Quadcopter
Introduction
A quadcopter, also known as a quadrotor helicopter, is a multirotor helicopter that is lifted and propelled by four rotors. Quadcopters are classified as rotorcraft, as opposed to fixed-wing aircraft, because their lift is generated by a set of rotors (vertically oriented propellers).
Design and Structure
Quadcopters utilize two pairs of identical fixed pitched propellers; two clockwise (CW) and two counterclockwise (CCW). These use independent variation of the speed of each rotor to achieve control. By changing the speed of each rotor it is possible to specifically generate a desired total thrust; to locate for the centre of thrust both laterally and longitudinally; and to create a desired total torque, or turning force.
Control
Quadcopter flight control can be achieved by altering the rotation rate of one or more rotors to change its torque load. In recent years, mature control algorithms have been developed to tackle the quadcopter's control problem.
Applications
Quadcopters are a useful tool for research and have recently seen a significant surge in interest for a number of applications including military, police work, surveillance, aerial photography, agriculture and drone racing.
History
The development of the quadcopter has been a long process with many setbacks. In the early 1900s, attempts were made at flight using four rotors. Early attempts failed, but later designs succeeded with flight. Today, quadcopters are the most popular type of drone for many recreational and commercial applications.