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Nowadays inductive powering has become a widely spread technique in existing and emerging implanted medical devices (IMD). The geometry of coils couple plays a key role in the design, optimization and evaluation of a biomedical inductive powering unit (IPU). We have proposed a relatively fast method for an execution of these procedures, which is based on a mutual induction calculation using GPU parallel computing. Generally, our approach is to calculate mutual inductance as a function of uncontrolled (axial distance, lateral distance, inclination) and controlled (coils radii, turns numbers, distance between turns) geometric parameters of a coil couple. Calculated geometric functions in its turn are used in the design and optimization procedure to evaluate an IPU performance (e.g., load power). Achieved time gain of the GPU calculations in comparison with the host CPU computing is up to 80 for sequential summation and up to 8 for parallel computing. Also, it is shown that precision of our method is comparable to the precision of existing electromagnetic field solvers, and at the same time, computation time is substantially less (time gain is about 7 . . . 8 for 2D case and about 100 and higher for 3D case). Additionally, we have verified our method experimentally and shown that results of the calculations are accurate enough to predict real IPU performance. Finally, we have given an example of an IPU design optimization using geometric functions calculated with the help of the proposed method.

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Coils misalignments restrain the wider implementation of inductive powering of implantable medical devices. The misalignment problem can be overcome with the help of the coils geometry optimization. Coil couple design implies simultaneous adjustment of the several parameters (coils radii, turns numbers, and pitch). Thus, it is desirable to have the means for computer-aided design of the system. An algorithm for the coil couple design is devised. The key feature of the algorithm is the use of predefined maximum and minimum acceptable values of the load power as a performance metric. The algorithm gives the geometry of the coil which ensures that the inductive powering unit provides the given range of the load power for the given range of the misalignments. A formal method is proposed for the calculation of the initial coils characteristics and consequent adjustment of the transmitting coil external radius, transmitting coil turns number, coils internal radii (simultaneously), and receiving coil turns number. The software implementing the proposed algorithm was developed. Eight design runs were performed in order to evaluate the algorithm performance in various conditions, including different power ranges (10 W, 100 mW, and 300 µW), operating frequencies (0.2 MHz, 1 MHz, 6.78 MHz, and 13.56 MHz), and possible implementations (ventricular assist devices, cochlear implants, and spinal cord stimulators). It was proved that the power drop as low as 10% of the mean load power can be ensured for the lateral misalignments up to the receiving coil external radius. The low-power inductive powering unit was constructed and tested. The experimental results confirm the numerical modeling. INDEX TERMS Electromagnetic coupling, inductive charging, inductive power transmission, implants.

One of the main concerns for transcutaneous energy transfer via inductive coupling is misalignments of coils, especially in the case of mechanical circulatory support systems, when coils placed on a chest wall or an abdomen. We proposed a space-frequency approach to this problem. It is possible to find values of so called splitting frequency by expression which incorporate the value of coupling coefficient. Given that coupling coefficient depends on the system geometry, it allows one to determine the optimal operating frequency for the specified relative position of the coils. Numerical calculations of transcutaneous energy transfer parameters show the capability of the proposed method. It was found that the operation at splitting frequency provided more stable output with respect to changes in a system geometry. The output power of the proposed system changes for not more than 5% for a distance in a range of 5-25 mm. At the same time, the output power of the system which operates at fixed resonant frequency changes for about 40%. Similar results were obtained for lateral displacements in a range of 0-20 mm.