Explore the vast range of titles available.

Bearings are pivotal components in mechanical systems, providing crucial support to rotating bodies. However, traditional bearings are susceptible to failure caused by friction and wear. This vulnerability is particularly pronounced in scenarios involving ultrahigh speeds and extreme conditions, necessitating the minimization of bearing losses and the enhancement of performance. Magnetic bearings, distinguished by their frictionless operation, absence of lubrication requirements, and high-speed capabilities, offer a promising solution to mitigate bearing failure attributable to friction. Nevertheless, a comprehensive review of magnetic bearings, encompassing their structural attributes, modeling mechanisms, and control strategies, is currently lacking in the literature. This paper aims to address this gap by conducting an exhaustive literature review on magnetic bearings. The objective is to provide scientists with a profound understanding of the structural characteristics, operational mechanisms, control performance, and future development trajectories of this technology. The paper begins by categorizing various magnetic bearings and conducting an in-depth analysis of their properties and characteristics, focusing on their magnetic circuit structures. Subsequently, it delves into the working principles and performance of mathematical models for magnetic bearings with different configurations, outlining the modeling procedures and optimization approaches. Additionally, the paper highlights the impact of control strategies on the performance of magnetic bearings. Modern control theory has demonstrated a remarkable 50% improvement in position accuracy and adjustment time compared to traditional PID control. Finally, the paper offers a glimpse into the future of magnetic bearing design, modeling mechanisms, and control strategies, presenting prospective directions for further advancements in this field.

The versatility of high-speed drives can be enhanced by incorporating a flexible coupling that isolates motor shaft and application dynamics, enabling a single motor to operate with a diverse range of applications. However, this isolation increases driveline flexibility, necessitating strength analysis for the flexible rotor assembly, during dropdown events in active magnetic bearing supported systems. It is also necessary to implement the nonlinear models of the bearing elements to acquire realistic dynamics of the system for stress estimation. To that end, this paper extends the traditional dropdown analysis by proposing a method to calculate stresses and fatigue life during dropdown and identify critical driveline components. The study employs a megawatt-class induction machine driveline coupled with a quill-shaft coupling as a test case. A finite element model, based on Timoshenko beam theory, is developed for the rotor system. A nonlinear contact model is implemented in touchdown bearings to obtain the friction forces during contact of rotor and bearings. The system is levitated using a designed controller and allowed to fall freely on touch down bearings due to gravity. Bending and shear stresses are estimated based on vibrational responses under different dynamic conditions. Stress intensity distribution highlights that the quill-shaft coupling experiences significantly higher stresses than other rotor locations. Furthermore, the coupling’s geometric dimensions significantly influence stress intensity, a critical factor in integrated driveline design.

Aiming at the high-precision torque output and saturation singularity avoidance problems in Lorentz force magnetic bearing (LFMB) swarms for magnetic levitation spacecraft, this study designs a manipulation law based on an adaptive weighted pseudo-inverse law. The system monitors each magnetic bearing’s working state in real time using high-precision position and current sensors. As the key input for the adaptive weighted pseudo-inverse control law, the sensor data’s measurement accuracy directly determines torque distribution effectiveness and attitude control precision. First, considering electromagnetic back-EMF effects, individual LFMB dynamics are modeled via the equivalent magnetic circuit method, with working principles elucidated. Subsequently, saturation coefficients for LFMB swarms are designed. Incorporating spacecraft maneuvering requirements, a genetic optimization algorithm establishes the optimal mounting configuration under task constraints. Considering the LFMB swarm configuration characteristics, this study proposes an adaptive weighted pseudo-inverse maneuvering law tailored to operational constraints. By designing an adaptive weighting matrix, the maneuvering law adjusts each LFMB’s torque output in real time, reducing residual saturation effects on attitude control speed and accuracy. Simulation results demonstrate that the proposed mounting configuration and adaptive weighted pseudo-inverse maneuvering law effectively mitigate saturation singularity’s impact on attitude control accuracy while reducing total energy consumption by 22%, validating the method’s effectiveness and superiority.

This study investigates the nonlinear vibrations of a parametrically excited active-magnetic-bearing (AMB) asymmetrical rotor system. A comprehensive mathematical model is developed for 8- and 16-pole AMBs functioning as actuators or supports, incorporating time-varying proportional-derivative (PD) controllers to characterize electromagnetic forces accurately. Using the variational approach and dimensionless parameters, partial differential equations of motion are derived and reduced to ordinary differential equations via the Galerkin method. The system exhibits complex dynamics, including primary, parametric, and combination resonances. The time-varying proportional controller enhances system controllability by exciting backward modes, significantly reducing vibration amplitudes in symmetrical and asymmetrical systems. This effect is amplified with an increased number of pole legs. Additionally, derivative gain impacts the system differently depending on support types: its influence is reduced in systems with journal bearings due to the combined effects of oil-film and magnetic forces, while systems with hinged-hinged supports display predominantly magnetic-driven behavior. The system demonstrates hardening behavior with journal bearings and softening behavior with simply-supported ends. Asymmetrical systems exhibit greater amplitude reductions than symmetrical ones, and system stability, bifurcation loci, and solution multiplicity are highly sensitive to variations in the air gap and coil current. Notably, the AMB actuator's position strongly affects peak vibration amplitudes, with the lowest peaks observed when the actuator is located at the shaft's midpoint. Shaft and disk eccentricities significantly influence nonlinear dynamics and bifurcation loci. Systems without shaft eccentricities exhibit lower vibration amplitudes and more stable solutions, with some approaching trivial responses. Analytical solutions derived via the multiple scales method, validated through numerical simulations, confirm that the time-varying controller effectively suppresses vibrations, highlighting its practical utility for vibration control in AMB-rotor systems.

A comparison of two developed simulation models for a hybrid magnetic bearing (HMB) transient states is presented. This applies to analyses using the flux-circuit directly coupled magnetic equivalent circuit and field-circuit indirectly coupled finite element analysis. The required control system was implemented for both models. The results obtained from the simulations were compared with those obtained from measurement tests.

Magnetic bearings are widely used in fields such as fluid machinery, aerospace, and marine vessels due to their properties of non-mechanical contact. Due to errors in manufacturing and assembly, unbalanced forces will be generated when the magnetic suspension rotors rotate, especially at high speed, which can easily cause strong vibration of the equipment. The control compensation algorithm of minimum displacement for the rotor is to adjust the control current of the magnetic bearing based on speed and unbalanced quantity, so that the rotor rotates around its centre of the geometric as much as possible, in order to reduce rotor displacement vibration and ensure the reliable and safe operation of the equipment. However, owing to the presence of speed changes and phase lag, it is necessary to continuously and repeatedly calculate the unbalanced compensation coefficient, which increases the computational complexity and affects the control effect of the magnetic suspension rotor. Therefore, this paper proposes a method based on LMS (Least Mean Square) and polynomial fitting to calculate the unbalanced compensation coefficient, obtaining the compensation amplitude and phase of the unbalanced vibration of the magnetic suspension rotor at different speeds, solving the problem of active unbalanced vibration control for the magnetic suspension rotor at any speed, and providing guarantee for the application of the magnetic suspension rotor in high-speed rotating machinery.

This study addresses the challenges of magnetic circuit coupling and control complexity in active radial magnetic bearings (ARMBs) by systematically investigating the electromagnetic performance of four magnetic pole configurations (NNSS, NSNS, NNNN, and SSSS). Initially, equivalent magnetic circuit modeling and finite element analysis (FEA) were employed to analyze the magnetic circuit coupling phenomena and their effects on the magnetic flux density distribution for each configuration. Subsequently, the air gap flux density and electromagnetic force were quantified under rotor eccentricity caused by unbalanced disturbances, and the dynamic performances of the ARMBs were evaluated for eccentricity along the x-axis and at 45°. Finally, experiments measured the electromagnetic forces acting on the rotor under the NNSS and NSNS configurations during eccentric conditions. The results indicate that the NNSS configuration significantly reduces magnetic circuit coupling, improves the uniformity of electromagnetic force distribution, and offers superior stability and control efficiency under asymmetric conditions. Experimental results deviated by less than 10% from the simulations, confirming the reliability and practicality of the proposed design. These findings provide valuable insights for optimizing ARMB pole configurations and promote their application in high-speed, high-precision industrial fields such as aerospace and power engineering.

Displacement self-sensing active magnetic bearings (AMBs) have garnered significant attention from both academia and industry for their potential to reduce cost, enable system integration, and enhance reliability. While numerous self-sensing methodologies have been researched, the field lacks a unified framework for discussing their theoretical foundation and practical applicability. This paper analyzes and summarizes various displacement self-sensing methods, deriving the underlying principles and essence of these techniques, and clarifying the intrinsic interconnections of different schemes. The process of self-sensing is constructed through two steps: online inductance estimation and electromagnetic inductance modeling. A novel framework is then proposed, categorizing online inductance estimation, with dedicated discussion on modeling and handling critical nonlinearity like magnetic saturation and the eddy current effect. Furthermore, this review conducts a systematic comparative analysis, evaluating prevalent schemes against key performance metrics such as robustness, stability, signal-to-noise ratio (SNR), and system complexity. Finally, persistent challenges and future research trends are discussed. This review provides a valuable reference for both researchers and engineers when selecting and implementing self-sensing technologies for AMB systems.

When a magnetic bearing is used in the design of a high-speed motor, no friction and wear occur because of the principle of magnetic levitation; however, the size of the entire system increases. An integrated magnetic bearing motor is a motor with a magnetic bearing inserted inside the rotor that can minimize the increase in the size of the entire system. In this study, a method to reduce the bearing force ripple and torque ripple of an integrated magnetic bearing motor through parameters for a Halbach array and permanent magnet tapering is proposed. When designing an integrated magnetic bearing motor, because the magnetic bearing is located inside the rotor, the influence of the magnetic flux of the rotor and stator on the magnetic flux of the magnetic bearing should be minimized. By combining the magnetic fluxes of the magnetic bearing, rotor, and stator at the rotor back yoke, magnetic saturation occurs, and the performance of the bearing force and torque ripples decreases. The bearing force and torque according to the Halbach array and permanent magnet tapering were analyzed using finite element analysis. The average bearing force and torque were maximized, and the ripple was minimized through the rotor parameters. Thus, the validity of the main design variables selected to improve the output characteristics was confirmed.

The installation distance between the speed sensor of the traditional rolling or sliding bearing permanent magnet synchronous motor and the rotor was very close, and the rotor of the magnetic levitation motor supported by Active Magnetic Bearings (AMBs) was in suspension. When the motor was running at high speed, the radial trajectory of the rotor changed all the time. The same frequency vibration caused by the unbalanced mass of the rotor made it easy to cause mechanical collision between the sensor and the rotor, resulting in direct damage of the sensor. Therefore, the sensorless speed estimation method was needed for the rotor control system of the magnetic levitation motor (MLM) to achieve high performance closed-loop control of speed and position. More importantly, in order to control or compensate the unbalanced force of the electromagnetic bearing rotor system, the rotor rotation speed signal should be obtained as accurately as possible. Therefore, the principle of adaptive sliding mode observer (SMO) was analyzed in detail by taking the rotor system of MLM as an example. Then, the sliding mode surface was designed, the speed estimation algorithm based on adaptive SMO was derived, and the stability analysis was completed. Finally, in order to verify the anti-disturbance performance of the system and the static and dynamic tracking performance of the motor, the dynamic performance was verified by increasing and decreasing the speed and load. The results showed that the speed estimation method based on adaptive SMO could achieve accurate speed estimation and had good static and dynamic performance.