In recent years, wind turbines have shown a maximization trend. However, most of the wind turbine blades operate in areas with a relatively poor natural environment. The stability, safety, and reliability of blade operation are facing many challenges. Therefore, it is of great significance to monitor the structural health of wind turbine blades to avoid the failure of wind turbine outages and reduce maintenance costs. This paper reviews the commonly observed types of damage and damage detection methods of wind turbine blades. First of all, a comprehensive summary of the common embryonic damage, leading edge erosion, micro-cracking, fiber defects, and coating defects damage. Secondly, three fault diagnosis methods of wind turbine blades, including nondestructive testing (NDT), supervisory control and data acquisition (SCADA), and vibration signal-based fault diagnosis, are introduced. The working principles, advantages, disadvantages, and development status of nondestructive testing methods are analyzed and summarized. Finally, the future development trend of wind turbine blade detection and diagnosis technology is discussed. This paper can guide the use of technical means in the actual detection of wind turbine blades. In addition, the research prospect of fault diagnosis technology can be understood.

The attitude maneuver dynamics and control strategy for a fuel-filled spacecraft with uncertain inertia and external disturbances are studied. The mathematical model of a three-axis stabilized spacecraft is established based on the law of conservation of momentum, and the liquid fuel inside the partially-filled fuel tank is represented by an equivalent two-mode spring-mass model. The adaptive sliding mode control law is designed for this kind of underactuated system, and the Lyapunov stability analysis guarantees that all system trajectories reach and remain on the sliding surface. Then, the multiple mode input shapers are used to suppress the sloshing of the fluid fuel. The numerical results show good performance and effectiveness of the control strategy.

The problem of robust, angular velocity-free control and fault-tolerant control for liquid-filled flexible spacecraft attitude maneuver subject to unknown external disturbances is investigated. Moreover, state variables measurement uncertainty and actuator failures are explored. The liquid sloshing effect of spacecraft fuel is equivalent to a two-order spring-mass model, and the flexible attachments are equivalent to the Euler–Bernoulli beams. The external disturbance, multiple failures of the output actuator, and the coupled interference caused by liquid sloshing and vibrations of flexible attachments are distinguished as continuous and percussive disturbances. First, a fault-tolerant control method against the percussive disturbances is proposed, and the robustness performance and characteristics of this method are analyzed. Then, both continuous and percussive disturbances are considered to propose a new fault-tolerant control method based on a nonlinear disturbance observer, which is used to estimate the integrated disturbance. The Lyapunov stability theory proves that the proposed control strategy can make the state variables converge to a small neighborhood of the origin in finite time. Finally, the numerical simulation is used to verify the effectiveness and robustness of the proposed control strategy.