Lateral Dynamics of Flexible Rotors Supported by Controllable Gas Bearings Theory & Experiment

Active gas bearings might represent a mechatronic answer to the growing industrial need for high performance turbomachinery. In this framework, the paper gives a theoretical and experimental contribution to the improvement of lateral dynamics of rotating machines. The work aims at demonstrating theoretically as well as experimentally the feasibility of applying active lubrication to gas journal bearings. The operation principle is to generate active forces by regulating the radial injection of a compressible lubricant (gas) by means of piezoelectric actuators mounted on the back of the bearing sleeve. The active control principle is built using eddy-current sensor signals to detect the lateral motion of the rotor. A feedback law is used to couple the lateral dynamics of a flexible rotor-bearing system with the pneumatic and dynamic characteristics of a piezoelectric actuated valve system. A proportional derivative (PD) control is designed based on a theoretical model and experimentally validated. Results show the considerable performance advantages of such a type of controllable bearing. Discrepancies between theoretical and experimental results are elucidated in the paper, considering some simplifying assumptions used to derive the control matrix.