Incorporation of Active Elements into the Articulated Total Body Model.

Abstract : The Articulated Total Body (ATB) Model, based on rigid-body dynamics with Euler equations of motion and Lagrange type constraints, is used by the Harry G. Armstrong Aerospace Medical Research Laboratory to predict the forces and motions experienced by air crew personnel in typical flight operations. To provide a more realistic representation of human dynamics, active neuromusculature was added to the ATB Model using elements of the newly developed advanced harness system. A lumped three-parameter muscle model with a contractile element, a damping element and a parallel elastic element was developed. The contractile element included a length-tension relationship, a force-velocity relationship and an active state function. The basic fiber mechanisms were integrated into muscle systems utilizing motor unit organization, orderly recruitment of motor units and adjustments in force due to fatigue and reflex action. The complete muscle systems were then used to replicate the human neuromusculature of the trunk and neck and for the elbow, shoulder, hip and knee joints.