Graduate Studies


First Advisor

Carl Nelson

Date of this Version

Spring 4-23-2020


Jensen, N. 2020, 'A New 6-Degree-of-Freedom 3-Leg Parallel Manipulator', M. Sc. Thesis, University of Nebraska - Lincoln, Lincoln, NE, USA


A THESIS Presented to the Faculty of the Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science. Major: Mechanical Engineering and Applied Mechanics. Under the Supervision of Professor Carl A. Nelson, Lincoln, Nebraska: May, 2020.

Copyright 2020 Nathan Jensen


From their inception in the first half of the last century, parallel robots have advanced and diversified with several key goals. Among these, increased workspace size and kinematic performance take precedence. Many parallel architectures have been proposed to maximize such metrics; these often take the form of novel joint combinations or linkage configurations. Such studies on a new parallel robot are the focus of this thesis.

This thesis summarizes the work in prototyping, validation, and theory development of a new 6 degree-of-freedom, 3-leg parallel manipulator whose legs are in RRRS configuration. This arrangement of legs, with two powered revolute joints at its base, a passive revolute joint between its two links, and a spherical joint connecting to the end effector, warrants study. An initial prototype was constructed; the resultant testing and the manipulability analysis it provides are discussed. An improved derivation of the inverse kinematics for the manipulator is presented, along with a derivation for the manipulator’s Jacobian. This Jacobian allowed for the study of performance metrics such as torque requirements, manipulability, singularities, and stiffness. An optimization scheme was executed to maximize the workspace of the manipulator as well; the results were both reported and used to plan a second, larger-scale prototype. This prototype was designed, constructed, evaluated, and re-designed to mitigate failure modes.

The presented development forms a collection of critical strides forward for the system. Such a collection will be the foundation of future work in more precise optimization, finer control, and theoretical development.

Advisor: Carl A. Nelson