A Folded Coil Design for Cubic Wireless Charging Space Frames With Even Magnetic Flux Density Distribution

This article presents a novel coil design method for cubic wireless charging space frames to achieve even magnetic flux density distribution inside. The method is demonstrated in two hardware designs. The new coil design (i.e., Design-2) is upgraded from an elementary design (i.e., Design-1), which is inherited from the conventional Helmholtz coil to fit the cubic structure, by folding the terminal wires to the neighboring edges to form "L" shapes. Consequently, the magnetic flux density inside the space frame in Design-2 becomes stronger and more evenly distributed than that of Design-1. This important feature of the proposed design methodology is validated by theoretical calculations based on Biot-Savart law, simulation results based on finite-element method (FEM), and practical measurements based on a three-dimensional (3-D) printed prototype. The proposed coil design method could be potentially applied to cubic space frames for many 3-D wireless charging applications ranging from portable devices to underwater unmanned vehicles. The structure can form a 3-D wireless charging chamber that can in principle be scaled up to different sizes.