Small UAV: Product, Autonomous Flight and Future

Small unmanned aerial vehicles (which are less than 1m in size and less than 4kg in weight) can be divided into three categories according to their flight modes: fixed wing, rotor and flapping wing based on bionic design. Each flight type has its unique advantages and disadvantages. For example, fixed-wing aircraft can fly quickly and efficiently, but usually can't hover. Rotorcraft can hover and has good maneuverability, but its energy efficiency is usually low. Bionic flapping-wing aircraft provides an alternative paradigm, which can be scaled down (fixed wing and rotor can't), but at present it has great challenges in aerodynamics, mechanical design and control.

Flapping-wing aircraft

The energy consumption during flying is extremely high. Small unmanned aerial vehicles mainly use lithium batteries and motors as power sources. The smaller the aircraft, the worse the energy utilization efficiency. The main reason is that the electromagnetic power density of small-sized motor will decrease, the area of paddle will become smaller, the transmission efficiency will decrease after adding reduction gear, and the smaller Reynolds number will also bring greater viscous loss. The figure below shows the weight and flight time of the current small UAV products. The fixed-wing flight time is relatively long, but the short flight time is one of the bottleneck problems (ranging from several minutes to dozens of minutes) that affect the use of rotary-wing UAVs. However, multi-rotor UAV has gained rapid popularity in recent years due to its advantages of hovering, good maneuverability, simple structure and low cost. At present, it is also more suitable for development as an aerial robot platform. In this paper, some mainstream and mature multi-rotor platforms are listed and compared, and the future development of autonomous flight of UAV is discussed.