Octaquad, unstable altitude hold

ArduCopter Copter 4.0
1

Hello!

I’m trying to tune my small octaquad and I have some issue with Altitude hold function.

It is a 7 inch octaquad running at 4s with a flight time of 26 min. As you can see from log, it is a bit overpowered.
aircraft use an old VR Ubrain 5.1 running AC 4.0.7.

I recently enable notch filter and I think/hope I configured it correctly.

The issue is that in alt hold, it is not stable and move up and down for about 2-3m minimum and while moving forward I can hear motors increasing and decreasing quite rapidly.

Attached also the full parameter list octaquad.param (17.6 KB) 2021-04-11 17-30-05.bin (1015.1 KB)

2

no one can help? Do you need more info?

3

The 1st thing to notice are these parameter values.
ATC_ACCEL_P_MAX,1800000
ATC_ACCEL_R_MAX,1800000

These are off by a factor of 10 so essentially it’s unlimited. Your filter values are too low for a 7" craft. Run the Mission Planner Plug-in from Alt>A and reconfigure.

Also MOT_SPIN_MIN is higher than MOT_THST_HOVER.

4

Never heard about ALT>A, what it does?

5

Connect to Mission planner and hit Alt>A. It’s the Initial Tuning Guide plug-in.

6

hello there,
performed the Alt+A function and now copter looks a bit better. I got another strange issue. During translated flight or forward, quad is “vibrating” on the Z axis. It look like that throttle control is too aggressive.

Once again attached parameter filed and log octaquad updated.param (17.7 KB)

https://drive.google.com/file/d/1LcTdLVeGEqncsFD195_RVqJwwbuc9hF_/view?usp=sharing

7

You can try setting these:
PSC_ACCZ_I to 2 x MOT_THST_HOVER
PSC_ACCZ_P to MOT_THST_HOVER

It needs tuning. Run Auto Tune.

1 Like
8

can it run autotune for altitude?

1 Like
9

No but when it tunes pid settings correctly it removes vibration slightly and makes the altitude hold more accurate

10

After setting :

PSC_ACCZ_I to 4 x MOT_THST_HOVER
PSC_ACCZ_P to 2x MOT_THST_HOVER

with MOT_THST_HOVER= 0.12

I had to increase PSC_POSZ_P from 1.0 to 2.0

11

Yeah, dropping PSC_ACCZ_P and then set PSC_ACCZ_I to 2x the value will stop the motor pulsing, I’ve not figured out how to increase the ALT hold strength Yet - seems my baro bounces about in MP (like most do)

12

Thanks Redshifft,

usually the ardupilot system that I setup are not that overpowered.