Theses and Dissertations - UTB/UTPA

Date of Award


Document Type


Degree Name

Master of Science (MS)


Mechanical Engineering

First Advisor

Dr. Robert A. Freeman

Second Advisor

Dr. Horacio Vasquez

Third Advisor

Dr. Javier A. Kypuros


This study presents the theoretical results and experimental validation of an adjustable stiffness mechanism. The use of redundant actuation is emphasized in the design of a one-degree-of-freedom Watt II mechanism capable of independently controlling the effective stiffness without a change in equilibrium position. This approach is in contrast to previous spring mechanism designs unable to actively control the spring rate independent of deflection, and has potential applications in various types of suspension and assembly systems. Results indicate that driving the redundantly actuated, unidirectional, spring mechanism requires attaching two direct brush-type direct current motors on each of the two grounded revolute joints, and that the concept of adjustable springs has proven to be valid regardless of the friction effects. The torques are controlled with corresponding power amplifiers which incorporate current control loops, and the effective stiffness of the system is dependent on the redundant actuator torques of the motors.


Copyright 2010 Eleazar Marquez. All Rights Reserved.

Granting Institution

University of Texas-Pan American