James Yang Seminar

SPEAKER:
James Yang, Ph.D.
Associate Professor
Department of Mechanical Engineering
Texas Tech University

TITLE:
Nonlinear Dynamics of Human Upright Postural Stability on a Balance Board Using an Ankle-Hip Model

ABSTRACT:
Falls are a leading cause of fatal and nonfatal injury, often requiring expensive hospitalization and rehabilitation. Those with balance deficits such as stroke survivors, patients with multiple sclerosis or Parkinson’s disease usually show a higher risk of falls. Hence, it is important to find mechanisms to recover balance abilities to reduce this risk. One method for developing such mechanisms is based on balance training on a balance board (BB). BBs provide a simple way to manipulate sensorimotor feedback information to train patients to react to disturbances. However, despite BB’s wide use, the mechanisms responsible for maintaining upright posture (UP) on a BB are not yet completely understood. This study aims to investigate the nonlinear dynamics of human upright postural stability on a balance board. An anthropomorphic model of the human-BB system is developed by incorporating the hip joint into the human model to form a three degree of freedom inverted pendulum (two for the human body and one more for the BB). Various parameters (such as time-delays, proprioceptive, visual-vestibular, and BB’s spring stiffness feedback gains) are defined as bifurcation parameters and the effect of these parameters on UP stability has been investigated through bifurcation analyses. In addition, the effect of parametric changes on the size of the basin of attractions (BoAs) and the amplitude of the limit cycle (LC) oscillations is investigated.

BIO:
Dr. James Yang is currently an Associate Professor, Ed and Linda Whitacre Faculty Fellow, Director of Human-Centric Design Research Lab at the Department of Mechanical Engineering, Texas Tech University, Lubbock, Texas, USA. He is a Fellow of SAE and Fellow of ASME, and IEEE Senior Member. He received his B.S. and M.S. degrees in automotive engineering from Jilin University, China in 1989 and 1992 respectively. He received his Ph.D. degree in mechanical engineering from the University of Iowa, Iowa City, Iowa, USA, in 2003. He was a faculty member with the Department of Automotive Engineering, Tsinghua University, Beijing from 1992 to 1998 and a Research Engineer with the Center for Computer Aided Design, the University of Iowa from 2003 to 2008. Dr. Yang’s research has been supported by various federal agencies and industries including NSF, NIST, NIOSH, NPSF, USARIEM, DOE, etc. He is currently Associate Editor for five international journals. He is the recipient of the SAE Arch T. Colwell Award, SAE Ralph Teetor Educational Award, three ASME Best Paper Awards, Prometheus Award, Air Force Summer Faculty Fellowship, TTU Chancellor’s Council Distinguished Research Award and among others. His research interests include digital human modeling and simulation, ergonomics, biomechanics, vehicle dynamics, and robotic and mechanical systems.