Re: [Paparazzi-devel] Throttle problem with AIRSPEED sensor (Gautier)

[Eduardo lavratti]

Well, i tested new_ctrl in simulator.
the problem continue when in throttle mode.
i put a peace of code to limit the thottle down.

i will test it tomorrow.
the best part in ctr_new is that Integrator reset when changing to MANUAL

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Date: Sat, 16 Jun 2012 14:57:54 +0200
From: address@hidden
To: address@hidden
Subject: Re: [Paparazzi-devel] Throttle problem with AIRSPEED sensor (Gautier)

Hi Edouardo,

I mainly used the log plotter and compared the altitude, vertical speed, attitude and throttle with the desired values. I also looked at which control loops you actually used based on your airframe file and the code.

You can try with new control loop, but it is not really documented yet. I already flew with it but only in throttle mode, not airspeed control. With this control, you can choose the control strategy from the settings (throttle (default), airspeed or ground speed) and set the nominal cruise throttle even in airspeed mode, so this should prevent the problem you had before. One of the drawbacks is that the pitch setpoint coming from the flight plan is not taken into account yet. You also have a lot more gains that you can set, so it is not that easy to tune.

Gautier

Le 14/06/2012 08:13, Eduardo lavratti a écrit :

Gautier ... i am very curious to know how you discovered the problem.
how you debuged ?

are you used log file ploter ?
if yes, what parameter you look ?

about your replay, what are the other control loop available ?
flix sugest the NEW_Control
is this that you like to tell me ?

sorry for my poor english
regards.

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Date: Sun, 10 Jun 2012 20:52:42 +0200
From: address@hidden
To: address@hidden
Subject: Re: [Paparazzi-devel] Throttle problem with AIRSPEED sensor (Gautier)

Hi Edouardo,

Here is what happen during your flight:
According to your airframe file, you are flying with the standard control loop but with the airspeed (actually ground speed) control. Is it what you wanted ? In this mode the pitch is controlled by the vertical speed error (and thus altitude error), while the throttle is controlled only by the air and ground speed error.
When you first engaged AUTO2, the ground/air speed error is close to zero (or even slightly negative). The weakness of the PI controller used in this loop is that you can't set a "cruise throttle" value as initial throttle setpoint. In this situation, the output of the control is 0 throttle, resulting of speed loss which would have increase the integral action if the time spend in AUTO2 had been long enough.
As it was not the case, the second switch to AUTO2 leads to a 0 throttle, but this time increasing. This would have been enough to continue the flight if your plane had not stall due to a combination of pitch up setpoint and high bank angle.
This stall produced an important drop of your air/ground speed, which in the end saves your day as it allows the integrator to fully "charge" itself. For your last attempt to enter AUTO2, the throttle setpoint was close to 100%, resulting of a correct vertical control of your plane.

To summarize: integrators are real shit, but no, you can't just get rid of them like that. The correction I can advise to you is to add a cruise throttle setpoint corresponding to your throttle for cruise flight (somewhere close to sw/airborne/firmwares/fixedwing/guidance/guidance_v.c:351).

Last point: in your radio file, I think it is better to have min and neutral equals for THROTTLE channel, so you don't have -100% display in the GCS.

Good luck for your flights (in a very nice place by the way ;) )

Gautier

Le 10/06/2012 01:17, Eduardo lavratti a écrit :

Gautier, this is the logs that show  a problem when i engage AUTO2.

The flight start after 330 seconds
i tried to engage auto2 for 3 times.

on the 3th time the throttle work fine.

this is my last configuration.
i hae another logs with same problema but the airframe file is different.

regards.

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