Axial Hybrid Magnetic Bearing Research Articles

Design and Analysis of an Axial Hybrid Magnetic Bearing With the Slice Stator for the Magnetically Suspended Centrifugal Compressor

Design and Analysis of an Axial Hybrid Magnetic Bearing With the Slice Stator for the Magnetically Suspended Centrifugal Compressor

Electromagnetic Characteristics and Capacity Analysis of a Radial–Axial Hybrid Magnetic Bearing with Two Different Radial Stators

Compared with the widely used four-pole magnetic bearings, three-pole magnetic bearings are driven by a three-phase power inverter and have advantages pertaining to their small volume, low costs, and low power losses. However, the asymmetric structure of the three-pole bearings presents disadvantages in terms of their strong nonlinearity and couplings among the suspension forces of the control currents and displacements. The radial–axial hybrid magnetic bearing (RAHMB) with six-pole bearings is proposed to solve this problem. Firstly, the structure and working principle of the RAHMB are introduced. Secondly, the mathematical models of the RAHMB are established, and in order to obtain the radial capacity, the maximum suspension forces of the three-pole and six-pole RAHMBs are theoretically analyzed. Thirdly, the nonlinearity and couplings of the suspension forces with the control currents and displacements are analyzed. The radial capacity of the three-pole and six-pole RAHMB is 74.6 N and 83.6 N, respectively, which is an increase of 12.0%. Finally, the experiment results prove that the nonlinearity and couplings of the six-pole RAHMB are smaller than the nonlinearity and couplings of the three-pole RAHMB, and the maximum radial capacity of the three-pole and six-pole RAHMB is 84.1 N and 94.8 N, respectively, which is an increase of 12.7%. The simulation results are basically consistent with the experimental results, indicating the correctness of the theoretical analysis.

Design and Optimization Method with Independent Radial and Axial Capacity for 3-DOF Magnetic Bearings in Flywheel

The six-pole radial–axial hybrid magnetic bearing (RAHMB) has the advantages of small space and low power consumption, making it suitable for flywheel batteries. The bearing capacity and the volume are the main specifications of magnetic bearings that should be considered comprehensively. In this work, the six-pole RAHMB was used in a horizontal flywheel battery. As the axial bearing capacity is relatively smaller than the radial bearing capacity, a design method with independent radial and axial bearing capacity is proposed, and the parameters are optimized to minimize the volume. The mathematical model of six-pole RAHMB was derived from the equivalent magnetic circuit method. The relationships between bearing capacity, biased flux density, saturation flux density and the section area of magnetic poles were analyzed. The basic principle of the design method with independent radial and axial bearing capacity is to determine which five of the variables are preferred. According to the design method, one radial or axial biased flux density should be optimized to minimize the volume, and the genetic algorithm (GA) was adopted to search for the optimal value. The structural parameters were designed based on the optimized value of biased flux density. The total volume of the six-pole RAHMB was reduced by 24%. A 3D finite element (FE) model was built. The analysis results and experimental results show that the proposed design and the optimization method are feasible and valid.

Modeling and Control Strategies of a Novel Axial Hybrid Magnetic Bearing for Flywheel Energy Storage System

This article presents modeling and control strategies of a novel axial hybrid magnetic bearing (AHMB) for household flywheel energy storage system (FESS). The AHMB combines a passive permanent magnet (PM) magnetic bearing (MB) and an axial active MB in one unit, thus can offer benefits such as compactness of the structure, high load capacity, and low power consumption. A coupled magnetic field-circuit method is proposed for modeling this bearing. Compared with the regular equivalent magnetic-circuit (EMC) method, it introduces special concerns of the complex air-gap field, calculated from the conformal transformation of the air-gap geometry, to take into account the effect of flux fringing and leakage. A low-cost Hall sensor is used to replace the expensive Eddy-current position sensor to measure the changes in air gap flux density caused by the rotor axial displacement. Therefore, a novel flux density feedback control is adopted instead of the traditional position feedback control to directly stabilize the magnetically suspended flywheel. A prototype of this bearing is designed and fabricated, which is tested in a small-scale FESS. The simulation results and the experimental results demonstrate that the proposed model provides better accuracy than the traditional EMC and the flux-density feedback control strategy based on a low-cost Hall sensor can achieve a consistent performance with the traditional position feedback control strategy.

Structural optimization and dynamic characteristics of the new type 3-degrees of freedom axial and radial hybrid magnetic bearing

A new type of three degrees of freedom axial-radial hybrid magnetic bearing (3-DOF ARHMB) with compact structure, shorter axial length and smaller volume is proposed for the flywheel energy storage system. The axial direction adopts the permanent magnet biased thrust bearing (PMB) made of soft magnetic composite materials (SMCs). In the radial direction, the laminated structure is used to reduce the eddy current, and the Halbach array is introduced to strengthen the magnetic density of the radial air gap. Firstly, the dynamic magnetic flux distribution of the 3-DOF ARHMB is analyzed by the finite element method (FEM). Based on the equivalent magnetic circuit method, the equivalent reluctance model with comprehensive consideration of eddy current effect and magnetic leakage effect is established, and then the frequency responses are analyzed. Secondly, a constraint model coupled with structural parameters, equivalent reluctance and magnetic leakage coefficient is established, and an adaptive particle swarm optimization algorithm (APSO) is used to optimize the bearing parameters. Finally, based on the equivalent reluctance model, the axial and radial force-current factor and force-displacement factor are derived, and the dynamic characteristics of bearings with different structures and materials are compared and analyzed. The results show that the new 3-DOF ARHMB made of SMCs can provide much larger and more stable magnetic force and larger bandwidth than that made of carbon steel materials, and has better dynamic characteristics under higher-frequency conditions, which can meet the industrial requirements of flywheel energy storage system.

Design and Modeling of an Integrated Flywheel Magnetic Suspension for Kinetic Energy Storage Systems

The paper presents a novel configuration of an axial hybrid magnetic bearing (AHMB) for the suspension of steel flywheels applied in power-intensive energy storage systems. The combination of a permanent magnet (PM) with excited coil enables one to reduce the power consumption, to limit the system volume, and to apply an effective control in the presence of several types of disturbances. The electromagnetic design of the AHMB parts is carried out by parametric finite element analyses with the purpose to optimize the force performances as well as the winding inductance affecting the electrical supply rating and control capability. Such investigation considers both the temperature dependence of the PM properties and the magnetic saturation effects. The electrical parameters and the force characteristics are then implemented in a control scheme, reproducing the electromechanical behavior of the AHMB-flywheel system. The parameter tuning of the controllers is executed by a Matlab/Simulink code, examining the instantaneous profiles of both the air-gap length and the winding ampere-turns. The results of different dynamic tests are presented, evidencing the smooth air-gap changes and the optimized coil utilization, which are desirable features for a safe and efficient flywheel energy storage.

The effect of permanent magnet position on axial and radial load capability in axial hybrid magnetic bearing

The axial and radial load capacity of axial hybrid magnetic bearing (HMB) is critical for the magnetic levitation system. In this paper, the effect of permanent magnet (PM) position on axial and radial magnetic force and stiffness in axial HMB is investigated. Six different configurations are considered and the equivalent magnetic circuits of HMBs for each configuration is built and studied based on the distribution of magnetic field and magnetic leakage. The dependence of axial and radial magnetic force and stiffness on the axial displacement, radial displacement and control current is calculated and investigated for different configurations. To validate the calculated results, the axial and radial magnetic forces for each configuration are simulated by finite element method. A good agreement between the calculated and simulated results validated the proposed magnetic circuit models.

Magnetic flux leakage modelling and optimisation of a CRAHMB for DC motor

In this study, a combined radial–axial hybrid magnetic bearing (CRAHMB) with four poles is designed for high-speed brushless DC motor. Owing to the small distance of radial and axial unit of CRAHMB, the magnetic flux leakage (MFL) in both radial and axial directions is complex and serious. This study focuses on effective analytical model and optimisation of CRAHMB including flux leakage of permanent magnet circuit and control electromagnetic circuit. MFL analytical model was built based on equivalent magnetic circuit method. Under the condition of satisfying the maximum bearing capacity, the MFL coefficients were optimised with sequence quadratic programming method. A set of optimum parameters were suggested. MFL before and after optimisation are compared by finite element method. Finally, current stiffness calculated with optimised analytical model was verified on a DC motor experiment. The result shows the accuracies of both the axial and radial current stiffness are enhanced.

Designing and Experimental Verification of the Axial Hybrid Magnetic Bearing to Stabilization of a Magnetically Suspended Inertially Stabilized Platform

To decrease the mass and power loss of axial hybrid magnetic bearings (HMBs) in the application of inertially stabilized platform (ISP) with a large axial diameter, this paper investigates the effects of the layout of axial HMBs and the degree of asymmetry (DOA). An asymmetry axial HMB is proposed for ISP based on DOA. Each single axial HMB is modeled and analyzed using the reluctance network method. And the relationship between current and force, as well as the displacement and force, are studied. Additionally, the optimization design method of the axial HMB is presented based on DOA. According to the principle of the design, the layout of the complete asymmetry axial HMB is designed with eight single axial HMBs in the upper end and four single axial HMBs in the lower end of ISP. Furthermore, the relationship among displacement, current, and displacement stiffness and the relationship among displacement, current, and current stiffness are analyzed as the DOA varies. A prototype is manufactured based on the above design and analysis, and experiments are carried out. Experimental results illustrate that the mass and power loss will be decreased dramatically compared with the symmetry layout of axial HMBs.

Parameter Design and Static Performance Analysis of a Novel Axial Magnetic Bearing for Maglev Wind Generators

As an important component of maglev wind generators, magnetic bearing should possess the merits of small volume, light weight, lower consumption and so on. A novel low-loss axial hybrid magnetic bearing (HMB) is proposed in this paper, its structure and operation principle are introduced, and the process of producing suspension force is elaborated. Based on equivalent magnetic circuit method, magnetic circuit models of PM and control coil are analyzed and established to deduce the quotation of axial levitation force. The accuracy and the reasonableness of proposed low-loss axial HMB are analyzed and validated by using finite element method (FEM), and the comparison between theoretical calculation and FEM is given, which indicates the proposed HMB exhibits good dynamic response and easy control.

Design and Static Performance Analysis of a Novel Axial Hybrid Magnetic Bearing

This paper proposes an axial permanent magnet-biased hybrid magnetic bearing, which possesses the advantages of low power consumption, simple structure, and easy control. The structure and operation principle are introduced. Then, the mathematical models, including the suspension force expression, are built based on traditional equivalent magnetic circuit. In addition, the basic principle of structure parameter design is presented, based on which the key parameters are given. Due to the inaccuracy of the traditional equivalent magnetic circuit, an improved method for magnetic circuit is introduced. Last, the accuracy of the analytical method is validated by finite element analysis and it also has an important reference value for other types of magnetic bearings design.

Parameter Design and Analysis on Axial Hybrid Magnetic Bearing Using in Magnetic Suspension Flywheel

Magnetic suspension flywheel system is the actuator of spacecraft in high accurate position control, which requires the employed magnetic bearing possessing advantages of compact structure, small volume, light weight, low power loss, high efficiency and so on. A novel axial hybrid magnetic bearing in magnetic suspension flywheel is proposed, and the bias magnetic flux is provided with a permanent magnet ring. The cost and total volume of this structure can be reduced, which is especially suitable for magnetic suspension flywheel system. The structure and working principle of the axial magnetic bearing are explained, the mathematical expressions of the maximum bearing capacity are obtained, the detailed process of parameter design is presented, and the flux and maximum bearing capacity of the hybrid magnetic bearing are analyzed by using finite element analysis software. The analysis results validate the correctness of parameter design on the axial hybrid magnetic bearing.

Mathematical Model and Control of Axial Hybrid Magnetic Bearings Based on <i>α</i>-th Order Inverse System Theory

A linearization control research based on α-th order inverse system method has been developed for an axial hybrid magnetic bearing, which is a nonlinear system. The configuration of the axial hybrid magnetic bearing is briefly introduced, the working principle of the hybrid magnetic bearing is analyzed, and then the suction equations are set up. Based on expounding of α-th order inverse system method, and aiming at dynamics model of the axial hybrid magnetic bearing, the feasibility of linearization control is discussed in detail, the linearization control arithmetic based on α-th order inverse system method is deduced, and then close system controller is designed. Finally, the simulation system is set up with MATLAB software. The step response of system, the start up displacement curve of rotor and the performance of anti-disturbance of system are simulated. The simulation results have shown that the α-th order inverse system control strategy can realize accurate linearization for nonlinear mathematical model of the axial hybrid magnetic bearing, and the designed close control system has good dynamic and static performance.

Low eddy loss axial hybrid magnetic bearing with gimballing control ability for momentum flywheel

For a magnetically suspended momentum flywheel (MSMF), the spinning rotor can be tilted by a pair of the presented axial hybrid magnetic bearing (AHMB) with eight poles and rotates around the radial axes to generate a large torque to maneuver the spacecraft. To improve the control performance and gimballing control ability of the AHMB, characteristics such as magnetic suspension force, angular stiffness and tilting momentum are researched. These segmented stator poles cause the magnetic density in the thrust rotor plate to be uneven unavoidably and the rotational loss is large at high speed, but we optimized the stator poles configuration and caused the thrust rotor plate formed by bulk DT4C and laminated material to make the magnetic density in the thrust rotor plate change less and be smoother. Laminated material such as 1J50 film with a thickness of 0.1mm can make the variation of the magnetic density in DT4C become very small and the eddy loss of it be negligible, but the stress produced in the “O” shape stacks by reeling has a bad effect on its power loss. Nanocrystalline can reduce eddy losses and is not affected by the reeling process. Based on the AHBM consisting of the stator with eight improved poles and the presented thrust rotor plate with DT4 and nanocrystalline, the rotational loss of 5-DOF magnetically suspended momentum flywheel with angular momentum of 15Nms at 5000rpm has reduced from 23.4W to 3.2W, which proved that this AHMB has low eddy loss for the gimballing control ability.

A Novel 3-DOF Axial Hybrid Magnetic Bearing

In this paper, we propose a novel structure of permanent-magnet-biased axial hybrid magnetic bearing. It has four segments of poles to control three degrees of freedom (3-DOF). Based on the inner and outer air gaps in conventional axial magnetic bearings, a novel air gap, called the subsidiary air gap, is constructed between the permanent magnet and the stator poles. This air gap separates the bias flux paths from the control flux paths. As a result, lower power loss of the axial magnetic bearing can be achieved due to lower magnetic reluctance of the control flux paths. Furthermore, by means of the equivalent magnetic circuit method and the 3-D finite-element method (FEM), we analyze and model the 3-DOF axial hybrid magnetic bearing. Experimental results show that the presented axial magnetic bearing has good control performance and little coupling among X, Y, and Z directions. However, the rotational power loss will be large at high speed because of the alternating flux density in the thrust plate produced by four segments of stator poles. Therefore, we propose a novel stator, named the parallel-slot stator, and novel thrust plate to reduce the rotational power loss effectively, which is assembled by DT4 and nanocrystalline materials. Meanwhile, we have designed and assembled an axial hybrid magnetic bearing prototype with the novel stator and thrust plate, which is applied in the five-degrees-of-freedom reaction flywheel system with angular momentum of 15 Nms at 5000 r/min. It is validated by the experimental results.

플라이휠 에너지 저장장치를 위한 저 전력소모 하이브리드 마그네틱 베어링의 설계

For the application into a 1 kWh flywheel energy storage system(FESS), this paper presents the design scheme of radial and axial hybrid magnetic bearings which use bias fluxes generated by permanent magnets. In particular, the axial hybrid magnetic bearing is newly proposed in this paper, in which a permanent magnet is arranged in axial direction so that it can support the rotor weight as well as provide a bias flux for axial magnetic bearing. Such hybrid magnetic bearings consume very low power, compared with conventional electromagnetic bearings. In this paper, to stably support a 140 kg flywheel rotor without contact, design process is explained in detail, and magnetic circuit analysis and three-dimensional finite element analysis are carried out to determine the design parameters and predict the performance of the magnetic bearings.

A New Structure for Permanent-Magnet-Biased Axial Hybrid Magnetic Bearings

We propose a new structure for a permanent-magnet-biased axial hybrid magnetic bearing. Starting with the inner air gap and the outer air gap of conventional axial magnetic bearings, we first construct a novel air gap between the permanent magnet and the outer housing, which we call the second air gap, separating the bias flux paths from the control flux paths. As a result, the control flux paths will have lower reluctance, and the power loss of the axial magnetic bearing will be lower. Next, we modeled this axial hybrid magnetic bearing and analyzed it using the equivalent magnetic circuit method, 2-D finite element method (FEM), and 3-D FEM. We have designed and assembled an axial hybrid magnetic bearing prototype for a reaction flywheel system with angular momentum of 15 Nmiddotmmiddots at a speed of 5000 r/min. The theoretical analysis and the prototype experiments show such advantages as simple structure, good force current and force displacement, and high operating reliability.