multirotors

Multirotors are a class of rotorcraft that generate lift with multiple rotors mounted on a single frame. The most common configurations are quadrotors (four motors), hexarotors (six), and octocopters (eight); less common are tri- and other multi-rotor designs. They differ from traditional helicopters in using several individually controlled rotors rather than a single main rotor and tail rotor for lift and control.

Lift and control are achieved by varying the speed of each motor. By speeding up or slowing down specific rotors, the aircraft creates excess thrust in certain directions to produce roll, pitch, and yaw moments. The arrangement of motors and propellers, along with electronic speed controllers and a flight controller, provides stability and maneuverability. The energy source is typically a rechargeable battery, most often lithium polymer (LiPo), and power is distributed through a power distribution board to the motors.

Flight controllers process data from onboard sensors such as an inertial measurement unit, barometer, GPS, and magnetometer to stabilize the platform and enable advanced modes. Common capabilities include stabilized flight, altitude hold, position hold, and autonomous waypoint missions or return-to-home functions.

Applications span aerial photography and videography, mapping and surveying, infrastructure inspection, agricultural monitoring, search and rescue, and industrial inspection. Advantages include mechanical simplicity relative to single-rotor helicopters, high maneuverability, and ease of autonomous operation. Limitations involve limited flight time due to battery energy density, sensitivity to wind, safety concerns, and regulatory requirements governing airspace, pilot licensing, and operations. The development of multirotors has been shaped by advances in lightweight materials, compact sensors, and open-source flight-control software.