| Autonomous Underwater Vehicle(AUV),as a high-end equipment used for exploring the ocean,stands out among various underwater equipment due to its advantages of good maneuverability,strong concealment,and high degree of autonomy.AUVs are widely applied in fields such as marine resource development,oceanographic research,and maritime security.However,the working time and endurance of AUVs are greatly limited by the capacity of their batteries,making energy replenishment a crucial bottleneck that needs to be addressed.Underwater wireless charging technology has emerged as one of the solutions to the AUV battery energy replenishment problem,thanks to its high safety,non-electrical contact,absence of underwater leakage,and good isolation characteristics.To apply wireless charging technology to solve the AUV power supply problem,this thesis focuses on key research issues related to the design of a wireless charging system suitable for AUVs.These issues include the underwater transmission characteristics of wireless charging technology,the design of magnetic coupling devices,the design of resonance compensation networks,the design of power conversion circuits,and the implementation of a wireless charging system prototype.Electromagnetic wireless charging technology utilizes electromagnetic waves to transmit electrical energy.In order to analyze the feasibility of wireless charging technology for AUVs,this thesis starts by examining the energy attenuation issue of wireless charging technology in underwater environments from the perspective of electromagnetic wave transmission.It also analyzes the eddy current losses generated by wireless charging technology in underwater environments,establishes a model for eddy current losses in magnetic coupling devices in underwater environments,and proposes a calculation method for eddy current losses.Considering the AUV’s shape and limited internal space,this thesis proposes an arc-shaped four-coil magnetic coupling device that is resistant to ocean current interference and has minimal electromagnetic interference inside the AUV.The coil structure of the device is optimized.First,based on the requirements of preserving the AUV’s external features,saving internal space,resisting ocean current interference,and minimizing internal electromagnetic interference,the coil type is selected,and a coil structure suitable for AUVs is designed.Then,the magnetic field of the coil structure is analyzed using Ansys Maxwell,and adjustments are made to the coil structure.By employing parameter scanning,the optimal values for each parameter of the coil structure are obtained.Finally,the coil structure is analyzed for misalignment using the parameter scanning method,and the coil structure parameters are adjusted accordingly.To meet the requirements of minimizing reactive power loss in the wireless charging system and ensuring the stability and reliability of energy transmission,compensation networks and power conversion circuits for the magnetic coupling device are designed.Considering that the wireless charging system operates in a seawater environment,this thesis proposes an LCL-S compensation network that offers high safety and resonance stability.The calculation methods for the capacitance and inductance values of the compensation network structure are provided,along with power and efficiency calculations for the resonance compensation network.To meet the requirement of supplying the magnetic coupling device with high-frequency AC current,an inverter circuit using phase-shift control is employed.The working analysis of the phase-shift control is conducted,and the control laws for the conduction angle with respect to the output voltage RMS and THD values are obtained.By utilizing fundamental wave analysis,models for the output voltage and output current of the capacitive filtering circuit are obtained.A wireless charging platform is constructed to verify the correctness of the theoretical analysis and simulations.The measured coupling coefficients of two sets of magnetic coupling devices have a deviation of no more than 0.005 compared to the simulations.The system operates in a resonant state,with an output power of 786 W and a transfer efficiency of 90.5%.Through voltage variation and load variation experiments,the optimal operating conditions are determined,and the system’s fault tolerance range is found to be rotation±15° and axial misalignment greater than 30 mm,meeting the design requirements.Furthermore,the positions of parallel nodes and the pre-misalignment angle of combined magnetic coupling devices are validated,with simulation results consistent with experimental results. |
