Radial Suspension Research Articles

Triaxial Active Control Magnetic Bearing With Asymmetric Structure

A standard magnetic levitation system has several magnetic bearings (MBs) to levitate its rotor. However, the combined structure of MBs increases the system's axial length and size. To solve these problems, we propose a triaxial active control magnetic bearing (AMB) with an asymmetric structure. This study demonstrates the development of the proposed AMB using a prototype. Radial and thrust suspension force characteristics are shown and compared with analysis and measured results. Furthermore, a magnetic levitation test is conducted, and it shows that the rotor can levitate. In addition, stability against disturbances is evaluated using a sensitivity function, and loss characteristics when the rotor is rotated are measured and discussed.

Suspension Performance Analysis on the Novel Hybrid Stator Type Bearingless Switched Reluctance Motor

To solve the coupling between torque and suspension force in the conventional bearingless switched reluctance motor (BSRM) and improve suspension performances, the novel hybrid stator type bearingless switched reluctance motor (HSTBSRM) with double-slice structures is proposed. The torque magnetic circuit is completely independent of the suspension magnetic circuit, and the natural decoupling between the torque and suspension force is achieved. First, the structure, magnetic circuits, suspension, and rotation mechanism are analyzed. The mathematical models of radial suspension forces are deduced in detail. According to the maximum radial bearing capacity, the main parameters of the suspension part are designed. Finally, the 3-D finite-element analysis is carried out to verify the magnetic circuit, suspension mechanism, and models.

Research on the Modelling of a Single-winding Bearingless Permanent Magnet Brushless DC Motor

This paper studies the radial suspension force mathematical model of a single-winding bearingless permanent magnet brushless DC motor, which provides a theoretical basis for the precise control of a single-winding motor. First, the physical structure of the single-winding BL-BLDC motor and the principle of radial suspension force generation are introduced. Then, the equivalent magnetic circuit method is used to establish the electromagnetic relationship inside the motor and the virtual displacement method is used to derive and calculate the mathematical model of the radial suspension force. The radial suspension force of the motor is composed of the force generated by the suspension force winding and the unbalanced magnetic pull force generated by the motor rotor deviating from the center position. Finally, the finite element analysis software is used to model and simulate the single-winding motor to analyze the change of the suspension force amplitude under different currents and the influence of different eccentric displacements on the unbalanced magnetic tension of the motor. The results show that the error between the simulation results obtained by the FEA and the theoretical calculation results of the mathematical model is small, which verifies the correctness of the radial suspension force mathematical model of the single-winding BL-BLDC motor.

Principle and performance analysis for six‐pole hybrid magnetic bearing with a secondary air gap

In order to reduce the non-linearity of radial suspension forces of the three-pole hybrid magnetic bearing and further reduce the cost and power consumption, an AC six-pole hybrid magnetic bearing with secondary air gaps is proposed. First, the structure and working principle of the AC six-pole hybrid magnetic bearing with secondary air gaps are introduced, and the mathematical model of suspension forces are derived. Second, on the basis of the mathematical model, the linearity and coupling characteristics of the radial suspension forces are analysed, and then the suspension forces are simulated and verified by the finite element method (FEM). Then, the correlation performance indexes are compared with the six-pole hybrid magnetic bearing without secondary air gaps. Finally, an experimental platform is built, and suspension and disturbance tests are carried out. The research results show that the maximum bearing capacity of the six-pole hybrid magnetic bearing with secondary air gaps is 184% of the six-pole hybrid magnetic bearing without secondary air gaps.

Design and analysis of a high‐integration and low‐loss bearingless flywheel motor in vehicle

This study investigates an outer rotor bearingless flywheel motor for flywheel batteries in vehicle that exhibits the advantages of high integration and low loss due to outer rotor direct-drive and bearingless technologies. A hybrid excitation outer rotor bearingless flywheel motor with four-degrees-of-freedom radial suspension and permanent magnet bias is also proposed, further improving the advantages of high integration and low loss. In addition, suspension force density is ameliorated and suspension–torque coupling is reduced through structure design. To verify the aforementioned advantages of hybrid excitation outer rotor bearingless flywheel motor, its working principles are introduced and its electromagnetic characteristics are analyzed using the finite element method. Comparisons with 12/8 ORBFM are also conducted by focusing on suspension loss and suspension force density.

Structure and Suspension Force Analysis of Six-Pole Five Degrees of Freedom AC Hybrid Magnetic Bearing

A novel six-pole five degrees of freedom (5-DOF) ac hybrid magnetic bearing (HMB) is put forward in this article, which can obtain large suspension force density, high critical speed, and reduce the nonlinearity of radial suspension force. First, the structure and suspension principle are introduced in detail and then the mathematical models of the radial and axial suspension force are derived based on the equivalent magnetic circuit analysis. Second, the main parameters are designed according to the given maximum radial and axial bearing capacities. Finally, the prototype of the six-pole 5-DOF ac HMB is established by the 3-D finite-element analysis software Magnet. Moreover, the electromagnetic analysis is carried out to verify the rationality of the magnetic circuits and suspension mechanism. Furthermore, the force-current relationships are calculated. The research results have shown that the proposed six-pole 5-DOF ac HMB has reasonable structure and good suspension performances.

Open-Circuit Fault Control Techniques for Bearingless Multisector Permanent Magnet Synchronous Machines

This article presents three-phase and single-phase open-circuit fault-tolerant control strategies of radial suspension force and torque generation for bearingless multisector surface mounted permanent magnet synchronous machines. A combined winding topology is installed in the stator so that each phase contributes to both suspension force and motoring torque production. Indeed, a triple sectored three-phase winding is employed. Each three-phase winding is supplied by a power converter to independently control the suspension force vector and torque over each sector. An analytical formulation of the force and torque generation is described considering both three-phase open-circuit and single-phase open-circuit fault conditions. The analytical models of the machine are presented in a generalized matrix form so that they can be applied to any machine with a multisector winding structure. The analytical models are then used to derive the control algorithms that allow us to control the bearingless machine when a whole three-phase winding or one phase of one or two sectors are open circuited. The theoretical analysis is verified with both finite elements analysis and experiment tests. This system shows a good open-circuit fault-tolerant capability.

Structural optimization of radial containment ultrasonic suspension bearing

Structural optimization of radial containment ultrasonic suspension bearing

Research on combination of passive magnetic bearing and mechanical bearing for vertical axis wind turbine

Aiming at the “light wind start, light wind power generation” of vertical axis wind turbine, a new T-shaped radial passive magnetic bearing with high suspension characteristics is proposed. Passive magnetic bearings used in vertical axis wind turbines usually have small bearing capacity and difficult magnetization. The new T-shaped radial PMB can improve the radial bearing capacity, and the three magnetic rings all adopt simple axial magnetization. The new T-shaped radial PMB is combined with mechanical auxiliary bearing to form the suspension system of wind turbine. In the stable state, the suspension system can realize radial and axial stable suspension. The structure and working principle of the suspension system are briefly described. Through the finite element simulation, the characteristics of the new T-shaped radial PMB, the traditional double-ring PMB and the T-shaped PMBs are compared. Taking the high bearing capacity and high stiffness of the new T-shaped radial PMB as the optimization objective, the multi-objective optimization of the new T-shaped radial PMB was carried out by changing its geometric parameters (inner diameter, magnetization length and air gap). The research results show that: Under the same bearing capacity, the volume of the new T-shaped radial PMB is reduced by about 78.64%. Under the same volume, its bearing capacity increased by about 30.7%, and its stiffness increased by about 96.1%. After optimization, its radial bearing capacity increased to 101.38 N, and its stiffness increased to 202.76 N/mm.

Principles and Implementation of a Novel Radial-Anti-Disturbance Bearingless Switched Reluctance Motor

In order to solve the problem that the vehicle flywheel battery is easy to be disturbed in the process of using, a novel radial-anti-disturbance bearingless switched reluctance motor (RADBSRM) is proposed and studied based on the double stator switched reluctance motor. By widening the width of rotor poles, the flat top regions of all main winding inductances for each phase are constructed. By adopting the two-phase-conducting decoupling control rules, the electromagnetic torque and the main levitation force can be provided simultaneously. The auxiliary windings and the permanent magnet comprised in the inner stator can provide auxiliary radial suspension force, which can increase the radial load capacity, and also reduce the power consumption for suspension. The basic topology, operation principle, control method, and electromagnetic characteristics were all analyzed. Compared with double stator bearingless switched reluctance motor (DSBSRM), the results of finite element analysis method (FEM) verified that the capacity and stability of radial suspension force are both improved.

A Novel Dual-Channel Bearingless Switched Reluctance Motor

Bearingless switched reluctance motor (BSRM) has the advantages of high integration and low loss, and is especially suitable for flywheel batteries. In order to enhance the reliability and fault tolerance ability of BSRM, a novel dual-channel BSRM is proposed in this paper. This motor has the combined merits of switched reluctance motor and magnetic bearing, and can realize dual-channel fault-tolerant operation. The scalloped rotor poles are evenly distributed on the inner and outer walls of the rotor. All rotor poles are specially widened, which is benefit for raising the continuity of radial suspension force. Through the dual-phase-conduction decoupling control rules, the electromagnetic torque and suspension force can be generated simultaneously without serious coupling problem. The basic topology, operation principle, control method, and electromagnetic characteristics are analyzed. Field-circuit coupling joint simulation results of Simplorer and Maxwell confirm the feasibility of the proposed novel motor and the validity of decoupling control method.

A Novel Axial Split Phase Bearingless Flywheel Machine With Hybrid-Inner-Stator Permanent Magnet-Based Structure

This article proposes a topology of special axial split phase (ASP) bearingless switched reluctance (BSR) machine for flywheel applications named ASP-bearingless flywheel (ASP-BF) machine, which adopts hybrid-inner-stator permanent magnet (PM) structure and exhibits complete decoupling of torque and radial suspension force, four degrees-of-freedom (DOF) actively controlled suspension, high torque and radial force density. The topologies of conventional radial split phase (RSP)-BSR machines and the proposed ASP-BF machine are comparatively investigated. It is found that problems of conventional RSP-BSR machines, i.e., the radial suspension force generation dead zone and strong coupling of radial suspension force and torque, can be solved in ASP-BF machines and the suspension DOF can be doubled. Electromagnetic performances, including magnetic field distribution, inductance, torque, radial force are comprehensively investigated. Further, the concept of degree-of-coupling (DOC) is introduced, and the DOCs of the proposed machine and conventional machines are quantitatively analyzed and compared. It shows that the DOC of ASP-BF machine in two cases are 3.41% and 4.05%, less than a quarter of the conventional 8/10 pole machine (22% and 16%) and less than half of the 12/14 pole machine (8.57% and 11.3%). Finally, a 3 kW/100 Wh prototype is built and the experiments proved the validity.

Decoupling control based on linear/non‐linear active disturbance rejection switching for three‐degree‐of‐freedom six‐pole active magnetic bearing

In order to decouple the three-degree-of-freedom six-pole active magnetic bearing (3-DOF 6-pole AMB) with strong couplings, non-linear and multivariable, an linear/non-linear active disturbance rejection switching control (L/NL-ADRSC) strategy is put forward. Firstly, the configuration of the 3-DOF 6-pole AMB is presented, and the mathematics models of the radial and axial suspension forces are derived. Secondly, the advantages and disadvantages of linear active disturbance rejection control (LADRC) and non-linear active disturbance rejection control (NLADRC) are analysed, and the L/NL-ADRSC strategy is introduced. Thirdly, a L/NL-ADRSC system is designed to realise the decoupling control for the 3-DOF 6-pole AMB, and a simple practical parameter design method is provided. Finally, the simulations and experiments are carried out to verify the effectiveness of the whole control system. The results show that the decoupling control effect of L/NL-ADRSC is better than that of LADRC and NLADRC.

Suspension Force Analysis of Four-Pole Hybrid Magnetic Bearing With Large Radial Bearing Capacity

To make full use of the space and improve the radial bearing capacity, a new two-degree of freedom (DOF) four-pole radial hybrid magnetic bearing (RHMB) is researched in this article. This RHMB is characterized by that independent magnetic circuit is adopted, and the radial suspension winding is installed in the axial space. First, the structure and working principle are introduced. Second, the mathematical models are established and the main parameters of the prototype RHMB are designed. The 3-D finite-element analysis is carried out to analyze and calculate the magnetic circuit, suspension mechanism, and force–current relationship. Finally, the experimental system is built and the suspension force is tested. The research results have shown that the structure and magnetic circuit of the RHMB is reasonable and the mathematical model is correct.

A Novel Homopolar Four Degrees of Freedom Hybrid Magnetic Bearing

In this article, a novel four degrees of freedom (4-DOF) homopolar hybrid magnetic bearing (HMB) is put forward to reduce the magnetic field coupling of radial 4-DOF. It consists of two pairs of symmetrical radial stators and one rotor, and the radial stators on each side have two pieces, namely, X and Y stator core. Due to the special design of X and Y magnetic poles in the different radial stator cores, the magnetic circuits of X and Y channels are independent of each other. The configuration and operating principle of the homopolar HMB are first discussed, and then, the mathematical model of radial suspension force is deduced by the equivalent magnetic circuit method (EMCM). Besides, some main parameters are given in accordance with the given maximum radial suspension force. Finally, 3-D finite-element (FE) model of the homopolar 4-DOF HMB is established with MagNet software. Meanwhile, the magnetic flux distributions, the magnetic flux density, the force-current relationship of X channel with displacement and current of Y channel are simulated and analyzed. The simulation results indicate that the presented 4-DOF HMB has good performance, and the magnetic fields of X and Y channels decouple well from each other.

Parameter Design of Six-Pole Hybrid Magnetic Bearing Considering Variable Stiffness

Six-pole hybrid magnetic bearing (HMB) which driven by an inverter is a kind of high performance bearing with the advantages of small size and low cost. In order to overcome the disadvantage of the six-pole HMB that the working point of the rotor deviating from the given reference point, which affects the stable operation of the six-pole HMB system, the parameter design of the six-pole HMB is carried out in combination with the steady region determined by variable stiffness coefficient. Firstly, the structure and working principle of the six-pole HMB are described, and mathematical model of the radial suspension force in the x direction which considers static working point offset is derived by equivalent magnetic circuit method. Secondly, variable stiffness of the six-pole HMB which considers the static working point offset is analyzed, and the steady region of the stable operation of the six-pole HMB is obtained. Thirdly, combined with the delineated steady region, the parameter design of six-pole HMB is carried out. Finally, simulation and experimental results show that the six-pole HMB system has well performance of anti-interference, which proved that variable stiffness analysis provides a theoretical basis for the parameter design of the six- pole HMB.

Permanent Magnet Parameter Design and Performance Analysis of Bearingless Flux Switching Permanent Magnet Motor

Since the bearingless flux switching permanent magnet motor has a doubly salient pole structure of conventional flux switching permanent magnet motor, there are many problems, such as high cogging torque, high torque ripple, and the magnetic flux leakage produced by PMs, which affect the characteristics of the electromagnetic torque and suspension force. To overcome the shortcomings above, a novel method-right angle chamfering scheme, is investigated to reduce the cogging torque. Firstly, based on the given rated speed and rated power, the parameter ranges of the angle variables at both ends of the permanent magnets are designed by the empirical formulas. Then, under the condition that the torque and the power are reduced in allowable ranges, the electromagnetic characteristics, such as cogging torque, harmonic, electromagnetic torque, radial suspension force, and decoupling, are simulated and analyzed in detail. Based on the proposed design method, the compromise design of the above design objectives is considered and realized. Finally, the scheme of stator and rotor component is built, and the experimental results show that the effectiveness and feasibility of the scheme are verified.

Rotor Displacement Self-Sensing Modeling of Six-Pole Radial Hybrid Magnetic Bearing Using Improved Particle Swarm Optimization Support Vector Machine

An inverter-fed six-pole radial hybrid magnetic bearing (HMB) has the characteristics of compact structure, high support speed, long service life, and so on. However, using displacement sensors to detect rotor displacements leads to the problems of large volume, high cost, and low reliability. In this article, a self-sensing method using improved particle swarm optimization (IPSO) least square support vector machine (LS-SVM) is proposed, which eliminates the influences of displacement sensors fundamentally. The structure and working principle of six-pole radial HMB are introduced, and the mathematical model of its radial suspension force is deduced according to the equivalent magnetic circuit method. Based on the regression principle of the LS-SVM, the prediction model between the currents in control coils and the rotor displacements is established. Also, the performance parameters of LS-SVM are optimized by the IPSO algorithm, which realizes self-sensing modeling of rotor displacement. The simulation system for self-sensing modeling of rotor displacement for six-pole radial HMB is constructed, and floating experiment, static suspension experiment, dynamic suspension experiment, and disturbance experiment of the rotor are carried out, which verify the robustness and stability of the self-sensing method proposed.

Analytical modelling of radial suspension force in bearingless surface‐mounted PM synchronous motors considering static rotor eccentricity

In this study, a new analytical model is provided in order to calculate the radial suspension force in bearingless surface-mounted permanent magnet synchronous motor with static rotor eccentricity. The proposed model is based on the harmonic analysis of magnetic flux density, and considers the influence of both radial and tangential air-gap field components on the computation of radial suspension force. This model can reveal the generation mechanism of the radial suspension force and identify the generation sources of the force ripples. Furthermore, the magnitudes and frequencies of radial suspension force harmonics, and the relationship between the radial suspension force and rotor eccentric displacements can be accurately predicted by the proposed model. However, this model cannot be used for saturated machines. The analytical model is verified by finite-element analyses and the result of static experimental study.

Modeling and Performance Analysis on the Slice Hybrid Magnetic Bearing With Two Radial Air-Gaps

In order to reduce the axial length and increase the critical speed of the small magnetic suspension drive system, a new slice hybrid magnetic bearing (SHMB) with two radial air-gaps is proposed. The structure and suspension mechanism of the SHMB is introduced, and then the mathematical models of the radial suspension force are deduced using the equivalent magnetic circuit method. The suspension mechanism is proved. The radial and axial suspension forces are then calculated by the finite element method. The experimental prototype SHMB is finally designed and constructed. The stable suspension of the rotor is realized, and the suspension forces are measured. The results of the finite element calculation and experimental measurement verify the correctness of the mathematical models.