Enhancing damping of gas bearings using linear parameter-varying control

Abstract

a b s t r a c tJournal bearings can be lubricated through controllable injectors using pressurised fluids, whose viscosity highly determines the dynamic responses of the rotating machine. The use of fluids with low viscosity is attracting a growing interest due to the reduced friction forces and consequent losses when the machine is in operation. However low viscosity also entails poor damping properties, which may lead to degraded performance or even instability when the rotating machine operates at or near one of the modal frequencies. This issue can be properly addressed by employing active feedback control systems to regulate the injection pressure of the fluid. Due to the strong dependencies of system performance on system parameters, the sought controller should be robust over a large range of operational conditions. This paper addresses the damping enhancement of controllable gas bearings through robust control approaches. Through an extensive experimental campaign the paper evaluates two robust controllers, a linear parametervarying (LPV) controller and ∞  controller, on their capability to guarantee stability and performance of a gas bearing across the large operational envelopes in rotational speed and injection pressure. The control systems are designed applying state-of-the-art methods in the respective areas. The experimental results clearly demonstrate the feasibility of enhancing the damping properties of a gas bearing by means of robust control methods.

Parametric Fault Diagnosis of an Active Gas Bearing

“…As shown in [10] it is possible to state a model structure as given in Eq . (4) -(7) using a standard state space description of the system as given in equation (2).…”

“…Using Figure 3 the controller gain k was chosen to be −0.2 and the final controller is thus given in equation (10).…”

“…After model reduction, it was shown by the authors to be possible to use them to effectively design model-based controllers. Lately it was shown by [10] that identification of low order models of the position of a shaft held in place by an active gas bearing using a 6âȂŹth order linear model is possible. With such a model it is possible to design advanced controllers such as done in [10].…”

“…Lately it was shown by [10] that identification of low order models of the position of a shaft held in place by an active gas bearing using a 6âȂŹth order linear model is possible. With such a model it is possible to design advanced controllers such as done in [10]. The goal of all the controllers applied to the gas bearings has been to reject external disturbances.…”

Closed loop identification of a piezoelectrically controlled radial gas bearing: Theory and experiment

“…A successful mathematical model for active gas bearings was first introduced in Pierart and Santos 1 with extensions to the model presented in Pierart and Santos. [2][3][4] Recently, a low order model able to describe the dynamics of the active gas bearing was presented in Theisen et al 5 Such low order models greatly simplify the control design phase.…”