In the proposed technique the bemf waveform of bldcm need to be measured in advance at first , through computer simulation and frame transformation , the optimum q - axis current command is achieved . in order to minimize the torque ripple , the d and 0 - axis current command should be zero . furthermore , through reference frame transformation from dqo - axis to abc - axis , we can get the optimum current command in static abc reference frame 在这种控制方法中首先测量出电机的实际反电动势波形，然后通过计算机拟合和坐标变换，求得产生恒定电磁转矩所需的q轴电流，令i _ d ~ * = i _ 0 ~ * = 0 ，通过坐标变换，得到三相静止坐标系a - b - c下的参考电流i _ a ~ * , i _ b ~ * , i _ c ~ * ，利用电流滞环控制来产生pwm信号，由于这种控制方法中电流不会突变，从而可以较好的抑制转矩脉动。
For the bldcm which has a general crest width of the back - emf waveform , two kinds of torque ripple conditions when drived by sine - wave current as well as by square - wave current are deduced based on the mathematical models . in addition , a comparison is carried out between these two conditions , which indicates that sinusoidal current driving is more favorable to minimizing the torque ripple when the crest width of the back - emf waveform is less than a certain value 阐述了抑制齿槽转矩措施对反电动势波形的影响，利用无刷直流电机的数学模型推导并比较了任意平顶宽度梯形波反电动势在正弦波和矩形波两种电流驱动下的电磁转矩脉动情况，得出在梯形波平顶宽度减小到一定数值后采用正弦电流驱动更有利于减小电磁转矩脉动。
The thesis first explains the basic running principle and the characteristic of the direct torque control ( dtc ) , and presents the arithmetic model of the three - phase asynchronous motor , as well as its basic equation of voltage and flux . the knowledge about dsp is simply introduced . the basic principle and the characteristic of fuzzy control and the design method of fuzzy logic controller are also introduced 本文首先论述了三相异步电动机直接转矩控制系统的基本工作原理及特点，介绍了三相异步电动机的数学模型及其电压、磁链方程，较详细地论述了直接转矩控制的控制思想：基于定子坐标的定子磁链、电磁转矩观测；电压空间矢量的调节作用。
