Radial-axial Magnetic Bearing Research Articles

The cross-coupling problem caused by the structure of a combined radial-axial magnetic bearing for DC motors

Different from separated magnetic bearing units, combined radial-axial magnetic bearing (CRAMB) has cross coupling problem caused by structure itself. This paper focuses on the study of cross coupling problem for a CRAMB caused by structure itself. A

Suspension force analysis of six-pole radial-axial magnetic bearing for energy storage flywheel

This paper proposes a six-pole radial-axial hybrid magnetic bearing (RAHMB) used in a flywheel system. The radial and axial bias fluxes are generated by one permanent magnet and the radial control coils are driven by a three-phase converter. So, it has the advantages of compact structure, low power consumption and simple driver. First, the work principle is introduced. Then, the mathematical model is built. The force-current characteristics with different eccentricities, the coupling between radial two degrees of freedom (DOF) and the coupling between radial and axial DOF are analyzed based on the analytical model. Finally, the analyses are validated by 3D finite element analysis in the Maxwell software. The results have shown that the coupling between radial and axial DOF is very small. However, the force-current curves of radial two DOFs turn out to be nonlinear and coupled with the increase of rotor eccentricity.

Weight-Reduction Design Based on Integrated Radial-Axial Magnetic Bearing of a Large-Scale MSCMG for Space Station Application

For space application, weight and power consumption are the key parameters of an actuator for attitude control of spacecraft. In this paper, weight-reduction design based on a novel combined radial-axial magnetic bearing (CRAMB) in a large-scale magnetically suspended control moment gyro (MSCMG) for space station application is proposed. The CRAMB consists of a radial magnetic bearing (RMB) unit and an axial magnetic bearing (AMB) unit. Two CRAMBs can control the 5-degrees of freedom of the high-speed magnetically suspended rotor. According to the requirement of a large MSCMG for a space station, the CRAMB with permanent magnet bias is modeled (based on an equivalent magnetic circuit method), designed, and tested. Compared with the original magnetic bearings in MSCMG fabricated, the number of magnetic pole is reduced from eight to four for RMB unit based on the CRAMB, the weight of magnetic bearings can be reduced from 35.4 to 30.8 kg (reduced by 4.6 kg), and the volume is reduced from $\text{0.00456}$ to $\text{0.00394}\; \text{m}^{3}$ (reduced by 16.3%), when the MSCMG outputs the same angular momentum of 1200 N · m · s and the same torque of 209 N·m. The maximum power consumption of the proposed CRAMB system is decreased by 15.6%.

Design, Modeling, and Performance Testing of a Weak Coupling Combined Radial–Axial Magnetic Bearing

Most combined radial–axial magnetic bearing (CRAMB) is usually composed of a radial magnetic bearing (RMB) unit and an axial magnetic bearing (AMB) unit. The coupling problems in different degrees of freedom (DOF) will make it difficult to design the controller and influence dynamic characteristics of the magnetic bearing system (MBS). In this paper, the coupling stiffness models of a CRAMB between the RMB unit and the AMB unit affected by radial-displacement and axial-displacement are presented using equivalent magnetic circuit method. The CRAMB and the testing system are designed and fabricated. The coupling stiffness model is verified by the experimental results. The weak coupling characteristics between the radial-direction and axial-direction is beneficial to design the controller and dynamic stability control for the CRAMB system.

Multi-objective Optimization of a Combined Radial-Axial Magnetic Bearing for Magnetically Suspended Compressor

The combined radial-axial magnetic bearing (CRAMB) with permanent magnet (PM) providing bias magnetic flux is designed for magnetically suspended high-speed electromotor in the compressor for its compact construction. In this paper, the design principle and the initial model of CRAMB are introduced. To improve the performances of CRAMB and better meet the engineering requirements, the optimization is conducted on the bearing. Considering the incompatible objectives of the optimization model, the method of multiobjective optimization (MOO) on the bearing is proposed, which can balance these objectives compared with single-objective optimization (SOO). The objectives and constraints are provided in the form of analytical expressions by means of equivalent magnetic circuit whose rationality is demonstrated by finite-element method (FEM). To optimize the bearing efficiently, the integrated optimum methodology is adopted. After MOO process, the synthetical performances are improved, which are verified by FEM and experiment.

Modeling and Analysis of Coupling Performance of Dynamic Stiffness Models for a Novel Combined Radial-Axial Hybrid Magnetic Bearing

The combined radial-axial magnetic bearing (CRAMB) with permanent magnet creating bias flux can reduce the size, cost, and mass and save energy of the magnetic bearing. The CRAMB have three-degree-of-freedom control ability, so its structure and magnetic circuits are more complicated compared to those of the axial magnetic bearing (AMB) or radial magnetic bearing (RMB). And the eddy currents have a fundamental impact on the dynamic performance of the CRAMB. The dynamic stiffness model and its cross coupling problems between different degrees of freedom affected for the CRAMB are proposed in this paper. The dynamic current stiffness and the dynamic displacement stiffness models of the CRAMB are deduced by using the method of equivalent magnetic circuit including eddy current effect, but the dynamic current stiffness of the RMB unit is approximately equal to its static current stiffness. The analytical results of an example show that the bandwidth of the dynamic current stiffness of the AMB unit and the dynamic displacement stiffness of the CRAMB is affected by the time-varying control currents or air gap, respectively. And the dynamic current stiffness and the dynamic displacement stiffness between the AMB unit and the RMB unit are decoupled due to few coupling coefficients.

전자석 바이어스 Diskless반경방향-축방향 일체형 자기 베어링 해석

The theory for a new electromagnetically biased diskless combined radial and axial magnetic bearing is developed. A typical magnetic bearing system is composed of two radial magnetic bearings and an axial magnetic bearing. The axial magnetic bearing with a large axial disk usually limits rotor dynamic performance and makes assembling and disassembling difficult for maintenance work. This paper proposes a novel electromagnet biased integrated radial-axial magnetic bearing without axial disk. This integrated magnetic bearing uses two axial coils to provide the bias flux to the radial and axial air gaps of the combined bearing. The axial magnetic bearing unit in this combined magnetic bearing utilizes reluctance forces developed in the non-uniform air gaps such that the axial disk can be removed from the bearing unit. The 4-pole homopolar type radial magnetic bearing unit is also designed and analyzed. Three dimensional finite element model for the bearing is also developed and analyzed to illustrate the diskless combined magnetic bearing.

Design and analysis of a new permanent magnet biased integrated radial-axial magnetic bearing

A typical magnetic bearing system is composed of two radial magnetic bearings and an axial magnetic bearing. The axial magnetic bearing with a large axial disk usually limits rotor dynamic performance and makes assembling and disassembling difficult for maintenance work. This paper proposes a novel permanent magnet biased integrated radial-axial magnetic bearing without axial disk. The axial magnetic bearing unit in this integrated magnetic bearing utilizes reluctance forces such that the axial disk can be removed from the bearing unit. The 4-pole homopolar type radial magnetic bearing unit is also designed and analyzed. 3-D flux analysis is provided to illustrate the novel diskless integrated magnetic bearing.