Minimization of the Variance in Oil-Film Damping Coefficient Estimates

The frequency-domain algorithm developed by the authors to estimate oil-film bearing coefficients uses a Least Squares estimator and produces the variances and confidence bounds for the estimates. The variances can be minimized by correct design of the experimental procedure as well as by the data analysis package. The coefficient estimates are obtained by applying a multi-frequency test signal, measuring the applied force and corresponding journal displacements along orthogonal axes, and implementing the estimator. The paper discusses the use of D-optimality to select the measurement axes to improve the quality of the estimates. Experimental results obtained from a squeeze-film bearing rig are presented and discussed.