Because the mover and stator of a doubly-fed linear motor are both equipped with three-phase windings, the motor enables contactless energy to be transferred from the stator to the mover. Thus, when a doubly-fed linea...Because the mover and stator of a doubly-fed linear motor are both equipped with three-phase windings, the motor enables contactless energy to be transferred from the stator to the mover. Thus, when a doubly-fed linear motor is used in the linear driving system of trains, neither an overhead line nor a third rail is needed. However, the doubly- fed motor will lead to more severe thrust fluctuation than the unilateral motors. In order to overcome this shortcoming, the thrust fluctuation of the doubly-fed motor should be analyzed. In this paper, an expression for motor thrust is derived. It points out that the slot effect caused by the slotted structure is the main reason for the increase of thrust fluctuation. The method of adopting unequal pole pitch and unequal slot numbers per pole per phase of stator and mover, is proposed to weaken the slot effect when designing the motor slot parameters. Three different motor models are simulated by ANSOFT. The proposed method results in a motor thrust fluctuation coefficient of 8.4%, compared to 49.4% for the conventional method. Therefore, the motor＇s thrust fluctuation is effectively suppressed by the proposed method.展开更多
在射频识别RFID(Radio Frequency IDentification)系统中,其关键的问题是如何解决多标签之间的碰撞。动态帧时隙ALOHA(DFSA)算法是常见的防碰撞算法之一。在DFSA算法中,当帧长和标签的个数近似相等时,帧长调整频繁和碰撞时隙数过多,会...在射频识别RFID(Radio Frequency IDentification)系统中,其关键的问题是如何解决多标签之间的碰撞。动态帧时隙ALOHA(DFSA)算法是常见的防碰撞算法之一。在DFSA算法中,当帧长和标签的个数近似相等时,帧长调整频繁和碰撞时隙数过多,会给系统带来更多的功率损耗和更长的识别时间。针对上述问题,提出了一种基于线性回归统计分析的帧长优化改进算法,分析了其性能,并进行仿真。仿真结果表明,改进算法简单,降低了标签碰撞时隙数,减少了帧长的调整次数,有效地减少了系统时延。展开更多
每极分数槽永磁直线电机(PM linear motors,PMLMs)采用端部不重叠的集中绕组,具有绕组端部短、铜耗低、推力密度高等优点,在数控机床、半导体加工等领域应用广泛。针对12槽/11极与12槽/10极的两种PMLMs,阐述了每种电机采用单边型或双边...每极分数槽永磁直线电机(PM linear motors,PMLMs)采用端部不重叠的集中绕组,具有绕组端部短、铜耗低、推力密度高等优点,在数控机床、半导体加工等领域应用广泛。针对12槽/11极与12槽/10极的两种PMLMs,阐述了每种电机采用单边型或双边型、所有齿绕绕组或交替齿绕绕组的4种可行结构,建立了有限元分析模型,分析了平均推力、推力波动与结构参数之间的关系。此外,还重点分析了双边型结构PMLMs在两侧磁极位置错位时的力性能,提出了基于最小推力波动与推力比值的最佳错位位置。通过详细的对比分析,得到了单边型与双边型每极分数槽PMLMs推力波动与推力比值最小的最佳方案,研究结果为该类电机的优化设计及应用提供了参考依据。展开更多
文摘Because the mover and stator of a doubly-fed linear motor are both equipped with three-phase windings, the motor enables contactless energy to be transferred from the stator to the mover. Thus, when a doubly-fed linear motor is used in the linear driving system of trains, neither an overhead line nor a third rail is needed. However, the doubly- fed motor will lead to more severe thrust fluctuation than the unilateral motors. In order to overcome this shortcoming, the thrust fluctuation of the doubly-fed motor should be analyzed. In this paper, an expression for motor thrust is derived. It points out that the slot effect caused by the slotted structure is the main reason for the increase of thrust fluctuation. The method of adopting unequal pole pitch and unequal slot numbers per pole per phase of stator and mover, is proposed to weaken the slot effect when designing the motor slot parameters. Three different motor models are simulated by ANSOFT. The proposed method results in a motor thrust fluctuation coefficient of 8.4%, compared to 49.4% for the conventional method. Therefore, the motor＇s thrust fluctuation is effectively suppressed by the proposed method.
文摘在射频识别RFID(Radio Frequency IDentification)系统中,其关键的问题是如何解决多标签之间的碰撞。动态帧时隙ALOHA(DFSA)算法是常见的防碰撞算法之一。在DFSA算法中,当帧长和标签的个数近似相等时,帧长调整频繁和碰撞时隙数过多,会给系统带来更多的功率损耗和更长的识别时间。针对上述问题,提出了一种基于线性回归统计分析的帧长优化改进算法,分析了其性能,并进行仿真。仿真结果表明,改进算法简单,降低了标签碰撞时隙数,减少了帧长的调整次数,有效地减少了系统时延。
文摘每极分数槽永磁直线电机(PM linear motors,PMLMs)采用端部不重叠的集中绕组,具有绕组端部短、铜耗低、推力密度高等优点,在数控机床、半导体加工等领域应用广泛。针对12槽/11极与12槽/10极的两种PMLMs,阐述了每种电机采用单边型或双边型、所有齿绕绕组或交替齿绕绕组的4种可行结构,建立了有限元分析模型,分析了平均推力、推力波动与结构参数之间的关系。此外,还重点分析了双边型结构PMLMs在两侧磁极位置错位时的力性能,提出了基于最小推力波动与推力比值的最佳错位位置。通过详细的对比分析,得到了单边型与双边型每极分数槽PMLMs推力波动与推力比值最小的最佳方案,研究结果为该类电机的优化设计及应用提供了参考依据。
