It flies!

[GoFaster]

Menno -

In QGC, what values in the RC sliders do you see at 0, center and full throttle positions? Both the displayed RC values and the %. I would like to make sure that my scaling and offset are correct.

I'm still ~0.5-0.75kg short of my expected final weight so hopefully hover will be closer to center by then.
No pitch or roll trims needed

Regards,
- Felix

[Kisssys]

This seems to work for me to get the correct hover throttle without a lot of trial and error.

I view a LOG file with a good level hover and take the value LOG_MOT_THROTTLE from the graph. If it's correct it would be around 700.

The formula Corrected Factor Throttle = Current Factor Throttle * Value read from graph / 700. If the value read from the graph was 700 it would make no change. If your hovering low like I was in the pictures then the throttle factor was too high and needed to be reduced by the proportion of 600/700

[GoFaster]

I haven't been able to get out to a field for a while. But in the meantime, I installed the gimbal and along with another battery pack, the copter is at it's full flying weight of 3kg. Hover throttle is much closer to 50%. Thanks for the tips Steve, I will check my logs and adjust the throttle factor.

Couple of videos of first gimbal tests. First video is with wide FoV to try to get some part of the frame in the picture so I can visually get an idea of what the gimbal is doing. The descriptions indicate when I switched on or off PosHold etc.
Comments and analysis welcome!

1280x780 60fps 170 degrees FoV
http://www.youtube.com/watch?v=QB2SF5d3DhQ

1920x1080 30fps 107degrees Fov
http://www.youtube.com/watch?v=NCAiEX34MKQ

- Felix

[kinderkram]

Looking good, but could be much better.
Somehow the gimbal servos react too slow when you start to roll.
You can see the cam move in the same direction at the beginning of the roll .

Hopefully Menno can help you out...

btw: which gimbal do you use and which servos?

[GoFaster]

Thanks for catching that Norbert. Hopefully I can resolve that, along with what looks like a slow roll oscillation in PosHold - which could be a side-effect of incorrect PID tuning.
It's the Flyduino gimbal and Hitec HS-322HD servo.

[joebar.rc]

Hi Felix,

So to seem it's very calm weather and the corrections are small.
The pitch servo seems to do the job good enough, I wonder if the roll servo is countering the multirotor moves?
Just to be sure, if you bank left, will the roll servo keep the gimbal level?

I had to look for the hitec servo, it is an analog servo that is relatively slow @ 19ms /5v.
Although analog servo's are actually better suited for gimbals then digital (no jitter), their slower speed and slower frequency will give normally not give the best results. But... this is always an long journey in multirotor video setup, the long search for the best servo

So, if the gimbal stays level at any angle, make some more flights also in other weather conditions. If it does not stay level (the gimbal) , come back because there are some settings..
It could be that with these servo's and the gimbal this is the best you can do, and to be honest, if you pull it through a software stabilizer very acceptable footage will be the result.

Menno

[GoFaster]

[kinderkram]

How do you guys power your servos?
At 5V the speed is 0.19 sec per 60deg. At 6V it's 0.15 for the Hitec.

Precise digital high speed servos (like Airtronics) usually cost an arm & a leg.
But I've seen digital servos for less then 20$ that offer speeds around or below 0.10 @ 6V

Any recommendations on these? http://bigplanes.nl/contents/en-uk/p556.html

[GoFaster]

I run mine off a 3A HK linear BEC that also powers the RX, because their stall current easily exceeds that of the Recom.
In my opinion, the only advantage of digital servos is precise & stronger position holding and accurate centering at neutral (no double center). Also higher resolution is possible. The downsides are cost and higher overall power draw. I use them on fixed wing models where I need that precision. It's funny to hear 6 servos "singing" as they obsessively sample and reposition around a very tight deadband.
You can have high speed analog servos too, it's just the motor and gearing.

Given that an AP/AV copter is usually flown with small gentle movements, I'm not even sure super high speed servos are necessary. Unless one is using a big reduction drive. In which case it might be better to take the next step and go with continuous rotation steppers and external position encoders.

[joebar.rc]