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So I have made a ROS plugin to make a new library and I am trying to test the library's methods by executing one of them by a node in a different workspace. when I execute the node this happen: [ERROR] [1719244165.939620169]: The plugin failed to load. Error: According to the loaded plugin descriptions the class ik_solver_plugin::iKinematicPlugin with base class type ik_solver_plugin::iKinematicPlugin does not exist. Declared types are

I have tried many options to check the CMakeLists.txt file or the package.xml file or the package_description.xml file but everything seems made correctly to me. What causes this error and how could i fix it?

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  • $\begingroup$ What app is the plugin for? Which release of ros? Can you give us a url to a github.com repo containing this catkin package? $\endgroup$
    – Mike973
    Commented Jun 28 at 11:14
  • $\begingroup$ I wanted to make an IK solver but I was encountering this error, so in order to compare my work with something else I used the kdl_kinematics_plugin and still encounter the same ERROR. I have only modified the CMake file. I do not know if the issue lays in the CMakeLists.txt file or else. My idea is to have the IK solver developed in one workspace completed with shared library and have a ROS node in another workspace. Here the link for the github with the plugin and the node. catkin_ws_10 is the Ik solver and catkin_ws_11 has the node. github.com/Tommaso2025/Plugin $\endgroup$
    – Tommaso Pignata
    Commented Jun 28 at 20:54

1 Answer 1

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Package Visibility

If you are going to build in separate catkin_workspace in your user account, and then use them at the same time, you need to make the package(s) available by executing cmd source devel/setup.bash in the correct order.

So the steps for your scenario look like:

  • source /opt/ros/noetic/setup.bash
  • build the catkin_ws_10 workspace
  • source devel/setup.bash # for catkin_ws_10
  • build the catkin_ws_11 workspace
  • source devel/setup.bash # for catkin_ws_11
  • execute the app in catkin_ws_11

That said, my opinion is that this approach is more complicated than necessary, because you can simply put the code for both ik_load and kdl_kinematics_plugin side-by-side in the same catkin_ws/src/ directory during development.

Other Fixes

  1. You have the wrong filename in kdl_kinematic_plugin/CMakeLists.txt:
# Install the plugin description file to a custom directory
 install(FILES
-  plugin_description.xml
+  kdl_kinematics_plugin_description.xml
 )
  1. In ik_load/CMakeFiles.txt, your catkin_package() statement should contain no statements:
catkin_package(
-  INCLUDE_DIRS include
-  LIBRARIES ik_load
-  CATKIN_DEPENDS roscpp pluginlib geometry_msgs moveit_core moveit_kinematics kdl_kinematic_plugin
)
  1. Your xml file has errors. You have:
<library path="lib/libmoveit_kdl_kinematics_plugin">
  <class name="kdl_kinematics_plugin/KDLKinematicsPlugin"
         type="kdl_kinematics_plugin::KDLKinematicsPlugin"
         base_class_type="kinematics::KinematicsBase">

The "path" property should not have the "lib/" prefix, and the value should be the name of the .so file in catkin_ws/devel/lib/, so "libkdl_kinematics_plugin" for your package.

The "name" property should be removed completely (it's now an optional attribute.)

  1. In your load_ik.cpp, you are specifying the wrong class name to the ClassLoader. The second argument is the name of the base class, not the derived class.
  pluginlib::ClassLoader<kinematics::KinematicsBase> load_ik("kdl_kinematics_plugin", "kdl_kinematics_plugin::KDLKinematicsPlugin");

Have you enabled Debug logging for your load_ik ros node? I see some useful messages being logged by pluginlib.

Even with these 4 fixes, your node still doesn't work, but it looks to me like the plugin portion is being successfully loaded and executed.

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  • $\begingroup$ Hello @Mike973 I have tried to apply the changes in the kdl_kinematic_plugin/CMakeLists.txt and ik_load/CMakeFiles.txt. Even update the githib: github.com/Tommaso2025/Plugin/tree/master I also tried to combine all toghether in the same workspace as you suggsted for package visibility problem but the error is always there. I was wandering if you can give me some feedback about the kdl_kinematics_plugin_description.xml and plugin_description.xml. In this wiki.ros.org/pluginlib/Troubleshooting the point 1.4 says that this kind of error is caused by the plugin.xml file. $\endgroup$
    – Tommaso Pignata
    Commented Jun 30 at 17:52
  • $\begingroup$ I updated my answer to add fixes 3 and 4. $\endgroup$
    – Mike973
    Commented Jul 1 at 12:55
  • $\begingroup$ Hello @Mike973 I have updated the code with the fixes you mentioned, as you said the node still does not work. I have enabled the Debug logging but the most useful of it is this: [DEBUG] [1720046659.811653763]: Attempting to create managed instance for class kdl_kinematics_plugin::KDLKinematicsPlugin. [DEBUG] [1720046659.811679096]: Class kdl_kinematics_plugin::KDLKinematicsPlugin has no mapping in classes_available_. I do not understand entirely these messages. To me they are saying that the issue is within the plugin_description.xml or package.xml but to me they are both correct. $\endgroup$
    – Tommaso Pignata
    Commented Jul 6 at 11:35

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