Unsucesfull autotune of haxacopter 18" propellers

ArduCopter Copter 4.0
1

Hi I am trying to autotune my new hexacopter based on U7-420 motors with 18" propellers. It’s classic flat hexa based on 2x6s batteries and Cube Black. I did manual tuning:
with this parameters and that’s flight log flying with this manual parameters. Generally the copter is too sluggish with this parameters. I think it can fly much more responsive.

I tried autotune with 0,08 aggressive but after this the copter was totally not flyable it was so sluggish that I didn’t have control over hexacopter. It was reacting for sticks veeeeery sloooow. This are parameters after autotune.That’s a flight log from autotuning.

My manual parameters which are not perfect are:
image

  • Cube black is mounted on rubber screws (vibration isolation) which I tested with other octocopter builds and autotune worked on this rubber isolation.

  • Vibration on all axes are under 40

  • MOT_THS_EXPO is 0,7

  • Frame is quite stiff carbon and aluminium

  • I am using T-Motors 80A Flame escs which were autotuned in my other multirotor builds

  • Copter is not overloaded

  • I calculated some of my parameters in this spreadsheet which I found on this forum :slight_smile:

What should be my next step to do successful autotune ?

2

Vibrations must be bellow 30

3

I don’t think that’s possible with bigger copters. I have higher vibrations only on Z axis.

4

You better make it possible!

And you might want to take a look at: https://github.com/ArduPilot/ardupilot/pull/16471

5

Mee too , today I want to work with 18" quad so I go to auto tune but every time show nothing change in flight performance , why this happening ???
This is after 1st time autotune

This is 2nd time autotune

This is 3rd time autotune

This is a link of Bin file https://www.dropbox.com/sh/dz2giadcbdj1vlb/AABtS3ywctaUlw_ZL3hGz_bGa?dl=0

Help me out

Thank you :slightly_smiling_face:

6

For the T-Motor Flame ESCs set these:
MOT_THST_EXPO,0.2
MOT_PWM_MIN,1100
MOT_PWM_MAX,1940

I checked the manual tuning flight log, there’s definitely too much Z axis vibrations. If you can get the Z vibrations down and set these values, then I think Autotune would work a lot better:
ATC_RAT_PIT_FLTD,13.00
ATC_RAT_PIT_FLTT,13.00
ATC_RAT_RLL_FLTD,13.00
ATC_RAT_RLL_FLTT,13.00
ATC_RAT_YAW_FLTT,13.00
INS_ACCEL_FILTER,20.00
INS_GYRO_FILTER,26.00

MOT_SPIN_MIN,0.15 is very close to MOT_THST_HOVER (0.16 - 0.18) so lower MOT_SPIN_MIN,0.15 a bit so thrust is just starting to be produced. Also the hover value is not learning properly because you’ve got massive amounts of RC stick input and the hex is constantly pitching and rolling up to 30 or 40 degrees.

For improved stick response, lower ATC_INPUT_TC - you have 0.22, try 0.2 or 0.18. 0.15 is the default.

Also for you manual tuning try these as a starting point:
ATC_ACCEL_R_MAX,60000
ATC_ACCEL_P_MAX,60000
ATC_ACCEL_Y_MAX,20000
ATC_ANG_RLL_P,8
ATC_ANG_PIT_P,8
ATC_ANG_YAW_P,5
ATC_RAT_RLL_P,0.18
ATC_RAT_RLL_I,0.18
ATC_RAT_RLL_D,0.009
ATC_RAT_PIT_P,0.18
ATC_RAT_PIT_I,0.18
ATC_RAT_PIT_D,0.009

Finish setting up your battery and failsafe settings properly.
Do some flight tests with a bit more hovering and flying around with gentle stick inputs, it’s easier to see what’s going on in logs.

1 Like
7

Create a new post rather than confuse the original post with your problems.

8

Thanks for detailed response. I have changed my setup a little bit. I replaced Cube Black with Cube Orange and hard mounted it on the frame without rubber screws. Now vibration are much better under 30. I did also more manual tuning because autotune still gives very sluggish copter and now I think copter is flying ok. That’s my log from flying after manual settings. I will try your settings for autotune :

MOT_THST_EXPO,0.2
MOT_PWM_MIN,1100
MOT_PWM_MAX,1940

ATC_RAT_PIT_FLTD,13.00
ATC_RAT_PIT_FLTT,13.00
ATC_RAT_RLL_FLTD,13.00
ATC_RAT_RLL_FLTT,13.00
ATC_RAT_YAW_FLTT,13.00
INS_ACCEL_FILTER,20.00
INS_GYRO_FILTER,26.00

during next flight. Thanks again for help

9

Yes, please try them and report back.
I’m finding that incorrect filter settings makes Autotune give too low values for PIDs leading to the “sluggish” performance you mentioned. In fact even manually changing the PIDs doesnt have much effect when the filters are wrong, since valid movement (not just noise) can be filtered out, so the PIDs cant correct for it.
Your Z axis vibrations are still a bit high, see if you can get them lower, maybe shielding the FC from prop-wash.
I’d probably slightly alter those PIDs too, but after you’ve adjusted the Filter and MOT_PWM settings
ATC_ANG_RLL_P,6.0
ATC_ANG_PIT_P,6.0
ATC_RAT_RLL_P,0.18
ATC_RAT_RLL_I,0.18
ATC_RAT_RLL_D,0.01125
ATC_RAT_PIT_P,0.18
ATC_RAT_PIT_I,0.18
ATC_RAT_PIT_D,0.01125

Having the D terms too high usually causes motor heating, and you can sometimes hear a “mechanical” noise too. The RAT PIDs might all be a bit high (or not) but we’ll see what happens if you can do a bit of test hovering and gentle flight after making all the changes. If there’s oscillations, land immediately and reduce all the RAT PID values by about 10% and reduce the ANG P values by 10% and try again.

10

Hi
I had opportunity to fly and that’s a log from gentle flight in ALT HOLD without gimbal and camera with my manual settings.

I tried following settings to autotune again:
MOT_THST_EXPO,0.3
MOT_PWM_MIN,0
MOT_PWM_MAX,0
ATC_RAT_PIT_FLTD,13.00
ATC_RAT_PIT_FLTT,13.00
ATC_RAT_RLL_FLTD,13.00
ATC_RAT_RLL_FLTT,13.00
ATC_RAT_YAW_FLTT,13.00
INS_ACCEL_FILTER,20.00
INS_GYRO_FILTER,26.00

I changed MOT_PWM_MIN/MAX to 0 because when I changed to your values (especially MOT_PWM_MIN: 1100) motors started and I couldn’t stop them. I was also a little bit afraid of so low MOT_THST_EXPO). Autotune succeed but again with not so good result. Copter was very sluggish. I just autotuned roll axis.
That’s a log from autotune flight.
and
That’s a log with my manual settings with gimbal and camera.

During take off from folding landing legs copter is vibrating a lot. Is there any solution for that ? It happens only when it’s standing on the ground before take off. Maybe my legs are not so hard mounted to the frame???