Design of springs with “negative” stiffness to improve vehicle driver vibration isolation

Minimization of the fundamental frequencies of a vibratory system by means of springs with “negative” stiffness is probably the only way to attain infra-frequency vibration isolation under gravitation. Traditionally, the design of similar springs for vehicle driver vibration isolation systems was an art, and design decisions were based primarily on the designer experience. This paper presents an approach, based on the consistent theory of thin shells, for designing compact springs in terms of their compatibility with the room available for packaging the vehicle suspensions and simultaneous extension of the height control region where fundamental frequencies are kept minimal. In the approach, a generic model of a simple springing element with “negative” stiffness in the large is proposed. A simple iterative procedure is formulated to solve the geometrically nonlinear problem of large-amplitude post-bucking of springing elements and to represent them in a way that enables an optimal, computable scheme for the design of springs. Validity of the approach is assessed by a comparison of the computation and measurement results. Using the approach, we propose a generic spring module applicable to any vehicle suspension, whether it is a seat suspension, a cab mounting, or a cargotainer platform.