im having some problems with throttle in the latest version, there are two problems which might turn out to be two seperate issues, but could quite easily be related.
low-end throttle range just doesnt get low enough, flying in an updraught today (where the slope soarers meet) i couldnt maintain a hover. trying to get the throttle low enough i was actually stopping the motors in flight, the throttle stick was so low my timer wasnt even running most of the time. i also noticed the same problem to a certain extent this afternoon in turbulent but not constant updraught conditions. flying with 400g of camera it was better, but with no load and AUW of 2Kg i need less throttle!
altitude hold in loiter is very unpredictable - every time i go into LOITER the cruise throttle value is very different and the result is usually a climb or descent, ive tried this in very different conditions and it seems only about one in five attempts actually result in altitude hold. position hold in loiter is working well, even in some wind. my first flights with v2.5 had the same tendency, but after a few attempts the throttle trim adjusted to a reasonable value and worked from then onwards.
ive recalibrated my radio, although all the trim values came out exactly the same and theres been no change in the behaviour. ive also just gone through the standard parameters to reset my throttle PIDs to default, they werent very different:
is there anything else to look at in config? ive never had alt hold problems before. attached logs, one with attempted loiters in a gentle breeze yesterday, and one trying to hover but climbing with throttle at minimum today.
ok i found the change by jason defining new max and min throttle values in config.h, where before we had:
# define MINIMUM_THROTTLE 130
and now this is defined as 200. i will change mine to 150 which i expect should help at least with the first point, though i dont know if its going to help with loiter.
I think max and min throttle values should be an adjustable parameter. Can that be added in the next release ?
in the config parameters there are values: THR_MIN and THR_MAX
THR_MAX at least corresponds to the value in config.h (1000), while in my case at least THR_MIN is at zero. i must try and work out if these are the same values and would permit us to override whats set in the code.
You're probably right that they should be adjustable. I've created an issue here. I can't guarantee if it'll get into 2.7 or not just yet.
Sounds like you have a very powerful quad to be honest.
Thanks. Sounds like a plan! I posted a pic of my quad build on this site. When I launched it for the first time in stable mode I was grinning ear to ear, then quickly realized I had to limit my throttle.
I've been playing with the simulator and hopefully will attempt loiter mode this weekend.
450mm frame that consists of fiberglass and g10 platform decks that hold the arms and electronics
I wanted it to be small enough to get into my Jeep Wrangler while still achieving decent lift.
1200kv motors, 10.5" props from 3d robotics
right now with 2200ma battery I am weighing in a 780g
Once I get the camera gear and larger battery I think I'll be around 1700g
I have a KK X525 with an APM2 and for a really inexpensive Quad it is a little hot rod.
Changing to 2.6 put me in the position of nearly being at take off as soon as I moved my stick above full off.
It also put me completely outside the flattened throttle curve I had set up for 2.5.
From what I can interpret here, it seems to me that 200 is too high a figure for THR_MIN and should at least be set back to where it was in the 2.6.1 release which I have no doubt is coming out real soon now.
Having an adjustable param at least for THR_MIN would be a great thing although I can see that THR_MAX could be problematic because of the way the manual override throttle "bump" is performed in the Arducopter.C file.
I've adjusted so many parameters that thought a clean install would be in order!
with the previous fw, I thought it was 2.6 but it might have been 2.55 because I installed it using planner mav 0.9 where 1.0 is required with 2.6 ! Anyway with default params I was experiencing:
Very poor yaw reaction
swinging about 50 ft while in Loiter (mag declination on auto)
Now with a fresh 2.6 install:
Moderate yaw reaction, but still too mild
Loiter Mode= much less swinging around (mag declination now on manual) & windy
Now needs a boot full of throttle when going into Alt Hold and Loiter or it will drop like a stone( this is new, about 1/4 travel increase in throttle required) with a corresponding decrease in throttle required when switching back to stabilize.
Also noticed that props start turning the moment the throttle is off the min stop. i mean like a thou or two off the end stop and the props are turning, disconcerting!
Just for the record, when setting the Tx travels up, are you supposed to do this with throttle trim at minimum or mid setting? I have always used minimum in the belief that the flashed esc's require a very low throttle setting to initiate.
looking through the changes in source, jason has changed the minimum throttle back to the old value and made these values user configurable.
the only doubt for me is whether or not this is the cause of the alt hold problem in loiter, hopefully ill be able to fly tomorrow and find out.
James, Been playing around with the throttle here and managed to get what you were experiencing
reprogrammed stick movements, but this time set the throttle trim to mid position.
The idea was to see if I could get a small amount of dead space by afterwards setting the throttle trim to minimum.
Well I got the dead space alright, but when the props now first start turning they are already running fast enough for take off.
i am currently flying with min/max defined as 150/950 - set in config.h and it has solved all my throttle and alt hold problems. as i say above these values have been updated to be user configurable so as soon as a minor update is released i expect this will be included.