Magnetic Bearing Research Articles

Search for optimal parameters of active structural suspension elements by determining their integral stiffness and damping characteristics

The paper presents an approach to the modelling of the “Rotor in active magnetic bearings” system and the subsequent search for optimal support parameters to ensure non-resonant operation of the machine in the entire range of operating rotational speeds. The object of the study is active magnetic bearings for the rotor of an industrial fan for local ventilation of the mine, which was previously installed in the rolling element bearings and due to the lack of the necessary load on them, have large frictional efficiency losses. To solve the problems with the loss of efficiency, it is proposed to use active magnetic bearings with a control system based on a proportional-integral-derivative controller with control principles of single input-single output, which is a cheaper and simpler system to implement compared to multiple input-multiple output systems, however, can be an effective tool for solving the described problems in the operation of the machine. The subject of the study is the dynamics of the rotor of an industrial fan in active magnetic bearings, which are modeled using spring-damper elements with stiffness and damping coefficients which are determined using the approach developed in the work. It is based on the representation of active magnetic bearings as an electromechanical system with components the dynamics of which are described by transfer functions in the frequency domain. The formation of the transfer function of the active magnetic bearing as a whole and its subsequent inclusion in the system of rotor dynamics equations allows obtaining relatively simple dependences of the stiffness and damping coefficients of the bearings on the rotor rotational speed. These dependencies contain the physical parameters of active magnetic bearing components and the parameters of their control systems which allows not only simulating the dynamics of the rotor in such bearings, but also searching for their optimal parameters, in particular, the value of the bias current in the electromagnets, which is necessary to ensure the absence of resonances of the rotor with synchronous excitation loads in the entire range of operating rotational speeds, which is confirmed by plotting the dependences of the rotor critical speeds on the bias current, as well as the Campbell diagram for the optimal value of the bias current.

Study on type of magnetic suspension rotor groove and wear of drop touchdown bearing

The active magnetic bearing (AMB) is widely used in the field of flywheel energy storage system (FESS) in wind power generation. This study mainly studies the magnetic suspension rotor groove (MSRG) of FESS and the wear of drop touchdown bearing (DTB). The mathematical model of air gap magnetic field waveform on stator surface and Plath equation of control in air gap region were established. Contrastive analysis of conventional, second harmonic and third harmonic ‘petal-shaped’ MSRG in AMB. The life test of DTB on magnetic suspension rotor was carried out for 24000r/min and lasted for 1500 h. The second harmonic ‘petal-shaped’ MSRG could not only generate reluctance torque and increased the torque density of the motor, but also increased the fundamental component and excitation torque component by reducing the peak value of the magnetic field. The temperature ranges of front and rear DTB were ‘30℃–46℃’ and ‘26℃–40℃’, respectively. After service, the maximum thickness of metamorphic layer in the DTB raceway was 6 μm. After service, the content of Fe in the metamorphic layer of DTB raceway decreased by 10.11% and the content of C increased by 2.41%. Raceway hardness of DTB after service was 59.67 HV higher than that before service.

An Overview of the R&D of Flywheel Energy Storage Technologies in China

The literature written in Chinese mainly and in English with a small amount is reviewed to obtain the overall status of flywheel energy storage technologies in China. The theoretical exploration of flywheel energy storage (FES) started in the 1980s in China. The experimental FES system and its components, such as the flywheel, motor/generator, bearing, and power electronic devices, were researched around thirty years ago. About twenty organizations devote themselves to the R&D of FES technology, which is developing from theoretical and laboratory research to the stage of engineering demonstration and commercial application. After the research and accumulation in the past 30 years, the initial FES products were developed by some companies around 10 years ago. Today, the overall technical level of China’s flywheel energy storage is no longer lagging behind that of Western advanced countries that started FES R&D in the 1970s. The reported maximum tip speed of the new 2D woven fabric composite flywheel arrived at 900 m/s in the spin test. A steel alloy flywheel with an energy storage capacity of 125 kWh and a composite flywheel with an energy storage capacity of 10 kWh have been successfully developed. Permanent magnet (PM) motors with power of 250–1000 kW were designed, manufactured, and tested in many FES assemblies. The lower loss is carried out through innovative stator and rotor configuration, optimizing magnetic flux and winding arrangement for harmonic magnetic field suppression. Permanent magnetic bearings with high load ability up to 50–100 kN were developed both for a 1000 kW/16.7 kWh flywheel used for the drilling practice application in hybrid power of an oil well drilling rig and for 630 kW/125 kWh flywheels used in the 22 MW flywheel array applied to the flywheel and thermal power joint frequency modulation demonstration project. It is expected that the FES demonstration application power stations with a total cumulative capacity of 300 MW will be built in the next five years.

Noncontact Rotor Vibration Velocity Sensor and Its Application to Vibration Control of a Flexible Rotor on Active Magnetic Bearings

Noncontact Rotor Vibration Velocity Sensor and Its Application to Vibration Control of a Flexible Rotor on Active Magnetic Bearings

Nonlinear dynamics and motion bifurcations of 12-pole variable stiffness rotor active magnetic bearings system under complex resonance

In this study, we analyze the nonlinear dynamic characteristics of a 12-pole variable stiffness rotor active magnetic bearings (rotor-AMBs) under intricate resonance conditions. Using the principles of electromagnetic bearings, a model for the 12-pole variable stiffness rotor-AMBs system is developed. Next, the dynamic equations for a two-degree-of-freedom 12-pole variable stiffness rotor-AMBs system are derived, incorporating both quadratic and cubic nonlinearities, through Newton's second law. Considering the primary parametric resonance, 1:1 internal resonance, and 1/2 subharmonic resonance, the multiple time scale perturbation method is applied to derive the average equation of the system. Based on these averaged equations, the characteristics and complex dynamics of the system are analyzed. Finally, MATLAB software is employed for numerical simulations of the 12-pole variable stiffness rotor-AMBs system. The simulation results indicate that the nonlinear control parameters can modify the system's softening and hardening spring behaviors. Varying the parametric excitation amplitude leads to diverse dynamic behaviors, including single-periodic motion, double-periodic motion, and chaotic vibrations.

Review on high-temperature superconducting REBCO trapped field magnets

Abstract Superconducting (SC) magnets can generate exceptionally high magnetic fields and can be employed in various applications to enhance system power density. In contrast to conventional coil-based SC magnets, high-temperature superconducting (HTS) trapped field magnets (TFMs), namely HTS trapped field bulks (TFBs) and trapped field stacks (TFSs), can eliminate the need for continuous power supply or current leads during operation and thus can function as super permanent magnets. TFMs can potentially trap very high magnetic fields, with the highest recorded trapped field reaching 17.89 T, achieved by TFSs. TFMs find application across diverse fields, including rotating machinery, magnetic bearings, energy storage flywheels, and magnetic resonance imaging (MRI). However, a systematic review of the advancement of TFMs over the last decade remains lacking, which is urgently needed by industry, especially in response to the global net zero target. This paper provides a comprehensive overview of various aspects of TFMs, including simulation methods, experimental studies, fabrication techniques, magnetisation processes, applications, and demagnetisation issues. Several respects have been elucidated in detail to enhance the understanding of TFMs, encompassing the formation of HTS bulk composites and TFSs, trapped field patterns, enhancement of trapped field strength through pulsed field magnetisation (PFM), as well as their applications such as SC rotating machines, levitation, and Halbach arrays. Challenges such as demagnetisation, mechanical failure, and thermal instability have been illuminated, along with proposed mitigation measures. The different roles of ferromagnetic materials in improving the trapped field during magnetisation and in reducing demagnetisation have also been summarised. It is believed that this review article can provide a useful reference for the theoretical analysis, manufacturing, and applications of TFMs within various domains such as materials science, power engineering, and clean energy conversion.

Suppression of synchronous current of active magnetic bearings considering radial displacement inconsistency

Suppressing rotor synchronous current is vital for achieving precise control in active magnetic bearing (AMB) rotor systems. The displacement amplitude inconsistency in orthogonal channels presents new challenges for synchronous current suppression. This paper proposes an improved complex least mean square (CLMS) algorithm with error compensation to effectively mitigate rotor unbalanced vibration. Firstly, a dynamic model of the AMB-rotor system with an unbalanced mass is established, and the displacement amplitude inconsistency within the orthogonal channels of the radial magnetic bearings is analyzed. Subsequently, the rotor displacement signal from the orthogonal channels is converted into a complex plane signal. By calculating the negative sequence weight component, the displacement signal is reconstructed, and an error compensation channel based on the CLMS is introduced to enable real-time tracking and compensation of displacement amplitude inconsistencies in the orthogonal channels. Moreover, system stability across the full speed range is ensured through the application of the phase compensation angle method. Finally, experimental validation on a magnetic levitation molecular pump prototype confirms the effectiveness of the proposed algorithm.

Identification in a Magnetically Levitated Rigid Rotor System Integrated with Misaligned Sensors and Active Magnetic Bearings

Identification in a Magnetically Levitated Rigid Rotor System Integrated with Misaligned Sensors and Active Magnetic Bearings

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.

Integrated analysis of additive and multiplicative internal excitation parameters in misaligned-bowed-internally damped rotor systems with active magnetic bearings: Numerical and experimental identification

Precisely identifying internal excitation parameters within rotor-bearing systems is imperative for ensuring reliability and optimal performance. This paper meticulously addresses various issues, such as coupling misalignment, residual bow, internal damping, and imbalance. However, the novelty of the work lies in its detailed exploration of the interplay between these parameters, particularly emphasizing the multiplicative effect resulting from residual bow and misalignment. Introducing an innovative approach, the paper employs an active magnetic bearing (AMB) near the output rotor's disc to mitigate vibrations and enhance system stability. A robust identification algorithm is developed, leveraging least-squares fitting in the frequency domain to accurately estimate multiple internal excitation parameters and system characteristics. These parameters encompass viscous damping, internal damping, unbalance, residual bow, static and dynamic coupling misalignment, multiplicative force, and various AMB constants. The algorithm's resilience is demonstrated through rigorous testing against noise percentage errors. Furthermore, practical experimentation using a laboratory test rig validates its efficacy. Response data from proximity probes are inputted into the algorithm, successfully identifying parameters. Experimental validation is achieved by comparing irregularities in orbit plots and full spectra with numerical simulations based on the identified parameters, affirming the algorithm's reliability in real-world scenarios. This comprehensive approach offers a dependable solution for internal excitation identification in complex rotor systems.

Radial Displacement Measurement Method for Magnetic Bearing Based on FPC Coils

Radial Displacement Measurement Method for Magnetic Bearing Based on FPC Coils

Opportunities to Enhance sCO2 Power Cycle Turbomachinery with Bearingless Motor/Generators

Thermal power cycles using sCO2 as a working fluid place extreme demands on their turbomachinery components and their electric motors/generators. In this paper, new system topologies for sCO2 turbomachinery are proposed which take advantage of “bearingless” electric machine technology to improve performance. Bearingless motors/generators are a new type of electric machine which integrate the functionality of active magnetic bearings into the existing hardware of an electric motor/generator. The existing electromagnetic surfaces and materials are reused to enable controllable production of radial forces on the machine shaft. This is envisioned to improve hermetic direct-drive turbomachinery systems by either augmenting existing bearings (i.e., bearing assist) or replacing existing bearings (i.e., bearing removal). The state-of-the-art technologies for several bearing types (gas foil bearings, externally pressurized porous (EPP) gas bearings, and active magnetic bearings) and electric machines are reviewed to motivate the introduction of bearingless technology. Two system designs using bearingless machines are proposed and compared against existing commercial solutions in terms of maximum shaft weight, number of passthroughs into the hermetic environment, cost, and complexity. A case-study bearingless motor/generator is assessed via simulations and a hardware prototype to investigate practical considerations for using bearingless technology in sCO2 turbomachinery. The proposed bearingless solutions have potential to enable a new generation of sCO2 turbomachinery with improved reliability, reduced complexity, and lower cost. This paper shows that by transforming the motor/generator already present in turbomachinery into a bearingless motor/generator, the technical challenges involved with sCO2 can be overcome without adding significant cost.

Robust Controller Development via Iterative Model Updating for Active Magnetic Bearing Rotor Systems

Robust Controller Development via Iterative Model Updating for Active Magnetic Bearing Rotor Systems

A recurrent neural network‐based rotor displacement estimation method for eight‐pole active magnetic bearing

AbstractActive magnetic bearing (AMB) is a key technology in high‐speed rotating machines for rotor suspension, where the displacement sensors play a crucial role in detecting and controlling the rotor position. However, the traditional displacement sensors have the problems of high cost, large volume and poor reliability. To solve these problems, this paper proposes an innovative solution that utilises a recurrent neural network (RNN) to estimate the rotor displacement from the current in the AMB controller. The proposed method offers high‐quality prediction performance for the rotor displacement which is close to the high precision eddy current displacement sensors. The mathematical model of AMB is analysed to provide guidance in historical current data acquisition and design of RNN. The input dimensions and the architecture of the neural network are optimised to improve both prediction accuracy and computational complexity. Experimental results validate the effectiveness of the algorithm and demonstrate that the proposed method has high accuracy, robustness and generalisation ability.

Proportional-derivative control and motion stability analysis of a 16-pole legs rotor-active magnetic bearings system

This paper analyzes the motion stability of a 16-pole rotor-active magnetic bearings (rotor-AMB) system and investigates the complex vibrations under a proportional-derivative (PD) controller. First, electromagnetic theory and Newton’s second law are applied to derive the two-degree-of-freedom differential governing equations for the 16-pole rotor-AMB system, incorporating the PD control terms. The resulting differential equations include parametrically excited, quadratic nonlinear, and cubic nonlinear terms. Subsequently, the multiple time scales perturbation analysis method is performed on the obtained governing equations, yielding four-dimensional averaged equations in both Cartesian and polar coordinates. Finally, numerical simulations including the amplitude–frequency response characteristics, motion trajectories, energy–amplitude relationships, as well as bifurcation and chaotic motion of the system are studied. The results indicate that the PD controller affects the softening and hardening spring characteristics of the system and has significant control effects on the system’s amplitude, energy, and stability. Additionally, increasing the differential gain coefficient [Formula: see text] can change the system’s motion from chaotic to periodic.

Comparison of Levitation Properties between Bulk High-Temperature Superconductor Blocks and High-Temperature Superconductor Tape Stacks Prepared from Commercial Coated Conductors.

Bulk high-temperature superconductors (HTSs) such as REBa2Cu3O7-x (REBCO, RE = Y, Gd) are commonly used in rotationally symmetric superconducting magnetic bearings. However, such bulks have several disadvantages such as brittleness, limited availability and high costs due to the time-consuming and energy-intensive fabrication process. Alternatively, tape stacks of HTS-coated conductors might be used for these devices promising an improved bearing efficiency due to a simplification of manufacturing processes for the required shapes, higher mechanical strength, improved thermal performance, higher availability and therefore potentially reduced costs. Hence, tape stacks with a base area of (12 × 12) mm2 and a height of up to 12 mm were prepared and compared to commercial bulks of the same size. The trapped field measurements at 77 K showed slightly higher values for the tape stacks if compared to bulks with the same size. Afterwards, the maximum levitation forces in zero field (ZFC) and field cooling (FC) modes were measured while approaching a permanent magnet, which allows the stiffness in the vertical and lateral directions to be determined. Similar levitation forces were measured in the vertical direction for bulk samples and tape stacks in ZFC and FC modes, whereas the lateral forces were almost zero for stacks with the REBCO films parallel to the magnet. A 90° rotation of the tape stacks with respect to the magnet results in the opposite behavior, i.e., a high lateral but negligible vertical stiffness. This anisotropy originates from the arrangement of decoupled superconducting layers in the tape stacks. Therefore, a combination of stacks with vertical and lateral alignment is required for stable levitation in a bearing.

Analysis of factors influencing the performance of radial electrodynamic bearing with radial air gap between permanent magnets using response surface methodology

Analysis of factors influencing the performance of radial electrodynamic bearing with radial air gap between permanent magnets using response surface methodology

High-speed magnetically levitated centrifugal hydrogen recirculation pump in proton exchange membrane fuel cells

This paper presents a novel magnetically levitated centrifugal hydrogen recirculation pump (MLCHRP) designed for proton exchange membrane fuel cells (PEMFCs). Compared to traditional hydrogen recirculation pump, the MLCHRP offers significant advantages, including no lubrication, no mechanical friction, and active vibration suppression. However, the compact design of the pump imposes constraints on the load capacity of the active magnetic bearings (AMBs). As a result, the rotor is more susceptible to instability when subjected to unbalanced disturbance forces. This paper details the structure of the MLCHRP and provides an analysis of the basic model for unbalanced disturbance forces. A method for suppressing these unbalanced disturbances is proposed, utilizing a Linear Extended State Observer (LESO) combined with Parallel Peak Filters (PPF). The impact of this approach on system stability is thoroughly examined, and the effectiveness of the proposed method for unbalanced disturbance suppression is experimentally validated. The experimental results show that the peak-to-peak displacement of the rotor decreased by 80%. Additionally, the synchronous component in the rotor's displacement FFT was reduced by 6 dB (from -19.2 dB), and the second harmonic component decreased by 23.8 dB (from -23.7 dB). Finally, aerodynamic performance tests confirm that the MLCHRP meets the application requirements of actual PEMFCs system.

Dynamics and adaptive backstepping control of rotor-hybrid foil-magnetic bearings system

The hybrid foil-magnetic bearing (HFMB) is a contactless-type bearing composed of a foil bearing (FB) in the inner side and an active magnetic bearing (AMB) in the outer side. It has the advantages of low drag torque, high DN value (bearing inner diameter times rotating speed), and high supporting efficiency. However, significant subsynchronous vibration will degrade the stability of the rotor-HFMBs system, which is an obstacle to the industrial implementation of HFMBs. To control the rotor vibration, this paper presents a dynamic model of the rotor-HFMBs system with unknown parameters and the design of an adaptive backstepping controller (ABC) for it. The stability of the closed-loop system is established. Simulation results of the rotor-HFMBs system controlled by ABC are compared with the proportional-integral-derivative controller (PID), illustrating that the ABC is capable of eliminating rotor vibration, and it is more effective than the PID.

A Novel Three-Degree-of-Freedom Hybrid Magnetic Bearing for Air Compressors

A Novel Three-Degree-of-Freedom Hybrid Magnetic Bearing for Air Compressors