Unable to roslaunch laserscan_multi_merger when launch file is run in a different package

[yungchuenng]

Hi!

I am running the ira_laser_tools on a ROS Kinetic system. In my workspace, I have a package i.e. "test_robot", in which a launch file that starts up my ROS system would include a launch file that calls the ira_laser_tools laserscan_multi_merger (in the same directory) which has the code as follows:

<launch>
    <node pkg="ira_laser_tools" name="laserscan_multi_merger" type="laserscan_multi_merger" output="screen">
        <param name="destination_frame" value="/base_link"/>
        <param name="cloud_destination_topic" value="/merged_cloud"/>
        <param name="scan_destination_topic" value="/scan"/>
        <param name="laserscan_topics" value ="/scan1 /scan2" />
        <param name="angle_min" value="-3.14"/>
        <param name="angle_max" value="3.14"/>
        <param name="angle_increment" value="0.0043"/>
        <param name="scan_time" value="0.0333333"/>
        <param name="range_min" value="0.10"/>
        <param name="range_max" value="50.0"/>
    </node>
</launch>

In this situation, even though the laserscan_multi_merger node (in the same workspace) seems to have launched without any error thrown, this node does not seem to be working correctly as when I tried to get the output,

rostopic echo /scan

It gets stuck and nothing happens at all (my inputs /scan1 and /scan2 are working correctly).

However, when I

roslaunch ira_laser_tools laserscan_multi_merger.launch

after I roslaunch my ROS system (still including the launch file to run the ira_laser_tools node in the "test_robot" launch file), the laserscan_multi_merger node from previously gets killed, and the new laserscan_multi_merger node works fine and I am able to get /scan data.

The reason for including the launch file that calls the ira_laser_tools laserscan_multi_merger in my own launch file is so that I can run all nodes at once from just one main launch file.

Hence, the issue is that when trying to launch the laserscan_multi_merger node from another package other than from ira_laser_tools, the laserscan_multi_merger node does not seem to work correctly.

Would deeply appreciate anyone's assistance in this matter! Thank you in advance!!!

[pietrocolombo]

I think the problem is that when starting the multi_merger the topics / scan1 and / scan2 are not published yet so you should see in the terminal "Not subscribed to any topic." this line

because the search for available topics is done only at startup

[yungchuenng]

Thank you for your prompt response! Will get back to you regarding this when I return to working on my project in a few days! I will try to workaround it and update here again.

[yungchuenng]

Hi!

I actually did not notice the "Not subscribed to any topic" line, but there was a ROS warning message:

Transformer::setExtrapolationLimit is deprecated and does not do anything

So it seemed the code did managed to continue running after.
Regardless, I managed to solve the issue by adding the following lines in the source code of laserscan_multi_merger.cpp before the function "laserscan_topic_parser()" is run in LaserscanMerger::LaserscanMerger():

boost::shared_ptr<sensor_msgs::LaserScan const> messsage;
message = ros::topic::waitForMessage<sensor_msgs::LaserScan>(last_laser_topic, node_, ros::Duration(100));

However, there was another issue that I encountered.

After I catkin_make the ira_laser_tools in a workspace i.e. "workspace_1", running my roslaunch file in workspace_2 that includes "laserscan_multi_merger.launch" will always find the ira_laser_tools package from workspace_1 instead of from workspace_2, in which I have also catkin_make ira_laser_tools, even though I have sourced the setup.bash of workspace_2.

May I kindly ask if there is a way to go about this? That is even if I have the ira_laser_tools in different workspace, I want the ira_laser_tools in the local workspace to run.

Much thanks!