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Hy, I just found useful to post my idea here.

I've seen videos about automated quadcopters: http://www.ted.com/talks/raffaello_d_andrea_the_astounding_athletic_power_of_quadcopters.html and http://www.ted.com/talks/vijay_kumar_robots_that_fly_and_cooperate.html.

I surfed pages from the companies presenting this research and other information on the internet, but I haven't found why they use quadcopters specifically. I understand, how accelerating, rotating and rolling works in those quadcopters - it's simple, but they claim that quadcopters have minimum number of working parts to fulfill their needs, which I don't agree and I think that tricopters are better in this (duocopters can't rotate horizontally, but tricopters can by inclining and then powering the remaining left or right propeller).

I rode forums, calculated and draw drafts of both tri and quad and found, that tri is much more efficient just in everything than quad with same props and battery when taken in account that best properties has the smallest copter with the largest props so: 3:4 moving parts (no vectored yaw in tri), 9.5:16 size, building Y instead of X construction take far less material 1.5:2.82, lesser maximum power input 3:4, better power efficiency makes longer flight time and tricopters have also improved agility over quadcopters.

The only disadvantage I see is a bit complicated horizontal rotating in tricopter without vectored yaw, which can be problem in man controlled machines but easily solved by simple algorithms in automated machines -> it's not a real disadvantage, just a small work to be done. I was thinking about doing that in my bachelor thesis, but for now I am looking for your opinions, thanks!

EDIT: Maybe the torque is the problem, because on tricopters you can can have all 3 props in 1 direction or 2 in 1 direction and 1 in the opposite and it's symmetrical in neither way, but I'm not sure if this is the main problem...

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    $\begingroup$ As written, this isn't really a question. Whether you should or shouldn't study this for your bachelor thesis is certainly an important question, but it's not something that can be supported factually one way or the other -- it's a matter of opinions. Is there a more practical aspect of the quadcopter-vs-tricopter design that you're having trouble with? $\endgroup$
    – Ian
    Commented Jul 8, 2013 at 1:55
  • $\begingroup$ But I just want to find, what is the problem with tricopters.. maybe someone tells me, what is much better on quadcopters, I don't know. $\endgroup$
    – Salda
    Commented Jul 8, 2013 at 2:58
  • $\begingroup$ I thought quadcopters had two rotors balanced against the other two. How do you do that with a tri-copter? $\endgroup$
    – Guy Sirton
    Commented Jul 8, 2013 at 3:20
  • $\begingroup$ I see there's an additional servo to tilt one of the motors in a typical tri-copter design. That's your answer I guess... shrediquette.wikia.com/wiki/How_does_a_tricopter_work $\endgroup$
    – Guy Sirton
    Commented Jul 8, 2013 at 3:24

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If you want to maximise efficiency, you go with two rotors: a main rotor, and a tail rotor. I.e. a traditional helicopter. With the common CCPM setup (Cyclic Collective Pitch Mixing), you have three servos controlling the main rotor. Together they can tilt it any direction and control the pitch on the blades. As you can imagine, this is mechanically complicated.

The advantage of a quadcopter is that it's very simple; you have no servos. Adjacent arms are counter-rotating to control yaw.

Tricopters have a yaw imbalance that is corrected by dynamically tilting one of the motors.

So, with a tricopter you lose the "no servo" advantage that made people switch from traditional 2-rotor helis to quads.

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  • $\begingroup$ Actually, I'd have to argue that if you want to maximize efficiency you forfeit vertical flight completely and go with a plane. $\endgroup$
    – Octopus
    Commented Oct 13, 2016 at 6:10
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    $\begingroup$ Because the author asked about multirotors, I think it's safe to assume hovering was required. If you want to expand the problem domain beyond multirotors, maybe he should use a blimp - they get the longest flight times. $\endgroup$
    – foobarbecue
    Commented Oct 13, 2016 at 13:12

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