A quadcopter is a multirotor helicopter that is lifted and propelled by four rotors, as shown in the following photograph. So, what are the important components and their functions? A quadcopter consists of two pairs of identical propellers, where one pair of propellers rotates in a clockwise direction and the other pair rotates in an counter-clockwise direction. These propellers are connected to motors, which are driven by an electronics speed controller. A quadcopter uses independent variations of speed from each rotor to achieve control. By chaining the speed of each rotor, it is possible to specially generate the desired total thrust and desired total torque.

A quadcopter also consists of a microcontroller; a microcontroller is just a small computer based on embedded devices such as Arduino. This microcontroller is connected to different sensors, such as a speedometer and a gyroscope, which provide state information—position, velocity, acceleration, and orientation. An electronic receiver is connected to the microcontroller, which transfers instructions from the remote control to the microcontroller. All these devices are powered by the battery: