errors, a model is developed to analyze load distribution of ball screw with errors in various load conditions are theoretically investigated. Negative errors makes the load on ball or guiding grooves in corresponding position smaller, even there is no contact in the position when the negative errors reaches certain value. Positive error makes the load bigger. If error heights are assumed to be normally distribution random, the load distribution without error is average value of that in random-error contact. It is valuable for equilibrating load distribution to correct nut groove. The simulation results show that model proposed in this paper is significant to study characteristics of ball screw with regard of errors.

本文提出了计算表面电机气隙磁通量密度分布的分析方法。首先，建立了表面电机磁场的分析模型，给出了磁标量位的拉普拉斯方程以及一系列边界条件。然后用分离变量法获得了永磁体在气隙中产生的磁场强度和磁通量密度的分析表达式。最后将分析结果与实验结果进行对比，证明了分析方法的正确性。为进行表面电机对比研究、优化设计和机械动力学建模提供了基础。

A simple approach of compensating friction error of high-precision tablesis proposed in this paper. On the basis of accurate prediction of the magnitude of thefriction error and the place where it occurs, first a compensator is constructed whichconsists of an online friction error prediction model and the rectangular compensationcurves regarded as the compensation pulses. Then by carrying out several times ofoptimal compensation experiments, the parameters describing the rectangular compensation curve at certain positions can be obtained. Finally the optimal parameters of the rectangular compensation curve at any position can be determined by interpolation and approximation approach. It has been shown that the method of compensating friction error proposed in this paper can be applied to effectively compensate the friction error for any circular motions of high-precision tables.

针对磁悬浮精密定位平台的运动稳定性问题，设计了一种新型六自由度磁悬浮精密定位平台。该平台采用十二个空心电磁线圈做定子、三十六块永磁体做动子，悬浮部分与驱动部分相互独立，很好地解决了电磁线圈铁心引起的非线性以及悬浮与驱动单元之间的相互耦合问题。采用Lorentz定律，分析了永磁体长度、线圈电流和悬浮高度对悬浮稳定性的影响，确定了平台的悬浮平衡位置。建立平台在平衡位置附近的悬浮数学模型并进行了动态响应仿真研究。结果表明该磁悬浮精密定位平台在悬浮电流为2A，悬浮高度为0.5mm时可以稳定悬浮，因此可应用于需要超精密定位和超洁净环境的半导体光刻装置中。