Ernesto C. Martinez-Villalpando Thesis Defense
Ernesto C. Martinez-Villalpando Thesis Defense: "Design and Evaluation of an Agonist-Antagonist Active Knee Prosthesis"
Thursday, February 09, 2012 | 12:30pm - 2:30pm
Host/Chair: 
Hugh Herr

The loss of a limb is extremely debilitating. Unfortunately, today's assistive technologies are still far from providing fully functional artificial limb replacements. Although lower-extremity prostheses are currently better able to give assistance than their upper-extremity counterparts, important locomotion problems still remain for leg amputees. Instability, gait asymmetry, decreased walking speeds, and high metabolic energy costs are some of the main challenges motivating the development of a new kind of prosthetic device. These challenges point to the need for highly versatile, fully integrated lower-extremity powered prostheses that can replicate the biological behavior of the intact human extremity.

In this thesis Martinez-Villalpando presents the design and evaluation of a novel biomimetic active knee prosthesis capable of emulating intact knee biomechanics during level-ground walking. The knee design is motivated by a mono-articular prosthetic knee model comprised of a variable damper and two series-elastic clutch units spanning the knee joint. The powered knee system is comprised of two series-elastic actuators positioned in parallel in an agonist-antagonist arrangement. This architecture attempts to resemble the body's own musculoskeletal design using actuator technologies that have muscle-like behaviors and control methodologies that exploit the principles of human locomotion.

Furthermore, in this thesis Martinez-Villalpando examines the clinical impact of the active knee prosthesis on the metabolic cost of walking at self-selected speeds of three unilateral above-knee amputees. In the study we compare the antagonistic active knee prosthesis with the subjects' prescribed transfermoral passive and/or variable-damping prosthetic system. The results of the clinical evaluation suggest that an agonist-antagonist active knee prosthesis design with variable impedance control can offer walking energetic advantages over commercially available systems. These results report for the first time a metabolic cost reduction of walking with a prosthetic system comprised of a powered knee and passive foot-ankle prostheses, as compared to conventional transfemoral prostheses. With this work Martinez-Villalpando aims to advance the field of biomechatronics, contributing to the development of integral assistive technologies that adapt to the needs of the physically challenged.