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Re: [Paparazzi-devel] Navigation schema ?

From: Famille Chateauvieux-Hellwig
Subject: Re: [Paparazzi-devel] Navigation schema ?
Date: Sun, 15 Jun 2008 17:38:40 +0200
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>  What do you call a real route ?
        Assume the plane flying north (heading 0°). The waypoint you target is 
currently 200m east from the current position (bearing 90°). My PID loop has 
90 - 0 as input and acts on the rudder. the plane will start flying more to 
the right. In the next cycle, I'll have may be heading = 5,  bearing=92, but 
that's not something I can really compute in advance. I just let the PID loop 
regulate it.

>  It does not make a difference only if you are currently on your desired
> track. Usually you don't want only to go somewhere, you want to follow a
> track all the way until the waypoint is reached.
>  You can compute a carrot position as soon as you are able to project the
> current position of your vehicle on the route you want to follow. Easy with
> straight lines and circles ...
> --Pascal

        Ach so !
        Hmmm. That's not always easy.
        Assuming you're close enough to the desired route, and the difference 
heading and bearing is small, you can place the carrot at the intersection 
between the desired route and the "Carrot circle", carrot seconds around the 
plane. Correct ?
Figure 1

        Now If you're far from the route or your current heading is way off the 
bearing to the carrot, you have to change the strategy, and compute a more 
complex desired route (ex: figure 2) ? This will typically be the case just 
when you switch the autopilot on. Can you do this on the AVR ?

Is this the idea ?

Thanks Pascal

Attachment: Carrot-Fig1.jpeg
Description: JPEG image

Attachment: Carrot-Fig2.jpeg
Description: JPEG image

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