Hello guys, I am new to ROS, Gazebo and PX4. I am working on robot arm equipped USV. I edited the existing USV (boat) sdf file in PX4 by adding a robot arm on it. I want to control the robot arm from the ROS. And in order to control the robot arm on the USV I need to add a plugin and I need to write a joint controller in ROS. I am a beginner and I am confused on how to do that.