提出一种判断过约束机构的新方法，它基于如下的单开链运动相容性准则：若对于主动输入的任意取值，2个单开链始终满足其两端轴间距相等，轴间夹角相同，对应的轴长之差为常量，则此二单开链可构成一个封闭回路，该回路为过约束机构。该法操作简单，其特点是变量间输入输出关系先于过约束性得到。过约束机构的寻找可由局部相容性关系入手找出部分运动学关系，进而逐步得到满足所有相容性关系的过约束性条件与运动输入输出规律。用该法给出了4R过约束机构的寻找方法，同时对一个4R2P机构进行了过约束性判定。%A new method for analyzing overconstrained mechanisms is presented in this paper according to the kinematic compatibility criterion of single-opened-chains(SOCs). This criterion states that if for any value of an active input, two SOCs have the same distances and angles between two ending axes of each SOC, and the difference of axis-lengths corresponding to each hand-side for two SOCs is kept constant, then the two SOCs can be combined together as one closure loop which is an overconstrained mechanism. This method is simple and quite different from other methods because the input-output relationship of variables can be obtained during overconstraint analysis. In order to find overconstrained mechanisms, we can begin with parts of compatibility conditions to obtain some kinematic relationships, so that the input-output law and the overconstraint conditions satisfying all compatibility relationship could be given. With this method, 4R overconstrained mechanisms is proved, and also a 4R2P overconstrained mechanism is determined.
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