Magnetic Gear Research Articles

Design Optimization of an Axial Flux Magnetic Gear by Using Reluctance Network Modeling and Genetic Algorithm

The use of a suitable modeling technique for the optimized design of a magnetic gear is essential to simulate its electromagnetic behavior and to predict its satisfactory performance. This paper presents the design optimization of an axial flux magnetic gear (AFMG) using a two-dimensional (2D) magnetic equivalent circuit model (MEC) and a Multi-objective Genetic Algorithm (MOGA). The proposed MEC model is configured as a meshed reluctance network (RN) with permanent magnet magnetomotive force sources. The non-linearity in the ferromagnetic materials is accounted for by the MEC. The MEC model based on reluctance networks (RN) is considered to be a good compromise between accuracy and computational effort. This new model will allow a faster analysis and design for the AFMG. A multi-objective optimization is carried out to achieve an optimal volume-focused design of the AFMG for future practical applications. The performance of the optimized model is then verified by establishing flux density comparisons with finite element simulations. This study shows that with the combination of an MEC-RN model and a GA for its optimization, a satisfactory accuracy can be achieved compared to that of the finite element analysis (FEA), but with only a fraction of the computational time.

A Review of Magnetic Gear Technologies Used in Mechanical Power Transmission

This paper presents a literature review on magnetic gears, highlighting the advantages of using these technologies for mechanical power transmission applications in wind energy conversion systems and transportation, such as in electric vehicles. Magnetic gear technologies have important advantages over their mechanical counterparts. They can perform the speed change and torque transmission between input and output shafts by a contactless mechanism with a quiet operation and overload protection without the issues associated with conventional mechanical gears. The paper describes the fundamentals and operating principle of the field-modulated magnetic gear topologies and investigates the magnetic torque transmission mechanism. However, despite all the advantages highlighted in different research and development reports, there is still no convincing evidence to show that magnetic gear technologies are an acceptable alternative for industrial applications. The aim of this paper is to summarize previous work on magnetic gears to identify the topologies most suited for mechanical power transmission systems in wind energy conversion systems and electric vehicle applications. These applications will show that research and development of magnetic gear technologies contribute significantly to solutions for sustainable systems, a subject to which our current civilization must pay a lot of attention.

A High Torque and Low Ripple Magnetic Gear with Embedded Permanent Magnet

A High Torque and Low Ripple Magnetic Gear with Embedded Permanent Magnet

Self-powered flow sensing for automobile based on triboelectric nanogenerator with magnetic field modulation mechanism

Automobile flow sensors are critical in ensuring the engine air-fuel ratio, improving fuel efficiency, and reducing pollution. This paper presents a self-powered shaftless turbine intake flow sensor (STIFS) for automobiles consisting of a ball-bearing triboelectric nanogenerator (BB-TENG) and a magnetic field modulation type magnetic gear electromagnetic generator (MG-EMG). The contact electrification between the rolling ball and the outer ring of the BB-TENG generates a periodic electrical signal for flow sensing. In particular, the magnetic gear can improve the BB-TENG signal frequency and MG-EMG output performance. The smoothness of the airflow is improved by designing the shaftless turbine using the computational fluid dynamics (CFD) method, and the start flow of the STIFS is 160 L/min. The sensing sensitivity of the STIFS reaches 0.71 Hz/L·min−1·in the monitoring range of 300–900 L/min, and there is a well linear relationship between frequency and flow rate. In addition, the MG-EMG can generate output voltages and currents of 374 V and 31 mA to power data analysis and transmission modules in real-time. This work presents a novel methodology for self-powered wireless airflow sensing in large-flow pipelines, such as automobile intake pipes.

Design of Quasi-Halbach Permanent-Magnet Vernier Machine for Direct-Drive Urban Vehicle Application

Removing the gearbox from the single-motor configuration of an electric vehicle (EV) would improve motor-to-wheel efficiency by preventing mechanical losses, thus extending the autonomy of the EV. To this end, a permanent-magnet Vernier machine (PMVM) is designed to ensure such operation. This machine avoids the high volume and large pole-pair number of the armature winding since its operating principle resembles that of a synchronous machine with an integrated magnetic gear. Therefore, such a structure achieves low-speed and high-torque operation at standard supply frequencies. From the specification of an urban vehicle, the required specification for direct-drive operation is first determined. On this basis, an initial prototype of a Vernier Machine with permanent magnets in the rotor that can replace the traction part (motor + gearbox) is designed and sized. This first prototype uses radial contiguous surface-mounted magnets and its performance is then analyzed using finite element analysis (FEA), showing a relatively high torque ripple ratio. The rotor magnets are then arranged in a quasi-Halbach configuration and simulations are performed with different stator slot openings and different ratios of the tangential part of the magnet in order to quantify the effect of each of these two quantities in terms of average torque, torque ripples and harmonics of the back-electromotive force at no load. Since the design and optimization of this motor is finite element-assisted, a coupling process between FEA Flux software and Altair HyperStudy is implemented for optimization. This method has the advantages of high accuracy of the magnetic flux densities and electromagnetic torque estimates, and especially the torque ripples. The optimization process leads to a prototype with an average torque value that meets the specification, along with a torque ripple ratio below 5% and a high power factor, while keeping the same amount of magnet and copper.

The basic specifications of magnetic flux modulation gear

The basic specifications of magnetic flux modulation gear

Research and control of a new dual-modulation magnetic gear compound motor for electric vehicles based on a mathematical model and FEA co-simulation

According to the development of the electric vehicle motor drives, a magnetic gear compound motor with small size, lightweight, non-contact, and high-power has a good development prospect in the new energy electric vehicle industry. A new dual-modulation magnetic gear compound motor (DMFMCM) with high torque, low torque ripple, and high mechanical strength is proposed in the paper. The topology and driving principle of DMFMCM are analyzed in this paper, and the finite elements analysis (FEA) is used to compare and analyze the DMFMCM and the conventional magnetic gear compound motor (CMGCM). Furthermore, the mathematical model of DMFMCM is established to achieve the decoupling of the three-phase voltage or current, and the mathematical model and FEA co-simulation is established to ensure the accuracy of the mathematical model. Finally, according to the principle of SVPWM controlled by id = 0, the paper simulates a PI-adjusted three-phase DMFMCM control system model. The result shows that the DMFMCM controlled by SVPWM has high stability, strong anti-interference ability and good speed regulation performance, thus meeting the development of electric vehicles.

Fast Magnetic Field Approximation Method for Simulation of Coaxial Magnetic Gears Using AI

Artificial intelligence and deep learning have been widely used in recent years to explore the possibility of accelerating computation. However, it has very few applications in magnetic field calculation. This article employs a conditional generative adversarial network (cGAN) to approximate the magnetic field of a coaxial magnetic gear and calculate the magnetic torque through postprocessing. The working principle of magnetic field approximation using cGAN and the training process is introduced in this study. We adopted conditional image-to-image translation technology in cGAN and compared different loss functions and residual structures combinations. Then, we found the best combination, which can accelerate convergence, reduce errors, and improve the generator's performance. Numerical experiments have verified the effectiveness of the proposed cGAN, and the average numerical error can be as small as 1%. At the same time, its speedup ratio is as high as 200 compared to the finite element method.

Magnetic field and torque analysis of coaxial magnetic gear using semi-analytical and superposition methods

This paper presents the magnetic flux density and torque calculation of coaxial magnetic gear. We obtained analytical magnetic field solutions produced by permanent magnets based on subdomain method and super position method. Then, the analytical solutions for torque characteristics were obtained. All analytical results were validated with two-dimensional finite element analysis and experimental results.

Load Angle of Flux Modulated Magnetic Gears

Load Angle of Flux Modulated Magnetic Gears

Design and Optimization of Axial Field Flux-Switching Magnetic Gear Composite Motor Based on Varying-Network Magnetic Circuit

Design and Optimization of Axial Field Flux-Switching Magnetic Gear Composite Motor Based on Varying-Network Magnetic Circuit

Corrections to “Design and Optimization of Axial Field Flux-Switching Magnetic Gear Composite Motor Based on Varying-Network Magnetic Circuit”

Corrections to “Design and Optimization of Axial Field Flux-Switching Magnetic Gear Composite Motor Based on Varying-Network Magnetic Circuit”

Coupling Analysis of Multi-physical Fields of Magnetic Gear Motor with Nonuniform Air-gap Halbach Array Magnetization

Coupling Analysis of Multi-physical Fields of Magnetic Gear Motor with Nonuniform Air-gap Halbach Array Magnetization

비정형 물체 파지를 위한 적응형 자석 기어 그리퍼

This paper proposes an adaptive gripper for atypical objects. This gripper is designed to drive three fingers with one motor by applying three adaptive two-joint fingers developed in our previous research. The gripper with a single motor has the advantage of reduced weight, and the non-contact finger can be continuously driven by utilizing the characteristics of the magnetic gear when grasping an atypical object. A prototype of the adaptive gripper was manufactured with a 3-D printed body and link. It was confirmed that the adaptive grasping of the gripper worked in a limited driving torque range in the experiment. The gripper could grasp atypical objects such as tomatoes and oriental melons with torque control. Finally, it was confirmed that the performance of the gripper could be controlled by the torque control and the gap between the magnetic gear.

Determination of Design Parameters Considering Working Harmonic and Irreversible Demagnetization for Flux-Modulated Linear Actuator

This article proposes a design process for a flux modulated (FM) permanent-magnet linear actuator for a five-axis gantry robot system by investigating the parameters affecting working harmonics. A detailed design process using the magnetic gearing effect was developed by considering the magnetic equivalent circuit and finite element analysis models of the FM-linear actuator. Considering natural cooling, the design process includes the effect of irreversible demagnetization when selecting the design parameters. Using the design parameters, a final simulation model was created to check the electromagnetic performance under both no-load and full-load conditions. A prototype was built to validate the results obtained using the proposed analytical model.

Transmission performance of planetary permanent magnet gear with few pole difference

Transmission performance of planetary permanent magnet gear with few pole difference

Fast and efficient simulation of the dynamical response of coaxial magnetic gears through direct analytical torque modelling

Coaxial magnetic gears have been of great interest amongst researchers and the industry since their introduction two decades ago. Although magnetic gears suffer from slippage at high torques and in general have lower torque density compared to their mechanical counterparts, they surpass their performance in terms of attained speeds, versatility, vibration attenuation, backdrivability and efficiency. Increasing the torque density is a major issue in magnetic drivetrains that has been extensively discussed in the literature. However, the calculation of the torque is typically performed through FEA and/or numerical methods, thus increasing the computational cost especially in dynamical simulations where the applied torques at the two rotors have to be calculated at each time step. The objective of this work is to introduce an analytical 2D model for fast and efficient calculation of the applied torques for every rotation angle, geometry configuration and constitutive parameters of the magnets using the Maxwell Stress Tensor. The results obtained from the model were compared against those obtained from FEA. The calculated torques at the inner and outer rotor were in perfect agreement with FEA, however the analytical model was more than two orders of magnitude faster. In addition, an analytical calculation of the torque ripple in coaxial magnetic gear drives is made possible using the proposed model. An investigation of the influence of the modulator ring on stall torque was performed illustrating that there is an optimum length value for the ferromagnetic segment to maximize torque density. Furthermore, the motion equations of the coaxial magnetic gear drive were formulated and a model was developed to simulate the dynamical response of the system without the requirement of torque calculation at each time step that significantly decreases computational cost. The slip effect was investigated and the resulting transmission error was determined.

Analysis and Calculation of the Three-Dimensional Air-Gap Magnetic Field and Electromagnetic Torque of a Multishaft Ring-Plate Magnet Gear

A kind of multishaft ring-plate magnet gear (MRMG) structure is proposed. Because an MRMG has the characteristics of an eccentric permanent magnet gear with a small aspect ratio and large magnetic leakage at the end, there is a large deviation when using traditional 2-D FEM or an analytical method to analyze and calculate field and torque values for an MRMG. In this article, a 3-D mathematical analytical model of the MRMG eccentric air-gap magnetic field and electromagnetic torque is established, which is suitable for computer modeling. First, based on the cylindrical coordinate system of the inner and outer permanent magnet rings, the 3-D analytical models of the air-gap magnetic field of the inner and outer permanent magnet rings are established, respectively, by using the vector magnetic potential method. Then, by analyzing the position relationship between the inner and outer permanent magnet rings and their superposition angles, the radial and tangential air-gap magnetic fields of the inner and outer permanent magnet rings are superimposed according to their included angles, and a 3-D analytical model of the air-gap magnetic field and the electromagnetic torque of an MRMG is established. Because all the calculations are magnetic field integrals along the axial length of the MRMG, the magnetic field’s end effect is included in the established model, and the calculated results are more accurate than those of a 2-D FEM and analytical method (error >13%). A 3-D FEM and static loading experiment show that the model has a good accuracy (error < 2%) with the measured results and finite-element analysis, but the calculation speed of the model is faster than that of the 3-D FEM, which not only greatly shortens the calculation time but is also suitable for computer programming and is easily used to perform the MRMG analysis and optimization of different MRMG structural parameters.

동일한 토크-속도 성능곡선을 만족하는 철도차량 직접구동용 IPMSM과 마그네틱 기어드 모터의 특성 비교 연구

This paper conducted a comparative study on the characteristics of an Interior Permanent Magnet Synchronous Motor (IPMSM) and a Magnetic Gear Motor (MGM) with a 200 kW class direct drive motor (DDM). The IPMSM and MGM for DDM satisfying a given torque-speed performance curve were designed, and it was examined whether the same torque-speed performance curve could be satisfied based on the voltage limiting ellipse of MGM newly derived. In addition, the electromagnetic characteristics and performance of the two motors were analyzed, and a comparative study of the two motors was conducted in various aspects such as current density, power density, and efficiency.

Analytical vibration of middle rotor of coaxial magnetic gear with complicated structure due to holes and screws

Coaxial magnetic gear is a cutting-edge technology introduced a few years ago. Its middle rotor is a rotating steel cylindrical shell with a variable array of holes that are filled by brass screws, hence it is such a complicated structure due to these holes. At first glance, it seems impossible to apply shear deformation theories to this unusual geometry, but for the first time, this article has introduced a novel mathematical methodology that creatively makes this possible. Consequently, an analytical formulation is presented for free vibration of this complicated structure, with no need to finite element software. The final aim is to extract natural frequencies and critical speeds in terms of different parameters. The formulation begins with the first-order shear deformation theory as the displacement field and continues with the Hamilton approach to gain governing equations of motion. Additionally, the effect of an external radial magnetic field is modeled by Maxwell’s relation. In the end, the Galerkin scheme is followed for discretization of the governing equations. This scheme is compared to an older article to guarantee its accuracy. Subsequently, the natural frequencies are estimated in terms of physical parameters of the rotor such as angle and number of holes, hole-thickness to total-thickness ratio, magnetic field and some other parameters. The mode shapes are also depicted for better interoperation of rotor’s behavior. The findings show that unlike geometric parameters (e.g., angle and number of holes), the radial magnetic field does not significantly affect the natural frequency.