Quadcopters: How Do They Work?

It can be quite a sight to see four rotors spinning at 7000 rpm hover two feet in front of your eyes. The stability and as well, agility of these tiny beasts sure makes someone wonder.

Flying Quadcopter


Unlike conventional helicopters, a quadcopter does not require a spinning tail rotor to change direction or maintain a balance of yaw. How so? Quadcopters have four spinning rotors with two spinning opposite to their contrary.



Quadrotorhover.svg

By having this design, two motors are expected to spin clockwise (CW) and the two others counterclockwise (CCW). Thus, this cancels out all yaw and torque which can possibly be found when standing stationary. Simply stated, this setup keeps a quadcopter in a stable hover with no movement across either of it's axis'. Although, how does it manage to move when it needs to?

For a quadcopter to rotate it simply has to increase its power to a pair of CW or CCW motors.
Quadrotoryaw.svg
This image depicted will cause a counter-clockwise rotation.
With the image in view, it will cause the quadcopter to rotate in the counter-clockwise direction. Conversely, the opposite could be done by increasing the power to the CCW motors.

Now how does a quadcopter move left/right, or forward/backward? It does this by applying power to one or a pair of the CW/CCW motors. With this, the motor pushes a certain side of the quadcopter upwards causing the other rotors to catch on and pull the craft in the downward facing direction.

Quadrotorpitch.svg
In this image, the quadcopter will incline towards the bottom of the screen (if viewed in 2D) thus causing a movement, or better known as a pitch, towards the bottom of the screen. To clear up any confusion, this configuration will cause the quadcopter to incline at a half angle, not completely bank.

With the image taken into account as well, two pairs can be increased in power providing one is spinning CCW and the other spinning CW which can tilt the quadcopter as well. By increasing the power of two motors this causes a banking (sometimes known as a tilting motion) towards the intended direction causing it to move that way.

Summary 


See? It really isn't all that complicated. The innovation of the design though, is very impressive. It allows freedom of mobility, maneuverability, and even stability when needed.

A quadcopter flies because of two pairs of motors each spinning CW, and the other pair spinning CCW. They rotate by increasing power to a pair of these motors. To pitch or roll, all a quadcopter has to do is increase the power on one of these four motors or a pair.

Hopefully this article has helped you understand the fundamentals of how a quadcopter flies, and will lead you to become a more skillful and knowledgeable pilot as you progress.

Images by Purpy Pupple (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

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