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This manuscript presents the use of three novel technologies for the implementation of wireless green battery-less sensors that can be used in agriculture. The three technologies, namely, additive manufacturing, energy harvesting, and wireless power transfer from airborne transmitters carried from UAVs, are considered for smart agriculture applications, and their combined use is demonstrated in a case study experiment. Additive manufacturing is exploited for the implementation of both RFID-based sensors and passive sensors based on humidity-sensitive materials. A number of energy-harvesting systems at UHF and ISM frequencies are presented, which are in the position to power platforms of wireless sensors, including humidity and temperature IC sensors used as agriculture sensors. Finally, in order to provide wireless energy to the soil-based sensors with energy harvesting features, wireless power transfer (WPT) from UAV carried transmitters is utilized. The use of these technologies can facilitate the extensive use and exploitation of battery-less wireless sensors, which are environmentally friendly and, thus, "green". Additionally, it can potentially drive precision agriculture in the next era through the implementation of a vast network of wireless green sensors which can collect and communicate data to airborne readers so as to support, the Artificial Intelligence and Machine Learning-based decision-making with data. [ABSTRACT FROM AUTHOR]

Unmanned underwater vehicles (UUVs) are key technologies to conduct preventive inspection and maintenance tasks in offshore renewable energy plants. Making such vehicles autonomous would lead to benefits such as improved availability, cost reduction and carbon emission minimization. However, some technological aspects, including the powering of these devices, remain with a long way to go. In this context, underwater wireless power transfer (UWPT) solutions have potential to overcome UUV powering drawbacks. Considering the relevance of this topic for offshore renewable plants, this work aims to provide a comprehensive summary of the state of the art regarding UPWT technologies. A technology intelligence study is conducted by means of a bibliographical survey. Regarding underwater wireless power transfer, the main methods are reviewed, and it is concluded that inductive wireless power transfer (IWPT) technologies have the most potential. These inductive systems are described, and their challenges in underwater environments are presented. A review of the underwater IWPT experiments and applications is conducted, and innovative solutions are listed. Achieving efficient and reliable UWPT technologies is not trivial, but significant progress is identified. Generally, the latest solutions exhibit efficiencies between 88% and 93% in laboratory settings, with power ratings reaching up to 1–3 kW. Based on the assessment, a power transfer within the range of 1 kW appears to be feasible and may be sufficient to operate small UUVs. However, work-class UUVs require at least a tenfold power increase. Thus, although UPWT has advanced significantly, further research is required to industrially establish these technologies. [ABSTRACT FROM AUTHOR]

With the proliferation of electronic devices and electricity-based mobility solutions, the significance of wireless power transfer technology has increased substantially. However, ensuring secure and reliable power transmission to authorized users remains a significant challenge. Addressing this complex issue requires an integrated approach that balances efficiency, stability, and security considerations. While current efforts primarily focus on improving charging efficiency and user convenience, integrating robust security measures into wireless charging infrastructure is challenging due to its inherently open nature and susceptibility to external interference. Technical advancements are required to strengthen the security of the wireless charging infrastructure; however, these should be balanced with power loss management. This study tackles two core issues: the increasing hardware requirements for billing system authentication protocols and the interception of wireless charging signals by unauthorized users, leading to power theft and subsequent losses. To address these challenges, we propose a mechanism termed "LazyFrog". This mechanism dynamically adjusts the frequency hopping schedule, activating frequency changes only in response to detected threats during remote charging or upon identifying unauthorized access attempts. The proposed mechanism compares the expected power reception at the device with the actual power supplied by the charging station, enabling the detection of abnormal power losses. By minimizing unnecessary frequency changes and optimizing energy consumption, LazyFrog reduces hardware requirements. Moreover, we have implemented a relative distance estimation mechanism to facilitate efficient power transfer as wireless devices move within the charging environment. With these features, LazyFrog demonstrates a secure, flexible, and energy-efficient wireless charging system ready for practical application. [ABSTRACT FROM AUTHOR]

This paper investigates the challenges associated with constructing wireless chargers at the megawatt level using inductive power transfer (IPT) technology for marine energy storage systems. For marine applications, charging can only take place at a quay, meaning that only static charging is possible. In this paper, the specifications of the MF Ampere ferry have been used for the feasibility study. Through analytical calculations and PSIM simulation, it was determined that several low-power (100 kW) IPT systems need to be paralleled to achieve 1 MW power transfer. Building a single unit of 1 MW is not feasible due to the voltage and current stress across the components and limited space available onboard and onshore. However, a 100-kW power level can be implemented, despite the involved misalignments, if the primary system is kept stationary with respect to the secondary. Two proposed solutions for implementing a fast charger at the 1 MW level are presented in this paper: 10 units of 100 kW without mechanical mooring assistance or 5 units of 200 kW with mechanical mooring assistance. [ABSTRACT FROM AUTHOR]

It is well known that when applying wireless power transfer technology to energy storage loads, higher-order compensation networks can implement the load-independent output characteristics and simplify the control system. Analysis methods based on the equivalent model can effectively reduce the design complexity of high-order compensation networks. However, additional analysis is required to maintain zero phase angle of input voltage and input current and implement soft switching during the entire charge process simultaneously, when these analysis methods are adopted. Therefore, a composite network model, which is able to systematically analyze the load-independent output characteristics, zero phase angle, and soft-switching conditions of the higher-order compensation network, is proposed in this paper. To verify the reliability and effectiveness of the proposed composite network model, a 100-W lab prototype charger with the double-sided LCC compensation circuit has been built. Moreover, the composite model can be applied to other higher-order networks. [ABSTRACT FROM AUTHOR]

The existing simultaneous wireless power (SWP) and information transfer can only achieve serial signal transmission and it is hard to decouple the power and signal transmission without the additional circuits. To solve these problems, a SWP and multibit signals transfer technology is proposed in this article. Based on the working principle of the hybrid modulation waves pulsewidth modulation control technology, the power and multibit signals are modulated into the system through the modulation waves with different frequencies. Therefore, the signal transmission no longer depends on the power transmission, and the signal transmission rate is multiplied through the realization of parallel signals transmission. Subsequently, the parameter selection criterion of the signal channel is given by analyzing the signal transmission rate and the interference between the power and signal transmission. Finally, the proposed technology is verified with experimental results. The experimental results demonstrate that the power and two-bit signals can be transmitted stably. Compared to the serial transmission, the band signal transmission rate is increased by two times. [ABSTRACT FROM AUTHOR]

For implantable medical devices, it is of paramount importance to ensure uninterrupted energy supply to different circuits and subcircuits. Instead of relying on battery stored energy, harvesting energy from the human body and any external environmental sources surrounding the human body ensures prolonged life of the implantable devices and comfort of the patients. In this article, we present existing issues and challenges related to the state-of-the-art solutions used for harvesting energy to power implantable devices. In addition, the details on existing energy storage technologies and various wireless power transfer techniques incorporating external or internal energy sources and sensors have been discussed. The authors have outlined the performance and power constraints of existing biomedical devices and provided a brief overview of various power architectures found in the literature. This survey has been conducted on existing implantable solutions in terms of output voltage, current, device dimension, application, generated power, energy density, and so on. Finally, the advantages and drawbacks of different solutions have been discussed and compared. Therefore, this article can be considered as an expedient reference for researchers conducting research in the field of energy scavenging, internal energy storage, wireless power transfer techniques, and power management of implantable medical devices. [ABSTRACT FROM AUTHOR]

This paper presents the current state of knowledge in the field of wireless power transfer. The concept of such a transfer and the basic methods of its implementation are described, together with block diagrams of the necessary devices. The technologies of electrical power transfer over short and long distances are characterized. The most popular electrical power transfer technology based on the phenomenon of electromagnetic induction is discussed in great detail. The analysis of the influences of such factors as the coupling factor, the shape of the coils, the type of ferromagnetic material from which the core of the coils is made, and the mutual position of the transmitting and receiving coils are analyzed on the properties of the wireless power transfer system. The advantages and disadvantages of the used technologies are shown. Furthermore, a wireless power transfer system is presented for charging the batteries of electric vehicles. The standards of wireless power transfer are also presented, and development trends are outlined. [ABSTRACT FROM AUTHOR]

Dynamic wireless power transfer (DWPT) has attracted widespread attention for its charging flexibility; short-segmented DWPT systems are more suitable for EV charging scenarios because of their higher charging efficiency and lower electromagnetic radiation, compared to long-track DWPT systems. For short-segmented DWPT systems, the structural design of the ground-side coil affects the coupling characteristics of the system, while simultaneously the electric vehicle driving speed and coil arrangement also cause coupling variations, and this will inevitably have an impact on the system's performance. Therefore, this paper demonstrates the coupler design of a short-segmented system for electric vehicles, focusing on the optimization of ground-side coil. The coupling variations causing by driving speed of EV and coil arrangement are taken into account. Considering the tradeoffs and restrictions, a multi-objective optimization process of coils in DWPT systems is proposed based on the Pareto optimizing method, with three objectives: transfer power, high efficiency and low cost. A reasonable optimal solution is selected from the Pareto front to verify the optimizing method through a constructed prototype. [ABSTRACT FROM AUTHOR]

Wireless rechargeable sensor networks (WRSNs) employ wireless charging transfer technology to provide dynamic energy replenishment for sensors. Previous related research considers enhancing the flexibility of WRSNs with the use of wireless charging vehicles (WCVs). Although this research prolongs network lifetime to some extent, there still exist two essential drawbacks: off-road limitation and traveling speed limitation. Benefiting from the intrinsic flexibility, high flight speed, low cost and small size, wireless charging drones (drones) have great potentials to be used to charge sensors in WRSNs. However, suffering from limited battery capacities, it is impossible to use drones for charging sensors in large WRSNs independently. To conquer the drawbacks of WCVs and drones, we propose a novel WRSN model which integrates WCVs, WCV-carried drones and independent drones to construct an efficient novel charging system. The proposed system, which aims to extend network lifetime and to minimize the time of charging scheduling on premise of satisfying charging requests with the cooperation of WCVs and drones. Thus, we develop a novel charging scheduling scheme, which divides the sensing region into three circular sub-regions for scheduling the WCVs or drones collaboratively. Sensor nodes located in the inner ring are charged by independent drones directly from the base station. Nodes located in the middle ring are charged by WCVs, while the outer ring charged by WCV-carried drones. Simulation results show that our scheduling scheme outperforms multiple WCVs which either employ temporal or distantial priority scheme and earliest-deadline first scheme with respect to the lifetime and network charging efficiency. [ABSTRACT FROM AUTHOR]

Dynamic wireless charging (DWC) is one of the most promising and economical power supply solutions for electric vehicles (EVs), which can address range anxiety and downsize the volume of onboard batteries. To solve the null power phenomenon and transfer power pulsation phenomenon in DWC scheme, this paper proposes a new magnetic coupler array to implement continuous charging and reduce the output power variation. The transmitters are placed with a proper interval to eliminate the adjacent coupling and enlarge the coil array’s effective length. ANSYS Maxwell is utilized to demonstrate the finite element analysis (FEA) of the DWC system. A larger receiver coil is designed to significantly mitigate power pulsation and increase the magnetic coupling as the receiver moves along the array. With the well-designed receiver coil, the output power pulsation is $\pm$ 1.52 $\%$. For the high-power capacity scenario, a multilevel connected DC-DC converter is designed on the receiver side to regulate the transfer power. Besides, a passivity-based control (PBC) is developed for the receiving DC-DC converter based on the Euler-Lagrange (EL) model, and a current sharing compensator is employed to balance each phase inductor current. Finally, a 500- $\text{W}$ prototype is constructed, and experimental results are represented to validate the proposed optimized coil array and the proposed PBC method. [ABSTRACT FROM AUTHOR]

This article proposes an enhanced timely and robust constant current (CC) control for wireless in-flight charging systems. The challenge for practical wireless in-flight charging systems is to maintain a CC output for hovering drones under circumstances of the continuous variation of coupling effect, various charging power requirements, and the parameter shifting, which is nearly unexplored in previous studies on wireless power transfer technologies. In order to address the issue, this article adopts the online-trained radial basis function neural network (RBFNN) to ensure the expected CC output for battery charging, which aims to handle negative impacts of the continuously varied coupling effect, the disturbance of parameters, and the change of charging current. In this article, both simulated and experimental results are given to verify the effectiveness of the proposed control scheme, wherein the accuracy of the controlled output current is within 5% and the average response time is less than 100 ms. It shows that the proposed dynamic-balancing robust current control is an ideal technical solution for wireless in-flight charging of drones by means of remarkable characteristics of the adopted RBFNN-based controller, namely, the increased rapidity and the enhanced robustness. [ABSTRACT FROM AUTHOR]

The misalignment between the transmitting (Tx) coil and the receiving (Rx) coil is an urgent problem in the drone charging system using wireless power transfer technology. The coupling coefficient is so low when the resonance coils is not aligned, which degrades the drone wireless charging performance. In this article, the optimization processes of the coupling mechanism are presented in detail. First, we illustrate the great superiority of unequally spaced Tx coil, compared with traditional uniformly spaced one. Then, a genetic algorithm to optimize the side lengths of the Tx coils is highlighted by discussing the main design considerations and methods in a comprehensive manner. Furthermore, the Rx coil with varying radius size per turn is proposed in terms of the distribution of magnetic field generated by the optimized Tx coil. Experimental results show that the optimized coils have better coupling performance due to small mutual inductance change under the condition of misalignment. Power transfer efficiencies in different misalignment situations are measured and the best power transfer efficiency improvement achieved by the proposed system can reach 56.23% in contrast with traditional coils. This drone charging system can transfer a maximum power of 100 W with the remarkable transfer efficiency of 92.41%. [ABSTRACT FROM AUTHOR]

Recently, more and more unmanned aerial vehicles (UAVs) have been used in industry, public services and commercial fields. However, the UAV is generally limited by the battery capacity, and the operation radius is greatly limited. In this paper, to increase the flight time of the UAV, the recharging station by using wireless power transfer technology is proposed. A new receiver magnetic coupler is given, the receiver coil is wound around the hollow ferrite core, which realizes the strong coupling of the primary and secondary coils, and improves the anti-misalignment ability of the UAV. The weight of the receiver is relatively light, so the effect on the weight bearing of UAV is small. In addition, the compact coil structure is also easy to install on the UAV. The feasibility of the proposed wireless charging method is verified by a 185 W laboratory prototype. The weight of the magnetic receiver is 98 g and the operating distance is 20 mm, with a measured maximum efficiency of 90.40%. [ABSTRACT FROM AUTHOR]

An uninterruptable wireless power supply is developed for a left ventricular assist device (LVAD), which is an implanted, electrically driven centrifugal pump used to treat advanced heart failure pathologies. The LVADs are currently powered through a cable driveline (DL) that exits the patient's body through the skin. Here, an innovative uninterruptable power supply is presented, based on a hybrid wireless/wired architecture: the electric power of 10 W is transferred by the near field wireless power transfer technology operating at 300 kHz, from outside the human body to an implanted subcutaneous receiver, and then by an internal cable to the LVAD. A significant improvement of the subcutaneous receiver is here proposed, based on the integration in the receiving coil of a battery pack providing the following benefits: no-break power supply for the LVAD; peak load management; enhanced system reliability; elimination of DL infection; enhancement of patient's quality of life. The proposed system is first designed and optimized, then a demonstrator is made and tested in a laboratory using the latest LVAD generation. The measured coil currents are used as sources for dosimetric analysis to assess the compliance of the system with the electromagnetic field safety and thermal regulations. [ABSTRACT FROM AUTHOR]

The use of wireless power transfer technology in unmanned aerial vehicle (UAV) systems is rapidly improving in different application areas. The main limitations of electric-powered UAVs are their charging range and stability in dynamic conditions. To solve these, this article proposes a hybrid control method based on dc-link and switched capacitor control with a fixed operating frequency. The dc-link voltage is regulated by the boost power factor correction converter to smoothen the output voltage, and the switched capacitor is used to dynamically compensate for self-inductance variations under dynamic coupling conditions. The output voltage stabilization and near-unity power factor of the input impedance can be achieved by applying the hybrid control method. Therefore, efficiency improvement can be achieved. Furthermore, the proposed control method can also be applied to systems with large coupling variations. To verify the proposed control method, a 500-W prototype was set up in the laboratory, and the experimental results proved that the control method could ensure a stable output voltage with horizontal and vertical offsets of 200 and 62 mm. respectively. Additionally, the results show that the maximum efficiency of the proposed control method is 91.9%, demonstrating that the proposed method effectively improves the efficiency. [ABSTRACT FROM AUTHOR]

In the plant protection drone wireless power transfer system, the positional deviation of the transmitting coils and the receiving coils will cause the efficiency of wireless power transmission drops. In view of this problem, an anti-offset constant current wireless power transfer technology by adjusting the duty cycle of the secondary side buck circuit is proposed in this paper. By establishing a theoretical model of wireless power transfer system for plant protection drone, the relationship between positional deviation and charging current and charging power charging efficiency is analyzed. The magnetic field between transmitting coil and the receiving coil is simulated and compared using Maxwell. In order to further verify the correctness of the theoretical analysis, mathcad is used for simulation analysis. Finally, an experimental platform using the design parameters is built to verify the anti-offset performance. The experimental results show that under different misalignment conditions the charging current can be maintained at 2 A. Compared with the traditional wireless charging system, the system efficiency is improved as much as 3.54%. [ABSTRACT FROM AUTHOR]

The wireless power transfer scheme is based on fractional-order time-sharing control for a variety of household appliances in intelligent building. In the scheme, by adding a fractional-order capacitor in the transmitter, the time-sharing resonant charging is realized without changing the traditional receivers. The wired power transmission is usually adopted to supply power for the devices in the traditional buildings. With the development of intelligent buildings, the way of wired power supply would greatly increase the complexity and consumption of laying the lines. To improve the flexibility of power supply and reduce the cost of wiring, wireless power transfer technology has been used in smart buildings. However, it remains a fundamental challenge to create a simple wireless power transfer system in which power can be wirelessly transferred to multiple appliances. Therefore, this paper proposes a wireless power transfer scheme based on fractional-order time-sharing control for a variety of household appliances in intelligent building. In the proposed scheme, only one fractional-order capacitor in the transmitter is needed to realize the time-sharing resonant charging. In contrast, the traditional multiple-receiver systems require complicated control scheme, for example, controlling a plurality of sets of series-parallel capacitors through a series of relay switches. To demonstrate the method, a 150 W LED TV with 300 kHz and a 5 W mobile phone charger with 127 kHz serve as the actual loads. The experimental results show that the proposed system can supply power to the TV and the mobile phone by a time-sharing way wirelessly. [ABSTRACT FROM AUTHOR]

This paper proposes a quadrature-shaped pickup coil, which can realize an angular-misalignment insensitive omnidirectional wireless charging system. Recently, the three-dimensional wireless charging has shown promising prospects for removing the performance deterioration caused by the positional misalignment, which can transfer power to arbitrary spatial objectives. In the conventional design, the strength and the direction of the induced magnetic field can be adjusted by controlling the excitation currents of transmitting coils. However, the existence of angular misalignment caused by the self-rotation of the pickup unit still can result in a sharp decrease of the transmitted power. Accordingly, this paper proposes and implements a novel pickup coil topology to compensate such huge fluctuations in power transfer, which aims to ensure an angular misalignment insensitive omnidirectional wireless charging. Simulated and experimental results are both given to verify the feasibility of the proposed quadrature-shaped topology. [ABSTRACT FROM AUTHOR]

Breakthroughs in information and power transfer for wireless networks are imperative in order to satisfy the requirement of wireless nodes for energy sustainability. To this end, significant research efforts in academia and industry have been devoted to the design of optimal resource allocation schemes for RF SWIPT networks. The transmit power constraints imposed by safety regulations introduce significant challenges to the improvement of power transfer performance. Therefore, solely relying on RF resources to cope with the expectations of next-generation wireless networks, such as longer device lifetimes and higher data rates, may no longer be possible. Thus, the investigation of technologies complementary to conventional RF SWIPT is of critical importance. In this article, we propose a novel collaborative RF and lightwave power transfer technology for future networks, where both the RF and lightwave bands can be entirely exploited. In this context, we introduce the basic transceiver architecture and four corresponding collaborative communication and power transfer protocols. Finally, key potential future research directions are highlighted. [ABSTRACT FROM AUTHOR]

Current imbalance in multistring light-emitting diodes (LEDs) is a critical issue. It may cause overcurrent in one or more LED strings, leading to rapid degradation. In this paper, a mixed high-order compensation networks-based wireless power transfer system is proposed to generate multiple constant current outputs. It is composed of an LCC resonant network in the transmitting side, a series resonant network, and multiple CLC resonant rectifiers in the receiving side. The CLC resonant rectifiers are connected in parallel to form multiple independent output channels, and each channel is then connected to an LED string. Based on the analysis of the T resonant circuit and the modeling of coupling coils, multiple constant output currents can be derived. As a result, current balance can be achieved, which is very suitable for driving multistring LEDs. The proposed system also offers a modular, scalable, and maintenance-free design, which can significantly reduce the construction cost and the control complexity. In addition, the inverter in the transmitting side can achieve zero phase angle. A laboratory prototype with dual independent output currents is built to verify the proposed method. The experimental results agree well with the theoretical analysis. [ABSTRACT FROM AUTHOR]

In this paper, a novel wireless servo motor drive is proposed and implemented, which artfully integrates wireless power transfer into the dc servo motor drive to achieve wireless bidirectional servo motion. Prominently, there is no power converter or controller at the servo motor side to realize the bidirectional rotation, while the motor control is fully conducted at the transmitter side. The key is to adopt only one transmitter with LCL network to achieve power equalization of two receiver coils, hence realizing bidirectional motion. Meanwhile, the phase-shift control method is newly developed to perform the desired speed control at the transmitter side, without requiring any switched capacitor arrays. As a result, the proposed wireless bidirectional servo motor drive takes the definite advantages of electrocution free and totally sealable. Both calculation and experimental results are presented to validate the feasibility and controllability. For the prototype, the transmission distance can reach up to 130 mm and the transmission efficiency can be up to 85%. [ABSTRACT FROM AUTHOR]

Transfer efficiency is one of the most significant indexes of magnetic coupling wireless power transfer (MC-WPT) systems, which is severely affected by frequency splitting. In this paper, a novel method is proposed for MC-WPT systems to achieve the maximum transfer efficiency by introducing and controlling the circuit detuning factors while maintaining the operating frequency at constant. Firstly, the circuit model of tri-coil MC-WPT systems is established along with the derivation of some key concepts, including the transfer efficiency and circuit detuning factors. Then the analytical expressions of the optimal circuit detuning factors, maximum transfer efficiency and a comprehensive discriminant which could quickly and accurately determine the critical value for every system parameters are derived. Further, the physical interpretation of the maximum transfer efficiency is firstly elucidated from the perspective of energy flow: (1) when the system is in non-splitting region, the energy flow path of the maximum transfer efficiency is transmitter–relay–receiver; (2) when system is in splitting region, the energy flow path of the maximum transfer efficiency is directly from the transmitter to the receiver. Finally, simulation models and practical prototypes are designed to verify the theoretical results. The simulation and experimental results show that the proposed system can maintain an almost constant maximum transfer efficiency over a wide range of transfer distance. The derived discriminant is very useful for guiding the system design in the future, and the energy flow analysis method will be beneficial for maximizing the efficiency for multi-coil MC-WPT systems. [ABSTRACT FROM AUTHOR]

In this paper, we derive formulas that calculate the impedance parameters (Z-parameters) of multiple antennas near objects to analyze wireless power transfer. Furthermore, we propose a method to calculate the impedance parameters of antennas, the maximum power transfer efficiency, and the optimum load impedance of a wireless power transfer system using equivalent current that generate the same electromagnetic field as that generated by an antenna in transmitting mode. [ABSTRACT FROM AUTHOR]

Power allocation is important for dynamic dual-pickup wireless charging system of electric vehicles (EVs). The existing power allocation methods of wireless power transfer technology mainly focus on allocating the power to loads according to the needs with different resonant frequencies. However, the issues of inaccuracy and low power are still not well solved by the existing methods. In addition, the control strategies of existing methods are complex and difficult to implement in practical situations. In this paper, a new power allocation method is proposed, which can dynamically and precisely allocate power to loads. Moreover, the dynamic mutual inductance estimation and the power ratio change between loads are also investigated. In addition, this method has no need to use additional circuits for the receiving coil. Thus, it is convenient to implement in the dual-pickup wireless charging system of EVs. Experimental results have well verified the correctness of the proposed dynamic mutual inductance estimation and power allocation method. [ABSTRACT FROM AUTHOR]

Integral equation (IE) methods have recently been proposed for the modeling of inductively coupled resonant wireless power transfer. These approaches usually result in a low number of degrees of freedom. However, their applicability is mostly limited to homogeneous background media. In the present contribution, integral formulations are extended to take certain foreign objects into account in the model. By using quasi-static approximations, homogeneous foreign objects of canonical shape (e.g., spheres, plates) modify the Green’s function such that it can still be analytically expressed; thus, the computational cost of the IE method remains low. The method is validated against 3-D finite-element simulation and experimental data. [ABSTRACT FROM AUTHOR]

This paper proposes an on-line method for foreign object detection in a double DD coil system. The foreign object is detected by real-time measurement of the mutual inductance between the transfer pads. Measurement of the mutual inductance between coils can be performed at the start, during initialisation, or during the wireless power transfer. The coils in the double DD coil structure can be used separately; one coil can be used for power transfer and the other can be used for the mutual inductance measurement. The mutual inductance measurement is based on the voltage measurement across the open circuit receiver coil. The measured value of mutual inductance between the transmitter and the receiver pad can be used in a control algorithm and in a foreign object detection algorithm. Additionally, a 2DDq coil structure can be used as a replacement for the double DD coil structure, which increases the power transfer density. The DD coils in the double DD coil structure can also be driven using two phase-shifted voltages, which enables better location and detection of foreign objects. The method also helps to differentiate the mutual inductance change due to the distance change from the mutual inductance change due to the presence of a foreign object. [ABSTRACT FROM AUTHOR]

In future, it is expected that RF and infrared-based WPT technology, which are less efficient than the current WPT technology but can wirelessly transmit power over a longer distance, will become more active. Despite several decades of progress in WPT technologies, the inductive WPT system still provides a short transmission distance, as large as the transmitting/receiving coils. RF technologies have been highly anticipated as potentially being able to realize the breakthrough transmission distance. [Extracted from the article]

Wireless power transfer allows the transfer of energy from a transmitter to a receiver without electrical connections. Compared to galvanic charging, it displays several advantages, including improved user experience, higher durability and better mobility. As a result, both consumer and industrial markets for wireless charging are growing rapidly. The main market share of wireless power is based on the principle of inductive power transfer, a technology based on coupled coils that transfer energy via varying magnetic fields. However, inductive charging has some disadvantages, such as high cost, heat dissipation, and bulky inductors. A promising alternative is capacitive wireless power transfer that utilizes a varying electric field as medium to transfer energy. Its wireless link consists of conductive plates. The purpose of this paper is to review the state of the art, link the theoretical concepts to practical cases and to indicate where further research is required to take next steps towards a marketable product. First, we describe the capacitive link via a coupling model. Next, we highlight the recent progress in plate topologies. Additionally, the most common compensation networks, necessary for achieving efficient power transfer, are reviewed. Finally, we discuss power electronic converter types to generate the electric field. [ABSTRACT FROM AUTHOR]

In this paper, we propose a spectrum-sharing protocol for a cooperative cognitive radio network based on non-orthogonal multiple access technology, where the base station (BS) transmits the superimposed signal to the primary user and secondary user with/without the assistance of a relay station (RS) by adopting the decode-and-forward technique. RS performs discrete-time energy harvesting for opportunistically cooperative transmission. If the RS harvests sufficient energy, the system performs cooperative transmission; otherwise, the system performs direct transmission. Moreover, the outage probabilities and outage capacities of both primary and secondary systems are analyzed, and the corresponding closed-form expressions are derived. In addition, one optimization problem is formulated, where our objective is to maximize the energy efficiency of the secondary system while ensuring that of the primary system exceeds or equals a threshold value. A joint optimization algorithm of power allocation at BS and RS is considered to solve the optimization problem and to realize a mutual improvement in the performance of energy efficiency for both the primary and secondary systems. The simulation results demonstrate the validity of the analysis results and prove that the proposed transmission scheme has a higher energy efficiency than the direct transmission scheme and the transmission scheme with simultaneous wireless information and power transfer technology. [ABSTRACT FROM AUTHOR]

Decision-making is an important part of human life and particularly in any engineering process related to a complex product. New sensors and actuators based on MEMS technologies are increasingly complex and quickly evolving into products. New biomedical implanted devices may benefit from system engineering approaches, previously reserved to very large projects, and it is expected that this need will increase in the future. Here, we propose the application of Model Based Systems Engineering (MBSE) to systematize and optimize the trade-off analysis process. The criteria, their utility functions and the weighting factors are applied in a systematic way for the selection of the best alternative. Combining trade-off with MBSE allow us to identify the more suitable technology to be implemented to transfer energy to an implanted biomedical micro device. [ABSTRACT FROM AUTHOR]

The expansion on the use of Electric Vehicles demands new mechanisms to ease the charging process, making it autonomous and with a reduced user intervention. This paper reviews the technologies applied to the wireless charge of Electric Vehicles. In particular, it focuses on the technologies based on the induction principle, the capacitive-based techniques, those that use radiofrequency waves and the laser powering. As described, the convenience of each technique depends on the requirements imposed on the wireless power transfer. Specifically, we can state that the power level, the distance between the power source and the electric vehicle or whether the transfer is executed with the vehicle on the move or not or the cost are critical parameters that need to be taken into account to decide which technology to use. In addition, each technique requires some complementary electronics. This paper reviews the main components that are incorporated into these systems and it provides a review of their most relevant configurations. [ABSTRACT FROM AUTHOR]

The application of wireless power transfer technology in the underwater environment proposes both opportunities and challenges to undersea power feeding. Due to the attenuation of electromagnetic waves in seawater, the distance between transmitter and receiver is always maintained at a minimum value, which results in tight coupling between the transmitter and receiver. The tight coupling condition provides a low impedance loop for high-order harmonic, so the component of the harmonic wave is thus significantly increased and cannot be ignored in the power transmission system. In order to fully utilize the harmonic energy, a fundamental-harmonic dual-channel system was proposed and studied in this paper. Compared with single-channel systems transmitting fundamental wave only, the dual-channel system has higher power transmission capability, while the loss in dual channel system can be less than that of a single-channel system after proper optimization. A 3 kW experiment platform is established to verify the effectiveness of theoretical analysis. [ABSTRACT FROM AUTHOR]

Non-radiative inductive power transfer is one of the most studied and commercially applied wireless charging technologies, where the magnetic field is employed as the medium for power transfer. In the wireless charging of electric vehicles, the strong magnetic field will heat up any metal items falling in the charging area due to eddy current induced in the metal objects, causing hazards like fire. Metal object detection (MOD) is necessary for the market penetration of inductive power transfer technology. This paper aims to improve the performance of systems that detect metal objects based on inductance variations. Two novel multi-layer detection coil layouts are proposed, which can not only cover the entire charging area without blind spots but can also be decoupled from the transmitter and receiver to minimize the influence of the magnetic field that is used for power transfer. Two mixed resonant circuits are proposed and proven to have better performance than parallel and series resonance. The impacts of the detection coil layer, trace width, and turn-number are investigated. The test results indicate that the MOD system can detect one-cent coins at various positions of the detection coil printed circuit board, and can also detect various inductance variations without blind spots in the processing circuit. [ABSTRACT FROM AUTHOR]

The paper describes the sensitivity analysis of a wireless power transfer link involving an implanted antenna within the surrounding biological environment. The approach combines a 3D electromagnetic modeling and a surrogate model (based polynomial chaos expansion). The analysis takes into account geometrical parameters of the implanted antenna and physical properties of the biological tissue. It allows researchers to identify at low cost the main parameters affecting the efficiency of the transmission link. [ABSTRACT FROM AUTHOR]

Electric vehicles have gained more and more attention because of the serious oil crisis and environmental problems. However, the disadvantages of the electric vehicle, such as short driving range, high battery cost, and inconvenient charging, are hindering its market development and expansion. The realization of on-road wireless power transfer technology can effectively solve the problems of short driving range, prevent the battery from being completely discharged to prolong its service life, and reduce requirement of on-board battery. In this paper, the charging mode and the compensation topology of wireless power transfer technology are discussed and then the equivalent circuit model of segmental wireless power transfer system is built. We carried out some magnetic field simulation to analyze how the track shape and length influence coupling coefficient, which is later verified by experiments. [ABSTRACT FROM AUTHOR]

This paper proposes a detailed analysis of the incomplete coupling effect in omnidirectional wireless power transfer systems and a compensation method aiming to improve the transmission performance. Recently, omnidirectional wireless charging technologies have been gradually explored and studied. These charging technologies can transmit power to arbitrary directions in three-dimensional space. However, there are still specific regions where the transmitted power capability dramatically drops to an extremely low level due to the incomplete coupling effect. Accordingly, this paper provides a theoretical analysis and compensation of such an effect. The compensation effectiveness is validated by both a simulation and a 7 W experimental prototype. After the compensation, the transmitted power can be improved by 61% to drive the load in a full range of the space. [ABSTRACT FROM AUTHOR]