机械工程学报 >

2018 , Vol. 54 >Issue 5: 74 - 83

DOI: https://doi.org/10.3901/JME.2018.05.074

机构学及机器人

机构自由度和构件自由度的关系及本质区别

  • 牟德君 ,
  • 张一同 ,
  • 张兴
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  • 1. 燕山大学河北省并联机器人与机电系统实验室 秦皇岛 066004;
    2. 燕山大学先进锻压成型技术与科学教育部重点实验室 秦皇岛 066004;
    3. 燕山大学工业计算机控制工程河北省重点实验室 秦皇岛 066004
牟德君,女,1967年出生,副教授。主要研究方向为并联机器人机构学理论及应用。E-mail:djmu@ysu.edu.cn

收稿日期: 2016-12-14

  修回日期: 2017-07-06

  网络出版日期: 2018-03-05

基金资助

河北省自然科学基金资助项目（E2011203193）。

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Relations between DOF of Mechanism and DOF of Links and Their Essential Differences

  • MU Dejun ,
  • ZHANG Yitong ,
  • ZHANG Xing
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  • 1. Key Lab of Parallel Robot and Mechatronic System, Yanshan University, Qinhuangdao 066004;
    2. Key Lab of Advanced Forging & Stamping Technology and Science of Ministry of National Education, Yanshan University, Qinhuangdao 066004;
    3. Key Lab of Industrial Computer Control Engineering of Hebei Province, Yanshan University, Qinhuangdao 066004

Received date: 2016-12-14

  Revised date: 2017-07-06

  Online published: 2018-03-05

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摘要

为了避免产生机构自由度和构件自由度两个基本概念的混淆，对它们的本质属性和区别进行了详细的讨论。用广义杆组和虚拟环路的概念，给出了单环路和多环路中任意选定构件的自由度计算方法。通过对平面单环7R机构、滚子从动件凸轮机构、不同自由度的Sarrus机构、2-3RC等典型机构的分析，按机构自由度和构件自由度的关系，把机构分成三类：第一类是机构自由度为1的机构，机构自由度等于所有构件自由度；第二类是机构自由度等于构件最大自由度的机构；第三类是机构自由度大于构件最大自由度的机构。分析结果表明，构件（包括输出构件）自由度是独立位移参数的数目，具有运动形式性质。而机构自由度是使机构所有构件都具有确定位置的全部独立参数的数目，仅仅是一个自然数，没有运动性质可言，机构的自由度与输出构件的选择无关。机构自由度是反映机构整体性能的一个属性，构件自由度反映的是机构局部中某个构件性能的一个属性，两者有着本质区别，在使用这两个概念时要严格区分，不能混为一谈。

关键词： 机构自由度; 构件自由度; 杆组自由度; 输出构件自由度

本文引用格式

牟德君 , 张一同 , 张兴 . 机构自由度和构件自由度的关系及本质区别[J]. 机械工程学报, 2018 , 54(5) : 74 -83 . DOI: 10.3901/JME.2018.05.074

Abstract

The essential difference of the basic conceptions between the DOF of mechanism and the DOF of links are discussed in the paper to avoid the confusion about the DOF of mechanism and the DOF of links. On the basis of the concepts of general link groups and virtual loops, the method is given to calculate the DOF of any selected link in single-loop mechanism or multi-loop mechanisms. The examples are the planar single loop mechanism with 7R, roller-follower cam mechanism, Sarrus mechanisms with different DOF and 2-3RC mechanism etc. According to the relationship between the DOF of mechanism and the DOF of all links, the mechanisms are divided into three types. The first-class is those mechanisms whose DOFs equal 1. The DOF of mechanisms equal DOF of each link. The second-class is those mechanisms whose DOFs equal the maximum DOF of links. The third-class is those mechanisms whose DOFs are greater than the maximum DOF of links. After analyzing some examples, it comes to an important conclusion that the DOF of links (including output link) is the number of independent displacement parameters with motion properties. The DOF of mechanism is only the number of all independent parameters which keep all links have definite position and orientation. It is only a natural number without the property of motion. The DOF of mechanism doesn't rely on the choice of output link. It reflects property of whole mechanism. The DOF of links reflects the property of one link in mechanism. In application, the DOF of mechanism and the DOF of links have district differences, which should not be confused.

Key words： DOF of mechanism; DOF of links; DOF of link-group; DOF of output link

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