Design of Coaxial WPT Coils for Linear and Rotational Movement-Based Applications

Two-degree-of-freedom (2-DoF) wireless power transfer (WPT) system is proposed. The WPT provides a high coupling to achieve a constant efficiency against rotational (α) and linear (Δ) movements. The transmitting coil (TX-C) and receiving coil (RX-C) are wound on cylindrical structures. The RX-C can move between three positions, as follows. 1) First position (P
₁
). 2) Second position (P
₂
). 3) Third position 3 (P
₃
). Besides, the RX-C can rotate around its axis between 0° and 360°. The mutual inductance (M) between the coaxial windings is derived and validated by simulation results. Design procedures of the TX-C and RX-C are discussed in detail considering maximizing the power transfer efficiency (PTE). Finally, the WPT coils were fabricated. Experiment results were in good agreement with the calculation and simulation results.