The synthesis of six-bar linkages as constrained planar 3R chains

In this paper, we constrain a planar serial chain formed by three revolute joints, so that it becomes a one degree-of-freedom six-bar linkage. Our focus is on the various ways that two RR chains can be attached to constrain the links of the 3R chain, and ensure that the end-effector passes through a set of five specified task positions. This synthesis process yields designs for the Watt I and Stephenson I, II, and III six-bar linkages. This approach does not apply to the Watt II because its floating link is not connected to the ground frame by a 3R chain. We demonstrate the synthesis process with the design of a six-bar steering linkage intended for use on a gravity racer.