摘要
针对平面机构中轨迹重合虚约束的判定问题,提出通过对机构拆分杆组及速度分析相结合的判定方法。应用该方法通过以下两步骤可对机构中的轨迹重合虚约束进行判定:步骤1,对机构拆分杆组,确定机构具有负值杆组;步骤2,拆分负值杆组中的一个转动副,确定拆分后组成原转动副的两构件在转动副中心速度方向共线,则可以判定该机构具有轨迹点重合虚约束。研究结果表明:该方法不仅适用于轨迹点重合虚约束的判定,而且也适用于两构件距离不变两点间加入构件和运动副类虚约束及不影响机构运动传递的重复部分引入的虚约束的判定。该研究有助于对虚约束概念的加深理解及机构创新设计。
In this paper,the method of combining the splitting of linkage group and velocity analysis is put forward to solve the problem of the recognition of redundant constraints of trajectory coincidence in the calculation of degree of freedom in planar mechanisms.Using the method,the existence of a redundant constrain of trajectory coincidence could be identified according to the following two steps.Step one,decompose the drived links of a mechanism into Assur groups,and make sure the existence of Assur group with negative degree of freedom.Step two,separate a revolute pair formed by two links in the Assur group with negative degree of freedom and make sure the directions of the speed of the two points at the center of revolute on the two links are in the same line.Then it can be judged that the mechanism has the redundant constraint of trajectory coincidence.The results show that the method is not only suitable for the identification of redundant constraints of trajectory Coincidence,but also suitable for the identification of the redundant constraint caused by adding an link with two revolute pairs at two points on two different links with fixed distance,as well as the redundant constraints introduced by the repetitive part which does not affect the motion transmission of the mechanism.This study is helpful to understand the concept of redundant constraint and innovative design of mechanism.
作者
张晓伟
潘继生
傅惠
ZHANG Xiao-wei;PAN Ji-sheng;FU Hui(School of Electromechanical Engineering,Guangdong University of Technology,Guangzhou 510006)
出处
《机械设计》
CSCD
北大核心
2021年第S02期75-78,共4页
Journal of Machine Design
基金
广东省一流本科课程建设研究项目(2020 No.16)
广东工业大学“本科教学工程”项目(广工大教字(2020)22号,广工大教字(2016)54号,广工大教字(2021)71号)
关键词
平面机构
基本杆组
轨迹重合
虚约束判定
自由度
planar mechanism
Assur group
trajectory coincidence
identification of redundant constraint
degree of freedom
