Fiducial Follow error


I find that the magnitude does not respond to the target 49. I performed the following test after ssh to the robot.
raspistill -o test.jpg
Took a look at the test.jpg and it showed nothing unusual. I believe the raspberry pi cameral is functioning as expected

As instructed I ran the command

sudo systemctl stop magni-base

and then the command

roslaunch magni_demos fiducial_follow.launch

As soon as I placed the default target “49” in front of the camera the output came to the screen which I attempted to capture partially before killing the
It appears that the Fid 49 is actually identified but there appears to be an error related to “base_link” not existing


traceback (most recent call last):
File “/home/ubuntu/catkin_ws/src/demos/fiducial_follow/nodes/”, line 151, in newTf
tf = self.tfBuffer.lookup_transform(“base_link”, self.target_fiducial, imageTime)
File “/opt/ros/kinetic/lib/python2.7/dist-packages/tf2_ros/”, line 87, in lookup_transform
return self.lookup_transform_core(target_frame, source_frame, time)
LookupException: “base_link” passed to lookupTransform argument target_frame does not exist.
Could not get tf for fid49
[ INFO] [978312395.092011143]: Got image 422
[ INFO] [978312395.113678904]: Detected 1 markers
[ INFO] [978312395.115822497]: Detected id 49 T -0.05 -0.11 0.66 R 0.63 3.04 0.09
[ INFO] [978312395.115943851]: angle 3.102972 axis 0.202755 0.978818 0.028400
978312395066530154 978312395117108941

Fid 49 -0.046404 -0.106144 0.657721 0.202717 0.978635 0.028395 0.019309



Try running it again after rebooting,
but this time don’t run sudo systemctl stop magni-base.

This command is longer needed, and the documentation needs to be updated.



Thanks Rohan that sorted out the problem!
I took the mangi for a little spin around the house and it performed as advertised. Is there a way to gracefully stop the process other than control-c (or via a hardware reset button)? Also once launched, does the raspberry pi need to be connected wirelessly to the ubuntu workstation?


Great! Documentation has been updated.

“Ctrl-C” is the graceful shutdown :slight_smile:

They don’t need to remain connected, but if the ssh connection drops, the process will die.

To prevent this, before launching run screen, and then run the launch. Then you can detach from this session with “Ctrl-A” followed by “D”.

To reattach (to analyze output or gracefully stop) run screen -r.