Setting up tf for Hector SLAM

asked 2012-08-02 00:38:28 -0600

BenMa
76 ●10 ●10 ●15

updated 2012-08-02 03:56:58 -0600

Stefan Kohlbrecher

24361 ●173 ●299 ●444 https://www.energy-rob...

Hi, all,

I am trying to get my hokuyo laser node to work with hector_slam to produce realtime SLAM. I have installed hokuyo_node and the laser seems working properly. I also completed the hector_slam tutorial using the "Team_Hector_..bag" file. However, when I rosrun hokuyo_node and hector_slam(through a launch file), I just can't get it right. My launch file settings are as follows:

Then I went back to rerun the hector_slam tutorial, I use rxgraph to check what the nodes/topics are. Then, I found that a "/play node" (play back of the *.bag file in the tutorial) publish a '/tf' topic and "/hector_mapping" node subscribe to it. If I just rosrun hokuyo_node, then the "/hokuyo_node" just publish the '/scan' topic. I guess the problem is here. Can anyone elaborate a little more on this '/tf' and how to resolve it when using real laser scanners? THANKS A LOT.

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please share your launch file, i have a same problem too.

Messi ( 2013-06-08 05:15:12 -0600 )edit

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answered 2012-08-02 03:47:50 -0600

Stefan Kohlbrecher

24361 ●173 ●299 ●444 https://www.energy-rob...

updated 2012-08-02 22:23:39 -0600

Yes, the problem is related to tf not being available. To get an overview of how tf works you can have a look at the following links:

TF tutorials

Hector SLAM setup tutorial

The easiest option to make it work is manually starting a tf publisher that publishes the needed transform from the base_link that you want to have localized to the laser scanner frame. This can be done by adding the following to a launch file:

  <node pkg="tf" type="static_transform_publisher" name="base_to_laser_broadcaster" args="0 0 0 0 0 0 base_link laser 50" />

/edit: This is assuming you have set the hector_mapping parameters like this:

  <param name="pub_map_odom_transform" value="true"/>
  <param name="map_frame" value="map" />
  <param name="base_frame" value="base_link" />
  <param name="odom_frame" value="base_link" />

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answered 2012-08-02 16:35:13 -0600

BenMa
76 ●10 ●10 ●15

I added

<node pkg="tf" type="static_transform_publisher" name="base_to_laser_broadcaster"
      args="0 0 0 0 0 0 base_link laser 50"/>

into my launch file. But I always get the error "lookupTransform base_frame to laser timed out.... Frame /laser exists with parent /base_link. Frame /base_link exists with parent NO_PARENT." Is there something else missing? Really appreciate your help.

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Hi, updated my answer above. Please comment on answers if you have further questions, as further questions being added as answers tend to confuse people.

Stefan Kohlbrecher ( 2012-08-02 22:24:28 -0600 )edit

please share the launch file discussed above.

Messi ( 2013-06-08 05:49:42 -0600 )edit

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Setting up tf for Hector SLAM

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