According to the International Federation of Robotics any robot that operates autonomously or semi-autonomously to help the human being in his activities (excluding manufacturing) is a service robot. Today the use of drones has grown exponentially for different types of applications, including service robotics. In this thesis, after a brief introduction on the regulation and classification of UAVs, the main sizing criteria of each component of a multirotor will be shown. Starting from the design constraints and a state of the art of the main flight controllers, the hardware and firmware components chosen for the implementation of an autopilot quadcopter under 250 grams will be described.