Getting real-time CF position data using cflib/Crazyswarm ROS

[coenwerem]

Hello all,

I recently started working on a swarm project with the Crazyflie 2.1 quadcopter. Using the excellent and very helpful Crazyswarm ROS package, I have been able to successfully fly 4 CFs to custom waypoints by modifying several scripts from the Crazyswarm ROS package. However, for the script to work as intended, I currently have to specify the real starting positions of the CFs in the inertial frame using the allCrazyflies.yaml file. What I want to be able to do is to fly the 4 CFs to custom points in 3D space without hardcoding their initial positions. That is, can I programmatically obtain the real-time position data of the CFs using either the Crazyswarm ROS package or cflib to use that in the script instead? I have read through the Crazyswarm and cflib docs without any luck. I also tried using the methods in the position_hl_commander.py cflib script, but don't seem to be getting anywhere as I am running into some errors.

I am using the V1 Lighthouse Positioning System for external localization.

Any help will be appreciated!

Many thanks

[whoenig]

LightHouse is decentralized tracking, so the PC does not know by default the current positions. You can set enable_logging and enable_logging_pose to true in the launch file, which will create topics like cf<id>/pose containing the current state information. In your script, you can then use position() or subscribe to the topic manually if you need velocities as well.

[coenwerem]

Thank you so much for the prompt response! I have those two parameters set to True in the hover_swarm launch file. I did not know about the cf/pose topic. I will try that out.

Thank you.