IkFast Plugin fail to load

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Hello, guys, i generated a iKFast plugin for moveit, but i met a problem. when i launch panda_moveit_config demo.launch, everything is ok, but when i rosrun my node, which will use move_group.move() function to move robot to targeted pose, and it will turn out the following error( plugin fail to load), but i can still plan my robot.

Output in console：

[ERROR] [1565683587.994017715]: The kinematics plugin (panda_arm) failed to load. Error: According to the loaded plugin descriptions the class panda_arm_panda_arm_kinematics/IKFastKinematicsPlugin with base class type kinematics::KinematicsBase does not exist. Declared types are  cached_ik_kinematics_plugin/CachedKDLKinematicsPlugin cached_ik_kinematics_plugin/CachedSrvKinematicsPlugin kdl_kinematics_plugin/KDLKinematicsPlugin lma_kinematics_plugin/LMAKinematicsPlugin srv_kinematics_plugin/SrvKinematicsPlugin trac_ik_kinematics_plugin/TRAC_IKKinematicsPlugin
[ERROR] [1565683587.994133629]: Kinematics solver could not be instantiated for joint group panda_arm.

i have looked for the plugin_descriptionsfile and the package.xml . i think it has added all the required things in my description file for plugin:ik_kinematics_description.xml：

<?xml version='1.0' encoding='UTF-8'?>
<library path="lib/libpanda_arm_panda_arm_moveit_ikfast_plugin">
  <class name="panda_arm_panda_arm_kinematics/IKFastKinematicsPlugin" type="ikfast_kinematics_plugin::IKFastKinematicsPlugin" base_class_type="kinematics::KinematicsBase">
    <description>IKFast61 plugin for closed-form kinematics</description>
  </class>
</library>

in my package.xml:

  <export>
    <!-- Other tools can request additional information be placed here -->
    <moveit_core plugin="${prefix}/panda_arm_panda_arm_moveit_ikfast_plugin_description.xml"/>
  </export>

and i cmd rospack plugins --attrib=plugin moveit_core, it outputs following, the plugin is already register

moveit_planners_ompl /opt/ros/kinetic/share/moveit_planners_ompl/ompl_interface_plugin_description.xml
moveit_ros_control_interface /opt/ros/kinetic/share/moveit_ros_control_interface/moveit_core_plugins.xml
panda_arm_ikfast_panda_arm_plugin /home/xcell/ikfast_ws/src/panda_arm_ikfast_panda_arm_plugin/panda_arm_panda_arm_moveit_ikfast_plugin_description.xml

i dont know where does it problem ?can you help me to solve this problem thank you in advance