直接驱动XY平台位置域轮廓跟踪控制

针对直接驱动XY平台轮廓误差近似模型建立困难的问题,提出一种提高轮廓跟踪性能的位置域轮廓跟踪控制方法.通过将双轴运动系统等效为主-从运动方式,主动轴(X轴)以位置量作为自变量,将从动轴(Y轴)的运动描述为不同轮廓跟踪要求的X的函数.通过从时域到位置域的一一映射,得到双轴运动系统的位置域动态模型.提出了位置域PD控制策略,主动轴运动以自身为参考产生的位置跟踪误差为零,仅有从动轴的运动跟踪误差影响到了最后的轮廓误差.仿真结果表明,位置域轮廓控制相比时域轮廓控制能够获得更好的跟踪精度.

Democracy on the Road toward the Rule of Law Started from Umbrella Movement

This paper had started its words from the hot current Umbrella Movement in Hongkong, with putting forward the questions that ＂ What is the democracy？ ＂ and ＂ How should the democracy develop？ ＂ . And then, it had reviewed the historical development of the concept of democracy, on that basis, it had explored the socialist democratic system in China and analyzed the dilemmas in the construction of socialist democracy. And it gave the responses to questions in the beginning of the article and explained the reasons in details. At the last, some notes on the construction of democracy in China＇ s journey toward rule of law were written in this article.