I am learning ros_control and trying to create and use own controller. But controller spawner couldn't load it.

I created empty dumb controller:

namespace roscontrol_test
{

    class MyController : public  controller_interface::Controller<hardware_interface::PositionJointInterface>
    {
    public:
        virtual bool init(hardware_interface::PositionJointInterface *hw, ros::NodeHandle &n) override
        {
            return true;
        }

        virtual void starting(const ros::Time & /*time*/) override {}
        virtual void update(const ros::Time &time, const ros::Duration &period) override {}
        virtual void stopping(const ros::Time& /*time*/) override {}

    };

    PLUGINLIB_EXPORT_CLASS(roscontrol_test::MyController, controller_interface::ControllerBase);
}

I configure plugin.

controller_plugin.xml

<library path="lib/libmy_controller">
    <class
           name="roscontrol_test/MyController"
           type="roscontrol_test::MyController"
           base_class_type="controller_interface::ControllerBase">
        <description>This is an example ros_control plugin.</description>
    </class>
</library>

package.xml

...
<export>
    <roscontrol_test plugin="${prefix}/controller_plugins.xml"/>
</export>
...

I also test that pluginlib can load this plugin:

int main(int argc, char** argv)
{
    pluginlib::ClassLoader<controller_interface::ControllerBase> controller_loader("roscontrol_test", "controller_interface::ControllerBase");

    try
    {
        auto controller = controller_loader.createInstance("roscontrol_test/MyController");
        ROS_INFO("Plugin loaded");
    }
    catch(pluginlib::PluginlibException& ex)
    {
        ROS_ERROR("Failed to load plguin");
        ROS_ERROR(ex.what());
    }


    return 0;
}

And all is OK. Finally, I create simple robot and this is a YAML config:

arm:
  # publish all joint states
  joint_state_controller:
    type: joint_state_controller/JointStateController
    publish_rate: 50

  # position controllers
  pan_joint_position_controller:
    type: position_controllers/JointPositionController
    joint: pan_joint
    pid: {p: 100.0, i: 0.01, d: 10.0}

  tilt_joint_position_controller:
    #type: position_controllers/JointPositionController
    type: roscontrol_test/MyController
    joint: tilt_joint

But I faced with error while loading:

[ INFO] [1520931242.427358562, 0.308000000]: Loaded gazebo_ros_control.
[INFO] [1520931242.500081, 0.380000]: Controller Spawner: Waiting for service controller_manager/switch_controller
[INFO] [1520931242.503352, 0.383000]: Controller Spawner: Waiting for service controller_manager/unload_controller
[INFO] [1520931242.506296, 0.387000]: Loading controller: joint_state_controller
[INFO] [1520931242.517501, 0.398000]: Loading controller: pan_joint_position_controller
[INFO] [1520931242.531252, 0.412000]: Loading controller: tilt_joint_position_controller

[ERROR] [1520931242.534222608, 0.415000000]: Could not load controller 'tilt_joint_position_controller' because controller type 'roscontrol_test/MyController' does not exist.
[ERROR] [1520931242.534263585, 0.415000000]: Use 'rosservice call controller_manager/list_controller_types' to get the available types

[urdf_spawner-4] process has finished cleanly
log file: /home/garrus/.ros/log/12367bb2-269c-11e8-8a6d-94de802129d7/urdf_spawner-4*.log
[ERROR] [1520931243.535656, 1.414000]: Failed to load tilt_joint_position_controller
[INFO] [1520931243.536768, 1.415000]: Controller Spawner: Loaded controllers: joint_state_controller, pan_joint_position_controller
[INFO] [1520931243.542771, 1.421000]: Started controllers: joint_state_controller, pan_joint_position_controller

Why controller spawner couldn't load controller, but I can load it manually by pluginlib?