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[Paparazzi-devel] Re: Eagletree altimeter and airspeed sensor

From: Christophe De Wagter
Subject: [Paparazzi-devel] Re: Eagletree altimeter and airspeed sensor
Date: Sun, 13 Sep 2009 20:18:24 +0200

From: address@hidden
To: address@hidden
Date: Sat, 12 Sep 2009 10:08:02 -0700
Subject: RE: [Paparazzi-devel] Eagletree altimeter and airspeed sensor.
The paparazzi team includes you :)  sooooo get writing.  Actually airspeed control coupled with pitch control is an interesting problem.  My theory is a lot of the simple control logic that paparazzi uses would have to change to really make the airspeed/altitude system work.


Hi AJ,

We played quite a lot with airspeed and the conclusion is indeed that it is not as easy as e.g. attitude control. As the paparazzi manual says: the v_ctrl is the hardest to tune, so adding interfering loops does not make it easier.

-Pitch from airspeed is quite easy to tune, but interacts a lot with the altitude loop if the altitude loop is also high gain. (interesting for landings)
-Throttle from airspeed gives the same. It is difficult to tune high performance airspeed control and high performance pitch at the same time. (interesting for formation flights) 

Basically you should choose to either have very performance altitude control and slower speed control or the other way around.

-The results become very nice however when total energy control is used: 
Throttle from missing total energy and pitch from differential energy (pitch up when Ekin>Epot). When good sensors are used (mainly to find the time derivative) there is much less loop interaction.

(for the full story see "total energy from lambrechts"

Problem is: how to add this to paparazzi without adding a whole lot of extra IFDEFs? Any ideas?



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