Hydrodynamic Modeling And Control Algorithm Design For An Underwater Helicopter

With the raise of China’s 13th plan of five-year national development, the importance of maritime strategy is further emphasized. Humans have pressing needs for ocean environment research, ocean environment protection and maritime territory defense. But the problems have appeared to be complex due to lack of oxygen, liquid corrosion, and high water pressure in deep water environment. These problems have caused great troubles in direct detection by human beings. The underwater helicopter is a kind of autonomous underwater vehicle, and it is able to dive up and down and keep at one horizontal plane. To achieve high performance in underwater helicopter, controller design is a very important step.This thesis mainly focuses on controller design for an underwater helicopter.The first task is hydrodynamic modeling. Newton’s Law and fluid-related theory is used to build the underwater helicopter equilibrium by separating the model to one master device and several attachments. The gravity center, buoyancy center, gravity, buoyancy, and calculate the mass matrix, added mass matrix, Coriolis centripetal matrix, added Coriolis centripetal matrix are soon calculated in the following step. Then the relationships between inputs and outputs of propellers are analyzed and propeller is calculated with the acknowledgements of propeller axis location. On the other hand, the hydrodynamic parameters of Underwater Helicopter are also considered and we build the state space model of it at last.The second task of this thesis is controller design. The model is simplified and the characteristic of the underwater helicopter is achieved through state space model. The membership function, logic rule database, de-fuzzy function and advanced PID algorithm is determined to complete the fuzzy-PID controller structure. Comparison is also made between different inputs and outputs of fuzzy algorithm such as error, error change rate, proportion, integral, differential amplified gains to choose appropriate value of them. Finally, simulation work is conducted in case of with and without ocean wave disturbances. Simulation results on depth control, navigation, and altitude control show the performances of the closed-loop system is within the requirements.Results of this thesis can be used in controller design for the prototype of the underwater helicopter and the optimization of the structure of underwater helicopter, thus contributing to the development of the oceans.