An Undergraduate Honors in the Major Thesis Submitted to the Department of Mechanical Engineering in partial fulfillment of the requirements for the degree of Master of Science
Degree Awarded: Spring Semester, 2012

Research has shown that being able to vary the effective limb stiffness of legged robotics can aid in efficient locomotion. This is especially true when considering a variety of terrains and payloads. Recent developments have lead to multiple solutions for implementing variable compliance mechanisms, including mechanically actuated methods as well as smart materials. These methods have typically been directed toward moderately large, dynamic running platforms. Less work has been performed on small scale robotics.

This work presents the design of a a new robotic leg mechanism for a variable stiffness application. The design utilizes dielectric elastomer (3M VHB 4910) pre-stretched into a diaphragm to rapidly control stiffness changes for enhanced mobility and agility of a field demonstrated, small scale hexapod robot, iSprawl. The diaphragms developed are modular in nature to allow for ne tuning of the permissible stiffness range. A set of electro-mechanical test are utilized to obtain up to 92% reduction in stiffness that is controlled by an electric field. Preliminary transient tests are used to characterize the response time of the system when exposed to sudden field application. The device achieves a full transition to a decreased stiffness approximately 66ms post field application. This work demonstrates a functional mechanism for exhibiting tunable compliance on a reduced scale architecture and outlines the necessary methods for future implementation.