电磁辅助支承的变刚度减振研究

对一种新型支承结构——电磁辅助支承的变刚度减振进行研究。电磁辅助支承的结构类似挤压油膜阻尼器,它直接将电磁执行器安装在主支承上,通过控制电磁执行器的电流可以改变整个支承的刚度和阻尼。该支承被应用于一单圆盘对称转子实验系统。通过对转子系统建模,仿真不同支承刚度下转子的振动响应,从而可采用变刚度来保证高速转子以较低的振幅平稳度过临界转速。实验结果证明在一阶临界转速附近,可取得70％的较好减振效果。     

电磁辅助支承被动阻尼减振与主动阻尼减振的比较

对基于电磁执行器的一种新型支承结构--电磁辅助支承的被动阻尼减振和主动阻尼减振进行比较.首先通过各自的数学模型分析其阻尼减振的不同机理,然后在一四自由度电磁辅助支承转子系统中进行验证,并取得较好的实验效果.通过比较可知,在被动阻尼控制中电磁执行器仅提供负的动刚度和随转速变化的动阻尼;而主动阻尼控制则可以根据需要提供正负刚度和固定或变化的阻尼;且在相同的静态励磁电流下,主动减振效果优于被动减振,但前者结构复杂,造价较高,而后者实施容易.     

基于电磁辅助支承的不对中在线补偿系统

引入一种可在线调节转子轴位置的支承结构——电磁辅助支承,它通过控制电磁执行器线圈中的电流来调整整个转子轴在空间的位置,使转子系统轴系间的不对中消除。将不对中引起的附加振动视为干扰量,针对它采用具有自学习功能的前馈控制方法,使得转子在不停车的情况下自动实现不对中的识别和控制。最后在单盘对称转子轴承系统上进行了试验验证,试验结果证明该控制方法对轴系间的不对中具有较好的校正能力。     

电磁轴承-无轴承电机系统在转子主动控制的应用研究

主动磁轴承借助电磁力来控制转子的振动,无轴承电机在实现转矩控制的同时实现电机的悬浮控制。本文在对永磁偏置三自由度电磁轴承和两自由度无轴承电机的磁悬浮机理一般性描述的基础上,分析了其产生的悬浮控制力。并以转子电磁振动为研究对象,结合电磁轴承和无轴承电机的特点,提出利用一种新型的五自由度磁悬浮异步电机作为执行机构对转子电磁振动进行主动控制,实现了转子系统稳定工作。此系统可以有两方面的应用,既可以用做转子的支承,也可以用做转子振动主动控制的增稳。     

移动载体上电磁轴承-转子系统的基础激励振动主动抑制

安装在移动载体上的电磁轴承-转子系统往往会受到来自其承载基础的振动激励干扰。对单自由度支承模型和多自由度转子模型在基础激励条件下的动力学响应进行比较分析,认为可以将基础激励引起的电磁轴承-转子系统定转子之间的相对运动等效为一个由基础加速度决定的强迫振动。提出一种基于基础加速度信号作为参考信号的自适应滤波器的电磁轴承-刚性转子系统基础激励响应抑制方法,并分析该方法抑制各种类型振动的有效范围,所需滤波器的阶数,以及滤波器自适应收敛的最佳权值。在电磁轴承-转子系统试验平台上进行试验,结果表明提出的控制方法对稳定的基础激励造成的转子振动响应能有效抑制,强制定转子间隙保持稳定,避免碰撞。     

转子在线自动平衡研究

研究了转子在工作转速下实现在线自动平衡的方法。以电磁执行器作为施力装置,运用傅里叶分析和线性系统的叠加原理,对不停车的情况下转子不平衡振动的识别和抑制的算法进行了推导,并在一滚珠轴承支承的转子系统上进行了试验研究。结果证明该方法和装置能够使旋转工作频率下转子的不平衡振动大大减小。     

电磁辅助支承的被动式减振研究

结合电磁轴承的原理和结构以及旋转机械的减振理论，提出一种新型结构的支承。它将电磁轴承安装在主支承上，由主支承提供主刚度，而电磁执行器则根据需要提供附加的阻尼和刚度。对其被动式减振机理进行了研究，建立了恒压源式被动控制模型。其中支承中的电磁执行器利用直流电励磁，产生被动阻尼和刚度，阻尼值的大小由励磁电压的大小决定。该支承结构应用于实验转子系统，取得了较好的减振效果。     

多跨转子系统多频传递力变步长神经网络控制

转子在旋转过程中,转子上的各种激励力会通过轴承传递给基础,从而导致基础的振动.为了抑制多频传递力,提出一种基于跟踪滤波后轴颈位移和传递力误差信号的变步长神经网络算法.设计一种集电磁执行器与固定瓦滑动轴承于一体的混合支承结构,并建立其动力学模型.用有限元法建立多跨转子系统的动力学模型,分析传递力控制的基本原理,采用离散跟踪微分器和状态观测器分别解决位移信号夹杂白噪声不易微分和传感器与执行器不同位时执行器位置处轴颈位移的重构问题.提出一种能够抑制多跨转子系统多频传递力的变步长神经网络算法.以一个四轴承二跨转子系统的仿真模型为例进行仿真分析,对所提出的变步长神经网络算法抑制双跨转子系统传递力的有效性进行了验证.结果表明,变步长神经网络算法能够有效地抑制转子系统对基础的多频传递力.     

电磁辅助支承恒压源与恒流源被动式减振之比较

对电磁辅助支承的两种被动减振类型(恒压型和恒流型)进行研究,建立了各自的数学模型,揭示了它们不同的减振机理:在恒压源被动减振控制情况下,电磁辅助支承中的电磁执行器不仅提供与转速无关的负的静态位移刚度,而且提供随转速变化的附加(正)刚度和(正)阻尼;而在恒流源被动减振控制下,线圈中的电流保持恒定, 电磁执行器仅提供不随转速变化的负的静态位移刚度。最后在一对称转子系统上进行了试验验证,并取得了较好的减振效果。     

主动电磁轴承转子系统振动模态的分析研究

概要介绍了电磁轴承支承下多质点柔性转子振动模态计算分析方法 ,对一套低温制氧高速透平膨胀机的电磁轴承转子系统的振动模态进行了分析 ,阐述了电磁轴承转子系统振动模态与传统油膜轴承转子系统振动模态的不同之处 ,指出了振动模态分析对电磁轴承系统传感器安装位置设计的重要性 ,及传感器安装位置的设计原则。     

600MW汽轮机组大型转子-轴承系统非线性动力学分析

针对600 MW汽轮发电机转子-轴承系统,采用ANSYS计算了转子固有频率,分析其振动特性。建立了具有1 016个自由度的非线性振动方程,并基于固定界面模态综合法降维至34个自由度。分析了转子稳定性随转子偏心距、轴承间隙和润滑油动力黏度的变化规律,并利用三维谱图分析了不平衡力和重力对油膜失稳的影响。     

基于遗传算法的多自由度非线性振动的模糊控制方法

由于非线性系统的复杂性,难以得到基于线性控制规律的有效控制方法。本文对于复杂的多自由度非线性振动系统提出了基于遗传传算法的主动模糊控制方法。     

Nonlinear Dynamic Response of Cylindrical Roller Bearing–Rotor System with 9 Degree of Freedom Model Having a Combined Localized Defect at Inner–Outer Races of Bearing

This article presents a nonlinear dynamic model for a cylindrical roller bearing–rotor system with interaction forces between the inner race, outer race, and roller. Roller–race contacts are modeled predicting nonlinear stiffness (Hertz contact theory) and nonlinear damping for a rotor–cylindrical roller bearing system. Here a shaft–rotor bearing system is modeled with 9 degrees of freedom with one defect on the inner race and one defect on the outer race for a case of combined localized defects. In the mathematical formulation, contacts between rolling elements and inner and outer races are considered as nonlinear springs and nonlinear damping is taken into consideration. Contact force calculations with nonlinearity are solved using the Newton-Raphson method for n unknown nonlinear simultaneous equation. The Newmark-β implicit integration technique coupled with the Newton-Raphson method is used to solve the differential equations. The results are obtained in the form of a time domain plot, frequency domain plot, and phase plot/Poincare map. The validity of the proposed model is compared with experimental results. A bifurcation graph of speed versus peak amplitude predicts the behavior of the system.     

用形状记忆合金弹簧主动控制转子振动

选择形状记忆合金（shape memory alloy,SMA）制作的弹簧元件作为转子系统的弹性支承，研究对转子振动的主动控制。利用SMA近似的应力－应变－温度的多项式模型，推导出SMA弹簧的非线性恢复力模型。运用简化的势和学模型，建立SMA弹簧的温度控制系统，以电流加热的方法改变SMA的温度。在数值仿真中，设计了给定温度曲线，计算出电流功率，并验证了改进后系统的振动抑制效果。仿真结果表明该方法能将转子最大振幅减少30％以上。     

Stability analysis of a rotor bearing system due to surface waviness and number of balls

In the paper, the stability analysis of a rigid rotor supported by ball bearings has been studied. In the analytical formulation, the contacts between balls and races are considered as nonlinear springs, whose stiffnesses are obtained by using Hertzian elastic contact deformation theory. The implicit type numerical integration technique Newmark-β with Newton–Raphson method is used to solve the nonlinear differential equations iteratively. The effects of surface waviness and the varying number of balls on stability of rotor bearing system are observed. All results presented in form of fast fourier transformations show that the vibration characteristics of the rotor and its bearings change, when the bearings operate in different regions of their nonlinear load deflection characteristics. From the analysis, it is implied that the number of balls and number of waves in the ball bearing are two important governing parameters affecting its dynamic behavior.     

椭圆轴承-转子系统失稳运动数值分析

滑动轴承油膜力是一种强非线性作用力,滑动轴承转子系统是一种典型的非线性动力系统,传统的线性方法无法计算系统失稳后的运动。文中给出用数值积分瞬态模拟对轴承－转子系统非线性振动进行计算分析的方法,并以椭圆滑动轴承－刚性转子系统为例,对系统失稳后的运动状态进行了计算和分析。     

A novel nonlinear model of rotor/bearing/seal system and numerical analysis

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.     

Characteristics analysis of aero-engine whole vibration response with rolling bearing radial clearance

For the influence of rolling bearing radial clearance on the whole vibration in the aero-engine whole system, a real engine rotorbearing- casing whole model is established. The rotor and casing systems are modeled by means of FEM; the support systems are modeled by lumped-mass model; rolling bearing radial clearance and strong-nonlinearity of Hertz contact force at four different supports are considered. The coupled system response is obtained by the numerical integral method. The characteristics of the whole vibration response are analyzed. For rolling bearing at a typical support, the rotor, outer ring of rolling bearing and casing response characteristics at different rotating speeds are analyzed. The changing law of contact forces for each ball and the global contact forces at different speeds are analyzed. The influence of the radical clearance on the contact forces on the whole vibration is analyzed. The results show that the contact forces will be larger and the acceleration amplitude jumps obviously when the radial clearance is increased, and due to the variable stiffness of the rolling bearing, the natural frequency will appear when the stiffness changes fiercely, that is frequency-locked phenomenon. When the radical clearance is larger and the rotating speed is between two critical speeds, the rotor squeezes the outer ring now and then. Reducing the radical clearance can reduce the whole vibration and increase the rotor’s stability.