I took Chloe out onto the drive – horizontal drift didn’t exist – a perfect vertical rise and fall. There were only two flights; the first rose to 50cm but then descended slowly during the hover phase, landing gently even before descent phase of the flight plan has started. The second flight also didn’t drift laterally, but in contrast, it rose to 2 meters during ascent phase, and continued to climb during the hover phase; at that point, I killed the flight.
There’s a few possible causes I can think of off the top of my head:
- the Butterworth filter needs turning as its filtering out of gravity is lagging behind sensor drift – this is my prime suspect
- the complementary filter needs tuning as its merging of angle sources is lagging behind sensor drift – this is much less likely however, if only because it would affect lateral drift also
- IMU temperature drift between the first flight and the second – again I’m doubtful as although it could affect hover height, there shouldn’t be vertical drift during hover phase – this is what’s pointing to the Butterworth lagging too.