## 3 Design Method of MCRWPT System Based on Simulation
### Ferrite Shielding Structure Design  
Because there are electronic circuits, sensors, and other structures on the RMINS, which are easily affected by electromagnetic fields, it is necessary to introduce the ferrite structure to reduce the magnetic leakage of the system. In this paper, the magnetic shielding structure made of manganese-zinc ferrite is applied to reduce the influence of magnetic leakage caused by the MCRWPT system on the internal environment of the RMINS. The introduction of the magnetic shield structure changes the inductance of the primary winding and the secondary winding. Compared with the MCRWPT system with coil only, the self-inductance and mutual inductance of the MCRWPT system cannot be calculated by existing formulas [27]. Therefore, the self-inductance and mutual inductance of the system are determined by simulation. Four ferrite structures are simulated in ANSYS Maxwell two-dimensional (2D) software to study the magnetic flux leakage characteristics of different magnetic shielding structures. Geometries of 2D simulation models are shown in Figure 5, and the dimensions of simulation models are shown in Table 2.  
The Geometry of the 2D simulation model is symmetric about the \(Z\)-axis, and Figure 5 shows only half of the 2D simulation model. The position and dimensions of coils, line-in, and line-out are all the same in Figure 5a-d. The primary and seco \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Parameters** & **D (mm)** & **Parameters** & **D (mm)** & **Parameters** & **D (mm)** \\ \hline R1 & 20.5 & h2 & 6.5 & b1 & 1 \\ R2 & 26.5 & h3 & 14 & b2 & 1.5 \\ R3 & 32.5 & d1 & 1 & b3 & 1.5 \\ R4 & 35 & d2 & 2.8 & l1 & 18 \\ h1 & 3 & d3 & 1 & l2 & 9.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Dimensions of the simulation model. Figure 5: The geometry of the 2D simulation model. (**a**) Case1: without ferrite shielding. (**b**) Case2: with ring ferrite shielding. (**c**) Case3: with improved pot core ferrite shielding. (**d**) Case4: with special-shaped ferrite shielding. structure, and the distance between the coils is fixed. The wire diameter of the primary coil is 1.2 mm. The coil diameter of the primary coil is 29.5 mm, and the number of turns is 6. The secondary coil is the same as the primary coil. The 2D simulation model of winding structure for MCRWPT is constructed in ANSYS Maxwell, and the circuit is constructed in ANSYS Simplorer to realize co-simulation with ANSYS Maxwell. Excitation frequency of 100 kHz, output power of 15 W, and equivalent load resistance of 100\(\Omega\) are the common parameters of the simulation. Under the condition that the aforementioned common parameters are determined, the magnetic shielding performance of four different winding structures is compared through simulation. Figure 6 illustrates the magnetic flux density distributions on the XZ plane, which shows half of the magnetic flux density distribution and the other half symmetrical about the \(z\)-axis. The maximum limits of the color maps in Figure 6 are identically defined as 12 mT so that the differences in the magnetic flux density distribution between the maps can be compared. The magnetic field distribution shown in Figure 6a shows that the magnetic flux density near the coil is strong. From Figure 6b,c, it can be seen that there are obvious differences in the magnetic field distribution. Due to the directing of the magnetic field by the improved pot core ferrite shielding, the magnetic flux density inside and outside the ferrite structure is significantly reduced. Figure 6d shows the special-shaped ferrite shielding structure to reduce magnetic leakage further. Parameters of coils and PTE via simulation are shown in Table 3. The coil structure with ferrite shielding has a higher PTE than the coil structure without ferrite shielding. The coupling coefficient and PTE from Case1 to Case4 are gradually improved under the same output power, the same coil, and different magnetic shield structures.