quadrotors

A quadrotor, or quadcopter, is a type of unmanned aerial vehicle with four rotors arranged in a cross or square configuration. The vehicle generates lift with four rotors, with two rotating clockwise and two counterclockwise to cancel reaction torques. By varying the speed of individual rotors, a quadrotor can hover, move laterally, and rotate about its vertical axis.

A typical quadrotor consists of a rigid frame with four arms, brushless DC motors, and propellers, plus a flight controller and electronic speed controllers. Sensors such as an inertial measurement unit, barometer, and GPS provide orientation, altitude, and position data. A battery, most commonly LiPo, provides energy.

The flight controller runs control algorithms, often including PID loops, to maintain stable flight and execute commanded motions. Autopilots like ArduPilot or PX4 enable autonomous missions and waypoint navigation. Ground control software enables programming and monitoring.

Applications include aerial photography and videography, inspection of infrastructure, mapping and surveying, agricultural monitoring, and search and rescue. Smaller quadrotors are used indoors with prop guards and smaller batteries; larger units carry payloads such as cameras, sensors, or delivery modules.

Limitations include sensitivity to wind and weather, limited flight time, and reliance on line-of-sight and regulatory requirements. Safety concerns center on rotor injury risk and collision; operators use geofencing, protective guards, and other safety measures.

History: Quadrotor designs emerged in hobbyist and research communities in the early 2000s, with consumer models popularizing around the mid-2010s. Advances in motors, batteries, and lightweight materials have driven ongoing improvements in performance.