Optical-Flow oscillations at higher altitudes

ArduCopter Copter 4.3
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1

Hi, im trying to use an HereFlow sensor with an LW20/B lidar (good up to 50m) using Copter-4.3.2…

I followed the the wiki at: https://ardupilot.org/copter/docs/common-optical-flow-sensor-setup.html#common-optical-flow-sensor-setup and setup the EK3_SRCx Parameters so that i can switch between GPS and OpFlow using a switch. I can confirm the EKF3 is switching correctly between GPS and OpFlow (I followed all the steps in the wiki including in flight calibrations and setting the FLOW_POS parametrs)

The OpFlow performance is ok at low altitude (below 20m the copter is very steady), above this altitude the copter starts oscillating about the pitch and roll axis’s. the flight where held outdoors it a well lit and textured environment

the flight log and a short video of the oscillation can be found here:
https://drive.google.com/drive/folders/15pOcFXy2iemsAVWAki8n1x3YUzjj7Xzy?usp=sharing

is OpFlow not suited for higher altitudes i.e. 20m-500m? (assuming i’m in the lidar effective range)

i’d appreciate your help🙏 Thanks!

2

You are correct that flow sensors in general are ineffective at higher altitudes. I have a lot of experience with the hereflow and found it didn’t do much over 20m. The flow info changes very little and much more slowly above that altitude.