Development and Validation of a Self-Adapting Myoelectrically Controlled Prosthetic Ankle with Continuously Variable Stiffness
Abstract
Whether an individual is walking slow or fast, on level ground, or ascending or descending a set of stairs, the biomechanics occurring at the ankle vary dramatically. Unfortunately, current prosthetic feet cannot respond to these changes in mechanics. Many of the feet offered have the ability to store and return energy to the user through the deflection of carbon fiber springs, but the spring stiffness is often design for level-ground walking and cannot be adjusted after production. Therefore, patients and prosthetists must select from a range of available stiffnesses and use the same selected stiffness for different mobility tasks. The goal of this proposed effort is to address this gap through the development and validation of a variable stiffness prosthetic ankle design that includes efferent control to improve prosthetic device function. The variable stiffness prosthetic ankle design investigated in this proposal emulates the human ankle torque-ankle relationship during stance phase and offers a solution that can adjust the mechanics dependent on the mobility task. The foot will further advance the field by investigating the benefit of muscle contraction data to help determine the appropriate stiffness of the ankle. These signals are capture by a liner with embedded electrodes. The tasks of this proposed effort will directly address the development of the prototype that will be used to demonstrate improved biomechanics and function. The project goals will be accomplished through the completion of three objectives. The initial efforts will focus on evaluating the current prototype design through the use of international standard strength test protocols to provide design refinement criteria. Next, clinical testing will be completed to determine what the optimal ankle stiffness for different mobility tasks if for each participant. Data will be collected to determine joint positions and joint forces for comparison between the study conditions. Lastly, muscle contraction data collected during the clinical testing will be evaluated to evaluate the impact of these signals on the ability to determine what mobility task a prosthesis user is performing. Through more accurate replication of the anatomical ankle stiffness, we expect to find greater socket comfort by reducing socket loading, aid in the forward progression by reducing or eliminating the “dead zone” that amputees commonly complain about, and reduce the time of heal-only contact with the ground by quickly achieving foot-flat for improved stability. Varying the stiffness of the ankle will allow the foot to return energy to the user rather than loosing that energy via damping mechanisms like currently available microprocessor controlled prosthetic feet. The addition of muscle data into the control of the slider position is expected to reduce the classification of mobility task. Overall, the proposed variable stiffness ankle design is likely to have a multitude of beneficial side effects, including decreased metabolic cost, decreased gait asymmetries, improved stability, decreased loading through the socket, and decreased pain. Improvements in protective armor and medical practices have increased combat injury survival rates. Thus, the number of Service personnel surviving with amputations has increased with current estimates exceeding 1200 surviving amputees, many of whom have sustained more than one limb amputation. While a primary goal of many military personnel having an amputation is to lead normal, productive lifestyles, an important secondary goal is the potential to return to active duty status and continue their military service. Critical to regaining normal lifestyles and even returning to active duty is to have a highly functional prosthesis that can respond according to the activity and ultimately, one that can respond to user commands and even return feedback about the environmental to the user. The proposed solution will provide a
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 29, 2018
- Source ID
- W81XWH1710704
Entities
People
- James Colvin
Organizations
- United States Army
- Willow Wood (United States)