An Actively Controlled Journal Bearing With Increased Resistance to Instability

Abstract

Journal hydrodynamic bearings are used for their high radial load capacity and operation at high speeds. The only disadvantage is the excitation of vibrations, called an oil whirl, after crossing a threshold of the rotational speed. The whirl can be suppressed using the controlled motion of the non-rotating loose bushing which is actuated by piezo-actuators. The displacement of the piezo-actuators is governed by a feedback which reduces the difference between the required and true position of the bearing journal. This new bearing design enables not only to increase the threshold of instability but also serves to maintain the desired bearing journal position with the accuracy of micrometers. The article deals with the design of an actively controlled bearing with special regard to the installation of piezoelectrometers. Part of the article is also a description of the influence of active vibration control on bearing performance characteristics and bearing friction losses.