Alzrc devil 420 with CUAV V5 nano

Hi all,

Looking for some help with my devil 420,after successful first hover i’m ready to proceed with tuning but i would like to someone with experience to take a look at the log and parameters to see if there is anything that i should change before proceeding to next step.[]
Thank you for the help


I think your set up looks pretty good. I can’t tell if you have vibration issues as the log sample rate is not fast enough. The VIBE signals look good but those are based on accels and not gyro data. Its not a bad idea just to set up the harmonic notch according to the wiki for helicopters.

Everything else looks good for a starting point. What are the actual blade collective pitch values for H_COL_MID and H_COL_MIN.

I would suggest that you upgrade to 4.2.0 since it was just released as stable and has an autotune feature now. Be sure to set new parameters for the collective set up and read the wiki on the autotune feature.

Hi Bill,

Today im finishing installing hall sensor for rpm measurement and after that i will setup the dynamic notch filter.
As for H_COL_MID and MIN they are 0 and -3 degree of pitch

After updating to latest version and enabling dynamic notch filter i made another test.
This time i proceeded with manual tuning per wiki,started with D gain which resulted value of 0.000031,any higher than that i get oscillations.
log attached

Did you try tuning the FF gain for pitch and roll? For the rate D and rate P gains, the autotune can do a much better job in most cases and require maybe 3-5 min per axis. The FF gain can’t be overpowering. I know the FF test in autotune has not been doing as well with the smaller heli’s (< 500 size). But follow the wiki and try it. I have described in the log analysis section video how to see if the FF is not being determined properly. Once you are happy with the FF gain then run the rate D and rate P gain autotuning. What you determined manually seems very low.

Unfortunately I do not have the ability to open logs and conduct analysis at this time. Hopefully the advice above helps.

Thank you for your help Bill,really appreciated

Today i tuned FF gain and i think it DesRoll,roll and DesPitch,Pitch are ok, before i continue with autotune of D and P gain is there anything in log that i should change,my concern is that heli is not hovering at mid stick,more like 40% of the stick travel

@ivank Ivan, I am on holiday for the next 10 days and won’t be able to review logs. I can look at changes in your parameter list and give you advice. Regarding the hovering collective, what is your rotor speed? Now that you upgraded to 4.2.0, what is H_COL_ANG_MIN, H_COL_ANG_MAX, H_COL_ZERO_THRST, and H_COL_LAND_MIN. Hover Collective not at 50% is not that big a concern but it will cause the transition between stabilize and althold or loiter to be less smooth. You could adjust the IM_COL_STB_2 and IM_COL_STB_3 to encompass the hover collective point. It will make the collective in stabilize mode nonlinear in that it will feel more sensitive in one area (above/below hover) and less in the other. Make IM_COL_STB_2 =35 and IM_COL_STB_3 =55. You can read the section of the wiki on this if you need more info.

Head speed is 2600rpm
H_COL_ANG_MIN, -3.5deg
H_COL_ANG_MAX 11 deg
Currently i have IM_STB_COL_2, 40 and IM_STB_COL_3, 55

@ivank Ivan, based on your estimate of 40% collective for hover, that means you are hovering at about 2.5 deg collective. That is pretty low and makes me wonder why you need your max collective at 11 deg. I guess if you want to fly extremely fast or do acrobatics, then I guess that would be warranted. So you can do one of two things: lower the max collective so the hover collective is closer to 50% OR change the IM_COL_STB_2 and IM_COL_STB_3 to help center the collective stick on your hover collective.

One thing to be cautious of is the H_COL_LAND_MIN value being too high. You may want to lower it another degree if your aircraft can withstand rotors turning on the ground with the collective that low. This is very important when the autopilot is flying as it uses this value to determine when the aircraft is landed. So you want to be sure that when it hovers in the wind that the collective does not go below that H_COL_LAND_MIN value.

I don’t intend to do acrobatics or fly at some crazy speed just normal sport flying.
When i was doing testing it was pretty windy day here in Dublin so that maybe affected collective required for hover?
Next test will be with lower max collective
Anyway i will do what you recommended for H_COL_LAND_MIN and set it at -1 degree
Thanks for your help

1 Like

@ivank just realized that you misunderstood my suggestion. i meant for you to set it a degree lower than where it is now. So I am suggesting to set it at -3 deg.

After successfully finished autotuning FF gain yesterday,today i tried tune pitch and roll gains.
Everything went fine with pitch axis as shown in log, but on the second flight with fresh battery i was doing autotune on the roll axis,autotune lasted entire flight 8+ min and ended up with autotune fail message.
Logs attached.

Hi Ivan @ivank ,
It appears from the log for the roll axis tuning that the maximum frequency was not high enough to capture data for the max gain determination. I would suggest increasing the AUTOTUNE_FRQ_MAX to 100 and try tuning the roll axis again.

Bill,thanks for your help,really appreciate that.
I will try with FRQ_MAX 100 but first i need to sort out mechanical problem on the heli,found out that heli has way to much slope in the rotor head.
Looks like rotor hub is machined slightly oversize and dampers and o-rings are loose in the hub,tried with genuine SAB parts(dampers,o-rings and feathering shaft) with same results.
Would that kind of problem affect autotune?

@ivank I think that as long as the control linkages don’t have slop in them then it should be good. The movement of the blade grip on the spindle should be ok. I seemed to have some of that on my synergy heli but never saw any issues with the tuning of it.

Found slightly bigger and harder o-rings and now head feels perfect.

1 Like

After setting FRQ_MAX 100 tried tunnel roll axis again,it failed two times,on the third flight it completed auto tune successfully but ended up with extremely low D gain,not sure what is the problem,vibrations,noise in the control signal?.
I’ve tried Angle P tune as well,tune ended up only with Ang_Rll_P of 9.5

@ivank Yes the roll tuning went pretty well now that it was able to go high enough in frequency to determine the maximum allowable gains. If found the following
Max allowable Rate P gain = 0.093
Max allowable Rate D gain = 0.00063
It starts tuning by raising the Rate D gain and watches the response gain. Once it stops decreasing then it moves to the Rate P tuning. So as soon as it started increasing rate D the response gain increased so it stopped increasing Rate D and left it zero. Rate P got to almost 50% the max gain value.
Looking at your second flight. it looks like you did angle P for both pitch and roll axes. The autotune didn’t do a great job on finding the frequency with the maximum frequency. So I think you should take the Roll angle P gain back to 4.5. How does it feel with the autotune determined roll rate P and rate D settings and roll angle P at 4.5. if it behaves well then leave it.

For the angle P tuning in pitch, the autotune again found the wrong frequency. You can look at the data and see that the peak is near 30 rad/s rather than 60 where there was a spike which is not real. So I would suggest lowering the max frequency for the angle P for pitch and run it again. I’m assuming that you have tuned the pitch rate P and rate D already. it looked like there were non zero values for those gains.


Really happy with heli and how it behaves,but need to do bit more testing.
What frequency do you suggest to set for angle P,and should i leave roll angle P 4.5 and tune just pitch angle P?
Yes, rate P and rate D are alredy tuned

@ivank Glad to hear that you are happy with how it behaves.

Since you think roll behaves well with Angle P at 4.5, I would only tune the pitch angle P. As for the maximum frequency, I would set that to 40 so that it doesn’t make it to where the data got spikey. Remember to set the pitch angle P value back to 4.5 before starting the Angle P autotune test.

Let me know how it goes.