Encoding Biological Step Placement Swing Control Strategies in Powered Prosthetic Legs

Adjusting step length is a central strategy humans use to maintain balance and change walking speeds in daily life. However, current robotic prosthetic legs do not consider step placement. Prosthetic users experience reduced gait stability and an increased risk of falls compared to able-bodied individuals. This project aims to address these limitations by developing control methods for robotic prostheses that can intelligently adjust step length in response to the user’s motion to maintain balance. Enabling prostheses to adapt to an individual’s real-time motion and mimic human step placement behavior would improve the stability and safety of these individuals. This work aims to improve prosthetic options for veterans and other Americans living with limb-loss. By partnering with the Minneapolis Veterans Affairs Health Care System, this research will facilitate engagement with veterans with amputation, reducing the gap between development of technologies and the population the technology is intended to serve. This project will enhance engineering education by providing hands-on research opportunities for students and facilitating interdisciplinary learning in controls, robotics, and biomechanics. The objective of this project is to encode step placement strategies used by humans into the swing control formulation of multi-joint lower-limb powered prostheses. Traditional human step placement models require full-body state information, such as center of mass, which cannot be directly measured by standard sensors. To overcome this limitation, this research will create a center of mass estimation method based entirely on onboard prosthesis sensing. Additionally, this project will develop user-specific data-driven step placement predictors that provide goals for a task-space prosthesis controller. This framework will first be validated in forward-dynamic simulations and then experimentally evaluated through human-subject testing with individuals with lower-limb amputation. This project is expected to restore the link between human motion and prosthesis step placement, providing a unified prosthesis control framework for a range of walking speeds, speed transitions, and perturbations. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.