Re: [Paparazzi-devel] Suggestions: Auto-tuning of gains and upload via modems

[Maik Höpfel]

Hello,

thank you very much for your clarifications!

Auto-tuning: Okay, as far as I understand it, there's disagreement
about what method to use to get the gains. Once you have the algorithm
down to detect oscillations and all that, I feel like implementing
different methods to get the right gains shouldn't be much effort.
What method do the other Paparazzi users use? I'm afraid I don't know
nothin' about control theory (well, I guess I've understood the
concept of a PID controller by now).

Uploading: How long are we talking about here? I know with our
airplane it the flashing process takes long, because we have to attach
a USB cable deep inside the airframe ;) And no, having an outside USB
connector is not an option for us.
I don't really know how to go about finding the size of a typical
upload, sorry. But with 57600 bauds, I can't imagine things can be
that bad. Thoughts?

Regards,
Maik



2010/6/21 Christophe De Wagter <address@hidden>:
> Uploading used to be over the serial link in the past (2005). Do not
> underestimate the time this took to upload new code.
>
> On Sun, Jun 20, 2010 at 3:39 AM, Eric Parsonage
> <address@hidden> wrote:
>>
>> Hi Florin, Maik,
>>
>> I am sure that ZN would definitely work, but its just how well it works! I
>> am pretty sure ZN is the only option if you cant derive the Transfer
>> Function of the system analytically, so for most people who use paparazzi
>> and haven't learnt that much about classical or modern control, or for
>> airframes that may have weird Dynamics (like a flying wing), it is
>> definitely the way to go. ZN based tuning also results in a controller that
>> is very good at rejecting disturbance, which for level flight is great, I
>> just worry about the step response of that sort of controller in regards to
>> setpoint changes, like rolling into or out of a heavy bank, I fear that it
>> may be very oscillatory. It does of course depend on your aircraft, and
>> whether or not you are constantly changing its attitude.
>>
>> However, Maik does make a very interesting point. the community could
>> probably develop a little script, or even a simple spreadsheet, that assumed
>> you had a straight winged monoplane platform, and took inputs about its
>> geometry, moments of inertia etc. then approximated the  transfer function
>> of the system based on that, with that it could then analytically calculate,
>> using at least a couple of PID tuning methods, the appropriate gains for
>> your system which you could then program in. This could be done without you
>> even having to leave the ground! of course, you would need to do a little
>> bit of manual tuning once you got up in the air, but at least you could have
>> some trust in your controller to begin with. Of course, someone would need
>> to derive the state-space model for a generic aircraft in terms of variable
>> regarding its dimensions. Any of you control gurus wish to comment on this
>> suggestion (I know you are reading)?
>>
>> Eric
>>
>>
>> On 19 June 2010 18:15, Florin Mingireanu <address@hidden>
>> wrote:
>>>
>>> Hi Eric,
>>>
>>> I've used succesfully ZN on flying wings.
>>> I haven't used it on other planes.
>>>
>>> Florin
>>>
>>> On Sat, Jun 19, 2010 at 11:34 AM, Eric Parsonage
>>> <address@hidden> wrote:
>>>>
>>>> Hi Maik, Florin,
>>>>
>>>> I would suggest that ZN tuning would not be that effective, This is due
>>>> to the fact that the ZN algorithms were empirically derived from work with
>>>> process systems which all exhibited a particular response (time delay, big
>>>> phase lag, integrator racking up error to a step input). Perhaps a more
>>>> sensitivity driven algorithm, like kappa-tau, or pole placement, would be
>>>> more effective since aircraft tend to act a lot more like a 
>>>> servomotor-style
>>>> system than a phase-laggy process one.
>>>>
>>>> Eric
>>>>
>>>> On 19 June 2010 17:54, Florin Mingireanu <address@hidden>
>>>> wrote:
>>>>>
>>>>> Hi Maik,
>>>>>
>>>>> The method I tried to describe is called Ziegler-Nichols.
>>>>>
>>>>>
>>>>>
>>>>> On Sat, Jun 19, 2010 at 11:20 AM, Florin Mingireanu
>>>>> <address@hidden> wrote:
>>>>>>
>>>>>> Hi Maik,
>>>>>>
>>>>>> As far as I know, tuning P and I-gains is like:
>>>>>>
>>>>>> increase P value until you detect instability (oscillation as you
>>>>>> said) and then decrease P to half and start to increase I until 
>>>>>> sufficient
>>>>>> stability is obtained.
>>>>>>
>>>>>> If, additionally, you have a D term (d-gain) then you apply
>>>>>> recursively this algorithm for subsequent I and D.
>>>>>>
>>>>>> So tuning gains for a new aircraft is more like a cascaded algorithm.
>>>>>>
>>>>>> Florin
>>>>>>
>>>>>>
>>>>>> On Sat, Jun 19, 2010 at 10:12 AM, Maik Höpfel <address@hidden>
>>>>>> wrote:
>>>>>>>
>>>>>>> Hello dear community,
>>>>>>>
>>>>>>> I recently added two features I would like to see to the Software
>>>>>>> Wishlist in the Wiki, but did not get any feedback. So I'd like to
>>>>>>> present them on the list as well:
>>>>>>>
>>>>>>> 1) Auto-tuning of gains: as far as I see it, the rules for setting
>>>>>>> the
>>>>>>> P-gains on a new aircraft are pretty easy: "turn it up till it
>>>>>>> oscillates, turn down a little". Now given sufficient height and a
>>>>>>> bit
>>>>>>> of trust in the airframe, this should easily be doable by an
>>>>>>> algorithm
>>>>>>> instead of the crew on the ground, shouldn't it? Oscillation can be
>>>>>>> detected via the IR sensors/IMU... I imagine it like a special flight
>>>>>>> plan block that then sets the correct gains.
>>>>>>>
>>>>>>> 2) Flashing via modems: Couldn't the boot loader wait for a special
>>>>>>> sequence from the modems before starting up the Paparazzi code? And
>>>>>>> then the GCS just sends that special message and the firmware that is
>>>>>>> to be flashed? Should be error-checked, of course. But it's possible,
>>>>>>> right?
>>>>>>>
>>>>>>> I'm really looking forward to your thoughts! I think both things
>>>>>>> would
>>>>>>> make Paparazzi even easier to use for beginners.
>>>>>>>
>>>>>>> Regards,
>>>>>>> Maik
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> Paparazzi-devel mailing list
>>>>>>> address@hidden
>>>>>>> http://lists.nongnu.org/mailman/listinfo/paparazzi-devel
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
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>>>>>
>>>>
>>>>
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>>>
>>>
>>>
>>> --
>>> Florin Mingireanu
>>> Romanian Space Agency
>>> Str. Mendeleev 21-25, et. 5, sector 1, 010362 Bucuresti, ROMANIA
>>> office tel. +40-21-316.87.22; +40-21-316.87.23;
>>> cell: +40-757-768971 (primary phone)
>>> fax +40-21-312.88.04
>>> address@hidden
>>> http://www.rosa.ro
>>>
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