System Design And Motion Analysis Of Mini-type Autonomous Underwater Vehicles

The development of marine oil and gas resources is the reliable guarantee for the national energy security.The offshore equipment,such as offshore drilling platforms,need large daily maintenance,meanwhile the environment is very complex.The manual maintenance face many problems,such as low efficiency,small scope,high danger and high cost.In order to solve the problems mentioned above,this paper has designed a kind of multi-propulsion type small autonomous underwater vehicle for the narrow and complex underwater environment.According to the design philosophy and the practical application scenarios,the design philosophy of the autoumous underwater vehicle had been formulated to be small shape,action flexiblility and high intelligence.The mechanical system design and control system design of the autonomous underwater vehicle had been launched base on the design philosophy and actual needs,including the design of overall layout,the design of the propelling system,the design of computational fluid dynamics simulation of the shape,the design of sensors system and the design of the whole electrical system,then determining the final design by continuous optimization.The final vision of the autonomous underwater vehicle is based on visual and inertial navigation with six propellers.On the base of the final design vision,the motion model had been established finally.The keinematics model and rigid body dynamics model of the autonomous underwater vehicle was deduced firstly,then the resultant external force was analyzed including the controllable thrusts,the additional mass forces,the viscous resistance and the underwater restoring force.Finally,a complete and instantiated hydrodynamics model was completed,which are the most accurate description of the entire vehicle system and the basis of the control model.After the series work of analyzing the actual application scenarios,the inertial measurement and moncular vision messurement are used to ensure the position and the attitude of the aotonomous underwater vehicle.The paper had improved the classical moncular P4 P model to adapt the underwater environment.At the same time,considering the errors accumulation of the inertial measurement and the discretization of the visual measurement,a fusion algorithm based on inertial measurement and visual measurement was designed to solve the two problems by iterative solving process.In order to analyze the practicability and the measurement errors of the two measurement methods,a set of errors analysis device was designed to analyze the errors of inertial measurement,vision measurement and its fusion measurement simultaneously.A large number of underwater experiments were conducted to analyze the errors of various measurement methods.Based on the virtual design and theoretical researches metioned above,the prototype of the first-generation autonomous underwater vehicle was assembled and named SAIL.Based on SAIL prototype,the dynamic model and some control methods are tested by a large number of experiments.It shows that the SAIL autonomous underwater vehicle conforms the characteristics of small shape and action flexiblility.The follow-on work will be carried on the research of high autonomy.