A quadracopter is a flying machine that operates using four propellers (or rotors). Although designs can vary, there are certain fundamental mechanical and electrical components required. Firstly, the main mechanical components are:
Frame: this is the integral part of the quadracopter as it joins the other components. The frame can come in many designs and sizes yet its main purpose is to ensure that the vibrations coming from the motors are kept at a minimum. Therefore, it is imperative that the frame is made with a strong and rigid material, such as carbon fibre.
Motors: every quadracopterhas four electric motors and these drive the propellers. The motors on a quadracopterare usually out-runners (meaning that the motor is on the outside as opposed to being on the inside).
Propellers: there are four in total, one on each motor. Having four propellers increases the quadracopter’s stability.
Along with the mechanical components a quadracopter also needs various electrical components:
Electronic Speed Control (ESC): this interprets the control information from the controller board and varies the speed and direction in which the quadracopteris moving.
Battery: this powers the quadracopter.
Remote Control: this gives control over the quadracopterfrom the ground, when in flight. quadracopter can now also be controlled via smart-phones or tablets.
Controller board: this is the flight control board. It’s purpose is to ensure stability in flight and does this by passing the information on to the Electronic Speed Control. Controller boards can also be customised to add different functions.
As mentioned, quadracopter use four rotors, with two propellers moving in a different direction to the other two: rotors one and three rotate clockwise while rotors two and four rotate anti-clockwise (the quadracopter would continually spin around if all the propellers moved in the same direction). All four of the propellers work together, at the same time, to create an upward thrust. Varying the thrusts on each one of the propellers controls movement, and this particular design (using four rotors) offers overall increased stability. The weight of the quadracopter is split between the four rotors and therefore, altering the lift and torque of each rotor will control the flight.
A quadracopter has four controllable degrees of freedom and these are: yaw (turns left or right), roll (rolls left or right), pitch (tilts left or right) and altitude. The motion along any of the degrees of freedom is controlled by varying or adjusting the thrusts on each rotor. For example, if you want the quadracopter to roll or pitch, you increase one rotor’s thrust while at the same time decreasing the opposite rotor’s thrust. This must be done simultaneously and at an identical level. This will result in the quadracopter tilting. As a quadracopter tilts, the force vector splits into two components, horizontal and vertical, which will cause two things to occur. The first is that the quadracopter will start to travel opposite the horizontal component and secondly, because the force vector has been split, the vertical component will be smaller. This would cause the quadracopter to fall. To prevent this from happening, increasing the thrust on all four rotors is necessary.