Re: [Paparazzi-devel] Magic values

[Reto Büttner]

Hi guys

Felix's Bixler airframe config file looks like a fine starting point.
Just some minor comments to my experience:

1. To prevent a 3S LiPo from damage use:

CATASTROPHIC_BAT_LEVEL 9.0 V
CRITIC_BAT_LEVEL 9.5 V
LOW_BAT_LEVEL 10.0 V

2. Altitude Control

ALTITUDE_PGAIN 0.075: Is a good starting point. To get close altitude
control be prepared to increase this value while tuning. Maybe to 0.01
or even 0.02.
AUTO_THROTTLE_MIN_CRUISE_THROTTLE 0.4: To give the throttle controller
a larger working range I use 0.2 or even 0.0.
AUTO_THROTTLE_MAX_CRUISE_THROTTLE 0.8: To give the throttle controller
a larger working range I use 1.0.
AUTO_THROTTLE_IGAIN 0.1: Might be a bit high to avoid oscillations.
You might want to start out with a lower value. It is a good strategy
to start out with low igains when tuning an airframe.

3. Horizontal Control

COURSE_PGAIN 0.7: Is a good starting point. To get close course
control be prepared to increase this value while tuning. Maybe to 1.2
or even 1.8
COURSE_DGAIN: To get close course control while avoiding oscillations
I always use some dgain. A value between 0.2 and 1.0 might work well.

Follow the tuning instructions on the Wiki closely. First trim
precisely in manual, then in Auto1. Check control reactions in Auto1
and then try Auto2.

I just tuned my Cougar Hotliner and set a new record for the T3
Contest Figure 8:

http://diydrones.com/profiles/blogs/restarting-the-t3-contest-now-with-copters?id=705844%3ABlogPost%3A700749&page=12

Happy landings,
Reto

2012/6/19 Felix Ruess <address@hidden>:
> Hi Tilman
>
> since we don't really have one standard airframe setup for beginners I would
> propose to make the Bixler that one (with Lisa/M 2.0 and Aspirin 2.1).
> I added a really simple no-frills example for a
> Bixler: 
> https://github.com/paparazzi/paparazzi/blob/v3.9/conf/airframes/examples/bixler_lisa_m_2.xml
> The gains are not tuned (I don't have a Bixler), so this is just a start...
> you also need to make sure the servo defines are ok for your airframe.
> I'll be happy to update that example if you have a known-to-work config...
>
> It is probably better for you to start with a basic setup before you start
> adding/using some additional options and picking random stuff together from
> other airframe files...
> So in that example the IMU, AHRS and control runs at the default 60Hz. You
> can do better if you increase that, but that adds more complexity in
> configuration...
>
> About the aileron diff... I guess it is nice but probably not really needed
> in most cases (I didn't add it in the example to limit confusion).
>
> The adaptive control is not especially documented so far, but you probably
> don't gain that much by using it if you don't have an airspeed sensor...
> To use it you would have to specify the type="new" for the control
> subsystem.
>
> It would be really nice if we could get _one_ example setup that is know to
> work really well. The Bixler is probably a good choice there, but the
> drawback is that probably none of the really experienced Paparazzi's has
> one? But it should be similar to an EasyStar (but with ailerons).
> Would be good to update that example with your final tuned values once it
> flies well so the next one with a bixler doesn't have to start tuning
> again...
>
> I also added a section about the default LED assignments on Lisa/M
> 2.0: http://paparazzi.enac.fr/wiki/Lisa/M_v20#LEDs
> You can of course change these via the configure options, but there is
> probably no need for that....
>
> Anyways it would be good to get some input from some fixedwing people on a
> standard setup...
>
> Cheers, Felix
>
>
> On Mon, Jun 18, 2012 at 9:39 PM, Tilman Baumann <address@hidden> wrote:
>>
>> My Bixler Airframe is nearing completion.
>> But I'm absolutely overwhelmed by the number of magic values in my
>> airframe file.
>>
>> I based my config on another 5 channel airframe I found in the sources.
>> Whic was basically cargo cult configuration.
>> With this I copied a lot of things that are probably absolutely wrong for
>> my plane.
>>
>> I tried to reduce those magic values to a minimum but it does not seem to
>> compile with many of those. I commented out a bunch but there is still a lot
>> left.
>> For most of those values a Wiki search brings no results, or no indication
>> for safe defaults.
>>
>> I'm sure that I have to eventually do some tuning. But I would like to do
>> this incrementally and based on some sane defaults.
>>
>> Also there is stuff like aileron mixing in the command laws. They look
>> cool. But should I use that or better not?
>> And this mixing of rudder and ailerons also happens in MANUAL mode. Good?
>>
>> Also there is this adaptive control loop. Is that on by default? I don't
>> find options for it. Or should I not use that anyway?
>>
>> I pasted a copy of my config. You see all the FIXME and the commented
>> stuff.
>> http://piratepad.net/FSUEQOzM99
>>
>> I suppose I have to do a lot of tuning. But perhaps if any of you see some
>> big no-no's there or like to comment on choices I have taken (or rather
>> ignored).
>> I would hate to start with a totally botched up setup. Would be nice if it
>> actually flies. :)
>>
>> Comments welcome.
>>
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>
>
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