Efficient Power Receiving Coil With Novel Ferrite Core Structure for Capsule Robot

Power receiving coils (PRCs) with ferrite cores are widely used in wireless power transfer (WPT) for capsule robots (CRs) to enhance the power transfer efficiency (PTE). However, due to the large demagnetizing factor, the traditional one-dimensional hollow cylindrical ferrite core has its limitations in volume and performance improvement, which needs to be reconsidered. To this end, we propose a novel PRC equipped with a delicate, lightweight, and more efficient ferrite core structure in this paper. Different from the traditional ferrite core structure, the proposed design composed of distributed ferrite cores and end covers aims to minimize the negative impact of demagnetization on PTE and enhance the magnetic flux concentration. Based on the analysis of the PTE and mutual inductance, influence of the introduced cores on the WPT system is emphasized. The relationship between the change of ferrite core structures and the demagnetizing factors, as well as the effective permeability, is analyzed and simulated. Prototypes of PRCs with different ferrite core configurations are established, tested, and compared to validate the performance enhancement. Experimental results on the power delivered to the load (PDL) and PTE indicate that the proposed design has a volume reduction of 24.4% but performance enhancement of 36% compared with the traditional one with hollow cylindrical ferrite core, thanks to the structure-based demagnetizing factor optimization.