[from Github] Issue with flying Multi CF's precisely for a given position using UWB loco positioning system

[arnaud]

Copied from a github issue https://github.com/whoenig/crazyflie_ros/issues/75 to move the discussion here.

I was using the latest firmware for flying multi CF's using UWB loco positioning system.
I am using this command
roslaunch bitcraze_lps_estimator dwm_loc_ekf_multi_hover.launch uri0:=radio://0/30/250K/E7E7E7E701 uri1:=radio://0/30/250K/E7E7E7E702 for flying 2 CF's.
and using
roslaunch bitcraze_lps_estimator dwm_loc_ekf_swarm_hover.launch uri0:=radio://0/30/250K/E7E7E7E701 uri1:=radio://0/30/250K/E7E7E7E702 uri2:=radio://0/30/250K.
for flying 3 CF's.

both has the same issue behaving crazy and hitting the walls (Not taking off accurate to the position given to the UWB loco positioning system. )

Any suggestions would be helpful.

Thanks in advance,

Appala Chekuri.

[arnaud]

In what ranging mode are you running the Crazyflies? If you are running the default TWR mode, you cannot fly more than one Crazyflie. You need to run either TWR-TDMA or TDoA mode in order to be able to fly multiple Crazyflie: https://wiki.bitcraze.io/doc:lps:index# ... ctionality.

Another thing that could cause bad take-off is that all the Crazyflie should be started facing X. This is required because the Kalman filter needs do have a good initial orientation.