Thr_Mid Confusion

ArduCopter Copter 3.4
1

I’ve got some confusion about thr_mid…
This might not be a 3.4 issue… I never had any trouble w/ 3.3, but then again, it’s nothing I ever though about… In 3.3, I set thr_mid based on my transmitter throttle stick position, and it works…

Basically, in stab, my transmitter is not far below middle, with the props I’m using at the moment…
So, based on the physical position of my throttle, I’d guess it’s between 450 and 500.
But…
I look at my log, at the ctun throttle setting, as it says to do on the wiki page about setting thr_mid…
There, the throttle is at .26! (I’m assuming that means 260).

I guess my questions is, what’s correct? 260, or ~450? Should I go by transmitter or log?

And about alt_hold performance, it doesn’t seem to make a difference either way!!! Alt_Hold isn’t holding well with either setting… but it does eventually hold with both…
As I said in a different post, it goes up and down by a meter or so for several seconds ,and finally stabilizes at a steady hover… thr_mid set to 300 or 500, it performs exactly the same.

1 Like
2

Later iterations from master 3.4dev will remove that issue, because there’s a new feature that sets TH_MID by itself.

this commit https://github.com/ArduPilot/ardupilot/commit/48eb4cf67464a7c61be38ddf8f57f84d13fe4d36

Limited testing yet, so no feedback.

3

Thanks! That’s great.

And I think I found another (or the) problem… I don’t know what’s acceptable… But my barometer readings are worse on this copter, than on a couple others… The pressure reading has a sort of triangle wave shape on all of them, but the amplitude is double the size on this copter. I’m going to work on that now.

4

The black closed cell foam is our friend :slight_smile:

5

I’ve noticed that sometimes the baro reading is not updating. It is zero when I connect and does not change when I increase the altitude of the Pixhawk. I’ll submit a separate issue.

6

I checked a few of my logs and they all show a changing altitude, so that’s probably not related.

I haven’t had time to try different foam and mounting yet, but that could be the source of this copters alt_hold performance issues. If others aren’t having alt_hold trouble, I’ll assume it is…

And, I guess my other questions about the thr_mid, ctun, transmitter settings doesn’t matter anymore :).

7

Same confusion, same values, same results changing thr_mid but nice althold, check your vibes, here you have lot info about that http://diydrones.com/forum/topics/vibration-isolation-and-dampening-of-apm-px4-for-version-2-9?id=705844%3ATopic%3A1102762&page=1#comments

8

@cala2

Things have been changing with 3.4 and although vibrations are still a possible issue, the behavior for determining mid throttle has changed.

I didn’t have time, yet, to have enough flights with the new features but count on it for the 3.4 release.

1 Like
9

Thank’s Luis, I remember to read something but I searched in Diy Drones and I have the answer in my nose THR_MID vs new CTUN.ThrOut sorry to repeat questions; Some flights now and Im very happy how pixracer+3.4 works with my little copter, great work hardware and software developers :slight_smile:

10

similar problems here

http://discuss.ardupilot.org/t/heavy-y6-adventure-thru-3-4-rc-with-autotune/11488/