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

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

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

Living in the windy Netherlands we encountered this problem quite often. I would even add the following to your observations. 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 ?

Concerning forward speed, adding quite some of "pitch_of_vz" helps a lot (similar to the PITCH_LOOP but keeping the THROTTLE_LOOP active). Furthermore the loiter-cruise-dash trims are very useful to overcome the wind. By adding a pitch down trim, a sufficient auto throttle i_gain will automatically find a higher throttle setting to maintain altitude and the result will be a faster forward speed... finally getting you somewhere. But there is also a ground speed loop if you are interested: #define NAV_GROUND_SPEED_PGAIN. If you use this one in high winds, make sure your throttle_cruise_min is high enough to maintain altitude when flying downwind. Last month we flew at >11m/s wind speeds and our 390 gram 50cm MAV handled the weather very well, while manual flight had became close to impossible as combination of the gusts and visibility issues.


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