Active Control of Multi-Mode Rotor-Bearing Systems Using HSFDs

Abstract

This paper summarizes the modeling and control of hybrid squeeze film dampers (HSFDs) for active control of vibration of rotors exhibiting multiple modes. In a recent paper (El-Shafei and Hathout, 1994), it was shown that the automatically controlled HSFD based on feedback on rotor speed can be a very efficient device for active control of rotor vibration. It was shown that this closed-loop, on-off control strategy results in a much improved behavior of the rotor system. The previous investigation was performed on a Jeffcott rotor model. The model was simple and fluid inertia effects were not taken into consideration. In this paper, major strides were made in both the modeling of the rotor and the HSFD. Modal analysis was implemented in the dynamic analysis of the squeeze film damper supported rotor in a novel and unique manner of performing modal analysis on nonlinear rotor systems. This allowed the modeling of any number of modes using modal analysis and hence to verify the capability of the HSFD to control multiple modes. Also, fluid inertia forces were considered in our model for the HSFD due to their direct influence in changing the behavior of the damper (El-Shafei and Crandall, 1991). A complete mathematical model of this open-loop system is developed and is implemented on a digital computer. Finally, based on the feedback on speed, the closed-loop behavior was studied from both steady-state and transient points of view and showed an overall enhanced behavior for the rotor system.