can see scan and shift on rviz for different frame on all of my computers. Means wireless network is function fine. Scan and shift of tf can be observed. But only Gmapping is not running. suspect is the 2nd problem you were mentioning
snakehaihai gravatar imagesnakehaihai ( 2013-02-04 23:14:12 -0600 )edit

Just tested. Ok there are something appears on the screen now. Looks like a map but it`s not published well. there is an error

snakehaihai gravatar imagesnakehaihai ( 2013-02-04 23:36:31 -0600 )edit

Ok it`s the timing problem. roswtf gives WARNING Received out-of-date/future transforms: * receiving transform from [/laser_scan_matcher_node] that differed from ROS time by 16.823852148s

snakehaihai gravatar imagesnakehaihai ( 2013-02-04 23:42:51 -0600 )edit
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answered 2019-01-08 04:35:22 -0600

Time differences between machines is the problem. use automatic clock setting in both machines to solve the roswtf warning.

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answered 2013-02-04 18:32:49 -0600

Echo /map topic on terminal, and see whether map data is being published or not. If that is working then there must be some problem with tf. Check the frame_id of map make that as fixed frame in rviz.

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I echoed map. Nothing comes out. But if I move the laser. I can see the frame shift in RVIZ . what could be the tf problem ? the same launch file works fine when using with hokuyo node on one PC

snakehaihai gravatar imagesnakehaihai ( 2013-02-04 18:39:31 -0600 )edit

Then check the inputs to gmapping whether it subscribed to correct sensor topics and as @Stefan said check the communication,run rostopic list on both machines and see whether topics are getting published correctly or not.

ayush_dewan gravatar imageayush_dewan ( 2013-02-04 19:47:23 -0600 )edit

Laser are published across the network correctly. rostopic info shows scan and tf are being subscribed correctly by matcher and gmapping. I double checked the scan matcher Pose2D is generated correctly. Only Gmapping is not running. No matter is in launch or rosrun. it hangs there

snakehaihai gravatar imagesnakehaihai ( 2013-02-04 23:12:02 -0600 )edit

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Asked: 2013-02-04 18:24:12 -0600

Seen: 772 times

Last updated: Feb 04 '13