Bitcraze Forums

Hi,

My build is a quadcopter with crazyflie bolt, and currently having this problem position mode.
Whenever i flew the drone above 1.5m manually or using script, the drone will start to have "bouncing" motion but it holds altitude well when flying low.
The beacons were set up in a 4x3x3m square.

Is there any parameter that i can change to improve the z axis performance to allow the drone fly stable at a higher altitude.

Thanks in advance

Hi!

Which type of positioning system/mode are you using?

i am using UWB with flowdeck and 8 loco positioning beacons in twr mode

Sounds like the noise from the VL53L1 laser ranger sensor is going up and that it is causing instability. The height measurement is handled in zranger2.c. You could try to increase values in the STD model here as a first step. You could also try to switch VL53L1 mode to VL53L1_DISTANCEMODE_LONG

Thanks Tobias, it works better now after increasing the value.

May i know what is the difference between expPointA and expPointB?

The ExpPoint values are creating an exponential STD function based on the distance. The longer from the ground the less the kalman filter will trust the data. The function looks like this:

i tuned the values and it's working fine in TWR mode, able to fly stable at 5m, however when i switched mode to TDoA3 the same problem happen again, may i know why?

And is the possible for crazyflie fly above or outside the area enclosed by the beacon in TDoA3 mode?

Thank you!

Good question. I think it is because the TDoA is a bit more noisy and depending on the anchor positions often Z is the most noisy. Is it different then if you would only use the Loco positioning, no flow or z-range?

In TDoA the position estimation will quickly become worse outside the enclosed area. I recommend to read up a little about TDoA to get a better understanding.