TECS tuning settings completely instable

@Maarten_pa0mhe wrote:

The Ardupilot firmware project is the best initiative I have seen in years.
My problem is not the firmware but my understanding of the tuning. Already for months, and with several crashes, I'm trying to get my Mini Talon stable. The CG is tuned correctly and in manual no problems.
I tried to use parameter files of other users, and used Auto tuning.
On the DIYDRONE forum I also posted related questions but nobody was answering.

But it remains that the altitude is very instable, especially during decents at approach and auto landing.
Normal flight the altitude is stable.

When the approach starts, the plane is at moment at an altitude of 4meters .Normally the plane could just land without throttle.
You clearly see the Pitch is following the NavPitch with a phase_delay of almost 90 degree, you also see a heavy Pitch swing with peak2peak amplitude of 50.
But also the throttle is engaged for 70%, which results in height and speed increase and an overshoot of the "runway"
When the Flare is started, no more throttle, and the Pitch oscillation is damped out.

What I would like to understand what is wrong, I expect something in the TECS tuning ?

I tried to change the following parameters:
TECS_SPDWEIGHT 1.2
TECS_PTCH_DAMP 0.4
TECS_LAND_SRC 0.1
TECS_LAND_TDAMP 0.6 m/s/m
TECS_LAND_THR 10%
But non of the changes gave any improvement.

Plane:
Mini Talon AUW 1200g, 3S 2200mAh battery
Pixhawk, ArduPlane V3.6.0

Please, please help, thanks in advance Maarten

2016-12-22 15-14-30.bin (2.9 MB)

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