problem of publishing a PoseStamped goal on the move_base_simple Topic

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I am new user of ROS and gazebo. Here is what I did: created a gazebo WorldPlugin. In the plugin, I created a publisher to publish a PoseStamped goal to the topic move_base_simple/goal. When I select a model in gazebo scene, I call the publisher to publish a message. But I do not see the robot moving to the selected model. The ros navigation setup is based on the setup in turtleb0t3_navigation.launch. I dod see the PoseStamped published by rostopic echo. I wonder if publishing PoseStamped is a right way in WorldPlugin or not? Thank you all for any help!