Re: [Paparazzi-devel] Strange throttle behavior

[antoine drouin]

I just looked at the file and noticed that someone added a sort of low
pass filter in there. It would probably be nicer to handle the
dynamics of the commands in the stabilization layer.

On Tue, Dec 20, 2011 at 1:14 PM, antoine drouin <address@hidden> wrote:
> take a look at
>  paparazzi/sw/airborne/firmwares/rotorcraft/actuators/supervision.c
> This was my first attempt at handling actuators saturation issues. You
> are correct that the attitude stabilization is given priority over
> vertical guidance. It's based on the assumption that the angular
> dynamic is faster than the vertical one.
>
> Poine
>
> On Tue, Dec 20, 2011 at 1:06 PM, Simon Wilks <address@hidden> wrote:
>> Hi Felix,
>>
>> On Tue, Dec 20, 2011 at 2:09 AM, Felix Ruess <address@hidden> wrote:
>>>
>>> Hi Simon,
>>>
>>> yes, when it's armed the motors will idle at low rpms with zero
>>> throttle on the RC.
>>> From your config it looks like you were testing in attitude_direct
>>> mode?
>>
>> Correct.
>>
>>>
>>> In that case the guidance_v p gain does not play any roll at
>>> all, since throttle is directly controlled via RC.
>>
>>
>> I see. I will give it a try seeing Eduardo seems to think it helps. It will
>> at least not hurt if it isn't used.
>>>
>>>
>>> I haven't heard or experienced your problem with throttle lag
>>> before... maybe it's a problem with 8 motors and i2c? That is a shot
>>> in the dark, but you could test with increasing the i2c queue to more
>>> than 10 (that's just what others reported on the mailing list for 8
>>> motors).
>>>
>>>
>>> When you hold the quadcopter with zero throttle and tilt it a bit it
>>> should immediately try to compensate for that.... sluggish response to
>>> that might indicated an i2c queue problem...
>>
>>
>> When I tip the copter in any direction it seems to respond correctly and
>> very quickly. I will probably give the i2c queue adjustment a try as well.
>>>
>>>
>>> With respect to switching off attitude control at zero RC throttle
>>> input: I didn't quite get why you'd want to switch that off and IMHO
>>> opinion that is not such a good idea (at least I can't think of a
>>> reason right now).
>>> E.g. when you want the copter to fall really quickly and you take the
>>> throttle to zero, you really don't want stabilization completely
>>> switched off.
>>
>>
>> OK, I agree that it probably isn't a good idea then :) Didn't think of that.
>>
>> The throttle issue only happens when the copter is in flight and I have
>> never noticed something like this when throttling up (and then down) while
>> remaining on the ground. I wonder if this is an effect of it overdoing the
>> attitude control as it should be sinking and it just puts too much power
>> into the stabilization attempts, at least for an octocopter?
>>
>> Thanks,
>>
>> Simon
>>
>>>
>>> If one wanted to do that at all, one could think about using something
>>> like the autopilot_in_flight state to check if the copter is not in
>>> flight AND the rc throttle at zero to switch it off... but that would
>>> need some modifications for takeoff.
>>>
>>> Cheers, Felix
>>>
>>> On Mon, Dec 19, 2011 at 7:42 PM, Simon Wilks <address@hidden> wrote:
>>> > On Mon, Dec 19, 2011 at 6:23 PM, Eduardo lavratti
>>> > <address@hidden>
>>> > wrote:
>>> >>
>>> >> As i tell you ... i have the same behavior when i using a HIGH valeu on
>>> >> guidance_V P parameter.
>>> >
>>> > OK, got it.
>>> >
>>> >
>>> >>
>>> >>
>>> >> This is the first think that i will modify in PPZ software.
>>> >> When the throttle is around 0 the ATTITUDE control stop control the
>>> >> motors.
>>> >
>>> > That would be great. This is pretty nasty (and extremely surprising)
>>> > behavior.
>>> >
>>> > Thanks
>>> >
>>> > Simon
>>> >>
>>> >>
>>> >>
>>> >> ________________________________
>>> >> Date: Mon, 19 Dec 2011 09:56:34 +0100
>>> >> From: address@hidden
>>> >> To: address@hidden
>>> >> Subject: Re: [Paparazzi-devel] Strange throttle behavior
>>> >>
>>> >>
>>> >> I just replayed the logs and the GCS shows the throttle input going to
>>> >> 0%
>>> >> after about 3 secs but the octocopter was clearly still flying for
>>> >> another
>>> >> 3-4 secs after this I till I hit the kill switch.
>>> >>
>>> >> On Sun, Dec 18, 2011 at 10:13 PM, Simon Wilks <address@hidden>
>>> >> wrote:
>>> >>
>>> >> On Sun, Dec 18, 2011 at 10:06 PM, Hector Garcia de Marina
>>> >> <address@hidden> wrote:
>>> >>
>>> >> Yeah,
>>> >>
>>> >> regarding the safety, I agree with Eduardo, next time DO NOT run next
>>> >> to
>>> >> the copter if you have lost its control until it completely
>>> >> is switched off.
>>> >>
>>> >>
>>> >> Yes you are right. I should keep clear till it has settled.
>>> >>
>>> >>
>>> >>
>>> >>
>>> >> Cheers
>>> >>
>>> >>
>>> >> On Sun, Dec 18, 2011 at 9:31 PM, Eduardo lavratti
>>> >> <address@hidden>
>>> >> wrote:
>>> >>
>>> >> Hey man ... take care with your tests !
>>> >> This props and motors are very POWER and DANGEROUS !
>>> >> Take a look at this pictures
>>> >> http://brquad.blogspot.com/2011/04/little-acident-with-my-big-hexa.html
>>> >> This accident occurred when i make some tests with my big hexa whit
>>> >> same
>>> >> motors and props.
>>> >> Never make this tests with children arround.
>>> >> Well, for the JUMP problem reduce the "guidance_V / hover_KP" and make
>>> >> a
>>> >> test.
>>> >>
>>> >> Make the same for wooble. Reduce the P & D GAIN parameter for Theta and
>>> >> Phi . You see this values in STABILIZATION_ATTITUDE section.
>>> >> Reduce P for 300 and make a test.
>>> >>
>>> >> Stay sure that your props are very well balanced or your lisa board
>>> >> have a
>>> >> good vibration isolation.
>>> >>
>>> >> When i make my first fly using lisa/m i have similar attitude on me
>>> >> small
>>> >> octo (5"props) and on my quad (8" props)
>>> >> after i balance the props and make a good vibration isolation all
>>> >> problems
>>> >> are solved.
>>> >>
>>> >> Regards and sorry for my poor english.
>>> >>
>>> >> Eduardo Lavratti
>>> >> Brasilian UAV developer.
>>> >>
>>> >>
>>> >> ________________________________
>>> >> Date: Sun, 18 Dec 2011 20:38:21 +0100
>>> >> From: address@hidden
>>> >> To: address@hidden
>>> >> Subject: [Paparazzi-devel] Strange throttle behavior
>>> >>
>>> >>
>>> >> Hi
>>> >>
>>> >> I have been noticing what seemed like a lag in throttle control though
>>> >> I
>>> >> wasn't 100% sure till my first test flight today (octocopter, lisa/l,
>>> >> spektrum satellite receiver). While on the ground I don't seem to
>>> >> notice
>>> >> this effect but when holding it above my head or lifting off strange
>>> >> things
>>> >> start to happen.
>>> >>
>>> >> When holding it above my head changing the throttle on the sender seems
>>> >> to
>>> >> take a second or two till it happens on the copter. I have also noticed
>>> >> what
>>> >> seems to be a general increase in throttle all of sudden, not just to
>>> >> correct attitude but like a it wants to pull up and away.
>>> >>
>>> >> When I tried the first flight today I got a bit of a shock when I
>>> >> wanted
>>> >> to just lift off a bit then set down only to discover it did not want
>>> >> to
>>> >> respond to the fact that I had returned the throttle back to zero and
>>> >> skipped off across the garden. In the end I had to flick the kill
>>> >> switch.
>>> >> Pretty funny after the event. I have a video if you want a laugh here.
>>> >>
>>> >> You will see the props rotating at minimum speed (zero throttle on the
>>> >> sender) after arming. I assume this is correct? One of the props isn't
>>> >> rotating properly and I suspect it might have a problem and need
>>> >> swapping
>>> >> with a spare (it has a bit more resistance to the hand when rotating
>>> >> than
>>> >> the others) but I thought it might be OK to try a small hover anyway.
>>> >>
>>> >> Any ideas what causes this kind of throttle behavior? Pitch and roll
>>> >> seem
>>> >> pretty responsive. Here is the aircraft config.
>>> >>
>>> >> Thanks
>>> >>
>>> >> Simon
>>> >>
>>> >>
>>> >>
>>> >>
>>> >>
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>>> >>
>>> >>
>>> >>
>>> >> --
>>> >> Héctor
>>> >>
>>> >>
>>> >>
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