Modulation of magnetic moment and magnetic anisotropy of rare-earth-free permanent magnet α”-Fe16N2 under biaxial mechanical strain

Permanent magnets containing rare earth elements are essential components for the electrification of society. Ce(Co 1-x Cu x ) 5 permanent magnets are a model system known for their substantial coercivity, yet the underlying mechanism remains unclear. Here, we investigate Ce(Co 0.8 Cu 0.2 ) 5.4 magnets with a coercivity of ∼1 T. Using transmission electron microscopy (TEM) and atom probe tomography (APT), we identify a nanoscale cellular structure formed by spinodal decomposition. Cu-poor cylindrical cells (∼5-10 nm in diameter, ∼20 nm long) have a disordered CeCo 5 -type structure and a composition Ce(Co 0.9 Cu 0.1 ) 5.3 . Cu-rich cell boundaries are ∼ 5 nm thick and exhibit a modified CeCo 5 structure, with Cu ordered on the Co sites and a composition Ce(Co 0.7 Cu 0.3 ) 5.0 . Micromagnetic simulations demonstrate that the intrinsic Cu concentration gradients up to 12 at.% Cu/nm lead to a spatial variation in magnetocrystalline anisotropy and domain wall energy, resulting in effective pinning and high coercivity. Compared to Sm 2 Co 17 -type magnets, Ce(Co 0.8 Cu 0.2 ) 5.4 displays a finer-scale variation of conventional pinning with lower structural and chemical contrast in its underlying nanostructure. The identification of nanoscale chemical segregation in nearly single-phase Ce(Co 0.8 Cu 0.2 ) 5.4 magnets provides a microstructural basis for the long-standing phenomenon of "giant intrinsic magnetic hardness" in systems such as SmCo 5-x M x , highlighting avenues for designing rare-earth-lean permanent magnets via controlled nanoscale segregation.

A general controller-based dynamic linearized model-free adaptive control and its application to PMLSM.

Vibration reduction design of repulsive ring permanent magnet coupling in ship power transmission system

Design and performance of a lightweight, high power density permanent magnet Hall thruster

Research on water-cooling heat dissipation of modular stator built-in waterway permanent magnet synchronous motor

A pareto-based multi-physics coupling optimization method for electromagnetic noise in super high-speed permanent magnet synchronous motors

Practical development of terahertz technology requires higher power radiation sources. The sheet electron beam vacuum device is an effective solution of increasing the output power of terahertz radiation sources, but faces the difficulty of stable transmission of the beam. In this paper, a compact quadrupole permanent magnet (QPM) focusing system for terahertz sheet beam devices is designed, and a practical focusing system is constructed into a prototype for beam transmission verification. In the experiment, 16 pieces of high-performance NdFeB permanent magnets were adopted with a total weight of about 10 kg. The magnetic field test of the system was carried out and the results show that the system can provide a uniform high-intensity magnetic field of over 0.95 T within an axial length of 20 mm. With the tested QPM magnetic field configuration, PIC simulation of the sheet beam transmission was implemented, indicating that a sheet electron beam with a 20 kV voltage and 15 mA current can travel through a beam tunnel of a cross-section 0.1 mm × 0.05 mm, with a transmission ratio of 98.5%.

This paper investigates the feasibility of an interior permanent magnet (IPM) rotor for 1 MW-class high-speed permanent magnet synchronous machines (PMSMs) in a hybrid propulsion system of electrified aviation. A double-layer IPM machine and a surface-mounted PM (SPM) benchmark machine with Halbach-array PMs, which are typically employed in aviation applications; are designed using the same design specifications, the same stator, double-three-phase winding layout, physical air-gap length, outer and inner diameters of rotor; and the same materials. The rotor robustness of the IPM machine using high-strength iron material has been verified through mechanical strength analysis with an outstanding safety factor margin. The electromagnetic performances of IPM and SPM benchmark machines are compared. It is found that the IPM design can achieve similar high torque/power density and high efficiency to the SPM benchmark machine, using 48% less rare-earth PM materials and a simpler rotor structure without a carbon fiber sleeve for easy manufacturing. The investigation confirms the feasibility of IPM topology for MW-class high-speed aviation propulsion machines for lower cost and more sustainable purposes.

This paper presents a unified framework for reliable motion control of permanent magnet linear motors (PMLMs) by integrating fault detection (FD) and fault-tolerant control (FTC). The framework combines a brain emotional learning-based intelligent controller (BELBIC) with a linear extended state observer (LESO) to enable rapid detection and mitigation of abrupt and incipient faults, as well as disturbances and sensor noise that degrade tracking accuracy and system reliability. The LESO is employed to estimate unknown dynamics and lumped disturbances and to generate residuals for reliable fault detection, while BELBIC provides adaptive and robust control actions without requiring prior knowledge of system parameters or explicit fault models. Extensive simulation studies under actuator faults, system dynamics faults, external disturbances, and measurement noise are conducted. Comparative evaluations with benchmark approaches demonstrate improved fault detection speed, tracking accuracy, and robustness of the proposed framework, highlighting its potential for enhancing reliability and operational continuity in high-precision industrial applications.

Gastric cancer remains a global health challenge with high mortality rates, underscoring the urgent need for advanced diagnostic tools. While conventional gastroscopy encounters patient reluctance due to procedural discomfort, wireless capsule endoscopy (WCE) provides a non-invasive alternative but faces challenges, including intricate motion control, constrained power supply, and restricted detection capability. This study presents a bimodal imaging WCE system that integrates near-infrared fluorescence and white-light imaging, enhanced with linear magnetic navigation and motion-robust wireless power transfer. The innovative geometrically polarized permanent magnet configuration enables sensorless adaptive and precise linear navigation (position accuracy: 0.29 mm; orientation accuracy: 0.97°). The axially self-aligning coil configuration achieves motion-robust power transfer, with capacity further enhanced by a novel internal magnet layout. Experimental validation demonstrates stable high-power reception (2 W), reduced operator dependency through the linear navigation, and improved lesion detection capability via bimodal imaging. This breakthrough addresses the fundamental limitations of current WCE systems, showcasing a mechatronic approach to advance gastric cancer diagnostics.

Abstract The integration of linear motor and maglev technology enables contactless vehicle operation, laying the foundation for the speedup of rail transit. The high-temperature superconducting pinning (HTSP) maglev system is a passive levitation system, and its high-speed operation imposes explicit performance requirements on the traction system: a relatively large thrust to ensure high-speed traction capacity, a low normal force to avoid additional loads on the passive levitation system, and low thrust ripple to guarantee stable system operation. The ironless permanent magnet synchronous linear motor (PMSLM) meets all these demands, making it an ideal traction solution for HTSP high-speed maglev engineering. Focusing on the engineering application of HTSP maglev transportation, this paper takes the world’s first HTSP high-speed maglev engineering prototype’s ironless PMSLM as the research object, and investigates its electromagnetic characteristics based on actual prototype parameters. A finite element method (FEM) model is established to calculate the air-gap magnetic field and electromagnetic force, and a prototype test platform is built for experimental verification. Simulation and experimental results are in good agreement, verifying that the finite element model is reliable and accurate, and that the motor performance satisfies the system design requirements. Based on the validated model, the variation laws of electromagnetic parameters and the effects of key factors on electromagnetic force are clarified. The research results provide support for the collaborative design of traction-levitation-track systems and further promote the engineering application of HTSP maglev technology.

With the development of the automotive industry and road conditions, cars have become essential for daily life and travel. However, the number of traffic accidents is rising rapidly, and rear - end collisions are common, posing a threat to safety. Anti - collision technology is crucial for road traffic, but existing ones can't reduce losses or prevent accidents. This paper focuses on non-contact anti-collision technology based on electromagnetic repulsion and levitation, using relevant conversion technology. Permanent magnet devices like electromagnetic coils are placed around the vehicle. When a collision is about to happen, the magnetic levitation mode is activated; when a collision occurs, emergency levitation braking is triggered to reduce losses and achieve levitation or repulsion. By analyzing previous collision problems, a vehicle-road cooperative collision avoidance method is proposed in combination with the active collision avoidance system. Simulation designs of rear - end collision, active collision avoidance, and magnetic levitation are completed using MATLAB.It's concluded that this technology has high future development value.

Temperature characteristics of permanent magnet eddy current brake under overwinding protection

Ferrites constitue an important class of ferrimagnétique oxide materials which have been extensively investigated due to their interesting magnetic and electrical properties and wide range of technological applications. Among the different types of ferrites, hexagonal ferrites, particularly M-type magnetoplumbites such as BaFe₁₂O₁₉ and SrFe₁₂O₁₉, are of considerable importance because of their high magnetocrystalline anisotropy, large coercive force, moderate saturation magnetization and good chemical stability. In the present review, the crystal structures of spinel, garnet and hexagonal ferrites are discussed with emphasis on the S, R and T structural blocks and their influence on magnetic exchange interactions and anisotropy. Various synthesis techniques including conventional ceramic method, co-precipitation, sol–gel, hydrothermal, spray drying and glass crystallization methods are briefly described in relation to phase formation and microstructural development. The effect of cation substitution, particularly coupled substitutions such as Co²⁺–Ti⁴⁺, Zn²⁺–Ti⁴⁺ and Ni²⁺–Sn⁴⁺, on magnetic and dielectric properties has been highlighted. The importance of these materials in permanent magnets, microwave devices, electromagnetic wave absorption and other high-frequency applications is also presented.

The dynamics of a liquid metal slug driven by electromagnetic induction under an unsteady magnetic field are investigated through experiments and numerical simulations. When a Galinstan slug is subjected to a rotating magnetic field in a circular container filled with an electrolyte solution, it exhibits regular circular revolutions along the circumferential edge of the container. To reveal the spatiotemporal distribution of the electromagnetic field within the slug and the temporal profile of the Lorentz force acting on the slug, we develop a numerical framework that fully resolves the coupled transient phenomena in the multi-physics and multi-phase system. The periodic magnetic field induces locally intensified eddy currents within the slug, which interact with the magnetic field to generate a pulse-like Lorentz force per magnet rotation cycle, eventually promoting the revolving motion of the slug. The maximum magnitude of the Lorentz force acting on the slug increases with the rotational speed of the permanent magnet, and the duration of the strong Lorentz force within the magnet rotation cycle increases with the mass of the slug. Based on the energy balance, a scaling relation that characterises the motion of the slug is developed. Experimental and numerical comparisons demonstrate that the proposed scaling relation predicts the angular velocity of the slug with reasonable accuracy. Our findings highlight a strategy for the remote manipulation of liquid metals, offering insights into soft actuation.

ABSTRACT To solve the problems of excessive overshoot, insufficient precision, and susceptibility to external disturbances in the speed control of permanent magnet synchronous motors (PMSM), a novel sensorless control method is proposed herein. First, a new exponential convergence law was designed and a new sliding mode speed controller was constructed based on this law. An optimisation algorithm combining genetic algorithms and particle swarm optimisation (GAPSO) is proposed to optimise the parameters of the sliding-mode speed controller. Second, inspired by the Cholesky triangular decomposition, the symmetric strong tracking extended Kalman filter (SSTEKF) algorithm is derived from the strong tracking extended Kalman filter (STEKF) algorithm. The experimental results show that the GAPSO method for optimising the sliding mode controller parameters reduces the overshoot and accelerates the convergence speed, improving the control effectiveness of the PMSM, particularly under sudden load changes. Compared with the STEKF algorithm, the improved SSTEKF algorithm has higher accuracy in estimating the rotor speed and position, with the error in estimating the rotor speed reduced from 0.3 to 0.2 and the error in estimating the rotor position reduced from 0.01 to 0.005. Even with sudden load changes, a better observation performance can be achieved.

Abstract In permanent magnet synchronous machine (PMSM)-based servo systems, the intricate interplay of electrical and magnetic dynamics poses many practical challenges, particularly in high-frequency position tracking scenarios. Inappropriate control methods employed with the PMSM may lead to unacceptable phase lags and even jeopardize the connected precision machining or laser processing devices. This article establishes a high-frequency position tracking control framework for PMSM-based servo systems considering dynamic load identification. Therein, a reduced-order generalized proportional-integral observer-based composite control strategy is developed for stator current regulation, aiming at improving the transient/steady-state performance and anti-disturbance capability. An adaptive quasi-proportional-resonant control and a disturbance observer are proposed for position and speed regulations, respectively, enabling the rapid tracking of high-frequency sinusoidal references, as well as the accurate identification of load conditions of the PMSM. The stability of these algorithms is theoretically verified by accommodating the model of the servo system. The superiority of the proposed high-frequency position tracking control framework considering various operating scenarios of the system is verified by diversified simulations and hardware-in-the-loop-based experiments.

Bursting and Spiking Oscillations in a Permanent Magnet Stepper Motor with Load Torque: Dynamical Probing, Microcontroller Execution and Control

ABSTRACT HP steel tubes used in reforming furnaces operate under extreme temperature and pressure, leading to the formation of creep voids in the inner wall. Nucleation of these voids leads to the formation of multiple cracks, when left undetected, may prove catastrophic. In this work, we have investigated eddy current inspections to detect creep induced axial cracks occurring in clusters, emulated by machined notches, located in the sub-surface of retired reformer tube samples. As those tubes were initially exposed to oxidising environments, there is a formation of a thin ferromagnetic layer on the surface of the tube. The probe used for this study, in addition to a rectangular geometry coil for excitation and a Hall sensor for detection, includes permanent magnets to saturate this layer. A study by Finite Element Method (FEM) was conducted to determine the required magnetic remanence to partially saturate the ferromagnetic layer. Boundary Element Method (BEM) was used to rapidly estimate the perturbed magnetic field components due to multiple flaws, in a simplified two-layer stacked geometry. Experiments have been performed over the tube samples containing axial cracks. The results indicate that the proposed technique can detect sub-surface cracks that are nearly 30% of tube thickness.