Six Degrees of Freedom Wireless Power Transfer by Crossed Dipole Transmitting Coils and the Minimum Number of Receiving Coils

Inductive wireless power transfer (WPT) to a moving receiver (Rx) can be evaluated by the Rx displacements and rotations relative to the transmitter (Tx). Three degrees of freedom (3 DoF) in displacements and 3 DoF in rotations of the Rx can be defined. This research has designed a system with the highest DoF (6 DoF). The Tx has crossed dipole coils, and the Rx has the minimum number of coils for 3-D omnidirectional WPT. Unlike most studies on 3-D omnidirectional WPT, the Tx and Rx have flat structures in this study, which can be an essential advantage in transferring power to moving devices. Because of variable magnetic coupling, the compensation circuit has the LCC-S topology. With a 2.4 cm transfer distance, power transfer efficiency is higher than 80% in the Rx displacements, and the maximum transfer power reaches about 700 watts. The efficiency remains high in the Rx rotations around the z-axis (yaw rotations) with output power changes. The efficiency is also acceptable in the Rx rotations around the x and y axes (roll and pitch rotations). Therefore, the proposed WPT system provides 6 DoF with the flat Tx and Rx structures.