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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 15:29:56 +0300

Dear Todd,

sorry, I have actually messed up with terminology - while saying constant ground speed, actually I had in mind minimal ground speed.

About setting pitch neutral, I did it a little bit different - I trimmed the rudder a little bit too down, so it would always tend to pitch nose down. However, it didn't add too much effect, and it would continue to fly +30 meters above desired altitude. Next time I'll be at the field, I will try your suggestion, maybe it would do better. Thanks for advice.


On Tue, Jun 22, 2010 at 2:42 AM, Todd Sandercock <address@hidden> wrote:
Hi Rokas.

1. Setting constant ground speed is very dangerous. Firstly going down wind the aircraft would have to fly very slow (maybe even impossibly slow) relative to the airflow and secondly you might find the aircraft flying full throttle for continuous periods flying into wind.

2. Adding to Gautier's comments, It sounds like you haven't set the the pitch neutral of the aircraft properly. All you need to do is make the paparazzi think that the nose is pitched up higher therefore in reality the nose will be driven down adding speed and making it easier to keep the altitude under control.


From: Rokas Adiklis <address@hidden>
To: address@hidden
Sent: Tue, 22 June, 2010 5:56:41 AM
Subject: [Paparazzi-devel] Constant ground speed and altitude control

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!



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