Silvano Cruciani

Wireless Power Transfer Charging System for AIMDs and Pacemakers

This paper deals with the electric and magnetic field (EMF) safety aspects of a wireless power transfer (WPT) system based on magnetic resonant coupling between two coils. The primary coil is assumed to be on-body, while the secondary coil is assumed to be inside the human body and connected to a battery recharge system of an active implantable medical device such as a pacemaker. This study allows us to identify a good preliminary solution of the WPT coil configuration, compensation capacitor topology, and operational frequency. Demonstrative WPT systems operating at two different frequencies are proposed in order to verify the WPT performances. The EMF safety has been finally assessed by numerical dosimetry studies using anatomically realistic human body models revealing no particular concerns about this application.

EMF Safety and Thermal Aspects in a Pacemaker Equipped With a Wireless Power Transfer System Working at Low Frequency

A wireless power transfer (WPT) system based on magnetic resonant coupling is applied to a pacemaker for recharge its battery. The primary coil is assumed to be on-body, while the secondary coil is in-body. Three different configurations of the secondary coil are hereby investigated placing it inside the titanium case of the pacemaker, on the top surface of the case, or being part of the top surface case. The operational frequency is fixed to be at a relatively low frequency (20 kHz) in order to allow field penetration through the case and to limit the electric and magnetic field safety and thermal increase issues. For each examined configuration, these aspects are investigated by numerical and experimental techniques. The obtained results demonstrate the feasibility of the proposed solutions highlighting their advantages and disadvantages.

Robust LCC compensation in wireless power transfer with variable coupling factor due to coil misalignment

The paper provides an investigation of a possible application of wireless power transfer (WPT) technology to recharge the battery of a short-distance electric vehicle. The performance of the WPT system working at 85 kHz is first investigated by simulations. A robust LCC compensation network suitably tuned is then investigated with the goal to analyze the influence of design parameters on the compensation strategy. Particular attention is addressed to evaluate the deterioration of the WPT system performance due to coil misalignment. Finally, the WPT performances are evaluated demonstrating the feasibility of the proposed WPT technology.

Wireless power transfer system applied to an active implantable medical device

This study deals with the design of a Wireless Power Transfer (WPT) system based on magnetic resonant coupling between two coils, whose secondary is located inside the human body and connected to a battery recharge system of an active implantable medical device (AIMD). A co-simulation tool is developed using circuit and electromagnetic field models to simulate the WPT system. Simulation results are obtained for different positions of the secondary coil and are compared with experiments.

Efficient Low Order Approximation for Surface Impedance Boundary Conditions in Finite-Difference Time-Domain Method

An efficient implementation of low order surface impedance boundary conditions (SIBCs) for the finite-difference time-domain (FDTD) method is presented. The surface impedance function of a lossy medium is approximated with a series of first-order rational functions by using the vector fitting (VF) technique. Thus, the resulting time-domain convolution integrals are efficiently computed using recursive formulas. The numerical error of the surface impedance modeled by the FDTD method is carried out analytically. A sensitivity analysis is performed to determine the minimum number of poles required by the VF technique to achieve good accuracy in modeling regions bounded by several lossy media with near- or far-field source excitations.

Near-Field Reduction in a Wireless Power Transfer System Using LCC Compensation

This paper deals with wireless power transfer technology applied to charge the battery of a short-distance electric vehicle. Different compensation topologies (series–series and LCC compensations) are examined and compared in terms of magnetic field emission and system efficiency. The investigation is carried out by simulations and measurements taking into account the variation of the coupling factor due to possible lateral misalignment of the parallel coils, and of the load conditions that depend on the level of the battery charge.

FDTD Modeling of Impedance Boundary Conditions by Equivalent LTI Circuits

A circuit-based implementation of the Leontovich impedance boundary condition (IBC) is proposed. The surface impedance of a lossy medium is approximated by a series of first-order rational functions using the vector-fitting technique. Thus, an equivalent analogical circuit with lumped linear time-invariant parameters is derived, which is simply analyzed in time domain without performing any convolution. The implementation of the equivalent circuit in the finite-difference time-domain method is detailed for different circuit configurations. Finally, the advantages of the proposed method are presented and compared with those of other numerical procedures for the solution of the IBC in time domain.

Optimum coil configuration of wireless power transfer system in presence of shields

This paper deals with the coil optimization of a wireless power transfer (WPT) system configuration in presence of a shield which is used to mitigate the magnetic field in the environment. The performance of the WPT system and the magnetic field shielding are investigated by simulations and measurements in a WPT demonstrator working at the frequency of automotive applications (f=20-85 kHz). The proposed innovative simulation method allows choosing the optimum shield design of a WPT system in order to assure good electrical performance and compliance with EMC and EMF safety standards.

A novel homogenization procedure to model the skin layers in LF numerical dosimetry.

In this study we focus on the validity of the skin layer currently implemented in up-to-date human-body anatomical models employed in low frequency (LF) numerical dosimetry. Indeed, the several layers of the skin structure, i.e. the stratum corneum (SC), dermis, and epidermis are in these models embedded into a unique fairly-thick (2-3 mm) layer encompassing all of them. While a previous work from the authors showed that for normal-standing (or limb-non-touching) postures a single-layer skin model could conservatively estimate the peak electric field induced in the skin, at least a two-layer skin model comprising of the SC and the remaining skin layers should be used for limb-touching exposure scenarios. This implies notable efforts to discretize the tiny SC layer questioning the validity of current anatomical models. A novel strategy based on the homogenization of the several skin layers has been therefore proposed in order to eliminate the SC from the computational domain opening the doors to future LF magnetic applications even for limb-touching scenarios.

Assessment of magnetic field levels generated by a wireless power transfer (WPT) system at 20 kHz

An investigation is carried out to assess the magnetic field levels produced by the currents flowing in two magnetically coupled coils in air used for wireless power transfer (WPT). The currents are determined by an equivalent circuit, while the magnetic field in the surrounding environment is numerically and analytically calculated. The simulation procedure is validated by comparison with experiments.