Research On Improving The Misalignment Performance Of The Magnetic Coupler In Wireless Charging Systems For Unmanned Aerial Vehicle

In recent years,unmanned aerial vehicles(UAVs)have been applied on various occasions,such as remote sensing monitoring,plant protection operations,and inspections,due to their low cost,high flexibility,solid real-time performance,and a high degree of automation.However,due to factors such as battery capacity,payload,and acquisition cost,the range and duration of rotorcraft are usually short,which seriously restricts the further development of rotorcraft.Although an efficient power replenishment method has effectively solved the above problem,the existing plug-in charging has drawbacks such as being susceptible to adverse weather conditions,consuming a large number of labor costs,and charging interface leakage and wear,making it challenging to meet the autonomous charging needs of rotor drones under different operating conditions.Wireless power transfer technology overcomes the problems of plug-in charging and achieves safe,efficient,and reliable power replenishment for rotor drones through nonphysical contact.However,in practical applications,the wireless charging system(WCS)of UAVs inevitably faces the problem of difficult alignment between the transmitter and receiver.Therefore,from the perspective of structural design and performance optimization of magnetic coupling mechanisms,this paper proposes a high-performance magnetic coupling mechanism that considers the configuration characteristics and load limitations of UAVs through theoretical analysis,simulation,and experimental verification.Specifically,this paper conducted the following research work:First,explain the circuit structure and working principle of wireless charging systems,and analyze the performance of various compensation topologies.In response to the demand for improving the misalignment performance of wireless charging systems,a comparative analysis is conducted on the system characteristics of the SS(Series Series,SS)type compensation topology in resonant states and various non-resonant states.Careful consideration is given to selecting the SS-type compensation topology in the primary side detuning and the secondary side resonance state as the compensation topology for wireless charging systems.Derive the relationship between output current/voltage and load resistance,mutual inductance value,and overall system parameter design.Use simulation results to verify its rationality,providing support for subsequent magnetic coupling mechanism design and optimization.Second,due to the large number of parameters to be optimized for the magnetic coupler and the severe impact of each parameter on its operating performance,using specific or modeling methods to optimize the magnetic coupling mechanism is often time-consuming and labor-intensive.Multiple singleobjective optimization algorithms were compared and analyzed using numerical experimental methods.The Balanced Particle Swarm Optimization(BPSO)algorithm with high algorithm convergence and good global search performance was selected.Then,based on optimizing the main parameters of the stacked magnetic coupling mechanism using the BPSO algorithm,its misalignment performance was improved,solving the problems of the high workforce and time consumption in manual optimization methods.Third,the multi-objective optimization algorithm is used to optimize the magnetic coupling mechanism to solve the shortcomings of the single-objective optimization method,such as the need for a rich experience in determining the fitness function.Based on the comparison of numerical experimental results with various multi-objective optimization algorithms,NSGA-II(Non dominated Sorting Genetic Algorithm II)algorithm was selected to participate in the multi-objective optimization of magnetic coupling mechanisms.Based on considering lightweight design,the orthogonal experimental method is used to determine the magnetic coupling mechanism.Then,the NSGA-II algorithm optimizes the magnetic coupler’s parameters,synergistically improving the magnetic coupler’s misalignment performance and reducing the optimization process’ s dependence on experience.Finally,a prototype of a WCS for UAV was built using non-resonant SS compensation topology and NSGA-II algorithm to optimize the magnetic coupler,and hardware circuit design was completed according to system parameter requirements.Software algorithms were written to ensure the integrity of system testing.When the offset distance along the x/y axis does not exceed 140 mm,or the offset distance in the oblique direction does not exceed 108 mm,a constant current output of 6 A and a constant voltage output of 25.2 V was achieved.The experimental results verify that the magnetic coupler of the WCS designed in this paper has a solid anti-misalignment ability,ensuring that the UAVs can autonomously charge when landing in a wide area of the charging platform in outdoor environments without human intervention.