Autotune reduce unnecessarily responsive

ArduCopter Copter 4.6
1

Hi all,

Happy New Year.

I have a 13 in quadcopter running 8S 3300 mah 4312 506 kV matek h743. I have finished autotune, but I would like to reduce the stress on the airframe even with autotune aggressive = 0.5.
From the autotune page, I see this: AutoTune will attempt to tune each axis as tight as the aircraft can tolerate. In some aircraft, this can be unnecessarily responsive. A guide for most aircraft:

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After autotune, here are the parameters after autotune. I set mot_SLEW_UP_TIme = 0.05 and MOT_SLEW_DOWN_TIme = 0.05.

For this ATC_ANG_PIT_P should be reduced from 10 to 6, is that from 100% to 60% or change the number to 6?

Thanks,

param_Apex_Evo_13_in_autotune_2026_jan.param (23.3 KB)

2

You could change the Pitch and Roll values (21-22) to 60% of that but I would leave Yaw where it is. A log file of a post auto tune flight would be useful and I’m guessing that the vertical acceleration controller gains are not right. Unless you really do have a hover thrust of 0.125 which is the lowest value it will learn.

You mean 0.05 but I have not seen many Auto Tunes that were optimum with a value that low. It typically produces Rate PID’s too low producing a slug for attitude control.

1 Like
3

Thanks,

I have flown this before, and I have a hover thrust of 0.125 . I was afraid of flying autotune parameters without changing becaue after autotune, I had a crash a 13 in already (that frame was a cheap $45 frame from Aliexpress) due to autotune and I was flying in Loiter full speed ahead and then release the stick, the airframe dis-integrated; but initial flight with default parameter was fine (before autotune). Then I had another crash of another 15 in quadcopter due to switching from Loiter to Acro at mid-throttle, and frame was not able to tolerate the abrupt throttle change, so I increased mot_SLEW_UP_TIme = 0.05 and MOT_SLEW_DOWN_TIme = 0.05.

4

Is that from the log looking at CTUN>Tho at hover or using the MOT_THST_HOVER parameters value? Not to belabor the point but many get this wrong.

Can’t say I have ever seen anything like that before from all manner of frames.

5

I just hover at Alhold, and it changes the default ( I think around 0.25 to 0.125) for MOT_THST_HOVER. I didn’t check the log.

6

Then it’s likely wrong. As I said it will not learn a value below 0.125 so you have to review the log for the correct value. It could be 0.125 but that’s awfully coincidental wouldn’t you say?

But whatever. Post a link to the log or don’t

7

here are two logs:

8

Hover thrust is ~0.14 so I would revise the vertical acceleration controller gains based on that. But actually 0.125 on this craft is close enough. Then personally I would set Auto Tune aggressiveness back to default (0.075) and run Auto Tune again. The Rate tune needs some improvement. You will want to set the MOT_SLEW parameters back to default before doing so.

The vibe levels are high but I assume that by getting to this stage you have already done what you can to address it.

9

Also I would update to the latest firmware…4.6.3

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