Research On Magnetic Induction Coupled Wireless Charging Technology For Autonomous Underwater Vehicle

Autonomous Underwater Vehicle(AUV)is widely utilized in water environment monitoring,mineral exploring and underwater searching.However,it cannot work for a long time due to the limitation of battery capacity.The traditional charging methods include manual charging from salvaging AUV to its carrier and underwater charging through wet plug-in cable,which reduces the flexibility and concealment of AUV and has potential safety hazards.To this end,this thesis applies wireless charging technology to AUV,designing magnetic coupler,analyzing compensation network characteristics and improving misalignment tolerance.In order to reduce the sensitivity of the magnetic coupler to the position offset,the effective coupling law of the magnetic lines under different alignment conditions is studied in depth,and the structure of the magnetic coupler that enhances the capability of the receiver to converge the magnetic lines is proposed.The magnetic circuit model is established to study the variables affecting the coupling coefficient.By analyzing the misalignment tolerance of common magnetic cores,an asymmetric structure magnetic coupler is proposed,which sets redundant parts for core sizes and number of turns.Then the influence of various parameters of magnetic cores on the coupling coefficient is analyzed,and the magnetic core sizes and coil winding methods of the magnetic coupler are iteratively designed with the coupling coefficient and misalignment tolerance as indicators.It is shown from the simulation results that the coupling coefficient is 0.32 and the designed magnetic coupler has a rotation tolerance range of ±14° and an axial offset tolerance range of ±25 mm when the coupling coefficient decreases by 0.1,which satisfies the design index.The resonant state of the circuit is analyzed,and the variation law of the system coupling under the misalignment is studied to ensure the stability of the system when the magnetic coupler is misaligned.The principle analysis and parameter design of the LCC-P compensation network are carried out.Its constant current excitation and constant current output characteristics are analyzed,and the expressions of output power and efficiency are derived and the relationship between multiple independent variables of the system and output power and efficiency is plotted by MATLAB.After that,reasonable parameters are selected to improve the output performance of the system.The PSpice simulation verified that the selected parameters can make the system work in resonance state with an output power of 777 W and an efficiency of 93%,which meets the requirements.To further improve the misalignment tolerance of the system,the relative position of multiple magnetic couplers and the coupling capability under misalignment are studied,and a combined magnetic coupler structure is proposed.The influences of the coils connection mode and the arrangement structure of multiple magnetic couplers on the coupling coefficient are analyzed,and the combination method of the magnetic coupler and the applicable circuit topology are proposed.Then,the parallel nodes are selected and the two magnetic couplers are pre-misaligned to verify the feasibility of power superposition of the two magnetic couplers at different work states.Taking the power and efficiency of the superimposed output as the index,the simulation realizes that the system output performance is better when the pre-misalignment angle is 2°.The platform of wireless charging system is built to verify the correctness of theoretical analysis and simulation.The deviation between the measured coupling coefficients of the two magnetic couplers and the simulated values is no more than 0.005.The system operates in a resonant state with output power of 744 W and transmission efficiency of 90.1%.The optimal working conditions are selected by the variable voltage and load experiments.It is found that the measured system rotation tolerance range is ±15° and the axial offset tolerance range is larger than 30 mm,which satisfies the index.In addition,the position of the parallel node and the pre-misalignment angle of the combined magnetic coupler are verified and the experimental results are consistent with the simulation.