Sinusoidal Permanent Magnet Research Articles

Design and analysis of in-wheel motor with sinusoidal permanent magnet shape for electrical vehicles

This paper deals with the design and analysis of a surface-mounted outer rotor in-wheel motor (IWM) with the aim of reducing cogging torque and torque ripple for electric vehicles. The proposed IWM is equipped with axial sinusoidal surface-mounted permanent magnets (PMs), with the purpose of producing sinusoidal air gap flux density distribution, thus to realize sinusoidal back electromotive force (EMF) and smooth electromagnetic torque. To highlight the advantage of the proposed IWM, the conventional IWM with tile-shaped PMs and the IWM with stepwise-shaped PMs are also studied for comparison. The finite element method in the commercial software package is utilized to analyze the performance of the three motors, including the radial flux density of air gap, back EMF, cogging torque, and electromagnetic torque. Through the quantitative comparison, it is found that the proposed IWM greatly reduces the cogging torque, highly improves the sinusoidality of back EMF, and nearly eliminates the torque ripple.

A New High-Speed Dual-Stator Flux Switching Permanent Magnet Machine With Distributed Winding

This article proposes a new axial dual-stator flux-switching permanent magnet (FSPM) machine for high-speed applications. The machine adopts a fractional slot distributed winding, which has a higher winding factor, efficiency, and torque density. First, the high-speed FSPM machine topology and operating principle are introduced. By employing the winding complementarity principle, the unfavorable even harmonics of a single stator in the FSPM machine can be counteracted, resulting in an essentially sinusoidal permanent magnet (PM) flux-linkage as well as effectively reduced cogging torque and torque ripple. Second, based on the 3-D finite element method (FEM), both the no-load and on-load electromagnetic performances are obtained. Compared with the other three FSPM machines, the advantages of the proposed machine are highlighted. Finally, a high-speed FSPM prototype is manufactured and a test platform is built to measure the no-load and on-load performances, which verifies the theoretical analysis and simulated results.

Analytical Average Torque Optimization Method of Parallel Magnetized Surface‐Mounted Permanent‐Magnet Machine with Third‐Order Harmonic Shaping Method

AbstractOn the basis of existing studies presented in literature on optimizing permanent magnet (PM) shaping with third harmonic for the tile‐shaped magnetic poles under radial magnetization, this paper proposes a method for PM shape optimization using third harmonic for bread‐shaped magnetic pole under parallel magnetization. Furthermore, the optimal value of third harmonic that should be injected for achieving maximum torque output of a surface‐mounted permanent‐magnet (SPM) motor under parallel magnetization is obtained. The accuracy of the analytical calculation is verified using the finite element method. Furthermore, electromagnetic properties, including back‐EMF waveform, cogging torque, average torque, and torque ripple of the SPM motor obtained under different PM shaping conditions, i.e., without PM shaping, sinusoidal PM shaping, and sinusoidal PM shaping with third harmonic are compared. The comparison results indicate that injecting the optimal value of third harmonic into the PM being subject to sinusoidal shaping can greatly improve the average torque and power density of the SPM motor without increasing the torque ripple. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Enhanced Generalized Vector Control Strategy for Torque Ripple Mitigation of IPM-Type Brushless DC Motors

Optimal currents with appropriate harmonic components injected into the motor windings can effectively mitigate torque ripple for interior permanent magnet (IPM) type brushless dc motors (BLDCMs). However, existing approaches may fail to accurately inject the optimal currents into motors due to the limited current loop bandwidth. This paper proposes a simple enhanced generalized vector control strategy to mitigate the torque ripple for IPM-type BLDCMs. With the proposed vector control strategy, the control block diagram for IPM-type BLDCMs is as simple as that with traditional vector control for sinusoidal permanent magnet synchronous motors. First, an electromechanical energy conversion voltage (EECV), considering the effects of the non-sinusoidal back-EMF and the rotor salience property, is proposed in αβ -axis. Then, a novel coordinate frame is constructed with the proposed EECV, which is based on the arbitrary reference frame theory. As a result, the currents of IPM-type BLDCMs can be decomposed into two constant components, one being linked to the torque and the other one to the flux linkage. Thus, the bandwidth of current loop with simple proportional integral regulator can be equivalently expanded in the proposed coordinate frame. Finally, comprehensive experiments are conducted in different operation conditions to validate the effectiveness of the proposed vector control strategy.

Magnet shape optimization of five‐phase surface‐mounted permanent magnet machine to improve torque performance based on equivalent permanent magnet method

This paper studies the magnet shape optimization of a five‐phase surface‐mounted permanent magnet (PM) machine to improve its torque performance. First, a sinusoidal PM with third and fifth harmonics (sine + third + fifth PM) is presented to enhance the torque. An equivalent PM method is then proposed to avoid the complicated interface conditions between PM and the air gap, making the derivation of torques with magnet shapes using 2‐D analytical models possible. Besides, the influence of PM edge thickness on torque improvement is considered. Moreover, under the condition that the copper losses of machines with different magnet shapes are kept unchanged, optimal harmonics of sinusoidal PM with third harmonic (sine + third PM) and sine + third + fifth PM are analytically derived. Finite element (FE) analysis is performed to validate the equivalent PM method and analytical results. Finally, machines with sine + third PM, sine + third + fifth PM and conventional (without shaping) PM are comparatively studied using nonlinear FE analysis and the experimental results of machine with sine + third + fifth PM are presented, verifying the effectiveness of the analytical optimization of magnet shape. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Material-Efficient Permanent-Magnet Shape for Torque Pulsation Minimization in SPM Motors for Automotive Applications

This paper focuses on the design and analysis of a novel material-efficient permanent-magnet (PM) shape for surface-mounted PM (SPM) motors used in automotive actuators. Most of such applications require smooth torque with minimum pulsation for an accurate position control. The proposed PM shape is designed to be sinusoidal and symmetrical in the axial direction for minimizing the amount of rare earth magnets as well as for providing balanced axial electromagnetic force, which turns out to obtain better sinusoidal electromotive force, less cogging torque, and, consequently, smooth electromagnetic torque. The contribution of the novel PM shape to motor characteristics is first estimated by 3-D finite-element method, and all of the simulation results are compared with those of SPM motors with two conventional arched PM shapes: one previously reported sinusoidal PM shape and one step skewed PM shape. Finally, some finite-element analysis results are confirmed by experimental results.

Torque Improvement of Five-Phase Surface-Mounted Permanent Magnet Machine Using Third-Order Harmonic

This paper presents optimal third harmonics in both permanent magnet (PM) shaping and current waveform to improve the output torque of five-phase surface-mounted PM (SPM) machines. The optimal value of third harmonic injected into the sinusoidal PM shape and current waveform for maximum torque improvement is analytically derived and validated by both finite element (FE) analyses and experiments. It is found that the optimal third harmonic is 1/6 of the fundamental one for both PM shape and current waveform. For the five-phase SPM machines having rotors without shaping, Sine shaping, or Sine shaping with third harmonic injected, the electromagnetic performance including the back EMF waveform, cogging torque, average torque, torque ripple, copper loss, iron loss, impact on power inverter, and demagnetization withstand capability are compared. It is demonstrated that, although the copper loss and iron loss increase due to additional third harmonic in the winding current and magnet shape, the average torque with optimal third harmonics injected in PM shaping and current waveform can be improved by >30% while the torque ripple and remains similar to that of the one with Sine shaping. In addition, this will reduce the dc bus voltage while maintaining the machine torque density. Furthermore, the machine with Sine and Sine+3rd rotors presents much better demagnetization withstand capability performance than conventional rotor.

Torque Enhancement of Surface-Mounted Permanent Magnet Machine Using Third-Order Harmonic

This work presents a permanent magnet (PM) shaping technique with optimal third harmonic to improve the output torque without deteriorating the torque ripple in surface-mounted PM (SPM) machines. The optimal value of third harmonic injected into the sinusoidal PM shape for maximum torque improvement is analytically derived and confirmed by finite-element analysis. Further, the influence of magnet edge thickness on the airgap field distribution is investigated and utilized to compensate the inter-pole flux leakage and curvature effect. It is found that the optimal third harmonic is 1/6 of the fundamental one. For the SPM machines having rotors without shaping, Sine shaping, Sine shaping with third harmonic injected, the electromagnetic performance, including the back-EMF waveforms, cogging torque, average torque, and torque ripple are compared. It is demonstrated that the average torque in the machine of a Sine shaping with an optimal third harmonic injected can be improved by >9%, while the torque ripple remains similar to that of the one with Sine shaping. Finally, the machines with both conventional (without shaping) and optimal third harmonic PM rotors are prototyped and measured to validate the analyses.

空间光学遥感器扫描控制系统设计

A scanning control system for space optical remote sensors based on the sinusoidal Permanent Magnet Synchronous Motor (PMSM) was explored in this paper. By a control strategy combining composite control with differential negative feedback, the reciprocating motion of a scanning mirror with low velocity and high precision was achieved. The mathematical model of scanning mirror motion was analyzed, and a mathematical model of PMSM under the d-q coordinate system was established. By using the id=0 vector control strategy, the simulation model of the control system based on space vector pulse width modulation was built using the MATLAB/SIMULINK, and the current, speed and the position loop were designed. A simulation and an experiment were performed, the results show that the velocity average error in the simulation has optimized from 1.27% to 0.92% and the steady-state mean angular velocity error has arrived 2.06% when the scanning mirror is at a constant speed steady state after combing control. Theoretical analysis and simulation experiments show that the dynamic characteristics of control system can be improved by the proposed control method, and it shows the advantages of short regulation time, small overshooting and quickly accurate dynamic response.

Using Third Harmonic for Shape Optimization of Flux Density Distribution in Linear Permanent-Magnet Machine

This paper presents a sinusoidal permanent magnet (PM) shaping technique with third harmonic to improve the electromagnetic thrust force in linear slotless PM machines without sacrificing the thrust force ripple. Slotless PM linear machine possesses relatively low thrust force ripple due to the absence of cogging force, compared with slotted topology. However, thrust force ripple of the machine with rectangular PM shape still exists due to nonsinusoidal airgap flux density distribution produced by PMs. Sinusoidal shaping techniques can be used to reduce the thrust force ripple but the average thrust force is reduced as well. Therefore, a simple PM shaping technique with optimal 3rd harmonic is presented to improve the output thrust force but not to increase the thrust force ripple. The sinusoidal plus 3rd harmonic shaping technique is analytically demonstrated together conventional sinusoidal shaping method and verified with finite element method. The results show that the electromagnetic performance can be significantly improved.

Modeling of Novel Permanent Magnet Pole Shape SPM Motor for Reducing Torque Pulsation

This paper deals with the modeling of a novel permanent magnet (PM) pole shape for a surface-mounted permanent magnet (SPM) motor so as to generate sinusoidal back EMF and linear electromagnetic torque. Conventional SPM motors have a square-shaped PM pole structure; therefore, square back EMF is generated along with the torque pulsations. This novel SPM motor has sinusoidal PM pole shape in the axial direction; therefore, sinusoidal back EMF is generated due to the sinusoidal magnetic flux distribution. Sinusoidal back EMF eliminates most of the cogging torque; thus, a linear electromagnetic torque is generated. Square and sinusoidal current excitation is provided as to analyze the electromagnetic torque characteristics of SPM motor models. As compared to square current excitation, sinusoidal current excitation shows better linearity as well as average electromagnetic torque for the novel SPM motor model. 3-D finite element analysis (FEA) is utilized to analyze and compare the back EMF, cogging torque, and electromagnetic torque of conventional and proposed novel PM pole shaped SPM motor models for both square and sinusoidal current excitation.

Application of Direct-Drive Technology in Marine Electric Propulsion

The characteristics of direct-drive technology were briefly analyzed. The superiority of using the direct drive technology in the ship electric propulsion was pointed out. The sinusoidal permanent magnet synchronous motor (PMSM) was analyzed and its control strategy applied in the ship electric propulsion. This technology’s feasibility and advanced was expounded.

Compensation of torque ripple in high performance BLDC motor drives

Brushless DC motor drives (BLDC) are finding expanded use in high performance applications where torque smoothness is essential. The nature of the square-wave current excitation waveforms in BLDC motor drives permits some important system simplifications compared to sinusoidal permanent magnet AC (PMAC) machines. However, it is the simplicity of the BLDC motor drive that is responsible for causing an additional source of ripple torque commonly known as commutation torque to develop. In this paper, a compensation technique for reducing the commutation torque ripple is proposed. With the experimental results, the proposed method demonstrates the effectiveness for a control system using the BLDC motors that requires high speed and accuracy.

Torque and current control of high-speed motion control systems with sinusoidal-PMAC motors

Describes a torque- and current-control application to a commercial motion-control system with sinusoidal permanent magnet ac (PMAC) motors. The control approach is based on maximization of torque-per-amp ratio. The proposed torque controller, in the form of torque feedforward plus proportional-integral (PI)-type torque feedback, utilizes the feedback of nominal torque signal only, a signal that can be readily calculated, online. No torque sensor is required. Through proper design of the desired nominal torque with adaptive control, the proposed torque controller can overcome disturbances due to torque estimation error and model uncertainties. A discrete-time approach is developed for inner-current loop control design. The inner-loop control gains, which are hard to obtain through manual tuning in practice, are determined by a dynamic model-based calculation methodology. Experimental evaluation on a commercial motion control system demonstrates the validity of the proposed approach in high-speed motions.

Modeling, identification, and compensation of pulsating torque in permanent magnet AC motors

Permanent magnet AC motors generate parasitic torque pulsations, owing to several electromagnetic phenomena, such as imperfections in the motor and in the associated power inverter. Excitation of the mechanical resonances on the load side is generally the worst consequence of such disturbances; speed oscillations arise which may dramatically limit the performance in high-precision applications. A compact model of the pulsating torque in sinusoidal permanent magnet motors is presented in this paper, based on a combination of theoretical analysis and experimental identification. Online identification algorithms and a compensation scheme are also outlined. The control scheme autonomously identifies the parameters of the disturbance model through simple closed-loop motion experiments. The compensation is then applied as a modification of the output of the position controller. Experiments carried out on an industrial robot demonstrate the effectiveness of the control scheme in suppressing oscillations, both on the motor and on the load sides.