Hi,guys!I am a new user for gazebo.I just want to control the speed of arm end.My arm is a 6-DOF,and my gazebo is GAZEBO7.I just want use jacobi matrix to get the joint speed,so maybe my real problem just want to a example cpp procedure (or other language) how to set_velocity() in GAZEBO7.Can everyone give some examples just like real-time speed control in GAZEBO7.Thanks,I get stuck this problem almost one month.