Search Results (183)

In electrodynamic suspension (EDS) maglev systems, the time-varying magnetic fields experienced by onboard superconducting magnets can induce excessive AC losses and elevate the risk of quench, posing a critical threat to operational reliability. Conventional three-dimensional finite element analysis, though accurate, requires hours per frequency point and cannot support real-time quench assessment or parametric design optimization. This paper proposes an efficient magnetic shielding analysis method based on a reflection–absorption decoupled lumped-parameter framework. The three-dimensional eddy current field is reduced to a low-order coupled system by decomposing the eddy currents into plate-surface modes, a global circulation loop, and side-wall contributions, all coupled through a unified series magnetic circuit, while the field penetration through the cavity wall is captured via a finite impulse response (FIR) diffusion kernel with a high-frequency correction. The proposed method achieves a simulation time of 3–5 s per frequency point, a speedup of approximately ${10}^3$∼${10}^4$ over finite element analysis, with a root-mean-square shielding effectiveness deviation of 2.03 dB over 10 Hz–3000 Hz. The efficiency of the proposed method enables co-optimization of the outer dewar and superconducting magnets, offering a practical analysis tool for quench mitigation and electromagnetic compatibility design in EDS maglev systems. Full article

A novel energy-regenerative hydraulically interconnected ISD (inerter–spring–damper) suspension system (ER-HIISDS) is proposed by incorporating a fluid inerter into the hydraulic interconnection architecture, with the objective of simultaneously enhancing vehicle ride quality and vehicle stability while recovering suspension vibration energy. A coupled vehicle–hydraulic model is developed by integrating the 14-degree-of-freedom (DOF) full-vehicle dynamics with the ER-HIISDS hydraulic subsystem. On this basis, the key system parameters are optimized using the Electromagnetic Wave Propagation Algorithm (EMWPA). The mechanical characteristics and energy-regeneration performance of the optimized ER-HIISDS are subsequently investigated under sinusoidal excitations and stochastic road inputs. Comparative simulations are further conducted under representative transient maneuvers, including single-wheel bump excitation, emergency braking, and double-lane-change conditions, with a conventional passive suspension and an energy-regenerative hydraulically interconnected suspension (ER-HIS) employed as benchmark systems. The results indicate that the proposed ER-HIISDS can attenuate vehicle-body vibrations and improve body attitude stability while maintaining favorable dynamic performance and energy-regeneration capability over a range of stochastic road excitations. Under the representative transient maneuvers, the hydraulic interconnection generates additional coupling forces and corresponding anti-roll and anti-pitch moments, thereby effectively suppressing vehicle-body roll and pitch motions. Overall, the proposed ER-HIISDS achieves a favorable balance among ride comfort, handling stability, attitude control, and vibration-energy regeneration, demonstrating its potential for advanced vehicle suspension applications. Full article

Conventional five-degree-of-freedom (5-DOF) magnetic bearing supports often require a large axial span, while highly integrated magnetic circuits can introduce axial–radial flux coupling through shared return paths. This study proposes a compact permanent-magnet-biased 5-DOF magnetic bearing for flywheel energy storage systems, integrating two radial support sections and one axial support unit within a common stator. A series-opposed compensation winding is introduced to suppress axial-control-induced leakage into the radial branch. An electromagnetic design procedure considering leakage, ampere-turns, and magnetic-saturation constraints is evaluated using a three-dimensional magnetostatic finite-element model. At 6 A, the modeled axial and radial forces reach approximately 1.50 and 0.75 kN, respectively, while the maximum ferromagnetic flux density remains below 1.25 T. Under permanent-magnet-biased operation, the compensation winding reduces the peak radial-field deviation from approximately 161.5 to 1.7 mT, corresponding to approximately 99.0% suppression; the full-path RMS-deviation metric indicates approximately 93.1% suppression. Among the investigated configurations, the one with 50 turns provides the closest restoration to the bias-only radial field. Prototype tests demonstrate stable five-channel closed-loop static suspension, supporting physical realizability, but do not directly validate the predicted decoupling ratios. Full article

Maglev trains are susceptible to various types of operational challenges, including track irregularities, load variations, and actuator faults. It is evident that these factors can compromise suspension performance and even pose a serious risk to operational safety. This paper proposes a prescribed performance event-triggered fault-tolerant control method for the electromagnetic suspension system of a maglev train subject to multiple constraints. A projection-based adaptive extended state observer is designed to estimate the unknown gain caused by actuator faults and load variations, as well as the external disturbance. In light of the disparity in upper and lower safety margins inherent to the suspension gap error, arising from track irregularities, an asymmetric prescribed performance function and an error transformation are devised to ensure that the gap tracking error perpetually complies with the asymmetric prescribed performance constraint. In addressing the issue of rapid variations in the suspension gap, the vertical velocity is also constrained through the implementation of prescribed performance, resulting in a joint constraint framework that encompasses both the gap tracking error and the vertical motion. A dynamic event-triggered mechanism has been incorporated into the backstepping design with a view to reducing unnecessary control updates under limited communication resources, while Zeno behavior has been excluded from the closed-loop system. Within this framework, a dynamic gain adjustment mechanism with an explicitly bounded rate of variation is further developed to achieve smoother gain adaptation. The uniform ultimate boundedness of all closed-loop signals is demonstrated through Lyapunov stability analysis under the prescribed multiple constraints. The efficacy of the proposed method is demonstrated through comparative simulation results. Full article

A magnetic-levitation direct-drive oil-free scroll compressor (MLDD-OFSC) eliminates the anti-rotation mechanism to achieve oil-free operation. Still, its large-stroke planar motion introduces strong sensor–DOF coupling and air-gap-dependent stiffness variation that degrade fixed-gain PID performance. This paper proposes a control strategy integrating acceleration feedback linearization, gain-scheduled PID, and coordinate decoupling. An inverse electromagnetic force model is derived to compensate for the nonlinear force–air-gap relationship, linearizing the suspension dynamics. A phase-adaptive gain scheduling law is developed, where gains vary with trajectory phase via a cosine-based mapping. A homogeneous transformation matrix decouples raw sensor signals into independent X, Y, and yaw DOFs. Frequency-domain analysis at three air-gap positions confirms closed-loop stability. Simulations show that the proposed acceleration-linearized gain-scheduled PID (AL_GS_PID) outperforms traditional PID and fixed-gain AL_PID in tracking accuracy. Experiments demonstrate progressive improvement across four configurations—decentralized PID, decoupled PID, fixed-gain AL_PID, and AL_GS_PID—with the full scheme reducing peak errors to 0.043 mm in X and 0.04 mm in Y, corresponding to 74.7% and 33.3% reductions over decentralized PID. These results demonstrate that the proposed strategy effectively addresses coupling and stiffness variation in large-stroke maglev systems under no-load and light-load conditions. Full article

Background: Accurate thyroid volume measurement is essential for diagnosing and monitoring thyroid disorders and for determining radioiodine therapy dosage. The ellipsoid method applied to two-dimensional B-mode ultrasound (Bmode-2D-US) is the most prevalent clinical approach, yet it is known to suffer from high observer dependence and limited accuracy. Tracked three-dimensional ultrasound (3D-US) is a promising radiation-free alternative, but direct comparisons across modalities under controlled conditions remain scarce. Methods: A custom-built anthropomorphic multi-modality phantom was constructed containing six anatomically realistic thyroid lobe samples molded from segmented MRI data, with ground truth volumes verified by the suspension method and 3D surface scanning. Volume measurements were performed by six observers of varying experience using Bmode-2D-US, electromagnetically tracked 3D-US (EM-3D-US), inertial-measurement-unit-tracked 3D-US (IMU-3D-US), and optically tracked 3D-US (Opt-3D-US), as well as computed tomography (CT) and magnetic resonance imaging (MRI). Inter- and intraobserver variability were assessed using modified Bland–Altman analysis. Results: All three 3D-US methods reduced inter- and intraobserver variability compared to Bmode-2D-US, achieving variability comparable to CT and lower than MRI. Mean accuracy was similar across 3D-US, CT, and MRI. Bmode-2D-US showed strong observer dependence, with operator experience having the most pronounced effect on this method. Among tracked methods, EM-3D-US and Opt-3D-US were least sensitive to operator movement quality, while IMU-3D-US showed somewhat higher sensitivity. Conclusions: Tracked 3D-US is a promising radiation-free alternative to conventional Bmode-2D-US for thyroid volumetry, offering improved reproducibility and accuracy across operators of varying experience in this phantom-based evaluation. Full article

Vehicle energy-regenerative suspension can convert part of the vibration energy induced by road excitation into electrical energy. However, there are coupled performance conflicts among energy recovery, ride comfort, and suspension safety, and a fixed-weight LQR controller finds it difficult to maintain a reasonable performance compromise under different road conditions. To address this problem, this paper proposes an AWG-NN-LQR control method based on an Adaptive Weight Generation neural network. First, a quarter-car energy-regenerative suspension model, an electromagnetic actuator model, and a random road model are established, and the vertical vehicle responses and energy-regeneration characteristics under different road classes are analyzed. Second, vehicle speed, road roughness coefficient, and statistical features of vehicle responses are used as inputs. LQR weight labels are generated through offline closed-loop simulation and candidate-weight search, and the AWG-NN is trained to learn the nonlinear mapping relationship between road conditions and weight parameters. Finally, closed-loop comparative validation is conducted for the passive suspension, fixed-weight LQR, and AWG-NN-LQR under a typical class-C road condition. The results show that, compared with the fixed-weight LQR, AWG-NN-LQR reduces the RMS of body acceleration from $1.7041{\mathrm{m}/\mathrm{s}}^2$ to $1.6527{\mathrm{m}/\mathrm{s}}^2$, and reduces the RMS of suspension deflection from $0.00863\mathrm{m}$ to $0.00844\mathrm{m}$, while achieving an average regenerated power of $9.41\mathrm{W}$. The proposed method can improve the objective-bias problem of the fixed-weight LQR under a typical operating condition while maintaining a certain energy-regeneration capability, providing a feasible approach for multi-objective adaptive control of energy-regenerative suspension. Full article

Previous studies on maglev vehicle–bridge coupled systems have mostly described the bridge using classical boundary conditions, while the effects of general constrained boundaries and uncertain parameters have not been fully considered. In this study, an energy-based dynamic model of a maglev vehicle–bridge coupled system is established. The boundary constraints of the bridge are introduced through equivalent springs, so that complex boundary conditions can be represented in a unified form. The proposed model is verified by comparison with published results. On this basis, Monte Carlo simulations are carried out to investigate the effects of random suspension parameters and random control parameters on the dynamic responses of the system. Two simplified electromagnetic-force models are also considered, and Sobol sensitivity analysis is used to evaluate the contributions of different parameters to the vibration responses and vibration energy. The results indicate that the suspension and control parameters affect different response quantities in different ways. The two electromagnetic-force models also lead to different sensitivity results, especially when the vibration energy is used as the evaluation index. The proposed method provides a useful tool for analyzing the stochastic vibration mechanism and optimizing the parameters of maglev vehicle–bridge coupled systems under general constrained boundaries. Full article

To reveal the nonlinear instability mechanism by which the three-degree-of-freedom rotor system of a magnetic-liquid double suspension bearing transforms from stable suspension to periodic vibration, a nonlinear dynamic model considering electromagnetic suspension force, hydrostatic supporting force, rotor unbalance force, and liquid film resistance is established. The equilibrium point of the system is linearized, and the Hopf bifurcation boundary is determined using the Routh–Hurwitz criterion. Numerical simulations are then carried out to investigate the effects of the initial current i₀, supply flow rate q₀, and different initial disturbances on the displacement time histories, phase trajectories, and spatial phase trajectories of the rotor. The results show that, under the given system parameters, the Hopf bifurcation boundary is 0.61 A for the initial current and 9.62 × 10⁻⁵ m³/s for the supply flow rate. Current variation mainly affects electromagnetic stiffness and nonlinear electromagnetic force, whereas flow rate variation primarily changes the hydrostatic load capacity and oil film damping characteristics. Under different initial disturbances, the system may exhibit amplitude attenuation, recovery to stable suspension, or finite amplitude periodic vibration. Experimental results show good agreement with numerical simulations in terms of frequency spectra, displacement time histories, and phase trajectories, thereby verifying the effectiveness of the proposed three-degree-of-freedom dynamic model and Hopf bifurcation analysis method. The results can provide theoretical guidance for parameter matching, stability evaluation, and self-excited vibration suppression of magnetic-liquid double suspension bearings. Full article

This study experimentally investigates the mixed convection heat transfer performance of CuZnFe₂O₄–water-based magnetic nanofluids in a cylindrical minichannel under the influence of external magnetic fields. Nanofluids with three different volumetric concentrations (0.25%, 0.50%, and 0.75%) were synthesized and characterized in terms of thermophysical properties. The experiments were conducted within the Richardson number range of 0.1–10 to ensure mixed convection conditions, while magnetic field intensities of 220 G, 300 G, and 380 G were applied using custom-built electromagnets. Results show that suspending CuZnFe₂O₄ nanoparticles significantly enhances the heat transfer rate compared to pure water, mainly due to increased thermal conductivity and particle–fluid interactions. The application of a magnetic field further augments the Nusselt number by disturbing the thermal boundary layer and intensifying particle motion, leading to up to 64.4% improvement compared with pure water at similar Reynolds numbers. In addition, Analysis of Variance (ANOVA) and Response Surface Methodology (RSM) were employed to determine the most influential parameters on heat transfer performance and to develop a predictive correlation for the Nusselt number as a function of Reynolds number, nanoparticle concentration, and magnetic field intensity. The findings highlight the combined effects of nanoparticle suspension and magnetic field application as a promising approach for enhancing heat transfer in low-flow mixed convection regimes, offering valuable insights for thermal management in miniaturized cooling systems. Full article

This paper presents the design and experimental validation of a self-contained rotating Halbach array—based demonstrator for electrodynamic suspension (EDS) systems. The proposed platform was developed to bridge the gap between conventional externally powered laboratory testbeds and large-scale EDS vehicles by enabling investigation of levitation behavior under realistic onboard mass and subsystem integration constraints. The system integrates rotating circular Halbach arrays, onboard power supply, sensing, motor control, and structural support within a single levitated architecture. Experimental validation was conducted under a constrained one-degree-of-freedom configuration allowing vertical motion only. The system achieved stable levitation of a 35 kg platform and supported additional payloads approaching a 1:2 ratio relative to the baseline mass, while maintaining air-gap stability within approximately ±0.1 mm. The experimental results further reveal that the operational limit of the system is governed by actuation power and current constraints rather than electromagnetic levitation capability, highlighting a key distinction between self-contained and externally powered EDS systems. The proposed demonstrator provides a compact and practical experimental platform for the validation and performance evaluation of Halbach-array-based EDS systems. In addition, the study presents practical engineering insights regarding payload distribution, actuator saturation, structural integration, and system-level design constraints relevant to future self-contained EDS platforms and control-oriented levitation systems. Full article

The suspension system of high-speed maglev trains has composite time-delay factors, such as inductance delay and control circuit latency, which lead to a decrease in the tracking and robustness of the current control loop. Based on the study of electromagnetic characteristics of suspension systems, this paper proposes a composite anti-time-delay current loop based on adaptive parameter optimization. First, a finite element analysis model of the suspension electromagnet is constructed to analyze the changes in suspension force and inductance of the suspension electromagnet. A self-tuning PI current loop is constructed to achieve time-varying parameter matching. Second, to tackle the inherent time delays and disturbances in the control loop, a predictive PI control algorithm combined with an extended state observer (ESO) is introduced, which effectively estimates and compensates for disturbances and phase lags. Furthermore, a parameter optimization strategy based on the adaptive differential evolution (ADE) algorithm is proposed to address the difficulties in current loop tuning. The results demonstrate that compared to traditional current loop strategies, the dynamic performance of the designed composite anti-time-delay current loop is significantly improved, enhancing the current following control capability of the suspension system under complex operating conditions. Full article

Graphene possesses exceptional mechanical strength, high electrical conductivity, and a stable lattice structure, making it an ideal material for sensors in advanced manufacturing. However, these sensors face stability challenges due to complex electromagnetic interference (EMI) environments generated by electrical equipment. Therefore, investigating the influence of EMI on sensor performance is of significant importance. In this study, simulations were performed to analyze electrical parameter perturbations of intrinsic graphene films under EMI conditions. The Magnetic Fields, Solid Mechanics, and Electrostatics modules in COMSOL Multiphysics were employed to construct a coupled model of a three-phase power transformer and a graphene-based pressure sensor. The results indicate that EMI can induce baseline drift on the order of ~5% full scale (FS) in the graphene current density, accompanied by degradation in signal-to-noise ratio (SNR) exceeding ~15 dB under typical simulation conditions. Graphene in direct contact with metal electrodes shows enhanced sensitivity to EMI, with more pronounced noise amplification due to interfacial coupling effects. In contrast, cavity-suspended graphene configurations exhibit relatively improved robustness, suggesting that suspended membrane architectures can mitigate EMI by reducing parasitic coupling and enhancing mechanical isolation. Compared with previous studies, this work highlights the role of multiphysics coupling and membrane suspension in influencing EMI-induced perturbations, providing theoretical guidance for the design of graphene-based sensors in power system and industrial Internet of Things (IoT) applications. Full article

The dynamic performance of medium- and low-speed maglev vehicle–track coupling systems, as well as the dynamic response of the vehicle body and suspension frame under suspension electromagnet failure, is of great significance for the safe operation of maglev tracks. Based on vehicle–track coupling dynamics theory, and considering the spatial dynamic magnetic rail relationship in combination with the suspension control system, a dynamic vehicle–track model incorporating suspension electromagnet failure is established. The effect of such failures on electromagnet suspension force and overall vehicle performance are analyzed. The results indicate that the theoretically calculated electromagnetic force differs significantly from the actual force. Under four electromagnet operating conditions, lateral displacement has the greatest influence on suspension force. By considering the magnetic saturation of ferromagnetic materials and the leakage effect of suspension gaps, a spatial dynamic magnetic orbit relationship is established. A single-pole suspension electromagnet fault has little effect on overall vehicle performance. When the suspension electromagnet on one side fails, the suspension frame tilts toward that side and is supported and operated by a sled. When three suspension points fail, the entire suspension frame loses its suspension state and operates fully under sled support. When a suspension frame electromagnet becomes stuck, severe fluctuations in suspension force and vehicle vibration acceleration occur. These fluctuations increase with vehicle operating speed, seriously endangering operational performance. The findings provide a fundamental theoretical basis for the safe operation and maintenance of medium- and low-speed maglev vehicles under fault conditions. Full article

Active suspension systems are gaining growing attention in the automotive industry. This trend aligns with vehicle electrification and X-by-wire technologies adoption, also answering to the increasingly stringent requirements for passenger comfort and safety. Among the possible solutions, electromechanical actuators represent a valid alternative to traditional shock absorbers, integrating an electric machine that can be easily controlled to deliver the desired forces in both active and passive operations. The present work aims at developing an innovative transmission compound for a rotary electromagnetic active suspension system that is able to obtain high level NVH and safety performances. Two different proposed systems are analyzed. The first one couples a cycloidal transmission stage to a polymeric planetary one, while the second one couples the same cycloidal stage to a concentric magnetic gearbox. Both of them are expected to improve the NVH performances of the shock absorber, thanks to the high efficiency of the cycloidal reducer and to the properties of plastic materials and of magnetic coupling. The proposed systems are analyzed analytically and in simulation environment, providing promising results in terms of efficiency and torque density. Full article