Anti-offset Performance Improvement Of Wireless Charging System

Wireless power transfer technology,especially the rapidly developed magnetic coupling resonant wireless power transmission technology,has been studied and applied in various fields in recent years,such as electric vehicles,robots,drones and so on.In most of the power supply for mobile power equipment,one of the most common problems of wireless charging is that the positional offset often occurs between the transmitting coil and the receiving coil,causing fluctuations in output power and affecting the stability of wireless charging of devices such as robots and electric vehicles.Therefore,this paper takes the autonomous mobile robot wireless charging application as an example,and aims to improve the charging stability of mobile robots in the effective charging area.The core structure of robot wireless charging is studied,and the coupling coil and compensation topology are analyzed and optimized.The main work of this paper is as follows:(1)Based on the mutual inductance theory,this paper analyzes the basic transmission characteristics of the two-coil wireless power transmission system,the relationship between the quality factor of the coupled coil and the resonant frequency and the parameters of the coil is studied.And the input impedances and resonant capacitances of four basic compensation topologies are compared.(2)For the wireless charging application of robots,the circuit characteristics of robot wireless charging are analyzed.The finite element simulation analysis is used to optimize the basic coupling coil and core structure.Combined with circuit simulation,the transmission current and transmission characteristics of LCL-S and SS basic compensation topology are compared and analyzed.(3)Based on the above analysis,it is found that the uniform distribution of the magnetic field of the transmitting coil is the fundamental way to improve the mutual inductance and transmission performance stability of the wireless power transmission system under the condition of coil offset.Based on the magnetic field distribution law of single-turn square coil,the relationship between the peak position of the single-turn coil magnetic field and its size at different heights is analyzed.The peak-shaving law of the magnetic field is proposed to improve the magnetic field distribution of the original concentrated coil.Additional windings are added inside the original coil to optimize the vertical component uniformity of magnetic field distribution in the effective charging region,and the larger reverse magnetic field outside the coil is weakened by adding additional windings outside the original coil.And both the uniformity of the transmitting coil magnetic field and the coupling coil coupling stability can be fundamentally improved.(4)Based on the experience optimization,a multi-objective optimization model with the magnetic field uniformity and the external reverse magnetic field of the transmitting coil as the objective functions is established.Based on the genetic algorithm multi-objective optimization,the magnetic field distribution,the mutual inductance,self-inductance,system load power and overall efficiency of different optimized coils are compared.Finally,an optimal solution is selected as the design parameter of the transmitting coil,and both the load power and overall efficiency stability of the wireless power transmission system is improved under the condition of coil misalignment.