MAE SEMINAR: “Control Methods for Integrating Functional Electrical Stimulation and Ultrasound Imaging in a Powered Exoskeleton.”

Biography:

Nitin Sharma received the B.E. degree in Industrial Engineering from Thapar Institute of Engineering and Technology, India, in 2004, and the M.S. degree and the Ph.D. degree in Mechanical Engineering from the Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, in 2008 and 2010 respectively. He was an Alberta Innovates-Health Solutions Post-Doctoral Fellow with the Department of Physiology, University of Alberta, Edmonton, Canada. From 2012-2017, he was an Assistant Professor with the Department of Mechanical Engineering and Materials Science, University of Pittsburgh, and promoted to an Associate Professor in 2018. In 2019, he joined the Joint Department of Biomedical Engineering at North Carolina State University-Raleigh and University of North Carolina-Chapel Hill. He has won O. Hugo Schuck Award for the Best Application Paper from the 2008 American Control Conference. His research in hybrid exoskeletons is funded by NSF awards and NIH. His awards include NSF CAREER Award in 2018, IEEE Control Systems Technology Award 2019, and NIBIB Trailblazer Award in 2021.

Abstract:

A hybrid exoskeleton that combines functional electrical stimulation (FES) and a powered exoskeleton is an emerging technology for assisting people with mobility disorders. The cooperative use of FES and the exoskeleton permits active muscle contractions through FES while robustifying torque generation with the exoskeleton assistance. However, the control design must overcome the rapid onset of muscle fatigue to enable desired closed-loop coordination between FES and the powered exoskeleton. Additional challenges such as inherent uncertainties and nonlinearities in the musculoskeletal system, electromechanical delay (EMD), and human intent should also be considered to avoid potential instability. 

In this talk, I will go over Lyapunov-based nonlinear control design methods to control FES and a hybrid exoskeleton to restore sit-to-stand and walking functions in people with spinal cord injury. Specifically, I present continuous and switched control designs that compensate for EMD and provide synergistic control of FES and exoskeleton. I will also present our most recent work that facilitates the incorporation of ultrasound imaging-derived muscle state signals in the Lyapunov-based control design.