Reluctance Force Research Articles

Highly Efficient Drive System for Elastocaloric Heat Pumps and Cooling Systems

The need for alternative cooling technologies aside from compressor based cooling is growing since more and more refrigerants get regulated. One promising technology is cooling with the elastocaloric effect by using a phase change of elastocaloric materials that induces a temperature change within the material. The crucial point in the commercialization of this technology is the efficiency of the elastocaloric system including elastocaloric material and the drivetrain. Literature often gives values for the efficiency without including the actuator that drives the system although this is necessary to determine the overall total efficiency. In this study, we introduce a highly efficient drive system based on energy recuperation and deduce the efficiency of this concept. The actuator drive consists of an oscillating armature and is driven by reluctance forces. For the characterization of the system, the elastocaloric material is exchanged with preloaded springs. This gives rise to the possibility of measuring the efficiency of the actuator system itself without considering the elastocaloric material. The efficiency of the drive system is determined to be ηA=95.7%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\eta }_{\ ext{A}}=95.7 \\%$$\\end{document}.

Unified Vector Torque Control for Reluctance Motor With Different Coil Pitch

This paper unifies the vector torque control of reluctance motor with different coil pitch in the classic vector model frameworks, including the typical switched reluctance motor (SRM), mutually coupled switched reluctance motor (MCSRM), synchronous reluctance motor (SynRM) and so on. Based on the proposed vector model, the instantaneous electromagnetic torque of the reluctance motor is decoupled into two components. The first partial torque is called as the Synchronous-Speed Reluctance Force (SSRF), generated by the interaction of the <i>d</i>-axis and <i>q</i>-axis currents. The second partial torque is the Double-Speed Reluctance Force (DSRF), generated by the interaction between the <i>dq</i>-plane current and the 0-axis current. The torque formula can reflect the torque generation and fluctuation reasons, and the proportion of the two torque components is related to the ratio of the varying components of the motor&#x0027;s self-inductance and mutual inductance. Different types of reluctance motors can be summarized in the unified vector model. The conclusion is that the SynRM only contains the SSRF torque while the typical SRM and MCSRM contain both the SSRF torque and DSRF torque. The proposed unified vector torque control method is verified by simulations and experiments of 12-slot 8-pole reluctance motors with different coil pitch.

Production of Ni0.5Co0.5Fe2O4/activated carbon@chitosan magnetic nanobiocomposite as a novel adsorbent of methylene blue in aqueous solutions

Methylene blue is a cationic dye, not degraded naturally due to its aromatic rings. Accordingly, biological, chemical, and physical water treatment methods have been proposed for its removal. Adsorption is an economical and effective method in this regard. In this study, the nickel–cobalt ferrite/activated carbon@chitosan magnetic nanobiocomposite was synthesized as an adsorbent. The nano-adsorbent was evaluated with FESEM, which estimated the particle size at ~ 16.64 nm. According to EDAX analysis, the purity of particles was 99%. XRD characterization showed the successful coverage of chitosan, correct placement of nickel–cobalt ferrite, and the nono-structure of crystallites. The specific surface area was 316 m2/g using the BET theory and 285 m2/g using the Langmuir theory, and the porosity volume was 0.18 cm3/g. According to the VSM analysis, magnetic reluctance and coercive force were 1.1 emu/g and 499 Oe, respectively. The FTIR analysis showed that the reaction was successful, and methylene blue was present on the adsorbent surface. The methylene blue adsorption test indicated that 388 mg/g of the dye was adsorbed (97% dye removal), and the final concentration reached 6 mg/L after 8 h. The point of zero charge (pHpzc) was 6.8.

Model-based flux control of an electropermanent magnet for adaptive zero power gravity compensation

This paper presents a model-based flux control for a variable reluctance actuator with an electropermanent magnet, used for adaptive zero power gravity compensation in magnetic levitation systems. With the hysteresis of the electropermanent magnet being identified and approximated, tailored current pulses are applied by the model-based flux control to tune the magnetization of the electropermanent magnet. In this way, the resulting stationary reluctance force compensates the gravitational force of the levitated mover mass. Based on the identified hysteresis, a non-linear control law is derived, which is extended by an integrator term to compensate modelling uncertainties. In comparison to the state of the art model-free control, the model-based control increases the force tuning rate by a factor of 14 to 19 N/s and improves the robustness of the experimental system in variable mover positions.

Force Modeling and Analysis of a Tube Flux-Switching Transverse-Flux Permanent Magnet Linear Motor

The permanent magnet linear motor (PMLM) has a variety of outstanding topological structures, such as flux switch structure and transverse flux structure. However, the inherited cogging force of PMLM is difficult to reduce without thrust damage. To solve the above-mentioned problem, this article investigates the thrust force, based on a novel flux-switching transverse-flux PMLM (FSTFPMLM) with a simple structure systematically, and provides the guidance to design the FSTFPMLM to achieve a larger thrust, with smaller cogging force. First, the basic structure and working principle of the FSTFPMLM are introduced. Second, an equivalent permeance model of the FSTFPMLM is proposed to calculate the thrust force, including cogging force, permanent magnet thrust, and winding reluctance force. Then, the leading parameters’ influence on the thrust force is investigated; it is concluded that the method effectively minimizes the cogging force and increases the thrust force. Finally, the prototype is manufactured, experiments are performed, and the experimental results agree well with the finite-element method results. This article verifies the effectiveness and practicability of the motor and the proposed analysis method, pointing out the motor's outstanding advantages in reducing cogging force while maintaining high thrust force.

Magnetic Force Calculation in Reluctance Force Launcher

To study the clamping device in reluctance force launcher, the Maxwell stress tensor method is extended to contact force calculations. It is generally believed that the Maxwell stress tensor method is only suitable for objects surrounded by air or vacuum. However, in this article, the Maxwell stress tensor applicable to ferromagnetic materials is re-derived, and the classical Maxwell stress tensor is successfully reproduced. Its integral region is determined as the outer surface of the interface between the object and the outside world, which means that the Maxwell stress tensor method can be used for contact force calculations. Subsequently, the Maxwell stress tensor method was used for force studies in the clamping device. The needed clamping force of the clamping device is calculated. The reducing effect of ferromagnetic materials on the clamping force and the effect on the acceleration force of the projectile are analyzed. Finally, based on the determined integral region, the reason why the integral result of Maxwell stress tensor method is related to the integral path is successfully explained, which provides another theoretical basis for the contact force calculation method in this article.

Reluctance Force Modeling and Compensation

Reluctance Force Modeling and Compensation

Model based investigation of reluctance force shunt damping—A numerical parameter study

An electromagnetic energy converter for vibration damping is studied. The device consists of a coil linked with a magnetic circuit with permanent magnetization and a variable air gap between the fixed magnet and a moving yoke. The reluctance force in the air gap causes magnet and yoke to attract each other. Passive shunts of the coil lead to a hysteresis between reluctance force and motion of the yoke causing damping. A numerical model is set up which describes the magnetic circuit by lumped elements. The nonlinear dynamic state equation of the magnetic flux is solved for harmonic air gap oscillation using the Harmonic Balance Method. Equivalent linear stiffness and damping of the flux-depending reluctance force are computed in order to study the mechanical behaviour of the system. Besides consideration of resistively shunted reluctance force dampers, deployment of a resonant shunt is proposed in order to amplify the damping effect. The influence of shunt parameters on the frequency-depending mechanical behaviour is investigated. Based on the frequency-depending equivalent damping, a suitable application for shunted reluctance force dampers is examined.

Modeling and Characteristic Investigation of Axial Reluctance Force for Bearingless Switched Reluctance Motor

Combining the advantages of switched reluctance motors and magnetic bearings, bearingless switched reluctance motors (BSRMs) have the potential value for industrial applications, such as turbine generators and compressors, because of their high reliability and low friction. In order to ensure the axial levitation of a rotor coping with loading in the axial direction, the axial reluctance force is essential to be considered for the BSRM. In this article, the analytical model of the axial reluctance force is proposed for BSRMs to investigate the axial levitation ability of the studied BSRM. The operational characteristics of the axial reluctance force are revealed by electromagnetic analysis for the BSRM. The factors affecting the axial reluctance force are explained, and the principle of output characteristics with the change of parameters is obtained. The analytical model is applicable for the calculation of the axial reluctance force under different motor parameters, i.e., axial displacement, current, and some mechanical parameters. After that, the finite-element method is adopted to verify the proposed analytical model. Then, the torque and radial levitation control and corresponding power converters are implemented in experiments to test the performance of the studied BSRM on the axial levitation in practice.

Modeling and Analysis of Radial Levitation and Axial Reluctance Force for Four Degree of Freedom Bearingless Switched Reluctance Motor

For traditional 12/8 bearingless switched reluctance motors (BSRMs), the coupling between torque and levitation increases the complexity of control. For the turbomachinery application, 2 degrees of freedom (DOF) BSRMs stabilized by extra 3-DOF active magnetic bearings are required. In this article, an improved BSRM with 4 rotor poles and 12 stator poles is proposed to realize 4-DOF radial levitation, and the torque dead zone is compensated because that two rotors and these poles are assemble with 15 mechanical degree shifted. The decoupling of torque and radial levitation is realized simultaneously. Moreover, the operation principle of axial reluctance force is analyzed for passive levitation in the axial direction. Various experiments were completed to verify the performance of the proposed BSRM, and the prototype achieved stable levitation of the rotor in 10 000 r/min.

Theoretical research on magnetization and demagnetization process of electrohydraulic servo valve with permanent magnet torque motor

The magnetization and demagnetization process of electrohydraulic servo valve with permanent magnet torque motor is the last manufacturing process of electrohydraulic servo valve before its service, which has a significant effect on the output characteristics and magnetic stability of both torque motor and electrohydraulic servo valve. However, the previous studies mainly focus on the static state of the magnetic circuit instead of the changes of the magnetic steel’s states while operating magnetization and demagnetization process of torque motor, which causes many issues such as the unpredictability and inaccuracy of magnetization and demagnetization process. In this paper, a set of theoretical models are proposed to describe this entire magnetization and demagnetization process more accurately aiming at this issue. Firstly, a detailed magnetic circuit mathematical model of permanent magnet torque motor before demagnetization is established according to two kinds of magnetic circuits. Secondly, different from the existing research, in this paper, taking the variety of internal reluctance and magnetomotive force of magnetic steel into consideration, an equivalent method is presented by dividing the B-H curve of the magnetization and demagnetization process into several segments. Finally, the finite element method is used to verify the accuracy of the proposed mathematical model. The research results show the proposed model can accurately calculate the magnetic flux density of magnetic steel at any time and even the air gap’s magnetic flux and the output torque after the magnetization and demagnetization process. This research can help to design the magnetization and demagnetization process such as demagnetizing current to make sure the toque motor meets the requirements, which has an important guiding significance to design and conduct the magnetization and demagnetization process of electrohydraulic servo valve with permanent magnet torque motor.

Design and Analysis of a Self-Holding Three-Position Electric Tubular Actuator

A self-holding three-position electric tubular actuator (SHTPETA) is described in the article. The proposed linear actuator can be applied in a clutch system, where it is necessary to change certain mover positions over time. Other potential applications of such actuators can be shift of gears, coupling (decoupling) of various moving (rotating) mechanisms, or electromagnetic valves. The self-holding force of the proposed SHTPETA is achieved by the reluctance force between the armature and mover cores, where a magnetic flux is excited by a permanent magnet located in the armature and an excitation current is not needed, whereas the moving force is determined by the dc voltage (current) applied to two coils located in the stationary part of the SHTPETA. The article proposes a relatively fast and simple approach for the SHTPETA design process based on the required forces and moved distance.

Analysis of Zero Stiffness Permanent Magnet Bearing Including Reluctance Effect

The isolation bandwidth of zero stiffness permanent magnet bearing (ZSPMB) is limited by the stiffness variation near the zero stiffness point. This paper proposes an accurate and effective modeling technique to analyze and optimize the stiffness of ZSPMB in working range. Since the stiffness of ZSPMB is very sensitive to modeling errors, the variable current model of the permanent magnet is first derived considering magnetic permeability, the influences of which on the magnetic field and force are attributed to the reluctance effect in this paper. Then, the force exerted between permanent magnets (PMs) is equivalently decomposed into Lorentz force and reluctance force. Based on the Biot–Savart law and elliptic integral, the magnetic field of rings with axial, radial magnetizations and the equivalent Lorentz force (ELF) of typical ZSPMB topologies are calculated analytically. The equivalent reluctance force (ERF) is subsequently obtained by combining the finite element method. Compared with the ELF, the ERF is about one order of magnitude smaller and in the opposite direction and it causes the stiffness-displacement curve to drift and deflect. Finally, a Halbach ZSPMB is optimized with the ELF model, and then the ERF is suppressed by fine-tuning the structural size. The finite element analysis results show that the stiffness variation in the working range is effectively reduced, and the validity of the proposed hybrid analytical-finite element model modeling technique is verified.

High-speed Scanner with Nanometer Resolution Using a Hybrid Reluctance Force Actuator

High-speed Scanner with Nanometer Resolution Using a Hybrid Reluctance Force Actuator

Detent Force Reduction in Permanent Magnet Linear Synchronous Motor Base on Magnetic Field Similarity Method

Permanent-magnet linear synchronous motors (PMLSMs) have been widely used in various industries. However, the inherent detent force of these motors limits their application range, especially in high-precision motion and low-speed systems. In this study, magnetic field similarity (MFS) method and edgy teeth-shape optimization are proposed to reduce the detent force. First, an equivalent model of the PMLSM is established wherein the end effect is initially taken into consideration, and the parameters, such as reluctance, energy, and detent force, are calculated. Second, the principle of the MFS is introduced, and the main parameters that affect the detent force are obtained. The detent force is studied and analyzed using parametric analysis, and the shape of the edgy teeth is optimized by particle swarm optimization. The simulation verifies the correctness and applicability of the proposed method. Finally, a prototype is fabricated and the experimental results verify the validity of the mathematical model and simulation results.

Topology Choice and Optimization of a Bearingless Flux-Switching Motor with a Combined Winding Set

The purpose of this paper is to choose a new topology for bearingless flux-switching slice motors, regarding the number of stator and rotor poles, with a combined winding set. Additionally, the selected motor topology is optimized with finite element method (FEM) simulations to improve the performance. Bearingless slice drives feature a magnetically-suspended rotor disk passively stabilized by reluctance forces due to a permanent magnet (PM) bias flux in the air gap and actively controlled by the generation of radial bearing forces and motor torque. Usage of the combined winding set, where each phase generates both motor torque and suspension forces, opens the opportunity for a new topology. The topology choice and optimization are based on FEM simulations of several motor optimization criteria, as the passive axial, tilting and radial stiffness values and the active torque and bearing forces, which are simulated regarding the motor height and specific stator and rotor parameters. Saturation, cogging torque and cogging forces are also analyzed. The 3D FEM program ANSYS Maxwell 2015 was used. The results led to an optimized bearingless flux-switching motor topology with six new stator segments and seven rotor poles. By optimizing the geometry, a considerable improvement of performance was reached. This geometry optimization is a base for a future prototype model.

High-Performance Hybrid-Reluctance-Force-Based Tip/Tilt System: Design, Control, and Evaluation

This paper presents the design, assembly, and evaluation of a novel integrated two degree of freedom (2DoF) actuator design for tip/tilt motion and its integration into a fast steering mirror with comparably large range. The system is designed for scanning applications, such as in optical metrology systems, and comprises an integrated symmetric 2DoF hybrid-reluctance-force actuator and moverflexure-design. The actuator design employs a permanent magnet for biasing the actuator with a constant flux and two actuator coils per axis to generate a steering flux for positioning the mover. The system prototype has an angular range of ±3° in tip and tilt and achieves a closed-loop control bandwidth of 1 kHz based on the signal of eddy current sensors. Compared to the only so far realized state-of-theart reluctance force actuated fast steering mirror system with integrated sensors, the presented design enables to improve the product of range times' bandwidth, representing a measure for the system performance, by more than 85%.

Analysis and experimental research on air gap characteristics of permanent magnet low‐resistance belt conveyor

Normal belt conveyors transfer materials by utilising the friction force between driving rollers and the conveyor, resulting in sag resistance and friction. In order to overcome this shortcoming, this study presents a new permanent magnet low resistance belt conveyor, which is used to replace the original mechanical contact with the permanent magnetic support system. The simplified mechanical three-dimensional model of its permanent magnet support system was established. The mathematical expressions of suspension force, reluctance force and lateral force were deduced with Maxwell equations based on reasonable assumptions. The approximate relationship among air gap length, magnetic flux density and magnetic force was derived from the analysis of air gap characteristics of the permanent magnet support system and the finite-element simulation of the permanent magnet support system under different air gap conditions. A self-designed test device of the permanent magnet low-resistance belt conveyor was used to apply different sets of loads and carry out the experimental research on the permanent magnet support system under different air gap lengths, so as to obtain the pressure distribution of the magnetic conveyor belt. The findings provide theoretical references for further research on the permanent magnet low-resistance belt conveyor.

Rotary-Reciprocating Movement Switched-Reluctance Machines With Consequent Axially Shifted Poles

A new switched-reluctance machine (SRM) topology with combined rotary and reciprocating rectilinear movement is introduced in this paper. The topology of this machine is based on the conventional radial-flux SRM with a modified rotor structure. Unlike the other rotary-translational electromechanical systems which have separate units, one for rotary motion and another for translational reciprocating motion, the proposed machine achieves combined rotary-reciprocating (RR) movement with just one set of stator coils around each pole identical to the conventional SRM. By exciting each pole of the stator, both radial and axial magnetic flux will be produced in the air gap of the machine. As a result, the electromagnetic reluctance torque around the axis of the rotation and the reluctance force along the axis of translational movement are produced. Details of the rotor structure and machine operation are presented. Magnetic equivalent circuit (MEC) analytical equations are derived for four operational points within the RR motion cycle. Finite-element analysis (FEA) is utilized to validate the analytical MEC equations. The output performance profiles are simulated for two example machines using static 3-D FEA to investigate the impact of the axial displacement of the consequent poles. In addition, a sensitivity analysis is carried out to investigate the impact of the rotor pole angle on the torque and force production of the machine. The dynamic behavior of the proposed structure is analyzed and discussed for two displacements of the consequent axially shifted poles.

Hysteresis Bearingless Slice Motors with Homopolar Flux-biasing.

We present a new concept of bearingless slice motor that levitates and rotates a ring-shaped solid rotor. The rotor is made of a semi-hard magnetic material exhibiting magnetic hysteresis, such as D2 steel. The rotor is radially biased with a homopolar permanent-magnetic flux, on which the stator can superimpose 2-pole flux to generate suspension forces. By regulating the suspension forces based on position feedback, the two radial rotor degrees of freedom are actively stabilized. The two tilting degrees of freedom and the axial translation are passively stable due to the reluctance forces from the bias flux. In addition, the stator can generate a torque by superimposing 6- pole rotating flux, which drags the rotor via hysteresis coupling. This 6-pole flux does not generate radial forces in conjunction with the homopolar flux or 2-pole flux, and therefore the suspension force generation is in principle decoupled from the driving torque generation. We have developed a prototype system as a proof of concept. The stator has twelve teeth, each of which has a single phase winding that is individually driven by a linear transconductance power amplifier. The system has four reflective-type optical sensors to differentially measure the two radial degrees of freedom of the rotor. The suspension control loop is implemented such that the phase margin is 25 degrees at the cross-over frequency of 110 Hz. The prototype system can levitate the rotor and drive it up to about 1730 rpm. The maximum driving torque is about 2.7 mNm.