Synthesis and Analysis of Stephenson III Six-Bar Motion Generators With an Instantaneous Stop Link

This article deals with the synthesis and analysis of Stephenson III six-bar motion generators with, a coupler link instantaneous stop of the five-bar loop and a crank-driven four-bar loop. The proposed design procedure consists of adding a dyad of RRR or PRR types to a crank-driven four-bar mechanism, which can include a prismatic pair, thus giving the slider-crank or swinging-block mechanisms. In particular, starting with a suitable configuration of the crank-driven four-bar mechanism, a ternary coupler link is designed in such a way to have the third vertex as coincident with its instant center of rotation (IC). Then, the first revolute joint R of the dyad is installed on this IC and the last R or P joints of the RRR or PRR dyads are positioned freely on the fixed plane. Thus, the kinematic analysis of two types of the synthesized Stephenson III six-bar motion generators with an instantaneous stop, as derived by a swinging-block mechanism and a four-bar mechanism, respectively, is formulated and implemented in a Matlab program with the aim to validate the proposed design procedure and analyze the main geometric and kinematic characteristics of this particular rigid body motion, which can find novel practical applications in complex mechanical systems, such as conveying systems, instantaneous dwell mechanisms, mixing machines, and moving platform for amusement parks.