Design Of Magnetic Bearing Research Articles

Research on magnetic fluid precise localized lubrication thrust cylindrical roller bearing with low-friction micro-vibration and high load-bearing capacity

Abstract As the magnetic field that is difficult to be distributed in the existing magnetic fluid thrust cylindrical roller bearing structure, it is more difficult for the magnetic fluid to be evenly distributed inside the bearing raceway with the axial localized lubrication, which seriously affects the engineering application of the magnetic fluid bearing. To solve the magnetic field control problem that the magnetic fluid is uneasy to be accurately localized and adsorbed, a new type of magnetic fluid thrust cylindrical roller bearing is designed in this study, which shows good characteristics of low-friction, micro-vibration and high load-bearing capacity. The seat-ring is set as an annular raceway that can be used for magnetic fluid storage and matching with the roller lubrication system, and an annular permanent magnet is designed as an external magnetic field source to be placed below the annular raceway to adsorb the magnetic fluid on the friction surface. The structure design of the axial magnetic fluid localized lubrication bearing is reasonable, which is especially suitable for precision instruments with strict operating-conditions and precision-lubrication.

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

Simulation and parametric optimal design of active radial magnetic fluid bearing

Simulation and parametric optimal design of active radial magnetic fluid bearing

Simulation and parametric optimal design of active radial magnetic fluid bearing

Simulation and parametric optimal design of active radial magnetic fluid bearing

Design and Unbiased Control of Nine-Pole Radial Magnetic Bearing

Typical radial active magnetic bearings are structurally symmetric. For example, an eight-pole bearing uses two opposing pairs to control one axis by winding the pair in series. The magnetic force produced by an active magnetic bearing is quadratically proportional to coil currents and inversely proportional to the square of the gap between the bearing and the journal. Bias linearization is widely used to linearize the relationship of coil currents to the magnetic force. However, the bias currents increase ohmic losses and require a larger than necessary capacity of power amplifiers to supply the sum of bias and control currents. Unbiased control of symmetric bearings has the critical issue of slew-rate limiting. Unbiased control of unsymmetrical bearings can eliminate the need for bias currents while avoiding slew-rate singularity except in extreme cases. Although a generalized inversion of the force–current relationship of unbiased unsymmetrical bearings has been proposed previously, no experimental validation is reported. The main objective of this research is to implement the unbiased control strategy and show that exactly the same linear control strategy for eight-pole symmetric bearings can be applied to nine-pole unsymmetrical bearings on industry-scale compressor test rigs. Two test rigs are built: one with eight-pole symmetric bearings and another with nine-pole unsymmetrical bearings. Linear control algorithms are designed and applied. Both control algorithms are linear and consist of lead filters and notch filters. The test results show that the linear control design used for unsymmetrical bearings can achieve the same level of stability that the symmetric bearings provide, satisfying the sensitivity criterion specified by ISO 14839-3.

Design and Implementation of a Low-Cost Active Magnetic Bearing

Design and Implementation of a Low-Cost Active Magnetic Bearing

Design and speed control of U-type 3-coil active magnetic bearing

Design and speed control of U-type 3-coil active magnetic bearing

Modeling, Design and Suspension Force Analysis of a Novel AC Six-Pole Heteropolar Hybrid Magnetic Bearing

To improve the radial suspension force of heteropolar hybrid magnetic bearing (HMB), a novel AC six-pole heteropolar HMB is proposed. Firstly, the structure, magnetic circuit, and suspension force generation principle are introduced and analyzed. Secondly, the equivalent magnetic circuits are established. The mathematical models of magnetic resistances, air gap magnetic fluxes, and levitation force are derived by node magnetomotive force (MMF) method. The main parameters of prototype heteropolar HMB, such as outer and inner air-gap length, winding turns, and permanent magnets, are designed. Then, the analysis model is established by MagNet 3D. The magnetic circuit, air-gap flux density, suspension mechanism, force-current relationships, force-displacement relationships, and force coupling characteristics are analyzed and calculated. Finally, the experimental system was built to test the levitation force and levitation displacement waveforms. The research results have shown that the proposed novel six-pole heteropolar HMB has a reasonable structure and magnetic circuit. The design method is also proven to be correct. Furthermore, it is compared with the traditional heteropolar six-pole HMB, the maximum suspension forces in the X and Y directions are increased by 1.96 and 2.02 times, respectively.

Structure Design and Optimization of the Radial Magnetic Bearing

According to different working environments and functional requirements, radial magnetic bearings (RMBs) have various design methods. Some methods’ lack of effectiveness or accuracy is likely to cause significant differences in the structural performance of magnetic bearings, which will cause serious problems such as limited bearing capacity and complex control. This paper analyzes the structure topology of a magnetic bearing according to the application scenario of RMBs, then proposes a general design example of an 8-pole magnetic bearing based on magnetic circuit analysis and reveals the linearity between electromagnetic force and current as well as air gap through finite element analysis and the influence of magnetic saturation on the load capacity of the magnetic bearing structure. After completing the preliminary design, we further optimize the structure, take the genetic algorithm as an example to iterate the influence coefficient, and summarize and prospect. The design scheme and optimization method proposed in this paper only provide a valuable reference for researchers and factories when devising RMB devices.

Design and Implementation of Novel Homopolar Magnetic Bearings Incorporated in Reaction Wheel for Satellite Attitude Control

Design and Implementation of Novel Homopolar Magnetic Bearings Incorporated in Reaction Wheel for Satellite Attitude Control

Design and Optimization of a Radial Magnetic Bearing Considering Unbalanced Magnetic Pull Effects for Magnetically Suspended Compressor

In magnetic suspended centrifugal compressors, the unbalanced magnetic pull (UMP) may cause saturation on power amplifier currents driving the coils of the active magnetic bearing (AMB), eventually affecting the stability of the rotor. This article addresses the issue on the stable operation of the AMB-rotor system subject to the UMP. A mathematical model of the UMP with uneven magnetization of permanent magnet (PM) and eccentricity is proposed for a surface-mounted PM synchronous motor supported by magnetic bearings. Based on this model, an improved radial magnetic bearing (RMB) with control and bias separated coil structure is designed and optimized to decrease the compensation current used to balance the UMP. First, a mathematical model containing the unevenness of the magnetization and eccentricity is established to estimate the UMP. Next, the compensation current for the UMP is analyzed based on the UMP model. Then, with the aim of minimizing the compensation current, the proposed RMB is optimized under the constraints of the starting current, the magnetic bearing volume, and the coil current density. The compensation current of the optimized RMB is reduced by 25%, compared with that of the original RMB. Finally, the experimental results on a 132-kW magnetic suspended centrifugal compressor, equipped with the optimized RMB, show the effectiveness of the modeling and optimization design.

Magnetic Circuit Design and Experiment of Novel Lorentz Magnetic Bearing with Double Air Gap

A uniform magnetic density distribution in the air gap is key for the Lorentz magnetic bearing to achieve high precision control and large torque output. To overcome the small magnetic field strength in an explicit magnetic bearing and a high magnetic density fluctuation rate in an implicit Lorentz magnetic bearing, a second air gap design method is proposed based on the maximum magnetic density distribution in the winding area. A novel Lorentz bearing with a double second air gap is designed. The maximum magnetic field strength in the winding area is calculated by the finite element method, and the structure of the double second air gap is designed. To reduce the calculation error of the magnetic field strength, the division of the reluctance by the magnetic induction line is proposed. The reluctance calculation formula is given. Based on Ohm’s law, the calculation of the magnetic field strength is obtained. Finally, a prototype of the novel Lorentz magnetic bearing is made. The magnetic field strength in the winding area and the magnetic density fluctuation rate are measured with a magnetic density measurement instrument. The maximum magnetic flux density in the winding area is 0.631 T, and the magnetic field strength is 0.58%. Less difference is found between the measurement result and the finite element result.

A Novel Hybrid Analytical Model of Active Magnetic Bearing Considering Rotor Eccentricity and Local Saturation Effect

To facilitate the active magnetic bearing (AMB) design and analysis, an accurate and fast model that considers both rotor eccentricity and the saturation effect is necessary. In this article, a novel hybrid analytical model (HAM) for effective calculation of the magnetic field of the AMB is proposed. Eccentricity and local saturation are considered in the proposed HAM. In the proposed HAM, the stator and rotor are modeled by elementary subdomains (ESDs) and the air-gap is modeled by magnetic equivalent circuit (MEC). Direct coupling between the solutions in the ESD regions with MEC completes the whole model matrices. Compared to the existing literature, the proposed model considers both the rotor eccentricity and material nonlinearity. The effectiveness and accuracy of the proposed HAM are validated by both the finite element model and experimental results. The results show that the proposed HAM can accurately predict the magnetic quantities of the AMB.

Finite element analysis and optimization of active magnetic bearings for contra-rotating coaxial rotor system

This paper presents the design, analysis and optimization of active magnetic bearings (AMBs) to support the inner rotor in a contra-rotating coaxial rotor system. An FEM based rotordynamic model is developed using 8-dof Timoshenko beam elements assuming both inner and outer rotors to be flexible. The dynamic response of this system due to an unbalanced force is used in one of the constraints of a multi-objective genetic algorithm for controlling the vibration amplitude within 10% of the air gap. A maximum reduction of 46.9% in the amplitude peak is obtained under the present conditions. Hence, this work also offers a tool useful in touch-down bearing design. The PD controller gains are found to govern the stiffness and damping properties of the AMB. On increasing the mass unbalance by a factor of 2.5, number of turns, pole width and maximum current are found to increase by 52.9%, 29.4% and 71.67% respectively.

Gain-Scheduled Control of Asymmetric Thrust Magnetic Bearing

The thrust position of the magnetic levitation rotor can be changed, bringing convenience to the practical application of cold compressors. This paper derives the mathematical model of asymmetric thrust magnetic bearings for a cold compressor and analyzes the changes in the system characteristics with the equilibrium position. By constructing PID controllers associated with the structural parameters of the magnetic bearing, the adaptive adjustment of the control parameters under different balanced position commands is realized. The simulation and experimental results prove that the gain-scheduled control method proposed in this paper can achieve a robust stability of the rotor in the range of 50 to 350 μm, and not at the cost of the response speed, adjustment time, and overshoot. The research results have reference significance for the structure design of asymmetric thrust magnetic bearings and play an important role in the commissioning and performance improvement of cold compressors.

Improved design and analysis of a radial magnetic bearing with paired‐pole or alternating‐pole configurations

The magnetic saturation of iron-core will reduce the maximum output force, influence the linear force characteristic and control precision of the magnetic bearing. To avoid these problems, a modified iron-core design rule for the alternating-pole magnetic bearing is proposed. The thickness of both stator yoke and rotor journal should be designed as 3/4 of the stator pole width for the alternating-pole configuration, which is successfully verified by 3D finite element method and experiments. Based on the improved design, the structural sizes, rotor iron losses, and force coupling characteristics of the paired-pole configuration and the alternating-pole configuration are compared. The results show that the size of the alternating-pole bearing is smaller than that of the paired-pole bearing; the alternating-pole configuration generates slightly higher rotor iron loss than the paired-pole configuration; the coupling strength of the alternating-pole configuration is stronger than that of the paired-pole configuration irrespective of whether the magnetic force coupling is caused by rotor displacements or control currents. The presented method and results can provide a reference for the design and selection of the active magnetic bearings.

Analytical modeling and experimental validation of the six pole axial active magnetic bearing

The article presents a novel design of the axial active magnetic bearing with six poles. An analytical magnetic bearing model was developed to provide the axial magnetic induction distribution in 3D. The model utilizes magnetic vector potential formulation and Schwarz-Christoffel mapping. The paper covers in-depth deliberations on the end effect influence and the conjugate complex permeance function. Numerical model and simulations were provided in 3D mode with support of COMSOL Multiphysics software. The six pole axial active magnetic bearing was manufactured and investigated experimentally. Identification of the magnetic field distribution was carried out with a single axis magnetic induction sensor using custom automatic field scanner. High convergence of the modeling results and experimental research was demonstrated. The main advantage of the proposed analytical method is significantly shorter computation time compared to the numerical one that is useful from the modeling and controller study point of view. The configuration, modeling, simulation and experimental investigation results are well illustrated for the better overview.

Passive Radial Bearing With Active Damper for Downhole Natural Gas Compressor

Design of radial passive magnetic bearings with active dampers (radial PMB-AD) and their application in a down-hole natural gas compressor (DHGC) are discussed. These compact and reliable bearings allowed noncontact suspension of a high-speed DHGC rotor spinning at 50 kr/min in a highly adverse environment more than 3 km (10 000 ft) below the ground with temperatures reaching 100 °C. The design was further complicated by the space limitations imposed by a well casing. The paper presents the design of PMB-AD modules, as well as their integration and testing as a part of a DHGC.

Design of the Six-Pole Hybrid Magnetic Bearing With Separated Magnetic Circuit to Generate Symmetrical Levitation Force

To solve the problem of generating the different two-degree-of-freedom (two-DOF) maximum levitation forces, a novel six-pole hybrid magnetic bearing (HMB), adopted combined stator and magnetic path structure, and its design method are proposed. Firstly, the configuration of the combined magnetic circuits and levitation principle are introduced. Then, the force-current relationships are derived. Furthermore, according to flux saturation, the permanent magnetic flux density is designed. Moreover, the combined magnetic circuit, force-current curves and design method are calculated and analyzed by Magnet 3D. Finally, the levitation forces are tested. The combined stator, levitation principle, force-current relationship and the design are proved to be correct.

Study and analysis on some design aspects in single and multi-axis active magnetic bearing (AMB)

Active magnetic bearing (AMB) is a substitute of conventional bearing, which provides electromagnetic force to support the rotating part respecting the stator. The utilization of electromagnetic force makes this bearing “active”. The attraction force of an AMB system can be control by manipulating the input so that the rotor can be levitate at required position. As lot of limitation exist in passive magnetic bearing, the AMB is very useful in modern applications. Due to frictionless nature of magnetic bearing and non-necessity of lubricants, now-a-days AMB is taking place as the alternate of any other bearing in multiple applications of growing industry. Adequate knowledge of essential components is necessary for successful implementation of any active magnetic bearing design. So, In this paper, the magnetic analysis has been analyzed for the different types of single and multi-axis AMB using ANSYS Maxwell with extensively reviewed components.