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Failed to build tree: child link [base_laser_mount] of joint [laser_mount_joint] not found

Hi, I'm trying to get the husky robot simulation up and running with https://github.com/husky/husky

I've installed all the necessary packages, but upon calling 

roslaunch husky_gazebo husky_empty_world.launch

I am met with the following error

ERROR] [1591406797.536308608]: Failed to build tree: child link [base_laser_mount] of joint [laser_mount_joint] not found

I believe it's talking about this following bit of code, husky.urdf.sacro in husky_description

  <xacro:if value="$(arg laser_enabled)">

    <sick_lms1xx_mount prefix="base"/>

    <sick_lms1xx frame="base_laser" topic="scan" robot_namespace="$(arg robot_namespace)"/>

    <joint name="laser_mount_joint" type="fixed">
      <origin xyz="$(arg laser_xyz)" rpy="$(arg laser_rpy)" />
      <parent link="top_plate_link" />
      <child link="base_laser_mount" />
    </joint>

  </xacro:if>

However, I'm not sure where baselasermount isn't defined, especially because I didn't tamper with the files from the github.

Asked by ildaniel on 2020-06-05 20:32:32 UTC

Comments

Hi @ildaniel,

Have you changed something in the repository, because I have cloned it, launched the simulation and there were no errors in the process. That is weird.

Actually, I have a proper tf_tree that connects top_plate_link --> base_laser_mount --> base_laser.

Asked by Weasfas on 2020-06-06 06:13:26 UTC

Thanks for your response. Could this be because I'm runnning Ubuntu 20.04 LTS and ROS Noetic? I grabbed the melodic-devel branch from github. And just to be clear about what I'm doing I cloned the github contents into ~/husky_ws/src/

cd ~/husky_ws/
catkin_make
source ~/husky_ws/devel/setup.bash/
roslaunch husky_gazebo husky_clear_world.launch

and then I run into missing resources such as

resource not found: lms1xx

which I install, but then there's always another error it seems like. Could this be a fundamental problem with my ROS installation or how I'm calling things above?

Asked by ildaniel on 2020-06-06 11:43:05 UTC

Well, I do not know if there is an issue regarding the ROS distribution, but I think it should not be a problem of compatibility. But, what I did is cloning both repos, the one containing the husky_description and the one with the lms1xx_description, sourced the workspace and launched with roslaunch husky_gazebo husky_empty_world.launch. Then no error appears. As a way of "debugging" what is happening you could just run a virtual enviroment with a ROS Noetic/Melodic and try to reproduce your steps. By the way, how you installed the lms1xx package? from apt? lms1xx repository contains a Noetic branch, but the xacro file you are using: sick_lms1xx.urdf.xacro is the same as the one Melodic uses, so it is compatible with the Melodic branch of husky description.

Asked by Weasfas on 2020-06-06 14:40:59 UTC

So I tried following the steps on a different machine on 18.04.4 LTS and ROS Melodic and found no issues. Maybe I unknowingly completed the steps in a different way, but regardless this allowed me to get through it. Thank you for your help!

Asked by ildaniel on 2020-06-07 13:39:40 UTC

Great!, glad I helped you. Cheers

Asked by Weasfas on 2020-06-08 04:15:42 UTC

Hello @ildaniel ! I have the same problem. Were you able to solve the problem in Ros Noetic? Thanks!

Asked by marihm on 2020-07-11 23:17:12 UTC

I'm using ROS Melodic, but the following steps should work smoothly, let me know if they do:

cd
mkdir -p test_ws/src
cd test_ws/src
git clone https://github.com/husky/husky
cd ~/test_ws
rosdep install --from-paths src --ignore-src -r -y
catkin_make
source ~/test_ws/devel/setup.bash
roslaunch husky_gazebo husky_empty_world.launch

After installing all necessary dependencies I've recovered from many issues

Asked by ildaniel on 2020-07-12 12:08:51 UTC

Thanks for your answer! I had no luck, same error appears despite I had followed your suggestion. I have looked into the .xacro files and everything seems to be ok, the base_laser_mount link is defined in the sick_lms1xx.urdf.xacro file which is located in lms1xx/urdf. I have just commented the lines which defines the laser links and joints in the husky.urdf.xacro file and I have managed to load Husky in Gazebo without the laser. I think it has something to do with ROS Noetic because I have also been working with ROS Melodic and I didn't have any problems.

Asked by marihm on 2020-07-12 23:28:06 UTC

Answers

This error seems to arise only on noetic:

First of all, if you want to simulate Husky in Gazebo, make sure you clone hector_gazebo_plugins, husky_gazebo, husky_control, husky_description, LMS1xx and interactive_marker_twist_server into the src/ folder of your workspace.

Once you have done that, build your workspace.

Finally, edit line 142 and line 144 in the husky_description folder of the husky repository:

FROM:

    <sick_lms1xx_mount prefix="base"/>

    <sick_lms1xx frame="base_laser" topic="scan" robot_namespace="$(arg robot_namespace)"/>

TO:

    <xacro:sick_lms1xx_mount prefix="base"/>

    <xacro:sick_lms1xx frame="base_laser" topic="scan" robot_namespace="$(arg robot_namespace)"/>


Note: Please let me know if this solution doesn't work out for you. If in case it does, feel free to upvote my answer.

Asked by LSD on 2020-10-29 14:51:43 UTC

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