Magnetic Bearing Research Articles

Development of an experimental plant and a numerical model of an axial magnetic rotor suspension

This article presents the results of the work on the creation of an experimental plant, its testing, as well as the development of a computational model of a rotor magnetic suspension with the use of axial electromagnets. The main purpose of producing the plant was to test the results of the developed numerical finite element model. An automatic control system was developed for the experimental installation. The electrical circuit was assembled on the basis of a ESP32 microcontroller with a clock frequency of 240 MHz and a PWM with a capacity of 10 bits. A PID-regulator program was developed. The coefficients kP, kD, kI used in the code of the electronic control system program (PID-controller) were selected. An experimental study of the bearing capacity of the axial active magnetic bearing under the influence of an external axial force was conducted. The required power of the axial active magnetic bearing was determined. The maximum load-bearing capacity of the installation for the selected coefficients of the PID-controller was determined. An axisymmetric finite-element model of the axial active magnetic bearing was created in the open-source program FEMM 4.2. The load-bearing capacity of the installation for a given current intensity value was calculated. The results of the numerical modelling were compared with the experimental data obtained. The basic principles of creation and operation of the experimental plant and its numerical model are outlined.

A comprehensive comparison of the in vitro hemocompatibility of extracorporeal centrifugal blood pumps.

Purpose: Blood damage has been associated with patients under temporary continuous-flow mechanical circulatory support. To evaluate the side effects caused by transit blood pumping, in vitro hemocompatibility testing for blood damage in pumps is considered a necessary reference before clinical trials. Methods: The hemocompatibility of five extracorporeal centrifugal blood pumps was investigated comprehensively, including four commercial pumps (the Abbott CentriMag, the Terumo Capiox, the Medos DP3, and the Medtronic BPX-80) and a pump in development (the magAssist MoyoAssist®). In vitro, hemolysis was tested with heparinized porcine blood at nominal operating conditions (5L/min, 160mmHg) and extreme operating conditions (1L/min, 290mmHg) using a circulation flow loop. Hematology analyses concerning the blood cell counts and the degradation of high-molecular-weight von Willebrand factor (VWF) during 6-h circulation were also evaluated. Results: Comparing the in vitro hemocompatibility of blood pumps at different operations, the blood damage was significantly more severe at extreme operating conditions than that at nominal operating conditions. The performance of the five blood pumps was arranged in different orders at these two operating conditions. The results also demonstrated superior hemocompatibility of CentriMag and MoyoAssist® at two operating conditions, with overall low blood damage at hemolysis level, blood cell counts, and degradation of high-molecular-weight VWF. It suggested that magnetic bearings have an advantage in hemocompatibility compared to the mechanical bearing of blood pumps. Conclusion: Involving multiple operating conditions of blood pumps in in vitro hemocompatibility evaluation will be helpful for clinical application. In addition, the magnetically levitated centrifugal blood pump MoyoAssist® shows great potential in the future as it demonstrated good in vitro hemocompatibility.

Research on Electromagnetic System of Large Capacity Energy Storage Flywheel

A large capacity and high power flywheel energy storage system (FESS) is developed and applied to wind farms, focusing on the high efficiency design of the important electromagnetic components of the FESS, such as motor/generator, radial magnetic bearing (RMB) and axial magnetic bearing (AMB). Firstly, a axial flux permanent magnet synchronous machine (AFPMSM) based on soft magnetic composite material (SMC) is designed. Then, considering the structure of FESS and machine, a permanent magnet biased radial magnetic bearing (PMRMB) and a HALBACH axial passive magnetic bearing (PMB) is proposed which have the advantages of low power consumption and large bearing capacity, then the analyses are carried out according to the load capacity requirements. Finally, the flywheel prototype is fabricated and tested. The experimental results verify the relevant theoretical analysis, and finally can achieve stable and reliable operation.

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

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

Kriging-Based Surrogate Controller for Robust Control of a Flexible Rotor Supported by Active Magnetic Bearings

Abstract Vibration control in supercritical rotors is a challenging task due to the underlying complex dynamics that high-speed machinery undergoes. When taking into account both structural (e.g., structural integrity and material properties) and operational (e.g., rotational speed variation and environmental effects) uncertainties that can plague such systems, the task of designing and implementing a robust and reliable control system becomes increasingly daunting. In this contribution, a Kriging modeling approach is used to derive a representative surrogate-based controller applied to a flexible rotor supported by active magnetic bearings. The surrogate controller is formulated by considering the relationship between the shaft position and actuator current. This means that after proper training, the surrogate control takes the rotor position (proximity sensor readings) as input, and the output corresponds to the current levels for the actuators to control the system vibration amplitudes. Experimental tests considering a test rig composed of a flexible rotor supported by two active magnetic bearings were used to validate the proposed approach for different operational scenarios, namely, steady-state, run-up, and transient-state. In this case, the surrogate model was trained considering the shaft positions and the corresponding control currents measured with the rotor operating close to its first bending critical speed. The obtained results illustrate how the Kriging-based surrogate controller can reliably maintain acceptable vibration levels, even when exposed to unexpected constant rotation speeds and other operating conditions not manifested in previous sample sets.

Design of a Noncontact Torsion Testing Device Using Magnetic Levitation Mechanism

To facilitate torsion testing in special environments, a noncontact torsion testing device, where a noncontact torque can be transmitted to a specimen, was developed using magnetic levitation technology. A permanent magnetic gear is used to produce noncontact torque. In addition, four electromagnets and four attractive-type permanent magnetic bearings were employed to realize levitation; in more detail, the four electromagnets actively stabilized two levitation degrees of freedom (DoFs), while the four attractive-type permanent magnetic bearings passively stabilized four DoFs. Furthermore, a plant model considering the effect caused by the four attractive-type permanent magnetic bearings was built for the two levitation DoFs requiring active control. Based on the plant model, two PD-controllers were designed. Moreover, a control simulation was conducted to obtain appropriate PD-gains. Finally, experiments further validated the feasibility of the whole scheme, and it was proven that the device can apply a 0.126 N·m torque to the specimen while maintaining levitation.

A Full-Frequency Angular Rate Measurement Method of Spacecraft Based on Multi-MSCSG Weight Assignment

In order to realize the full-frequency angular rate measurement of spacecraft based on Magnetically Suspended Control and Sensing Gyroscope (MSCSG), a full-frequency angular rate measurement method of spacecraft based on multi-MSCSG weight assignment is proposed in this paper. Firstly, the main structure of MSCSG is introduced. The traditional angular rate sensing principle of MSCSG is analyzed on the basis of the working principle of Lorentz magnetic bearing, the key component of MSCSG; After introducing and analyzing the shortcomings of the two existing measurement methods, namely, four-cross configuration and virtual gyro technology, the weight function of frequency is obtained by deriving the measurement accuracy model of the two methods. The weight assignment measurement method is proposed to achieve the fusion of the advantages of the two methods and achieve high-precision angular rate measurement of spacecraft in the full- frequency band. Through simulation and semi physical experiments, we verified that the angular rate accuracy of spacecraft measured by the proposed one can be maintained above 98% at different frequencies, and the higher the frequency is, the higher the angular rate measurement accuracy of spacecraft is.

Unbalanced Magnetic Pull Disturbance Compensation of Magnetic Bearing Systems in MSCCs

Unbalanced magnetic pull (UMP) disturbance seriously affects the stable operation of the magnetically suspended rotor (MSR) system. This article proposes an UMP disturbance suppression method based on a linear extended state observer (LESO) and adaptive peak filter (APF). The cascade structure of LESO and APF can accurately estimate the UMP disturbance in the whole speed range. First, the dynamic model of the active magnetic bearing rotor systems is established and the UMP caused by the dynamic eccentricity in the MSR system is analyzed. Second, a third-order LESO and an APF are designed. The performance evaluation of the LESO indicates that estimation error of disturbance decreases with the increase of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\omega _{o}$</tex-math></inline-formula> , and the addition of APF can make UMP disturbance estimation unaffected by the high-frequency noise. After adding this method, the closed-loop system remains stable within the working rotation speed range. Finally, simulation results show that the UMP disturbance can be estimated and compensated. Experimental results validate the proposed method can well suppress the large vibration of the UMP on the rotor.

AMB-Supported Flywheel Battery for Electric Tractors: Structure Design and Driving Method

Active magnetic bearing (AMB) supported flywheel energy system, also called flywheel battery, is a mechanical battery storing kinetic energy in a rotating flywheel disk and has appealing features such as high specific power and energy, short time of charging/discharging, no pollution and long life span. In this paper, we apply AMB-supported flywheel battery as a new type of power battery to electric tractors, which absorbs wasted energy when the electric tractor brakes frequently and provide additional driving energy supplement when the electric tractor face an overload start, a sudden load mutations or field work resistance mutations. The structure design of the AMB-supported flywheel battery is introduced, including the axial/radial magnetic bearing, flywheel disk, the rotor and the motor. The driving method of the whole system is also analyzed. This design provides the reliability guarantee for the innovative application of the AMB-supported energy storage flywheel battery in electric tractors.

Control Study for Compensating Rotor Vibration of Four-DOF Six-Pole Hybrid Magnetic Bearings Based on Variable Step Size LMS Algorithm

In order to solve the problem that the unbalance vibration caused by rotor mass eccentricity of the four-degree-of-freedom (four-DOF) six-pole hybrid magnetic bearings (HMBs), a feed-forward compensation control strategy based on variable step size least-mean-square (LMS) adaptive filter is proposed. First, the structure, operation principle and mathematical model of the four-DOF six-pole HMBs are introduced, the motion law of rotor vibration is analyzed, and the dynamic equation is derived. Second, the variable step size LMS adaptive filter is improved by using the Versoria function. The step size of LMS algorithm is adjusted adaptively by using Versoria function model and Takagi–Sugeno (TS) fuzzy inference machine. The LMS adaptive filter can generate a signal with the same frequency, amplitude, and phase as the rotating speed to offset the vibration signal, so as to realize the vibration compensation control of the four-DOF six-pole HMB rotor. Finally, the simulations and experiments not only prove the effectiveness of this method but also show that the method has good compensation accuracy. The result shows that the Versoria function used in variable step size LMS adaptive filter for vibration compensation is better than the traditional variable step size filtering algorithm based on Sigmoid function.

Research on Common Mode EMI and Its Reduction for Active Magnetic Bearings

Active magnetic bearing (AMB) with power electronics drive is an important technology for high-speed rotational machinery suspension. There were seldom literatures concerning the common mode (CM) electromagnetic interference (EMI) problems of the AMB system. In this article, we found that the power electronic converter used for AMB control will not only bring EMI to the devices but also influence the performance of the levitation control. To cope with this problem, the parasitic paths of the leakage currents in the five-degrees-of-freedom AMB system were analyzed. The control principle and the novel zero CM PWM (ZCMPWM) strategy for the AMB driven by a four-leg converter were presented to suppress the CM EMI. Experiment has been done on an AMB-based compressor. The proposed method can significantly reduce the CM EMI caused by the AMB controller and improve the performance of levitation.

Tilting Control of Rotor Suspended by Complex Magnetic Bearings with Coupling Torques

For a novel Vernier-gimballing magnetically suspended flywheel (Vernier-gimballing MSFW) with conical magnetic bearing (MB) and Lorentz MB, the rotor’s dynamic model is constructed based on the characteristics of both coupling torque generated by conical MB and nonlinear titling torques generated by Lorentz MB. To make the high-speeding rotor tilt precisely and fast to output large moment, the Vernier-gimballing control method based on the extended state observer (ESO) combined with feedback linearization is presented originally considering torques’ complex nonlinearities, and the sliding mode control (SMC) with ESO is designed to improve the robustness of the closed-loop system. Simulations and experimental tests to verify the rightness and validity of SMC with ESO have been done and all research results indicate that the rotor can track the tilting signal faster and more accurately than classic SMC to output high precision moment.

A Study on Weight Reduction and High Performance in Separated Magnetic Bearings

Recently, high-speed motors are receiving a lot of attention in the industrial field. When driving a motor at high speed, the advantages include high power density, high efficiency, and miniaturization. However, the disadvantages of the high-speed operation of motors are mechanical and structural safety. This is because the bearings used in high-speed motors require characteristics such as precision and low friction. There are two prominent types of bearings mainly used in high-speed motors: rolling bearings and magnetic bearings. A feature of rolling bearings is that they reduce frictional resistance by contacting points or lines between the shaft and the bearing. However, the disadvantages of rolling bearings are high mechanical friction losses due to the need for contact with the lubrication system. Maintenance costs are high. For this reason, a lot of research on bearings is being conducted to reduce the frictional loss of bearings and increase their efficiency and reliability. Bearings that are advantageous for high-speed operation are magnetic bearings that do not require lubricants, have no friction loss, and have low maintenance. However, magnetic bearings have disadvantages such as high cost and difficulty in miniaturization. In this paper, a stator with a separated teeth structure was used to compensate for these disadvantages. Using this, a model with miniaturization, light weight, and high manufacturability was proposed. The model name proposed in this study is called the STMB (separated teeth magnetic bearing). There are also disadvantages of the STMB model proposed in this paper. A model that compensates for this drawback is called the HSTMB (hybrid separated teeth magnetic bearing). The HSTMB reduces the weight by removing the back yoke of the stator and has advantages of a high filling rate and high productivity in the form of a module. As a result, high productivity, light weight, and high performance are possible when the HSTMB is applied, which was proven through FEA (finite element analysis).

Dynamic Characteristics Analysis of Magnetic Levitation Rotor Considering Unbalanced Magnetic Pull

The working principle of the motor can cause unbalanced magnetic pull (UMP) between stator and rotor unavoidably. Previous research about nonlinear vibration excited by UMP was focused on the rotor supported by traditional mechanical bearings or gas bearings. However, the magnetic levitation rotor is particular due to the low rigidity provided by the active magnetic bearing (AMB). UMP amplifies rotor vibration in the resonant zone and further excites the nonlinear electromagnetic force, thus producing different vibration phenomena. The paper calculates rotor orbit, spectra analysis, and time-history plot with numerical methods and studies the influence of the rotation speed, eccentricity, key control parameters, and UMP on rotor dynamics in detail. Results illustrate displacement response spectra of the magnetic levitation rotor are quite different from previous research results. The appearing frequency components are inducted by universal formulas in this paper. Furthermore, research shows a slight adjustment of the control parameters affect significantly harmonic components and vibration characteristics. The research results have practical reference significance for fault diagnosis, feature recognition, and controller optimization of the AMB-rotor system.

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.

A novel optimized fault prediction in magnetic bearing using shaft vibration image database

A novel optimized fault prediction in magnetic bearing using shaft vibration image database

Study on Load-Bearing Characteristics of Converter Trunnion Bearing

In order to improve the load-bearing performance of converter trunnion bearing, this paper proposes magnetic-hydraulic bearing which is a new coupled support technology that combines electromagnetic support and hydrostatic support. It can be realized the active control of electromagnetic and hydraulic pressure, and is conducive to extending the bearing replacement period. Based on the magnetic-hydraulic coupling, a mathematical model of the initial state of the radial support system is established, the calculation formula of bearing capacity of radial magnetic fluid bearing is deduced, and Matlab software is used to analyze the variation trend of bearing capacity and stiffness with rotor displacement. The optimization of structural parameters was carried out according to analysis of bearing characteristics, and it was concluded that the bearing performance was the best when the diameter of the bearing cavity was 10 mm, and the bearing capacity increased significantly when the thickness of the oil film was 70 μm. It provides a theoretical basis for the innovative design of converter trunnion support system.

Study on Modeling and Analysis Method of Active Magnetic Bearing–Flexible Support Coupled System

Study on Modeling and Analysis Method of Active Magnetic Bearing–Flexible Support Coupled System

Improvement of the Static and Dynamic Characteristics of Water-Lubricated Bearings With Integrated Halbach Magnet Arrays

The generation of frictional vibration and noise by water-lubricated bearings is one of the most severe problems putting at risk the safety and concealment of ships. Here, Halbach magnet arrays were integrated as the upper bush of the water-lubricated bearing with the aim of suppressing frictional vibration. Simulations and experiments were conducted and compared between the magnetic bearing and a normal rubber bearing. Effects of magnetic strength, Halbach array length, rotational speed, and external load on bearing characteristics were analyzed. The results show superior static and dynamic performances on the magnetic bearing. More specifically, attractive forces generated by Halbach magnets can reduce static pressure by nearly 37% on the bottom bush. Stiffness of magnetic bearings was calculated as smaller than for normal bearings, indicating a lower natural frequency. Shaft trajectories were observed close to the geometric center of bearing yielding less stress concentration on the bottom bush of the magnetic bearing. Finally, test rig experiments demonstrated suppressed vibrational peaks and reduced frictional vibration (more than 10 dB) on the magnetic bearing. It is also interesting to note that the magnetic bearing even shows exceptional robustness regarding fluctuations of rotating speed or external load. This study presents a new routine for overcoming the frictional vibration and noise of water-lubricated bearings.

Displacement Control and Simulation Based on A Hybrid Magnetic Bearing Model

The mechanical structure of a hybrid magnetic bearing contains both a permanent magnet and electromagnet, besides, its magnetic force form is relatively complex. The installation deviation of the sensor, processing quality, and other factors will make the actual working position of the magnetic bearing deviate from the rated balance position when it is stably suspended. This situation affects the working efficiency of magnetic bearings. This paper takes a magnetic levitation structure as the research object, and obtains the single-end magnetic force of the structure from electromagnetics-related knowledge. From the mechanical point of view, the detailed force formula of the system is obtained. The control system is designed by combining fuzzy control with PID control, and the performance of the two control methods is compared. In this paper, based on a hybrid magnetic bearing model, its mathematical model is obtained through electromagnetics and other related formulas, and PID and fuzzy PID algorithms are designed and simulated