Nonlinear time-varying identification of human arm joint mechanical properties using a portable pneumatic thruster

The goal of this research is to determine the joint mechanical properties of the freely moving human arm, by utilizing an unconstraining force perturbation device and developing nonlinear time-varying system identification methods. The authors formulate the human arm model by identification using perturbation, and present a pneumatic perturbation system and two identification methods, exponentially weighted least squares (EWLS) and highpass mean removal ensemble data (HRED). The experimental results on human elbow joint in posture and movement as well as the effect of the small perturbation on the joint dynamics are presented