How do I just sit and spin without wandering off? (GPS&ATTI)

[AltaFlix]

Hi all!

I'm circling when I want to be spinning! Can I adjust something to fix this?

I hope you are all enjoying your Phantom's as much as I am! I have recently employed the use of the new GoPro 2-axis gimbal from UAVProducts, a DU-BRO prop balancer and MOONGEL and have been able acquire some really nice aerial media! There's still one minor thing I have not been able to get under my control and that is the circling behavior when I want to be spinning. Maybe "spinning" is the wrong word - I want to be able to go straight up - albeit WAY up - stop and slowly rotate 360 degrees, then come down. When I attempt to rotate - and it does not matter if I'm in GPS or ATTI - it moves in a circle. It's not a huge circle, but it definitely ends up being very far from the point from which I started it the rotation, once complete.

Is this a balance issue?

Thanks in advance for the help!

-Chris

 

[Sac D]

Re: How do I just sit and spin without wandering off? (GPS&A

It's likely that it's up high enough that the wind is catching it. I've learned that the air can be absolutely still at ground level, but up at 100 or 200 feet it's a different story.
Have you been able to spin at 10 or 20 feet up? My Phantom seems to drift backwards sometimes, I think it may be due to the GPS trying to compensate for the added weight of the camera up front. But it also does it in ATTI as well.

 

[pwright]

Re: How do I just sit and spin without wandering off? (GPS&A

It might well be a balance issue with both a GoPro and a gimbal. All that weight is on one end. Haven't noticed a problem with mine but I only have the GoPro.

I've wondered about trying to balance with small weights on the rear so that the Phantom is balanced fore/aft. Seems like that would make it easier to maintain position and you wouldn't have two motors always working harder to keep the front up.

 

[Sac D]

Re: How do I just sit and spin without wandering off? (GPS&A

I've wondered about trying to balance with small weights on the rear so that the Phantom is balanced fore/aft. Seems like that would make it easier to maintain position and you wouldn't have two motors always working harder to keep the front up.

Hmmm... good point! I guess it will all even out once I have acquired the rest of the stuff I want to attach... such as the Holux M-241 data logger, and the BluTrack tracker which I just found out about today. (Thanks to Adam!) Those two should even out the weight. Then the only axis I would ever have to consider adjusting would be for vertical.

I don't know if any of this is helpful to AltaFlix however, that may involve a more technical issue, unrelated to the payload.

 

[AltaFlix]

Re: How do I just sit and spin without wandering off? (GPS&A

I'll try adding some weights...guess I need to get a scale now! Thanks for the reply's!

 

[Gizmo3000]

Re: How do I just sit and spin without wandering off? (GPS&A

couldn't hurt to run advanced calibration as well.
but does makes sense that if the phantom is really front-heavy it would be more inclined to tilt (and move) forward.
does the mount allow you to mount it a bit further back?

 

[tanasit]

Re: How do I just sit and spin without wandering off? (GPS&A

I don't think adding weight will fix the issue. The CG is not a problem for the Phantom because the system will compensate for the difference. I did tied another battery pack to one leg and it still hovered level and stayed in place.
Pirouette on the spot is not an easy task and most of the time you will also lose the altitude. Some pilot always add throttle while giving a yaw input and some TX even have the auto feature to do just that.
Perhaps more practice on the calm day will help.

 

[pwright]

Re: How do I just sit and spin without wandering off? (GPS&A

Tanasit - this isn't a traditional chopper with a cyclic, collective and anti-torque pedals. The Phantom NAZA controller handles all the nuances of flight control including adjusting for imbalance as you said but that is mostly about maintaining a level flight and holding position. The NAZA knows where the supposed CG of the Phantom and that is what it will try to rotate about. If the real CG is significantly offset from the theoretical the Phantom will orbit around a position that is offset in the opposite direction of the imbalance.

With no input on the right stick the OP should be able to spin his Phantom in place around it's CG with only adjustments to the left stick. Assuming no significant wind. If it won't do that then an Adv. Cal. as Gizmo suggested might help.

 

[tanasit]

Re: How do I just sit and spin without wandering off? (GPS&A

Tanasit - this isn't a traditional chopper with a cyclic, collective and anti-torque pedals. The Phantom NAZA controller handles all the nuances of flight control including adjusting for imbalance as you said but that is mostly about maintaining a level flight and holding position. The NAZA knows where the supposed CG of the Phantom and that is what it will try to rotate about. If the real CG is significantly offset from the theoretical the Phantom will orbit around a position that is offset in the opposite direction of the imbalance.

With no input on the right stick the OP should be able to spin his Phantom in place around it's CG with only adjustments to the left stick. Assuming no significant wind. If it won't do that then an Adv. Cal. as Gizmo suggested might help.

IMU relies on the inertia measurement units which include: the accelerometer, gyro scope, barometric altimeter plus the help from the GPS and compass for the positioning in space. The measurements are based on the assumed installation CG in all axes. When accessories are added to the Phantom, the CG may shift but the NAZA will be able to handle unless the shift is out of range i.e. can't even take off. The GPS can only confine the Phantom within certain square feet (4-6?). The yaw input in this case denied the compass or heading.

Now what if the weight is added while the Phantom is hovering? NAZA is still able to keep the Phantom level like it doesn't care where is the "new" real CG. All of the magic self control above is not designed to keep the Phantom pirouette on spot. And yes the offset CG may make the matter worse but perhaps not to a point where one can adjust so that the perfect pirouette can be achieved.

My first rc helicopter 35 years ago (German made Cricket) came with mechanical yaw compensator, which I never mastered! Then came the dual fly wheel gyro that break every time you crash and the solid state ones took over. Nowadays we got it too easy.

 

[auck]

Re: How do I just sit and spin without wandering off? (GPS&A

Nowadays we got it too easy.

no complaints from me

 

[pwright]

Re: How do I just sit and spin without wandering off? (GPS&A

Nowadays we got it too easy.

So true. Ain't technology grand.