I'm operating a stock standard Arducopter 2 from jdrones with GPS, Magnetometer, MB1200 Sonar and a Turnigy 9x radio
Over the past couple of months I have seen the occasional odd behaviour with the Sonar when bench testing with the CLI Sonar test. Basically the Sonar sometimes fails to report the correct distance - sometimes it locks in a fixed and incorrect distance, sometimes it sticks at the minimum 34cm. At other times it appears rock steady and quite accurate.
Yesterday while out on a perfect flying day (a rare event in the middle of winter here in the land downunder) I struggled to get altitude hold to work when testing 2.0.35. I saw the pulsing or gunning behaviour others have seen in the latest Alt_Hold followed by either a steady climb or a gentle descent that brought the aircraft down to lawn mower level.
Looking at the logs in Mission Planner I notice that the sonar data is very spikey.
In the images below note the red trace is Sonar Alt, Blue is Baro Alt, Green is Throttle
The correlation between the sonar peaks and baro altitude is good at low altitudes which reassures me the Sonar is functioning correctly - some of the time
and the same again zoomed in near the start of the data.
Can anyone help explain what I am seeing with this 'noisy' sonar data.
Do I have a hardware problem?
Where might it be?