Please help alt/pos hold tuning

[HeliHenkie]

Hi all,

After weeks of trying I finally succeeded getting RTH to work as it should.
In the end it appeared I was using the wrong switch combination ........... my problems had nothing to do with my setup.
Great performance, my quadcopter cuts through the air like a warm knife through butter. No overshoot, just back to home pos.

But now I'm focusing on alt/pos hold. I just don't seem to be following the right tuning procedure.
My mag and acc and gyro data are relatively clean, so it should be able to work.
When I engage alt/pos hold my quadcopter hold altitude for about 3-5 seconds and then slowly starts to drop for a meter.
Sometimes it recovers, but most of the time it descends till it touches the ground.

These are my PID settings.

nav_alt.JPG (44.81 KiB) Viewed 7961 times

Any suggestions how to proceed?

Best regards,

Jan Willem

[chschmid]

I have the same issue. What I found is that alt_speed_I might be too low.
Thats what I try when the weather allows it.

[LPR]

Jan

I had the same problem. Steve told me it's most likely a small correction in the accelerometer adjustment is needed.
I found you can get a fairly good altitude hold be just increasing the navi alt position P. As you increase the P you should increase navi alt position "I" or you will not get the quad hit the same altitude ever time.
Edit
On the quad I'm using P = .7, I = 4.
The octo I use P = .4, I = 2.

Larry

[plexus]

I had that at the beginning. I reduced the speed I. See mine parameters.
download/file.php?id=1425&mode=view

But before that, you must see at which value is the throttle for the hold position. It must be tuned at 700 (adjusted by factor trotlle) because switching
to manual, the flaps down, the craft can jump to the sky if too high or go down if too low.
The dead band of 40, on my opinion, is a little bit too short, 50 seems better to adjust the hold position.
I think you known all that, sorry if I disturb you.

[LPR]

plexus

I have my throttle set to spring to center on the DX8 Spectrum. The spectrum DX8 throttle can be set to spring to the center by just using a small screw driver. Now I always know the throttle is centered. It works really well and is not hard to get use to.

Larry

[plexus]

Ok LPR , but in flight when the craft is hovering, have you read the value of the throttle in the QGC "chart log viewer"
Have you seen that post:
viewtopic.php?f=27&t=539&start=10

to resume:
If hover is 400 , and factor throttle 0.7, hover must be at 700.
to get 700:
400/700x0.7= 0.4
700/700x0.4= 0.4 ( factor throttle in special setting QGC, stick channel 0, mot_throttle)

The value must be a little bit adjusted.