Oscillations after lowering throttle.. Imax?

I’ve been trying to get rid of some occasional oscillations I get at mid-throttle. Usually after I take off then slow down to cruise, or after I’ve been flying fast and then slow down. They’re about 2-3hz, and only last a few seconds, or until I change the throttle. I’ve been through a huge range of PID’s, and experienced everything from sluggish to starting to oscillate, and through the entire range, it still does this 2-3hz osc at times.

Could IMAX be causing this? Building up too much Iterm after a high speed run? That’s the last thing I tried and it seems to have helped, but the issue doesn’t occur every flight, so I’m not sure… And I’m out of time for flying for a few days, and won’t be able to do any more test flights for a while… I’m just curious if IMAX could cause issues like this.


Is this on one of your small copters?

And I’m pretty experienced w/ tuning and all, but can’t figure out how to get rid of these occasional oscillations. This is just a subtle occasional thing. I obviously don’t have a gimbal on these tiny copters… and if I did have a gimbal, I bet I wouldn’t even know this is happening. I don’t always notice it in my goggles. But when reviewing the HD video later, I see the little wiggles.

Little more info about why I’m looking at IMAX now…

I know what I term does technically, but in practice, haven’t ‘felt’ or seen a lot of difference in a huge range of settings for I. But I came across several posts from people saying too much I term leads to a slow oscillation. So I could see maybe I term building up for some reason during high speed runs, and when I lower the throttle I is built up and kept high when it isn’t needed anymore, so causes the I term oscillations for a few seconds. Just a guess. I did have time for a flight today and it still did this… But I had to force it… I ran a long full throttle run, and when I stopped, it oscillated. But otherwise, with regular flying I couldn’t reproduce it w/ the lower IMAX. This is just one of those issues where it might be fine for weeks, then all of a sudden it happens for several flights. So at this point I still don’t know if I’ve made any difference.

One more thing I’m not clear on and would really really help me, is when people discuss tuning they often talk about fast oscillations (as in too much D term) and slow oscillations (as in too little P, or too much I term).
But what is fast and slow? I am considering these 2-3 hz osc’s as slow… Because I have seen too much D term cause oscillations so fast I can hear it buzzing. But what do other people consider fast vs slow oscillations?

Did you ever figure this out?

My 2 cents on ‘fast’ and ‘slow’ oscillation. I consider oscillations that you can hear as buzzing/whirring to be ‘fast’ oscillations. Those tend to be in the 100Hz or higher.

The slow oscillations are ones you can’t hear but you see in the goggles, like bounce-back from doing a hard pitch/roll.