Vertical dynamics of high-pressure air cushion bearing module: Stability and auto-oscillation

Abstract

Unstable static equilibrium and vertical auto-oscillations are problems encountered in the application of a high-pressure air cushion module (ACM) for the indoor transportation of heavy loads. The results of two base methods are compared: linear stability analysis based on the linearized equations of the perturbed motion coupled to airflow fluctuations and numerical evaluation of the nonlinear dynamic response of the system. The main distinguishing feature of the analysis is that it comprehensively examines air compressibility in the cushion plenum and in the inlet and outlet flow zones. Accordingly, the study and its findings are valid for high-pressure and low-flow applications of air cushion transportation. A narrow stability region in the parameter domain is identified when the cushion pressure approximates the supply pressure. The peculiarities of the vertical dynamics of the system near stable and unstable static equilibrium positions are described, and influence of viscous damping is considered. The study results contribute to the generalized representation of the stability and vertical dynamics of ACMs and to the theoretical database for ACM design.