The Complete Determination of Squeeze-Film Linear Dynamic Coefficients From Experimental Data

Abstract

This paper describes the use of the State Variable Filter (SVF) method of parametric identification to estimate the complete set of twelve linear hydrodynamic coefficients for a squeeze-film bearing system. Simulated force and displacement data are used to assess the algorithm and issues such as noise tolerance, the influence of sample time interval and input signal complexity are investigated. Real experimental data from a squeeze-film rig are processed by the SVF method and the technique used to derive linearized model coefficients is explained. For the first time, all twelve coefficients in the general linear model are estimated from experimental data. Tables and graphs are used to present the coefficient values. Sixteen parameters (including four parameters relating to initial conditions) are identified in each experiment. The direct coefficients show the same trends and orders of magnitude reported in earlier and simpler tests, relating to a single-degree-of-freedom system. The damping cross-terms are found to be virtually zero whereas the inertial and stiffness cross-terms appear to be significantly nonzero.