Date of Award

Fall 1998

Document Type

Dissertation - Restricted

Degree Name

Doctor of Philosophy (PhD)


Mechanical Engineering

First Advisor

Schimmels, Joseph M.

Second Advisor

Heinrich, Stephen M.

Third Advisor

Nagurka, Mark L.


This work addresses a method for improving vertical whole body vibration isolation through optimal seat suspension parametric design. The primary thrusts of this investigation are: (1) the development of a simple model that captures the essential dynamics of a seated human exposed to vertical vibration, (2) the selection and evaluation of several standards for assessing human sensitivity to vertical vibration, and (3) the determination of the linear and nonlinear seat suspension parameters that yield optimal vibration isolation. For the linear seat suspension, results show that the optimal seat damping coefficient depends very much on the selection of the vibration sensitivity standard, on the lower bound of the stiffnesses used in the constrained optimization procedure, and on vibration environments. In all cases, however, the optimal seat damping obtained here is significantly larger (a factor of 2 to 10) than that obtained using existing seat suspension design methods or from previous optimal suspension studies. This research also indicates that the existing means of assessing vibration in suspension design (ISO 7096) requires modification. For the nonlinear seat suspension, results show that different vibration environments alter the optimal values of all seat parameters, especially the optimal nonlinear damping value; different initial conditions have significant effects on the optimal values of the nonlinear part of the damping; and different human properties have little effect on the optimal values of all seat parameters. In all nonlinear seat suspension cases, the optimal values of the objective function are much smaller than those of the linear seat suspension. The analysis shows that the optimal nonlinear seat suspension is much better than the optimal linear seat suspension and can be realized using a mechanism consisting of linear springs and dampers.



Restricted Access Item

Having trouble?