Hi to all,
Today with a beautiful sunny day here in France, i went to the field, trying to fine tune my heli (trex 700FB) with my APM 2.6 with 3.1 firware
I have a lot of trouble tuning a very good alt hold, sometimes it is pretty good, and sometimes when i change the altitude manually in alt hold, the heli seems to don’t lock the new altitude until i force it to stop descending with the collective stick and lock again with the heli almost in a stable alt.
Is this normal ?
my settings are near those noted here on the wiki (throttle tuning copter.ardupilot.com/wiki/tradit … er-tuning/ )
A the end of the afternoon, i wanted to try another tuning change by lowering the thr acc imax from 500 to 300, then do a test fly : take off in stabilize, climb up to approx 15m, and switch to alt hold, and then the heli go full neg. collectif !!!. I just have time to switch again to stabilise and have a hard landing with only a landing gear broken .
I investigated every files i can to find the pb and after many hours, i can reproduce it on the bench :
in fact when i arm and switch my trottle switch ON , if i switch to alt hold before 10s , the collectif go full neg. with no automatic corrections, and after 10s every thing come back and automatic corrections are ok.
My rotor speed control is mode 1, i have tried to lower my RSC SPEED UP from 10 to 2 and RSC RAMP from 1 to 0 with no change, the only thing that eliminate the 10s alt hold delay is to change speed control mode to none.
perhaps is there a bug with alt hold controler ?
Thanks for your help,congratulations for your work, and sorry for my poor english
ps: Do you know (the dev team) when we can expect to have the 3.2 ?
I forgot to mention another strange thing :
Some times , when i am in alt hold at a stable altitude and i try to change alt. by moving my throttle stick up, the heli don’t climb (or very slowly)even at full up stick, then i try do descend by lowering the throttle stick, and i have alot of authority for descending ! it’s like if the center stick was changed. So i switch to stabilize and back to alt hold and sometime this behaviour disapear ??
Bruno, do you have the ESC through the APM?
I’m really going to need logs to try to help diagnose your issue.
Yes i have esc through apm and rsc to mode 1, with initially rsc speed up to 10s, and I first assume this was the pb, but after I lower rsc speed up to 2s, I always need to wait approx 10s before alt hold can operate normally.
The only solution i found to eliminate the 10s is to change rsc mode to none, wich eliminate ARM security on the esc
I’m sorry but I can’t post logs this WE because I don’t have the computer with me, but i will post on monday.
Again thanks for your help
here is my last log, with stabilise and alt hold
,[quote=“bruno-16OOO”]Some times , when i am in alt hold at a stable altitude and i try to change alt. by moving my throttle stick up, the heli don’t climb (or very slowly)even at full up stick, then i try do descend by lowering the throttle stick, and i have alot of authority for descending ! it’s like if the center stick was changed. So i switch to stabilize and back to alt hold and sometime this behaviour disapear ??[/quote]
I can’t reproduce this on my last fly
Hi Bruno, I had a look. First off, the vibration levels are really high. Way too high. You need to work on that. How is it mounted? I’m surprised it holds altitude at all.
There may also be problems with the Alt Hold tuning, as well as Roll and Pitch, but there’s no point working on those until the vibrations are solved.
One more time you’re right
vibrations seems to be the problem, especialy y axis if I understand the log, so I tried some dampeners with no effect (probably not the good dampeners) so I tried to lower the filter from 20 hz to 10hz, and way better (about -3/+3 on y axis), so I tried lower again filter to 5hz, and vibrations drop to -2/+1 (y axis) and I redo the setup from start, and now the alt hold and loiter are good (probably some tuning to improve again but don’t have more time today)
Is it a pb to fly with filter on 5hz ?
I always have the delay before alt Hold to be full active after starting motor, is it normal ?
Do you know if 3.2 will be soon ready
thanks for your help,
I’ve never flown on 5Hz, I usually use 10Hz. So I can’t really say how well it will work out. In fact, I’ve been wanting to use 20Hz to try for better response.
I think you should probably spend more time trying to solve the source of the vibrations. Are your blades very well balanced? Are they tracking well? All shafts straight? Bearings in good condition? Gears straight with a good mesh? Belt tight enough? If using a torque-tube, is it straight? How many bearings are you using? Some users have reported they get reduced vibration by using 2 or 3 bearings on the torque tube instead of just one.
Yes, there is normally a delay before Alt-Hold will kick in. It is supposed to be controlled by the Rotor Runup Time parameter, but somebody else reported it was not. I need to look into that.
You are right, i’ll have to look to the whole heli to reduce the vibration, however, I have made 3 or 4 flight with 5hz filter (even in auto mode) and everything seems to work normaly.
I’m a little afraid with the alt hold/loiter controler delay, I have made several test on the bench and despite that the time seems to be near 10-15 s most of the time, i have seen 60s delay
Now every time i switch to alt hold or loiter, i climb to 30 meters, just in case…