Review on fault diagnosis of unmanned underwater vehicles.

The ocean surroundings are mostly complex and harsh, which make the faults of the unmanned underwater vehicles (UUVs) difficult to avoid. Fault diagnosis (FD) technologies for UUVs can assist in providing the damage states and are helpful for implementing the targeted fault-tolerant strategies with which further expansion of the losses could be prevented. In the past three decades, a lot of researches on UUV FD have been carried out, from which the findings are classified and analyzed in this paper to present a clear status of the development for the future studies. The task, capability, and component layers of FD are defined based on the specific control structure of the UUVs, where the task layer FD concerns the overall risks of the system operation and task execution, the capability layer FD describes the comprehensive effects on the motion and sensing features with multiple components, and the component layer FD pays attention to the physical information toward specific components. For each layer, the literatures are organized and briefly explained based on the similarities of solutions. Accordingly, some worthwhile issues to be solved are summarized. • The FD literatures of UUVs are reviewed in layers of task, capability, and component concerning the solution similarities. • The overall risks of the system operation and task execution are concerned in the task layer FD. • The comprehensive effects on the motion and sensing characteristics of the components are analyzed in the capability layer. • The comparison-based FD concerning the physical information is contained in the component layer. • Worthwhile issues concerning the adaptive fault threshold, active FD, multi-layer FD, and FD applications are summarized. [ABSTRACT FROM AUTHOR]