System Control And Experiments On Autonomous Underwater Vehicle With Capabilities Of Landing And Sitting-bottom

A novel small modular low-cost Autonomous Underwater Vehicle with Variable Buoyancy System (AUV-VBS) is designed and developed in the dissertation. AUV-VBS can carry out such assignments as underwater landing, sitting-bottom and long-time observations. It can be used for ocean dynamic environment monitoring and military missions. The dissertation deals with its dynamics modeling, simulations, system controls and experiments. The results of simulations and experiments prove that the theories and methodologies applied are proper and valid. The main contributions are as follows:1) The mechanics and control systems of AUV-VBS are originally designed to achieve functions of long-range navigation, underwater landing and sitting-bottom.2) A six-degree and non-linear dynamic model for AUV-VBS is formulated and validated by simulation. In order to design system controllers, the system is reasonably separated into different subsystems using decoupling and method of small perturbation. The development and verification of the linear simplified model are described. The model can be used in the design of the controller.3) Controller Area Net (CAN) is introduced into the hardware design of AUV-VBS for distributed and hybrid control architecture. The application of layer protocol of CAN Bus is established for controlling AUV-VBS. The overall control system hardware and software are also accomplished. The failure-safe and reliable methods are presented to enhance the capabilities of the control system. The control system can readily be expanded and transplanted.4) Considering the limitations of PID controllers for AUV-VBS, free-model Sliding Mode Fuzzy Controller (SMFC) is proposed. The method of acquiring its suboptimal solution is also presented. Two different control schemes are compared. The performances and merits of SMFC are justified by simulations and experiments.5) The task of sitting-bottom for AUV-VBS is accomplished by suitable landing strategy. Four underwater landing strategies for AUV-VBS are presented and systemically studied by simulation. Evaluation of their performance and applicability are outlined and compared. The sitting-bottom stability ofAUV-VBS is analyzed as well.6) Mass experiments are conducted including laboratory tests without water, pool tests, lake experiments and sea trials. The experimental results are in good agreement with the simulations.