Just came across this:
github.com/cleanflight/cleanflight/issues/691
Any chances of getting this into Quadrino? Im prob giving up my on custom Vtail build (cant get it to stop drifting, even on takeoff) but still like the idea of something a bit different.
Can you describe the “Drift” problem in details ?
Usually when we talk about “Drift” on a multirotor it’s a very suble move that occur when not giving any RC commands at Hover.
TBH Im unsure of the problem, it maybe mechanical (as in the motors) or the complete lack of tuning or the general shape of my Vtail. I have never got it flying enough to determine the problem or tune, all my tests end in disaster. Which is ok as I just rebuild with improvements but Im starting to think there is a reason there are no Vtails with 15" props.
2 tests ago it was rolling to the front **right **on take off so significantly I didnt dare take off. I since moved the batteries into the COG and tried again…
Last test it was now rolling to the front **left **when trying to take off (approx 50% throttle). I turned off all RC modes as per the PID tuning document and pushed the throttle upto 90% to get it to lift off which it did, but it rolled to the left just as on the ground and drifted rapidly towards houses (I found a field to test in but evidently not a large enough one). I throttled off but it came down hard at that same angle and got pretty smashed up.
I will remake it fixing structural weaknesses but seems like Im building to just destroy it again.
I’m using 15 CF props on Avroto AVL3515 motors. I’ve long suspected one of the motors is “looser” than the others in some manner, I’ve tried tightening/loosening the screw on the shaft to accommodate but perhaps still not right.
I also cant figure out (nor can anyone I asked) how to do the PID tuning without getting chopped to bits by the 4 x 15" props spinning on an untuned and unstable quad. It seems stupidly dangerous at this scale vs something with little props which the tuning is clearly written for.
When flying in “Horizon” mode the flight controller should try to keep the frame Level even if that mean asking more from a motor that do not turn like the others.
The frame will always have to be flown when talking VTail unless it’s perfectly tuned.
Did you experience any oscillations ?
The best advise i could give you at this point is making a simple Quad frame with wood and test all the electronic in that configuration… 
Thanks, all makes sense. Ill rig up a basic quad shape and test that out. On oscillations, a little, is there a video of whats acceptable on the Nano?
Could you clarify these two things for me though:
[font=Helvetica Neue, Helvetica, Arial, sans-serif][size=2][highlight=#fbfbfb]- "The frame will always have to be flown when talking VTail unless it’s perfectly tuned. "[/highlight][/size][/font]
What do you mean by talking Vtail? Do you mean it always has to be in Horizon mode?
[highlight=#ffffff]There are no “Acceptable” oscillation, this is produced by a bad PID setting. The controller overshoot a corrective and it oscillates.[/highlight][highlight=#ffffff]We mean you always have to “Fly” and “Control” the frame and pitching in a direction might happen at takeoff and you still have to get it back to its position with your controls.[/highlight][highlight=#ffffff]It’s not flying by itself, even more if the PID’s are not optimal. Horizon mode will help keep the frame Level.
All PID’s can be tunes in WinGUI.[/highlight]
[size=1]"[font=Helvetica Neue, Helvetica, Arial, sans-serif][highlight=#ffffff]There are no “Acceptable” oscillation, this is produced by a bad PID setting. "[/highlight][/font]
[highlight=#ffffff][font=Helvetica Neue, Helvetica, Arial, sans-serif]Even when testing it with no props on, which is part 1 of the PID tuning guide? It says if there is a lot of oscillation there then its vibration issues, not PID problems? I see minor ripples there…[/font][/highlight]
[highlight=#ffffff][font=Helvetica Neue, Helvetica, Arial, sans-serif][/font][/highlight]
[font=Helvetica Neue, Helvetica, Arial, sans-serif][highlight=#ffffff]From the PID tuning guide:[/highlight][/font]
[font=sans-serif][highlight=#ffffff]
]Set motors running at approx 50% if you have props on be very careful, check GUI trace for an almost flat line from gyro and acc[list=1]
]if trace is dancing all over the place you have vibrations issues and it needs to be sorted before proceeding."/:m]/:m][/list:o][/highlight][/font]
[font=sans-serif][/font]
[font=sans-serif]“Dancing all over the place” is significant oscillation… which is to say there is some acceptable levels below that… right?[/font][/size]
The first thing to avoid is still Frame / Motor / Propeller vibration as the flight controller can react to those vibrations by giving unwanted commands. (reactions)
If your propellers are well balanced and there are no big vibrations, you should be fine.
There is a “Filter” in the FCT application which can be set to eliminate some of the vibration induced. (FCT / Options / Filters / Gyro Filter)
