Mikrokopter MK Okto with I2C converter **Question**

[Bartman]

Is anyone else flying an MK Oktokopter with the I2c converter and chinese ESC's? I've had mine flying for a week or so and it's got a noticeable wobble that my first MK Okto didn't have. It doesn't seem to be a flight control wobble but it just looks as if the copter is under control 98% of the time and the other 2% it's falling off from level in pitch or roll. It's very subtle but it's there and it actually looks like the camera mount is trying to compensate for it as it's happening.
It's small enough that photography wouldn't be effected but it's showing up as camera shake in video.
Anyone with something to say about this?
Thanks!
Bart

 

[Bartman]

i suppose, in the absence of your opinions on this , i can change the motor timing to High and see what effect that has.

 

[RTRyder]

What are you using for props? Not that it would likely make as much difference as it does with stacked motors like on my Y6 but it's an idea worth trying if you have some different type props on hand which I know you do...

And out of curiosity, what ESCs are you using? I've had issues with some of the cheap Chinese ones doing what you describe for no apparent reason that I can figure out beyond maybe differences in component tolerances or ratings causing them to effectively have different throttle ranges or response timing.

Ken

 

[Bartman]

Xoar 12x5 props and ExceedRC ESC's. I'm working on the problems at hand and will devote the next ten to twelve days on this. After that, a new MK power ring with my BL's transplanted into it will arrive and take over if things are still less than perfect.
My problem is that my original MK Okto 2 flew perfectly. This new Okto might very well fly as well as the components will allow but it isn't nearly as good as my first one.
I'm going to try changing the motor timing first and then try some PID fiddling.

 

[Bartman]

in defense of the I2C converter, while looking at the video I shot this morning, it appears I have the roll and nick settings way too high in the camera tab.
will adjust and try again in the morning along with the change in motor timing.

 

[crcr]

Shawn is having the same issues http://www.multirotorforums.com/sho...8-using-standard-ESC-s-and-Futaba-TX-RX/page3

 

[Bartman]

Shawn and I cried on each others' shoulders (via a landline) yesterday afternoon.
I spoke with RTRyder this morning and he's of the opinion that while the various chinese ESC's appear to have the same hardware, they are not equal in terms of their firmware. In my case, the ExceedRC ESC's are probably not running at the same refresh rate as the Turnigy Plush even though they look identical. He also said that he believes the ESC's being sold by MontoRC.com are a 400 hz refresh rate ESC so they would also play better with the MK FC board for a smoother flying heli.
I think the dips and jitters I'm seeing are the result of a shortage of control info flowing between the FC and ESC's. I don't necessarily think the I2C converter is to blame and it's entirely likely the higher frequency ESC's will perform better. So while my ExceedRC ESC's appear to be useable, there stands the chance that they aren't. If anyone has hard info on ExceedRC ESC's, I'd be interested in hearing it.
Thanks,
Bart

 

[Bartman]

given what Ken had to say this morning, this would appear to be a better choice for an MK with the I2c converter

http://montorc.com/MT30ABEC.aspx

bart

 

[Bartman]

I changed the ESC motor timing to High last night and did a test flight just now. It definitely helped and the nervous tick that the heli had is greatly reduced to almost nothing. But, there's still something of a very subtle jitter so the MK stuff will find it's way onboard as soon as it arrives. The jitter is more in descending flight (which isn't completely stable in any multi-rotor) but since I'm working towards a dedicated video platform, any jitter is too much. We'll see if the MK stuff makes any difference. I may also prop-down to 11" Graupners and see if more heavily loaded props helps at all.

 

[Crash]

I have a set of ExceedRC Proton 30A and gut feeling is that they seem different than Plush or SS.

Here's my understanding of the underlying issue. I'm sure someone else can explain it better.

Part of the problem is the way ESCs currently work. When the flight controller sends a message to change the ESC speed, the ESC logic will 'gradually' increase the speed until it finally reaches it's target. That translates into a slower reaction speed than what the MK ESCs can achieve.

The OP guys came up with a possible way to get around that current problem by using what they call feedforward. When tuned properly, it's like flooring the gas to get to desired speed faster but letting off the gas before it overspeeds.

 

[Bartman]

That could very well be the problem. I doubt it would even be an issue if I were out buzzing around as it flies well and is completely controllable. It just doesn't fly like my original MK which flew like it had its own little highly-competent astronaut (not talking about me) at the controls.
Bart

 

[Droider]

Bart its a much bigger beast and will have totally different flight characteristics.. It will take time to master it and as you say its a video platform so VERY steady away.

Dave