We propose a novel biomimetic active prosthesis for above-knee amputees. The clinical impact of this technology focuses on improving an amputee’s gait symmetry, walking speed, and metabolic energy consumption on variant terrain conditions. The electromechanical design of this robotic device mimics the body's own musculoskeletal design, using actuator technologies that have muscle-like behaviors and can integrate control methodologies that exploit the principles of human locomotion. This work seeks to advance the field of biomechatronics by contributing to the development of intelligent assistive technologies that adapt to the needs of the physically challenged.

Motivated by applications in rehabilitation and robotics, we are developing methodologies to control muscle-actuated systems via electrical stimulation. As a demonstration of such potential, we are developing centimeter-scale robotic systems that utilize muscle for actuation and glucose as a primary source of fuel. This is an interesting control problem because muscles: a) are mechanical state-dependent actuators; b) exhibit strong nonlinearities; and c) have slow time-varying properties due to fatigue-recuperation, growth-atrophy, and damage-healing cycles. We are investigating a variety of adaptive and robust control techniques to enable us to achieve trajectory tracking, as well as mechanical power-output control under sustained oscillatory conditions. To implement and test our algorithms, we developed an experimental capability that allows us to characterize and control muscle in real time, while imposing a wide variety of dynamical boundary conditions.

We are studying the mechanical behavior of leg muscles and tendons during human walking in order to motivate the design of economical robotic legs. We hypothesize that quasi-passive, series-elastic clutch units spanning the knee joint in a musculoskeletal arrangement can capture the dominant mechanical behaviors of the human knee in level-ground walking. Biarticular elements necessarily need to transfer energy from the knee joint to hip and/or ankle joints, and this mechanism would reduce the necessary muscle work and improve the mechanical economy of a human-like walking robot.

Gait research on trans-femoral prosthesis users has shown that the metabolic costs for these individuals are significantly higher than those of able-bodied individuals for level-ground walking. Additionally, trans-femoral amputees exhibit a much higher degree of gait asymmetry between the affected and non-affected sides, leading to reduced walking speeds and increased hip and back pain compared to non-amputees. This project consists of a clinical study of five to ten unilateral trans-femoral amputees using either a conventional or a powered knee prosthesis and height-weight matched able-bodied individuals. This work will compare the metabolic cost of transport and biomechanics of conventional standard of care prosthetic knees with a novel powered knee. Amputee performance with each prosthesis will also be compared to the performance of able-bodied individuals. It is hypothesized by using a powered prosthetic knee both the metabolic and biomechanical aspects of amputee gait can be improved.