The Partial Element Equivalent Circuit (PEEC) method is a powerful electromagnetic modeling and analysis tool capable of converting complex electromagnetic field problems into circuit problems, demonstrating broad application prospects. The calculation of discretized element parameters constitutes one of the key technologies in the PEEC method. To address this, this paper investigates semi-analytical calculation methods for partial inductance within the PEEC framework. The research first employs an iterative algorithm based on Bartky transformation to calculate the inductance of toroidal fundamental elements. Subsequently, the self- and mutual inductance of rectangular fundamental elements are studied, where a normalized geometric parameter approach is introduced to simplify complex integral expressions, making them suitable for computer-aided semi-analytical computation. The accuracy and efficiency of the proposed semi-analytical method are validated using the Finite Element Method (FEM) for both element types through comparative analysis. Building upon the partial inductance calculations, the PEEC method is further applied to compute the impedance of rails. Comparative results with FEM simulations confirm the feasibility and effectiveness of the PEEC approach based on semi-analytical inductance calculations. This work paves the way for extending PEEC applications to broader domains.

The Epstein frame is widely adopted in one-dimensional magnetic measurement methods. However, in certain cases, the iron loss calculated based on the test results of the Epstein ring method differs significantly from the actual measured values. To address this issue, this paper presents a study on the magnetic properties of toroidal silicon steel laminations. Firstly, finite element analysis (FEA) of toroidal silicon steel laminations was performed. By analyzing and comparing the magnetic field distribution along the radial direction within the toroid, key factors influencing its magnetic properties were preliminarily identified. Based on the magnetic field simulation results, the magnetic characteristics of toroidal cores with varying parameters were then experimentally measured. The integrated analysis of computational and experimental results demonstrates that the ratio of outer diameter (Do) to inner diameter (Di) primarily affects the fundamental magnetization curve and the magnetic field distribution; the effective magnetic path length has a significant influence on the core loss curve; while the lamination thickness exhibits a negligible effect on the magnetic properties under the conditions studied.

Amorphous alloy materials are highly interested for high-speed applications because of low iron loss and high magnetic permeability, in comparison with conventional silicon steel materials. The iron loss in the stator of high-speed permanent magnet (HSPM) motors is difficult to be measured directly, and it increases with working frequency regardless of the material used. The accurate calculation of HSPM motor iron loss is significant for the design and analysis of the high-speed motor. In this paper, a calculated method of iron loss for high-speed motors is proposed by combining the ring specimen measurement, Preisach hysteresis model and finite element analysis. The magnetic properties of two ring specimens are measured, both of which are manufactured using the same processing technology as motor cores. The database of frequency-dependent Everett functions for the Preisach hysteresis model is established based on measurement data. An identification algorithm based on the symmetric minor hysteresis loops of the Preisach hysteresis model is adopted. The iron loss of an amorphous alloy and a silicon steel HSPM motors are calculated using the proposed method, from which the iron loss differences due to different materials are quantitatively analyzed. To verify the analysis results, motor experiment is executed by utilizing the high-speed airflow test platform and the non-magnetized motor experiment platform. The performance of amorphous alloy and silicon steel HSPM motors are tested at the same operating frequency, including total losses and efficiency etc. The air friction and mechanical losses in two motors are measured through non-magnetized motor experiments, and proved to be equal. The validity and accuracy of proposed method is verified with comparison results of loss separation model and motor experiments, which demonstrates the applicability of Preisach hysteresis model for calculating iron losses in high-speed motors.

Laser welding technology has significant advantages in the precision machining and mass production of metal bipolar plates for fuel cells due to its characteristics of high precision and high efficiency. However, in the welding of ultra-thin metal bipolar plates, problems such as difficult-to-control weld quality and welding thermal deformation exist. To solve the above problems and optimize the welding process window more efficiently, a Gaussian surface-cylinder compound heat source model based on the non-penetrating welding of ultra-thin metal bipolar plates was constructed using COMSOL Multiphysics. A full factorial analysis scheme with four factors and five levels was constructed by adopting three parameters: penetration depth, weld width, and joint width. A BP neural network model was trained through JMP software combined with the actual weld pool morphology, making the modified simulation model closer to the actual welding weld pool. The test results show that when the modified laser heat source model is used for the welding process simulation, and the simulation results are compared with the actual bipolar plate welding test results, the relative errors between the simulation data and the test data are all within ±5%. This indicates that the model can well guide the actual engineering practice of the laser welding process for metal bipolar plates in the future.

The I-f control can be stabilized by adjusting the reference frequency and current magnitude via active and reactive power loops, respectively, extending its utility beyond the conventional startup phase of sensorless surface-mounted permanent magnet synchronous motor (SPMSM) drives. However, existing power-based methods lack theoretical tuning guidance and suffer from limited load capability. This paper establishes a full-order analytical framework based on the proposed 7th- and 8th-order small-signal models. Root locus analysis reveals that system stability under the worst-case zero $d$-axis current condition is dominated by the integral term of the internal reactive power ($Q_{i}$) controller, with the proportional term providing auxiliary damping. A step-by-step parameter tuning method is proposed to ensure baseline stability and enhance load capability. To address inherent low-speed instability, a smooth deactivation method is developed. A dynamic $Q_{i}$ regulation strategy is introduced to prevent pole-slipping during zero-current deceleration. Comprehensive experiments on a 0.75 kW SPMSM validate that the proposed methodology withstands rated step loads, achieving stable operation across a wide speed range, including full-load acceleration and deceleration.

The extraction of high-resolution rotor position and speed from the Hall signals of permanent magnet synchronous motors (PMSMs) can be achieved through a filtering process based on second-order generalized integrators (SOGIs) and a phase-locked loop (PLL). This article proposes a novel SOGI-based cross-coupled PLL (CCSOGI-PLL) method that incorporates a notch coefficient, $d$, to enable arbitrary tuning of the notch filter for negative sequence components. The article also presents an investigation of the corresponding parameter design. Furthermore, the combined effect of permanent magnet and Hall device installation errors is analyzed, demonstrating that the proposed filtering approach is a viable alternative to complex compensation schemes. To facilitate implementation in low-cost drivers, the article develops an implicit Tustin discretization method for stable filtering across a wide frequency range and introduces a state presetting technique to enhance stability during startup and bidirectional operations. The effectiveness of the proposed strategy is experimentally verified on a 0.75 kW treadmill motor.

The main purpose of this paper is to study the nonlinear dynamic characteristics of a hybrid electromagnetic suspension system for high-speed Maglev trains, addressing the essential engineering problems of maintaining stable suspension under aerodynamic disturbances. A one-degree-of-freedom model is established, which incorporates electromagnetic forces generated by permanent magnets and control coils, along with a proportional-derivative controller using cubic displacement feedback. The system is transformed into a dimensionless state-space model to perform a comprehensive stability and bifurcation analysis. The stability of such a system is found to be strongly dependent on the damping parameters and magnetic stiffness. Furthermore, equilibrium analysis is used to show the transitions that occur between stable operating states and unstable saddles or spirals. The system displays complex behaviors under periodic aerodynamic excitation, such as a hidden chaotic attractor and the confirmed existence of chaotic motion indicated by positive Lyapunov exponents. One-and two-dimensional bi-furcation diagrams are plotted to clarify the parameter regions where periodic, quasi-periodic, and chaotic motions occurred. The results provide crucial design guidelines by identifying safe operational envelopes and dangerous instability zones. This study delivers a practical framework for optimizing hybrid electromagnetic suspension controller parameters to suppress chaotic vibrations and ensure robust, stable performance in next-generation high-speed Maglev transportation systems.

The magnetic properties and iron losses of the soft magnetic materials are susceptible to temperature increase and are difficult to be accurately simulated and calculated. In this article, an improved temperature dependence Preisach hysteresis model for soft magnetic materials is proposed, which can be used to describe the hysteresis behavior of materials at various ambient temperatures. The nonlinear influence of temperature is introduced by establishing the relationship between magnetic field strength and temperature. The hysteresis loops at various different temperatures are measured using ring specimens, to construct and identify the Everett function database. The iron loss of soft magnetic materials at different temperatures can be calculated using the proposed model. The validity and accuracy of the proposed model are verified by comparing the calculated results with the experimental measurement results.

In this article, a novel checkerboard array pole (CAP) magnetic lead screw (MLS) is proposed. Compared with the traditional MLS, the proposed CAP-MLS can not only save permanent magnet (PM) consumption but also provide enough thrust for application. To save PM consumption, PM and iron teeth are alternately mounted to form a circle of helical magnetic poles on the mover of the proposed CAP-MLS. Meanwhile, the traditional pure PM helical poles are mounted on the rotor to increase the maximum thrust and torque. On the other hand, a 3-D analytical model (AM) based on the superposition theory for the proposed CAP-MLS is established to analyze and predict the magnetic field distribution in air gap, thrust force, and torque. The analytical results are compared with those from a 3-D finite element AM and experimental prototype to verify the effectiveness of the proposed novel topology and its corresponding 3-D AM.

The pulse width modulation (PWM) technique is commonly utilized in voltage-source inverters for driving motors, but its application introduces a large number of harmonics into the voltage and current of the motor, resulting in an increment in iron loss. This paper reveals the underlying mechanism of iron loss increment caused by PWM harmonics based on the hysteresis behavior of soft magnetic materials. An iron loss calculation method that integrates an advanced hysteresis model with strategy-circuit-field simulation is proposed. This approach accounts for the interaction of motors and the inverters to obtain the distortion and distribution of current harmonics caused by PWM. The visual correlation between harmonic components and iron loss is established directly through the hysteresis performance of materials. The mechanism of the increment in iron loss due to PWM harmonics is explored and revealed thoroughly from point to line to the surface of the motor core. Additionally, the influence of PWM parameters on iron loss is comprehensively analyzed, providing a criterion for the optimization of motor performance. The accuracy and reliability of the proposed method are verified by experiments under various conditions.

Metal bipolar plates are important components of fuel cells, playing a role in conducting electricity, gas, and heat during the operation of fuel cells. The sealing and joint quality of the bipolar plates have a significant impact on the performance and service life of fuel cell stacks. In actual production, laser technology is often used for welding bipolar plates, and the welding quality is ensured by laser process parameters when using the same equipment. Therefore, in order to further optimize the laser welding process of metal bipolar plates, this paper selects three laser parameters for single-factor analysis to evaluate the impact of each parameter on laser welding quality. The Box-Behnken design-response surface method is used for multi-factor analysis, with process parameters as inputs and weld quality parameters as outputs, to assess the sensitivity of each laser process parameter to laser welding quality, and to fit a nonlinear function. Based on the results, the optimal welding process window is derived to improve the quality of the welds in the actual welding process. Finally, a comprehensive welding quality assessment system is established on the premise of reducing costs and improving quality.

In order to improve the production efficiency of industrial equipment, how to design servo system to further reduce the position overshoot and shorten the positioning time has become the focus of current research. In this paper, a high positioning response control scheme based on decoupled extended state observer is proposed. Firstly, the coupling problem of traditional extended state observation is analyzed, and a speed controller based on decoupled extended state observer is designed, which achieves the decoupling of tracking performance and anti-disturbance performance, and simplifies the tunning of control parameters. Secondly, aiming at the problem that the overshoot of the position servo system based on the former designed speed controller becomes larger, a position control method with compensation controller is proposed, which improves the bandwidth of the position loop, and has the same characteristics as the first order inertia system in response to the command, with the advantage of small overshoot. The experimental results show that the proposed control scheme can reduce position overshoot, shorten positioning time, and has good anti-disturbance performance.

Recently, humanoid robots with personification behavior and high working efficiency have received significant attention. Meanwhile, high-torque-density motors, which serve as the core power source for robot joints, have also been widely researched. In this paper, a high-torque-density double-stator permanent-magnet (DSPM) motor is designed for robot joint applications, and its outer stator (OS) split ratio (the ratio between the inner and outer diameters of the OS) and inner stator (IS) split ratio (the ratio between the inner and outer diameters of the IS) are analyzed and optimized. Since the DSPM motor has different heat dissipation capabilities for the OS and IS, their different loss limitations should be considered to avoid the risk of local overheating, especially for the IS. This paper shows that the loss limitations affect the optimal OS and IS split ratios, as well as the maximum average torque. The IS loss limitation increases the optimal OS split ratio and decreases the optimal IS split ratio; however, the OS loss limitation has the opposite effect. Additionally, an investigation into the electromagnetic characteristics of the optimized DSPM motor was conducted using the finite element method. Finally, a prototype was manufactured, and the results of the temperature rise experiments verified the feasibility of the proposed DSPM motor and the effectiveness of the optimal method.

Owing to the elimination of physical sensors, sensorless speed control systems for induction motors are gaining increasing popularity. Nevertheless, the low-speed performance of these systems still warrants further enhancement. Speed sensorless control based on the model reference adaptive system (MRAS) has garnered widespread attention, primarily attributed to its robust adaptability and computational simplicity. This paper proposes an improved measure for induction motors, addressing the instability of traditional stator current based MRAS at low speeds. Based on Lyapunov stability theory, the adaptive law of MRAS is modified, and a coefficient is introduced to correct the rotor flux-producing current. The observer performance is further enhanced by configuring the feedback matrix. The feasibility and efficiency of the proposed method have been validated through both simulation and experimental measurement.

Direct-driven generation is considered one of the most reliable selections in wave energy conversion systems. Therefore, a direct-driven linear-rotary wave generator (LRWG), which can transfer the low-speed linear wave motion to the high-speed rotating motion of the rotor and then generate electrical power simultaneously, is proposed in this paper. The proposed LRWG comprises three parts: translator, common rotor, and stator. From the energy view, the proposed LRWG can be divided into two sections: the energy transmission section to increase the velocity of the wave and the energy conversion section to generate power. The initial design method is given to determine the main dimensions of the proposed LRWG. To meet the maximum power tracking control requirements, a multi-mode and multi-objective optimization method, which can consider both generator and motor mode, is proposed to improve the performance of the proposed LRWG by sensitivity analysis, response surface methodology, and non-dominated sorting genetic algorithm II method. Finally, a prototype and its experimental platform are developed based on one of the optimization schemes from the possible solutions to verify the proposed approach and the performance of the proposed LRWG.

The vibration isolation platform, operating in the harsh space environment, faces the potential risk of actuator failure. Consequently, fault-tolerant capability becomes paramount for the platform to successfully accomplish on-orbit tasks. Considering the nonlinear characteristics of the vibration isolation platform in large angle motion, multiple degrees of freedom (multi-DOF) coupling nonlinear dynamic model is established. The Active Disturbance Rejection Control (ADRC) is designed to control the vibration isolation platform according to the nonlinear characteristics of the platform. To reduce the influence of the actuator fault on the performance of vibration isolation, a fuzzy ADRC controller is proposed. The controller combines the adaptability of fuzzy logic with the nonlinear control capabilities of the ADRC controller. The control parameters can be adjusted in real-time, thereby effectively coping with dynamic changes under various degrees of actuator failure. Specifically, research has been conducted on the fault tolerance performance of the isolation platform under one actuator, two actuators, and three actuator failures. Finally, the correctness of the proposed nonlinear dynamic model and the effectiveness of fuzzy ADRC controller has been demonstrated through simulation and experiment. The fault-tolerant control strategy provides technical support for the stable operation of isolation platforms in complex space environments.

To reduce the time consumption of dynamic performance analysis and optimization design for the hybrid excitation magnetic lead screw (HEMLS), a two-dimensional (2-D) mesh-based (MB) magnetic equivalent circuit (MEC) model is proposed. In the proposed model, the mesh structure of the proposed model doesn't need to rebuild for each time instant, and only the parameter value of each element needs be updated to describe the status of HEMLS. To simply the proposed mesh-based MEC model, both PM and current exciting sources in one pole are together considered as one magnetomotive force. Meanwhile, the density of the mesh can be adjusted according to the solution region to decrease the time consumption. Finally, the proposed MB-MEC model is verified by comparing it with the static thrust force from the finite element method and prototype test under load and no-load conditions.

The traditional sliding mode observer (SMO) for permanent magnet synchronous motor (PMSM) has low accuracy and poor sinusoidality in observing back-electromotive force (EMF), resulting in noticeable chattering and large errors of estimated rotor position and speed. To address these issues, this paper proposed an improved SMO based sensorless control strategy for PMSM. Firstly, a high-order SMO (HSMO) is analyzed, in which the back-EMF is introduced as a new state variable of the traditional SMO. Then, an improved SMO which contains a high pass filter-low pass filter (HPF-LPF) structure is proposed. In order to achieve good filtering effect, two HPF-LPFs are adopted and cascaded. The comparative analysis and experiments results show that the performance of the proposed two HPF-LPFs-based SMO is comparable to that of HSMO.

Joint motors are the core power source of highly dynamic humanoid robots, requiring designs with high torque density and low torque ripple. Due to the unique permanent magnet arrangement, Halbach array with a magnetic flux focusing effect is a promising candidate for use in joint motors of humanoid robots. Based on various Halbach array configurations (two-segment, three-segment, and four-segment) and magnetization angles, this paper investigates the difference of electromagnetic performance between traditional radial magnetization and Halbach array configurations in outer rotor permanent magnet synchronous motors (PMSMs), including air gap flux density, back EMF, cogging torque, electromagnetic torque, and motor losses. The results indicate that each Halbach array configuration has an optimal magnetization angle to achieve the maximum torque. Moreover, the three-segment Halbach array configuration shows an 11.4