Efficiency Of Wireless Power Transmission Research Articles

Modeling and analysis of magnetic resonance wireless transmission coil

Wireless transmission technology is a new type of power transmission technology with electric and magnetic fields as the medium. It has more advantages in transmission direction, transmission characteristics, security, and penetration. The model of a magnetically coupled resonant radio energy transmission system is designed. The main parameters such as resonance frequency and mutual inductance are considered comprehensively. The model is designed using the equivalent topological circuit structure of mutual inductance coupling. The equivalent parameters in the circuit topology can be affected by setting the size of the coil, the distance between the coils, the excitation size, and the high frequency. The structure parameters of the whole system are modeled and calculated by the Ansoft Maxwell software. At the same time, the influence on the power and efficiency of wireless power transmission is explored by several factors such as the coil diameter, the distance between the transmitting end and the receiving end, and the resonance frequency of the system, so as to achieve the purpose of verifying the technical characteristics of wireless power transmission. The key factors that may affect the transmission efficiency and power of the system are analyzed in detail by deriving the calculation model of transmission efficiency and power.

Low complexity on-board vector calibration network for optimal microwave wireless power transmission and enhanced RF-to-DC conversion efficiency

A low complexity on-board vector calibration network for optimal microwave wireless power transmission (MWPT) efficiency is proposed in this work. The proposed technique is based on sequentially tracking the minimum power level of two antenna elements in an array for both phase and amplitude error discrimination. Unlike conventional vector calibration networks based on a down-conversion topology, the proposed architecture can perform vector calibration by only monitoring the magnitude of each antenna element. Thus, high system efficiency can be achieved by reducing hardware costs and eliminating any unnecessary power consumption by extra active devices. Further, phase and amplitude imbalances between antenna elements in an array can be accurately captured with higher precision compared to the conventional rotating-element electric-field vector (REV) method. The proposed technique achieved higher resolutions for both amplitude and phase error detection than REV, which suffers from low resolution near the maximum or minimum field crests. To verify the MWPT efficiency improvement based on the proposed calibration network, a 1 × 4 phased array MWPT system was fabricated and tested at 5.8 GHz with a reference rectenna. With the calibrated power transmission, the total RF-DC conversion efficiencies at ± 45° beamforming angles were improved by up to a maximum of 138.79%.

Wireless Power Transmission Efficiency Improved by Conformal Phase Gradient Metasurface for Implanted Devices

Wireless Power Transmission Efficiency Improved by Conformal Phase Gradient Metasurface for Implanted Devices

Enhancing Wireless Power Transmission Efficiency via Resonant Coupling into Coil and Wire Parameters

The concept of wireless power transmission involves the transfer of electrical energy from a power source to an electrical load without wires. The technology has become widely used in various mobile, industrial, and medical fields. This innovation eliminates the need for wires and batteries, making it a convenient and safe option for all users. Inductive and resonant coupling are the most commonly used methods for wireless power transmission. This work delves into designing and developing wireless power transmission hardware. A wireless power system comprises a transmitter (primary coil) and a receiver (secondary coil). The primary coil produces a magnetic field by passing alternating current through it. The secondary coil is then positioned close to the primary coil. When the two devices make contact, the primary and secondary coils become magnetically linked, causing the power to transfer from transmitter to receiver. To optimize the wireless power transmission using a resonant coupling, the paper tests and analyzes how different wire diameters, coil diameters, and the number of coils affect the output power.

The Efficiency Improvement of Track-Type Wireless Power Transmission Systems through Electromagnetic Finite Element Analysis

The original system, designed as a combination structure of a linear machine and a wireless power transmission transformer, was designed to overcome the limitations of the wired power supply method used for working robots and transportation equipment in existing smart factories, and improvements in magnetic coupling and power transfer efficiency are needed. In this work, we study the efficiency improvement of a system that can supply wireless power to track-type transportation equipment. For this purpose, electromagnetic properties such as magnetic equivalent resistance, inductance, magnetic coupling rate, and core loss are analyzed using the finite element method. In addition, the results of magnetic field finite element analysis are applied in electrical equivalent circuit modeling to analyze the voltage transfer ratio and input/output characteristics of a CLLC resonant converter designed for wireless power transmission. The efficiency improvements of the proposed model are verified through a comparison of experimental and simulation results after fabricating a prototype. From the results of this study, a more optimized wireless power transmission system design based on the analysis results from an electromagnetic perspective can be realized to improve the efficiency of wireless power transmission.

An Efficient Design of Inductive Transmitter and Receiver Coils for Wireless Power Transmission

Wireless power transmission (WPT) is commonly used today in many important daily applications, such as electric vehicles, mobile phones, and implanted medical devices. The transmitter and receiver coils are essential elements in the WPT system, and the coupling coefficient between these coils plays an important role in increasing the power transfer efficiency. In this work, we introduce a new approach to optimizing the coupling coefficient between the transmitter and the receiver coils by changing the geometries and locations of the coil turns. In the optimization process, the geometry of the turns varies from a rhombus to a circular and then a rectangular shape according to a quasi-elliptical parameter value. The Neuman formula is used to calculate the self-inductance, mutual inductance, and coupling coefficient for each specific geometry and turn location. The configuration with the highest coupling coefficient is then selected at the end of the optimization process. The final WPT coils are tested and verified using Ansys software through electromagnetic and AC analysis simulations. The results show that the new approach could achieve smooth and easily manufacturable coils with higher coupling coefficients, thereby increasing the power transfer efficiency of WPT.

Online optimization of intelligent reflecting surface-aided energy-efficient IoT-edge computing

With the tremendous developments of Internet of Things (IoT), IoT devices and applications are imposing progressively higher requirements on computing, communication, and power services. Edge computing in combination with wireless power transmission (WPT) presents a viable solution. By empowering wireless access points (APs) with the capability of computation and WPT, APs can act as both edge computing servers and power stations. To improve the efficiency of data transmission and WPT, the Intelligent Reflective Surface (IRS) technique is adopted to passively beamforming thereby improving the channel condition of the wireless links. In such an IoT-edge system, efficiency and stability are the main concerns in designing a strategy of workload scheduling and resource allocation. In this paper, we propose an online algorithm named LSDR (Lyapunov optimization in combination with semi-definite relaxation) to minimize the total energy consumption while maintaining the system’s stable operation. The system’s stability implies that unprocessed data on the AP is limited and the battery level of each IoT sensor should not be depleted. Without requiring prior knowledge of the statistics of the IoT-edge system, the algorithm can balance the trade-off between system stability and total energy consumption. Through rigorous theoretical analysis and extensive numerical simulations, we demonstrate the effectiveness and efficiency of the algorithm.

Enabling Underwater Wireless Power Transfer towards Sixth Generation (6G) Wireless Networks: Opportunities, Recent Advances, and Technical Challenges

In recent decades, wireless power transfer (WPT) has gained significant interest from both academic and industrial experts. It possesses natural electrical isolation between transmitter and receiver components, ensuring a secure charging mechanism in an underwater scenario. This ground-breaking technology has also enabled power transmission in the deep-sea environment. However, the stochastic nature of the ocean highly influences underwater wireless power transmission and transfer efficiency is not up to that of terrestrial WPT systems. Recently, the research fraternity has focused on WPT in the air medium, while underwater wireless power transfer (UWPT) is challenging and yet to be explored. The major concerns are ocean current disturbance, bio-fouling, extreme pressure and temperature, seawater conductivity and attenuation. Thus, it is essential to address these challenges, which cause a substantial energy loss in UWPT. This study presents a comparison between various WPT techniques and highlights the research contributions in UWPT in recent years. Research and engineering challenges, practical considerations, and applications are analyzed in this review. We have also addressed influencing factors such as coil orientation, coil misalignment and seawater effects in order to realize an efficient and flexible UWPT system. In addition, this study proposes multiple-input and multiple-output (MIMO) wireless power transmission, which can significantly improve the endurance of autonomous underwater vehicles (AUVS). This idea can be applied to the design of an underwater wireless power station for self-charging of AUVs.

Wireless Power Transmission Efficiency of Dipole Array Antenna using a Left-Handed Waveguide Slot Antenna as a Feeder

This paper proposes to transform microwaves for snow melting, which slightly leaking from the slotted waveguide, into electric power using a wireless power transmission technique for effective use. A combination of left-handed and right-handed waveguides is a method to melt snow evenly over a large area using microwaves. The left-handed waveguide, however, has large loss because of stubs. In order to evaluate the effect of the left-handed waveguide’s loss, this paper analyzed the wireless power transmission efficiency when the left-handed waveguide with a slot was set as the power transmission part, and a dipole array was placed above the left-handed waveguide as a power reception unit. The wireless power transfer efficiency was calculated using kQ product from S-parameters that were obtained by using the method of moments. The results clarified that the sum of the maximum efficiencies of the arrayed dipoles could be made larger than the maximum efficiency of one dipole.

Research on circuit analysis and optimization of wireless power transmission system with embedded coil

PurposeThe wireless power transmission (WPT) system with an embedded coil will achieve a more flexible charging operation and higher system efficiency. However, the comprehensive analysis considering cross-coupling for WPT with embedded coil is rarely investigated. This study aims to improve the system efficiency of WPT with the embedded coil based on circuit analysis and optimization of embedded coil loops.Design/methodology/approachThe circuit model of WPT system with the non-resonant compensated embedded coil is developed by taking the cross-coupling of all coils and the circuit compensation degree of the embedded coil into consideration. On the basis of system characteristics analysis, optimization of embedded coil position and non-resonant compensation are proposed to improve the efficiency of WPT system with embedded coil. Experimental studies demonstrate the correctness of theoretical research.FindingsThe WPT system with embedded coil designed by optimizing the position and non-resonant compensation achieves higher efficiency than those of the system with two-coil mode and the three-coil system with a resonant compensated embedded coil.Practical implicationsA WPT system with embedded coil could be more efficient by using a non-resonant compensated coil embedded into the buffer material of the storage box for sophisticated electrical equipment.Originality/valueThe cross-coupling between all coils is considered in circuit analysis for WPT system with embedded coil. Optimization of the position and non-resonant compensation of embedded coil achieves higher efficiency.

Optimization of Electric Vehicle Wireless Power Transmission Efficiency Based on Ant Lion Optimizer

<div class="section abstract"><div class="htmlview paragraph">Magnetically coupled resonance wireless power transmission technology (MCR-WPT), as a technological innovation in the electric vehicle industry, is of great significance to promote the development of the electric vehicle industry chain. The current wireless charging technology is affected by the design of the vehicle itself, the distance between the vehicle-mounted part of the wireless charging and the ground is not fixed. And the changeable parking attitude will cause the projection of the transmitting coil and the receiving coil to deviate. Therefore, reasonable matching of transmission frequency, matching impedance and other parameters is of great significance for optimizing power transmission efficiency. This paper establishes a mathematical model of transmission frequency, matching impedance, distance between two coils and wireless power transmission efficiency. Based on the preliminary analysis of 10 experimental data of wireless charging in the laboratory under different coil spacings, the relationship between various parameters and wireless charging efficiency is obtained. In view of the problem of coil offset under actual charging conditions, a nonlinear optimization model for maximizing the efficiency of the MCR-WPT system is proposed. The selected optimization parameters are parameters such as transmission frequency and matching impedance. The goal is to ensure the maximum value of automotive coil offset under high transmission efficiency. In this paper, the optimization model is solved based on the Ant lion optimizer, and the optimal parameter values under the specified working conditions are obtained, and the relative error is less than 3%. When the coil spacing is 10mm, the maximum offset of the coil with a transmission efficiency higher than 80% is 0.3423m, and the RMSE between theoretical and experimental results is less than 0.015. Algorithm optimizes the power transmission efficiency and improved the fault tolerance rate of wireless charging system during parking.</div></div>

An Optimal Design Method for Improving the Efficiency of Ultrasonic Wireless Power Transmission during Communication.

Due to the excellent directivity, strong penetrability, and no electromagnetic shielding effect, ultrasonic waves have good potential for wireless energy transmission and information transfer inside and outside of sealed metal devices. However, traditional ultrasonic based energy transmission methods usually result in considerable energy consumption because of the impedance mismatch during the impedance modulation of the communication. This paper presents an optimal design method for efficient energy transfer during ultrasonic communication. The channel equivalent circuit model is established by only using the acoustic-electric channel scattering parameters. According to the equivalent circuit model, the channel impedance matches with a weak mismatch state is performed during the communication. In this way, the impedance modulation effect is ensured with a lower decrease in the energy transmission efficiency. Finally, the simultaneous energy transmission and impedance modulation are carried out through the 11 mm thick 304 stainless steel plate. The transmission power is 37.86 W with a transmission efficiency of 45.75%, and the modulation rate is 10 Kbps. Compared with the traditional methods, our proposed energy transmission efficiency is increased by 17.62%. The results verify the proposed method’s effectiveness and the high accuracy of the model. The proposed method has great engineering applications and broad prospects in condition monitoring of metallic environments.

Wireless power transfer system based on frequency and impedance matching hybrid adjustment against system detuning

System detuning caused by a variation in the distance between the transmitting and receiving terminals can greatly reduce the transmission power and efficiency of a magnetic resonance-coupled wireless power transmission (WPT) system, which limits the WPT application scope. This paper proposes a magnetic resonance coupling wireless power transmission system, which is based on jointly and continuously adjustable frequency compensation (CAFC) and two-transistor-controlled variable capacitor circuits (TCVCs). Therefore, this system can reach the resonant state by using CAFC and two-TCVCs when the transmission distance is changed. The proposed system can adaptively adjust combinations of the operating frequency and equivalent compensation capacitor’s capacitance to achieve impedance matching avoiding the phase difference caused by the imaginary part of the impedance, thus maintaining stable transmission efficiency under the condition of transmission distance variation. Compared to the traditional magnetic coupled resonant circuit based on impedance matching or variable resonant frequency, the proposed system achieves higher efficiency and stability and dynamic distance adaptation.

Structure and circuit solution of a wireless power transfer system for application in mobile robotic systems

This paper presents the development of a medium-power wireless power transmission system for use in robotics and other applications. The presented system can be used to power devices or charge batteries. The system is based on the principle of inductive power transmission. A feature of the system is the use of a resonant self-oscillator, for which the transmitting LC circuit of the system is a frequency setting. The use of identical receiving and transmitting resonant circuits makes it possible to refuse additional frequency control devices in the receiving part of the system. The presented circuitry solution of the wireless power transmission system ensures operation in the resonance mode in the receiving and transmitting circuits, where the receiving and transmitting coils are at various positions relative each other, while not requiring a dedicated monitoring and control system for this. Experimental verification of the proposed solution was carried out on a prototype of a system with shell elements, shielding from magnetic fields, while the maximum level of efficiency of the system without an output stabilizer in the receiving part was 80.41%, with a transmitted power of 131.5 W, at a transmission distance of 15 mm. The dependency curves of the efficiency and the transmitted power were obtained for three distances of energy transfer — 0 mm, 15 mm and 30 mm. With distances between the coils up to 30 mm, the efficiency of the system is above 70% with a transmitted power of more than 55 W. Key words Wireless charging system, wireless power transmission, resonant oscillator, wireless power transmission efficiency. Acknowledgements This research is supported by the RFBR, project no.19-08-01215_А.

Magnetic Force Calculation of Movable YBCO Superconducting Helical Coils Applicable to Electric Vehicles Wireless Power Transfer

Background and Objectives: Today, replacing gasoline-powered vehicles with electric vehicles (EVs) and connecting them to an electric power source have made the optimal usage of energy-saving resources. Therefore, wireless Power Transfer (WPT) outstands as an alternative technology to improve the user perception about the charging process of the EVs. Superconducting coils (SCs) with high-temperature have an applied feature in decreasing losses of wireless power transmission (WPT). The Magnetic force has effects of overall deformation modes between two current carrier superconducting coils, i.e. axial extension, torsion, and bending. Coil misalignment is a fundamental problem and its impact on wireless power transmission efficiency is very complex. The analysis of a magnetic force which is presented in this paper are beneficially for the design and application of the WPT systems. Here, a fast analytical solution is presented to obtain the magnetic force between the transmitter and receiver helical superconducting coils in different positions.Methods: In this paper, a new method applied to solve the numerically magnetic force solutions in different superconducting coils mismatch states for WPT. Finally, for improvement of efficiency, the WPT system has been designed on the basis of mutual inductance changes which receiving helical coil was moved inside the transmitting helical coil. Hence, the magnetic force calculation of movable YBCO superconducting helical coils inside each other is presented. These models have been compared with the FEM.Results: Results show that the presented equations are reliable as well. According to the comparing the analysis and FEM data, the obtained results indicated the errors with less than 0.0064%. Also, results show an excellent agreement with respect to the finite element method.Conclusion: In this paper, the numerical solutions of magnetic force in different superconducting coils mismatch states were solved by a new method. The magnetic force analysis basics introduced in this paper are useful to develop and apply for wireless power transmission system. The simulation results show that only by applying some constraints, the efficiency of the transmitted wireless power will be optimized. Then, analytical models have been presented which make it possible to calculate the axial force which was exerted between two axially Helical magnetized and two thin coils in air. Also, the analytical stiffness calculation applied between these distributions of magnetic source has been presented. These models have been compared with the FEM to show an appropriate consistency.

High-efficiency and compact WPT receiving antenna design using simulation optimization method

In this paper, a high-efficiency and compact wireless power transfer (WPT) receiving antenna using an flexible printed circuits board (FPCB) with high-Q factor is proposed. The proposed high-efficiency and compact WPT receiving antenna consists of a spiral structure, a lumped element and via through the ground structure. In this paper, in order to design a miniaturized high-efficiency WPT receiving antenna, machine learning technology was used to optimally design the antenna pattern that affects the Q factor. The designed receiving antenna has improved wireless power transmission efficiency with high Q characteristics. The power transfer efficiency is above 88% from distance 10 mm and the resonant frequency is 110 MHz. The sizes of the receiving antenna and the NFC antenna are 30 × 40 mm and 20 × 30 mm, respectively. Machine learning was used to design and fabricate the composite module of a WPT receiving antenna and NFC antenna. Comparison of the experimental results of the proposed receiving antenna with a general receiving antenna confirms the improvement in transmission efficiency.

Research on Tradeoff between Power and Efficiency of Wireless Power Transfer via Magnetic Resonance Coupling

Focusing on the tradeoff problem between the output power and transmission efficiency of magnetic coupling resonance wireless power transmission (MCRWPT) system, this paper firstly analyzes the series–series topology system by using the mutual inductance theory of concentrated parameters, and proposes the concept of power-efficiency composite function by using the method of normalization of output power and then the WPT system is assigned a weight factor. Based on that, the calculation expression of the optimal resonant frequency is obtained. The correctness of theoretical analysis is verified by simulation and experimental platform, which provides a useful reference for further improvement of power-efficiency synchronization and energy saving.

Enhancement of Wireless Power Transmission Efficiency and Flexibility via an Optimized Three-Dimensional Coupled Magnetic Resonance System with Double Transmitter Coil

Wireless power transmission (WPT) has gained considerable attention in recent years due to its convenience. Moreover, various research especially 3D coil structure studies in WPT are emerging through continuous research. However, most of these power sources are too volumetric to charge mobile devices, and the recently proposed 3D couple magnetic resonance system (CMRS) represents not only a lower power transmission efficiency (PTE) than the 2D system, but the PTE decreases sharply as the distance between the coils increases. To improve these drawbacks, this study proposes a novel approach to power mobile devices using a 3D spiral coil structure and a double transmitter coil system simultaneously. The mathematical model is presented, and three different coil structures are designed to evaluate the most power-efficient 3D coil structure. The proposed model is obtained and verified based on the simulation and experiment results. The result showed that when the distance between coils is the closest (8 mm), the PTE was 55.77%, which is improvement compared to that of the pervious 3D CMRS studies. Moreover, the PTE did not decrease sharply since our proposed system has the double resonance frequencies. Mathematical model, simulation, and experiment are provided to verify the feasibility of the proposed model.

Transfer Efficiency of Underwater Optical Wireless Power Transmission Depending on the Operating Wavelength

Optical wireless power transmission (OWPT) is a good candidate for long-distance underwater wireless power transmission. In this work we investigate the transmission efficiency of underwater OWPT, depending on the operating wavelength. We consider four operating wavelengths: infrared, red, green, and blue. We also consider the cases of pure water and sea water for the working conditions. Our results show that it is necessary to select the operating wavelength of underwater OWPT according to the transmission distance and water type of the target application.

Design and testing of a novel gastrointestinal microrobot.

In order to improve the reliability, safety and whole digestive applicability of the gastrointestinal microrobot (GMR), a novel inchworm-like GMR is proposed in this paper. The expanding mechanism of the robot adopts an overlapping expanding arm structure. This structure increases the variable diameter ratio (ratio of fully expanded diameter to fully folded diameter) of the robot to 3.3, making the robot more applicable to the intestines in various parts of the human body. The mechanical model of the expanding arm is established, and the expanding force at different expanding radii is obtained. And then the expanding force is tested by a force test platform. The force test results: the maximum expanding force is 6.5N, and the minimum expanding force is 1.3N. The trend of the experimental and theoretical values is the same, and the experimental value is less than the theoretical value. A position limiting device based on Hall sensor is designed, which detects whether the mechanism reaches the limit position by non-contact method. This device alleviates the problem of sharp voltage drop caused by motor stall and improves the stability of the control circuit. The results of the Hall-type position limiting device (HPLD) testing show that the working currents of the expanding mechanism and the telescoping mechanism with HPLD are respectively 0.066A and 0.110A, and the robot control circuit works stably. Finally, the robot is tested in the intestine of the living pig, and the safety and reliability of the robot are verified. However, due to the decrease of the efficiency of wireless power transmission in vivo experiments and the change of the position of the receiving coil relative to the transmitting coil, sometimes the power supply is insufficient.