In order to improve the torque-output precision of the magnetically suspended reaction flywheel,compensation methods were proposed respectively to attenuate the undesirable torque ripple caused by nonideal back electromotive force waveform and commutation in classical control of brushless direct current motor.The real-time back electromotive force was estimated according to the rotor position and speed in order to obtain the reference current,the pulse width modulation duty cycle was calculated in the torque controller to compensate the torque ripple caused by the nonideal back electromotive force.The theoretical derivation was analyzed,methods of modulation of the non-commutation phase during lowspeed range and modulation of the switching-out phase during high-speed range were presented on the basis of the characteristics respectively.Also,a calculation method of the commutation time was given.The experimental results show that the proposed methods can achieve an effective compensation.%为提高磁悬浮反作用飞轮输出力矩精度,针对传统控制方法下永磁无刷直流电机非理想反电势和换相引起的转矩脉动,分别提出补偿控制策略.非换相期间,根据转速和位置信息,估计实时反电势来获取参考电流,通过设计的力矩控制器直接计算出调制占空比以补偿非理想反电势引起的力矩脉动;分析全转速范围内换相期间转矩波动的特点,分别提出低速区非换相相调制和中高速区间关断相调制的换相转矩脉动抑制策略,并给出换相时间的计算方法.实验表明所提控制方法显著提高了飞轮的输出力矩精度,从而验证了方法的正确性和有效性.
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