Parametric Estimation of a Squeeze-Film Bearing

Abstract

There is a continuing need to develop new experimental techniques for identifying linear models to represent the dynamic behaviour of bearing oil-films. The traditional methods, based upon the application of sinusoidal and step input functions, have yielded limited information due to the presence of noise and other factors. Burrows and Stanway (1977) have considered the particular case of a journal bearing and shown that the experimental determination of the eight linearised oil-film coefficients may be reformulated as a problem of estimating the parameters in a state-space model of known structure.The present paper extends this work to a squeeze-film bearing. In previous experimental investigations of these bearings reduced order models have been identified, whereas here a discrete-time state-space model of the same structure as that used to describe the journal bearing is fitted to sampled observations of rotor displacement and velocity responses. The estimated discretetime parameter matrix is then transformed to obtain estimates of the linearised oil-film coefficients. It is shown that this new formulation eradicates possible errors in the interpretation of results which may arise from the identification of reduced order models.