Coaxial Magnetic Gear Research Articles

Chaotic behaviour in the dynamical response of coaxial magnetic gears during acceleration

Slippage during acceleration has been a significant issue in coaxial magnetic and has been thoroughly investigated in the recent years. Depending on the applied outer load it is important to know the maximum acceleration that can be induced so that the system will not diverge. In the present work a non-dimensional analysis has been conducted in order to develop a stability criterion for the maximum acceleration that can be applied to the system as a function of the outer load. A closed-form relation for the period of the oscillations of the system that will be caused by the acceleration, has also been derived. Furthermore, the case of acceleration with ripple has been investigated. It was demonstrated that during acceleration with ripple under constant applied outer load, the system showcases a chaotic behaviour similar to the driven pendulum. In particular, a thorough analysis on the frequency of the ripple has been conducted. It was observed that when the ripple frequency was slightly lower than the frequency of the oscillation under steady acceleration, the system could potentially diverge even if the acceleration of the system was lower than the critical value. With the present work, a detailed non-dimensional model has been derived that could be a useful tool for determining the stability of coaxial magnetic gears without the requirement of numerical solution of the governing equations. In addition, some interesting observations are made regarding the chaotic behaviour of the dynamical response of coaxial magnetic gears during acceleration with ripple.

Optimum design of a coaxial magnetic gear integrated with a permanent magnet synchronous generator of a wind turbine based on the pelican optimization algorithm

This paper presents an optimum design of a coaxial magnetic gear (CMG) Integrated with a Permanent Magnet Synchronous Generator (PMSG) of a wind turbine using a pelican optimization algorithm (POA) launched in 2022. In order to evaluate the proposed system design based on POA, the well-known Particle Swarm Optimization (PSO) is implemented for the same CMG under the same conditions and constraints. Also, a Taguchi-method-based sensitivity analysis for the key design variables is employed to determine their impact on the system’s performance. The optimization process for the CMG design based on POA and PSO is executed based on the 2-D Finite element analysis (FEA) using the Finite Element Method Magnetics (FEMM) program. The results obtained from the POA and PSO are compared and analyzed. The results underline that the optimum design for the CMG/PMSG integrated system based on POA achieves more torque/weight ratio and then more generated power and currents as compared to PSO. It is concluded that the proposed design based on POA gives a superior and efficient design with substantial stability and rapid convergence.

Detailed Investigation of the Eddy Current and Core Losses in Coaxial Magnetic Gears through a Two-Dimensional Analytical Model

This work introduces a 2D model that calculates power losses in coaxial magnetic gears (CMGs). The eddy current losses of the magnets are computed analytically, whereas the core losses of the ferromagnetic segments are computed using an analytical–finite element hybrid model. The results were within 1.51% and 3.18% of those obtained from an FEA for the eddy current and core losses in the CMG for an indicative inner rotor speed of 2500 rpm. In addition, the significance of the circumferential magnet segmentation is demonstrated in the CMGs. Furthermore, a parametric investigation of the efficiency of the system for different applied external loads is carried out. Finally, a mesh sensitivity analysis is performed, along with the computation of the average power losses throughout one full period, resulting in an at least 80% reduction in computational costs with a negligible effect on accuracy. The developed model could be a valuable tool for the minimization of power losses in CMGs since it combines high accuracy with a low computational cost.

Theoretical and experimental comparison of gear systems: Planetary mechanical transmission and coaxial magnetic gear

Gear systems in today’s industry are one of the critical pillars providing power transformation and matching speed and torque to application requirements. Reliability, high efficiency, and low operating costs are desirable due to the prevalence of gearboxes. This paper provides a comparative analysis of selected mechanical and magnetic gears, using a specific example to point out the advantages and disadvantages of contactless power conversion. After determining the essence of the operation of the magnetic gear on the base model, two magnetic gear optimization cases are presented, testifying to the application potential. An analysis of the stress distribution in the area of the teeth of the mechanical gearbox and the most stressed element of the magnetic gear - the modulator, was carried out. The effects of temperature and load on losses were measured and simulated, and ultimately, the efficiency characteristics of the two gears were also compared.

Torque Calculation and Dynamical Response in Halbach Array Coaxial Magnetic Gears through a Novel Analytical 2D Model

Coaxial magnetic gears have piqued the interest of researchers due to their numerous benefits over mechanical gears. These include reduced noise and vibration, enhanced efficiency, lower maintenance costs, and improved backdrivability. However, their adoption in industry has been limited by drawbacks like lower torque density and slippage at high torque levels. This work presents an analytical 2D model to compute the magnetic potential in Halbach array coaxial magnetic gears for every rotational angle, geometry configuration, and magnet specifications. This model calculates the induced torques and torque ripple in both rotors using the Maxwell Stress Tensor. The results were confirmed through Finite Element Analysis (FEA). Unlike FEA, this analytical model directly produces harmonics values, leading to faster computational times as it avoids torque calculations at each time step. In a case study, a standard coaxial magnetic gear was compared to one with a Halbach array, revealing a 14.3% improvement in torque density and a minor reduction in harmonics that cause torque ripple. Additionally, a case study was conducted to examine slippage in both standard and Halbach array gears during transient operations. The Halbach array coaxial magnetic gear demonstrated a 13.5% lower transmission error than its standard counterpart.

Nonlinear control of coaxial double rotor magnetic gear based on high gain observer in wind turbine

AbstractThis paper proposes a nonlinear control law with a dynamic controller based on high gain observer (HGO) for a co‐axial double rotor magnetic gear (CADRMG) based on Halbach array used in wind turbines. The generalized canonical form (GCF) is used to normalize the nonlinear augmented system to achieve the dynamic control signal with a chain of integrator of system output. In addition, a tracking problem is defined to track high speed rotor (HSR) with respect to GCF. On the other hand, the HGO is used to estimate the error tracking at the expense of nonlinear terms. Furthermore, the nonlinear system observability of the augmented system is evaluated. A dynamic control law is used to solve the tracking problem based on HGO. This controller can eliminate the effect of load torque as a constant and unknown disturbance in the closed‐loop system. Moreover, the closed‐loop stability of the system under dynamic signal control is guaranteed. The system states estimation is calculated by recursive equations from tracking error estimations. Finally, numerical simulations are given to illustrate the theoretical results of proposed system.

Physics-informed neural network for simulating magnetic field of coaxial magnetic gear

In the process of performance analysis and structure optimization of coaxial magnetic gear, an emerging method for precise magnetic field simulation remains a focal point in engineering research. In this study, we introduce a physics-informed neural network to model the magnetic field of a magnetic gear. We employed a physics-based loss function to optimize neural network parameters to solve the magnetic field of a Maxwell-controlled magnetic gear. Additionally, we developed a joint training model that leverages the continuity of the medium interface. The feasibility of the model was confirmed by solving the magnetic field of a permanent magnet, with an error margin of less than 5%. The model exhibited excellent precision in simulating magnetic field behavior within magnetic gears. We demonstrate that adjusting model parameters enables the creation of a proxy model, which effectively addresses analogous problems. Furthermore, leveraging transfer learning substantially diminishes training time for similar tasks, resulting in a 43% reduction in training cost. Finally, we propose an enhanced physical information neural network with data-physical drive fusion and use a special Poisson's equation solution in the magnetized region as a data drive during training. The enhanced physics-informed neural network effectively solved the magnetic field of a magnetic gear, resulting in a 50% improvement in solution accuracy. This study establishes the groundwork for analyzing and optimizing magnetic gears, providing new research insight for electromagnetic practitioners.

Formulation of a non-dimensional criterion for stable dynamical response in coaxial magnetic gears

Formulation of a non-dimensional criterion for stable dynamical response in coaxial magnetic gears

Surrogate-Based Multi-Objective Optimization of Flux-Focusing Halbach Coaxial Magnetic Gear

Due to their contact-free and low-maintenance features, magnetic gears (MGs) have been increasingly investigated to amplify the torque of electric motors in electric vehicles (EVs). In order to meet the requirements of propelling EVs, it is essential to design an MG with a high torque density. In this paper, a novel flux-focusing Halbach coaxial MG (FFH-CMG) is proposed, which combines the advantages of flux focusing and Halbach permanent magnet (PM) arrays. The proposed structure has a higher torque performance and greater efficiency than conventional structures. A multi-objective design optimization based on a surrogate model is implemented to achieve the maximum volumetric torque density (VTD), torque-per-PM volume (TPMV), and efficiency, as well as the minimum torque ripple, in the proposed FFH-CMG. The employed optimization approach has a higher accuracy and is less time-consuming compared to the conventional optimization methods based on direct finite-element analysis (FEA). The performance of the proposed FFH-CMG is then investigated through 2D-FEA. According to the simulation results, the optimized FFH-CMG can achieve a VTD of 411 kNm/m3, and a TPMV of 830 kNm/m3, which are significantly larger than those of the existing MGs and make the proposed FFH-CMG very suitable for EV applications.

Analysis of a coaxial magnetic gear optimally designed using Particle Swarm Optimization

Analysis of a coaxial magnetic gear optimally designed using Particle Swarm Optimization

The Optimal Design and an Analysis of a Hybrid W-Shaped IPM Rotor of Coaxial Magnetic Gear

The Optimal Design and an Analysis of a Hybrid W-Shaped IPM Rotor of Coaxial Magnetic Gear

Design and Optimization of Coaxial Magnetic Gear With Double-Layer PMs and Spoke Structure for Tidal Power Generation

A coaxial magnetic gear (CMG) with double-layer permanent magnets (PMs) and Spoke structure is proposed to replace the mechanical gearbox in tidal power generation system. For the inner rotor PMs, the distributions of PMs are the spoke structure with different sizes, and the magnetization direction is Halbach array. The outer rotor PMs have two layers, one is Halbach array, and the other is radial magnetization. According to the sensitivity of parameters, the response surface method and multiobjective genetic algorithm are used for optimization analysis to determine the optimal structural dimension parameters of CMG. A CMG topology with 4 inner poles and 17 outer poles is established. Compared with the conventional CMG, the output torque of the proposed CMG is increased by 33.42%. Finally, a prototype was made and a test platform was built. The experimental results show that the transmission ratio of the proposed model is consistent with the theoretical value, the no-load loss is relatively small, and the efficiency is high.

Optimization of coaxial magnetic gear and its application in wave power generation

The application of coaxial magnetic gear (CMG) in wave generator instead of traditional variable speed gearbox can effectively improve torque density and reduce torque ripple. Thus, the operation principle of CMG from the perspective of magnetic field modulation is firstly analyzed in this paper. Then the air gap magnetic fields induced by high-speed and low-speed rotors are studied. And the radial height, inner diameter angle, and outer diameter angle of the modulating pieces (MPs) are optimized by using the combination of response surface method (RSM) and particle swarm optimization (PSO) algorithm to improve the torque transmission capacity of CMG. The CMG is combined with the permanent magnet synchronous machine to get the magnetic-gear permanent magnet synchronous generator (MG-PMSG). The design feasibility of the MG-PMSG is verified from four aspects: static magnetic field analysis, no-load characteristics, load characteristics and load disturbance analysis.

Magnetic gearbox for automotive power transmissions: An innovative industrial technology

Conventional coaxial magnetic gears are structures with permanent magnets, which working principle is equivalent to that of epicyclic gearing. The motion is transferred between different axles, without contact in the rotating elements, by modulating the magnetic field generated by permanent magnets on inner and outer rotors of the machine, exploiting ferromagnetic poles in the middle rotor. The challenge of replacing standard mechanical gears in an automotive powertrain has led to the development of a new technology of paramount importance for the automotive industry which could solve several problems related to classical gears like, e.g. need of lubricant, wearing, vibration, noise, and need of friction material. In this paper a novel topology of magnetic gearbox is proposed. The presented solution is expected to have a higher reliability and efficiency compared to equivalent mechanical gearboxes, allowing the torque transmission from the power source (electrical or thermal) to the wheels, with a certain number of fixed gear ratios. Several topological solutions of magnetic gearbox are proposed, with possible application in different industrial fields. The gearshift phase has been dynamically analysed with an analytical approach and then a magnetic powertrain has been developed in Matlab/Simulink to validate the proposed technology, as alternative to the mechanical one.

Multi-Objective Optimization Analysis of Magnetic Gear With HTS Bulks and Uneven Halbach Arrays

To improve the output torque of coaxial magnetic gears, a novel coaxial magnetic gear (CMG) with high temperature superconducting (HTS) bulks and uneven Halbach arrays is proposed in this paper. The convex structure is used in the middle of inner rotor permanent magnets (PMs). The PMs of the outer rotor are arranged in a low-high-low arrangement, epoxy resin is added between the PMs of outer rotor and the outer iron yoke. At the same time, the HTS bulks replace the epoxy resin to reduce magnetic flux leakage. In addition, according to the sensitivity analysis, the structural parameters can be divided into different levels, the multi-objective optimization analysis is carried out. Finally, the optimal CMG topology with 4 inner and 17 outer pole pairs is established. The results show that the amount of PM is reduced and the output torque is effectively increased by finite element analysis (FEA).

Design and Experimental Testing of a Magnetic Gear for an Electric Aircraft Drivetrain

This paper presents the magnetic, thermal and mechanical design details as well as testing result for a high mass torque density coaxial magnetic gear (MG). The MG was designed for use in an electric aircraft application and has a 12.4:1 gear ratio. The MG was designed to be competitive with a mechanical equivalent aircraft gear and had a calculated total mass torque density of 53 Nm/kg with a rated torque of 229 Nm. The proof-of-principle MG used Garolite support parts, rather than carbon fiber and due to dimensional differences, the tested MG was shown to achieve a 23.5 Nm/kg torque density. The importance of using laminated magnets and the importance of accounting for both parallel and in-plane eddy current losses within the MG is highlighted.

Analysis of Some Design Parameters and Constructive Solutions for Coaxial Magnetic Gears

Abstract This paper presents the torque focused design optimization and analysis of coaxial magnetic gears parameters when implementing some constructive and assembly solutions. A theoretical investigation of several proposed solutions for mounting the permanent magnets on the surfaces of inner and outer rotors is held. The mounting of magnetic pieces on outer and inner rotors is considered as the benchmark models of magnetic gears do not display the actual torque capability provided by their constructed versions. Design, geometry, and assembly of magnetic flux modulator are studied to determine some feasible solutions. The impact of above-mentioned parameters on the torque capability are then studied and calculated with the help of finite element method (FEA) and the results are summarized and presented.

Sliding mode control of an outer-rotor magnetic-gear-integrated motor with a Halbach array

In this paper, the magnetic-gear-integrated motor with a Halbach array is analyzed. The combination of coaxial magnetic gear and permanent magnet synchronous motor (PMSM) replaces the role of mechanical gear in transmission structure and realizes the transmission characteristics of low-speed and high torque. Halbach permanent magnet array has the effect of good unilateral magnetic shielding, which can make the waveform closer to the sine wave. Aiming at the problem that the position sensor limits the control accuracy during the operation of the motor, founded on the analysis of the mathematical model of the magnetic-gear-integrated motor, an improved sliding mode observer is proposed. Also, the sliding mode controller (SMC) replaces the PI regulation in the speed loop to increase the robustness of the system. Lyapunov is utilized to prove the stability of the system, and the simulation is built in MATLAB/ Simulink. A 3.6 kW prototype is manufactured and tested. The feasibility of the sensorless-driven system is proven by simulation and experiments.

Design Aspects of Conical Coaxial Magnetic Gears

In this paper, a new design of a conical coaxial magnetic gear was proposed. Conical magnetic gears are considered a logical link between the radial- and axial-field coaxial designs. The modeling of magnetic torques based on the 3D finite element method was developed. The design parameter variations of the conical coaxial magnetic gear were determined and discussed. The magnetic torque density was calculated and compared with that of a cylindrical coaxial magnetic gear with the same size and materials used. An optimal cone angle based on the air-gap length was proposed. Multistage conical coaxial magnetic gears were proposed as a sequence of coupled rotors with increased torque density and reduced magnetic reluctance. The proposed conical coaxial magnetic gears are more compact in size and suitable for integration with electrical machines and variable transmissions.

Loss Analysis of Magnetic Gear with Slotted in Magnetic Modulation Ring

In order to improve the operation efficiency of coaxial magnetic gear (CMG), in this paper, a CMG model with slotted in magnetic modulation ring is proposed. In this model, the permanent magnets (PMs) of internal and external rotors are distributed in Halbach array, the inner rotor PMs are equally divided into 3 small pieces, and the outer rotor PMs are equally divided into 2 small pieces. At the same time, the static magnetic modulation ring iron blocks are slotted, each iron block has 3 slots, the width of the slot is 0.4°, and the depth of the single side slot is 1mm. Finally, a two-dimensional model is established, and the eddy current loss and iron loss of the model are optimized, compared with the conventional CMG model, it is found that the changed pattern can increase the internal and external output torque by 4% and 4.12%, respectively. The eddy current loss is reduced by 66.57%, and the iron loss is reduced by 8.9%, which significantly improve the operation efficiency of the CMG.