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多个磁悬浮轴承支承的转子系统,由于支承位置的不对中会造成各个轴承的支承载荷变化。针对某一转子模型,分析采用不同个数的磁悬浮轴承支承时,各个支承载荷随着支承位置不对中的变化情况,并在三个磁悬浮轴承转子系统中得到验证。针对转子动力学特性,分析了支承高度不同时,转子固有频率的变化。此外,采用传递矩阵法,分析转子随着支承个数的增加,其不平衡响应变化情况,并实验对比了采用三支承和两支承时,转子的振幅。三支承较两支承,转子振幅有所减小。 相似文献
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基于最小二乘法的转子不平衡振动信号的提取 总被引:1,自引:0,他引:1
不平衡振动是旋转机械失效的重要原因,实现精确平衡必须从强噪声中提取出与主轴转速同频的不平衡量振动信号,因此,不平衡振动信号的准确提取是进行转子动平衡的前提。基于最小二乘法的原理,通过建立提取转子振动不平衡信号的数学模型,提出了一种准确提取转子不平衡振动信号的方法。基于该方法,并通过Matlab仿真分析,有效提取了转子振动不平衡信号。研究表明,基于最小二乘法的转子振动不平衡信号提取方法能够准确提取转子不平衡振动的幅值和相位信息,该方法可用于转子不平衡振动监测及动平衡等方面。 相似文献
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Dynamic characteristics of rotor dynamic systems, namely natural frequencies, damping and mode shape, vary with rotation speed due to gyroscopic effect. To consider such effect, modal analysis is required to be performed while in operation. However, to generate the frequency response functions, it is not viable to perform data reduction in frequency domain as noise and harmonics excited by rotating forces dominate the spectrum and hide the natural frequencies. The full set of dynamic characteristics is difficult to obtain. A novel technique, referred to as Impact-Synchronous Time Averaging (ISTA), is developed in this study to screen out the noise and harmonics. 相似文献
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For a Jeffcott rotor system with a 45° slant crack on the shaft, the motion equations are established with four directions, i.e. two transversal directions, one torsional direction and one longitudinal direction. It can be seen from the deducing process of the stiffness with the strain energy release approach that there are coupling stiffnesses of bending–torsion, bending–tension and torsion–tension for the slant-cracked shaft and only bending–tension for the transverse-cracked one. The paper shows that besides the coupling stiffnesses, there is bending–torsion coupling caused by the eccentricity. All these couplings affect the responses of the slant-cracked shaft and the transverse-cracked one. Comparing responses of a cracked shaft with an open crack model and those with a breathing crack model finds that there are the same prominent characteristic frequencies for these two kinds of shafts, even though the cracked shaft with a breathing crack model behaves much more non-linear than that with an open crack model. Therefore, almost all studies in this paper adopt the open crack model since it needs taking much longer time to compute responses of a breathing cracked shaft than that of an open cracked shaft. Analyses of steady responses indicate that the combined frequencies of the rotating speed and the torsional excitation in the transversal response and the frequency of the torsional excitation in the longitudinal response can be used to detect the slant crack on the shaft of the rotor system. 相似文献
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Chong-Won Lee Yeo-Kwon Yoon Ho-Seop Jeong 《Journal of Mechanical Science and Technology》1997,11(2):155-163
The tool axis misalignment, which causes machining inaccuracies in an active magnetic bearing (AMB)-spindle system, can be
compensated by tracking control of the rotor-spindle. The pseudo-derivative feedback (PDF) control scheme alone does not correct
the tool axis misalignment since the integral action results in the narrow bandwidth and large phase lag in the controlled
system. To improve the tracking performance, the feedback and feedforward controllers are combined with the existing proportional-derivative
controller, which stabilizes the inherently unstable AMB-spindle system dynamics. The theoretical and experimental results
show that proposed control scheme efficiently compensates the tool axis misalignment compared with the conventional PDF control
scheme. 相似文献
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Effects of cracks on rotor system instability 总被引:4,自引:0,他引:4
The stability threshold of a rotor-bearing system having a transverse crack has been studied by using FEM and considering the various crack parameters and shaft internal damping (viscous and hysteretic damping) and geometric parameters. It has been observed that the instability speed has reduced considerably with increase in crack depth and influenced more with hysteretic damping compared to viscous damping. The stability of the rotor system including shaft with two open cracks has also been carried out and observed the influence of one crack over the other for threshold speed limits. 相似文献
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A novel nonlinear model of rotor/bearing/seal system based on the Hamilton principle is proposed for steam turbine systems in power plants. The Musznyska model and unsteady bearing oil-film force model were applied to describe the nonlinear steam excitation force and oil-film force. The Runge-Kutta method was used to solve the motion equation of the rotor/seal/bearing system. The dynamic characteristics of the rotor/bearing/seal system were analyzed with bifurcation diagrams, time-history diagrams, trajectory diagrams, Poincare maps and frequency spectrums. The numerical analysis indicates that the seal force and the oil-film force influence the nonlinear dynamic characteristics of the rotor system. With the increase of rotation speed, the rotor system exhibits rich forms of periodic, double-periodic, multi-periodic, quasi-periodic and chaotic motion. The combined impact of steam excitation force and bearing oil-film force may cause a severe vibration which seriously affects the safety and stability of the rotor. The presented model provides a theoretic foundation for further research on the ultra-supercritical steam turbines. 相似文献
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Nonlinear dynamic characteristics of geared rotor bearing systems with dynamic backlash and friction 总被引:4,自引:0,他引:4
Effects of the friction and dynamic backlash on the multi-degree of freedom nonlinear dynamic gear transmission system, which incorporate time varying stiffness, are investigated. Firstly, the relationship between gear central distance error and backlash is deduced and the dynamic backlash is defined, subsequently a multi-degree of freedom nonlinear dynamic gear transmission system is developed with dynamic backlash, friction and time varying stiffness. The nonlinear dynamic system is solved by the Runge-Kutta method. The results show that the friction force may enlarge the displacement magnitude and affect the high frequency parts significantly in frequency domain at low speed. But the RMS of the steady response is reduced on the effect of friction. The difference between the constant backlash and the dynamic backlash models is also discussed. The system may enter into previous chaotic motion due to the effect of dynamic backlash. Finally, no impact motion, single-side impact motion and double-side impact motion are also predicted in the new dynamic backlash model. 相似文献
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Radoslav Tomovic Aleksandar Miltenovic 《International Journal of Mechanical Sciences》2010,52(9):1176-1185
Rolling element bearings appear in nearly 90% of all rotating machinery. Their dynamic performance is often the limiting factor in the performance of the machines that use them. The specific construction of a bearing has a decisive influence on its dynamic behaviour. The paper defines a new vibration model of a rigid rotor supported by rolling element bearings. By application of the defined model, the parametric analysis of the influence of internal radial clearance value and number of rolling elements influence on rigid rotor vibrations in unloaded rolling element bearing was performed. The defined vibration model and parametric analysis were verified experimentally. The results of experimental analysis are also presented in this paper. 相似文献
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Model validation and controller design for vibration suppression of flexible rotor using AMB 总被引:1,自引:0,他引:1
Soo Jeon Hyeong-Joon Ahn Dong-Chul Han 《Journal of Mechanical Science and Technology》2002,16(12):1583-1593
This paper discusses the model validation and vibration suppression of an AMB flexible rotor via additional LQG controller.
The main difficulty in the vibration suppression of the flexible rotor using AMB is to realize a controller that can minimize
resonance without injuring the stabilized rigid modes. In order to solve this problem, simple scheme for system modeling and
controller design are developed. Firstly, the AMB flexible rotor is stabilized with a PID controller, which leads to a new
stable rotor-bearing system. Then, authors propose the model validation procedure using measured open-loop frequency responses
to obtain an accurate model of the AMB flexible rotor system. After that, LQG controller with modal weighting is designed
to suppress resonances of the stable rotor-bearing system. Due to the poor controllability and observability of flexible modes
compared to rigid ones, balancing of two Gramians is prerequisite for the fair LQG controller design. Simulation with step
disturbance and experimental results of unbalance response up to 10,000 rpm verified the effectiveness of the proposed scheme. 相似文献
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Of recent years, a series of researches have shown that a circumferential feeding groove of squeeze film damper (SFD) has evident effect on fluid film forces in SFD. Therefore, the feeding groove also affects dynamic responses of a rotor in SFD. Present work studies the effect of the feeding groove on unbalance response of a flexible rotor in SFD based on new film force models that include effects of the feeding groove and fluid inertia on dynamic characteristics of the fluid film in SFD. Compared with the published work, unbalance responses predicated under considering effect of the feeding groove on the dynamic characteristics in SFD are small, and rotor speed region for unbalance responses with multiple solutions is different, affecting the stability of a rotor system. And the effect of the feeding groove on the unbalance response is related to action of fluid inertia. 相似文献
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本文讨论了具有两个动力缓冲器的可变阻抗滑动轴承的动力学系数及其计算方法,建立了基于Reynolds方程和流量连续性原理的油膜压力分布理论模型,并提出了这种轴承油膜的线性动力学系数计算的压力扰动法。理论分析结果表明这种轴承可以在运行条件下有效地改变其油膜的动力特性,为这种轴承的实际应用提供了必要的理论基础。 相似文献
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