Qingxin Yang

Influence Factors Analysis and Improvement Method on Efficiency of Wireless Power Transfer Via Coupled Magnetic Resonance

Wireless power transfer via coupled magnetic resonance has many merits, which has become one of the hot research spots in recent years. The progress of technology in the field of wireless power transfer is remarkable, but its power and efficiency vary with the impacts of the distance, orientation, and center deviation on transmission. To suppress the fast decrease of the transfer efficiency, the equivalent circuit model of wireless power transfer and mutual inductance theory were presented. The results provided critical insight into the design of improving efficiency using a novel method of frequency tracking. The measurement results showed that the efficiency decreased greatly with the distance, orientation and center deviation at fixed-resonance frequency, and the efficiency decreased slowly using adapted resonance frequency. The proposed method is proved through the experiment, and it can provide an effective way to improve the power and efficiency of wireless power transfer.

A novel combination method of electrical impedance tomography inverse problem for brain imaging

A novel method combined differential evolution algorithm and modified Newton-Raphson method is proposed in this paper to solve the electrical impedance tomography (EIT) inverse problem. This method is applied to the two-dimensional impedance reconstruction of brain section based on a four-layer concentric circle model and real head geometric model. Our simulations demonstrate that the novel combination method is robust and time saving in obtaining high-quality reconstruction in EIT problems for brain imaging studied in this paper.

3-D electrical impedance tomography forward problem with finite element method

Electrical impedance tomography (EIT) is a newly developed technique by which impedance measurements from the surface of an object are reconstructed into impedance image. The two-dimensional (2-D) EIT problem is regarded as a simplified model. As 2-D model cannot physically represent the three-dimensional (3-D) structure, the spatial information of the place where the impedance is changed by some diseases cannot be detected accurately. Therefore, 3-D EIT is necessary. In this paper, the finite element method (FEM) of 3-D EIT forward problem is presented. A sphere model is studied. The tetrahedron element is used in the meshing. Two types of sphere model, uniform model and multiplayer model are analyzed. The uniform sphere model, to which the analytical solution is applicable, is used to verify the developed FEM as well as examine the accuracy. The comparison between the numerical solution and the analytical solution shows the correctness of the developed FEM for EIT forward problem. The multiplayer model, four-layer model and three-layer model, is used to investigate the physical potential distribution inside the inhomogeneous sphere model. Reasonable potential distributions are obtained.

Optimization of hysteresis parameters for the Jiles-Atherton model using a genetic algorithm

A dynamic model with hysteretic nonlinearity for magnetostrictive actuators has been established, combined with the Jiles-Atherton model. The hysteresis parameters for the model have been optimized using the genetic algorithm (GA). Simulation and experimental results demonstrated the effectiveness of the model and parameter identification approach.

Magnetostrictive and magnetic properties of the pseudobinary compounds PrxTb1-xFe2 and Pr0.15TbxDy0.85-xFe2

The synthesis and magnetic and magnetoelastic properties of PrxTb1−xFe2 and Pr0.15TbxDy0.85−xFe2 are reported. The study on the crystalline structure, magnetization, and Curie temperature shows that PrFe2 has a lattice parameter of 7.463 A and a magnetic moment of 4.93 μB/f.u. With the addition of Pr, the anisotropy of TbFe2 decreases and the optimal magnetostriction with low anisotropy occurs on the Tb rich side for TbxDy1−xFe2. In addition, measurement of oriented samples has been carried out to analyze the magnetostrictive behavior.

Analysis of Wireless Energy Transmission for Implantable Device Based on Coupled Magnetic Resonance

WiTricity is a new technology for transmitting energy wirelessly via resonant coupling in the non-radiative near-field. In this paper, design of energy transmission system for implantable devices base on WiTricity is performed, the influence of system structural parameters on the energy transmission efficiency is investigated, the relations between the energy transfer efficiency with the transmission distance are analyzed, and also the frequency values of resonant coils with different parameters have been figured out.

Improvement of the element-free Galerkin method for electromagnetic field calculation

The element-free Galerkin method (EFGM) is meshless method, it can solve some problems that the finite element method (FEM) can not solve effectively in electromagnetic field, such as thin plate problems, narrow gap problems, moving conductors, etc. In this paper, an improved formulation of the EFGM is proposed for electromagnetic field computations. Detailed research is conducted on some key problems, such as the selection of the weight function, the treatment of imposing boundary conditions and interface conditions. Finally, numerical examples are cited for demonstration.

Measurement of Soft Magnetic Composite Material Using an Improved 3-D Tester With Flexible Excitation Coils and Novel Sensing Coils

In this paper, accurate measurement of three dimensional (3-D) magnetic properties of soft magnetic composite (SMC) material is carried out by using an improved 3-D tester with adjustable excitation coils and novel sensing coils attached upon the surface of the SMC specimen. Comparing with the conventional 3-D tester operating at 50 Hz, the improved 3-D tester enables measurements over wide frequency range from 2 Hz to 1000 Hz. The relationships between the B vector and H vector are measured under both alternating and rotating flux conditions, and the core loss features are analyzed. These experimental results are crucial for designing new SMC electrical machines, which are expected to operate at 200 Hz or above.

Modeling dynamic hysteresis for giant magnetostrictive actuator using hybrid genetic algorithm

This paper establishes a simple and novel dynamic hysteresis model for giant magnetostrictive actuator by considering the eddy current loss, anomalous loss and structural dynamic mechanical behavior of the actuator. To obtain parameters of the model, a hybrid genetic algorithm is proposed. Comparisons between the experimental and calculated results show the validity and practicability of the model

Coil Design and Efficiency Analysis for Dynamic Wireless Charging System for Electric Vehicles

Wireless charging electric vehicles (EV) is the development trend of EV. However, the battery taken by EVs has the disadvantages of big volume, long time to recharge, and limited driving distance. In this paper, an innovative dynamic wireless charging system based on magnetic coupled resonant power transmission is presented. The transmitting coil of this charging system can selectively turn ON/OFF for charging vehicles while driving. The structures of the transmitting coil and receiving coil are researched and improved. In addition, the dispersed coupling structure named grouped periodic series spiral coupler is proposed, and its characteristics are described. A simulation of coupling coefficients at different D values is carried out. A prototype is built to experiment on the dynamic wireless charging process of EV. Meanwhile, the coil coupling and variation of transmission efficiency are analyzed. The comparison of the experiment indicated that the EV can obtain a stable charging process under 25 mm transmission distance using the improved receiving coil with R:H:D = 4:5:13. Moreover, the dynamic charging process is relatively stable without an obvious fluctuation while passing the interval between two transmitting coils, and the transmission efficiency is promoted by 50%.