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Re: [Paparazzi-devel] Constant ground speed and altitude control


From: Rokas Adiklis
Subject: Re: [Paparazzi-devel] Constant ground speed and altitude control
Date: Wed, 23 Jun 2010 15:23:48 +0300

Dear Gautier,

I tried to use pitch="auto" with throttle="0.7". What I've got in the air was constant throttle (as expected), but altitude control was not working - it was rising up at about 1-2m/s (when it reached waypoint, it was WAY over desired altitude). What am I missing?

Thanks.
Rokas

On Mon, Jun 21, 2010 at 11:48 PM, Gautier Hattenberger <address@hidden> wrote:
Hello,

If you set the picth attribute to auto in your flight plan you will activate an alternate control loop call "AUTO_PITCH" were the throttle is more or less constant and the altitude tracking is done with the pitch.
There is a very basic ground speed loop in sw/airborne/nav.c:210 that I have never really used (Pascal did in simulation...) or an other one in fw_v_ctl.c that seems to use a airspeed sensor to prevent stalling.

Gautier

Le 21/06/2010 22:26, Rokas Adiklis a écrit :
Good evening,

I'm trying to figure out two things:
  1. how to set up constant ground speed?
  2. how to make it decrease altitude with pitch and without decreasing throttle?
The reasons for this is that I need to fly reasonably far distance (~8 km) forth and back, while having pretty high wind (~9m/s). While at wide throttle (70%) and Auto 1 mode it does pretty well, but in Auto 2 it wobles around like a snake and does not go straight. I have noticed, that it usually flies 15-25 meters above target altitude (it has non-symetrical wing with rather good lift). When this happens, it holds lower throttle to decrease altitude, but then there is not enough thrust to keep it stable and it starts to fight with incoming wind. When I command to shift desired altitude +30 meters, it instantly adds throttle, climbs these ~30m and decreases throttle to a low value again (as it is too high again). When I changed the navigation mode to constant throttle, it was rathe stable against wind, however the altitude was not controlled, and the plane was constantly going up.

What shoud I do, to configure minimal throttle and (pitch-based) altitude control at the same time? I've google out something about "pitch_of_vz" parameter. Could it help it given situation?

Also, is it possible to set constant ground speed? I'm trying to searched the archives, but just don't seem to be able to find the solution (or don't realize to have found one).

Thanks in advance for any help or hint!

Rokas
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