Three dimensional modeling of the lower extremity for the study of static standing postures in Functional Electrical Stimulation (FES)

A highly desirable enhancement to Functional Electrical Stimulation (FES) aided standing would be the ability to stand without using the upper extremities for support or balance (hands free standing). To achieve this, a deeper insight into the stability of the system is required to design robust but simple controllers for maintaining the posture. We are examining this problem using simulations with a full three-dimensional modeling of the lower extremities and pelvis. This paper describes a major step in this effort: solving the inverse dynamics for the closed chain model of a typical stance. We have critically examined the main reasons why the closed chain model is problematic and have developed an equivalent approach that avoids using a closed chain model by accurately estimating the ground reaction forces. This approach has been applied to the inverse dynamics problem related to human static standing.