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Re: [Paparazzi-devel] Strange throttle behavior


From: Felix Ruess
Subject: Re: [Paparazzi-devel] Strange throttle behavior
Date: Tue, 20 Dec 2011 02:19:12 +0100

and something else: the <configure name="MKK_I2C_SCL_TIME"
value="50"/> has no effect for stm32 based boards like Lisa/L.
There the i2c speed is currently fixed in the I2C1_InitStruct.

Cheers, 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? In that case the guidance_v p gain does not play any roll at
> all, since throttle is directly controlled via RC.
>
> 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...
>
> 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.
> 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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>>>
>>>
>>>
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>>
>>
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