RViz not displaying TF frames for all active Crazyflies

[coenwerem]

Hi,

Using the Lighthouse Positioning System, with the enable_logging and enable_logging_pose parameters in the hover_swarm.launch file set to True, I am only able to track the poses of 2 out of 4 (chooser.py, allCrazyflies.yaml) active Crazyflies (see the tfframes_axes.png file). On RViz, I can also see only 3 CF frames checked under the TF display (see the tfframes_rviz.png file). Running rosrun tf view_frames outputs the following error:

Listening to /tf for 5.0 seconds
Done Listening
b'dot - graphviz version 2.43.0 (0)\n'
Traceback (most recent call last):
  File "/opt/ros/noetic/lib/tf/view_frames", line 119, in <module>
    generate(dot_graph)
  File "/opt/ros/noetic/lib/tf/view_frames", line 89, in generate
    m = r.search(vstr)
TypeError: cannot use a string pattern on a bytes-like object

I have checked that the /cf<id>/pose/ topics are active for all 4 CFs, so I am not sure where the problem is coming from. I am trying to implement a leader-follower flight routine, but this issue has prevented me from retrieving the pose of all the CFs using the Crazyswarm position() method, causing my script to fail.

Any help will be greatly appreciated.

Thanks.

tfframes_axes.png	tfframes_rviz.png

[coenwerem]

Here is the tf tree:

Apparently, tf is deprecated, so I had to use tf2 instead. From the image, only 2 CF frames are visible.

Thank you.

[whoenig]

We update tf whenever we publish a /cf<id>/pose message, see https://github.com/USC-ACTLab/crazyswarm/blob/master/ros_ws/src/crazyswarm/src/crazyswarm_server.cpp#L708-L714.

You could directly subscribe in your script to /cf<id>/pose (rather than using the position() method), if these topics give you all the information that you need. My guess is that some of the pose topics might not be updated at a reasonably high rate due to radio bandwidth limitations. If that's the case (check with ros topic hz), then switching to two radios (and two channels) might improve the situation.

[coenwerem]

Thanks for the response, @whoenig. I tried directly subscribing to the cf<id>/pose topics, but kept getting zero values, and couldn't get my subscriber to work (a problem on my part and not the package because rostopic echo cf<id>/pose works). As a result, I had to resort to using the position() method to expedite things.

You are right. Using rostopic hz /cf<id>/pose returns no new messages for /cf1/pose/ and /cf2/pose and actual values for cf3 and cf4 pose topics. I will try switching to two radios with individual channels to see if I get better results. Thanks!

[coenwerem]

Using two Crazyradios with different channels fixed the tf frames issue. Thank you, @whoenig!