With the large-scale application of quadrotor unmanned aerial vehicles (UAVs) in civil fields including aerial surveying and mapping

agricultural plant protection

logistics transportation and power line inspection

flight safety and reliability have become core bottlenecks restricting the high-quality development of the industry. Adopting the methods of literature research and inductive analysis

this paper systematically sorts out research achievements of fault-tolerant design technologies for quadrotor UAVs from 2015 to 2025

and conducts a comprehensive review from three dimensions: technical classification

application in faulty links

and reliability analysis system. It summarizes the core problems existing in current research and prospects future development trends. Studies reveal that existing fault-tolerant technologies have formed two major systems: passive and active fault tolerance. In terms of faulty links

they can be divided into three categories of fault-tolerant schemes targeting sensors

actuators and flight control systems. A complete framework covering evaluation indicators

modeling methods and verification approaches has been established for reliability analysis. Nevertheless

challenges remain such as poor adaptability to low-cost platforms

insufficient robustness under multi-interference environments

and imperfect reliability evaluation systems. The review results of this paper can provide systematic literature support for the reliability optimization of fault-tolerant technologies for quadrotor UAVs

and facilitate the safe promotion of the civil UAV industry.