基于实测相电流的永磁同步电机转矩波动阶次来源分析及幅值预测EI北大核心CSCD

由于转子磁场非正弦分布、定子开槽及电流谐波等因素影响,轮毂永磁同步电机输出转矩中存在波动,驱动转矩波动将给轮毂电机驱动车辆带来振动噪声问题。为分析各因素对转矩波动的贡献及影响机理,通过转鼓倒拖试验实测了电机空载反电动势,进而确定了转子磁场分布情况及转子磁通系数;通过电机驱动转鼓试验实测了电机三相负载电流信号,发现电流中存在丰富的谐波成分并确定了谐波幅值及初始相位;考虑转子磁通和相电流谐波解析推导了电磁转矩表达式,分析了转矩波动阶次来源并根据电流谐波幅值和相位规律预测了各阶次幅值大小,进而确定了转子磁通谐波和电流谐波对转矩波动的贡献;通过实测的振动加速度信号间接验证了转矩波动阶次分析及幅值预测的准确性。结合试验和理论准确分析了轮毂电机转矩波动的全貌及其来源,为电动轮系统的振动优化提供了方向。     

基于实测相电流的永磁同步电机转矩波动阶次来源分析及幅值预测

由于转子磁场非正弦分布、定子开槽及电流谐波等因素影响,轮毂永磁同步电机输出转矩中存在波动,驱动转矩波动将给轮毂电机驱动车辆带来振动噪声问题。为分析各因素对转矩波动的贡献及影响机理,通过转鼓倒拖试验实测了电机空载反电动势,进而确定了转子磁场分布情况及转子磁通系数;通过电机驱动转鼓试验实测了电机三相负载电流信号,发现电流中存在丰富的谐波成分并确定了谐波幅值及初始相位;考虑转子磁通和相电流谐波解析推导了电磁转矩表达式,分析了转矩波动阶次来源并根据电流谐波幅值和相位规律预测了各阶次幅值大小,进而确定了转子磁通谐波和电流谐波对转矩波动的贡献;通过实测的振动加速度信号间接验证了转矩波动阶次分析及幅值预测的准确性。结合试验和理论准确分析了轮毂电机转矩波动的全貌及其来源,为电动轮系统的振动优化提供了方向。     

电动车用永磁同步电机非线性扭转振动模型

针对电动车车身阶次振动和车内噪声的主要振源—永磁同步电机的扭转振动问题,首先,利用集中参数法建立了永磁同步电机扭转振动的非线性动力学模型,解析求解了考虑非正弦分布的永磁磁场、定子开槽、时间谐波电流的永磁同步电机电磁转矩,获取了定子铁芯、机壳的刚度和阻尼参数,指出了电磁转矩波动是引起永磁同步电机非线性振动的主要原因。然后,采用状态变量法求得了非线性方程组的解。最后,通过永磁同步电机扭转振动实验验证了本模型的有效性。     

分布式驱动用永磁同步电机电磁转矩的解析计算

针对分布式驱动电动汽车车身阶次振动和车内噪声的主要振源—外转子表贴式永磁同步电机6k阶（ ）转矩波动,提出了一种分布式驱动用永磁同步电机电磁转矩的解析计算方法。基于永磁同步电机磁场畸变,对永磁磁极在均匀气隙中的径向分量进行了傅里叶级数分解,通过磁链、电压的计算,最终得到电磁转矩的解析解,为永磁同步电机的阶次振动与振源识别提供了理论基础。当不考虑电流谐波的影响时,对电磁转矩做了阶次分析,论证了由永磁体磁场谐波引起的电磁转矩波动频率是电源频率的6k倍频。最后,通过有限元计算验证了该解析计算结果。     

考虑时间谐波电流的永磁同步电机电磁噪声阶次特征分析

针对分布式驱动电动汽车主要噪声源-永磁同步电机电磁噪声,通过噪声测试实验测得了电机噪声信号,实验结果表明:电磁噪声具有明显的阶次特征,主要阶次不仅包含了偶数阶、开关频率附近阶次,还包含了大量奇数阶,甚至以往研究中被当做信号毛刺而忽略的分数阶。为解释该实验现象,通过磁势磁导法得到考虑时间谐波电流的气隙磁场分布,应用麦克斯韦张量法获得了电磁径向力波,并沿外转子内表面应用复合柯特斯公式对径向力波积分,求得了具有6阶代数精度的电磁径向集中力,进而应用圆柱壳体理论建立了一种考虑时间谐波电流的永磁同步电机电磁噪声数学预测模型,预测了变频器供电时永磁同步电机电磁噪声的特征阶次:2hi、2hj、2(2μ-1)、(hi±hj)、(2μ-1±hi)、(2μ-1±hj)[hi、hj为时间谐波电流阶次,μ∈N*]。当hi或hj是分数时,电磁噪声将出现分数阶特征频率。经过与实验结果对比,本模型能精确预测和解释永磁同步电机电磁噪声的特征阶次。     

电动轮-悬架系统台架振动特性试验分析

为了说明在实际驱动工况下电动轮-悬架系统的振动特性,进行了电动轮-悬架系统台架振动特性测试试验,测得了电动轮-悬架系统-台架的振动加速度响应,并进行了参数影响因素分析。分析表明,电动轮驱动时,电动轮、台架会出现由电动轮驱动电机引起的比较明显的阶次振动,频率成分主要有与非正弦分布永磁磁场、磁场开槽以及谐波电流有关的电流基频6倍、12倍及6±i/2(i=1,2,3)倍,且间隔均为电流基频一半。影响电动轮驱动电机振动谐频成分以及幅值的主要因素只有转速和负载转矩。转速主要影响频率成分,负载转矩影响振动能量,电动轮驱动电机在高转速、大负载等高负荷运行时高频段转矩波动能量较大。载荷、胎压以及车轮定位参数不影响振动响应的频率成分,对振动能量影响较小,适中的载荷、胎压、主销内倾角以及较小的前束角会减小台架振动。可为电动轮-悬架系统结构设计、使用条件以及电动轮驱动电机控制系统设计提供试验指导。     

基于谐波注入的永磁电机转矩脉动抑制策略研究

为解决多相永磁电机的转矩脉动问题,该文基于解析法、仿真以及实验的方法,提出一种抑制该类电机转矩脉动的方法。该文首先推导适用于任意相电机反电动势谐波和齿槽转矩引起的脉动转矩的通用解析表达式。然后,基于此模型,从控制的角度出发,提出通过采用电流谐波注入以补偿齿槽转矩和反电动势谐波的控制策略,分析所需注入的电流谐波特性的一般表达式。为验证所提出方法的有效性,以一台三相12槽10极表贴式永磁同步电机为例,通过Matlab/Simulink设计同时考虑反电动势谐波和齿槽转矩的电机仿真模型,搭建基于谐波注入的电机控制系统。此外,为进一步验证所提出的方法正确性,文章也进行相应的实验验证。研究结果表明：补偿前后电机的转矩脉动峰峰值从1.5 N·m降低到0.5 N·m,转速波动从±2.5 r/min降低到±0.7 r/min。     

电动车动力传动系机电耦合扭转振动分析与控制

对电动车动力传动系统的机电耦合扭转振动进行分析与控制。利用整车转鼓试验测得稳态工况下的电流信号,分析引发传动系统扭转振动的主要电流激励谐次;基于最大转矩电流比控制方法,结合传动系统机械振动模型,搭建综合考虑机械、电气相互影响的机电耦合模型,进行仿真分析;提出能够减小传动系统扭转振动幅值的电流谐波优化方法,阐述其原理并搭建其控制模块。控制前后的仿真结果表明,电流谐波优化方法可以有针对性的抑制电流的5倍、7倍谐波,减小6倍电流频率的转矩波动,降低传动系统在中高频固有频率处的振动幅值。     

一种可改善传动稳定性的混合励磁型磁齿轮研究

同轴磁齿轮是一种结构新颖的传动装置,在低速大转矩传动领域具有广阔应用前景。针对传统表贴式磁齿轮气隙磁密谐波含量高、转矩脉动大的问题,提出了一种内磁极为偏心表贴式,外磁极为永磁体励磁和电励磁两种磁化方式的同轴式磁齿轮。利用有限元法计算了传统型、开槽未加电流型和开槽加电流型磁齿轮的气隙磁场和电磁转矩,对内、外层气隙磁密的谐波含量进行了分析。仿真结果表明,偏心磁极结构有利于改善内层磁密波形,降低谐波畸变率;增加电流励磁不仅能保证输出转矩,而且能降低转矩脉动。这对提高同轴磁齿轮的传动稳定性具有重要意义。     

包装机驱动控制系统中谐波噪声信号抑制策略

目的为了抑制谐波信号的影响,提取得到更准确的转子位置信息,提高包装机动力系统性能。方法文中提出一种基于滑模观测器、改进广义二阶积分器锁频环、锁相环的无传感器控制方案,并通过Simulink仿真实验验证该方法提取电机转子位置信息的能力。结果该方案能够有效降低反电势信号中的直流谐波分量和5、7次谐波分量,提高了基波信号纯度,降低了转速估计误差,提高了永磁同步电机运作过程中转速稳定性与可靠性。结论在Matlab/Simulink中进行静态实验与动态实验,实验结果验证了文中采用的控制策略对不同阶次谐波噪声信号具有更好的抑制效果,能够提高永磁同步电机转速估计精确度,提高包装机动力系统工作性能。     

高效节能的永磁同步电机混合控制算法

目的 保证永磁同步电机在变速变载时能够快速响应的同时,降低其在稳态时的转矩脉动和开关频率,使永磁同步电机在整个包装过程更加高效节能.方法 分析永磁同步电机的2种控制策略DTC和PIPC的优缺点和共同点,提出在启动、变速和变载过程采用DTC控制策略保证电机的动态响应速度,在稳态时切换到PIPC控制策略,降低电机的转矩脉动和开关损耗.结果 仿真结果表明,2种控制策略能够实现平滑切换,电机动态响应快,抗干扰能力强,稳态时转矩脉动小、开关频率低;相比DTC,在空载、轻载和重载时转矩脉动分别减小了30％,12.5％和2.4％,开关频率降低了约45％;相比PIPC,响应速度提高了约7％.结论 相比单一的控制策略,DTC_PIPC混合控制算法融合了2种控制策略的优点,使电机在整个运行过程既能快速应对各种突变情况,又能降低其在稳态运行时的转矩脉动和开关频率.     

永磁无刷直流电动机位置传感器精度对脉动转矩抑制效果的影响研究

采用峰谷互补方法对永磁无刷直流电动机的脉动转矩进行抑制时,2台电机脉动转矩波形的对称性和正弦性与抑制效果密切相关,而位置传感器的精度直接影响电机脉动转矩的波形特性。基于此,首先通过实验测定了2种位置传感器在电机运行时其输出信号的相位差、占空比和响应速度,并进行了分析。然后搭建实验平台测定了电机在2种位置传感器工况下脉动转矩的对称性和正弦性。最后,对比了2种位置传感器运行时电机脉动转矩的抑制效果,结果表明在光栅位置传感器工况运行时电机脉动转矩的抑制效果约提升30%。     

Dynamical magnetoelectric effects in multiferroic oxides

Multiferroics with coexistent ferroelectric and magnetic orders can provide an interesting laboratory to test unprecedented magnetoelectric (ME) responses and their possible applications. One such example is the dynamical and/or resonant coupling between magnetic and electric dipoles in a solid. As examples of such dynamical ME effects, (i)?the multiferroic domain wall dynamics and (ii)?the electric dipole active magnetic responses are discussed with an overview of recent experimental observations.     

Torque ripple reduction in direct torque controlled five-phase induction motor using modified five-level torque comparator

The five-phase induction motor inherently has the minimal torque ripple. However, when it is controlled by direct torque control (DTC) technique, the torque ripple increases due to the presence of a hysteresis torque comparator. The classical five-level torque comparator is presented in the previous literatures to control the torque ripple. However, this comparator has the drawback of wrong selection of zero voltage vectors inside the inner band on the positive side of the comparator, which enables the torque ripple to increase and dc-link utilization to decrease. In this paper, in order to reduce the torque ripple and to increase the dc-link utilization, a modified five-level torque comparator is proposed, which selects either medium or small voltage vectors instead of zero voltage vectors inside the inner band on the positive side of the comparator. In addition to torque ripple reduction and improvement in dc-link utilization, the proposed comparator significantly improves the quality of phase current. All the available 32 voltage vectors are selected through the proposed five-level torque comparator based on the location of x–y stator flux in order to eliminate the x–y stator flux so as to obtain reduced distortion in the phase current. By employing all the available voltage vectors, the freedom of utilization of all voltage vectors in the five-phase induction motor DTC drive is availed. The proposed five-level torque comparator is compared to its classical five-level counterpart through simulation and experimental results in order to validate the proposed DTC strategy.     

Evolution of local to global minimum torque ripples of direct torque control for induction motor drives

This study discusses the evolution of the local minimum to global minimum torque ripples of the direct torque control of induction motor drives. This study will show that the previous minimum torque ripple design is not the global minimum but a local minimum root-mean-square (RMS) torque ripple. To show this, the study finds the optimal initial torque error, which makes the global minimum torque ripple, and then the related global minimum RMS torque ripple. Moreover, after finding the optimal initial torque error and its related global minimum RMS torque ripple, this study derives the evolution of the initial torque ripple error, under the local minimum RMS torque ripple control strategy. Furthermore, this study also proves that under the local minimum RMS torque ripple control strategy, the local minimum torque ripple will converge to the global minimum value.     

永磁无刷直流电动机换相脉动转矩及抑制方法

通过分析永磁无刷直流电动机的换相过程,得到了电动机绕组电流换相产生的脉动转矩表达式。为了验证理论分析的正确性,首先对电流换相产生的脉动转矩及相关特性进行了仿真,然后采用永磁旋转角加速度传感器对电动机轴上的脉动转矩进行了实际测量,验证了电机输出转矩中的脉动转矩分量的客观存在性及相关特性。针对脉动转矩,提出了一种基于峰谷互补的抑制方法,并建立了对应的实验平台开展了实验研究,理论分析和实验测量取得了一致的结果,从而证明了该抑制方法的正确性。     

Ripple compensation for torque sensors built into harmonic drives

Harmonic drives include a mechanically flexible component which transmits load torque, and therefore, a torque sensor can be built into harmonic drives by cementing strain gages on a flexible component of the gear. However, a periodic sensing error called ripple is generated by deformation of a flexible component during the gear operation. The ripple signal cannot be sufficiently compensated by pairs of strain gages that produce opposite phase signals, because the strain gages cannot be exactly positioned on the desired locations. In this paper, we present a method to compensate the ripple by a new approach of tuning the ripple amplitudes for separate strain gages. The ripple, caused by positioning errors of the strain gages, can be perfectly compensated, and, therefore, the requirement for accurate strain gage positioning is reduced. The method does not need any online calculations, and consequently, the torque signal is not delayed. The minimum number of strain gages needed to compensate a given number of frequency components of a ripple is derived. Some experimental results are shown     

Analytical Solution of Air-Gap Field in Permanent-Magnet Motors Taking Into Account the Effect of Pole Transition Over Slots

We present an analytical method to study magnetic fields in permanent-magnet brushless motors, taking into consideration the effect of stator slotting. Our attention concentrates particularly on the instantaneous field distribution in the slot regions where the magnet pole transition passes over the slot opening. The accuracy in the flux density vector distribution in such regions plays a critical role in the prediction of the magnetic forces, i.e., the cogging torque and unbalanced magnetic pull. However, the currently available analytical solutions for calculating air-gap fields in permanent magnet motors can estimate only the distribution of the flux density component in the radial direction. Magnetic field and forces computed by the new analytical method agree well with those obtained by the finite-element method. The analytical method provides a useful tool for design and optimization of permanent-magnet motors.