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Re: [Paparazzi-devel] Flyover and crash due to pressing takeoff before h


From: Felix Ruess
Subject: Re: [Paparazzi-devel] Flyover and crash due to pressing takeoff before holding point
Date: Wed, 24 Jul 2013 00:06:55 +0200

Hi,

probably a good idea to add something similar to the default flight plans.
But about your solution: that means it will switch to stop 10m above the ground if you try to land autonomously in AUTO2... not quite what we want..

Cheers, Felix


On Tue, Jul 23, 2013 at 10:11 PM, Refik Sever <address@hidden> wrote:
Hi Felix,

Thank you very much for your email. Luckily, there was a minimum damage in that crash. And, we are happy that we found a bug and helped to improve paparazzi. After each crash, we learn something and we haven't crashed in our last 20 take-offs.

Another important point for beginners (like us), is that we generally land using auto1. And in our first flights after landing we usually switch to auto2 by mistake and it immediately gives full throttle. Somebody can get hurt in this condition, especially if the motor is powerful. Therefore, we added something to our flight plan. If the plane goes to standby for once, then we set a variable named "stop" to be "TRUE". And we added an exception that if the altitude becomes smaller then ground_alt+10, we switch to a new block named "STOP", where we kill the power.

This may not be important for an experienced user, but for a beginner I think that it is important for safety. We can consider to put these codes to example airframe files.

Best regards,
Refik

    <block group="home" key="<Control>a" name="Standby" strip_button="Standby" strip_icon="home.png">
<!-- ################################################## -->
      <set value="TRUE" var="durdur"/>
<!-- ################################################## -->
      <circle radius="nav_radius" wp="STDBY"/>
    </block>

<!-- ################################################## -->
   <exception cond="(ground_alt + 10 > GetPosAlt()) && stop" deroute="STOP"/>
<!-- ################################################## -->

 <!-- ########################################################################## -->
    <block name="STOP">
     <attitude roll="0.0" throttle="0.0" until="FALSE" vmode="throttle"/>
    </block>
<!-- ########################################################################## -->
_______________________________________

Message: 1
Date: Tue, 23 Jul 2013 18:57:22 +0200
From: Felix Ruess <address@hidden>
To: Paparazzi devel list <address@hidden>
Subject: Re: [Paparazzi-devel] Flyover and crash due to pressing
        takeoff before holding point
Message-ID:
        <CAEc+GFeC25wynFMSsX2zxkB2=F210mNnicTuyoZtUY2T7_=address@hidden>
Content-Type: text/plain; charset="utf-8"

Hi Refik,

really sorry to hear about this, and even more sorry that this was due to a
bug!
I was able to reproduce in simulation and it was definitely not proper
behaviour.

The problem was that the initialization of the state interface was done
after initializing the INS instead of before.
This had the very very nasty effect that the local coordinate system was
not initialized if NavSetGroundReferenceHere() was not called from the
flight plan.

This is fixed now in latest master and v5.0. (Did not affect v4.0 and v4.2)
See
https://github.com/paparazzi/paparazzi/commit/635a14dbb0ecb34db3ca888afdffb6cd6808a84d

But of course Christophe is right in pointing out possible consequences of
skipping the GeoInit.
However it is totally fine to skip _iff_ the location and altitude
specified in your flight plan is correct.

Cheers and sorry again,

Felix

P.S. It really seems that everyone was really using the geo init, otherwise
this would have come up earlier already.


On Fri, Jul 19, 2013 at 8:12 AM, Christophe De Wagter <address@hidden>wrote:

> Sorry about your crash. A plane is not designed to crash if you press
> take-off before holding point, but skipping the boot sequence can have
> significant consequences. But you are free to "choose" that in your
> flightplan.
>
> If your flightplan has a GeoLocate call to shift the entire plan to the
> current location (including altitude) then it can be pretty important to
> execute that (holding point). Default flightplans wait 10 seconds after the
> first lock. But you can also set the correct altitude in the waypoints
> directly and make a flightplan without GeoLocate where you can take-off the
> very second GPS goes green or in theory maybe even before.
>
> Now I see you also use energy_control, which can dive to increase speed
> when too slow. If altitudes are not correct, the take-off-block exception
> can be triggered early and the plane will not take-off with full-power and
> a fixed pitch until 30m above ground but instantly switch to energy-control
> that might think that your airspeed is so slow that it needs to dive
> (depends on launch speed).
>
> So: skipping Holding point is not designed to crash, but skipping the boot
> sequence can have nasty effects indeed. Most often aborting the boot
> sequence with a GeoLocate call will not allow you to take-off as you are
> too far from HOME and remain in kill. If you are in a hurry and want to
> take-off the second you get GPS, then change your flightplan to not wait 10
> seconds afterwards, but that is not recommended either as the GPS
> internal co-variance is still very high the first seconds.
>
> -Christophe
>
>
> On Fri, Jul 19, 2013 at 12:42 AM, Refik Sever <address@hidden>wrote:
>
>> Dear all,
>>
>> Today, we had a crash. I am sending the logfiles and conf. files in the
>> attachment.
>>
>> We power on the autopilot at 512. second and we pushed the takeoff button
>> at geoinit state before it wrote holding_point (539th sec). Then we had a
>> take off using auto1. After climb, we switched to auto2. It wrote standby
>> in GCS and the green circle was put on the map, but the plane turned left
>> directly and went away. I switched to auto1 and tried to get back the plane
>> but the distance was too large and we had a crash.  I checked the desired
>> course in the replay, and it was actually 270deg.
>>
>> I did a simulation and pushed the takeoff button before it wrote holding
>> point. It did exactly the same in the simulation. I am using paparazzi
>> version of 4.9_devel-812-g8f341f0-dirty.
>>
>> I remembered that, I saw this behavior 2-3 months ago in the simulations.
>> But I thought that there was a problem in the simulation and forgat it.
>>
>> Is this a bug or is this a planned behavior? I think that we need to put
>> warnings with bold letters: "Do not press take off before holding point".
>>
>> Although it was a terrible crash with directly diving to the ground with
>> full throttle, the damage was not too bad. We fixed the plane and tomorrow
>> we will continue our flights.
>>
>> The plane circles perfect, tomorrow we will try other navigation options.
>>
>> Best regards,
>> Refi
>>
>>
>> _______________________________________________
>> Paparazzi-devel mailing list
>> address@hidden
>> https://lists.nongnu.org/mailman/listinfo/paparazzi-devel
>>
>>
>
> _______________________________________________
> Paparazzi-devel mailing list
> address@hidden
> https://lists.nongnu.org/mailman/listinfo/paparazzi-devel
>
>
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Message: 2
Date: Tue, 23 Jul 2013 11:57:59 -0600
From: alonso acu?a <address@hidden>
To: address@hidden
Subject: Re: [Paparazzi-devel] how to select an airframe
Message-ID:
        <address@hidden>
Content-Type: text/plain; charset="iso-8859-1"

Thanks to all the people that have responded, this is a great discussion.


>
> - How heavy is your payload (camera)?
> - How large is your payload (camera)?

We have 3 cameras: a multispectral, a Canon Powershot ELPH 320 and a  DSLR.
The first 2 are small and weight is less than 150g. The other one is bigger
and could go over 600g.  Primary goal is to use the first 2 and the other
one would be bonus or would be served later by a different plane.

>
> - Do you need vertical view only?

Initially yes but oblique photo would be a bonus (would be done with the
heavier camera and perhaps with a different plane).

 >
> - Do you have experience in RC planes?
> - Do you have experience in model gas engines?

I am working with very experienced people in building planes, electric and
gas, and flying them manually. I think I would prefer electric.

>
> - Do you have experience in Paparazzi?
>
I am working with people experienced in programming (including me) and
electronics. We will be investing whatever time it takes to be able to
answer yes to this question. We are just starting.
We might use a smaller cheaper plane with no camera for flight testing and
learning and then move to the primary plane when we feel confident.

 > - Do you have a runway available?
>
For testing yes. For real work we will be taking photos at multiple
locations all over our small country so perhaps a dirt road or a grass
field is all we'll find. I would like to know how big is the space needed
to takeoff and land and whether designs can be adapted to do shorter
landings. We might consider parachutes or nets or whatever.


50 minute flight would be OK.  The Bormatec Maja is advertised with 50 min
endurance with 3S/6000mAh and 500W motor with 1,5kg payload inclusive of
batteries. As seen on http://conservationdrones.org/hardware/
My plan is to build our own airframe as these are too expensive to buy and
we have the guys who can build planes from scratch if necessary. They don't
have experience with this kind of application or automated flying, so we
are unsure about the design to use.

Thanks again for all the help.

Alonso Acuna


On 23 July 2013 11:02, C?dric Marzer (priv?) <address@hidden> wrote:
> The question about the runway is very relevant indeed as you can achieve a
> long flight duration either by having a relatively high wing load, for
> instance with a 2 m plane with a landing gear packed with batteries

I am curious how long a runway you need - and also if paparazzi
handles landing or whether that's something that has to be done by
hand? (I'm still very much a paparazzi noob!)

> or if
> you don?t have a runway you will need a plane with a nice aerodynamic and
> less wing load (I am thinking for instance of f3j gliders) but you will
have
> more problems with wind?
>
>
>
> De : paparazzi-devel-bounces+spam1=address@hidden
> [mailto:paparazzi-devel-bounces+spam1=address@hidden] De la part de
> Hector Garcia de Marina
> Envoy? : mardi 23 juillet 2013 11:53
>
>
> ? : address@hidden
> Objet : Re: [Paparazzi-devel] how to select an airframe
>
>
>
> Hi C?dric,
>
>
>
> would you mind to show such setup? I am curious about the flight autonomy,
> payload, total size and weight of the plane etc.
>
>
>
> Reto also points out a good remark, it seems that you will need a runway
for
> this kind of airplane (or at least, a nice big launcher :P).
>
>
>
> On Tue, Jul 23, 2013 at 11:43 AM, C?dric Marzer (priv?) <address@hidden
>
> wrote:
>
> I would use an electric plane every time it is possible : less vibrations,
> better reliability, less noise.
>
> 50+ minutes flight isn?t difficult to achieve with the right plane and
> enough batteries.
>
>
>
> De : paparazzi-devel-bounces+spam1=address@hidden
> [mailto:paparazzi-devel-bounces+spam1=address@hidden] De la part de
> Reto B?ttner
> Envoy? : mardi 23 juillet 2013 11:24
> ? : address@hidden
> Objet : Re: [Paparazzi-devel] how to select an airframe
>
>
>
> There are countless options for your application. To give an appropriate
> advice we would need some more information:
>
>
>
> - How heavy is your payload (camera)?
>
> - How large is your payload (camera)?
>
> - Do you need vertical view only?
>
> - Do you have experience in RC planes?
>
> - Do you have experience in model gas engines?
>
> - Do you have experience in Paparazzi?
>
> - Do you have a runway available?
>
>
>
> Regards, Reto
>
>
>
>
>
> 2013/7/23 Chris Gough <address@hidden>
>
> I agree with Hector that petrol engines are the cheapest way to get
> endurance, and probably a good fit if you really do need 50+ minutes
> endurance. I would add a suggestion that you consider stepping up to
> longer flights after mastering short ones on a plane that forgives
> crashes. For example:
>
>  * a cheap plane with replaceable parts, e.g. skyfun, bixler, etc
>  * a rugged flying wing, e.g. EPP core with a stressed plastic skin.
>
> It's less critical if you are already an experienced RC pilot, but
> still probably a good idea.
>
> In the paparazzi source tree, have a look at
> "conf/airframes/examples", but please understand that you almost
> certainly will have to understand and edit your own configuration.
>
> Chris Gough
>
>
>
> On Tue, Jul 23, 2013 at 3:52 PM, Hector Garcia de Marina
> <address@hidden> wrote:
>> In my opinion, you should aim for a gas hi-wing plane if you want more
>> flights of more than one hour.
>>
>> On 23 Jul 2013 04:41, "alonso acu?a" <address@hidden> wrote:
>>>
>>> Hello. I am looking to build a UAV to take photos to make maps. I need
>>> stability and endurance around 50min or more with a small camera. I have
>>> seen so many options and don't have an idea of which one would be better
>>> for
>>> use with paparazzi.
>>>
>>> Also I am wondering how difficult is it to get paparazzi working with a
>>> new airframe.
>>>
>>> Even if I try to stick to one that has been tested I am not sure how to
>>> select one that is in active use so I could request help from other
users
>>> and give feedback.
>>>
>>> Any pointers would be greatly appreciated.
>>>
>>> Thanks
>>>
>>> Alonso Acu?a
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