Drone shoot up but log indicate potential thrust loss(3)

Hi everyone

I am using kakute H7 mini with tekko 50A ESC and a 3800KV motor. my quad is using pavo25 frame.
When i increase throttle in althold mode, the drone shoot up and the log indicated potential thrust loss.

my drone weight is around250g

Potential thrust loss is a message that arises when a copter commands certain propellers to rotate faster, but does not observe the corresponding change in either altitude or attitude. My impression that the second is most likely - e.g. the copter sees it is pitching backwards, so it spools up the rear props to compensate, but still keeps pitching backwards - for the reasons that follow.

Based on how badly it oscillated during first seconds of the flight, even before skyrocketing, I think the copter is really poorly tuned (too aggressively most likely). Please follow the initial tuning instructions, which include decreasing PIDs when you observe oscillations.

I would also say that values like ATC_RATE_{R,P,Y}_MAX, which are 90 degrees/sec, are too low for such an agile aircraft. I would keep them at 0 (no limits) and make the pilot feeling smoother using other means.

For initial flights, I would also say that ATC_INPUT_TC is set way too high, so that you are unlikely to react timely if the copter misbehaves. Keeping to the default 0.15, or even decreasing it to 0.1, seems a more sane choice for me. Once you tune the copter nicely, you are free to increase it back if you wish.

And it may be better to temporarily disable optical flow before you settle down with the low-level control. Optical flow will not help if the copter cannot keep itself at a given attitude.

Hi MaxBuzz,

I had follow the initial tuning instructions, and had some problem on tuning. My drone unable hover in stabilize mode and i see it fly up and down and when i switch to althold it will shoot up. Should i decrease the PID value? or should I enable harmonic notch filter?

Harmonic filter is a nice thing to have (you seem to have ESCs that support bidirectional DShot, that is good), but it will not magically solve the tuning problems.

PIDs now seem too small. Based on the logs, I would start testing with rate P&I on pitch and roll equal to 0.05, and then I would attempt to increase them by 0.01 until the quad can keep its attitude within sane limits. This will not be the final tuning, but something you may start from.

The runaway issue in AltHold may result from your barometer being affected by direct propwash. I see that you also have a rangefinder, and what it reports disagrees with the barometer by a lot. You need to cover the barometer with a piece of open foam, and ideally cover that from the top. What I typically do - provided that the barometer is on the top plane of the flight controller board - is that I assemble the quad in such a way that the VTX board is atop the flight controller, in this case I put some foam from the packaging between the boards.

In Stabilize, you do need to control the altitude by yourself - fortunately, this is not too hard with some experience, and the better the tuning, the easier. In AltHold, especially in small quads, you may see some height deviations too (unless you set up the quad to trust your rangefinder more, and unless the rangefinder itself is trustworthy).

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I am using the kakute stack from holybro (Kakute H7 Mini Stacks – Holybro Store) i had put foam in between the FC so is insulated. From the log, i guess the Vibe is in acceptable range.
So for now i seeing 2 issues:

I had increase my rate P&I on pitch and roll and do see its getting better. should i continue increase it? cause i dint see any significant improve and my drone will lean to left or right sometimes in stabilize mode and not really hover. Is it normal?

After enabled the harmonic filter, can help advice is my setting correct on it? cause it cause a crash when i set the freq to 300 and bandwidth 150.

I did also try althold or loiter but it still shoot up so i need to tie the drone for safety purpose.

Really appreciate your help!!!

Your rangefinder altitude is wrong, showing about 1.2 meters when the barometer is showing about 12 meters. The copter is trying to oscillate between the two altitudes.

or maybe ARMING_CHECK,388598 if you want to try and work without a GPS.

I suggest you disable the rangefinder and do a flight in AltHold and see how that goes.
The other rangefinder parameters will remain in place, they’ll just be hidden until you enable it again.
Definitely use the parameters below too - they will certainly help with flight and data gathering.
Later when all tuning is completed, then enable your rangefinder and see how it performs after being calibrated correctly. The reason to do everything in that order is then you know if tuning or the rangefinder are introducing issues, which will simplify what you do about it.

Set these to fix up your harmonic notch filter and get back to some normal logging:


I had disable the rangefinder and it dint shoot up. I tried using althold to hover seems like it too agile and hard to control on it. Any advice?

tune6.param (21.0 KB)

The copter is very overpowered, so you’ll have to either add weight, or set:


and manually adjust that hover value until it’s correct for most situations.

The copter is also oscillating wildly, start with adjusting these:


Hey Shawn,

After follow your instructions, my drone is undercontrol and more sane. It just lean backward and i guess need fine tune the pitch PID. I also try make some changes in harmonic notch frequency to 117 based on fft gyro result. let me know if i have it wrong.

One more thing is why my drone will out control once it get into althold, it will have full throttle going up but i already set my throttle to zero in transmitter

Really appreciate your advice

Definitely set ARMING_CHECK,388598

Set this, just to make sure the harmonic notch filter can go low enough if it needs to - it can scale up but not down below whatever value you set here (like 117Hz)

Connect the copter to MissionPlanner, go into Setup / Mandatory / Accel
Now perfectly level the copter (across the plane of the props if possible) - dont assume the ground it is sitting on is level - get a spirit level or something to check.
The press “Calibrate Level”

The full throttle thing in AltHold is because I suspect you’ve got a script doing something whenever you are in some position or altitude controlled mode:
Lua: @ROMFS/scripts/TeamoneTakeOff.lua:280: attemp
So disable scripting
and continue the normal tuning process.

Only go to the advanced features once the copter is working well with normal RC control.