A Design System for Eight Bar Linkages as Constrained 4R Serial Chains

Abstract

This paper presents a design system for planar eightbar linkages that adds three RR constraints to a userspecified 4R serial chain. R denotes a revolute, or hinged, joint. There are 100 ways in which these constraints can be added to yield as many as 3951 different linkages. An analysis routine based on the Dixon determinant evaluates the performance of each linkage candidate and determines the feasible designs that reach the task positions in a single assembly. A random search within the userspecified tolerance zones around the task specifications is iterated in order to increase the number of linkage candidates and feasible designs. The methodology is demonstrated with the design of rectilinear eightbar linkages that guide an endeffector through five parallel positions along a straight line.