Application of active magnetic bearings in flexible rotordynamic systems - A state-of-the-art review

The successful industrial application of flexible rotors supported on active magnetic bearings (AMBs) requires careful attention not only to rotordynamic design aspects, but also to electromagnetic and feedback control design aspects. This paper describes the design, construction and modeling process for an AMB test rig which contains a 1.23m long flexible steel rotor, with a mass of 44.9 kg and two gyroscopic disks. The rotor typifies a small industrial centrifugal compressor designed to operate above 12,000 rpm and the first bending natural frequency. There are four AMBs — two AMBs at the shaft ends to support the shaft with a combined load capacity of 2600N and two additional AMBs at the mid and quarter spans to allow for the application of simulated destabilizing fluid or electromagnetic forces to the rotor. Simulated aerodynamic cross coupling stiffness values are to be applied to the rotor through these two internal AMBs with the goal of developing stabilizing robust controllers. The unique design allows multiple support and disturbance locations providing the ability to represent a variety of machine configurations, e.g., between bearing and overhung designs. The shaft transfer function in lateral movement has been developed with finite element model and then verified by experimental frequency response measurements. Models for the power amplifiers, position sensors, signal conditioning and data converter hardware were developed, verified experimentally and included in the overall system model. A PID controller was developed and tuned to levitate the rotor and enable further system characterization.Copyright © 2010 by ASME

Design, Construction and Modeling of a Flexible Rotor Active Magnetic Bearing Test Rig

Considering frequency domain energy distribution differences of bearing vibration signal in the different failure
modes, a rolling bearing fault pattern recognition method is proposed based on orthogonal wavelet packet decomposition and Gaussian Mixture Model-Hidden Markov Model (GMM-HMM). The orthogonal three-layer wavelet
packet decomposition is used to obtain wavelet packet decomposition coefficients from low frequency to high frequency. Rolling bearing raw vibration signals are firstly decomposed into the wavelet signals of different frequency
bands, then different frequency band signals are reconstructed respectively to extract energy features, which form
feature vectors as the model input of GMM-HMM. A large number of samples are trained to get model parameters
for different bearing faults, then several groups of test data are adopted to verify GMM-HMMs so different fault
types of rolling bearings are recognized. By calculating the current state appearance probability of monitoring data
in GMM-HMMs, different failure patterns are recognized and evaluated from the maximum probability. Similarly,
we establish GMM-HMMs for different grade fault samples and evaluated the performance degradation state. Test
results show that the proposed fault diagnosis approach can identify accurately the fault pattern of rolling bearings
and evaluate performance degradation of bearings.

/pdf/a-fault-diagnosis-approach-for-rolling-bearing-based-on-4qp2mngr61.pdf

A Fault Diagnosis Approach for Rolling Bearing Based on Wavelet Packet Decomposition and GMM-HMM


 Despite the fact that the hydrodynamic lubrication is a self-controlled process, we designed the control systems based on PI controller, adaptive PI controller, and DQN-agent to minimize the friction torque in a conical fluid-film bearing. The bearing construction allows the shaft axial displacement and, as the result, the regulation of the bearing average clearance due to the controlled supply pressure. The main challenge is that the friction torque minimization may lead to the loss of load-carrying capacity and the contact in the shaft-bearing tribocouple. The other challenge is that random events may have an influence on the hydrodynamic lubrication parameters therefore changing the load-carrying capacity and the friction torque. So, the proposed control systems were designed and tested under the conditions of limited lateral shaft displacements and action of a random external force. The tests were performed using simulation models of a controlled rotating machine in MATLAB. The rotating machine simulation model includes modules of the rigid shaft, the coupling with linear axial reaction, and the conical bearing. The bearing module is based on the numerical solution of the generalized Reynolds equation and its non-linear approximation with fully connected neural networks. The obtained results demonstrated that the application of an adaptive PI controller or a DQN agent allows decreasing friction torque in a bearing under the conditions of a random external force. The goal of a DQN agent is self-learning in contrast to an adaptive PI controller that needs to be tuned.

Active fluid-film bearing with deep Qnetwork agent based control system

An active control method based on the proportional-derivative (PD) feedback control strategy using an active
magnetic actuator (AMA) is proposed for suppressing rotor vibration caused by rotor unbalance. The control
current of the AMA is adjusted according to the real-time displacement of the rotor through the PD feedback
algorithm to produce an electromagnetic force to reach the vibration response reduction of the unbalanced rotor.
The motion equation of the rotor-bearing AMA system is established and transformed into a state equation for
designing a control strategy based on the PD feedback. Finally, the test rig is set up and the verifications of
simulation and experiment are carried out. The simulation and experimental results show the effectiveness of the
proposed method for the suppression of the rotor unbalance vibration.

/pdf/unbalanced-vibration-response-reduction-of-rotor-using-3kzgcqofgu.pdf

Unbalanced Vibration Response Reduction of Rotor Using Active Magnetic Actuator Based on PD Control

Control of a Constrained Flexible Rotor on Active Magnetic Bearings

The invention discloses an active control method of milling chatter vibration based on an electric spindle of a magnetic suspension bearing. The method comprises the following steps: collecting a current displacement signal generated when the electric spindle has the milling chatter vibration; obtaining a state vector Q(t) formed by the displacement of the electric spindle and the speed; obtaining harmonic displacement which is shown as the formula in the description according to the electric spindle displacement [Fx Fy]T and a trigonometric function column vector phi(t); obtaining a first self-adaptive weight coefficient which is shown as the formula in the description and a second self-adaptive weight coefficient which is shown as the formula in the description; obtaining a first self-adaptive rate K1 and a second self-adaptive rate K2 according to the harmonic displacement h(t), the first self-adaptive weight coefficient lambda1 and a second self-adaptive weight coefficient lambda2; obtaining self-adaptive control current which is shown as the formula in the description according to the first self-adaptive rate K1, the second self-adaptive rate K2 and the harmonic displacement h(t); and applying the self-adaptive control current Qc(t) on a radial magnetic suspension bearing and generating corresponding magnetic field force so as to restrain the chatter vibration of the spindle. Through the active control method, the chatter vibration in the milling process is eliminated, thereby ensuring the processing quality and improving the processing efficiency.

Active control method of milling chatter vibration based on electric spindle of magnetic suspension bearing

The invention discloses an active inhibition device for high-speed milling motorized spindle cutting vibration The active inhibition device for high-speed milling motorized spindle cutting vibration comprises a maglev bearing milling motorized spindle, a frequency converter, a maglev bearing controller and an auxiliary signal processing part, wherein the maglev bearing milling motorized spindle is arranged on a milling machine and is used for machining a workpiece and inhibiting vibration; the frequency converter is connected with a motor of the maglev bearing milling motorized spindle and is used for driving the motor to rotate and controlling the motor to start and stop; the maglev bearing controller controls a radial maglev bearing in the spindle to generate magnetic field force for inhibiting the vibration of the spindle; the auxiliary signal processing part is used for conditioning signals transmitted by the components during milling The active inhibition device for high-speed milling motorized spindle cutting vibration has the advantages that the dynamic rigidity and damping of a spindle-cutter system can be greatly improved, the vibration is inhibited, and the cutting stability and efficiency are improved

Active inhibition device for high-speed milling motorized spindle cutting vibration

The utility model discloses an active inhibition device for cutting vibration of a high-speed milling electric spindle The active inhibition device for the cutting vibration of the high-speed milling electric spindle comprises a magnetic suspension bearing milling electric spindle, a frequency converter, a magnetic suspension bearing controller and a signal auxiliary processing part The magnetic suspension bearing milling electric spindle is placed on a milling machine and is used for machining workpieces and inhibiting vibration The frequency converter is connected with a motor of the magnetic suspension bearing milling electric spindle and is used for driving the motor to rotate and controlling the motor to be started and stopped The magnetic suspension bearing controller is used for controlling a radial magnetic suspension bearing in the spindle to generate magnetic field force for inhibiting vibration of the spindle The signal auxiliary processing part is used for regulating signals transmitted in the milling process of all the above parts The active inhibition device can greatly improve the dynamic stiffness and damping of a spindle-cutter system, so that the vibration is inhibited, and the cutting stability and efficiency are improved

Active inhibition device for cutting vibration of high-speed milling electric spindle

Active magnetic bearings (AMBs) are often used to mitigate vibrations in turbines, compressors, machining spindles, etc. However, rotor-AMBs are inherent open-loop unstable systems, and hence it is an urgent yet challenging task to stabilize rotor-AMBs with external disturbances. A dual-mode predictive flexible rotor controller is developed hereby for a rotorAMB system with input constraints. The method is afterwards proved to be capable of enlarging the region of attraction, and hence can effectively mitigate more-intensive vibrations excited by external disturbances, which is desirable in real applications. Finally, experiments are conducted on the rotor-AMB system to show the effectiveness of the proposed dual-mode predictive controller.

RETRACTED: Dual-mode predictive flexible rotor control for active magnetic bearings with input constraints:

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