Control strategy for an unsymmetrical rotor system with an active tilting pad journal bearing

The nonlinear dynamic model of unsymmetrical flexible rotor-bearing system of 8-DOFs with the effect of gyroscopic moment is formulated in this paper. The active lubrication action, which is based on injecting pressurized oil into the bearing gap through orifices machined in the bearing sliding surface, is utilized to suppress the shaft vibrations. A PI controller is designed for the active lubrication to change the rotor-bearing equilibrium position. The finite difference method is applied to solve the pressure distribution on each titling pad surface of the actively lubricated system. Numerical results show that the actively lubricated system presents effective vibration reduction of unbalance response of a flexible rotor and the PI controller exhibits better performance. The feasibility of eliminating rotor-bearing instabilities (phenomena of whirl) by using active lubrication is also investigated, which illustrates clearly one of its most promising applications.