Condition Monitoring of Rotor Using Active Magnetic Actuator

Abstract

It has been widely recognized that the changes in the dynamic response of a rotor could be utilized for general fault detection and monitoring. Current methods rely on the monitoring of synchronous response of the machine during its transient or normal operation. Very little progress has been made in developing robust techniques to detect subtle changes in machine condition caused by rotor cracks. It has been demonstrated that the crack-induced changes in the rotor dynamic behavior produce unique vibration signatures. When the harmonic excitation force is applied to the cracked rotor system, nonlinear resonances occur due to the nonlinear parametric excitation characteristics of the crack. These resonances are the result of the coexistence of a parametric excitation term and different frequencies present in the system, namely critical speed, the synchronous frequency, and excitation frequency from the externally applied perturbation signals. This paper presents the application of this approach on an experimental test rig. The simulation and experimental study for the given rig configuration, along with the application of active magnetic bearings as a force actuator, are presented.

Detecting cracked rotors using auxiliary harmonic excitation

“…The approach is demonstrated on a test rig utilized at the Center for Rotating Machinery Dynamics and Control (RoMaDyC) at Cleveland State University [19,20]. The photo of rig and its schematic are presented in Fig.…”

Crack identification by multifractal analysis of a dynamic rotor response

“…The alternative way is to analyze the corresponding Fourier spectrum [7,8], however in this approach one needs to examine longer time series. Note that the notch of 1mm does not posses all features of a real crack.…”

“…earlier by Sawicki et al [7] where the main issue was the identification of Fourier amplitudes related to rotational frequency and its multiple values as 1X, 2X, 3X, 4X with and without magnetic excitation. The preliminary experimental results were predicted by the modelling with FEM.…”

“…2c) and cracked ( Fig. 2d) rotors are subjected to the magnetic actuator applied harmonic force having amplitude of 200 N p-p (peak-to-peak) and fixed frequency [7].…”

Exploration of NDE Properties of AMB Supported Rotors for Structural Damage Detection

“…Lastly, 4 = it + 4 0 is the angle between the crack axis and the rotor response at the crack location and T is the transformation matrix from rotating to iner tial coordinates. Assuming weight dominance or Iq st I � IqI and taking into ac count that K 0 q st = W, one can obtain the parametrically excited cracked rotor model in fixed coordinates system as follows [3,4,6]:…”