Browse Publications Technical Papers 2003-01-2207

System Identification of Quasi-static Foam Behavior and its Application in H-point Prediction 2003-01-2207

Hip joint location (H-point) is an important design specification used by car seat manufacturers. Since most of the modern car seats are full-foam seats, the H-point location is primarily dependent on the quasi-static behavior of foam which is a highly nonlinear and viscoelastic material. In this work, a constitutive model is developed for flexible polyurethane foam. The stiffness characteristics of foam are described by a polynomial in displacement and the viscoelastic behavior is described by a convolution of the response with a kernel which is assumed to be a sum of exponentials. A system identification procedure, based on linear least squares fitting and ARMA modeling, is developed to identify the parameters from data collected in quasi-static foam experiments. Once identified, these models of foam are incorporated into two dimensional multi-degree-of-freedom seat occupant models to determine the static equilibrium position of an occupant in a seat from which the H-point location is determined. A graphical user interface is developed to facilitate study of the influence of changes in system parameters and also to visualize the settling of the occupant in the seat.


Subscribers can view annotate, and download all of SAE's content. Learn More »


Members save up to 43% off list price.
Login to see discount.
Special Offer: With TechSelect, you decide what SAE Technical Papers you need, when you need them, and how much you want to pay.