Halbach Permanent Magnet Research Articles

No-Load Analysis of PMLSM With Halbach Array and PM Overhang Based on Three-Dimensional Analytical Method

This paper presented a 3-D analytical method, based on transfer relations for permanent-magnet (PM) linear synchronous machine (PMLSM). The PMLSMs in this paper have a double-sided mover structure with Halbach array PMs and a slotless stator core. In addition, in order to complement the leakage and fringing flux density, we use a PM overhang in the mover structure. The analysis of this method's phenomenon is the proposed 3-D analytical method in this paper. Furthermore, we present experimental verification using a prototype model.

A Compact Hydrostatic-Driven Electric Generator: Design, Prototype, and Experiment

This paper presents an integrated hydrostatic-driven electric generator, which can be employed to convert hydrostatic energy to electrical form directly. The machine with compact structure is realized by mounting a Halbach permanent magnet array which has self-shielding magnetic property on the barrel surface of an axial piston hydrostatic motor. A stator consisting of iron core and windings is installed concentrically on the outside of the permanent magnets. Then, according to electromagnetic theory, electrical power will be generated when the barrel and the magnets are driven to rotate by pressurized fluid. Parametric constraints required by the integration are analyzed and tradeoff designs of some significant parameters are implemented by using theoretical analysis and finite-element analysis. A prototype is fabricated based on the utilization of some standard parts, and tested under both of no-load and loaded conditions. The results demonstrate that the prototype has expected performances including small volume and moment of inertia, reasonable efficiency, as well as good output voltage stiffness and generation quality.

Unbalanced Magnetic Torque in Electrohydraulic Energy Conversion Unit Considering Rotor Axis Deflection

An integrated electrohydraulic energy conversion unit is designed by mounting a Halbach permanent magnet array on the rotor surface of an axial piston hydraulic pump/motor. Since the rotor is not completely fixed as required by hydraulic principle, there exists a deflection angle between the rotor and the stator when the machine is in operation, which causes unbalanced magnetic torque acting on the rotor. This paper focuses on the calculation and characteristic investigation of the magnetic torque. According to the analytical expression, a simplified calculation is realized through the finite-element analysis on 2-D cross section, and compared with the 3-D finite-element calculation. Parametric effects on the magnetic torque are presented, such as deflection angle, iron core length, and air-gap length. The results can be employed to further study the machine’s rotor dynamics and provide reference to other permanent magnet machines having similar problems.

Application of a Halbach magnetic array for long-range cell and particle separations in biological samples

Here, we describe a versatile application of a planar Halbach permanent magnet array for an efficient long-range magnetic separation of living cells and microparticles over distances up to 30 mm. A Halbach array was constructed from rectangular bar magnets using 3D-printed holders and compared to a conventional alternating array of identical magnets. We theoretically predicted the superiority of the Halbach array for a long-range magnetic separation and then experimentally validated that the Halbach configuration outperforms the alternating array for isolating magnetic microparticles or microparticle-bound bacterial cells at longer distances. Magnetophoretic velocities (ymag) of magnetic particles (7.9 μm diameter) induced by the Halbach array in a microfluidic device were significantly higher and extended over a larger area than those induced by the alternating magnet array (ymag = 178 versus 0 μm/s at 10 mm, respectively). When applied to 50 ml tubes (∼30 mm diameter), the Halbach array removed >95% of Staphylococcus aureus bacterial cells bound with 1 μm magnetic particles compared to ∼70% removed using the alternating array. In addition, the Halbach array enabled manipulation of 1 μm magnetic beads in a deep 96-well plate for ELISA applications, which was not possible with the conventional magnet arrays. Our analysis demonstrates the utility of the Halbach array for the future design of devices for high-throughput magnetic separations of cells, molecules, and toxins.

Partitioned stator flux reversal machines having Halbach array PMs

Purpose – In this paper, the partitioned stator flux reversal permanent magnet (PM) (PS-FRPM) machines with Halbach array PMs are investigated to compare with the machine having the conventional parallel magnetized PMs, and conventional FRPM machine. This paper aims to discuss these issues. Design/methodology/approach – The Halbach array PM machines with 2-, 3-, and 4-segment and ideal Halbach array PMs have similar topology and designed based on the PS-FRPM with parallel magnetized PMs. The open circuit analysis and electromagnetic performance has been calculated and compares with the aid of finite element (FE) method, and validated by experiments. Findings – The PS-FRPMs with Halbach array PMs have higher back-EMF and torque performance, as well as lower cogging torque and torque ripple, all having significantly higher torque density than the FRPM machine with single stator. The experimental results and FE predicted results of the 2-segment Halbach PM prototype machine are compared and good agreement is achieved. Originality/value – This paper introduces the new concept and design of PS-FRPMs having Halbach array PMs with different PM segments and idea PM array. The comparison with conventional FRPM and PS-FRPM with parallel magnetized PMs shows the benefits with PS-FRPMs with Halbach array PMs.

COMPARISON, WITH AN ANALYTICAL OPTIMIZATION PROCESS, OF TWO SYNCHRONOUS HALBACH PERMANENT MAGNET MACHINES, FOR A DIRECT DRIVE STICK APPLICATION

This paper deals with the comparison of two actuators with different frameworks, for a direct drive active stick application. Each actuator will be compared with three different sets of specifications which impose many constraints as: high torque, small volume, low temperature, etc. The high required torque per unit of mass and the small volume allowed involve the use of synchronous Halbach permanent magnet (PM) topologies which have the best torque performances. In this article, an analysis and a comparison of two optimized actuators designed with a Halbach configuration are done. It is a linear actuator and a double airgap rotating actuator. The electromagnetic torque is calculated by the Laplace force for which the flux density generated by the Halbach PM configuration is defined by a Laplace equation and a Poisson equation. An analytical optimization under a set of nonlinear constraints will be realized with the analytical expressions of the torque we got previously. In order to validate the analytical model, finite-element analysis (FEA) simulations will be performed on the optimized structure. Finally, two actuators will be compared in order to give the best compromises for the stick application for each set of specifications.

Design and Control of a Six Degrees-of-Freedom Magnetically Levitated Positioning System

Abstract: Magnetic levitation technology is a promising solution to achieve ultraprecision motion in vacuum environment as it is with the characteristics, e.g., non-contact, frictionless, and unlimited stroke. This paper presents the design and control of a six Degrees-Of-Freedom (DOF) magnetically levitated (maglev) positioning system. The maglev positioner is implemented by using four groups of Halbach permanent magnet arrays and coil stators. Through energizing the three-phase current in four coil arrays, the six DOF Lorentz force will be generated in the translator of the maglev system to conduct positioning. To control the maglev positioning system, the controllers of X and Y -axes are designed and optimized according to the specifications characterizing on the closed-loop performance of the maglev system, where the specifications are formulated as the linear matrix inequalities (LMIs) in the constrains of the created optimization. Finally, the experiments are conducted on the maglev prototype to demonstrate its positioning performance of the maglev positioning system.

A novel design and control solution for an aircraft sidestick actuator based on Halbach permanent magnet machine

This paper is concerned with the design and control of a new sidestick actuators used to handle a civilian aircraft behaviour. Indeed, a discrete robust adaptive sliding mode control for a new designed aircraft sidestick based on synchronous Halbach permanent magnet machine. The main objective is to provide a new design structure and a control solution that ensures maintaining high performance specifications for the actuator and respects the set of constraints required by the considered aeronautical application. Indeed, this study achieved in a partnership with an industrial center of excellence for Fly by Wire Cockpit Controls (side sticks, rudder controls, thrust controls), proposes a novel design that enhances the characteristics of the actuator’s structure and the human machine interface between the pilot and the aircraft. Then, a new control strategy is proposed to optimize the efficiency of this actuator for the considered application. It is based on a discrete optimal adaptive sliding mode control considering time delays and uncertainties in the model by using a delay ahead predictor. The proposed strategy combines an optimal sliding mode surface with the delay ahead predictor in an adaptive control structure. Indeed, a varying parameter is used to achieve an ”on-line” adaption to the varying level of disturbances that affects the system. Then, since the sidestick actuator is designed to handle an aircraft displacement, the proposed control strategy is designed for position tracking. Simulations performed on the previously designed actuator prove the efficiency of the proposed technological solution for aircraft position control.

Design and Analysis of a Halbach Magnetized Magnetic Screw for Artificial Heart

Due to the limited number of the donor hearts, artificial heart (AH) systems are required for the therapy of the terminal heart diseases [1]. Existing electric-drive AHs employ the rotary blood pumps or linear motors, but suffering from blood damage and poor thrust density, respectively [2]. Very recently, the concept of magnetic screw was proposed. The magnetic screw actuator integrated with permanent magnet (PM) brushless machine is capable of converting rotational motion into linear motion and vice versa [3]. Since it offers high force density, wear-free, small size and light weight, magnetic screw actuator has a bright future in AH applications. The purpose of this paper is to propose and analyze a new magnetic screw with the halbach PM array [4], which offers improved force density.

Analysis and Optimization of a Double-Sided Air-Cored Tubular Generator

Compared with the slotted tubular generators, air-cored tubular generator has no attraction force, smaller thrust ripple and lower moving mass. The advantages of high respond speed and high output stability make the air-cored tubular generators to be research focus in recent years. It is used in energy conversion systems of ambient vibrations, free-piston engine, ocean wave energy and so on. And in order to overcome the disadvantage of low power density caused by high equivalent air-gap, a tubular generator with double-sided permanent magnet (PM) arrays is proposed. The construction of the tubular generator topology is shown in Fig.1. The two sets of the corresponding Halbach PM array in the stators can help to increase the flux density in the air-gap to enhance the electromagnetic force and power density of the generator. In [1], an equivalent magnetic circuit model of the generator was established and basic characteristics were analyzed. In [2], the force characteristics of the generator with different phases were compared and the influence of the dimensions on the forces was analyzed.

Design and characteristics analysis of linear oscillatory actuator with ferrite permanent magnet for refrigerator compressor

Actuators using NdFeB permanent magnets (PMs) are widely used, but they are costly and are affected by unstable material supply. In this study, a linear oscillatory actuator (LOA) using a ferrite PM is designed for use in the compressor for refrigerators, instead of the NdFeB PM. In spite of benefits of ferrite PM, it has not been widely used because the residual magnetic flux density of the ferrite PM is normally 35% less than that of a NdFeB PM. To overcome this shortcoming, we analyze the mover features of the LOA using two types of the ferrite PMs: interior PM type and Halbach PM type. The LOA designed has the same outer stator outer radius and number of coil turns as a conventional LOA with the NdFeB PM. The validity of the designed model is verified by comparing the analysis results using the nonlinear finite element method.

Coupling effects of a novel integrated electro-hydraulic energy conversion unit

Electro-hydraulic power units are key components of hybrid driven mobile machines such as forklifts and excavators. To satisfy the requirement of limited installation space, this paper proposes a compact and reversible electro-hydraulic energy conversion unit which is the integration of an axial piston hydraulic pump/motor and an electrical machine excited by a segmented Halbach permanent magnet array. The magnets are fixed on the surface of a barrel so that the hydraulic rotor and the electrical rotor are integrated together. Analytical and numerical methods are used to investigate the coupling issues including the common rotor's effect on flux density distribution, combined torque ripple, flow and energy losses in the oil gap, and some design criteria are presented to provide further development with references.

MODELING AND ANALYSIS OF HALBACH MAGNETIZED PERMANENT-MAGNETS MACHINE BY USING LUMPED PARAMETER MAGNETIC CIRCUIT METHOD

Permanent-magnets (PMs) with tangential and parallel magnetization directions are combined in the Halbach PM (HPM) machine, which can offer high performances. However, the existing lumped parameter magnetic circuit (LPMC) model can only calculate one PM magnetization direction, namely either tangential direction or parallel direction. The key of this paper is to propose a method to divide and establish equivalent magnetic motive force (MMF) for HPM machine with both tangential and parallel magnetizations. Then, a LPMC model, using equivalent MMF, is developed to predict the electromagnetic performances for a four-phase HPM machine. In order to verify the effectiveness of the proposed LPMC model, a 6-pole/8-slot 15 kW HPM prototype is built. The comparative results of the proposed LPMC model, two-dimensional (2D) FEM and the experiments verify the effectiveness of the proposed LPMC model.

Modeling of a Two Degrees-of-Freedom Moving Magnet Linear Motor for Magnetically Levitated Positioners

This paper presents a novel analytical model that accurately predicts the current-force characteristic of a 2 degrees-of-freedom moving magnet linear motor (MMLM), where its translator is formed by a Halbach permanent magnet (PM) array. Unlike existing theoretical models, the uniqueness of this proposed model is based on a derived magnetic field model that accounts for the magnetic flux leakage at the edges of the Halbach PM array. Hence, it can be used to model an MMLM that employs a low-order Halbach PM array effectively. To implement the proposed model in high sampling rate control system, a model-based approximation approach is proposed to simplify the model. The simplified model minimizes the computation complexity while guarantees the accuracy of the current-force prediction. MMLM prototype with two separate translators, i.e., one with a single magnetic pole Halbach PM array and the other with six magnetic poles Halbach PM array, were developed to evaluate the accuracy of the proposed models.

Research on Distributed Magnetic Circuit Calculation of Halbach Magnetized Permanent Magnet Generators

Because of the flexibility and clear physical concept, magnetic circuit calculation method (MCCM) is preferred during the early stage of the electromagnetic design of generators and motors. Based on the analysis of magnetic field distribution in halbach magnetized permanent magnet generator (HMPMG) by finite element method (FEM), this paper proposes a distributed magnetic circuit calculation (DMCC) for HMPMG. Because of the low permeability of permanent magnet (PM) material, the DMCC for HMPMG is quite different from that for electrical excitation generator. By dividing half-pole generator model into sub-sections along radial and circumferential direction with circumferential equi-interval nodes in air gap, the DMCC for HMPMG employs iteration to calculate magnetic flux density on air gap nodes. In the end, the validity and accuracy of DMCC are proved by FEM.

Cost Reduction of a New Fault-Tolerant Halbach Permanent Magnet Machine Using Ferrite Magnet

In the permanent magnet (PM) machines, the Halbach PM (HPM) machine can offer higher performance than others, while they require more rare-earth PMs. Due to the high price of rare-earth PMs, such as NdFeB and SmCo magnets, the cost has become a serious drawback of the HPM machine. To overcome this disadvantage, a new fault-tolerant HPM (FTHPM) machine by mixing rare-earth PM and ferrite magnets is proposed in this paper. The proposed machine can be a good candidate for many applications because of low price and stable supply of ferrite magnets. Furthermore, the lumped parameter magnetic circuit method is used to analyze the proposed FTHPM machine. In addition, the finite element method is adopted to verify the effectiveness of the theoretical analysis.

The Effect of Magnet Magnetization Vector Orientation in Halbach Arrays on the Effectiveness of Separation

Magnetic separation is one of the methods that are used to separate magnetic and non-magnetic components from an input mixture. Its e ectiveness strongly depends on the strength and distribution of magnetic eld in the separator. It is economical to use Halbach permanent magnet arrays to create a suitable magnetic eld, since they do not change their properties during separation and do not need electrical energy. During real magnetization process, however, there can be a problem with correct orientation of their magnetization vector. The work based on 2D computer models shows the in uence of di erent orientations of magnetization vectors of individual elements of Halbach arrays on the size and distribution of the magnetic eld in the considered separator space. Several model systems that contained four to six typical AlNiCo, SmCo and NdFeB cube shaped magnets with the dimensions 50×50×50 mm were used for the analysis.

Design and Experimental Analysis of AC Linear Generator With Halbach PM Arrays for Direct-Drive Wave Energy Conversion

To convert wave energy into more suitable forms efficiently, a single-phase permanent magnet (PM) ac linear generator directly coupled to wave energy conversion is presented in this paper. Magnetic field performance of Halbach PM arrays is compared with that of radially magnetized structure. Then, the change of parameters in the geometry of slot and Halbach PM arrays' effect on the electromagnetic properties of the generator are investigated, and the optimization design guides are established for key design parameters. Finally, the simulation results are compared with test results of the prototype in wave energy conversion experimental system. Due to test and theory analysis results of prototype concordant with the finite-element analysis results, the proposed model and analysis method are correct and meet the requirements of direct-drive wave energy conversion system.

Levitation Force Investigation of Bulk HTSC Above Halbach PMG with Different Cross-Section Physical Dimensions by 3D-Modeling Numerical Method

The levitation force of a bulk high temperature superconductor (HTSC) over Halbach permanent magnet guideways (PMG) with different cross-section configuration is studied by numerical method. The Halbach PMG is composed of three host permanent magnets (HPMs) and two slave permanent magnets (SPMs). One cylindrical bulk HTSC with a diameter of 30 mm and height of 15 mm is used. The 3D-modeling is formulated by the H-method. The numerical resolving codes are practiced using finite element method (FEM). The E-J power law is used to describe the electric current nonlinear characteristics of bulk HTSC. By the method, the influence of the cross-section physical dimensions of Halbach PMG on the levitation forces of bulk HTSC levitated above the PMG is studied. The simulation results show that increasing the width of SPM ( $$W_\mathrm{SPM})$$ can enhance the bulk HTSC levitation performance immediately under the condition of keeping the ratio of $$W_\mathrm{HPM}$$ ( $$W_\mathrm{HPM}$$ : the width of HPM) to $$W_\mathrm{SPM}$$ between 1.6 and 1.8, the ratio of td (the height of the PMG) to $$W_\mathrm{HPM }$$ between 1.2 and 1.4. By the method, the bulk HTSC better levitation performance can be expected.

Determination of Quality Parameters for Mustard Sauces in Sealed Packets Using Time-Domain Nuclear Magnetic Resonance Spectroscopy and Chemometrics

Nowadays, most analytical methods used in the quality control of food products are based on wet chemical methods, which are destructive and generate toxic chemical waste. Therefore, in this study, we are proposing a nondestructive, noninvasive, wasteless method for quality control of mustard sauces, in sealed packets, using time-domain nuclear magnetic resonance (TD-NMR) spectroscopy. The method measures the content of soluble solid content (SSC) and moisture content (MC). The analysis is also performed without weighting, which is a time-consuming step. The samples were analyzed in a TD-NMR spectrometer using a wide-bore (10 cm in diameter) Halbach permanent magnet. The TD-NMR signals were acquired with Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence, and the full decay data were processed using chemometric tools. The chemometric models show good correlation and low errors when compared to the SSC and MC values obtained with standard methods. These are good indicator that the proposed method has the potential to be used in quality control of both raw and final products. Furthermore, these parameters can be predicted, without violating the seal of packages.