请将下列内容翻译: An unmanned aerial vehicle (UAV), commonly known as a drone, is an aircraft without a human pilot aboard. UAVs are a component of an unmanned aircraft system (UAS), which include a UAV, a ground-based controller, and a system of communications between the two. The flight of UAVs may operate with various degrees of autonomy: either under remote control by a human operator or autonomously by onboard computers. UAV innovations started in the early 1900s and originally focused on providing practice targets for training military personnel. UAV development continued during World War 1, when the Dayton-Wright Airplane Company invented a pilotless aerial torpedo that would explode at a preset time. The UAV development at that time was a target drone for training.