Re: [Paparazzi-devel] Course desired issues

[Gautier Hattenberger]

Hi,

Haiyang, you're absolutely right. The course setpoint is between -pi/2 
and 3*pi/2 while the gps course is between 0 and 2*pi. And it's not a 
problem because in fw_h_ctl.c:174 the difference between the two angles 
is normalized between -pi and pi before being used by the controller.

Daniel, if you want to have a nice display in your plotter, you can add :
if (h_ctl_course_setpoint<0) h_ctl_course_setpoint += 2*M_PI;
after the line 309 in nav.c, but that won't change your navigation.

GH

Haiyang Chao a écrit :
> Just a few details to add for this question. Any comment is welcomed.
>
> In nav.c, line 309,  desired course is calculated as:  
> h_ctl_course_setpoint = M_PI/2.-atan2(y - estimator_y, x - estimator_x);
> The function atan2() can return values between [-pi, pi]. So the 
> desired course is just between [-pi/2,pi*3/2].
>
> But for GPS course, based on my observation, moving north is roughly 0 
> or 2*pi, moving south is around pi, moving east is pi/2, moving west 
> is pi*3/2.
>
> So I guess there must be some difference between real course and 
> desired one unless there are some limitations on estimator_x and 
> estimator_y, which I have not take a detail look in the code. Really 
> busy recently for some hardware problems.
>
> Thanks
> Haiyang
>
> On Thu, Jun 12, 2008 at 10:57 PM, Daniel Morgan 
> <address@hidden 
> <mailto:address@hidden>> wrote:
>
>     I have been talking to poine and anton about this issue for a
>     couple of days and they both concluded it should not be
>     happening... What is happening on this plot is the course
>     desired's range is -90 to 270 and and the acutal is 0 to 360...
>     Now i talked to anton today and he said that he talked to poine
>     and they thought it was a issue with my code being messed up or
>     something.. So on his advice i changed my old paparazzi's folder
>     name and did a completely new cvs... When i did this it did not
>     aleviate the issues. So i thought maybe it was something with my
>     pc or my config, because of this i decided to try out a completely
>     clean system. What i did was i booted of a ubunut 8.04 live cd and
>     installed pprz from this last nights tarball(cvs command was
>     having issues for some reason)and used only the files in the cvs
>     and still got the same issue. The screenshot is from that (you may
>     notice the time is off but don't let that fool ya)... Needless to
>     say i am hoping someone who knows the code better can fix this or
>     at least shed some more light on it...
>
>     here is that screenshot
>     http://img127.imageshack.us/img127/1593/screenshot1vh4.png
>
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