Experimental Investigations of Decentralised Control Design for The Stabilisation of Rotor-Gas Bearings

Rotor-gas bearings are attracting increasing interest because of their high speed capabilities, low friction and clean operation. However, hydrostatic rotor-gas bearings show reduced damping characteristics, which makes it challenging to operate the rotating machine at and about the resonance frequencies. Active lubrication of the journal during operations could enhance the damping and stabilisation characteristics of the sytems, and this could be achieved by means of stabilising controllers. This paper investigates the feasibility of using reduced order models obtained through Grey-Box identification for the design of stabilising controllers, capable of enabling the active lubrication of the journal. The root locus analysis shows that two different control solutions are feasible for the dampening of the first two eigenfrequencies of the rotor-gas bearing in the horizontal and vertical directions. Hardening and softening P-lead controllers are designed based on the models experimentally identified, and salient features of both controllers are discussed. Both controllers are implemented and validated on the physical test rig. Experimental results confirm the validity of the proposed approach.