Research On Non-contact Docking System For Autonomous Underwater Vehicles On Cabled Ocean Observatory Networks

The development of ocean observatory network provides a new way to continuously monitor the ocean environment in long term and in real time.It is able to provide plenty of power for undersea electric equipments and transfer observation information to the Internet in real time,thus to realize continuously observation of sea environment.Autonomous underwater vehicles(AUVs)are designed to navigate in water automatically and collect all kinds of observation data in ocean profile dynamically.However,AUVs are powered by batteries,which limits their operation time and cover area.In order to combine the dynamic ocean profile observation with the static ocean bottom observation,this thesis aims to join together ocean observatory network technology,AUV docking technology and non-contact power and data transfer technology.In this way,AUVs can be recharged through ocean observatory network and their observation ability can be largely enhanced.Furthermore,the ocean profile data collected by AUVs can be transfer online to the ocean observatory network,providing 3D ocean observation information for ocean scientists.A cone type docking system is designed and optimised based on the analysis of overall docking process.The design methods of the chief components are studied.The features of the docking station include auto-orienting of the cone due to the ocean current,self-leveling,fixation without any actuators,and underwater camera shooting.It also possesses beacons to be located by AUVs and non-contact power and data transfer interfaces to work together with their counterparts on AUVs.In order to fulfill the docking task,a torpedo-shaped AUV is modified by adding extra docking modules.A non-contact power and data transfer system is specially designed for the docking system and the characteristics of relavant electromagnetic fields and waves in sea water are studied.Non-contact power transfer is achieved by an inductive coupling power transfer(ICPT)system.The coupling coils are specially designed and insulated to be properly installed in the docking system.The principal of ICPT circuit is studied using a computation program based on the mathematical model and the characteristics of different compensation topologies are analyzed and compared.A proper compensated ICPT circuit is developed based on the analysis results.The effects of different design parameters to the performance of the ICPT system in sea water are evaluated using an element analysis(FEA)simulation model.A theoretical method to evaluate,predict and improve system efficiency is developed based on the study of power losses,including copper loss in coils,semiconductor loss in circuits,and eddy current loss in transmission media.A propagation path analysis method is proposed to study the available distances of high frequency electromagnetic waves in sea water.Electromagnetic field analysis of the antenna are carried out and consequently verified by relevant experiments to verify the feasibility of using Wi-Fi devices in sea water.Based on the performance evaluation and application of the device,the network architecture in the docking system is constructed.In order to make sure the AUV navigate to the docking station precisely in the present of ocean current,a predefined path following navigation method and a two-loops control method are proposed based on the analysis of characteristics of different position sensers.A cross-track error based composited controller is developed for the outer control loop.The dynamic model of the AUV in the present of lateral current is built.The availability of homing method in different current conditions is demonstrated by the dynamic simulation model.In addition,a light tracking system is added to the AUV to guarantee successful docking in the final stage of homing.Finally,a prototype docking system is built and tested in laboratory environment and water pool.The functions of the non-contact battery charging system,the wireless data transfer system,the latching structure,the camera system,the voltage and current monitor system,and the upper computer program are demonstrated.Successful light tracking and cone entering are realized.The theoretical analysis of the non-contact power and data transfer system and homing control methods are verified through the experiments.