Wireless Energy Transfer Research Articles

Dual LCL resonance compensation for the design of electric vehicle wireless energy transmission system topology

Dual LCL resonance compensation for the design of electric vehicle wireless energy transmission system topology

Throughput maximization scheme of the IRS-aided wireless powered NOMA systems

The computation complexity of the existing resource allocation schemes to maximize sum throughput is very high for intelligent reflecting surface (IRS)-assisted wireless powered non-orthogonal multiple access (NOMA) system. Therefore, a low complexity resource allocation method to maximize sum throughput is considered by joint optimizing phase shifts and time allocation. Firstly, to reduce the variables that need to be optimized, we derive the problem with only phase shifts as variables, and further deduce optimization problem of phase shifts only for downlink wireless energy transmission (WET) process. Then, the problem of phase shifts for WET process is solved directly by transforming multi-variable optimization problem into that with single variable, and the phase shifts for the uplink wireless information transmission process are got as well with given phase shifts for WET process. Finally, with given phase shifts, the optimal time allocation is obtained by using the function extremum method. Theoretical analysis demonstrates that the proposed scheme has low computational complexity, and the simulation results show that sum throughput of the proposed scheme is no less than that of the existing schemes in the same scenario.

Linear generator for power supply to on-board consumers of high-speed magnetically levitated carriages

Background: Maglev transport is a promising mode of transport that can provide passenger and freight transportation at speeds of up to 400-500 km/h, and in the longer term – up to 1000 km/h. Active research in this area is being conducted in China, Japan, and the USA. Currently, in China and Japan, speeds of 450-500 km/h have been achieved for commercial transportation, and promising programs have been adopted for the construction of high-speed maglev tracks and the creation of rolling stock. At such speeds, one of the pressing problems is the problem of contactless energy transfer for on-board consumers located on the carriage, because it is very difficult to ensure reliable contact current collection at speeds of 450-500 km/h and above.
 Aim: development of the design, calculation and analysis of the characteristics of a linear generator of electrical energy for contactless power transfer to the moving crew of high-speed magnetically levitated transport.
 Materials and methods: to calculate the external magnetic field of the linear generator inductor and the EMF induced in the receiving coil of the crew, methods of electromagnetic field theory and electrical circuit theory were used; calculation algorithms are implemented in the Visual Basic for Applications software environment.
 Results: a design was proposed and the calculation of the external magnetic field of an inductor with transposition of conductors was performed; to increase the EMF induced in the receiving coil of the crew, it is proposed to give the receiving coil a double 8-shape; the most rational inter-circuit distance of the linear generator inductor has been established; the nature of the change in the magnetic flux penetrating the receiving coil when the vehicle moves, and the magnitude of the emf induced in the receiving coil are determined.
 Conclusion: the results can be used in the development of rolling stock for promising high-speed maglev transport systems.

Design and Performance Analysis of New Coupling Magnetic Core Structure for Dynamic Wireless Charging System of Electric Vehicle

Aiming at the problems of high cost, low efficiency, low power, and high electromagnetic radiation in the dynamic wireless charging system for electric vehicles (EVs), the cover‐like coupling structure and the return‐like coupling structure are designed, and the unique concave structure has excellent engineering practicability. Using Ansoft software for simulation and analysis, the newly proposed two coupling structures have significantly improved the induced voltage and electromagnetic induction strength at the pickup end compared with other commonly used coupling core structures. According to the advantages of practical applications, the application of its composite core structure for simulation and analysis proves that the cover‐like structure of the magnetic field strength at the pickup end not only enhances the magnetic field strength on the coil but also has a good magnetic field shielding effect. The lateral displacement of the EV is kept within the range of 10 cm, the coupling distance is 0–5 cm, the charging is stable, and the transmission efficiency is high. Finally, a dynamic wireless charging experimental platform for small EVs is constructed, which verifies that the new coupling core structure can significantly improve the transmission power and efficiency of the charging system and significantly reduce the economic cost.

Miniaturized near-field-focused antenna array

This paper presents a microstrip planar antenna array designed for near-field focusing operating at 10 GHz. It is a challenge to reach the phase and amplitude distribution of near-field-focused antenna arrays with small focal spots. The antenna elements of this array are arranged radially on the aperture of only 5.6λ 0 × 5.6λ 0, which reduces the focal spot diameter. We designed an unequal-amplitude unequal-phase power divider to reach phase distribution and binomial taper distribution. The proposed array suppresses the sidelobes on the focal plane. It increases the electric field intensity by 11.46 dB compared with the horn with the same aperture size and increases 9.42 dB compared with the equal-phase array. The focus spot diameter is only 0.33λ 0. The simulated and measured results are in good agreement, which verifies the high performance of the array. This miniaturized high-focus array has a good prospect in near-field applications like wireless energy transmission and industrial detection.

Robust Integrated Data and Energy Transfer Aided by Intelligent Reflecting Surfaces: Successive Target Migration Optimization Toward Energy Sustainability

Intelligent reflecting surfaces (IRSs) can actively adjust the wireless environment. However, accurate channel estimation on IRS-aided communication systems is difficult to obtain. Therefore, we study a robust beamforming design for an IRS-aided integrated data and energy transfer (IDET) with imperfect channel state information (CSI). Against the uncertain channel estimation error, we robustly design the transmit beamformers of the transmitter and the passive reflecting beamformer of the IRS to minimize the transmit power by satisfying both the wireless data transfer (WDT) and wireless energy transfer (WET) requirements for realising energy-sustainability in 6G. A successive target migration optimization (STMO) algorithm is proposed to obtain a robust design. The transmit covariance matrices are optimized by relaxing rank-one constraints, when a passive reflecting beamformer is given. Then, the target to minimize the transmit power is migrated to maximize the QoS requirements of energy users due to the fixed transmit power. A local optimal reflecting beamformer is obtained for improving the attainable WET performance, when the transmit covariance matrices are given. Finally, we prove that the rank-one transmit beamformers can always be found, which have the same WET and WDT performance as the transmit covariance matrices. The numerical results demonstrate the advantage of our design.

Intelligent Reflecting Surface-Assisted Wireless Powered Heterogeneous Networks

In this paper, we introduce an intelligent reflecting surface (IRS)-assisted wireless powered heterogeneous network (WPHN) consisting of two heterogeneous groups of devices. Specifically, one group of devices, i.e., energy-harvesting devices (EHDs), are charged by external energy supplies, while the other group of devices, i.e., non-energy-harvesting devices (NEHDs), are powered by internal energy supplies. An IRS aims to participate in the wireless energy transfer (WET) in downlink and the wireless information transfer (WIT) in the uplink. A sum throughput maximization problem is formulated subject to the constraints of individual energy consumption, transmission time scheduling, and IRS phase shifts. To cope with the non-convexity of the problem, we first derive the optimal IRS phase shifts of the uplink WIT independently. Next, the semi-definite programming (SDP) relaxation is adopted to recast this non-convex problem into the convex one, which can be numerically solved. Then, a novel low-complexity scheme is developed to gain more insights and mitigate the computational complexity induced by the SDP relaxation. In particular, the dual problem and Karush-Kuhn-Tucker conditions are first utilized to obtain the optimal transmission time scheduling. Then, we propose a method based on Riemannian manifold optimization to compute the optimal IRS phase shifts of the downlink WET in closed-form. Finally, simulation results are presented to verify the optimality of our proposed scheme, and highlight the benefits induced by the IRS to coordinate these heterogeneous devices.

Research on X-ray-based energy conversion technology and assessment of application prospect

A new type of wireless energy transfer (radiation energy to electricity) power system is proposed for small-scale distributed energy utilization. To utilize radiation energy efficiently, energy conversion technologies based on different conversion modules and dissimilar material combination schemes are used. A variety of schemes such as single photovoltaic cell and single/multilayer fluorescent layer integrated with photovoltaic cell are designed. The maximum power density ranges from 7.93 nW/cm3 (tube voltage: 30 kV, tube current: 1 mA) to 6.7 µW/cm3 (tube voltage: 110 kV, tube current: 1 mA). After the structure layout of the system is matched and optimized, the maximum output power in radio-luminescent mode can be much higher than that in radio-voltaic mode. In particular, the maximum output power of conversion modules with a stacked layer can be increased by more than 36 times in radio-luminescent mode compared to radio-voltaic mode. At the same time, the effect of the distance of wireless energy transfer on the output performance of the energy conversion module is analyzed. To adjust the radiation intensity and field parameters better, X-ray tube is used as the radiation excitation source for performance testing and analysis. The performance attenuation of different energy conversion modules is similar when responding to X-ray over long distances. Compared with the radio-voltaic mode, the findings of this paper show that the output power of the system based on the radio-luminescent mode can be an order of magnitude higher.

Model‐based systems engineering approach to the study of electromagnetic interference and compatibility in wireless powered microelectromechanical systems

AbstractElectromagnetic Interference and Compatibility (EMI–EMC) are a serious problem in Microelectromechanical Systems (MEMS), and specially in powered by wireless energy transfer MEMS. Most MEMS have dimensions in the order of 1 mm or less, thus, most of the suitable electromagnetic radiation sources have wavelengths larger than this, making isolation of electromagnetic effects very difficult. Model‐Based Systems Engineering (MBSE) can be an excellent tool to deal with EMI—EMC in MEMS during early design phases. In this work, we present a problem‐solving procedure and integration of EMI—EMC in MEMS from a Model‐Based Systems Engineering perspective. This approach is described in detail by a real example using a procedure based on nine steps fully integrated with the proposed systems engineering methodology. For example, the use of context diagrams (IBDs) and N SQUARE charts to describe EMC interactions is explained in detail. The system is formed by a Wireless Power Transfer (WPT) subsystem working near 2.45 or 4.5 GHz coupled to an electromagnetic micromotor. This micromotor contains copper microcoils which can receive electromagnetic radiation directly at the same time that the WPT subsystem. The greatest difficulty is, then, to power the WPT while isolating the micromotor, and optimizing the coupling interface. A summary of the most important EMC concepts and tools are reviewed from the systems engineer perspective and possible problems during the design and testing phases are discussed in detail using the example.

Radio Map-Based Trajectory Design for UAV-Assisted Wireless Energy Transmission Communication Network by Deep Reinforcement Learning

In this paper, we consider a wireless energy-carrying communication network of a UAV. In this communication network, the internet of things (IoT) devices maintain their work via the power supply of batteries. The energy of batteries is slowly consumed over time. The UAV adopts the full-duplex working mode and the flight hover protocol, that is, they can power the target device in the hover position and collect base station data at the same time. Unlike traditional methods, which seek to achieve wireless energy transmission, this paper adopts deep reinforcement learning. On the one hand, the deep reinforcement learning algorithm seeks to solve the dynamic programming problem without a model. The traditional method often requires a prior channel model, to form a formula about variables for convex optimization, while reinforcement learning only requires the interaction between agents and the environment. Then, the strategy is optimized according to the reward function feedback. On the other hand, traditional optimization methods generally solve static programming problems. Since IoT devices constantly collect information from the surrounding physical environment, and their requirements for power supply change dynamically, traditional methods are relatively complex and require huge computational overhead, while deep reinforcement learning performs well in complex problems. The purpose of our work is that with the assistance of the radio map, a UAV can find the best hover position, maximize the energy supplied by the UAV, maximize the data throughput collected, and minimize the energy consumption. The simulation results show that the proposed algorithm can well find the best hovering position of the UAVs and significantly improve the performance of the UAV-assisted wireless energy transmission communication network.

A Novel Method of Wireless Micro Energy Transmission Based on MEMS Micro Coil.

Based on current implantable devices, a battery's rigidity and large size makes it prone to immune rejection and wound incisions. Additionally, it is limited by its finite lifespan, which hinders long-term usage. These limitations greatly restrict the development of implantable medical device systems towards miniaturization and minimally invasive approaches. Consequently, obtaining high-fidelity and stable biological signals from the target tissue area of the organism remains challenging. Therefore, there is a need to develop wireless power transmission technology. In this paper, we propose a wireless micro energy transfer method based on MEMS micro coils for charging implantable devices. Through simulation calculations, we first investigate the influence of coaxial distance, horizontal displacement, and rotation angle between the MEMS micro coil and the transmitting coil on power transmission. Subsequently, we utilize micro nanofabrication technology to create a MEMS micro spiral copper coil with a line width, thickness, and spacing of 50 µm and a total of five turns. Finally, we conduct wireless power transmission tests on the coil. The results show that, when the transmitting coil and the receiving coil are 10 mm apart and the operating frequency is 100 kHz, the power of the wireless power transmission system reaches 45 µW. This power level is sufficient to meet the power supply requirements of implantable pacemakers. Therefore, this technology holds great potential for applications in the field of wireless power transmission for implantable medical devices, including pacemakers and brain neurostimulators.

Diffraction-free distance enhancement of Bessel beams based on spatial domain phase modulation

Bessel beams have garnered significant interest due to their unique diffraction-free properties and extensive potential applications. In this work, we propose a spatial domain phase modulation theory to achieve diffraction-free distance enhancement of Bessel beams, overcoming the limitation of the traditional methods due to the inability to infinitely decrease the wave vector angle. The traditional formula for non-diffraction distance is also modified. Simulation results demonstrate that our proposed scheme can significantly increase the maximum diffraction-free distance of zero-order and higher-order Bessel beams by more than two times, while ensuring the self-healing property of Bessel beams. Furthermore, our proposed scheme is not restricted to specific systems or limited to the optical wavelength range. This implies that the results have great applicative potential in long-distance free-space optical communication and wireless energy transmission.

Parametric investigations of wireless energy transfer using strain-mediated magnetoelectric transmitter-receiver

Magnetoelectric (ME) composites inherently convert magnetic energy to electrical energy and vice-versa, making them a viable technology in wireless energy transfer (WET) applications. This article focuses on identifying the optimal configuration for achieving relatively high ME power conversion efficiency in a fully ME-based transmitter/receiver composite system. Two configurations of ME composites, one in concentric composite rings and the other in layered laminate formation, have been fabricated and used alternately as transmitters and receivers. The influence of three important parameters has been experimentally studied and reported, including the effect of (1) the magnetization state of the magnetostrictive components and (2) the relative orientation of and (3) the separation distance between the transmitter and the receiver. It has been found that a higher energy conversion efficiency is obtained in a configuration where the laminated plate was used as the transmitter while the ring composites acted as the receiver. Furthermore, the location and alignment of the receiver significantly influence the output transferred power. Lastly, the distance between the transmitter and the receiver has been observed to have an exponential inverse influence on the performance of the investigated WET system. These results have been deciphered by experimentally generating horizontal and vertical magnetic field mapping around the composite systems and capacitance measurement of the piezoelectric element. Thus, this article presents a detailed study of the parameters and their influence on the performance of the ME-based WET technology, which would be extremely useful in designing and optimizing devices based on this technology.

An implantable, wireless, battery-free system for tactile pressure sensing

The sense of touch is critical to dexterous use of the hands and thus an essential component of efforts to restore hand function after amputation or paralysis. Prosthetic systems have addressed this goal with wearable tactile sensors. However, such wearable sensors are suboptimal for neuroprosthetic systems designed to reanimate a patient’s own paralyzed hand. Here, we developed an implantable tactile sensing system intended for subdermal placement. The system is composed of a microfabricated capacitive pressure sensor, a custom integrated circuit supporting wireless powering and data transmission, and a laser-fused hermetic silica package. The miniature device was validated through simulations, benchtop assessment, and testing in a primate hand. The sensor implanted in the fingertip accurately measured applied skin forces with a resolution of 4.3 mN. The output from this novel sensor could be encoded in the brain with microstimulation to provide tactile feedback. More broadly, the materials, system design, and fabrication approach establish new foundational capabilities for various applications of implantable sensing systems.

UAV-Aided Wireless Energy Transfer for Sustaining Internet of Everything in 6G

Unmanned aerial vehicles (UAVs) are a promising technology used to provide on-demand wireless energy transfer (WET) and sustain various low-power ground devices (GDs) for the Internet of Everything (IoE) in sixth generation (6G) wireless networks. However, an individual UAV has limited battery energy, which may confine the required wide-range mobility in a complex IoE scenario. Furthermore, the heterogeneous GDs in IoE applications have distinct non-linear energy harvesting (EH) properties and diversified energy and/or communication demands, which poses new requirements on the WET and trajectory design of UAVs. In this article, to reflect the non-linear EH properties of GDs, we propose the UAV’s effective-WET zone (E-zone) above each GD, where a GD is assured to harvest non-zero energy from the UAV only when the UAV transmits into the E-zone. We then introduce the free space optics (FSO) powered UAV with enhanced mobility, and propose its adaptive WET for the GDs with non-linear EH. Considering the time urgency of the different energy demands of the GDs, we propose a new metric called the energy latency time, which is the time duration that a GD can wait before becoming fully charged. By proposing the energy-demand aware UAV trajectory, we further present a novel hierarchical WET scheme to meet the GDs’ diversified energy latency time. Moreover, to efficiently sustain IoE communications, the multi-UAV enabled WET is employed by unleashing their cooperative diversity gain and the joint design with the wireless information transfer (WIT). The numerical results show that our proposed multi-UAV cooperative WET scheme under the energy-aware trajectory design achieves the shortest task completion time as compared to the state-of-the-art benchmarks. Finally, the new directions for future research are also provided.

Optimization analysis of transmission characteristics of wireless energy transmission system based on dynamic tuning algorithm

Abstract This paper aims to optimize the transmission characteristics of the wireless energy transmission system by optimizing the design of the coupling coils in the system, the system multi-parameter matching and the coil offset problem so that the overall wireless energy transmission system works in the best condition. The mathematical model of the power and efficiency of the two-coil MCRWPT is derived through the optimal tuning theory, and the principle of the wireless energy transmission method is analyzed to determine the wireless energy transmission method of the equivalent capacitive regulation circuit. By comparing the effects of load on output power and transmission efficiency under different topologies, a plane with a two-coil structure applicable to the wireless charging transmission system is selected to improve the transmission efficiency of the system. In the experimental verification of the WPT transmission characteristics optimization and dynamic tuning, it is concluded that the efficacy of the system is improved simultaneously with the transmission efficiency up to 91% when the load is adjusted to 298 mΩ for the load value adjusted at the transmission distance of 0.075m.

On CSI-Free Multiantenna Schemes for Massive Wireless-Powered Underground Sensor Networks

Radio-frequency wireless energy transfer (WET) is a promising technology to realize wireless-powered underground sensor networks (WPUSNs) and enable sustainable underground monitoring. However, due to the severe attenuation in harsh underground soil and the tight energy budget of the underground sensors, traditional WPUSNs relying on the channel state information (CSI) are highly inefficient, especially in massive WET scenarios. To address this challenge, we comparatively assess the feasibility of several state-of-the-art CSI-free multi-antenna WET schemes for WPUSNs, under a given power budget. Moreover, to overcome the extremely low WET efficiency in underground channels, we propose a distributed CSI-free system, where multiple power beacons (PBs) simultaneously charge a large set of underground sensors without any CSI. We consider the position-aware K-Means and the position-agnostic equally-far-from-center (EFFC) approaches for the optimal deployment of the PBs. Our results evince that the performance of the proposed distributed CSI-free system can approach or even surpass that of a traditional full-CSI WET strategy, especially when adopting an appropriate CSI-free scheme, applying the advisable PBs deployment approach, and equipping the PBs with an appropriate number of antennas. Finally, we discuss the impact of underground parameters, i.e., the burial depth of devices and the volumetric water content of soil, on the system’s performance, and identify potential challenges and research opportunities for practical distributed CSI-free WPUSNs deployment.

Optimal Resource Management for Hierarchical Federated Learning Over HetNets With Wireless Energy Transfer

Remote monitoring systems analyze the environment dynamics in different smart industrial applications, such as occupational health and safety, and environmental monitoring. Specifically, in industrial Internet of Things (IoT) systems, the huge number of devices and the expected performance put pressure on resources, such as computational, network, and device energy. Distributed training of Machine and Deep Learning (ML/DL) models for intelligent industrial IoT applications is very challenging for resource limited devices over heterogeneous wireless networks (HetNets). Hierarchical Federated Learning (HFL) performs training at multiple layers offloading the tasks to nearby Multi-Access Edge Computing (MEC) units. In this paper, we propose a novel energy-efficient HFL framework enabled by Wireless Energy Transfer (WET) and designed for heterogeneous networks with massive Multiple-Input Multiple-Output (MIMO) wireless backhaul. Our energy-efficiency approach is formulated as a Mixed-Integer Non-Linear Programming (MINLP) problem, where we optimize the HFL device association and manage the wireless transmitted energy. However due to its high complexity, we design a Heuristic Resource Management Algorithm, namely H2RMA, that respects energy, channel quality, and accuracy constraints, while presenting a low computational complexity. We also improve the energy consumption of the network using an efficient device scheduling scheme. Finally, we investigate device mobility and its impact on the HFL performance. Our extensive experiments confirm the high performance of the proposed resource management approach in HFL over HetNets, in terms of training loss and grid energy costs.

Channel Statistics Based Wireless Energy Transfer with Energy Demand in Rician Fading Channel

Channel Statistics Based Wireless Energy Transfer with Energy Demand in Rician Fading Channel

Concept of a fully-implantable system to monitor tumor recurrence

Current treatment for glioblastoma includes tumor resection followed by radiation, chemotherapy, and periodic post-operative examinations. Despite combination therapies, patients face a poor prognosis and eventual recurrence, which often occurs at the resection site. With standard MRI imaging surveillance, histologic changes may be overlooked or misinterpreted, leading to erroneous conclusions about the course of adjuvant therapy and subsequent interventions. To address these challenges, we propose an implantable system for accurate continuous recurrence monitoring that employs optical sensing of fluorescently labeled cancer cells and is implanted in the resection cavity during the final stage of tumor resection. We demonstrate the feasibility of the sensing principle using miniaturized system components, optical tissue phantoms, and porcine brain tissue in a series of experimental trials. Subsequently, the system electronics are extended to include circuitry for wireless energy transfer and power management and verified through electromagnetic field, circuit simulations and test of an evaluation board. Finally, a holistic conceptual system design is presented and visualized. This novel approach to monitor glioblastoma patients is intended to early detect recurrent cancerous tissue and enable personalization and optimization of therapy thus potentially improving overall prognosis.