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Aug 11, 2010, 06:31 PM
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Need help with Fixed Wing VTOL control/autopilot system

Hello, I have a concept for a fixed wing VTOL propulsion system and I could use some help with ideas for designing the control system(s). Below are a top and side view of the general layout. I'm still dreaming up the airframe, so I apologize for the generic drawing. I wanted to do something big and cool.

The design is basically two fixed EDFs that would be embedded in the wings with a center rear mounted gas turbine that tilts to provide both vertical and horizontal thrust. The two EDFS would provide both roll and pitch control while the rear gas turbine would just provide a bunch of thrust (and maybe yaw if needed)

What I'm trying to figure out is do I need a full blown autopilot to control this, or can I get away with just using gyros/mixers.

Here are my thoughts/concerns:
-keep it simple, pilot in the loop
-I'd like to maintain a stable hover (like in videos when guys walk up and push the hovering vehicle and it just returns to level)
-If using only gyros, is there a way to mix the EDF controls such that they do provide both roll and pitch.
-As the rear engine tilts and the wings begin to generate lift the EDFs will need to maintain a level platform and eventually shut-off all together as the vehicle becomes a traditional horizontal r/c aircraft.

Thank you in advance for any comments or ideas that anyone has. If there is something I'm overlooking or if anything didn't make sense I'll try to clarify.

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Aug 11, 2010, 07:04 PM
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it will depend on what controller you have
Aug 12, 2010, 04:38 PM
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When you say controller do you mean transmitter (Futaba...) or controller like MicroPilot/Kestrel? I have an old Futaba T6EXAP on my shelf, but will probably need to upgrade. What I'm trying to figure out is if I will need a controller like MicroPilot/Kestrel.
Aug 12, 2010, 05:34 PM
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v22chap's Avatar
I'd like to maintain a stable hover (like in videos when guys walk up and push the hovering vehicle and it just returns to level)
This statement of requirements says it all .... you need an auto pilot with GPS capabilites as no gyro will keep it level nor will they return it to where it started from !!!
They only will dampen the action of the axis so that the pilot has a little more time to control it

This turbine / fan system has been done before .... well the other guys ended up using heli tail rotors to control the roll , pitch and yaw .... and yes even though it is a smooth running turbine ... it still has a bundle of torque

I can't right of find the other project and don't have time (headed to IRCHA) but do a youtube search of the "rig " by eddie weeks .

Good luck and keep us posted
Aug 12, 2010, 05:41 PM
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GPS alone won't have any info about attitude. You need a full blown INS platform with GPS update. Or some form of horizon sensing if attitude is your only concern. And a microprocessor that can make use of that info and convert it in the appropriate control inputs.
Aug 12, 2010, 05:55 PM
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v22chap's Avatar
Auto pilot with GPS capabilites I believe I said ?? We are both on the same page here I think ,,, just different termonolgy I believe.
Some thing like the mikrokotper auto pilot or the ardu pilot or atto pilot so do him just fine .
Aug 12, 2010, 06:11 PM
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Oh, right, that was a brain fart on my side. I read GPS and my mind blanked out the "auto pilot" part. Sorry about that
Aug 12, 2010, 06:30 PM
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v22chap's Avatar
been there done that and have many tee shirts to prove it :O
Aug 12, 2010, 07:05 PM
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Excellent, thank you for all your help. I will start looking into autopilot setups and see what I can find. I'll look into the ones v22chap mentioned, however if anyone has experience with a particular controller that they would like to recommend I'm all ears.

Once I start the build (probably going to still be awhile) I'll start a new thread to update.
Aug 12, 2010, 08:00 PM
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v22chap's Avatar
Go to the UAV section , just above the VTOL section here on rcgroups ... this is where I have been getting my reading for the last yr or so ... haven't jumped in yet ... but it is really cool and I am thinking about it .

This mikrokopter Hexakopter with their control unit is really neat ... scroll down the page and watch the video ,, he lays the tx down and pushes the unit all over the place and it comes back to within a few feet of its starting point !!!!!

Good luck
Aug 13, 2010, 10:19 AM
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You might want to consider AttoPilot. I've watched the development of this on the Parallax forum and it looks pretty solid. I did one myself just to see if I could so I can attest to the architecture.


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