DJI Naza-H

[Andy Sayle]

hi Folks,

I was just wondering if anyone has tried the DJI Naza-H controller on a helicopter?  I'm looking at controllers to use on a flybarless heli, that can hold a GPS position whilst I fire some shots off a camera.  I'm not interested in 3D performance, just normal flying, and stabilised position hold...

Cheers
Andy

[Zeeflyboy]

Yeah I've had about 6-8 flights with it on my mechanics for the scale build...

Pro

- Easy to set up, nice software
- Manual mode flies just like a normal FBL heli and feels quite locked in.. It's quite a capable stand alone FBL controller
- GPS and Atti mode are ridiculously easy to fly, although you have to get used to not adding collective during forward flight or turns as it maintains altitude for you.
- Automatic position holding on signal loss is nice insurance
- GPS position hold and barometric altitude hold works like a boss, and far better than the stated maximum accuracy in my experience...


Con

- No RTH functionality such as Naza-M... That makes me sad.
- Promised semi-auto landing/take off has yet to arrive... That also makes me sad.
- Tail can be a bit difficult to get right in Atti/GPS Atti, although I think the latest update addressed this... Haven't had the chance to try it out since updating.
- Some variables in the software are extremely poorly explained as to their function and effect so it leaves you to experiment.
- No hard deck function like eg SK720 GPS where you can set a "never below" altitude


Overall it's a fantastic controller for FPV and AP, with the addition of semi-auto landing/take off (supposedly coming) and RTH ("not planned") it would be damn near perfect.

Here is the video from one of my first test flights... It is actually rather windy although you can't really tell until I land where you can see and hear the heli being blown around (a 7kg heli I might add!). This was one of the first flights and you'll notice a little bobbing, in later flights I turned down the autopilot gains and this made for much smoother flight, I think with the 5 blade head it had too much authority at standard settings.

http://youtu.be/jWiuuA_oB9A

[Andy Sayle]

That's awesome information, cheers!

One thing I have noticed whilst reading up on the Naza-H, is that it is recommended to not switch between modes (manual, atti, GPS) during anything other than a stable hover, and that the atti/GPS modes are not a "bail out" feature.  I don't suppose you have tried testing this to see what happens if the flight mode is changed whilst in forward flight, or a banked turn or similar?  I'm intrigued to see why DJI aren't touting the system as having a Bail out feature, unless it cannot handle stabilising the heli from anything other than a Hover....

I am looking at the SK720 system though, seems pretty pricey, but good as far as I can tell...

Cheers!
Andy

[Andy Sayle]

Oh, and, that 5 bladed head looks awesome!  Have you got any more details on it?

Andy

[Zeeflyboy]

Beware the SK720 though - what's not obvious unless you really look hard is that beyond 500m from base all GPS functions switch off.

The big problem with switching from anything less than a stable hover is that at the time you switch it locks the collective stick position as "hover pitch". Above this point you will climb, below it you will descend.

Now imagine if you will that you engage it while in a descent... The Naza will record this stick position (and throttle position for that matter) and it will be the zero reference. You now fly around in one of the auto modes and then decided to switch back into manual - your heli will shoot downwards as the blade pitch reverts to manual control. Not good if you are low down.

The other problem is that the thing can be quite violent in it's levelling. If you are flying fast forward and then enable GPS mode it will stop hard... Potentially hard enough to cause a boom strike. Atti isn't quite so bad as it'll just snap level and continue to slide... GPS however will actively try to stop the heli.

That brings me to another point, use the ESC governor and a flat throttle curve. The Naza will lock current throttle value when you engage auto modes and the heli will feel sluggish because when you try to climb there will be no increase in power to match the increased pitch. With the ESC governor enabled the ESC will automatically add power as required to maintain headspeed... Works much better.

Oh, and final note - unless you set your failsafes with flight throttle set, if you lose signal while in manual mode your heli will crash. Great design feature that one... So make sure you do that and also test on the bench that the motor continues to spin when you switch off. Just obviously be careful that you power up the heli after the tx (although usually the ESC safety start will protect you here) and power it down before the tx.

That head is actually for sale if you want it?

[Andy Sayle]

That seems like a bit of a limitation for the Sk720.  I suppose I wouldn't be flying it that far away from where I am standing though, the idea is that this machine I am planning isn't a long distance FPV machine, more an aerial photography ship. I won't have a requirement to fly miles away from the launch point (other than straight up perhaps!)

Does the Atti/GPS mode work like the Atti/GPS mode on the Naza-M then, where the collective stick is held at 50% for maintaining altitude, and moved up for a climb, and down for a descent?

The failsafe thing sounds like an interesting feature!  So the key thing is to make sure the throttle is not closed during a failsafe event?  Is the ESC throttle signal connected to Naza-M?

Andy

[Zeeflyboy]

Well the SK is limited in altitude as well as distance, but quite high... Think it might be 500m vertically too? It's in the manual somewhere.

The SK doesn't have the same modes as the Naza. It has a sort of Atti equivalent in that you can set it up with active stabilisation and so that it returns to level when you release the sticks, though I don't think it has pitch limits (Naza will only allow max 45 degrees in Atti or GPS Atti).

It then has a GPS position hold mode where you can slowly slew the position around, but it's not for flying around in. There is currently no GPS Atti equivalent where you can fly around in a GPS assisted mode and have it automatically hover when you release the sticks.

Personally IMO - for 3D heli flight/learning to fly, SK720 is the obvious choice. The hard deck and bailout function make that a no brainer. For AP/FPV on a substantially cheaper level than the ACE ONE the Naza-H is a great choice.

Yes the the Naza takes your throttle input and outputs it to the ESC. When engaging auto modes it will lock the current value and you can't change it until you exit into manual mode. In failsafe you can set it to auto Hover, and as long as you were in GPS Atti or Atti it'll be fine, if you were in manual it'll lock the instantaneous zero throttle when you failsafe and down she goes. To work around this you need to make sure when you failsafe that the throttle remains at flight throttle... With the obvious caveat that it requires stricter ground discipline as regards turning the radio on/off in the correct sequence.

[Andy Sayle]

Cool, thanks for the input there, much appreciated.  I've just picked up the Heli for conversion to AP machine now, a lightly used trex 550DFC.  The idea is to move teh abttery mounting rear wards, and add a camera mount to the front to restore the balance.  I'll be running everything else as is (although a stretch to 600 size, with semi sym blades is on the cards).

AllI have to do now, is find somewhere with a Naza-H in stock...

Cheers
Andy