An unmanned aerial vehicle (UAV) is an aircraft that is equipped with necessary data processing units, sensors, automatic control and communications systems, and is capable of performing autonomously flight missions without a human pilot. Unmanned Rotorcraft Systems provides a complete treatment of the design of fully autonomous miniature rotorcraft UAVs. It is an integration of advanced technologies developed in communications, computing and control areas. In particular, it focuses on: •the systematic hardware construction; •software systems integration; •aerodynamic modeling; and •automatic flight control system design. Emphasis is extended to the cooperative control and flight formation of multiple UAVs, and vision-based ground target tracking and landing on moving platforms. Other issues such as the development of GPSless indoor micro aerial vehicles and vision-based navigation are also highlighted. The proposed monograph aims to explore the research and development of fully functional miniature UAV (unmanned-aerial-vehicle) rotorcraft. This consists of a small-scale basic rotorcraft with all necessary accessories onboard, and a ground station. The unmanned system is an integration of advanced technologies developed in communications, computing and control areas. It is an excellent testing ground for trialing and implementing modern control techniques. It is however a highly challenging process. The aerodynamics of a small-scale rotorcraft such as a hobby helicopter are similar to its full-scale counterpart but has some unique characteristics, such as the utilization of stabilizer bar and higher main/tail rotors rotation speed. Besides these, the strict limitation on payload also increases the difficulty on upgrading a small-scale rotorcraft to a UAV with full capacities. Based on its various characteristics and limitations, a light-weight but effective onboard computer system with corresponding onboard/ground softwa