Active control of self-excited vibrations for a high-speed rotating machinery

This paper deals with an experimental study on the active control of self-excited vibration for a high-speed turbomachinery, In order to suppress the self-excited vibration, it is necessary to actively control the air film pressure or the air film thickness. In a tilting-pad gas bearing (TPGB), a shaft is supported by the pressurized air film, which can be modeled as a spring and damper system. Thus, disturbances, i. e., various kinds of external forces, can cause the shaft vibration as well as the change of the air film thickness. Active pads are used to control the air film thickness. The active pads are supported by pivots containing piezoelectric actuators and their radial position can be actively controlled by applying voltage to the actuators. The transfer characteristics from actuator inputs to shaft vibration outputs are experimentally investigated. The characteristics of self-acting gas bearing with active pads are investigated. We investigated the unstable vibration suppression performance by changing gain of the feedback control and the phase angle of the control force. As a result, we found that the feedback control is effective for suppressing self-excited vibration.