Simulation and design of an active orthosis for an incomplete spinal cord injured subject

Abstract

The dynamic simulation of incomplete spinal cord injured individuals equipped with active orthoses is a challenging problem due to the redundancy of the simultaneous human-orthosis actuation. The objective of this work is two-fold. Firstly, a physiological static optimization approach to solve the muscle-orthosis actuation sharing problem is presented. For this purpose, a biomechanical model based on multibody dynamics techniques is used. The muscles are modeled as Hill-type actuators and the atrophy of denervated muscles is considered by adding stiff and dissipative elements. Secondly, the mechanical design of a new active stance-control knee-ankle-foot orthosis (A-SCKAFO) is addressed. The proposed device consists of a passive joint that constrains ankle plantar flexion, along with a powered knee unit that prevents flexion during stance and controls flexion-extension during swing. The knee actuation is selected based on the results obtained through the optimization approach.