Search Results (332)

Wireless power transfer (WPT) has emerged as a compelling solution for delivering electrical energy without physical connectors, particularly in applications requiring reliability, mobility, or encapsulation. This work presents the modeling, simulation, construction, and experimental validation of an optimized dual-frequency WPT system using magnetically coupled resonant coils. Unlike conventional single-frequency systems, the proposed architecture introduces two independently controlled excitation frequencies applied to distinct transistors, enabling improved resonance behavior and enhanced power delivery across a range of coupling conditions. The design process integrates numerical circuit simulations in PSpice and three-dimensional electromagnetic analysis in ANSYS Maxwell 3D, allowing accurate evaluation of coupling coefficient variation, mutual inductance, and magnetic flux distribution as functions of coil geometry and alignment. A sixth-degree polynomial model was derived to characterize the coupling coefficient as a function of coil separation, supporting predictive tuning. Experimental measurements were carried out using a physical prototype driven by both sinusoidal and rectangular control signals under varying load conditions. Results confirm the simulation findings, showing that specific signal periods (e.g., 8 µs, 18 µs, 20 µs, 22 µs) yield optimal induced voltage values, with strong sensitivity to the coupling coefficient. Moreover, the presence of a real load influenced system performance, underscoring the need for adaptive control strategies. The proposed approach demonstrates that dual-frequency excitation can significantly enhance system robustness and efficiency, paving the way for future implementations of self-adaptive WPT systems in embedded, mobile, or biomedical environments. Full article

A class E inverter has presented wide application prospects in inductive wireless power transfer (WPT) systems due to its significant advantages such as high operation frequency, high power density, and low cost. However, its semiconductor power device is subjected to voltage stress several times higher than the input DC voltage, which inevitably increases the risk of overvoltage failure and limits the system power level. In this manuscript, an inductive WPT system with the pull–push class EF2 inverter is proposed to significantly decrease the voltage stress and ensure soft switching characteristic. The working principle and time-domain waveforms of the pull–push class EF2 inverter are analyzed. Moreover, the differential equations and mathematical model of the resonant parameters are investigated. Compared with the conventional class E inverter, the output power of the proposed inductive WPT system is doubled under the same input voltage. A 100 W system prototype is designed at the operating frequency of 6.78 MHz (according to the A4WP standard) and its experimental results demonstrate the effectiveness and feasibility of the analysis. Full article

This study analyzes cross-band interference and losses in a compact dual-frequency 4-port inductive coupler operating at 6.78 MHz and 13.56 MHz for Magnetic Resonant Wireless Power Transfer (MR-WPT) using an equivalent circuit model fitted to 3D full wave analysis and empirical measurements. The model is first matched to idealized 3D model results to establish baseline parameters and then theoretically analyzed in relation to measured S-parameters to reflect empirical losses. This approach achieves accurate theoretical interpretation, with errors remaining below 5%. The results show consistent transmission coefficients, with the model most closely matching the measurements. Power loss and efficiency comparisons indicate that the model accurately captures deviations, with its performance positioned between the 3D full wave analysis and measured results. Cross-band interference remains below −20 dB, and the maximum measured efficiency reaches 71.18%. Full article

To address the limitations of conventional magnetically coupled resonant wireless power transfer (MCR-WPT) systems in multi-frequency multi-load applications—specifically inadequate load power independence and high complexity inconstant-voltage/constant-current (CV/CC) control—this paper proposes a variable-structure dual-frequency dual-load wireless power transfer system by first establishing its mathematical model and implementing hybrid-frequency modulation for multi-frequency output, then developing an improved T/LCC hybrid resonant topology by deriving parameter design conditions for compensation network reconfiguration under CV/CC requirements, subsequently employing an orthogonal planar solenoid coupling mechanism and frequency-division demodulation to achieve load-independent power regulation across wide load ranges for enhanced stability, and finally constructing a 120 W dual-frequency dual-load prototype to validate the system’s CV/CC characteristics, where simulations and experimental results demonstrate stronger consistency with theoretical predictions. Full article

This study presents the design of an optimal Electric Resonant Coupling Wireless Power Transfer (ER-WPT) coupler intended for multiple-input multiple-output (MIMO) systems. The proposed coupler features a hexagonal-stacked structure optimized for electric field coupling and consists of three transmitters and one receiver. Analysis of the electromagnetic characteristics in this 3-to-1 configuration can be extended to larger arrays. Theoretical analysis based on a practical equivalent circuit (PEC) model, which incorporates loss elements from measurement, is validated through comparison with 3D full-wave simulations and experimental results. Across three representative receiver positions, the summed transmission coefficient of the MISO structure reaches up to 0.90, while the PEC model agrees with measurements within a maximum deviation of 0.09, confirming high accuracy. Furthermore, the proposed structure demonstrates stable resonance characteristics near 6.78 MHz with reduced frequency shifts under different receiver positions. The key contributions of this work are the proposal of an efficient hexagonal-stacked MISO ER-WPT coupler and a validated equivalent circuit modeling approach that reflects real-world losses, providing a reliable basis for future multi-transmitter/multi-receiver Wireless Power Transfer systems. Full article

The modernization of agriculture can help humanity address major challenges such as population growth, climate change, and labor shortages. Semi-autonomous agricultural robots offer clear advantages in automating tasks and improving efficiency. However, in open-field conditions, their autonomy is limited by the size and weight of onboard batteries. Wireless charging is a promising solution to overcome this limitation. This work proposes a methodology for the design, modeling, and experimental validation of a wireless power transfer (WPT) system for battery recharging of agricultural robots. A brief review of WPT technologies is provided, followed by key design considerations, co-simulation, and testing results. The proposed WPT system uses a resonant inductive power transfer topology with series–series (SS) compensation, a high-frequency inverter (85 kHz), and optimized spiral planar coils, enabling medium-range operation under agricultural conditions. The main contribution lies in the first experimental assessment of WPT performance under real agricultural environmental factors such as soil moisture and water presence, combined with electromagnetic safety evaluation and robust component selection for harsh conditions. Results highlight both the potential and limitations of this approach, demonstrating its feasibility and paving the way for future integration with intelligent alignment and adaptive control strategies. Full article

Wireless power transfer (WPT) technology offers a convenient, efficient, and environmentally robust power supply solution for rack-and-pinion modules. For WPT systems in such modules where the transmitter coil is a long rail, increasing the transmitter coil turns to enhance mutual inductance leads to issues like high cost, low efficiency, and installation difficulties. This paper introduces a relay resonator to strengthen system coupling and proposes a three-coil design scheme employing a single-turn long rail as the transmitter coil. The proposed all-detuned LCC-S-S topology exhibits constant output voltage (CV) and zero phase angle (ZPA) input characteristics while accounting for all cross-mutual inductances and coil resistances. The frequency detuning level of the relay resonator critically governs the system’s power transfer efficiency and directly determines the operational mode of the rectifier—either continuous conduction mode (CCM) or discontinuous conduction mode (DCM). To maximize system efficiency, the optimal detuning frequency of the relay coil is selected under CCM operation. Through optimized design of the three-coil parameters, the final prototype achieves an output power of 106.743 W and an efficiency of 90.865% when integrated with a 1200 mm single-turn long-rail transmitter coil. Full article

A cochlear implant (CI) system holds two spiral coils, one external and one implanted. These coils are used to transmit both data and power. A magnet at the center of the coils ensures proper alignment to assure the highest coupling. However, when the recipient needs a magnetic resonance imaging (MRI) scan, this magnet can cause problems due to the high magnetic field of such a scan. Therefore, a new type of implant without magnets would be beneficial and even supersede the current state of the art of hearing implants. To examine the feasibility of magnet-free cochlear implants, this research studies the impact of coil misalignment on the inductive coupling between the coils and thus the power and data transfer. Rather than using time-consuming finite element analysis (FEA), MATLAB is used to examine the impact of lateral, vertical and angular misalignment on the coupling coefficient using derivations of Neumann’s equation. The MATLAB model is verified with FEA software with a median 8% relative error on the coupling coefficient for various misalignments, ensuring that it can be used to study the feasibility of various magnet-free implants and wireless power and data transmission systems in general. In the case of cochlear implants, the results show that by taking patient and technology constraints like skinflap thickness and mechanical design dimensions into account, the mean error can even be reduced to below 5% and magnet-free cochlear implants can be feasible. Full article

This paper presents a hybrid fast charging strategy for static wireless power transfer (WPT) systems that synergistically combines pulsed current and multi-stage current (MCM) modes to enable rapid yet battery-health-conscious electric vehicle (EV) charging, thereby promoting sustainable transportation. The proposed approach employs a memetic algorithm (MA) to dynamically optimize the charging parameters, achieving an optimal balance between speed and battery longevity while maintaining 90.78% system efficiency at the SAE J2954-standard 85 kHz operating frequency. A neural-network-based state of charge (SOC) estimator provides accurate real-time monitoring, complemented by MA-tuned PI control for enhanced resonance stability and adaptive pulsed current–MCM profiles for the optimal energy transfer. Simulations and experimental validation demonstrate faster charging compared to that using the conventional constant current–constant voltage (CC-CV) methods while effectively preserving the battery’s state of health (SOH)—a critical advantage that reduces the environmental impact of frequent battery replacements and minimizes the carbon footprint associated with raw material extraction and battery manufacturing. By addressing both the technical challenges of high-power WPT systems and the ecological imperative of battery preservation, this research bridges the gap between fast charging requirements and sustainable EV adoption, offering a practical solution that aligns with global decarbonization goals through optimized resource utilization and an extended battery service life. Full article

This paper presents a new resonance circuit design method for LCC-LCC wireless power transfer (WPT) systems that incorporate reactive shielding (SH) coils on the receiver (RX) side to suppress the electromagnetic field (EMF). While reactive SH coils are known to reduce leakage magnetic fields, they alter the equivalent inductance of the system, thereby disrupting resonance conditions. To address this, we derive the changes in the equivalent inductance caused by SH coils and propose a method to re-select the series capacitor on both the RX and TX sides. Furthermore, we investigate the adjustment of the required input voltage to maintain output power with the SH coils. The proposed methodology eliminates the need for a series capacitor on the RX side, simplifies the network, and reduces the magnetic leakage field by up to 55.6%, as verified by the simulation and measurement results. This study provides a new pathway toward compact, EMF-conscious and LCC-based WPT systems. Full article

Wireless Power Transfer (WPT) enables efficient, contactless charging for mobile devices by eliminating mechanical connectors and wiring, thereby enhancing user experience and device longevity. However, conventional WPT systems remain prone to performance issues such as coil misalignment, resonance instability, and thermal losses. Addressing these challenges involves designing coil geometries that operate at lower resonant frequencies to strengthen magnetic coupling and decrease resistance. This work introduces a WPT system with a performance-driven coil design aimed at maximizing magnetic coupling and mutual inductance between the transmitting (Tx) and receiving (Rx) coils in mobile devices. Due to the nonlinear behavior of magnetic flux and the high computational cost of simulations, exploring the full design space for coils using ANSYS Maxwell becomes impractical. To address this complexity, a machine learning (ML)-based optimization framework is developed to efficiently navigate the design space. The framework integrates a hybrid sequential neural network and multivariate regression model to optimize coil winding and ferrite core geometry. The optimized structure achieves a mutual inductance of 12.52 $\mu$H with a conventional core, outperforming many existing ML models. Finite element simulations and experimental results validate the robustness of the method, which offers a scalable solution for efficient wireless charging in compact, misalignment-prone environments. Full article

Limited battery life compromises the usability of inspection and operation robots in hazardous environments such as nuclear sites under decommissioning. Both manually replacing the batteries and installing charging bays may be infeasible. Inductive wireless power transfer is a possible solution to deliver power through barriers such as reinforced concrete walls without physical contact. However, when requiring decent power (e.g., 100 W) to be transmitted over longer distances, the exaggerated dimensions of transmitting and receiving coils restrain the integrations with mobile robots. In this paper, a novel retractable design of the coil used in an inductive wireless power charging system is proposed, proving the minor deformation of the winding shape does not affect the transmission efficiency. A prototype with 5× size compression is implemented and tested. It successfully transmits 116.5 W over a distance of 1 m with 68.72% energy efficiency. The principle can be applied to a wide range of mobile platforms with a limited payload area where remote power is needed. Full article

This study presents the development, simulation, and hardware implementation of a 48 V, 1 kW mid-range wireless power transfer (WPT) platform for autonomous guided vehicle (AGV) charging in industrial applications. The system uses an LCC-S compensation topology, selected for its ability to maintain a constant output voltage and deliver high efficiency even under load variations at a typical coil distance of 15 cm. It can also operate at different distances by adjusting the compensator circuit. A proportional–integral (PI) controller is implemented for current regulation, offering a practical, low-cost solution well suited to industrial embedded systems. Compared to advanced control strategies, the PI controller provides sufficient accuracy with minimal computational demand, enabling reliable operation in real-world environments. Current adjustment can be dynamically carried out in response to real-time changes and continuously monitored based on the AGV battery’s state of charge (SOC). Simulation and experimental results validate the system’s performance, achieving over 80% efficiency and demonstrating its feasibility for scalable, robust AGV charging in Industry 4.0 Manufacturing Settings. Full article

This work proposes an ultrathin dual-polarized double-layer Huygens’ meta-atom, capable of generating Huygens’ resonance and achieving nearly 360° phase coverage and high transmission simultaneously. Two metalenses are designed based on the proposed meta-atom. The first is a dual-polarized metalens antenna with excellent directional radiation performance, achieving a peak gain of 30.4 dBi, an aperture efficiency of 47.8%, and a 3 dB bandwidth of 8.4% at 25 GHz. The second is a two-channel focusing metalens, with focusing efficiencies of 52.4% for x-polarization and 48.6% for y-polarization. The proposed meta-atom exhibits excellent transmission performance and offers a more flexible approach for designing transmissive devices, demonstrating significant application potential in the field of microwave communications, wireless power transfer, and imaging. Full article

A model for a fast and reliable evaluation of the impact of MOSFETs’ switching losses in the global performances of a high-frequency wireless power converter is proposed. The frequency domain model for an LCC-S wireless resonant converter is presented. The contribution of MOSFET behavior is counted considering a trapezoidal input voltage in the converter instead of the classic square wave or Pulse Width Modulation wave to take into account MOSFETs’ rise and fall times. These times are evaluated with a simplified first-order circuit able to model the MOSFET behavior during commutations. Two commercial MOSFETs have been integrated in the converter model. The predictions of the proposed approach are compared (for validation) with results coming from Simulink environment, where the converter behavior can be reproduced in a very realistic way. An evaluation of switching losses is presented, and the consequent impact on converter performances is evaluated by comparing the converter output voltage (and output power) predicted with the proposed model and that one is achievable by the converter considering ideal switches. The analysis has been performed considering different values of input voltage and load resistance. This approach can be easily generalized to every resonant converter topology. Full article