A Study on Stability Characteristics of Actively Controlled Hydrodynamic Journal Bearings

Abstract

Results of theoretical investigations on stability characteristics of an actively controlled hydrodynamic journal bearing are presented. The proportional and derivative controls including coupled motion are adopted for the control algorithm to control the hydrodynamic journal bearing with a circumferentially groove. Also, the cavitation algorithm implementing the Jakobsson-Floberg-Olsson boundary condition is adopted to predict cavitation regions in the fluid film more accurately than a conventional analysis with the Reynolds condition. The stability characteristics are investigated with the Routh-Hurwitz criteria using the linear dynamic coefficients which are obtained from the perturbation method. The stability characteristics of the rotorbearing system supported by active controlled hydrodynamic journal bearing are investigated for various control gain. It is found that the speed at onset of the instability is increased for both proportional and derivative control of the bearing, and the proportional and derivative control of coupled motion is more effective than proportional and derivative control of uncoupled motion.