scholarly journals Identification of Bearing Dynamic Parameters and Unbalanced Forces in a Flexible Rotor System Supported by Oil-Film Bearings and Active Magnetic Devices

Actuators ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 216
Author(s):  
Yinsi Chen ◽  
Ren Yang ◽  
Naohiro Sugita ◽  
Junhong Mao ◽  
Tadahiko Shinshi
Keyword(s):  
Variable Stiffness ◽  
Rotor System ◽  
Unknown Parameters ◽  
Oil Film ◽  
Rotor Systems ◽  
Response Characteristics ◽  
Unbalanced Force ◽  
Displacement Force ◽  
The Stability ◽  
And Control

As the rotational speed of conventional rotor systems supported by oil-film bearings has increased, vibration problems such as oil whip and oil whirl have become apparent. Our group proposed the use of active magnetic bearings (AMBs)/bearingless motors (BELMs) to stabilize these systems. In such a system, measuring the variable stiffness and damping of the oil-film bearings, the current-force and displacement-force parameters of the AMBs/BELMs, and the residual unbalanced force is necessary to satisfy the stability of the rotor system. These parameters are the foundation for the rotor dynamics analysis and optimization of the control strategy. In this paper, we propose a method to simultaneously identify the parameters of the oil-film bearings and AMBs/BELMs along with the residual unbalanced forces during the unbalanced vibration of the rotor. The proposed method requires independent rotor responses and control currents to form a regression equation to estimate all the unknown parameters. Independent rotor responses are realized by changing the PID control parameters of the AMBs/BELMs. Numerical simulation results show that the proposed method is highly accurate and has good robustness to measurement noise. The experimental results show that the unknown parameters identified by the responses generated by different controller parameters are similar. To confirm that the identification results are correct, verification experiments were carried out. The vibration amplitude of the rotor was successfully suppressed by applying a force to the rotor in the opposite direction to the residual unbalanced force. The frequency response characteristics and unbalanced responses of the rotor estimated by the values of the parameters identified show good consistency with the measured results.

Period-1 Motion to Chaos in a Nonlinear Flexible Rotor System

2020 ◽  
Vol 30 (05) ◽  
pp. 2050077 ◽  
Author(s):  
Yeyin Xu ◽  
Zhaobo Chen ◽  
Albert C. J. Luo
Keyword(s):  
Period Doubling ◽  
Rotor System ◽  
Harmonic Amplitude ◽  
Flexible Rotor ◽  
Periodic Motions ◽  
Bifurcation Tree ◽  
Rotor Systems ◽  
Saddle Node ◽  
Jeffcott Rotor ◽  
And Control

In this paper, a bifurcation tree of period-1 motion to chaos in a flexible nonlinear rotor system is presented through period-1 to period-8 motions. Stable and unstable periodic motions on the bifurcation tree in the flexible rotor system are achieved semi-analytically, and the corresponding stability and bifurcation of the periodic motions are analyzed by eigenvalue analysis. On the bifurcation tree, the appearance and vanishing of jumping phenomena of periodic motions are generated by saddle-node bifurcations, and quasi-periodic motions are induced by Neimark bifurcations. Period-doubling bifurcations of periodic motions are for developing cascaded bifurcation trees, however, the birth of new periodic motions are based on the saddle-node bifurcation. For a better understanding of periodic motions on the bifurcation tree, nonlinear harmonic amplitude characteristics of periodic motions are presented. Numerical simulations of periodic motions are performed for the verification of semi-analytical predictions. From such a study, nonlinear Jeffcott rotor possesses complex periodic motions. Such results can help one detect and control complex motions in rotor systems for industry.

scholarly journals A Novel Method for Identifying Crack and Shaft Misalignment Faults in Rotor Systems under Noisy Environments Based on CNN

Sensors ◽  
2019 ◽  
Vol 19 (23) ◽  
pp. 5158 ◽  
Author(s):  
Wang Zhao ◽  
Chunrong Hua ◽  
Dawei Dong ◽  
Huajiang Ouyang
Keyword(s):  
Signal To Noise Ratio ◽  
Principal Component ◽  
Rotor System ◽  
Fault Classification ◽  
Vibration Signals ◽  
Rotor Systems ◽  
Response Characteristics ◽  
Mode Decomposition ◽  
Shaft Misalignment ◽  
Band Limited

Crack and shaft misalignment are two common types of fault in a rotor system, both of which have very similar dynamic response characteristics, and the vibration signals are vulnerable to noise contamination because of the interaction among different components of rotating machinery in the actual industrial environment, resulting in great difficulties in fault identification of a rotor system based on vibration signals. A method for identification of faults in the form of crack and shaft misalignments is proposed in this paper, which combines variational mode decomposition (VMD) and probabilistic principal component analysis (PPCA) to denoise the collected vibration signals from a test rig and then achieve signal feature extraction and fault classification with convolutional artificial neural network (CNN). The key parameters of the CNN are optimized and determined by genetic algorithm (GA) firstly, and the domain adaptability of the trained network is verified by the signals with different signal-to-noise ratio (SNR) values; then, the noisy vibration signals are decomposed into multiple band-limited intrinsic modal functions by VMD, and further data dimension reduction is performed by PPCA to realize the separation of the useful signals from noise; finally, the crack and shaft misalignment of the rotor system are identified by the optimized CNN. The results show that the proposed method can effectively remove the interference noise and extract the intrinsic features of the vibration signals, and the recognition rates of crack and shaft misalignment faults for the rotor system with different SNR values are more than 99%, which is considered to be very effective and useful.

Stability Characteristics of Steam Turbine Rotor Seal System With Analytical Floating Ring Seal Force Model

2013 ◽  
Author(s):  
Guang-hui Zhang ◽  
Gui-long Wang ◽  
Zhan-sheng Liu ◽  
Rui-xian Ma
Keyword(s):  
Dynamic Response ◽  
Steam Turbine ◽  
Critical Speed ◽  
Turbine Rotor ◽  
Rotor System ◽  
Force Model ◽  
Oil Film ◽  
Steam Turbine Rotor ◽  
Ring Seal ◽  
The Stability

The analytical oil film force model for floating ring seal is established including the effect of axial pressure gradient. The analytical model is based on the oil lubricated Reynolds equation and the short bearing assumption, where the fluid Lomakin effect is considered. The pressure distribution of the floating ring and static characteristics is studied by numerical simulation. The three dimensional flow model is established and solved by the CFD method. By employing the finite element method, the dynamic model of the floating ring seal-steam turbine rotor system is established. The critical speed, mode shape and dynamic response of the steam turbine rotor with different bearing support stiffness are obtained. The effect of the floating ring oil film force on the critical speed and instability speed with different bearing support stiffness is studied. The effects of floating ring parameters (groove geometrical dimensions) on dynamic response are studied, and the stability of floating ring seal-rotor system with variation of the factor is analyzed. The floating ring seal can play the role of increasing the supporting effect, which will increase the critical speed of the rotor system. The floating ring seal can cause the sub synchronous vibration and the groove can significantly increase the stability of system.

Experimental Study on Vibration Properties and Control of Squeeze Mode MR Fluid Damper-Flexible Rotor System

2003 ◽  
Author(s):  
Jianxiao Wang ◽  
Guang Meng ◽  
Eric Hahn
Keyword(s):  
Vibration Control ◽  
Control Method ◽  
Rotor System ◽  
Flexible Rotor ◽  
Mr Fluid ◽  
Oil Film ◽  
Critical Speeds ◽  
Fluid Damper ◽  
Mr Fluid Damper ◽  
And Control

A squeeze mode MR fluid damper used for rotor vibration control is designed and manufactured, and the unbalance response properties and control method of a single-disk flexible rotor system supported by the damper are studied experimentally. It is found from the study that the magnetic pull force can decrease both the first critical speed and the critical amplitude; the oil film reaction force can decrease the amplitude at the undamped critical speeds, but increase the amplitude in a speed range between two undamped critical speeds. For the rotor system supported by a journal bearing and an MR fluid damper, it is possible to appear oil film instability as the increasing of the control current. The damper may have the best effect to make the vibration minimize within the range of all working speed by using on-off control method. The research show that the squeeze mode MR fluid damper has the advantages such as simple structure, clearly effectiveness, quick response, etc., and this kind of damper has a promising potential future in vibration control of flexible rotor systems.

scholarly journals Response Characteristics of Looseness-Rubbing Coupling Fault in Rotor-Sliding Bearing System

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Yang Liu ◽  
Zengyuan Xue ◽  
Lei Jia ◽  
Tuo Shi ◽  
Hui Ma
Keyword(s):  
Finite Element ◽  
Simulation Analysis ◽  
Element Model ◽  
Rotor System ◽  
Sliding Bearing ◽  
Oil Film ◽  
Response Characteristics ◽  
The Time Domain ◽  
Coupling Fault ◽  
Bearing System

For the diagnosis of looseness-rubbing coupling fault of rotor-sliding bearing system caused by bolt looseness fault, the mechanical model and finite element model of dual-disc rotor system with looseness-rubbing coupling fault are established based on the nonlinear finite element method, nonlinear oil film force, looseness stiffness model, and Hertz contact theory. With the augmented Lagrange method, contact constraint conditions are dealt with to ensure that the rotary disk and casing contact with each other meeting boundary penetrating depth within the prescribed tolerance range. And then the dynamics characteristics of the health rotor system supported by sliding bearing are studied. Combined with experimental study and simulation analysis, it is found that the looseness-rubbing coupling fault is often characterized by rubbing fault, the lower part of the time-domain fluctuated shape is denser, while the upper part is relatively loose, and multiple nested half ellipse is shown in orbit diagram. Because of the loosing stiffness and rubbing force, the phenomenon of unstable oil film is depressed. The appearance of the first- and second-order oil film oscillation phenomenon is delayed. It could be used as a theoretical basis for diagnosing looseness-rubbing coupling fault of rotor-sliding bearing system.

Distributed Measuring and Control System of Torque Rheometer

2012 ◽  
Vol 468-471 ◽  
pp. 1486-1489
Author(s):  
Peng Wang ◽  
Jian Yan ◽  
Ting Chen ◽  
Ming Li
Keyword(s):  
Control System ◽  
Pid Control ◽  
Control Algorithm ◽  
Data Link ◽  
Measurement And Control System ◽  
Response Characteristics ◽  
The Stability ◽  
Link Layer Protocol ◽  
And Control ◽  
Measurement And Control

This paper presents a new distributed control system used in torque rheometer. It can overcome shortcomings in traditional control system of torque rheometer and optimize overall performance of the system. The measurement and control system was designed by modeling method. The enhanced PID control algorithm and integration separation digital PID control algorithm were adopted to improve dynamic response characteristics. The Modbus communication protocol was selected as data link layer protocol of communications network. The monitoring software was developed by Visual Basic. A large number of experiments demonstrate that the stability of system is improved greatly and maintenance and extension of instrument become easier.

scholarly journals The Influence of Torsional-Lateral Coupling on the Stability Behavior of Geared Rotor Systems

1988 ◽  
Vol 110 (4) ◽  
pp. 563-571 ◽  
Author(s):  
P. Schwibinger ◽  
R. Nordmann
Keyword(s):  
High Performance ◽  
Coupling Effect ◽  
Practical Importance ◽  
Coupled System ◽  
Oil Film ◽  
Stability Behavior ◽  
Rotor Systems ◽  
Lateral Vibrations ◽  
Lateral Coupling ◽  
The Stability

In high-performance turbomachinery trouble often arises due to unstable asynchronous lateral vibrations. The instabilities are mostly caused by oil film bearings, clearance excitation, internal damping, annular pressure seals in pumps, or labyrinth seals in turbocompressors. In recent times as an additional influence the coupling between torsional and lateral vibrations is considered, which is of practical importance in geared rotor systems. In the literature [1, 2], some field problems are described, where in geared drive trains unstable lateral vibrations occurred together with torsional oscillations. This presentation studies the influence of torsional-lateral coupling on the stability behavior of a simple geared system supported by oil film bearings. The coupling effect is investigated by parameter studies and a sensitivity analysis for the uncoupled and the coupled system.

Investigation on the Excitation Characteristics and Dynamic Response of the Multi-Support Flexible Rotor With Misalignment

2017 ◽  
Author(s):  
Sen Xiao ◽  
FaYong Wu ◽  
YanHong Ma ◽  
Jie Hong
Keyword(s):  
Dynamic Response ◽  
High Speed ◽  
Structural Characteristics ◽  
Rotation Frequency ◽  
Frequency Component ◽  
Typical Feature ◽  
Rotor System ◽  
Flexible Rotor ◽  
Rotor Systems ◽  
Response Characteristics

Aiming at the misaligned problems of high-speed flexible multi-supported rotor system, considering the structural characteristics and load characteristics of the rotor, the unbalanced excitation of the rotor with misalignment is presented and quantitatively described. The mechanical model of the high-speed flexible rotor system with multi-support under misaligned excitation is established. Based on the finite element method, the dynamic equation of the rotor system is given and the dynamic response characteristics of rotor systems are studied. The results show that the misalignment for the highspeed multi-support flexible rotor system can not only lead to 2X excitation and support stiffness nonlinearity, but also bring additional unbalanced excitation to the rotor system. The 2X frequency component is one typical feature for the rotor system with bearing misalignment. The vibration response of the rotor showed a trend of “increased slowly first, then reduced quickly as the rotation frequency increased”, and it turns to be more obvious with the increasing of the nonlinear stiffness and unbalance.

Stability Analysis of Dual Rotor System by Extended Transfer Matrix Method

1989 ◽  
Author(s):  
K. D. Gupta ◽  
K. Gupta ◽  
K. Athre
Keyword(s):  
Transfer Matrix ◽  
Stability Criterion ◽  
Transfer Matrix Method ◽  
Matrix Method ◽  
Potential Method ◽  
Rotor System ◽  
Junction Conditions ◽  
Rotor Systems ◽  
Margin Of Stability ◽  
The Stability

This paper presents a general formulation for the stability problem of a linear model of dual rotor system with intershaft bearing(s) employing an ‘extended’ transfer matrix method [9] using complex variables. The stability criterion employed is essentially an extension of leonhard’s stability criterion. An alternative concept of ‘margin of stability’ has been suggested. In contrast to other methods, the present formulation maintains the integrity of dual rotor system in totality, by considering exact junction conditions at intershaft bearing. And it is felt that it would prove to be an potential method for analyzing the stability of complex rotor systems.

Forced Vibration of Rotor Suppressed by a Automatic Ball Balancer (Nonlinear Principal Resonances)

2013 ◽  
Vol 655-657 ◽  
pp. 551-557
Author(s):  
Xiao Long Zhang ◽  
Ya Bin Dong ◽  
Yu Min He ◽  
Mei Juan Tong
Keyword(s):  
Forced Vibration ◽  
High Speed ◽  
Rotor System ◽  
Restoring Force ◽  
Rotor Systems ◽  
Jeffcott Rotor ◽  
Rolling Elements ◽  
Rotary Speed ◽  
Nonlinear Elastic ◽  
And Control

The automatic ball balancer is equipment used to balance the rotor system online and control its forced vibration. Although the rotor system is a nonlinear system actually, especially the occurrence of the nonlinear elastic restoring force in the support of rolling elements bearings, many researches still focus on the linear rotor systems at present. The Jeffcott rotor acted by unsymmetrical nonlinear restoring force is studied in this paper. Through the resolving theoretically and simulating numerically, the principal resonance respond of the rotor system controlled by the balancer with two balls and its stability are studied, while the vibration characteristics and movement laws of the rotor and balls in every rotary speed region are analyzed. The results showed that the balancer can suppress the principal vibration of the nonlinear rotor system in high speed region very well.

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