scholarly journals A Novel Optimization Method for Halbach Magnet

2021 ◽  
Author(s):  
Wenjuan Jiang ◽  
Junzhou Li ◽  
Didi Sheng
Keyword(s):  
Cross Section ◽  
Permanent Magnets ◽  
Optimization Method ◽  
Magnetic Flux Density ◽  
End Effect ◽  
Halbach Array ◽  
Field Uniformity ◽  
Portable Nmr ◽  
Quality Factor Q ◽  
The Magnetic Field

Abstract Portable nuclear magnetic resonance (NMR) instruments are widely used in many fields. However, the large volume, low uniformity and end effect limits the application of portable NMR instruments. In order to improve the uniformity and compensate the end effect, a Halbach structure with 9-layer permanent magnet is proposed, which is optimized by axially adjusting the magnet height based on the Halbach array principle and Quality factor (Q) is introduced to represent the magnetic field uniformity at both ends of the central cylinder region. Each layer consists of 16 permanent magnets with trapezoidal cross section and the total volume is Φ240 × 141.8 mm. Through simulation, it is found that the final magnetic flux density is 1.09 T and the uniformity is 418 ppm in the central region (Φ20 × 20 mm) of the optimized structure. The proposed structure has the advantages of small size, compactness in structure and homogeneity, which is very suitable for portable NMR systems.

scholarly journals A Novel Optimization Method for Halbach Magnet

2021 ◽  
Author(s):  
Wenjuan Jiang ◽  
Junzhou Li ◽  
Didi Sheng
Keyword(s):  
Cross Section ◽  
Permanent Magnets ◽  
Optimization Method ◽  
Magnetic Flux Density ◽  
End Effect ◽  
Halbach Array ◽  
Field Uniformity ◽  
Portable Nmr ◽  
Quality Factor Q ◽  
The Magnetic Field

Abstract Portable nuclear magnetic resonance (NMR) instruments are widely used in many fields. However, the large volume, low uniformity and end effect limits the application of portable NMR instruments. In order to improve the uniformity and compensate the end effect, a Halbach structure with 9-layer permanent magnet is proposed, which is optimized by axially adjusting the magnet height based on the Halbach array principle and Quality factor (Q) is introduced to represent the magnetic field uniformity at both ends of the central cylinder region. Each layer consists of 16 permanent magnets with trapezoidal cross section and the total volume is Φ240 × 141.8 mm. Through simulation, it is found that the final magnetic flux density is 1.09 T and the uniformity is 418 ppm in the central region (Φ20 × 20 mm) of the optimized structure. The proposed structure has the advantages of small size, compactness in structure and homogeneity, which is very suitable for portable NMR systems.

Improved Configuration of Halbach Magnets with a Homogeneous Magnetic Field for Portable NMR Device

2021 ◽  
Vol 36 (5) ◽  
pp. 548-558
Author(s):  
Yi-Yuan Cheng ◽  
Ming-Yang Su ◽  
Tao Hai ◽  
Ming Hui ◽  
Bao-lei Li ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Fem Analysis ◽  
Pso Algorithm ◽  
Homogeneous Magnetic Field ◽  
Swarm Optimization ◽  
Halbach Array ◽  
Field Uniformity ◽  
Portable Nmr ◽  
3D Finite Element Method ◽  
The Magnetic Field

Halbach array magnets are widely used in portable nuclear magnetic resonance (NMR) devices that the homogeneity of the magnetic field generated by the array affects the imaging quality. In this paper, we propose some improvements to the construction of the Halbach magnets to enhance magnetic field uniformity. Using a Halbach array model comprising 16 magnets, all the calculations are based on 3D finite element method (FEM) analysis and optimized using the particle swarm optimization (PSO) algorithm. Comparisons of the results are shown to support the observations that the optimized and improved constructions can generate a more homogeneous magnetic field.

scholarly journals Design of a New 1D Halbach Magnet Array with Good Sinusoidal Magnetic Field by Analyzing the Curved Surface

Sensors ◽  
2021 ◽  
Vol 21 (7) ◽  
pp. 2522
Author(s):  
Guangdou Liu ◽  
Shiqin Hou ◽  
Xingping Xu ◽  
Wensheng Xiao
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Permanent Magnet ◽  
Flux Density ◽  
Permanent Magnets ◽  
Air Gap ◽  
Curved Surface ◽  
Magnetic Flux Density ◽  
Sinusoidal Magnetic Field ◽  
The Magnetic Field

In the linear and planar motors, the 1D Halbach magnet array is extensively used. The sinusoidal property of the magnetic field deteriorates by analyzing the magnetic field at a small air gap. Therefore, a new 1D Halbach magnet array is proposed, in which the permanent magnet with a curved surface is applied. Based on the superposition of principle and Fourier series, the magnetic flux density distribution is derived. The optimized curved surface is obtained and fitted by a polynomial. The sinusoidal magnetic field is verified by comparing it with the magnetic flux density of the finite element model. Through the analysis of different dimensions of the permanent magnet array, the optimization result has good applicability. The force ripple can be significantly reduced by the new magnet array. The effect on the mass and air gap is investigated compared with a conventional magnet array with rectangular permanent magnets. In conclusion, the new magnet array design has the scalability to be extended to various sizes of motor and is especially suitable for small air gap applications.

Platform Design for Characterizing Shear Force Produced by Magnetized Magnetorheological Fluid

2019 ◽  
Author(s):  
Ping-Hsun Lee ◽  
Jen-Yuan (James) Chang
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Yield Stress ◽  
Flux Density ◽  
Shear Force ◽  
Permanent Magnets ◽  
Magnetic Flux Density ◽  
Finite Element Method Result ◽  
Mr Fluid ◽  
The Magnetic Field

Abstract In this paper we proposed a platform for measuring shear force of magnetorheological (MR) fluid by which the relationship of yield stress and magnetic flux density of specific material can be determined. The device consisted of a rotatable center tube in a frame body and the magnetic field was provided by two blocks of permanent magnets placed oppositely outside the frame body. The magnitude and direction of the magnetic field were manipulated by changing the distance of the two permanent magnets from the frame body and rotating the center tube, respectively. For determining the magnetic field of the device, we adopted an effective method by fitting the FEM (finite element method) result to the measured one and then rebuilt the absent components to approximate the magnetic field, which was hardly to be measured simultaneously as different device setup were required. With the proposed platform and analytical methods, the drawing shear force and the corresponding yield stress contributed by MR fluid could be evaluated in respect to the magnitude and direction of given magnetic flux density with acceptable accuracy for specific designing purposes without a large, complex, and expensive instrument.

scholarly journals Boundary-integral model of permanent magnet of a tube segment as shape

2011 ◽  
Vol 60 (4) ◽  
pp. 413-432
Author(s):  
Krystyn Pawluk ◽  
Renata Sulima
Keyword(s):  
Magnetic Field ◽  
Permanent Magnet ◽  
Permanent Magnets ◽  
Boundary Integral ◽  
General Idea ◽  
Integral Approach ◽  
Integral Model ◽  
Magnetic Flux Density ◽  
The Magnetic Field ◽  
Tube Segment

Boundary-integral model of permanent magnet of a tube segment as shape The magnetic field due to a permanent magnet of a tube-side segment as shape and of radial-oriented magnetization is considered. Such a sheet modelling a single pole of the magnet is used to express the suitable contribution to magnetic quantities. A boundary-integral approach is applied that is based on a virtual scalar quantity attributed to the magnet pole. Such an approach leads to express analytically the scalar magnetic potential and the magnetic flux density by means of the elliptic integrals. Numerical examples of the computed fields are given. The general idea of the presented approach is mainly directed towards designing the magnetic field within the air gap of electric machines with permanent magnets as an excitation source. Other technical structures with permanent magnets may be a subject of this approach as well.

Study on Magnetic Field for Navigation of Articulated Needle

2012 ◽  
Vol 152-154 ◽  
pp. 952-957
Author(s):  
Hua Fang Huang ◽  
Yi Zhong Wang ◽  
Zong Guo Zhou ◽  
Yong Hua Chen
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Flux Density ◽  
Permanent Magnets ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Magnetic Flux Density ◽  
Variable Direction ◽  
The Magnetic Field ◽  
Three Dimensional Space

When the magnetic articulated needle is inserting, the magnetic field which can produce the magnetic force of variable direction is required in order to implement the magnetic navigation in three-dimensional space. The paper puts forward a method for generating three-dimensional magnetic field based on the rotaion and translation of multiple permanent magnets. In this method, multiple permanent magnets form a circumference array. Every permanent magnet can rotate around the spin axis of itself in the array plane and move along the direction vertical to the array plane. Thus, in the array center, a magnetic fied which can produce the uniform magnetic flux density is obtained. The direction of magnetic fied is controllable in three-dimensional space and the magnitude of magnetic flux density is variable in a certain range. The simulations by ANSYS verify the feasibility of the proposed method.

High Efficiency Radial Passive Magnetic Bearing

2010 ◽  
Vol 164 ◽  
pp. 360-365 ◽  
Author(s):  
Krzysztof Falkowski ◽  
Maciej Henzel
Keyword(s):  
Magnetic Field ◽  
Permanent Magnets ◽  
High Efficiency ◽  
Magnetic Levitation ◽  
Magnetic Bearing ◽  
Air Gap ◽  
The Other ◽  
Experimental Setup ◽  
Halbach Array ◽  
The Magnetic Field

Passive magnetic bearing with Halbach array is presented in this paper. The array uses permanent magnets with radial and axial magnetization to augment the magnetic field on one side of the array and cancel it on the other side. The design of the bearing consists of ring-shaped magnets of 60x70 mm and 75x85 mm with different orientation of magnetization. The designed passive magnetic bearing has air gap of 2.5 mm, stiffness 129297 N/m and maximal value of load 200 N. The bearing ensures magnetic levitation and stabilization of rotor in a work point. The paper presents the design of the passive magnetic bearing as well as the experimental setup together with investigation results.

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