Replies to This Discussion

Permalink Reply by Dr John Lannigan on February 23, 2012 at 2:52am

Im embarking on a similar project, im surprised there havent been any comments, how far have you managed to get with your project?

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Permalink Reply by Dave on February 23, 2012 at 4:06am

It's nice to seem some one has taken interest in the project! Whats your progress on the project to date? We have currently achieved a rough version of stabilisation using mapping from the gyro's to the servos, but have been held up with technical issues with the motor, as these have been produced in house and the hall effects aren't playing nice. This has limited the project to date.

Other than that we have acheived communication between a GPRS/GSM module and the arduino after much tinkering,

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Permalink Reply by Dr John Lannigan on February 23, 2012 at 10:26am

Hello Dave,

                My stage in the project at the moment is, i am sat looking (lusting) at the parts. I have a coaxial helicopter, with a 620mm rotor diameter, but with my usual approach to projects, i plan each stage meticulously. I intend to severely cut and hack the copter into just a circular UAV. My background is engineering and electronics, and most of the electronics i want to do myself.

Could i PM you direct Dave?

John

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Permalink Reply by Dr John Lannigan on February 25, 2012 at 6:33am

Ive just sent you a PM Dave, feel free to cut and paste it here if you feel it will contribute. Im certainly interested in seeing how you interfaced your modules to the Arduino, and learning more about the problems, youve had with the motors.

John

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DeveloperPermalink Reply by R_Lefebvre on March 1, 2012 at 3:11pm

Dr. Lannigan, can you please fill me in on your current progress?  What heli are you using?  There is an issue already in the "Issues List" to add coaxial support, and I've taken ownership of it.  However, implementation will be difficult because I don't have this airframe.

Can you explain (picture would be best) what the mechanical control mechanism is?  I'm familiar with the little indoor Coaxials.  They are fixed pitch, so they use motor speed for altitude control, and differential motor speed for yaw control.  Then they have 2 servos on the swash plate for elevator and roll.  

But I suspect the bigger machines might have collective pitch on each rotor?

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Permalink Reply by Dr John Lannigan on March 1, 2012 at 5:46pm

Hello Robert,

                   We have 3 models which fly in varying degree's, my fascination began with a coaxial helicopter, and talking with my colleagues at the university.

The project we are working on is a double coaxial UAV, both sets of blades are 100% fixed, but the blade/motor assemblies are mounted into a gymbal or gyro style assemby, both axis are controlled by servo's. The front and the back units downward thrust, can be controlled in any direction, or that is the plan.

From previous experiments, the first lesson we learned was 100% total stability, so our efforts right now are concentrated on just that.

If you are interested, my email for chat is john@jomac.asia

Best regards,

                  John

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DeveloperPermalink Reply by R_Lefebvre on March 1, 2012 at 6:48pm

So, what you are building is a twin-coax tandem heli, sort of similar to these?

http://www.xheli.com/shinook.html

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Permalink Reply by Dr John Lannigan on March 3, 2012 at 1:34am

Broadly speaking yes, its twin and tandem, but thats where it stops. Both sets of blades will be completely fixed, so it wont be cyclic, collective or differential collective pitch, just variable speed. However the motor assemblies will be mounted inside 2 rings which are pivoted 90 degrees apart like a gimbal or cardan suspension 

http://en.wikipedia.org/wiki/Cardan_suspension 

Each ring is controlled by servo, so for 2 motors or thrusters, there will be 4 servos and the direction of the downward thrust of each unit can be controlled seperately. The servos of both units are controlled by a dedicated processor and a giro to keep the craft horizontal in both axis, steering/thrust is accomplished by varying the angle and direction of either/or/both units. The finished craft resembling something like a short and stubby skateboard.

We did consider using 4 of these units instead of two to increase the X Y stability in the air, but decided to go for just 2 eventually.

We are not so bothered about auto pilot functions at the end of the day, but rather user control and stability.

John

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DeveloperPermalink Reply by R_Lefebvre on March 3, 2012 at 3:48am

Ah, what you're building is sort of...

So in any case, do you need support to get the code working for you, or you're going to handle everything yourself?

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Permalink Reply by Dr John Lannigan on March 3, 2012 at 6:21am

Hi Robert,

              The link wouldnt work for me, so i did a quick google. This model shows the rotors on the left and right of the aircraft, where ours will be front and back, weve had some discussions, whether to have 2 thrusters or 4 thrusters or sets of blades. Schools out at the moment on this one, but i feel 4 sets of blades may offer better stability.

I want to keep the electronics modular if possible, so for XY stability, a dedicated micro will be used. Ive never been an avid lover of Atmel, and have very little experience in C programming, im more experienced in using PIC micro's, on the other hand Arduino and Seeeduinos are very cheap, cheap enough to be used as individual modules. And help or interest in programming would be welcomed.

John

DeveloperPermalink Reply by R_Lefebvre on March 3, 2012 at 6:28am

Well, frankly I don't have any time to venture into a totally new controller, and am sticking with the Arducopter system.  So I can't help you much other than to say that if you want to develop your own thing, you are free to base it off our code.

Now, I will say that it sounds like your setup will be quite similar to a traditional tandem helicopter.  I'm actually about to embark on just such a project.  So you could probably use the code I develop.