Unmanned aerial vehicles (UAVs) have drawn significant interests worldwide due to the huge potential of being applied to both civilian and military areas. Autonomy is considered as one of the most challenging issues in the research and design process of UAVs. Firstly, classifications and system architectures of UAVs are presented in this paper. Secondly, since sense and avoid (S&A), fault detection and diagnosis (FDD) and fault-tolerant control (FTC), and cooperative control are regarded as the key techniques for autonomous control of UAVs, the principles of the three key techniques are described; and the latest development on the integration of the three key techniques, known as fault-tolerant cooperative control (FTCC), is also presented. Then, the key UAV technique applications to aerial refueling and forest resources and fire monitoring and detection are introduced. Finally, technical challenges and future directions are discussed.

UAVs  /  autonomous control  /  sense and avoid  /  fault detection and diagnosis and fault-tolerant control  /  cooperative control  /  faulttolerant cooperative control