换相期间无刷直流电机转矩脉动的抑制策略

无刷直流电机转矩脉动抑制方法综述

无刷直流电机转矩脉动抑制方法综述周杰，侯燕（河南工业大学电气工程学院，450007）摘要：为扩大无刷直流电机在精度较高的伺服系统中的应用，必须尽量减小其转矩脉动。详细论述了无刷直流电机各种有效的转矩脉动抑制方法，并进行分类归纳。关键词：无刷直流电机；转矩脉动；综述中图分类号：TM33 文献标识码：B 文章编号：1004-0420(2007)06-0005-04 The review on torque ripple minimization of brushless DC motors ZHOU Jie，HOU Yan (College of Electrical Engineering，Henan University of Technology，450007) Abstract：To enlarge the application of brushless DC motor in higher accurateness servos，the torque ripple of brushless DC motor must be minimized. Aiming at the torque ripple attenuation of brushless DC motor，many efficient methods were discussed and classified in detail. Key words：brushless DC motor; torque ripple; review 0 引言近年来,无刷直流电机(BLDCM)以其体积小、结构简单、功率密度高、输出转矩大、动态性能好等特点而得到了广泛应用[1]，尤其是在机器人、精密电子仪器与设备等对电机性能、控制精度要求较高的场合和领域，其应用和研究更是受到普遍重视。目前，无刷直流电机最突出的问题就是具有转矩脉动，转矩脉动会直接降低电力传动系统控制特性和驱动

齿槽转矩脉动

齿槽转矩脉动齿槽转矩是由转子的永磁体磁场同定子铁心的齿槽相互作用，在圆周方向产生的转矩。此转矩与定子的电流无关，它总是试图将转子定位在某些位置。在变速驱动中，当转矩频率与定子或转子的机械共振频率一致时，齿槽转矩产生的振动和噪声将被放大。齿槽转矩的存在同样影响了电机在速度控制系统中的低速性能，和位置控制系统中的高精度定位。解决齿槽转矩脉动问题的方法主要集中在电机本体的优化设计上。（1）斜槽法定子斜槽或转子斜极是抑制齿槽转矩脉动最有效且应用广泛的方法之一，该方法主要用于定子槽数较多且轴向较长的电机。实践表明，采用斜槽角度为10°时，齿槽转矩的基波转矩幅值相当于直槽时的90％，3次谐波幅值相当于直槽时的30％，5次谐波幅值相当于直槽时的19％。值得注意的是，为产生恒定的电磁转矩，反电动势波形必须是平顶宽度大于120°的理想梯形波，而斜槽或斜极引起的绕组反电动势的正弦化将会增大电磁转矩纹波。因此，选择合适的斜槽角度是有效抑制齿槽转矩脉动的关键。（2）分数槽法该方法可以提高齿槽转矩基波的频率，使齿槽转矩脉动量明显减少。但是，采用了分数槽后，各极下绕组分布不对称，从而使电机的有效转矩分量部分被抵消，电机的平均转矩也会因此而相应减小。（3）磁性槽楔法采用磁性槽楔法就是在电机的定子槽口上涂压一层磁性槽泥，固化后形成具有一定导磁性能的槽楔。磁性槽楔减少了定子槽开口的影响，使定子与转子间的气隙磁导分布更加均匀，从而减少由于齿槽效应而引起的转矩脉动。由于磁性槽楔材料的导磁性能不是很好，因而对于转矩脉动的削弱程度有限。（4）闭口槽法闭口槽即定子槽不开口，槽口材料与齿部材料相同。因槽口的导磁性能较好，所以闭口槽比磁性槽楔能更有效地消除转矩脉动。但采用闭口槽，给绕组嵌线带来极大不便，同时也会＇大大增加槽漏抗，增大电路的时间常数，从而影响电机控制系统的动态特性。（5）无齿槽绕组为了消除齿槽转矩脉动，可采用无槽绕组的永磁无刷直流电机，这种结构的电机定子可使用非导磁铁心的无齿槽空心杯定子结构（见图），能够彻底消除了齿槽转矩脉动的影响；但绕组电感显著减小，一般只有几μH到几十μH，因此定子电流中的PWM分量非常明显。

无刷直流电机PWM调制方式与转矩脉动关系研究

无刷直流电机PWM 调制方式与转矩脉动关系研究收稿日期:2005-04-28 航空科学基金项目(项目编号:04F 53036) 齐　蓉,周素莹,林　辉,陈　明 (西北工业大学,西安　710072) 摘　要:针对无刷直流电机的双斩和四种单斩PW M 调制方式,分析调制方式对电机稳态转矩脉动的影响,建立稳态及换向过程中电机相电流及电磁转矩的数学模型。基于M atlab 无刷直流电机的仿真模型,研究换向转矩脉动与各种单斩P WM 调制方式的关系。关键词:无刷直流电动机;转矩脉动;仿真;脉宽调制;数学模型中图分类号:T M 361 文献标识码:A 文章编号:1001-6848(2006)01-0058-04 The Relation Between Torque Ripples and PWM Modes of Brushless DC Motor Q I Ro ng ,ZHOU Su-ying ,LIN Hui,CHEN Ming (N or thwester n Po ly technical U niv ersit y,Xi'an 710072,China) ABSTRACT :T his paper analy zes the differ ent PW M modes (sing le cho p P WM m odes and do uble chop PW M modes )influence on the static to r que ripple in Br ushless DC mo tor (BLD CM )co ntro l sy st em .T he ma thematic models o f phase curr ent and electr omag netic tor que ar e derived.Based on M atlab BL DCM modules,the r elation between fo ur PW M modes(H pw m -L o n,H o n-L pw m,on pwm ,pw m on )and co mmutation tor que ripples a re discussed. KEY WORDS :Br ushless DC M ot or ;T o r que ripples ;Simulatio n ;PW M ;M athematic mo dels 0　引　言无刷直流电动机(BLDCM )由于转矩脉动较大地限制了其在高精度伺服系统中的进一步应用。因此,分析其转矩脉动产生的原因及过程,寻找抑制转矩脉动的解决办法成为提高BLDCM 伺服性能的关键。 PWM 调制方式通常分为双斩和单斩两大类型。换相转矩脉动及稳态转矩脉动都与PWM 调制方式有关[1-4]。由于BLDCM 相电感的存在使电机换相时产生换相延时,形成电机换向过程中的转矩脉动[5] ,称为换向转矩脉动。本文针对双斩及H pw m -L o n 、H on-L pw m 、on pw m 和pw m on 四种单斩PWM 调制方式,研究电机稳态和换向时的电流和电磁转矩,分析转矩脉动产生的过程,比较各种PWM 调制方式对转矩脉动的影响。 1　PWM 调制方式对稳态电流和转矩的影响分析 (a )三相六状态 (b ) 双斩调制 (c)H pw m-L o n (d)H on-L pw m (e )o n pwm (f )pw m on 图1　P WM 调制方式的输出波形当无刷直流电动机反电势为梯形波时,系统采用二二导通,三相六状态的120°导通方式如图1(a)所示,双斩调制方式如图1(b )所示。四种单斩PWM — 58—

方波无刷直流电机转矩脉动分析

方波无刷直流电机转矩脉动分析作者：中国中铁电气化局集团第二工程有限公司李庆 [专家点评] 引言永磁方波无刷直流电动机具有体积小、重量轻、出力大、控制简单和调速方便等优点，被广泛应用于军事、工业和家电等各行业。但是，方波无刷直流电机转矩脉动大，限制了它在一些场合的应用。转矩脉动主要是由于电磁因素引起的，本文分析了无刷直流电动机转矩脉动的成因，并从系统的观点提出改善转矩脉动的措施。方波无刷直流电机转矩脉动成因[2] 永磁无刷直流电动机的气隙磁场为方波，相应的逆变装置采用二二导通模式，以保证定子电流波形与气隙磁场波形一致，这样电机转矩脉动最小，几乎为零。但是现实中做到定子电流波形与气隙磁场波形完全一致是不可能的，同时由于电机本身存在定子绕组的换流问题，这就带来了转矩的脉动。从转矩公式 (1) 式中：t e为转矩；为相反电；为相电流；ω角速度；从式中可以看出，转矩脉动主要与定子电流和气隙磁场有关。定子电流对转矩脉动的影响控制逆变装置目的就是调整电流，使之尽量接近理想的方波波形，但是由于定子绕组存在电感，使得定子中的电流上升和下降都有个过程，使得定子电流达不到理想方波波形，导致了转矩的脉动。同时由于斩波频率的限制，非换相期间电流的脉动也带来的精度允许范围之内的转矩脉动。气隙磁场对转矩脉动的影响电机气隙磁场在设计时是梯形波磁场，但是由于机械加工制造等方面的影响，使得气隙磁场达不到理想的梯形波形，同时由于定子齿槽的存在使得气隙磁场有脉动[1]；当电机带负载运行时，定子磁场与转子磁场相互作用，有电枢反应，使得气隙磁场产生畸变，偏离理想梯形波，这也带来了转矩的脉动。抑制转矩脉动的措施为了抑制转矩脉动主要从三方面来采取措施：（1）从主回路角度，尽量采用高频器件，提高谐波次数，减少谐波转矩脉动；（2）从控制的角度，采用最佳的逆变器控制模式，尽量增加有效电磁转矩，采用合适的控制方法抑制换流带来的电流脉动导致的转矩脉动；

转矩脉动抑制

International Journal of Automotive Technology , Vol. 12, No. 2, pp. 291?297 (2011)DOI 10.1007/s12239?011?0034?8 Copyright ?2011KSAE 1229?9138/2011/057?16 291 TORQUE RIPPLE MINIMIZA TION CONTROL OF PERMANENT MAGNET SYNCHRONOUS MOTORS FOR EPS APPLICA TIONS G . H. LEE 1), W. C. CHOI 1), S. I. KIM 2), S. O. KWON 2) and J. P . HONG 2)* 1) Graduate School of Automotive Engineering, Kookmin University, Seoul 136-702, Korea 2) Department of Automotive Engineering, Hanyang University, Seoul 133-791, Korea (Received 18 February 2009; Revised 9 August 2010) ABSTRACT ?This paper identifies a control method used to reduce torque ripple of a permanent magnet synchronous motor (PMSM) for an electric power steering (EPS) system. NVH (Noise Vibration Harshness) is important for safe and convenient driving. Vibration caused by motor torque is a problem in column type EPS systems. Maintaining a very low torque ripple is one solution that allows for smoother steering. Theoretically, it is possible to design and drive the motor without torque ripple.However, in reality, a PMSM system torque ripple is caused by the motor itself (saturation in the iron core and EMF distortion)and the imperfect driver. This paper analyzes torque ripple of a PMSM system, and an advanced PMSM control method for the column typed EPS system is presented. Results of the analysis indicate that the compensation current is needed in order to minimize torque ripple when a PMSM is driven. KEY WORDS :Electric power steering, Magnetic saturation, PMSM, Torque ripple, Deadtime, EMF distortion 1. INTRODUCTION Research is being performed to improve the fuel efficiency of vehicles. One of the main areas of focus is on the steering of auxiliary equipment. Electric Power Steering (EPS) is receiving more attention than Hydraulic Power Steering (HYPS). Electric power steering (EPS) is a system that supplies motor power directly to the steering to assist steering torque while HYPS uses an oil pump that is driven by the engine (Shimizu and Kawai, 1991). A permanent magnet synchronous motor (PMSM) has been used to improve the performance of EPS. Since a PMSM has many advantages, such as high efficiency and high torque per rotor volume, it is especially suitable for automotive applications in which space and energy savings are critical (Miyoshi et al ., 2005). In a column type EPS system, the PMSM is linked to the steering shaft via a reduction gear. This connection transfers the motor vibration and torque fluctuation directly through the steering wheel to the hands of the driver (Zhang et al .,2008). For this reason, only the ripple between one and three percent of rated torque is permitted. Several technical papers have presented a motor design andcontrol technique to reduce cogging torque and torque pulsation (Islam et al ., 2005; Mattavelli et al ., 2005; Bianchi et al ., 2002; Lee et al ., 2008). However, this paper discusses an estimation method of compensation current for suppress-ing torque ripple caused by a PMSM (Lee et al ., 2008).In an EPS application, the magnetic saturation in the stator core and distortion of EMF is inevitable due to spatial and cost limitations(Lee, 2010). Imperfections of a low voltage inverter for EPS can be severe. This paper also analyzes torque ripple caused by the motor, deadtime effects, and current offset problems of the PMSM driver.The harmonic current distribution is calculated using finite element analysis, and the effective dead time compensation method is proposed. 2. TORQUE RIPPLE OF PMSM 2.1. Torque Ripple of PMSM for the EPS Figure 1 indicates a fabricated PMSM for the column type EPS system. The rotor configuration was skewed to reduce cogging torque. Segment type and ring type rotors are used for the purpose of this research. The specifications for a PMSM are listed in Table 1. Cogging torque and total harmonic distortion (THD) of a back-EMF required in the motor are less than 0.02 Nm and 0.7% respectively. If the rotor of a SPMSM is composed of segment-type permanent magnets, there is relatively low THD in the back-EMF (0.7%). A ring-type magnet has a higher THD in the back-EMF (2.3%) and an acceptable level of productivity.The torque waveforms of segment and ring magnets are shown in Figure 2. In order to measure torque ripple accurately, the motor is driven at 10 rpm, and input current is controlled with a THD less than 0.5%. As the magnetic torque increases, the electric frequency increases by a *Corresponding author . e-mail: hongjp@hanyang.ac.kr