High Z-oscillations when using multiple crazyradios

[ryanwallis]

Hi all,

I have been attempting to fly 3 crazyflies with 2 crazyradio PAs, motion capture system and Whoenig's ROS package. However, after a few seconds, the crazyflies begin to oscillate in the Z-axis, to at least 40cm about their desired position.

The crazyradios are separate to each other by a meter, using USB2 cables and there is no obvious other source of a 2.4GHz signal.
The stream from the motion capture system appears to be adequately quick.
The motion capture tracking reflects observed behavior.
Flying crazyflies (1 or 2) on one radio does not induce such oscillations and the flight is stable.
I am using crazyradio firmware 0.53 and crazyflie firmware 2016.09

I have tried a few different things but this behavior suggests a fundamental issue, does anyone have any suggestions for what I could look at?

Thank you very much.

[arnaud]

This is peculiar behavior. Are the two radio operating on far-enough radio channel and have you tried different datarate? For instance we have observered that 1M and 2M are less subject to interference.

[ryanwallis]

I ran 2 crazyflies on channel 20, at 1M and 1 crazyflie on channel 50 at 2M. The behavior is still present but there was an improvement.

Additionally, the crazyflies are each carrying a 12-15g frame to hold motion tracking markers. Even though this fits under the weight limit, do you suppose this could be a factor? What is the suggested turnover rate for motors and batteries for the crazyflies?

[arnaud]

The weight could be a factor but it cannot explain a correlation between the number of Crazyradio used and the quality of the flight.

Are you running the Crazyradios using a powered HUB? Could you maybe try to run 2 Crazyflie from 2 crazyradio and then 2 Crazyflie from 1 Crazyradio to see if there is any correlation between the fact that you use multiple Crazyradio and the flight instability.

[whoenig]

Make sure you assign unique addresses as well, even if you use spaced out channels. For high flight performance I recommend using the Crazyswarm framework instead (see http://crazyswarm.readthedocs.io/en/latest/). This comes with a much better controller, python scripting layer, and you won't need to put heavy frames on the Crazyflies. Also, you can operate 15 CFs with a single radio.

Best,
Wolfgang