【摘要】 本文通过对机械ＣＡＤ 系统的关键技术的约束求解方法及其优缺点的分析， 比较了国内外各个著名机械ＣＡＤ 系统所采用的约束求解方法， 指出变量几何技术是机械ＣＡＤ 约束求解的主流技术。本文最后指出统一的二维和三维求解核心是机械ＣＡＤ 系统约束求解的发展趋势。更多还原

【Abstract】 This article compares method of restrain explanation which is adopted by all famous machinery CAD system in domestic and foreign countries after analysiing the advantage and disadvantage of the restrain explanation in CAD system. Moreover, the article also points that the variable geometry technology is the essential aspect technology of restrain explanation in CAD system. The article finally pointsout that the explanation core of unitary two-dimension and three-dimension is the development tendency of restrains explanation in machinery CAD system.更多还原