Oooer, this is not as simple as I had imagined

[MombasaFlash]

I am not exactly new to flying rotor'd aircraft - check out the monster I normally fly on the web link below - but I was surprised how tricky this MK Octo appears to be to fly. I had blithely imagined that it would just lift off and look after itself. Hmm!

Following an initial and foolhardy 'let's just see what happens' attempt I then held one rotor arm to steady it and feel which way it was trying to go. Forward pitch, left roll and left yaw.

Presumably there are parameters within KopterTool that enable one to distribute power more evenly to the eight motors so that it doesn't want to skewer itself into the ground. I had to add loads of trim to all three axes to get it to feel more or less balanced.

But, when it started to lose the horizontal it looked like it was constantly overcompensating as the pitching back and forth got more and more violent.

Totally unflyable in this state.

 

[RTRyder]

I am not exactly new to flying rotor'd aircraft - check out the monster I normally fly on the web link below - but I was surprised how tricky this MK Octo appears to be to fly. I had blithely imagined that it would just lift off and look after itself. Hmm!

Following an initial and foolhardy 'let's just see what happens' attempt I then held one rotor arm to steady it and feel which way it was trying to go. Forward pitch, left roll and left yaw.

Presumably there are parameters within KopterTool that enable one to distribute power more evenly to the eight motors so that it doesn't want to skewer itself into the ground. I had to add loads of trim to all three axes to get it to feel more or less balanced.

But, when it started to lose the horizontal it looked like it was constantly overcompensating as the pitching back and forth got more and more violent.

Totally unflyable in this state.

With the out of box flight controller settings and all the proper calibrations done it should just lift into the air and sit there with little to no control input, if yours isn't doing that there's something else wrong.

Did you do the accelerometer calibration with the MK perfectly level before trying to fly it? Its done by throttle full up and yaw right, only needs to be done once after setup with the MK leveled first and is probably the most critical thing to get right, otherwise it will never fly right and need lots of trim to try and make it stable.

Which reminds me, is this an Octo with 8 straight arms or the Y arms? You shouldn't ever need to add trim to a properly setup MK, the accelerometers take care of that automatically, but with the Y arms on the older Octos they can get out of level pretty easily making it necessary to add trim to try and compensate. Proper fix is to straighten and relevel the arms, the Octo 2 did away with that setup for just that reason.

Ken

 

[MombasaFlash]

...the Octo 2 did away with that setup for just that reason...

Wish I had known that before I bought the Y-arm Octo!

I have done that accelerometer calibration - more than once because I am not actually clear on the two procedures throttle-up/yaw-left and throttle-up/yaw-right. I had understood that the first was to set the level reference and the second to write and save it to Eprom.

When I scroll through the various numbers in green on the centre readout of KopterTool I come to the readout showing current Tx stick positions and all three axes were off-centre by amounts varying between 9 to 15. These numbers can be brought to zero with SubTrim on the Tx.

Would that not have made a difference? Or are the accelerometers supposed to account for and absorb those inaccuracies?

If no trims are supposed to be applied does that include SubTrim?

 

[Pano-Dirk]

I had understood that the first was to set the level reference and the second to write and save it to Eprom.

That's wrong and your problem.
You have to level the copter exactly on the ground and than throttle up and yaw right. The values will be stored now.
Do this only one time to store the ACC zero level.

Than, bevor every start (copter is standing on the ground, but not perfect leveled) throttle up and yaw left to calibrate the accelerometers and store this values. Now you can start the engines and fly.


.

 

[MombasaFlash]

Thank you for that clarification.

I have performed that 'throttle-up/yaw-right' procedure several times on a level tabletop and immediately afterwards, with nothing having been moved, the KopterTool readings for AngleNick & AccNick and the AngleRoll & AccRoll are never the same. The AngleNick is invariably +1/+3 and the AngleRoll usually -5 (Both Acc readouts are '0'.

If it has just been told what is level should they not all read '0'?

The -5 reading for AngleRoll will go towards explaining why it wanted to roll left and required right trim to remove that tendency.

What about those off-centre Tx stick readings in KopterTool - or do they just get left at whatever they might be when all TX trims and sub-trims are zeroed?

 

[MombasaFlash]

Whilst I am testing on the table top the Octo is powered with a 12v battery charger voltage converter, i.e. a regulated supply. Every now and then a get a burst of fast beeps from the MK. It sounds like some sort of warning but what does it signify? I have searched the voluminous and meandering MK website & Wiki but cannot find a page devoted to beeps and their significance.

 

[BorisS]

Hi Mombasaflash,

it sounds like a low voltage warning with 12V. Disable the voltage warning in the MK tools or bring up the voltage to 14v. You are powering directly to the distribution board ?

Boris

(Edit) if its not that tell me than we will go through the other possibilities

 

[BorisS]

1. einzelnes Piepen beim Einschalten und Kalibrieren -> Vollkommen normal, ruig bleiben, durch die Hose atmen! - Peeping after turning on -> Totally normal calm down, breath through you pants.
2. langsames Intervall, mindestens 1 Sek -> Empfangsausfall - Slow interval of peeps -> transmitter signal loss
3. schnelleres Intervall, mindestens 1 Sek -> Akku - faster interval -> Lipo voltage low/warning
4. sehr schnelles Intervall, mindestens 1 Sek -> Kommunikation zu den Reglern gestört - even faster interval -> communication to the BLCs has a problem

 

[MombasaFlash]

Yes, could be. It is while it is being powered by a regulated 12v supply instead of the LiPo.

 

[BorisS]

hmm strange got an email with your last post, but cant find it here.

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Nope. It started doing it yesterday - now and then - with the LiPo attached.

But that is not the main issue.

The main issue is that the stupid insect is completely unflyable. Having redone both initial level (Throttle high/Rudder right) and compass several times the 'flying' result is always the same. Roll and Yaw look as if they are going to behave but the Pitch axis - sorry, Nick (BS) axis - is ridiculous and patently uncontrollable. It appears to be far too slow to react to being off-level and when it does finally correct it way-over-reacts, which of course results in an ever-increaingly violent seesaw.

Of course EVERYBODY is stupid some of the time but I cannot find any physical assembly mistakes i.e. clockwise/anticlockwise assignment for the motors and wiring from motors to BL-Ctrl's (verified in KopterTool with the individual motor test facility). The Configuration Setting is the straightforward default 'Beginners' configuration or the same with GPS and Compass disabled (Altitude is already disabled by default).

The MK Octo ended up on its back several times yesterday - although only one broken prop so far.

I have no idea which numbers should be changed within KopterTool to smarten up the Pitch axis performance - remember, the Roll and Yaw axes appear to be relatively stable, it is only the Pitch axis which is so obviously wrong - but then why should anything have to be changed at all? The word on this forum is that the default 'Beginners' configuration is sufficient to allow the MK to get off the ground and keep itself under control.

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What do the values AngleNick and AngelRoll say before take off and AccNick and AccRoll ?