Vibration control of a flexible rotor/magnetic bearing system subject to direct forcing and base motion disturbances

Abstract

During operation, a rotor/magnetic bearing system may be subject to various sources of vibration, either directly applied to the rotor or transmitted through the bearings owing to base motion. This paper considers controller designs that are capable of attenuating vibration arising from either source. It advances the current state of research in the area since other controller designs have considered only the direct forcing case. If base motion is not considered in the design of the controller then this disturbance may cause the bearing clearance limits to be reached. Controller design is formulated as an H∞ optimization problem, with mixed design objectives. A new controller is derived that can simultaneously reduce vibration and minimize the effect of base motion on relative rotor to bearing displacement. Account is taken of the fact that the bearings can apply only limited control force. The design study was complemented by a programme of experimental work. The base of a rig was subjected to impulse inputs and the results show the effectiveness of the new controller design. It is demonstrated that proportional, integral and derivative (PID) controllers, or controllers designed for unbalance vibration attenuation only, may result in rotor contact with retainer bushes, while the new controller may prevent contact. The potential now exists for continuing safe operation of flexible rotor/magnetic bearing systems such as compressors, gas turbines, generators, etc., in transport applications, during seismic events or in environments with expected base input disturbances.

Fault-tolerant control of rotor/magnetic bearing systems using reconfigurable control with built-in fault detection

“…Consider a standard linear state-space model (in discrete time), used to describe a typical rotor/magnetic bearing system [10], with additional fault signal inputs:…”

“…Four pairs of eddy current transducers (sensors), ®xed to the system base, measure rotor position. The experimental system is described further in reference [10]. The sensor arrangement used for the recon®gurable control strategy uses eight sensors in four planes as shown in Fig.…”

Dynamic Modeling of the Active Magnetic Bearing System Operating in Base Motion Condition

“…For instance, Kasarda et al [16] modified the PID controller gains on a non-rotating test rig with a single magnetic bearing mounted on a shaker to detect the effect of sinusoidal base motion. Cole et al [17] designed controllers that were capable of attenuating vibration arising from either directly applied to the rotor or transmitted through the bearings owing to base motion. Kang [18][19] presented an optimal base acceleration feedforward controller using filtered-X least-mean-square (LMS) algorithm and sliding mode controller to reduce the base motion response.…”

The vibration control of speed-dependent flexible rotor/magnetic bearing systems using linear matrix inequality gain-scheduled H∞ design

“…The H ' design method allows the formulation of these constraints in a unified framework. Research in the field of multiobjective time-invariant control design was undertaken by Cole et al [14], who investigated the vibration control of a system subject to separate direct forcing and base motion inputs. In a multibearing system, the dynamic forces transmitted across the clearance spaces may be related to relative displacements through a dynamic stiffness matrix.…”