Instantaneous motion and constraint analysis of Bennett linkage

Abstract

Bennett linkage is a well-known spatial four-bar linkage with one degree-of-freedom (DOF). Although mobility analysis of Bennett linkage has been carried out by many researchers, the type, direction and location of the instantaneous motion are seldom discussed. This paper focuses on investigating the full mobility information of Bennett linkage by using analytical method for mobility, and then addresses its extending application to a Bennett-based six-bar linkage. The result demonstrates that the instantaneous motion of Bennett linkage is always a helical motion. However, the location, direction and pitch of the helical motion are changing related to different configurations. An interesting phenomenon is that the direction of helical motion will reverse suddenly when passing through the configuration that the axes of these four links keep collinear. As an extending application, a Bennett-based six-bar linkage is discussed and its peculiar mobility is an instantaneous rotation without considering the bifurcation.