机构公共约束辨识及自由度计算“拆闭副法”

THE IDENTIFICATION OF GENERAL CONSTRAINT OF MECHANISM AND "SEPARATED-CLOSED PAIR METHOD" IN COMPUTING FREEDOM DEGREE

本文论证了闭环机构公共约束m_i与开环机构末杆约束m′_i的差异,提出关系式:m_i=m′_i+f′_i。澄清长期以来在机构自由度计算中关于公共约束的疑难。指出И·И·Артоболевский统一结构公式中的m_i,若定义为开环末杆约束m′_i,则在自由度计算中,运动副的级有确定的统一定义。阿氏公式与F·Freudenstein公式等效。作者建议取А·П·Мальищев型修正公式:W=6n-sum from k=1kp_k+sum from i=1 m_i作为统一结构公式;并提出确定末杆约束的拆闭副法;指出应用刚体运动分解原理考察各运动副对末杆产生的独立运动时,必须考虑末杆的约束条件。文中列举若干计算例题,并与常用计算方法进行对比分析。

This paper deals with the difference between the general constraint of closed- loop mechanism and end link constraint of open-loop mechanism. An equation has been constituted that can clarify the knotty problem about general constraint in computing the freedom degree of mechanism. It is pointed out that the class of kipematic pairs has its definite definition if the general constraint which is in the integrate equation by E. E. Artobolefski is defined as end link constraint of open- loop. The writer proposes that modified equation by A. P. Marbishef be taken as the integrate construction equation. A separated-closed-pair method has been used for determining end link constraint. It is pointed out that the constraint conditions must be considered in defining end link constraint and analysing the independent motion on end link which is caused by kinematic pairs ih mechanism. This paper has also given some examples of computing freedom degree and made a comparison with the classical method.