Transmitter Coil Research Articles

Analysis and Design of Constant Current/Constant Voltage Output of Array Multitransmitter Inductive Power Transfer System

ABSTRACTWireless power transfer has been widely used in unmanned aerial vehicle (UAV) charging due to its convenient and flexible noncontact charging characteristics. The working area of the uncoupler inductive power transfer (IPT) system is limited, and ZVS is easily lost in phase‐shift modulation. This paper proposes a method for constant current (CC) /constant voltage (CV) output in an array multitransmitter IPT system based on HFP modulation in a wide working area. The HFP modulation method easily realizes the current phase synchronization of multiple transmitter coils, and the size can be adjusted. At the same time, an efficient optimization model for a multitransmitter IPT system based on HFP modulation is proposed. Finally, an experimental platform for the array multitransmitter IPT system is built to verify the effectiveness of the CC/CV output realization method and the efficiency optimization model for the multitransmitter IPT system. The maximum errors in charging current and voltage are less than 2.52% and 2.1%, respectively, and the peak efficiency of the IPT system reaches 87.3%.

Triangulated Transmitter Coils With High Design Freedom for Free-Positioning and Omnidirectional Wireless Power Transfer System

Triangulated Transmitter Coils With High Design Freedom for Free-Positioning and Omnidirectional Wireless Power Transfer System

Comparison of Different Modulation Control Strategies for Wireless Power Transfer System

When designing a wireless power transfer system, overall system efficiency is one of the key parameters. The efficiency depends on several parameters, which also includes control modulation, used for excitation of the transmitter coil. However, how much the modulation technique impacts the efficiency is studied rarely. In this paper, we compare the three most popular control modulation techniques for transmitter voltage of a wireless power transfer system. First, the theory behind the methods is presented by highlighting the difference between them and their implementation. The methods are implemented, together with a linear PI control scheme, to evaluate the efficiency and performance of each of the methods. Finally, the practical tests were performed, under different output power levels, in order to evaluate the practical performance of each modulation strategy further.

Design of dual transmitter and single receiver coil to improve misalignment performance in inductive wireless power transfer system for electric vehicle charging applications

Design of dual transmitter and single receiver coil to improve misalignment performance in inductive wireless power transfer system for electric vehicle charging applications

RF shimming in the cervical spinal cord at 7 T.

Advancing the development of 7 T MRI for spinal cord imaging is crucial for the enhanced diagnosis and monitoring of various neurodegenerative diseases and traumas. However, a significant challenge at this field strength is the transmit field inhomogeneity. Such inhomogeneity is particularly problematic for imaging the small, deep anatomical structures of the cervical spinal cord, as it can cause uneven signal intensity and elevate the local specific absorption ratio, compromising image quality. This multisite study explores several RF shimming techniques in the cervical spinal cord. Data were collected from 5 participants between two 7 T sites with a custom 8Tx/20Rx parallel transmission coil. We explored two radiofrequency (RF) shimming approaches from an MRI vendor and four from an open-source toolbox, showcasing their ability to enhance transmit field and signal homogeneity along the cervical spinal cord. The circularly polarized (CP), coefficient of variation (CoV), and specific absorption rate (SAR) efficiency shim modes showed the highest B1 + efficiency, and the vendor-based "patient" and "volume" modes showed the lowest B1 + efficiency. The coefficient of variation method produced the highest CSF/spinal cord contrast on T2*-weighted scans (ratio of 1.27 ± 0.03), and the lowest variation of that contrast along the superior-inferior axis. The study's findings highlight the potential of RF shimming to advance 7 T MRI's clinical utility for central nervous system imaging by enabling more homogenous and efficient spinal cord imaging. Additionally, the research incorporates a reproducible Jupyter Notebook, enhancing the study's transparency and facilitating peer verification.

A Receiver Position Estimation Method Based on LSTM for Multi-Transmitter Single-Receiver Wireless Power Transfer Systems

The multi-transmitter single-receiver wireless power transfer (MTSR-WPT) system has good tolerance for coil misalignment because the magnetic fields generated by multiple transmitters can be shaped to adapt to position changes in the receiver coil. In order to achieve magnetic field shaping of the MTSR-WPT system and increase power transfer efficiency, accurately estimating the position of the receiver coil is a key issue that needs to be addressed. In this article, a receiver position estimation method based on long short-term memory (LSTM) is proposed, which utilizes a data-driven approach to establish a neural network model. By learning the relationship between the measured time-series voltage data of the transmitter coils and the position of the receiver coil, the proposed model can achieve accurate position estimation of the receiver. Compared with previous works, the proposed method does not require communication between the transmitter and receiver, which is conducive to simplifying the system structure and reducing costs. In addition, the proposed LSTM-based method requires less derivation of complex formulas and the internal mechanism analysis of the system. Finally, a MTSR-WPT prototype is built to verify the proposed method. The experimental results show that the proposed LSTM-based method can achieve high-accuracy position estimation of the receiver. When the receiver moves within a range of 160 mm × 160 mm, the average error between the estimated receiver coil position using the proposed method and the actual receiver coil position is less than 2.40 mm.

A Three‐Phase Omnidirectional Wireless Charger Based on Segmented Arc‐Shaped Coupler With High Anti‐Rotation Offset Feature for AUVs

ABSTRACTWhen the autonomous underwater vehicle (AUV) is charged by wireless charging technology (WCT), the coupler will be misalignment due to the impact of marine environment factors, which can lead to the weak stability of the system output. Besides, the electromagnetic field generated by the coaxial coil is concentrated in the center of the AUV hull, and the strong electromagnetic field may interfere with the normal operation of the power electronic equipment inside the AUVs. To address the above problems, this paper proposes a novel coupler with high anti‐offset and suppression of the central magnetic field of the AUVs. The coupler is composed of a three‐phase segmented arc‐shaped transmitter coils and a cylindrical receiver coil. The coupler can implement the suppression of the AUV central magnetic field and the promotion of anti‐rotation offset feature under the omnidirectional uniform magnetic field control method. To better adapt the proposed coupler and meet the battery charging requirements, a three‐phase wireless charging topology with a relay is designed, which can acquire the smooth transition between the two charging modes without constructing the wireless communication between two sides and detecting the state of charge (SOC). Finally, to verify the feasibility of the proposed scheme, a 1‐kW AUV wireless charging prototype is built. The experimental results indicate that the maximum output power fluctuation rate of the system is 1.1% in the case of the full‐angle rotation offset.

Dynamic Wireless Charging of Electric Vehicles

Electric car sales have surged sixfold in the last five years, totalling more than 40 million. These vehicles are environmentally beneficial, have minimal operating and maintenance costs, and account for almost 11% of worldwide greenhouse gas emissions. They could be a critical technology in combating climate change and global pollution. Switching from traditional petrol or gas cars to electric vehicles (EVs) presents major hurdles in decreasing emissions, reducing operational expenses, and enhancing energy storage capabilities. Wireless charging electric vehicles provide hopeful answers to the drawbacks of wired charging like limited range and long charging times. This article outlines a thorough strategy to tackle the obstacles of wireless power transfer (WPT) for electric vehicles (EVs) through optimizing coupling frequency and coil design to improve efficiency, while reducing electromagnetic interference (EMI) and heat production. A new coil design and adaptive hardware are suggested to enhance power transfer efficiency (PTE) by determining the best magnetic resonant coupling WPT and reducing coil misalignment, a major obstacle to the widespread use of WPT for EVs. An innovative approach to creating and organizing lanes and amenities along roadsides for dynamic wireless charging (DWC) of electric vehicles (EVs) is presented. This involves enhancing transmitter coils (TCs), receiver coils (RCs), and compensation circuits. Dynamic Wireless Charging utilizes Resonant Inductive Coupling to transfer electrical power wirelessly between two coils. An alternating current in the primary coil creates a magnetic field, inducing a voltage in the secondary coil. This system is used for dynamic charging of Electric Vehicles, with primary coils installed beneath the road and secondary coils mounted on the EV. Efficiency is dependent on high-frequency AC and compensation network tuning. The manuscript introduced a novel method for dynamically charging electric vehicles demonstrating its potential for sustainable and cost-effective EV infrastructure. Future research will focus on enhancing system efficiency and extending the charging lane distance. DOI: https://doi.org/10.52783/pst.1502

Structure optimization of transmission coil of wireless power transmission system for rail transit vehicles

Abstract To solve the transmission efficiency problem of traditional wireless energy systems applied to rail transit vehicles. In this paper, the key components of a wireless power transmission system, such as the transmission efficiency of the transmission coil and the poor anti-deviation ability of the coil, are studied. Firstly, this paper analyzes the traditional planar circular and square coil shapes, analyzes the magnetic field characteristics of the traditional transmission coil structures by ANSYS Maxwell simulation software, and obtains the advantages and disadvantages of different coil structures. According to the analysis structure, the coil structure is optimized and improved, and the coil structure form of the combined coil is put forward. Through the comparative analysis of finite element simulation software, it is attested that combined coil structure has a significant improvement in transmission efficiency and anti-deviation ability.

Radio-magnetotelluric transmitter in full-bridge resonance inverter

Abstract Radio-magnetotelluric (RMT) is a widely used method for shallow subsurface electromagnetic exploration, employing magnetic sources (coils) for signal transmission. A common challenge is the low frequency and unstable current of the instrumentation. To address this, a full-bridge resonant inverter circuit is designed for signal transmission.

Omnidirectional Wireless Power Transfer for Millimetric Magnetoelectric Biomedical Implants.

Miniature bioelectronic implants promise revolutionary therapies for cardiovascular and neurological disorders. Wireless power transfer (WPT) is a significant method for miniaturization, eliminating the need for bulky batteries in today's devices. Despite successful demonstrations of millimetric battery-free implants in animal models, the robustness and efficiency of WPT are known to degrade significantly under misalignment incurred by body movements, respiration, heart beating, and limited control of implant orientation during surgery. This paper presents an omnidirectional WPT platform for millimetric bioelectronic implants, employing the emerging magnetoelectric (ME) WPT modality, and "magnetic field steering" technique based on multiple transmitter (TX) coils. To accurately sense the weak coupling in a miniature implant and adaptively control the multi-coil TX array in a closed loop, we develop an Active Echo (AE) scheme using a tiny coil on the implant. Our prototype comprises a fully integrated 14.2mm3 implantable stimulator embedding a custom low-power System-on-Chip (SoC) powered by an ME film, a transmitter with a custom three-channel AE RX chip, and a multi-coil TX array with mutual inductance cancellation. The AE RX achieves -161dBm/Hz input-referred noise with 64dB gain tuning range to reliably sense the AE signal, and offers fast polarity detection for driver control. AE simultaneously enhances the robustness, efficiency, and charging range of ME WPT. Under 90° rotation from the ideal position, our omnidirectional WPT system achieves 6.8× higher power transfer efficiency (PTE) than a single-coil baseline. The tracking error of AE negligibly degrades the PTE by less than 2% from using ideal control.

Efficient Wireless Power Transmission System

The work focuses on wireless power transfer for electric vehicle charging stations. The aim of the study is to analyse the processes in the system of wireless magnetic resonance transmission of electrical energy using magnetic fields and to develop approaches to improve the efficiency of such systems. The set objectives were achieved by solving the following problems: the operation of the wireless power transmission system with a resonance-tuned transmission coil, the determination of the optimal energy parameters of wireless power transmission on the example of a magnetically coupled system with a series-sequential resonant circuit. The main results of the study are as follows: it is shown that the necessary condition for obtaining the maximum power in the receiver is not only the tuning to the resistance of the receiving coil, but also the inclusion of the receiving circuit to a certain active load resistance, depending on the coupling coefficient between the transmitting and receiving coils, and analytical expressions are obtained, by means of which it is possible to calculate the load resistance at which the considered power transmission system has the maximum efficiency; it is proved that the transmission efficiency of the series-sequential resonant circuit is maximum in the single resonance mode and depends on the coupling coefficient. Significance of the obtained results: It is proved that magnetic resonance transmission of electric energy in the case of series-sequential scheme of wireless power transmission is more effective in comparison with series-parallel, at frequencies not exceeding 100 kHz, which has a positive effect on the operation of charging stations for electric vehicles in an urban industrial environment and, as a result, on solving the problem of compliance of such systems with electromagnetic compatibility requirements.

Wireless power transfer systems and wireless charging design between electric vehicles

The foundations of wireless power transmission were laid down by Nikola Tesla many years ago, by transmitting energy wirelessly using a Tesla coil. Nikola Tesla's work many years ago pioneered wireless power transmission studies today. Wireless power transmission, which telephone companies have focused on in recent years, also forms the basis for charging electric vehicles. One of the main reasons why lithium ion batteries are preferred in electric vehicles is the advantages they offer regarding the charging process. These batteries provide longer range compared to other battery types, thanks to their high energy density, that is, they can store more energy compared to their size. At the same time, faster charging capabilities are a great advantage for electric vehicle owners. As a result, charging technology is very important in electric vehicles. In this study, we will present a design project that enables electric vehicles, which have become more common in daily life with the developing technology, to transfer their charge to each other contactlessly in emergency situations. In the design, the receiver coil will be placed on the front hood of the vehicle and the transmitter coil will be placed on the rear hood of the vehicle. There will be a distance sensor where the transmitter coil is located, thanks to this sensor, the distance can be adjusted. When the vehicles reach the optimum distance, the distance sensor will give a warning and be charged enough to go to the nearest charging station. In addition, thanks to the ease of sharing for emergencies, emergency vehicles (ambulances) will be able to quickly receive energy from another vehicle and continue their duties without interruption. In this way, we will reduce the towing cost of electric and hybrid vehicles and provide drivers with uninterrupted driving. In the wireless charging station; We will offer many advantages such as getting rid of cable clutter, providing ease of use, compatibility with all devices, multiple charging and durability.

An application of multi-magnetic circular planar spiral relay to improve the performance of wireless power transfer system

Introduction. The system of delivering electricity without wires is known as wireless power transfer (WPT). The WPT system has been extensively used in a number of industries, health, telecommunications, and transportation. However, the distance between the transmitter and receiver coils has a significant impact on its efficiency. Lower power can be generated between coils the farther apart they are, and vice versa. The novelty of the proposed work is innovative in that it develops a multi-magnetic circular planar spiral relay to improve the WPT system’s performance and designs circular planar spiral coils to achieve an appropriate inductance value for the 5 kHz matching frequency. The goal of paper is to create a circular planar spiral coil with an appropriate inductance value for the 5 kHz matching frequency. Methods. The transmitter circuit, receiver circuit, and DC voltage source are parts of the WPT system. The inverter circuit uses the inductive coupling technique to transform the DC power source into AC voltage on the transmitter coil. The suggested coil is additionally employed as a multi-magnetic circular planar spiral relay in order to increase the mutual inductance between the receiver and transmitter coils. Results. To monitor the power improvement that results from adding a multi-magnetic relay to the system, the transmitter coil, receiver coil, and multi-magnetic relay are positioned at specific distances from each other. With Vdc = 30 V and dtr = 21 cm, the power received at the receiver coil can therefore be improved by up to 67 %. Practical value. The multi-magnetic circular planar spiral relay applied in the WPT system has been investigated in an experimental study and it can be applied for DC load. References 26, table 1, figure 18.

Towards Advancing Real-Time Railroad Inspection Using a Directional Eddy Current Probe

In the field of railroad safety, the effective detection of surface cracks is critical, necessitating reliable, high-speed, non-destructive testing (NDT) methods. This study introduces a hybrid Eddy Current Testing (ECT) probe, specifically engineered for railroad inspection, to address the common issue of “lift-off noise” due to varying distances between the probe and the test material. Unlike traditional ECT methods, this probe integrates transmit and differential receiver (Tx-dRx) coils, aiming to enhance detection sensitivity and minimise the lift-off impact. The study optimises ECT probes employing different transmitter coils, emphasising three main objectives: (a) quantitatively evaluating each probe using signal-to-noise ratio (SNR) and outlining a real-time data-processing algorithm based on SNR methodology; (b) exploring the frequency range proximal to the electrical resonance of the receiver coil; and (c) examining sensitivity variations across varying lift-off distances. The experimental outcomes indicate that the newly designed probe with a figure-8 shaped transmitter coil significantly improves sensitivity in detecting surface cracks on railroads. It achieves an impressive SNR exceeding 100 for defects with minimal dimensions of 1 mm in width and depth. The simulation results closely align with experimental findings, validating the investigation of the optimal operational frequency and lift-off distance for selected probe performance, which are determined to be 0.3 MHz and 1 mm, respectively. The realisation of this project would lead to notable advancements in enhancing railroad safety by improving the efficiency of crack detection.

A Wireless Miniature Injectable Device with Memory-Assisted Backscatter for Multimodal Animal Physiological Monitoring.

This paper introduces a wirelessly powered multimodal animal physiological monitoring application-specific integrated circuit (ASIC). Fabricated in the 180 nm process, the ASIC can be integrated into an injectable device to monitor subcutaneous body temperature, electrocardiography (ECG), and photoplethysmography (PPG). To minimize the device size, the ASIC employs a miniature receiver (Rx) coil for wireless power receiving and data communication through a single inductive link operating at 13.56 MHz. We propose a folded L-shape Rx coil with improved coupling to the transmitter (Tx) coil, even in the presence of misalignment, and enhanced quality factor. The ASIC functions alternatively between recording and sleeping modes, consuming 2.55 μW on average. For PPG measurements, a reflection-type PPG sensor illuminates an LED with tunable current pulses. A current-input analog frontend (AFE) amplifies the current of a photodiode (PD) with 30.8 pARMS current input-referred noise (IRN). The ECG AFE captures ECG signals with a configurable gain of 45-80 dB. The temperature AFE achieves 0.02 ̊C inaccuracy within a sensing range between 27-47 ̊C. The AFE outputs are sequentially digitized by a 10-bit successive approximation register (SAR) analog-to-digital converter (ADC) with an effective number of bits (ENOB) of 8.79. To improve the reliability of data transmission, we propose a memory-assisted backscatter scheme that stores ADC data in an off-chip memory and transmits it when the coupling condition is stable. This scheme achieves a package loss rate (PLR) lower than 0.2% while allowing 24-hour data storage. The device's functionality has been evaluated by in vivo experiments.

A small-loop double-coil decoupling transient electromagnetic device for high-sensitivity near-surface detection

Small-loop transient electromagnetic (TEM) devices, several meters in size, are increasingly applied to near-surface geophysical exploration in space-limited environments. But the transmitter (TX) coil significantly affects the early time data acquisition of the receiver (RX) coil during current turn-off, resulting in the loss of shallow signals and creating a significant blind zone problem. We report a double-coil decoupling TEM (DCDTEM) device to solve this problem. The novel DCDTEM device ensures a weak primary magnetic flux region between the two coplanar TX coils with the same current direction and different radii. Simulation results indicate that the transmitting field of the DCDTEM device is more focused than the traditional central loop device, ensuring a stronger coupling with the target. The 3D TEM forward-modeling results show that the DCDTEM device has the highest detection sensitivity, together with a relatively high lateral resolution compared with other small-loop TEM devices. We further carry out several physical experiments to test the response characteristics of the DCDTEM device with reference to the offset and the ratio of turns between the TX and RX coils. The experimental results ensure that the position of the zero magnetic flux point can be accurately calibrated and mitigate interference from TX coils. Our DCDTEM device is also applied in a field test on water pipe detection, demonstrating its practicality in near-surface detection.

Dynamic Wireless Charging of Electric Vehicles Using PV Units in Highways

Transitioning from petrol or gas vehicles to electric vehicles (EVs) poses significant challenges in reducing emissions, lowering operational costs, and improving energy storage. Wireless charging EVs offer promising solutions to wired charging limitations such as restricted travel range and lengthy charging times. This paper presents a comprehensive approach to address the challenges of wireless power transfer (WPT) for EVs by optimizing coupling frequency and coil design to enhance efficiency while minimizing electromagnetic interference (EMI) and heat generation. A novel coil design and adaptive hardware are proposed to improve power transfer efficiency (PTE) by defining the optimal magnetic resonant coupling WPT and mitigating coil misalignment, which is considered a significant barrier to the widespread adoption of WPT for EVs. A new methodology for designing and arranging roadside lanes and facilities for dynamic wireless charging (DWC) of EVs is introduced. This includes the optimization of transmitter coils (TCs), receiving coils (RCs), compensation circuits, and high-frequency inverters/converters using the partial differential equation toolbox (pdetool). The integration of wireless charging systems with smart grid technology is explored to enhance energy distribution and reduce peak load issues. The paper proposes a DWC system with multiple segmented transmitters integrated with adaptive renewable photovoltaic (PV) units and a battery system using the utility main grid as a backup. The design process includes the determination of the required PV array capacity, station battery sizing, and inverters/converters to ensure maximum power point tracking (MPPT). To validate the proposed system, it was tested in two scenarios: charging a single EV at different speeds and simultaneously charging two EVs over a 1 km stretch with a 50 kW system, achieving a total range of 500 km. Experimental validation was performed through real-time simulation and hardware tests using an OPAL-RT platform, demonstrating a power transfer efficiency of 90.7%, thus confirming the scalability and feasibility of the system for future EV infrastructure.

A Reconfigurable IPT System With CC‐CV Output Characteristics and High Misalignment Tolerance

ABSTRACTMisalignment between transmission coils is an inevitable challenge in inductive power transfer (IPT) systems, particularly affecting the constant current (CC) and constant voltage (CV) outputs essential for battery charging. A reconfigurable IPT system with high misalignment tolerance and CC‐CV output characteristics is proposed in this article. The main circuit of the system is composed of a LCC‐LCC and LCC‐S topology with two intermediate coils, and two switches equipped with single unidirectionally blocking MOSFETs are incorporated on the secondary side to transition from CC to CV mode. A comprehensive analysis of the output characteristics for the proposed hybrid topology in both CC and CV modes is provided. Furthermore, the parameter optimization design based on BP coil for wide misalignment tolerance is presented. The experimental results demonstrate that the proposed reconfigurable IPT system can maintain stable CC and CV outputs within 50% lateral and vertical offset (the coupling factor varies from 0.1 to 0.21), when the load varies from 11 to 80 Ω, and the output current and voltage fluctuations remain below 5%.

A Design Review for Biomedical Wireless Power Transfer Systems with a Three-Coil Inductive Link through a Case Study for NICU Applications.

This paper outlines a design approach for biomedical wireless power transfer systems with a focus on three-coil inductive links for neonatal intensive care unit applications. The relevant literature has been explored to support the design approach, equations, simulation results, and the process of experimental analysis. The paper begins with a brief overview of various power amplifier classes, followed by an in-depth examination of the most common power amplifiers used in biomedical wireless power transfer systems. Among the traditional linear and switching amplifier classes, class-D and class-E switching amplifiers are highlighted for their enhanced efficiency and straightforward implementation in biomedical contexts. The impact of load variation on these systems is also discussed. This paper then explores the basic concepts and essential equations governing inductive links, comparing two-coil and multi-coil configurations. In the following, the paper discusses foundational coil parameters and provides theoretical and experimental analysis of both two-coil and multi-coil inductive links through step-by-step measurement techniques using lab equipment and addressing the relevant challenges. Finally, a case study for neonatal intensive care unit applications is presented, showcasing a wireless power transfer system operating at 13.56 MHz for powering a wearable device on a patient lying on a mattress. An inductive link with a transmitter coil embedded in a mattress is designed to supply power to a load at distances ranging from 4 cm to 12 cm, simulating the mattress-to-chest distance of an infant. the experimental results of a three-coil inductive link equipped with a Class-E power amplifier are reported, demonstrating power transfer efficiency ranging from 75% to 25% and power delivery to a 500 Ω-load varying from 340 mW to 25 mW over various distances.