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Hi Everyone, I installed the hector_quadrotor from source (hydro and 1.9 gazebo) and launched the file “quadrotor_empty_world.launch”. Everything seems to be ok, empty_world with one quadrotor, until I provided to the quadrotor a velocity command using “rostopic pub” and the quadrotor doesn’t move at all. I verified via “rqt_graph” that gazebo is connected to the right topic (/cmd_vel) and also verified if the data is published on the topic. Everything seems to be normal and I don’t know what else I can check. Any idea about this problem? Thank you for any help with this issue


Originally posted by Robert on Gazebo Answers with karma: 9 on 2014-05-06

Post score: 0

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Hi for me this command works:

rostopic pub /cmd_vel geometry_msgs/Twist '[0, 0, 1]' '[0, 0, 0]'

The problem might be that your quadcopter is not flying.

If the quadcopter is on the ground it needs a Twist with positive linear.z value. The program will print Engaging motors! As soon as you land on the ground the programm will print Shutting down motors! Which will mean you have to start it again.

Let me no if this does not solve your problem...


Originally posted by evilBiber with karma: 881 on 2014-05-07

This answer was ACCEPTED on the original site

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Original comments

Comment by Robert on 2014-05-07:
Hi evilBiber, thanks a lot for your tip. it worked and quadrotor took off. But I observed after awhile the quadrotor get frozen (motionless) on the space. I checked the quadrotor' pose via "rostopic echo /ground_truth/state" and the pose values are the same after reaching certain altitude (~952m). Also, I provided 0 command velocity (rostopic pub /cmd_vel geometry_msg/Twist '[0, 0, 0,]' '[0, 0, 0]') to the quad to land on the ground but the quad stayed motionless. Do you know how to land the quad on the ground?. Thanks a lot again

Comment by evilBiber on 2014-05-08:
you have to use negative z values for going down.

Comment by Robert on 2014-05-08:
Thanks alot again! your tip worked and quad landed

Comment by vinaykumar on 2015-04-17:
Thanks Robert! This helped me! :)

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