Altitude Hold Troubleshooting

So I am flying my vario helicopter in stabilize mode great.  I am venturing into AltHold and am seeing some strange behavior. 

I noticed that my BarAlt and Alt were not matching up.  So I reduced the INAV_TC_Z value which helped a lot. 

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So then today I am flying and I flip to AltHold and it actually is working ok... So I flip back to Stab, move the heli around a bit then flip back to Alt Hold and it immediately gives full negative and goes for the dirt!  Here you can see the Alt/BarAlt and throttle out graphs... 

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What am I missing?  Why is this happening? 

Also, here is my vibration graph... 

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Any advise is much appreciated! 

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Replies

  • have you tried changing the mix between baro and gps 3d fix?

  • The new vibration plate is working well.  After going back and forth between the PIDs and INAV_TC_Z values a bit, I found its sweet spot.  I was able to do a few successful AltHold flights and it is very smooth, even down to a landing. 

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    https://storage.ning.com/topology/rest/1.0/file/get/3702024509?profile=original
  • I fabricated an anti-vibration mount that is now closer to the rotor mast (CG).  This dropped my Z axis vibrations quite a bit which enabled me to do 4 successful AltHold flights.  The heli is still bobbing up and down a bit, I assume PID tuning will fix this?  

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  • Chris it seems that something happened during stabilize, look at the increased range (just before switching Alt-Hold the second time). Did you see anything wrong from outside? engine bolts all properly tightened ? Tail boom braces ? It looks like something came loose suddenly, thus generating all those vibrations (as an example on an Xcell converted to gasser I experienced one broken bolt in the clutch/engine support structure, showing a sudden increase in vibrations) .  

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