On the Development of a Robotic Biarticular Prosthesis Emulator

Abstract

People with transtibial limb loss experience decreased walking ability and have long-term musculoskeletal issues, such as knee osteoarthritis. Currently available ankle-foot prostheses, which only actuate the ankle joint, do not replicate the biarticular nature of the gastrocnemius muscle, which may limit their clinical efficacy. It is possible that transtibial prosthesis designs that include knee flexion assistance through a knee exoskeleton or exosuit could improve gait and quality of life for people with transtibial limb loss. However, the design space of these devices is large, and it is difficult to determine how biarticular gait assistance from different device designs might help people with limb loss. Therefore, developing a method to rapidly test and compare a variety of biarticular prosthesis designs is crucial for improving the lives of people with transtibial limb loss. The objectives of this work were to design, build, and evaluate a biarticular prostheses emulator – a device that combines a robotic ankle-foot prosthesis and knee exoskeleton that can behave like a variety of hypothetical device embodiments to facilitate scientific exploration in a laboratory environment. This work was separated into three studies. The first study detailed the design, control, and evaluation of a uniarticular robotic ankle-foot prosthesis with offboard actuation and control. The prosthesis design incorporated novel design choices compared to other prosthesis emulators, including a commercial foot plate and parallel torsion spring to provide dorsiflexion moments during walking. The prosthesis was found to be able to emulate both idealized passive devices and powered devices in walking experiments. The second study explored the design and control of a robotic knee exoskeleton emulator specifically for people with transtibial amputation. The third and final study presented the design and evaluation of an integrated biarticular prosthesis emulator that combined the robotic ankle-foot prosthesis with a second-generation design of the robotic knee exoskeleton. The biarticular prosthesis emulator design and control were evaluated with benchtop experiments and a walking demonstration that showed the prosthesis emulator’s ability to provide simultaneous knee and ankle assistance during walking. The primary contributions of this work are the design and development of several novel assistive devices for people with transtibial limb loss. Due to our modular design approach, future research may use either the ankle-foot prosthesis or knee exoskeleton as stand-alone uniarticular assistive devices, or together as a biarticular prosthesis. The work in this dissertation lays the foundation for a future research program that uses these devices to explore biarticular gait assistance and compare different hardware embodiment for prostheses that improve health and quality of life for people with transtibial limb loss. The potential impact of this work is significant, as the development of more effective prostheses for people with transtibial limb loss can significantly improve their mobility and overall quality of life.