Replies to This Discussion

Permalink Reply by Ellison Chan on April 9, 2012 at 4:13pm

I wonder if anyone makes a controller that can run 16 motors so that we can build Octor16 heavy lift craft with cheaper motors, and smaller props.

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Permalink Reply by Florian G on April 9, 2012 at 4:50pm

Hello Ellison !

For sure, there is no turnkey solution. As you can see, i have constructed my craft a little bit different than the usual designs - completely manual. If i was after a turnkey solution, i would have maybe bought the german m-copter thing - but i simply liked the arducopter more.

I know Nina (RCTimer) for a bit now and will talk to her. Unfortunately the 16" props will not fit my craft, and i have the feeling that i will need to stay with the props which i have or get ones custom made (there are shops around here which make custom props - but they are  90 USD per piece  - so quite costly..).

Having thought about even more engines before, i guess this may not be the best way as you increase the weigth of the motors more than proportional. It may even be better to construct a quad with e.g. 4x 3 kW engines than to run my configuration. As well, a quad in general has less pipes on the frame and less prop holders, screws etc.

This could be a potential next project after this one with all the experience what to do etc. - to construct a heavy lift quad - but lets stay with one thing at the time- i would even be happy to get this one sorted. - So i will work on it in the next days.

In any case, i will make a level testbed for the copter in the next days and then post results.

Cheers and thanks !

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Permalink Reply by Florian G on April 9, 2012 at 5:01pm

PS: This is how i started in the end. - I got a test motor, mounted different rotor blades, measured the power and did the frame design. - This is how i ended up with these props and engines. I was not really aware that a lower pitch is better - ok - learned for next time. For now, i will try to resolve the stab issue with the setup i have.

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DeveloperPermalink Reply by R_Lefebvre on April 9, 2012 at 5:24pm

I would just use the Octo code, and build the airframe to be able to work with it.  ie: make an Octo with 8 arms, and put two motors on each arm, rotating in the same direction. (not coaxial or counter-rotating)

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Permalink Reply by Ellison Chan on April 9, 2012 at 5:56pm

Huh? Not  co-axial?  So, side-by-side?  There would be no clearance for the props.

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DeveloperPermalink Reply by R_Lefebvre on April 10, 2012 at 8:28am

Well obviously they'd have to be moved for clearance.  So there would be an inner and outer ring or motors, with 2 on each arm.

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Permalink Reply by Ellison Chan on April 10, 2012 at 8:37am

The area covered by the arms would be double that of a coaxial, if the props are to be mounted adjacent to each other.  I feel that coaxial is the most efficient, in terms of spacing.  Sure you loose some power due to turbulence, but space savings over adjacent props is significant.

But, I've always wondered if it's necessary for the props on one arm to be counter-rotating for a Quad or Octo8.

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DeveloperPermalink Reply by R_Lefebvre on April 11, 2012 at 7:52am

Yes, coaxial obviously makes more sense from a physical standpoint.  But I don't think you can do it with the existing code.  You will run into a problem because of the yaw control problem.  If you use a Y-harness to drive two counter-rotating props, how will it control yaw?

If the props were not counter-rotating, then fine.

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Permalink Reply by Sayan Andriyanov on April 10, 2012 at 4:33am

Can you post the screenshot of the gyro graphs, either in static or when you flipping IMU?

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Permalink Reply by Florian G on April 25, 2012 at 12:06pm

Hello Everyone,

i will post screenshots of the octo in a little while once i repeat the tests with the new props after they have arrived.

While still waiting for the propellers to arrive, i have built a much smaller quad, based on the Hobbyking V2 Quad-Board, 9x4,5 Props, 1100 kv motors (350W), 4x Turnigy Plush 30A and a 4s battery 3000mAh, weight is ~ 1300g.

Basically, the result is very similar to the arducopter. I am really getting a bid fed up with this whole copter business.. -

On the Hobbyking 15 USD board, the parameters are set via pots - so i have done the following:

Roll: 20%
Pitch: 10%
Yaw: 15%
I use the Firmware QuadController V 4.7, so i am not sure these settings are rather not PID (i remember that the source says the following:
; Changed Pot control: Roll pot -> Roll/Pitch P-term. Pitch pot -> Roll/Pitch I-term.

Here are the results from the tests.

Most of the time, my quad flips just like in this video.

http://www.youtube.com/watch?v=dVUYavlwG1I

For once, i have managed to take off:

http://www.youtube.com/watch?v=BEMjmB39UrQ

Here the copter is flying in one direction without me touching the sticks.
As said before, i have done the throttle calibration but could not find any way to center sticks etc. - The COG looks ok to me when holding the copter at the sticks.

Does anybody know what is wrong here or how to approach this in a systematic way ?

How can two completely different copters behave the same way ? - Am i stupid ?!?

Maybe these copters would make a better source of heat rather than flying when setting them on fire instead.. - ok - not planning yet, but..

Does anyone have an idea ?

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Permalink Reply by Ellison Chan on April 25, 2012 at 12:26pm

Looks like you're getting the hang of it, in the second video.  Sorry to say, but the common factor is the operator. ;-)

The KK instructions say start at 50% for all gains.  Go up it there's not enough control or decrease if the corrections overshoot.  You have to be in the sticks all the time with the KK, it doesn't really stabilize itself like a controller with accelerometers.  All the gyros will to is counter rotation in roll, pitch and yaw axis.

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Permalink Reply by Florian G on April 25, 2012 at 12:35pm

Hmm - i think i rather just manged to shut the rotors off before killing the camera-lady as it was flying in this direction. Ok - so if i manage to get the flip problem under control, then it should be possible to actually get this thing really flying ?

Hmm - i still have an old APM 2560 in my box here. Maybe i should start with fitting this one on my quad ?!? I have a feeling that controlling a gyro only platform is not really the right thing for me..

Still, do you have an idea what causes the flip ? - Overcompensation ? - Undercompensation ?

Cheers

Florian

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