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## [Paparazzi-devel] Re: AUTO2 throttle management

 From: Christophe De Wagter Subject: [Paparazzi-devel] Re: AUTO2 throttle management Date: Mon, 16 Jun 2008 14:59:57 +0200

Date: Sun, 15 Jun 2008 12:32:47 +0200
Subject: Re: [Paparazzi-devel] Re: AUTO2 throttle management

On 14 jun 2008, at 20:32, Christophe De Wagter wrote:

When the ground speed (temporarily) becomes negative the navigation turns the wrong way as it uses the estimator_hspeed_dir which is defined as atan2 of the GPS speeds. So we added a line to use the heading instead of the ground track for any turn over 60 degrees. (This is a big recommendation as things get increasingly nasty if the plane turns the wrong way in high winds)

Could this always be done - or should one really augment the code to 'detect' windspeed and direction more robustly and 'switch' to this mode automagically ?

Dw

Dirk-Willem,

I believe this can always be done. It does need to compute an extra atan2, so maybe it should be in an ifdef statement for the good-weather mav. The wind estimation does not need to be perfect at all. A rough estimate (say: max wind estimation error is < 80% of your cruise speed) is far better than no estimate at all.

For large differences between the desired and actual ground track (>90/160degrees) and large wind speeds (>20/80% of nominal cruise speed), we steer with the heading. So if you happen to start flying backwards due to gusts for eg, even with a rough wind estimate with errors of 80% of your flight speed, your estimated heading will still point in a far better direction than the ground track. This keeps the vehicle far more stable and close-by for the operator to solve the problem.

1) When the flight speed is larger than the wind speed and turn are small this will not make any difference... (at large errors the desired roll is saturated and at small errors the ground track is used again)
2) When large turns are made (big carrot jumps) with significant wind, the plane will turn into the wind, hereby staying much closer to the desired track.
2) At too high wind speeds, the plane will stably fly backwards.

Christophe