硬盘驱动器（HDD）用磁性材料

简要介绍了迅猛发展的计算机硬盘驱动器（ＨＤＤ）用的新型磁性材料。它们分别是磁头材料,磁记录材料,永磁材料以及磁流体材料。同时叙述了这些材料在硬盘驱动器中的作用以及未来发展的前景。     

IPM在开关磁阻电机调速系统中的应用

介绍了智能功率模块(TPM)的基本结构及保护功能，同时还介绍了IPM在开关磁阻电机调速系统中的应用。     

汽车汽油蒸汽回收系统的控制方式及维修时的故障判定

对汽油机的空燃比进行闭环控制时,汽油蒸汽回收系统也要使用闭控制方法,汽油蒸汽回收系统中的电磁阀以间歇方式工作,以便确定碳罐清理气流对空燃比造成的影响,并据此控制碳罐清理时气流量的大小,使得发动机空燃比总是处于可调节的范围以内,如果使用专用检测仪检测到与碳罐清理状态有关的参数处于调节范围的极限状态时,预示着汽油蒸汽回收系统可能出现了故障。     

一种基于LabWindows的新型机械臂的设计与实现

针对双平行四边形结构的平面关节机械臂的特点和运动规律,利用LabWindows/CVI开发环境和HY-8021数据采集卡,结合步进电机,实现了机械臂的复位和匀速运动控制。     

频谱分析在建筑设备电机故障检测与诊断中的应用

本文以建筑设备电机为研究对象,总结了电机故障诊断的方法及特点,阐述了 FFT 频谱分析诊断电机故障机理。通过试验模拟电机故障,对电流信号进行了 FFT 频谱分析。分析结果表明,FFT频谱分析法可以实现电机故障的诊断。     

禹门口一级站改扩建工程大机组启动方式比选

通过对山西省禹门口一级站改扩建工程中电机的几种启动方式进行比选,确定该工程选用变频启动方式,并对变频器的工作原理、特点、控制方式等进行了简要介绍,为变频器启动方式的推广应用奠定了基础。     

路基永久变形对水泥混凝土路面的影响分析

采用由室内反复加载三轴试验建立的路基土永久变形预估模型,计算了典型土组路基永久变形的量值。分析表明,随着路基回弹模量的提高,其永久变形也逐渐减小;路基永久变形在空间上呈垂球面形,在模拟计算中,可采用抛物线或正弦曲线进行拟合。将路基永久变形作为初始条件赋予相应节点,建立考虑不均匀支撑条件的路面结构分析模型,并对不同荷位下路面结构的荷载响应和疲劳寿命进行分析。结果表明,路基变形对柔性基层路面荷载应力和疲劳寿命的影响均十分显著,因此柔性基层不适宜用于重交通和特重交通路面中;对于半刚性基层路面,当路基回弹模量达到40 MPa时,路基永久变形对路面荷载应力和疲劳寿命的影响均较弱,因此建议在路面结构设计中可予以忽略。     

双向同步施工差异沉降控制技术的研究

利用有限元分析软件,建立某大厦双向同步施工的仿真模型,考虑周围土体约束和混凝土的时变特性,分析了施工过程中构件间的差异沉降,为工程施工提供了可靠的数据支持。     

Reduction of NRRO in ball bearings for HDD spindle motors

In this paper, it is theoretically and experimentally analyzed that the non-repetitive run-out (NRRO) of a ball bearing is caused by geometrical errors of the inner and outer races and the balls, and the number of balls.

The results are summarized as follows:

(1) As for the geometrical errors of the inner and outer races, it is possible to reduce the NRRO to be less than 1 nm by choosing 12 or 18 number of balls, even if the inner and outer races have a harmonic undulation of less than the 11th order.

(2) The NRRO of a ball bearing with 12 balls is very small even if the geometrical errors of ball bearing parts are large. It was confirmed that 12 was an optimal number of balls for ball bearings used for HDD spindle motors.

     

Dynamic model tracking design for low inertia, high speed permanent magnet ac motors

Permanent magnet ac (PMAC) motors have existed in various configurations for many years. The advent of rare-earth magnets and their associated highly elevated levels of magnetic flux makes the permanent magnet motor attractive for many high performance applications from computer disk drives to all electric racing cars. The use of batteries as a prime storage element carries a cost penalty in terms of the unladen weight of the vehicle. Minimizing this cost function requires the minimum electric motor size and weight to be specified, while still retaining acceptable levels of output torque. This tradeoff can be achieved by applying a technique known as flux weakening which will be investigated in this paper. The technique allows the speed range of a PMAC motor to be greatly increased, giving a constant power range of more than 4:1. A dynamic model reference controller is presented which has advantages in ease of implementation, and is particularly suited to dynamic low inertia applications such as clutchless gear changing in high performance electric vehicles. The benefits of this approach are to maximize the torque speed envelope of the motor, particularly advantageous when considering low inertia operation. The controller is examined experimentally, confirming the predicted performance.