ROTATING SYSTEM CONTROL USING HYBRID ACTIVE BEARINGS

Strategies to control rotor dynamic behavior are critical to achieve improved performance of rotating machinery. It is possible to control the dynamics of a rotating system through the bearing characteristics, i.e., changing their damping and stiffness coefficients. Bearings that can be commanded to change their characteristics over time are known as active bearings. Because active bearings have a complex design, their use in commercial machines is limited. In this scenario, journal bearings are still regularly used since they can provide damping and high load carrying capacity. Moreover, by modifying the fluid film thickness or clearance, one can control the dynamic behavior of the bearing, which is not a simple task when a traditional geometric format is used. However, since the fluid film thickness is proportional to the axial position of the shaft in conical bearings, their dynamic characteristics could be manipulated through compensation of the shaft’s axial position via a thrust magnetic bearing. Therefore, this paper proposes an alternative hybrid bearing design, which consists of a conical fluid-film bearing and a thrust magnetic bearing. The magnetic bearing is used to sustain the axial force created and actuate the system. For the system analyzed, the new concept was able to reduce the maximum lateral vibration of the rotor by 30%.