Abstract To address the challenges of insufficient adhesion, poor obstacle-crossing capability, and low environmental adaptability in traditional tracked wall-climbing robots during operations on vertically curved metal surfaces, this paper proposes a solution for a flexible tracked wall-climbing robot based on permanent magnetic adhesion, which features adaptive curvature capabilities. Firstly, the overall structural design and operational principles of the robot are systematically elaborated, and a mechanical model is established based on its wall motion characteristics. Secondly, to ensure operational stability, critical conditions for slippage and overturning are defined through systematic force analysis, while the adaptive motion principles during obstacle crossing are demonstrated. Building on this foundation, finite element analysis of the magnetic field is conducted on the permanent magnetic adhesion structure, and the influence of magnetic field parameters on adhesion force is systematically explored through magnetic circuit optimization design and parametric simulation of the permanent magnet assembly, ultimately achieving design optimization of the permanent magnet structure. Finally, experimental validation is performed using a physical prototype, confirming the robot's motion flexibility and adaptive capabilities in curved wall environments. The experimental results demonstrate that the designed robot exhibits stable and reliable adhesion, strong load-bearing capacity, and excellent obstacle-crossing performance, providing a viable technical solution for operations in complex metal wall environments.

In response to the demands for high reliability, excellent dynamic response, and high-precision control of advanced aircraft actuation systems, this study focuses on the control technology for the master-master operating mode of dual-redundancy electro-hydrostatic actuation (EHA) systems. A multi-domain coupling model integrating motor magnetic circuit saturation, hydraulic viscosity-temperature characteristics, and mechanical clearances was established, based on which a current-loop decoupling technique using vector control was developed. Furthermore, the study combined adaptive sliding mode control (ASMC) and an improved active disturbance rejection control (ADRC) to enhance the robustness of the speed loop and the disturbance rejection capability of the position loop, respectively. To address the key challenges of synchronous error accumulation and uneven load distribution in the master-master mode, a dual-redundancy dynamic model accounting for hydraulic coupling effects was developed, and a two-level cooperative control strategy of "position synchronization-dynamic load balancing" was proposed based on the cross-coupling control (CCC) framework. Experimental results demonstrate that the position loop control error is less than ±0.02 mm, and the load distribution accuracy is improved to over 97%, fully meeting the design requirements of advanced aircraft. These findings provide key technical support for the engineering application of power-by-wire flight control systems in advanced aircraft.

The paper presents the results of numerical simulations carried out to investigate the influence of selected geometric parameter–precession angle and dimensions of the magnetic circuit of a two-stage magnetic precession gear on the magnetic torques acting on its active components. The operating principle of the proposed gear and the developed numerical model based on the 3D finite element method (FEM) are discussed. The study focuses on the effects of air gap length, magnet dimensions, pole pitch coverage and precession angle. The results confirm a strong correlation between these parameters and the transmitted torque, providing valuable guidelines for the optimal design of high-torque, compact and efficient magnetic precession gears.

This study presents a rotary magnetorheological (MR) damper for a suspension system of low floor vehicles (LFVs) where a large stroke cannot be achieved due to the space constraints of damper motion for special purposes. As is well known, MR dampers are highly suitable for the semi-active suspension systems, which show controllable damping force by an external magnetic field. One of the crucial geometrical parameters to achieve high damping force at the same magnetic field is the suspension stroke in conventional linear MR dampers developed or proposed so far. However, LFVs which include purpose-built vehicles (PBVs) and future smart mobilities, do not have enough space for the linear MR damper installation. Due to the confined space in LFVs, the shape of the MR damper and the magnetic circuit design need to be carefully devised to achieve the target damping force. In addition, the time delay of the MR damper which affects suspension performance should be considered in the modeling and control processing. In this work, the time delay caused by increased inductance is resolved using the Smith compensator, which is integrated into the control system to mitigate the time delay, ensuring effective real-time control. The target control range and operating angle were decided through mathematical modeling and simulation, followed by the prototype fabrication and the measurement of the field-dependent damping force characteristics of the rotary MR damper. Subsequently, a quarter-car suspension model with the proposed MR damper is established to evaluate the suspension performance of LVFs. It is shown from the control simulation that the ride comfort (ISO 2631) is enhanced by up to 21%, while the velocity response is reduced by up to 52% under smooth (ISO B-Class) and rough (ISO D-Class) road profiles, respectively. The results presented in this work are useful guidelines for future smart mobilities featuring the space confinement between floor and road for damper installation in the development of the semi-active MR suspension system.

The proliferation of wireless sensor networks in industrial Internet of Things (IIoT) applications demands sustainable power solutions that eliminate battery replacement requirements while maintaining operational reliability in varying vibration environments. This paper presents a frequency-tunable magnetoelectric (ME) energy harvester that addresses the fundamental challenge of frequency mismatch between ambient industrial vibrations and harvester resonance through position-dependent magnetic force manipulation. The proposed system employs a Terfenol-D/PMNT/Terfenol-D sandwich transducer mounted on a cantilever beam within an adjustable magnetic circuit, enabling continuous frequency tuning through air gap modification for different magnetic field configurations. A comprehensive theoretical framework incorporating position-dependent magnetic forces was developed to predict the system behavior. Additionally, Multi-walled carbon nanotube (MWCNT)-enhanced epoxy bonding layers with 2 wt.% concentration were analyzed and demonstrated six-fold power improvement over conventional epoxy. The experimental validation shows frequency tuning from 40 Hz to 65 Hz through air gap adjustment of only 1 mm, corresponds to a 62.5% tuning range. Further experimental investigation proves a ten-fold power output improvement up to 2 mW by employing a four-magnet circuit design compared to the two-magnet configuration through specific adjustment of the air gap width.

Abstract Hall effect thruster (HET) component manufacturing defects can result in non-uniformities in the plasma plume, significantly affecting thruster performance. The present work quantifies the effect of an azimuthal magnetic field gradient on the thrust, stability, and efficiency of a 5 kW HET. The study introduces an azimuthal magnetic field gradient inside the discharge channel of the P5, a 5 kW HET, through modifications of the outer magnetic coil circuit to simulate the impact of a manufacturing defect in the magnetic circuit. Far-field plasma probes are utilized to measure plasma properties to compare them to the measured performance. A three-dimensional sweep probe apparatus quantifies the effect of the azimuthal magnetic field gradient on the direction of the thrust vector. The azimuthal magnetic field gradient results in decreased stability during operation. The peak-to-peak discharge current oscillations increase by 31.1%, efficiency decreases by 25.7% and thrust decreases by 3.5% (2.7 mN) due to a 16.6% decrease in the local magnetic field resulting in an extreme gradient condition (0.36 G/°). The sweep probe apparatus observes a 24% decrease in the ion beam current and a 5.8° spatial deviation in the thrust vector for the HET with a 0.36 G/° magnetic field gradient. The study presents a physics-based framework that elucidates the observed patterns in thruster performance caused by variations in plasma characteristics. Through the physics-based performance model proposed in the study, the impact of the azimuthal magnetic field gradient on the electron parameters, such as the electron temperature is established. The impact of the azimuthal magnetic field gradient on HET performance and stability is established in the physics-based model by understanding the impact of such a gradient on the motion of the charged particles by utilizing plasma plume parameters.

Testing the rheological properties of magnetorheological fluids often faces challenges in measurement accuracy and magnetic field uniformity. To address these, this study proposes a novel cone‐recess interlocking shear fixture for measuring magnetic flux density and shear yield stress. Finite element analysis simulated the device's magnetic circuit and flux distribution. Comparative experiments confirmed its uniform magnetic field, direct flux density measurement, and high accuracy and repeatability in shear yield stress testing.

This paper presents a flexible femto-tesla detector design using multi-level cascade modules (quantum magnetic chips, semiconductor cooling, graphene superconductors, power supply, and control circuits). The quantum magnetic chip could be any quantum effect-based chip such as tunnel magnetoresistance, superconducting quantum interference devices, spin exchange relaxation-free, optically pumped magnetometers, semiconductor cooling device could be made of bismuth telluride, lead telluride, silicon–germanium, and bismuth antimonide alloys with copper or graphene coated ceramic plate, soft version is preferable to prevent long term cracking issue, the superconductor could be zero resistance based or Meissner effect based, critical temperature high one is preferable, such as graphene, quasi superconduct like Ohno Continuous Casting (CCC) is acceptable as well, power supply and control circuits must be extreme low noise made with the latest chip technology like silicon carbide and silicon nitride. Such design is mainly meant for educational usage. The lower cost is the main design goal. Its magnetic focusing lens combines semiconductors with room-temperature quasi-superconductors. A tapered superconducting disk with a central elliptical hole concentrates magnetic flux by repelling field lines toward the hole, amplifying field strength. Civilian applications include detecting biological magnetism, say, monitoring the student attention level during the study, diagnosing Alzheimer’s and depression in humans/pets. The high-end military uses involve long-range detection of stealth submarines, carriers, tanks, and stealth aircraft. The main challenge of designing such a system is to understand the environment magnetic noise fluctuation patterns, as such, we have conducted short and long term measurements to catch the effect of Moon cycle on the background noise, these data and analysis will allow us to design an advanced Karman filter to remove the Moon noise, to see femto-Tesla variation in a more accurate design.

This paper proposes a solution to enhance the torque production capability of Permanent Magnet Synchronous Machine (PMSM), utilizing not only the unused space resulting from the stator end windings on the rotor side, but also the otherwise unused space around the winding on the yoke side. By implementing an additional axial rotor equipped with Permanent Magnets (PMs) in both rotor and yoke sides, the proposed design technique increases the PMSM torque output, taking advantage of the useless space on the yoke side. In the proposed configuration, one magnetic flux path circulates between the PMs on the rotor (rotor side) and the stator, while an additional flux path circulates between the PMs positioned on both sides of the stator end windings. These two flux paths contribute to generating a stronger and more effective magnetic field within the machine than conventional structure, resulting in increased torque density. A magnetic equivalent circuit (MEC) model of the proposed design is developed, and its accuracy is validated through Finite Element (FE) analysis. For a fair evaluation, the proposed structure is compared with a conventional configuration using the same volume of PM material. Furthermore, optimization of the proposed design is carried out to maximize Torque/PM.

Analysis of Circulating Current in Electrical Machines Using Mesh-Based Magnetic Equivalent Circuit

Study and optimization on the ferrofluid seal with Sandwich magnetic circuit

A technique for determining magnetic conductivities and the main magnetic flux through the winding coil in a brushless direct current motor has been developed. It has been noted that the peculiarity of the proposed technique is that it takes into account the edge effect and scattering fluxes, as well as their dependence on the rotor position coordinate. Based on the analysis of a two-dimensional finite element model of the magnetic field of a brushless direct current motor magnetic system, an approach has been proposed for determining the distribution coefficients of the main magnetic flux of a tooth in the stator yoke. Expressions have been obtained for calculating the scattering coefficients and the edge effect in the magnetic system of a brushless direct current motor. It has been highlighted that the developed technique allows solving the problem of quantitatively determining the value of the main magnetic flux through the winding coil of a brushless direct current motor with high accuracy. It has been indicated that the proposed model makes it possible to determine the degree of influence of the geometric parameters of the magnetic circuit on the nature of the change in the main magnetic flux through the winding coil with the least amount of time. It has been established that the developed analytical model can be applied in the process of optimization of brushless direct current motors.

Abstract In order to solve the problem that the output damping force of the traditional magnetorheological damper is limited due to the low space utilisation of the piston head. A novel series flow channel magnetorheological damper (NSFC-MRD) was proposed. The structural design of NSFC-MRD was completed. The magnetic circuit model and damping force model of NSFC-MRD were established. In order to verify the performance advantages, the effects of key parameters on the damping characteristics of NSFC-MRD and conventional MRD are comparatively analysed by the finite element method under the constraints of the same piston outer diameter and cavity volume. The influence law of NSFC-MRD damping performance is revealed. A prototype of NSFC-MRD was manufactured and the damping performance of NSFC-MRD was tested. The results show that NSFC-MRD reduces the damping channel length in the unactivated zone by 28% in the same region. The viscous damping force is improved to approximately three times that of conventional structures. The piston radial space utilization rate of NSFC-MRD is improved by about 46% compared to traditional structures. When I= 2 A, A= 8 mm and f= 1 Hz, the maximum damping force of NSFC-MRD is up to 6893 N and the adjustable coefficient is up to 6.26.

Simulation analysis and performance evaluation of a novel magnetorheological damper with composite flow channel and curved magnetic circuit

Purpose This work aims to develop a method that balances computational efficiency and accuracy for evaluating the performance of linear electromagnetic actuators (LEAs) in the presence of stray magnetic fields (SMFs). Design/methodology/approach This paper presents a loop-equation-based magnetic equivalent circuit network (MECN) model for evaluating the electromagnetic characteristics of LEAs in the presence of SMFs. By using magnetic flux as the state variable, the proposed model enables analysis of leakage flux in windings. In this approach, SMFs are introduced as boundary conditions, thus reducing computational complexity. A solenoid-type LEA is used as a case study, and the accuracy of the proposed MECN is validated through comparison with finite element analysis (FEA) results. Findings The results demonstrate that the loop-equation-based MECN achieves good agreement with FEA simulations while significantly improving computational efficiency. This indicates that the proposed approach provides both reliable accuracy and reduced computational cost for analysing LEAs under SMFs. Originality/value This study proposes a loop-equation-based MECN method that introduces magnetic flux as a state variable, enabling analysis of magnetic fields in current-carrying regions. By incorporating SMFs as boundary conditions, the model is simplified, thus enhancing computational efficiency.

This paper describes about improvement the power character using nonlinear inductance in SWPGS with AMPTC. Wind power generation system is a one that converts the kinetic energy of the wind into electrical energy. In particular, it is very important to increase the operation efficiency because small wind power systems can be used as an efficient independent power source in areas with large power demand and no other energy sources. The SWPGS with AMPTC consists of a wind turbine, a PM generator, two rectifiers, a battery and a load. The wind turbine is a horizontal axis with three blades and the PM generator has a structure with the reactance bridges and two Y-connected winding sets. This system can automatically track the maximum power from the wind by changing the nonlinear inductance without the need for converters and control circuits. At this time, the variation of the nonlinear inductance follows the saturation characteristic of the reactance bridges in the internal magnetic circuit of the generator. In this paper, using this principle, the problem of fully approaching the maximum power curve of a wind turbine with the power characteristics of a wind power system following the rotational speed change is mathematically modeled. In other words, the output characteristics of SWPGS with AMPTC were close to the concave characteristics as well as the maximum output characteristics of wind turbines. Finally, without control circuit, the load power characteristic curve was allowed to operate at the maximum power point of the wind turbine. We also verified the accuracy of the theory by changing the nonlinear inductance in a stand-alone small-scale wind power system through simulation analysis using MATLAB.

We propose an electric circuit that generates a high magnetic field with a variable pulse width using insulated gate bipolar transistor (IGBT) switching. One method to realize a magnetic field with a variable pulse width is to switch the circuit open and short using semiconductor devices. However, in the case of a coil load used to generate a high magnetic field, inductive energy is released as a surge voltage during high-current switching, which can lead to the failure of switching devices. Therefore, we proposed connecting an external circuit in parallel with the coil to absorb and dissipate the inductive energy and analyzed the surge voltage and current waveforms generated in the circuit. The analytical solution based on circuit analysis and the circuit simulation results showed good agreement, indicating the transient response waveforms of the current and surge voltage in the proposed circuit. Moreover, the results reveal a trade-off between the surge voltage and the current decay time constant, depending on the resistance and capacitance values of the external circuit. A switching circuit with anti-series connected IGBTs demonstrated the interruption of the discharge current (500A peak, 1ms FWHM pulse width, 3kV surge voltage) at arbitrary timing for driving the magnetic field. From these results, a pulsed magnetic field with a variable pulse width was implemented.

In order to solve the problems of the unadjustable magnetic field of the permanent magnet generator and the high failure rate of the brush claw pole electric excitation generator, a new type of dual‐rotor hybrid excitation generator (HEG) is proposed, which is composed of a suspended brushless claw pole electric excitation rotor and a built‐in combined magnetic pole permanent magnet rotor. A magnetic field analysis method for the new HEG is proposed, which establishes equivalent magnetic circuit models considering the leakage flux and magnetic circuit distribution. The end leakage flux path of the permanent magnet rotor and the axial leakage flux path of the claw pole rotor are analyzed. The main magnetic flux and air gap magnetic flux of the permanent magnet rotor and claw pole rotor are calculated by using the equivalent magnetic circuit method and mesh hole method. Through the finite element method, the leakage flux coefficient of the synthetic magnetic field of the HEG is calculated, and the electromagnetic performance is analyzed to verify the correctness of the magnetic field analysis method and the rationality of the magnetic field distribution. Finally, a prototype is built and tested. The results show that the proposed HEG has the advantages of a wide magnetic regulation range, stable output voltage, and good output performance. © 2025 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

This study presents the development and comprehensive evaluation of a novel normally closed magnetorheological brake (NC-MRB) that synergistically combines permanent magnets and electromagnetic coils to achieve both fail-safe braking and adaptive torque control. The research methodology encompasses: (1) theoretical modeling using equivalent magnetic circuit theory to analyze the coupled magnetic fields from permanent magnets and excitation coils; (2) finite element simulations verifying the magnetic circuit design and confirming the working gap’s field strength satisfies MRF phase transition requirements; and (3) systematic experimental characterization of the brake’s torque performance. The results demonstrate three distinct operational modes: (i) a fail-safe braking torque of 14.5 N·m at zero excitation current, (ii) torque enhancement up to 32 N·m with forward current (positive correlation), and (iii) torque reduction to 2.5 N·m with reverse current (negative correlation). These findings validate the proposed hybrid excitation system’s ability to provide reliable power-off braking while enabling precise, continuous torque modulation. The study establishes both theoretical frameworks and experimental benchmarks for optimizing safety-critical MR brake systems, advancing their application in scenarios demanding fail-safe operation and dynamic controllability.

This paper focuses on the design and performance of magnetic fluid acceleration sensors, systematically sorting out their theoretical basis, structural design, magnetization characteristics and dynamic response mechanism. Magnetic fluid, as a new type of functional material with both ferromagnetism and fluidity, has broad application prospects in inertial sensors due to its unique field control behavior. The article first reviews the development history of magnetohydrodynamic sensors at home and abroad, covering various sensing forms such as micro-pressure difference, tilt Angle and acceleration, and points out that its modular design provides a technical path for multi-dimensional performance optimization. In terms of theoretical modeling, the article establishes a second-order inertial system model of the magnetohydrodynamic acceleration sensor, clarifies the action mechanisms of magnetic buoyancy and magnetic viscosity in restoring force and damping, and realizes the conversion of acceleration to electrical signal based on inductance and Hall elements respectively. Magnetic property analysis indicates that the magnetic fluid exhibits superparamagnetism, and its saturation magnetization intensity (coal-based > oil-based > water-based) is directly related to the sensor's sensitivity and dynamic range. The rationality of the magnetic circuit design was verified through COMSOL finite element simulation, revealing the key influence of magnetic gradient on displacement detection. The dynamic performance test results show that the coal-based magnetohydrodynamic sensor has the optimal transient response (rise time 0.122 s, stabilization time 0.323 s, overshoot 11.4%) and maximum bandwidth (25.37 rad/s), indicating that it is suitable for high-frequency vibration scenarios.