Replies to This Discussion

Permalink Reply by Ground Loop on January 5, 2011 at 9:01am

Am I the only one trying Hold mode? :)

 

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Permalink Reply by Magellan on January 5, 2011 at 11:09am

I've used GPS Hold a bit. I also have the Magnetometer. I would describe the operation as being less precise that I can control it myself. I have seen it jump around a bit; but I haven't had to do a great deal of intervention. I've seen it perform as advertised, with an accuracy of about 3-5 meters. Altitude accuracy tends to be about 1-2 meters.

"One other odd bit: The RED Arduino LED (GPS lock) does not track the Blue LED on the GPS directly.  I have to engage GPS Hold mode to see the RED LED reflect the GPS status.  Normal?"

I have seen this as well.

Different from you, mine has been holding position as advertised. I am disappointed with the accuracy of the position hold, and would like to find a way to improve it. I would like to see the center of the craft stay in a 1-1.5 meter box. Maybe my expectations are too high.

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Permalink Reply by Ground Loop on January 5, 2011 at 11:23am

Thanks Magellan!

 

I would be thrilled with 3-5 meters of hold.   I suspect something in my system isn't working correctly, but I'm not sure what it might be.  The manual control is flawless, and the GPS is locked and received by Ardu.

 

I'm not getting anything close to 5 meters, and haven't let it "run far away" to see if it eventually stops or comes back.  I'll get to a field today with more meters of airspace and see how far it wants to run before it decides to "hold".  Altitude accuracy is worse than 10m.

 

It's certainly making a mode change, because the feel of both stick is very different.  It just wants to 'pull' in some random direction, like there's a Trim problem.

 

Do you frequently have to take it Out/In GPS hold to reset the origin?

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Permalink Reply by Christof Schmid on January 5, 2011 at 12:16pm

Do you have a magneto connected?

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Permalink Reply by Sebastian Gralla on January 5, 2011 at 1:50pm

did you tune your GPS PID values?

did you set the correct geo correction factor?

did you set the correct declination for your flight area?

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Permalink Reply by Ground Loop on January 5, 2011 at 12:18pm

I have no magnetometer. (Yaw is controlled manually, but has been pretty stable in hover)
You?

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Permalink Reply by Knuckles904 on January 5, 2011 at 12:39pm

If memory serves me correctly, magneto is necessary for gps hold. Otherwise, the quad will not know which direction it is pointing.

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Permalink Reply by Ground Loop on January 5, 2011 at 12:58pm

Doh!  Really?  I did not know that.

It does make sense, but I figured I would just hold Yaw manually and let it stabilize altitude and position.  Hmm..

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Permalink Reply by Sebastian Gralla on January 5, 2011 at 1:50pm

yes, you need magneto...

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Permalink Reply by Taylor Cox on January 5, 2011 at 2:24pm

The reason why you need a magneto is because unlike on a plane, where this is always forward motion, a quad is stationary when hovering so the GPS needs the magnetometer to find it's heading.

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Permalink Reply by Ground Loop on January 5, 2011 at 2:31pm

Roger that.  I'll get one on order.  Is there a strong preference between the DIY and Sparkfun+VoltageAdapter combo?

 

Might be good to put that requirement on the wiki next to the GPS Hold instructions.

Or maybe I'm just denser than the average DIY'er. :)  Not the first time.

 

Thanks for the help.

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DeveloperPermalink Reply by Randy on January 5, 2011 at 8:40pm

Ground Loop,

     Yes, we will update the wiki!  You're actually not the first person to make that mistake.

 

     As for DIY vs SParkfun mag.  Either works but the thing I like about the DIY Drones one is that it can be mounted directly onto the Oilpan and also it works at either 5V or 3.3V (if you set the jumper correctly) so no need for a level shifter.  Instructions for both are on the wiki.

 

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