APM autopilot / RTL wind compensation.

[kogashuko]

So to date I have had two incidents where two different quads had RTL issues with wind. The first one the quad sailed off and I have not been able to find it. I simply watched my house get further and further away until I lost radio link. The second time the same thing began to happen but I had the presence of mind to snap it back into stabilize mode which let me pilot it back. However, I had to fly it close to the water, under some tree limbs, and then back up to my desired landing spot. I normally do this in altitude hold mode to allow for finer control of altitude. Since I was in stabilize mode I went just a little to close to the water and touched it. The result of that crash was a destroyed gopro and a couple of ESCs since saltwater pretty much destroys electronic stuff. I was able to salvage the motors, APM, and video transmitter. My first fly off was a total loss including a gopro.

So, my question is what setting do I have to change to allow the thing do tilt further to buck the wind? I would think this would happen by default since the APM should clearly see that the quad is not heading in the direction of home...

[Marty McFly]

maybe you need to increase the RTH speed up to counter act the wind,also it could be a Sat/HDOP problem,Marty, :scotland:

[kogashuko]

I will give that a try on the rebuild!

[Biffa]

You can get an air speed sensor for the APM which it will use to maintain it';s speed in a headwind.

[Hands0n]

You may need to adjust some parameters to boost the flight speed while in RTL (and other auto) modes.

Culled from the Arducopter wiki pages ...



Other navigation settings also have an influence over RTL mode:
WPNAV_ACCEL
WPNAV_LOITER_SPEED
WPNAV_SPEED_DN
WPNAV_SPEED_UP

Waypoint Horizontal Speed Target (WPNAV_SPEED)
Defines the speed in cm/s which the aircraft will attempt to maintain horizontally during a WP mission

Range: 0 2000
Increment: 50
Units: cm/s

Waypoint Acceleration (WPNAV_ACCEL)
Defines the horizontal acceleration in cm/s/s used during missions

Range: 50 500
Increment: 10
Units: cm/s/s

[kogashuko]

Thank you, I figured there was a simple fix but I wasnt quite sure what to search for.

[Biffa]

Surely those settings just adjust the speed between way points and do not have anything to do with compensating for a strong headwind?

[Marty McFly]

if it does not have enough speed to compensate for head winds it will just be blowen away,Marty and the borrowed doggie, :scotland:

[Hands0n]

Surely those settings just adjust the speed between way points and do not have anything to do with compensating for a strong headwind?

As I read the wiki those settings define the speed that the APM will attempt to reach when flying between waypoints, and in RTL the "home" is a waypoint for the RTL routine.  It isn';t ideal, but might be worth setting to a higher speed than the default if going to fly in windy conditions. 

[kogashuko]

You can get an air speed sensor for the APM which it will use to maintain it';s speed in a headwind.

Well I guess it makes sense if the board primarily determines speed by how much the craft tilts and then determines navigation by the GPS. I think I remember this being the case now when I was looking into putting an APM on a bixler without an air speed sensor. In that case the quad will tilt to a certain angle and just get blown away all the while still attempting to RTL.

[Biffa]

Without a proper airspeed sensor the board just relies on GPS data (I believe) to calculate it';s speed during way point navigation or RTL situations.

I should have got one myself really, still maybe on the next rebuild.

[Oakie]

http://www.ebay.co.uk/itm/301226569862?_trksid=p2060778.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

One of these Biffa?

Paul

[Biffa]

http://www.ebay.co.uk/itm/301226569862?_trksid=p2060778.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

One of these Biffa?

Paul

Yup one of those, some come with tubing that one doesn';t.

[kogashuko]

How much use would that be on a quad with four propellers flying around on it?

[Oakie]

Airspeed is a measurement of the plane';s speed relative to the air around it. The pitot (pronounced pee-toe) static tube system is an ingenious device used by airplanes and boats for measuring forward speed. The device is really a differential pressure gauge and was invented by Henri Pitot in 1732.

so the 2 tubes one in air flow the other static air.

http://science.howstuffworks.com/transport/flight/modern/question597.htm

[kilby]

It';s used in real aircraft ranging from supersonic jets to combat helicopters,  it';s suitable for the purpose

[kogashuko]

So you just extend the tube out to somewhere that it will not get propwash?

[kogashuko]

Ah, ok I remember where I read about the air speed sensor... it was when I was looking on putting a crius in a bixler.

http://www.multi-rotor.co.uk/index.php?topic=5647.0

There is another link inside of the thread that tells you how the APM or Crius determines speed without one. It is based on nav_pitch.

http://diydrones.com/forum/topics/airspeed-sensor-do-i-really-need-one?xg_source=activity

It also looks really hard to use airspeed sensor with the prop wash.