General Pid Questions

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General Pid Questions

Postby pilotnbr1 » Fri Mar 04, 2016 5:15 pm

So I am flying pids on my 280 frame. I recently switched from 2 blade to 3 blade props and also experimenting with much larger batteries in an effort to get more flight time.

The switch to 3 blade props required me to completely rework my pid settings. What are some general adjustments to make going from 2 blade to 3 blade props?

If I tune the quad with very little payload will it fly (be stable, I know it will be sluggish) just as well with a heavy payload?

I noticed that with small battery packs it twitchy but flies fine with much larger battery packs.. Just wondering if I can optimize for small batteries and throw a big one on later and not have any adverse reaction.

Thanks guys!!
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Re: General Pid Questions

Postby Max » Fri Mar 04, 2016 7:33 pm

No, in general it will not be the same tuning between a lightly loaded MR and a fully loaded one. They're like different machines. The main point of tuning is pretty much to match the settings to the specific machine. How different the tuning would need to be could depend on a lot of factors though. Besides the basic weight/inertia differences, the vibration frequency can also easily change when a load is added/removed, depending on what/where/etc. Wind resistance can change. And so on...

But seeing as the overall power-to-weight ratio does dictate a lot of the tuning, one thing which may help, if you can do it, is to reduce the prop size when the MR is empty. Going down a prop size (or two) may put your hover throttle point back to around 50% (or wherever you'll have it for the fully-loaded version, hopefully 50% or less). Then when you add weight, increase the prop size again, keeping the hover point roughly the same.

From my experience this does make re-tuning for the additional weight much simpler (or in some cases not necessary), though it's no guarantee by any means (all those other factors come into play, esp. vibration changes).

Do you mind if I move this to PID Tuning forum?

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Re: General Pid Questions

Postby pilotnbr1 » Fri Mar 04, 2016 9:41 pm

Thanks Max!

Sorry I posted in the wrong spot! Feel free to move me!

Good info Max- thanks for the reply!

I have it pretty dialed in with the 3 blade and running anywhere from a 2200 mah 3s to a light 5200 mah 3s all with less than 50% throttle. For me e-calc did not get very close to what I predicted. I think my hd-fpv wifibroadcast system is pulling more amps than I thought. I also am landing at about 11volts as shown on Android QGC. After landing and no load its coming up to about 11.4v on my batteries so maybe I am being too conservative...
2200mah 40c- 5 min flight
4000mah 30c- 7 min flight
5200mah 20c- 11 min flight - its a lighter than the 4000mah

I need to dial out some of the wobbles as much as possible in a descent. It seems to try to over correct and be dynamically unstable overcorrecting each wobble in a descent until I arrest it.

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