I am flying APM 2.5 with firmware ArduCopter v3.1.5. When I engage AltHold or Loiter mode, copter starts climbing up fast. As I have observed until now, the altitude displayed in mission planner correctly when the motors are not spinning. After take-off, the altitude takes negative values and decreases further with increased throttle. When I plot the barometer altitude, the data seems reasonable however, GPS’s RelAlt data matches with the displayed altitude data. I have tried the quad with APM 2.0 (both firmwares 3.1.5 and 3.1.2) also, but still got the same results. I am sharing my log file for APM 2.0 v 3.1.2.(Vibration data is also available)
Any help would be appreciated.
Did not see barometer data in logs. Turn up your logging for these test so we can see all the PCIN/PCOUT data as well as the barometer data.
The log show you were in Alt Hold only a short time. See some Vibration Spikes but that does not look like the issue.
AltHod was engaged for a shor time because quad climbs fast in AltHold. Barometer altitude is available in the uploaded log file under CTUN with the name BarAlt. I am sharing the plot of BarAlt, WPAlt and GPS RelAlt together. The log shows GPS ERROR but this was the only the time I got GPS ERROR, the problem is present at all times. The problem is GPS RelAlt goes negative and WPAlt is set accordingly. I suspect vibrations were the problem but does it have anything to do with GPS RelAlt?
Note: Red for BarAlt, Green for WPAlt and Blue for RelAlt