Kevin S. Giaier



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This research presents a methodology for designing mechanical chains comprised of a large number of identical spherical four-bar mechanisms. Such a mechanical chain can achieve up to five prescribed helices. A spherical four-bar mechanism is a single degree of freedom device consisting of four revolute (R) joints whose rotational axes intersect at a common point. The mechanical chains are created by connecting the coupler of the prior spherical mechanism to the base link of the subsequent spherical mechanism. An extension on each mechanism will lie along the prescribed helices as the device moves. The methodology introduces a companion helix to each prescribed helix along which the intersection locations of each spherical mechanism's axes must lie. As the mechanisms are connected by rigid links, the distance between the intersection locations along each companion helix is the same. Additionally, an approach to actuating this mechanical chain with a single rotating input is presented.

Publication Date


Project Designation

Graduate Research

Primary Advisor

David Myszka and Andrew Murray

Primary Advisor's Department

Mechanical and Aerospace Engineering


Stander Symposium project


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Serial Chains of Spherical Four-Bar Mechanisms to Achieve Design Helices