Design Of Inductively Coupled Wireless Charging System For Autonomous Underwater Vehicle

Due to the abundance natural of marine resources,the exploitation and utilization of marine resources has been paid more and more attention by people all over the world.As an important tool for ocean surveying,Autonomous Underwater Vehicle(AUV)has been widely used.However,limited energy of the power battery of AUV is the problem that limits its endurance.Compared with the power supply method of traditional plug-in connectors,the wireless power transmission(WPT)technology does not have the contact of metal plug-in and has no risk of short circuit,which improves the safety and reliability of charging.And it is expected to solve the problem of AUV endurance.Therefore,a wireless charging system suitable for AUV is designed in the paper from three aspects,which are electromagnetic coupling mechanism,resonance compensation network and control circuit.The electromagnetic coupling mechanism suitable for AUV is designed.According to the special circular structure of AUV and the effect of seawater mobility,an electromagnetic coupling mechanism based on E-type magnetic core is proposed.The structure and parameters are optimized by the equivalent circuit model,and the coupled structure is analyzed in COMSOL.The simulation results show that the coupling mechanism has the advantages of high coupling coefficient,strong anti-offset ability,and good magnetic field convergence effect.The eddy current loss in seawater is analyzed by Maxwell’s equations,and it is simulated in COMSOL.The compensation network suitable for underwater wireless power transmission(UWPT)system is studied.Compared with the traditional compensation network,the output voltage of the LC/S compensation network has nothing to do with the load resistance and operating frequency,and can maintain a constant output voltage to achieve power supply stability.The topology is modeled by a mutual-inductance circuit model,a steady-state model and a small-signal model.Considering the different electrical characteristics of air and seawater,the influence of seawater on the system is analyzed.Due to the existence of inter-turn capacitance,the operating frequency of the UWPT system should not be too high.The control circuit of lithium battery charging is designed.The bidirectional DC/DC circuit is adopted in the paper,so that the AUV can obtain energy through the charging pile,and can also become an emergency power supply in special cases to supply power to other equipment.The model of bidirectional DC/DC circuit is established.On the basis of PID control,model predictive control is added and a Luenberger observer that can observe the input voltage and load resistance is designed.An experimental platform for an underwater wireless charging system is built.Firstly,the hardware circuit for closed-loop control system is made.The current and voltage are controlled by DSP,and the performance of the closed-loop control circuit is tested.The open-loop and closed-loop experiments of the proposed underwater wireless charging syetem are carried out respectively.The open-loop experiments show that the maximum transmission power of the coupling mechanism can reach more than 120 W,and the efficiency exceeds 95%.When the system has axial misalignment and rotational misalignment,the output voltage variation range of the system does not exceed 15% within the specified range,indicating that the system has a certain anti-disturbance capability;the closed-loop experiments show that the normal charging function can be completed by the wireless charging system designed in the paper,and the efficiency of the closed-loop system can reach more than 90%.When there is axial misalignment and rotational misalignment,the charging current and charging voltage can remain constant.