A Wireless Power Transfer Design for Omnidirectional Joint

In this paper, a wireless power transfer (WPT) structure using only a pair of coupling coils is proposed for application at omnidirectional joint. Firstly, based on the theoretical analysis of the stability of the WPT at the joint, all the variables affecting the stable transmission are obtained. Secondly, the trajectory equation of the receiving (Rx) coil relative to the transmitting (Tx) coil during the rotation is determined by the coordinate system transformation theory, and then the mutual inductance of Rx and Tx coils at different pinch angles is obtained. Finally, the optimal values of the above variables, i.e., the final WPT structure, are obtained by minimizing the mutual inductance fluctuation deviation in the available range of 60-180°. By using the proposed transmission structure, a coupler operating is designed and the results show an efficiency fluctuation deviation of only
$\pm6.5\%$
in the 120° operating range.