Halbach Permanent Magnet Array Research Articles

Improved design of Lorentz force-type magnetic bearings for magnetically suspended gimballing flywheels

A Lorentz force-type magnetic bearing (LFMB) with good linearity is suitable for the high-precision deflection control of a magnetically suspended gimballing flywheel (MSGFW). In this paper, a novel LFMB with improved double magnetic circuits is presented. Inclined magnetization Halbach array permanent magnets (PMs) and trapezoidal PMs are utilized for improving the magnetic flux density. A mathematical model of the magnetic flux density is established based on the equivalent surface current method. To obtain the maximum magnetic flux density, the optimal magnetization angle is calculated, and the dimension parameters are optimized by the sequential quadratic programming method. A maximum magnetic flux density of 0.615 T is obtained, which is 7.9% larger than that of an LFMB with conventional double magnetic circuits. Based on simulation results, LFMB prototype magnetic flux density experiments are carried out. The results show that the magnetic flux density fluctuations of the two LFMB schemes are similar. The maximum magnetic flux density of 0.608 T is increased by 6.7% when compared with that of the LFMB with conventional double magnetic circuits at 0.57 T. The error between the simulation and the experiment is within 5%. This indicates that the LFMB with improved double magnetic circuits is promising when it comes to meet the agile maneuver requirements of the spacecraft.

Comparative Study of Dual PM Vernier Machines

In this paper, two types of dual permanent magnet (PM) machines, i.e., stator slot dual-PM (SSDPM) machine and split-tooth dual-PM (STDPM) machine, are investigated and compared. Both machines have consequent pole structure with Halbach array PMs. Their difference lies in the position of stator PM. The SSDPM machine has Halbach array PMs in the stator slots, while the STDPM machine has PMs between the split teeth. Torque characteristics, i.e., average torques and torque ripples, of different slot/pole number combinations of the two machines are compared. The 24 stator slots/20 rotor slots/4 armature pole pair (24S20R4Pa) SSDPM machine with distributed windings and the 24 stator slots/10 rotor slots/4 armature pole pair (12S20R4Pa) STDPM machine with concentrated windings are compared under both open-circuit and on-load conditions. The results show that the SSDPM machine is more competitive by delivering higher torque density and higher power density.

Optimization on Size of Halbach Array Permanent Magnets for Magnetic Levitation System for Permanent Magnet Maglev Train

A permanent magnet suspension (PMS) magnetic levitation (Maglev) system consisted of magnetic rail magnets and carriage magnets are investigated for PMS Maglev vehicle. The characteristics of magnetic flux line and magnetic flux density distribution in the suspension gap region are analyzed by using finite element method. The results show that the Halbach Array stack structure generates strong sinusoidal periodic magnetic field in the suspension gap region. The size of Halbach Array permanent magnets stacked structure model was simulated and optimized, and the optimal size factor was obtained. In addition, a levitation force model describing the relationship between magnetic levitation force, permanent magnet size and levitation height was established by molecular current method. The correctness of the levitation force model is evaluated. Finite element simulation and experiment verify the validity of the levitation force model. The results show that the optimized Halbach Array permanent magnets can generate large suspension force and good stability, which is of great significance to improve the utilization rate of permanent magnet materials and save costs, and is conducive to the further development of permanent magnet maglev train. The study is useful for analysis and design optimization of maglev train.

Analysis of Superconducting Synchronous Motors With Halbach Array Field Excitation

This article evaluates the novel design approach of a 3 MW partially superconducting synchronous machine for electric aircraft propulsion. Its special feature is the application of an electromagnetic Halbach array for the field excitation to reduce the back yoke weight and thereby increase the overall output power density. The electromagnetic Halbach array is obtained by reproducing a permanent magnet Halbach array with high-temperature superconducting coils. The arrangement is further optimized, and its field characteristics are compared to a conventional superconducting field winding design. Even though the Halbach array has a higher space and superconductor consumption, it shows better characteristics concerning the intensity of inside and outside magnetic field. Applied in a superconducting motor, the Halbach array field winding achieves a back yoke thickness reduction of up to 85% and a back yoke weight reduction of up to 78% compared to reference models. The gravimetric power density is increased by up to 30% at the expense of volumetric power density. In exchange for a back yoke weight reduction, other components, such as field winding and cryostat, become heavier.

Analysis of Halbach Permanent Magnet Array with Convex Type Section

This paper proposes Halbach permanent magnet arrays with convex type section. The magnetic field is modeled according to Ampere’s hypothesis of molecular current. Based on the model, the fundamental component of the magnetic flux density and the sinusoidal distortion rate are selected as evaluation indexes. Compared with these of Halbach permanent magnet array with normal square section, the Halbach permanent magnet arrays with specific configuration own better performance, which provide direction for further optimization.

Structural optimisation based on a snake‐like wave energy convertor with magnetoelectric transducer

Snake-like wave energy conversion (WEC) is a new type of WEC that combines raft WEC and magnetoelectric transducer. This type of WEC uses the magnetoelectric transducer, which is designed based on the permanent magnet linear generator and Halbach permanent magnet array, as its power take-off unit. The purpose of this study is to design a matching magnetoelectric transducer for WEC in common wave conditions and test its performance. The hydrodynamic model of the snake-like WEC is established to study the motion of WEC in regular waves. The equivalent magnetic circuit model of the magnetoelectric transducer is set up to optimise its ability to harvest wave energy in the ocean. Taking the maximum damping coefficient (cm ·max) as the optimisation goal of the magnetoelectric transducer, the induced voltage and output power of the magnetoelectric transducer in relatively uniform and sinusoidal motion can be calculated by simulation software. Finally, a prototype of the magnetoelectric transducer was made and its performance was tested. The experiment shows that the magnetoelectric transducer has a good ability to harvest wave energy, and snake-like WEC has wide applicability.

Optimized design and performance analysis of a magnetic-field modulated brushless dual-mechanical port motor with Halbach array permanent magnets

In order to develop an electrical continuously variable transmission (E-CVT) to replace mechanical power coupling equipment applied in series-parallel hybrid electric vehicle (HEV), this paper proposes a magnetic-field modulated brushless dual-mechanical port motor with Halbach array permanent magnets, which has a more compact structure. The operating characteristics are analyzed by the lever analogy. It is concluded that the motor can realize the speed and torque decoupling between the engine and the wheel, which meet multi-mode operation requirements for HEV. To realize the multi-objective design of torque output, torque ripple and usage amount of permanent magnets, an optimization scheme combined parameter sensitivity with response surface methodology is adopted. The trade-offs among the optimization objectives are considered, then the key structural parameters and its optimal values are efficiently determined. Based on a two-dimensional model, the electromagnetic performances are simulated and analyzed. The results show that, after the parameters optimization, the no-load back electromotive force (EMF) has better sinusoidal characteristic, and the torque ripples and cogging torque peaks of the motor have been significantly reduced. Furthermore, a prototype motor is tested. The experimental results are consistent with the simulation results, which demonstrates the validity of the proposed structure and parameter optimization method.

Design of a 3-RPR Flexure System for Optical Switch Assembly

In the MEMS optical switch assembly, the collision is likely to happen between the optical fiber and the U-groove of the chip due to the uncontrollable assembly errors. However, these errors can hardly be completely eliminated by the active control using high precision sensors and actuators. It will cause the large acting force and part damage, which further leads to the assembly failure. To solve this question, this paper presents a novel low-cost three-degree-of-freedom (three-DOF) passive flexure system to adaptively eliminate the planar assembly errors. The flexure system adopts three parallel kinematic chains with a novel 3-RPR structure and has a compact size with a diameter of 125 mm and thickness of 12 mm. A novel eddy current damper with the structure of Halbach array permanent magnets (PMs) is utilized to suppress the adverse mechanical vibration of the assembly system from the background disturbances. Analytical models are established to analyze the kinematic, static, and dynamic performances of the system in detail. Finally, finite element analysis is adopted to verify the established models for optimum design. The flexure system can generate a large deformation of 1.02 mm along the two translational directions and 0.02° along the rotational direction below the yield state of the material, and it has much higher natural frequencies than 200 Hz. Moreover, the large damping force means that the designed ECD can suppress the system vibration quickly. The above results indicate the excellent characteristics of the assembly system that will be applied into the optical switch assembly.

A Novel Dual-Stator Hybrid Excited Permanent Magnet Vernier Machine With Halbach-Array PMs

Permanent magnet Vernier machine (PMVM) has received more and more attention, due to its high torque density at low rotation speed. This article proposes a dual-stator hybrid excited PMVM with Halbach-array permanent magnets (PMs). The proposed machine can achieve high torque density with consequent-pole Halbach-array PMs in the rotor and has good flux regulation capability and high power factor. First, the basic principle of the proposed machine is discussed, and the proposed machine can be regarded as a combination of two machines. Finite-element analysis simulations are performed to verify the performance. Moreover, the influence of different parameters on the torque density, flux regulation capability, and power factor is analyzed. The results demonstrate the effectiveness of the proposed machine.

3D Analytical Model of Permanent Magnet and Electromagnetic Hybrid Halbach Array Electrodynamic Suspension System

In this paper, a 3D analytical model of permanent magnet (PM) and electromagnetic hybrid Halbach array electrodynamic suspension (EDS) system for a conductive plate is presented. When the hybrid Halbach array moves to cut the conductive plate, the 3D eddy current forces are derived using the second-order vector potential (SOVP) based on y-component of the source magnetic flux density, which is derived using the Biot–Savart law and surface current method. The accuracy of the derived equations is verified by a 3D finite-element analysis (FEA) model. Furthermore, the effects of the main characteristic parameters on the levitation force are analysed.

Damping vibration analysis of a dual-axis precision force sensor based on passive eddy current

High precision force sensors usually include flexible structures, which are prone to cause unnecessary mechanical vibrations, due to their low stiffness and high sensitivity. Aimed at the adverse problem, this paper proposes a novel two-degree-of-freedom passive damping system dedicated to the vibration suppression of a dual-axis precision force sensor. The damping system consists of two identical eddy current dampers (ECDs), each of which utilizes a double-layer Halbach-array permanent magnet structure and a middle-layer copper plate to generate a large damping force. Analytical models are established to predict the damping characteristic and dynamic behavior of the sensor system, with further verification through finite element simulation. Experiments are implemented to demonstrate the effectiveness of the damping design to suppress the sensor vibration in comparison with three different configurations (without ECD, with a single ECD, and dual ECDs). The results indicate the excellent damping characteristics of the developed ECD. This feature can be also extended to the vibration suppression of the planar XY positioning stages.

Gradient Coil Design and Realization for a Halbach-Based MRI System

In this paper we design and construct gradient coils for a Halbach permanent magnet array magnetic resonance (MR) scanner. The target field method, which is widely applied for the case of axial static magnetic fields, has been developed for a transverse static magnetic field as produced by a Halbach permanent magnet array. Using this method, current densities for three gradient directions are obtained and subsequently verified using a commercial magneto-static solver. Stream functions are used to turn the surface current densities into wire patterns for constructing the gradient coils. The measured fields are in good agreement with simulations and their prescribed target fields. Three dimensional images have been acquired using the constructed gradient coils with very low degree of geometric distortion.

Optimization design of halbach permanent magnet motor based on multi-objective sensitivity

The halbach permanent magnet synchronous motor (HPMSM) combines the advantages of permanent magnet motors and halbach arrays, which make it very suitable to act as a robot joint motor, and it can also be used in other fields, such as electric vehicles, wind power generation, etc. At first, the sizing equation is derived and the initial design dimensions are calculated for the HPMSM with the rated power of 275W, based on which the finite element parametric model of the motor is built up and the key structural parameters that affect the total harmonic distortion of air-gap flux density and output torque are determined by analyzing multi-objective sensitivity. Then the structure parameters are optimized by using the cuckoo search algorithm. Last, in view of the problem of local overheating of the motor, an improved stator slot structure is proposed and researched. Under the condition of the same outer dimensions, the electromagnetic performance of the HPMSM before and after the improvement are analyzed and compared by the finite element method. It is found that the improved HPMSM can obtain better performances.

Torque Calculation of Permanent-Magnet Spherical Motor Based on Permanent-Magnet Surface Current and Lorentz Force

Due to the complex spatial magnetic field distribution and the variable motion mode, the torque analysis of spherical motors is usually carried out by the finite-element method (FEM) with a large amount of calculation and time consumption. In order to improve analysis efficiency, this article proposes a spherical motor torque calculation method based on the permanent-magnet surface current model and Lorentz force, aiming to replace the finite-element calculation. First, the equivalent surface current analytical expression of the rectangular permanent-magnet magnetic field is derived. Then, this expression is used to establish the 3-D magnetic field analytical model of Halbach array permanent magnets in the rotor. Based on this magnetic field, the Lorentz force of the energized stator coil is calculated. Then, the electromagnetic torque generated by the rotor is analyzed. Finally, the analytical results of the magnetic field and the motor torque are compared with those by the FEM and experiments, verified that, under the premise of ensuring the calculation accuracy, the proposed method effectively shortens the calculation time and has higher stability.

Comparative Analysis of Coreless Axial Flux Permanent Magnet Synchronous Generator for Wind Power Generation

A 90° Halbach permanent magnet array coreless axial flux permanent magnet synchronous generator for wind power generation is compared with a conventional axial flux permanent magnet generator with cut cake type permanent magnet. 2D analytic model of generator is established. The air gap magnetic fields of two generators are analyzed by analytical method, and the air gap magnetic density and harmonic content are analyzed. Then the influence of different parameters on voltage total harmonic distortion is analyzed by changing the pole arc coefficient, air gap length, permanent magnet thickness and number of turns. Two prototypes of generators are manufactured, and the correctness of the simulation results is verified by experiments.

Improvement of torque performances in consequent-pole PM machines with optimized six-layer winding and Halbach PMs array

This paper presents a torque performance improvement method for three-phase consequent-pole permanent magnet (PM) (CPM) machines. The key of this method is to consider torque ripple and output torque simultaneously in CPM machines. This method is rea

Design and Manufacture of a Linear Actuator Based on Magnetic Screw Transmission

This article proposes a practical design guide for a linear electromagnetic actuator based on the concept of magnetic screw transmission, in which manufacturing and assembly technologies are investigated. The surface-inserted design is first used to form a required helical-shape magnetic pole, which exhibits simple processing, high precision, and robust structure. Moreover, different topologies are developed using the 3-D finite-element analysis aided design, with the goal of optimizing thrust force. In addition, different number of permanent-magnet (PM) segments are first proposed to reduce the cogging effect. Afterward, the linear actuator integrates the rotary machine and the magnetic screw together to construct a compact design and decouples the magnetic circuits. The decoupling design focuses on the self-shielding effect of the Halbach PM array, and the special bearing supports are selected to avoid the eccentricity. Finally, a prototype is built using the developed techniques. Experiments are carried out on a linear test bench, verifying the theoretical analysis.

Design of a wave energy converter based on Halbach magnetic array

With the continuous development of society and economy, people’s demand for electric energy is increasing. The low-carbon and energy-saving technologies of renewable energy especially wave energy have become the focus of current researches. Considering the increasingly serious energy problems, a wave energy converter (WEC) is proposed based on Halbach permanent magnetic array, which increases the output performance. The equivalent magnetic circuit model of the WEC is established. The static magnetic field modeling and structural parameters optimal permanent of the WEC are performed on this theoretical. Theoretical studies have found that the optimal permanent magnet thickness ratios for Halbach permanent magnet array structures is 0.6, and the ratio of permanent magnet to coil radial ratio is 0.7. The coil winding form and rectifying circuit of the WEC were designed. The WEC equivalent magnetic circuit model was verified by COMSOL Multiphysics finite element software, and the open circuit voltages of WEC was obtained. If the WEC moves at a speed of 0.1 m/s, the coil voltage can reach about 113 V after simulation. According to the testing requirements of the WEC, a test platform was built. The Halbach permanent magnet array structures greatly enhances the wave energy collection of WEC.

Magnetic field analysis of Primary Permanent Magnet Linear Motor Based on Halbach Distribution

The rail transit system driven by linear motor has outstanding advantages in climbing ability, traction performance, vibration and noise. However, with the increase of traffic travel and other situations, how to ensure that the linear motor still has a large thrust and stability in the air gap condition is the key technical problem. In order to solve this problem, three Halbach permanent magnet array structures are proposed and applied to the magnetic barrier coupled primary permanent magnet unilateral excitation linear motor (MBCPPMUELM). The finite element software is used for simulation and analysis. By comparing the harmonic distribution of air gap magnetic field of the three Halbach permanent magnet array motors, a topology structure with high magnetic field modulation effect is obtained It provides a useful reference for the further design and analysis of this kind of motor.

A novel fully floating three-body system for direct-drive wave energy converter

Converting persistent and renewable wave energy into electricity has been studied in recent years. This research develops a novel fully floating three-body direct-drive wave energy converter (DD-WEC) prepared for the research of the multi-body DD-WEC. Its prototype consists of three floating bodies, but both three bodies act as buoys to extract the wave energy, not just a body. And the relative motion of the buoys induces the voltage in Halbach array permanent magnet linear generators coils. Its feasibility is investigated theoretically by analyzing the dynamics of motion of the floating buoys. As a result, parametric design of the WEC is achieved. The load performance of the DD-WEC is investigated by using the Simulink, and it can be found that the relative displacements between buoys are different. Then, the electromagnetic power of the proposed WEC is much higher compared to a two-body DD-WEC by using numerical simulation Finally, the DD-WEC prototype is manufactured and tested in the wave tank. The results show that the WEC can produce the most electricity for the case with the wave period of 1.6 s, and the maximum voltage reaches 14.2 V, which is consistent with the simulation results. The results show that the proposed DD-WEC is well suited for wave energy conversion.