Research On Self-Repairing Control System For A Fiber Remotely Operated Underwater Vehicle

Due to its properties of long work duration and wide work range, underwater vehicles are generally used as important tools for human to explore the ocean. They have been widely used in scientific research, commercial and military fields. However, a number of complex issues due to the unknown, hazardous underwater environment have led to several accidents of vehicle loss since the application of underwater vehicles, e.g. the Kaikō ROV(Remotely Operated Vehicle), the Autosub2 AUV(Autonomous Underwater Vehicle), the Nereus HROV(Hybrid ROV). As an emerging country in this field, china also havs experienced more than once loss or accidents of underwater vehicles. These accidents caused huge economic losses and had blocked the development of marine science and technology. Thus, it is particularly prominent to increase the survivability of underwater vehicles.Fiber Remotely Operated Vehicle(FROV) capable of working to the full ocean depth is a novel hybrid underwater vehicle developed by Underwater Engineering Research Institute(UERI) of Shanghai Jiao Tong University. Key technologies of deep ocean underwater vehicles have been researched during the development process of FROV. These technical breakthroughs will equip our nation for the ability to develop full ocean depth working class ROV. The FROV employs twin free-flooded hulls, uses lithium polymer battery as main power source, can operate in two modes(AUV mode and ROV mode) and communicates with the surface control unit via fiber optic communication. Limiting depth and dual mode raise higher requirements for the survivability of FROV.Considering the external demand and the internal demand for survivability research of underwater vehicles, this dissertation presents a Self-Repairing Control System(SRCS) for FROV to achieve a certain survivability level. The main content of the dissertation is described as follows.(1) The survivability of underwater vehicle is discussed and quantitative method is introduced to access survivability. Then, a survival model is derived. Through the analysis of relation between probability indicators, the concept and content of FROV’s Self-Repairing Control System are explained. A model of FROV system is constructed to make it easy for Self-Repairing Control System research. Assessment result is acquired applying the assessment method proposed in this dissertation.(2) Based on the present FROV system, the research focuses on the two basic techniques of SRCS, fault diagnosis and isolation(FDI) and self-repairing strategies.·A model-based hierarchical fault diagnosis system is designed. Compairing with conventional methods, the diagnostic method presented in this dissertation is more efficient and covers the whole system, including different diagnostic modular.·Self-repairing strategies designed for each subsystem according to diagnostic information from the FDI system are presented.(3) According to the survivability assessment result of FROV, FROV system is upgraded referring to the two basic techniques of SRCS. System redundancy is reconfigured. Survivability of FROV is reassessed after upgrade.(4) Finally, tests are conducted for verification of the effectiveness of theories and methods presented in this dissertation.Through this work, the design and application of SRCS for the FROV is preliminary realized and the corresponding survival model is derived. It lays foundation for SRCS application in underwater vehicles, accumulates experiences for further research work and provides a reference for the intelligent control system of underwater vehicles.