Posted by Circuits Arena on Sunday, 7 February 2016
Quad Copters Working for Beginners is the artlcle explaining Quad Copters Working for Beginners: Intro to quad copters Quad copters, also known and quad rotors, are one of the most interesting ...
Quad Copters Working for Beginners:
Intro to quad copters
Quad copters, also known and quad rotors, are one of the most
interesting little flying machines ever imagined; yet there's a load of
disperse and almost undecipherable amount of information that comes from
hobbyists' and builder's gut feeling on what seems to be the right
thing to do.
This is my attempt at bringing all that information together in a simple
to understand version for beginners to get designing their own
quadrotors.
How they work
The concept is a flying machine with four motors aligned in a square;
two on opposite sides of the square rotate in one direction and the
other two rotate in the opposite direction.
This four rotor helicopter gives us some interesting properties:
1.- each motor lifts only a quarter of the weight of the heli, so we can potentially use less powerful motors
2.- the rotation or torque of the first pair of motors is canceled by
the rotation of the second pair that goes in the opposite direction. Let
me explain how this works:
On a regular helicopter, you have one big rotor to provide the lifting
power and a little tail rotor; this one counteracts the rotation that
the main big rotor would otherwise pass on to the structure of the
helicopter (making it rotate almost as fast as the propeller)
On a quad rotor, if all motors turned on the same direction the thing
would rotate same as a regular heli without tail rotor; the clever thing
is that since one pair create a torque or rotation on one direction,
the motors turning on the opposite direction create a torque also but on
the opposite direction. These torques tend to cancel out and the
quad copter stays facing the same direction without any rolling around.
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| Quad rotor control; arrow thickness denotes power |
3.- control becomes a matter of which motor gets more power and which one gets less.
Yaw (where the thing is "facing"; using your head, yaw is when turning
left and right) is controlled by turning up the speed of the regular
rotating motors and taking away power from the counter rotating; by
taking away the same amount that you put in on the regular rotors
produces no extra lift (it won't go higher) but since the counter torque
is now less, the quad rotor rotates as explained earlier.
Roll (how tilted to the side it is while still facing the same
direction; using your head, roll is turning it so that your chin is
parallel to the ground) is controlled by increasing speed on one motor
and lowering on the opposite one.
Pitch (how tilted it is; using your head is moving it up and down,
similar to nodding) is controlled the same way as roll, but using the
second set of motors. This may be kinda confusing, but roll and pitch
are determined from where the "front" of the thing is, and in a
quad rotor they are basically interchangeable; but do take note that you
have to decide which way is front and be consistent or your control may
go out of control.
