
From:  Gautier Hattenberger 
Subject:  Re: [Paparazzidevel] Proposed update in the fixedwing pitch control loop 
Date:  Sun, 25 Sep 2016 22:51:47 +0200 
Useragent:  Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 
Hi, I agree with Hector on the fact that the math is wrong when only using pitch rate. On the other hand, the error is most of the time small and only sensible at high bank angle. Also, correctly computing the derivative of theta means that we will add the error and noise of the angle estimates in the error signal (and so in the command). As long as we don't do aerobatics, not sure it really make sense to use the full equation. About adding the possibility to choose the current code or using the measured pitch rate, Michal said that the gains needs to be adapted with the P factor. So I guess the idea is to change the structure of control loop from u = P * (err + D * d_err) to u = P * err + D * d_err There is already a discussion opened in https://github.com/paparazzi/paparazzi/pull/1658 but not really closed. I'm also pointing that in the "old" control, it is not the numerical derivative of theta that is used (as in the "new" control) but the difference between the last two values (division by DT is missing). It means that you can't simply replace d_err by q (or a more complete equation). You also need to compensate by the control time step. Gautier Le 18/09/2016 à 09:06, Hector Garcia de
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