A Modified Iterative Learning Control Approach for the Active Suppression of Rotor Vibration Induced by Coupled Unbalance and Misalignment

This paper proposes a modified iterative learning control(MILC)periodical feedback-feedforward algorithm to reduce the vibration of a rotor caused by coupled unbalance and parallel misalignment.The control of the vibration of the rotor is provided by an active magnetic actuator(AMA).The iterative gain of the MILC algorithm here presented has a self-adjustment based on the magnitude of the vibration.Notch filters are adopted to extract the synchronous(1×Ω)and twice rotational frequency(2×Ω)components of the rotor vibration.Both the notch frequency of the filter and the size of feedforward storage used during the experiment have a real-time adaptation to the rotational speed.The method proposed in this work can provide effective suppression of the vibration of the rotor in case of sudden changes or fluctuations of the rotor speed.Simulations and experiments using the MILC algorithm proposed here are carried out and give evidence to the feasibility and robustness of the technique proposed.

Model-Based Degree Estimation of Unbalance and Misalignment in Flexible Coupling-rotor System

The condition of rotor system must be assessed in order to develop condition-based maintenance for rotating machinery. It is determined by multiple variables such as unbalance degree, misalignment degree, the amount of bending deformation of the shaft, occurrence of shaft crack of rotor system and so on. The estimation of the degrees of unbalance and misalignment in flexible coupling-rotor system is discussed. The model-based approach is employed to solve this problem. The models of the equivalent external loads for unbalance and misalignment are derived and analyzed. Then, the degrees of unbalance and misalignment are estimated by analyzing the components of the equivalent external loads of which the frequencies are equal to the 1 and 2 times running frequency respectively. The equivalent external loads are calculated according to the dynamic equation of the original rotor system and the differences between the dynamical responses in normal case and the vibrations when the degree of unbalance or misalignment or both changes. The denoise method based on bandpass filter is used to decrease the effect of noise on the estimation accuracy. The numerical examples are given to show that the proposed approach can estimate the degrees of unbalance and misalignment of the flexible coupling-rotor system accurately.

Effectof Film Force Nonlinearity on Unbalance Responseof a Jeffcot RotorJournal Bearing System

The effect of oil film force nonlinearity on unbalance response of Jeffcot rotor elliptical bearing system is studied. Linear analysis is done by linearizing the bearing oil film dynamic forces and expressing them with stiffness and damping constants. Nonlinear dynamic simulation is done by taking the nonlinearity of bearing oil film dynamic force into full consideration, with the latter being expressed by a special database which is generated beforehand, and based on non stationary Reynolds equation and Reynolds boundary condition of film rupture. The linear and nonlinear unbalance responses of a Jeffcot rotor supported on a pair of elliptical bearings is studied. The resulting dynamic characteristics and rotor and journal whirling orbits are compared. While good consistancy between nonlinear and linear predictions is found under very small unbalance, significant or even drastic differences are found whenever the unbalance is not small, indicating the necessity of including the nonlinearity of oil film dynamic forces, especially when response to large unbalance is to be predicted.

Modeling unbalanced rotor system with continuous viscoelastic shaft by frequency-dependent shape function

A reduced-order dynamic model for an unbalanced rotor system is developed, taking the coupling between torsional and lateral vibrations into account. It is assumed that a shaft is regarded as a continuous viscoelastic shaft with unbalanced and small deformation properties. The equations of motion for the torsional and lateral vibrations are derived using Lagrange's approach with the frequency-dependent shape function. The rotor torsional vibration is coupled with the lateral vibrations by unbalance elements in a way of excitations. Simulation and experiment results show clearly that the torsional vibration has strong impact on the rotor lateral vibrations, and it causes subharmonic and superharmonic excitations through unbalance elements, which leads to the superharmonic resonances in the lateral vibrations. This model with low-order and high accuracy is suitable for rotor dynamic analysis in real time simulation as well as for active vibration control syntheses.

Optimization of Rotor Assembly Process of Rotor Initial Unbalance of an Aeroengine Gas Generator

The rotor initial unbalance of an aeroengine gas generator of turboshaft engine seriously affects rotor assembly process.To reasonably optimize rotor assembly process,the effect analyses of rotor initial unbalance of single disc and combined discs on rotor dynamic characteristics are firstly implemented in respect of the dispersity of rotor initial unbalance.It is found that the most important factors contributing to rotor vibration are the unbalances of the first stage compressor disc and the second stage turbine disc.However,reducing the mass of two discs conflicts with the control of the whole gas generator rotor balance resulting from the unbalance increase of single components.Thus,we further analyze the key control factors of affecting rotor initial unbalance,and give the strict control measures of centrifugal impeller runout in the assembly process by adjusting the angle of central tie rod axis.The purpose of this measures to make the assembly process simpler and more effective for timely controlling rotor initial unbalance.The efforts of this study validate that the proposed method is workable for the rotor tightened by a central tie rod and possesses the significant meaning of practical application in engineering.

基于加权D-S证据理论的旋翼故障诊断

旋翼作为直升机的升力面和操作面,其健康状态对直升机的安全至关重要。旋翼故障诊断技术仍是直升机健康与使用监测系统(Health and usage monitoring system, HUMS)领域的薄弱环节,开发旋翼故障诊断技术具有重要价值。基于信息融合技术,首先分析了旋翼故障的诊断机理,建立了旋翼故障模型,通过流固耦合仿真获取了不同故障下桨叶、轮毂和机身的故障特征信息,生成数据集进行网络训练和验证。然后,利用遗传算法反向传播(Genetic algorithm-backpropagation, GA-BP)优化神经网络诊断3种类型的直升机旋翼故障,即后缘调整片误调、变距拉杆误调和桨叶质量不平衡。3个逐级神经网络分别对旋翼故障类型、故障位置和故障程度进行了诊断识别。最后采用加权的Dempster-Shafer(D-S)证据理论对旋翼故障进行诊断和分析。结果证明基于改进D-S证据理论的旋翼故障诊断方法能够成功应用到旋翼故障诊断中,并具有良好的识别效果。

Study on online elimination of sudden unbalance-induced vibration using active balancing technology

An active balancing technology has been applied to solve the severe vibration caused by sudden unbalance in rotating machineries during their working process. First, based on the generation principle of sudden unbalance, a simulation test stand with a sudden unbalance generation device was set up. Then, the balancing planes were optimized by using the finite element method （FEM） to determine the position for balancing device installation. Finally, the active balancing experiments were carried out on the test stand. The experimental results indicate that the vibration response caused by sudden unbalance can be decreased from 77μm to 8μm by using the active balancing device, and the vibration amplitude reduction was up to 89.6%. From this example, it can be concluded that the active balancing device, which is installed on a proper position of the rotor, can effectively control the random transient synchronous vibration, demonstrating its high value in engineering practice.

基于改进变步长LMS算法的储能飞轮主动磁轴承-转子系统振动控制

针对储能飞轮主动磁轴承-转子系统的振动控制,在变步长最小均方差(LMS)算法的基础上采用一种改进的步长因子并对其可变参数和算法效果进行对比分析,改进算法在提高迭代收敛速度的同时还能保持一定的稳态误差。对基于有限铁木辛柯梁单元法建立的轴承-转子系统动力学模型的仿真结果表明,在转子的振动位移反馈信号进入控制器前,利用基于改进步长因子LMS算法的自适应滤波器可以有效识别并滤除与转子同频的信号分量,从而实现储能飞轮主动磁轴承-转子系统的不平衡振动控制。

SAFETY MARGIN CRITERION OF NONLINEAR UNBALANCE ELASTIC AXLE SYSTEM

The safety margin criterion of nonlinear dynamic question of an elastic rotor system are given. A series of observing spaces were separated from integral space by resolving and polymerizing method. The stable_state trajectory of high dimensional nonlinear dynamic systems was got within integral space.According to international standard of rotor system vibration, energy limits of safety criterion were determined. The safety margin was calculated within a series of observing spaces by comparative positive_area criterion (CPAC) method. A quantitative example calculating safety margin for unbalance elastic rotor system was given by CPAC. The safety margin criterion proposed includes the calculation of current stability margin in engineering. This criterion is an effective method to solve quantitative calculation question of safety margin and stability margin for nonlinear dynamic systems.

Dynamics Modeling and Numerical Analysis of Rotor with Elastic Support/Dry Friction Dampers

The elastic support/dry friction damper is a type of damper which is used for active vibration control in a rotor system.To establish the analytical model of this type of damper,a two-dimensional friction model-ball/plate model was proposed.By using this ball/plate model,a dynamics model of rotor with elastic support/dry friction dampers was established and experimentally verified.Moreover,the damping performance of the elastic support/dry friction damper was studied numerically with respect to some variable parameters.The numerical study shows that the damping performance of the elastic support/dry friction damper is closely related to the stiffness distribution of the rotor-support system,the damper location,the pressing force between the moving and stationary disk,the friction coefficient,the tangential contact stiffness of the contact interface,and the stiffness of the stationary disk.In general,the damper should be located on an elastic support which has a large vibration amplitude in order to achieve a better damping performance,and the more vibration energy in this elastic support concentrates,the better performance of the damper will be.The larger the tangential contact stiffness of the contact interface,and the stiffness of the stationary disk are,the better performance of the damper will be.There will be an optimal value of the friction force at which the damper performs best.

Numerical Calculations of Aerodynamic and Acoustic Characteristics for Scissor Tail-Rotor in Forward Flight

The aerodynamic and aeroacoustic characteristics of a scissor tail-rotor in a forward flight are numerically calculated.A novel computational fluid dynamics(CFD)model based on Navier-Stokes(N-S)equations is presented to simulate the unsteady flowfield and the aerodynamic characteristics of a scissor tail-rotor in the forward flight.Then the Farassat Formulation 1 Aderived from the FW-H equation is coupled into the CFD model in order to compute the aeroacoustic characteristics of the scissor tail-rotor.In addition,two different scissor tail-rotor configurations,i.e.,the L-and U-configuration,are analyzed in details and compared with a conventional one.The influence of scissor angles on the aerodynamic and aeroacoustic characteristics of the scissor tail-rotor is also investigated.The simulation results demonstrate that the flowfield,aerodynamic force and aeroacoustic characteristics of a scissor tail-rotor are significantly different from the conventional one,and the aerodynamic interaction decreases with the increase of scissor angle,which leads to a reduction of amplitude variation of the tail-rotor thrust in the forward flight.The scissor angle has an important effect on the aerodynamics and aeroacoustics of the scissor tail-rotor.

For Propulsion Applications It Is Possible to Utilize Both the Torque Output of the Rotor and the Reactional Torque Acting on the Stator of the Driving Electric Motor by Linearizing the Stator

This paper presents a novel idea of utilizing the reactional torque of the conventional electric motor as a linear output for propulsion in addition to the conventional torque output of the rotor. The idea is demonstrated by a theoretical proposal of linearizing the stator of one of the most used motors in Electrical Vehicles and Hybrid Vehicles. The proposed Linear Stator Motor is a simple modification without involving any functional change of the conventional motor. Though theoretical, the indicated possible input energy saving of more than 75% as compared to the conventional motor is no surprise, as by linearizing the stator, an almost equal linear propulsion output is added to the conventional rotor output. In addition to this remarkable saving in input energy, the proposed Linear Stator Motor that suits all types of vehicles, can maintain propulsion without the need for a mechanical transmission system. Also, in the case of watercraft and aircraft vehicles, no external mechanical propulsion drive system is required. It is just an internal force that can push the vehicle forward, backward, or laterally, while the conventional rotor output can be utilized for energy recovery by driving a DC generator.

Dynamic Behavior of a Brushless in Runner Motor

In this article, a model of a rotor with an asymmetric disk is presented in order to represent Campbell’s diagrams and instability maps as a function of the rotations of the support which can significantly change the dynamic behavior of the rotor. Critical rotating speeds can also lead to unacceptable levels of vibration. Indeed, the critical speeds are a function of the dynamic rigidity of the rotating systems and the presence of the gyroscopic forces creates a dependence between the rotating speed of rotation and the natural frequencies to such structures (the CAMPBELL diagrams): this implies that the correct determination of the critical speeds is one of the essential elements when sizing such dynamic systems.

基于二维CNN与多源机电信息融合的同步电机转子匝间短路故障诊断方法

为提高同步电机转子绕组匝间短路故障的诊断准确率,以一台型号为SDF-9的一对极同步发电机为研究对象,提出了一种基于二维卷积神经网络(Convolutional Neural Networks, CNN)与多源机电信息融合的匝间短路故障诊断方法。首先选取故障前后的定子环流、转子振动、定子振动信号为故障特征,采用信号-图像转换方法将一维时序信号转化为二维灰度图像。其次将处理后的图像分别作为二维CNN模型的前置输入进行训练。最后采用D-S证据理论将3种证据体的输出概率进行决策融合。结果表明:该方法消除了单一信号易受传感器故障及环境变化的影响,故障诊断准确率显著提高,并与其他传统故障诊断算法的诊断结果进行对比分析,验证了此方法的有效性。

突加不平衡下GTF发动机转子系统瞬态响应分析

针对GTF发动机低压转子系统突加不平衡瞬态响应问题,基于有限元法建立了考虑啮合单元、行星架单元、膜盘联轴器单元的多体接触、多转子耦合动力学模型,介绍了考虑非线性因素下突加不平衡瞬态响应计算方法,求解了低压转子系统的突加不平衡瞬态响应,并分析了关键部件刚度对突加不平衡的影响规律。结果表明:当风扇转子发生突加不平衡时,各部件均表现为振动幅值突增,后迅速趋于稳定,低压涡轮转子发生明显拍振,突加不平衡载荷主要由行星架结构和第1.5支点刚性支承承担;行星架刚度主要影响风扇转子突加不平衡响应、第1.5支点和行星架处的外传力;膜盘联轴器刚度主要影响增压级突加不平衡响应、转子在突加不平衡之后稳定运转情况。

基于ANSYS的转子系统不平衡响应分析

通过对某离心机转子系统进行受力分析,得到可以计算的数学模型。利用有限元分析软件AN-SYS建立其有限元模型,获取不同工况下的不平衡响应曲线、峰值和共振频率。通过分析可知在目前使用工况下工作转速低于一阶临界转速,转子主轴属于刚性转子。离心机不平衡响应大小受转速、激振力、每组筒体配重差等因素影响,动平衡研究主要是解决粉体压缩导致的非线性激振力和转子转盘的平衡问题。为未来新的离心机转子系统研发设计提供了一定的理论参考依据。

纵列式及横列式双旋翼流动的N-S方程模拟及气动特性的研究

通过求解带动量源项的Ｎ－Ｓ方程，模拟了纵列式和横列式双旋翼的流动，给出了两旋翼相互干扰时的流场，特别是桨盘处的下洗速度分布；通过与单旋翼下洗速度分布的比较，分析了双旋翼流场的干扰特性；讨论了此２ 种双旋翼的气动性能。

立式离心泵典型故障复现试验研究

为了给立式离心泵的故障诊断提供试验和理论依据,搭建立式离心泵仿真试验台,进行立式离心泵典型故障的仿真复现试验,分析了转子不平衡、转子不对中和支座连接松动等故障的振动特性及其频谱特征.结果表明:机脚处的振动位移信号对支座连接松动故障的振动特性敏感性更高,轴系的振动信号对转子故障的振动特性敏感性更高;转子不平衡故障和转子不对中故障表现出不同的频谱特征,转子不平衡故障的频谱特征表现为1倍振动主要频率(amplitude power frequency,APF)幅值增大,且随着故障程度的增加,幅值呈现了逐渐减小的趋势,转子不对中故障的频谱特征表现为产生新的振动特征频率2APF,且随着故障程度的增大,信号幅值逐渐增大;支座连接松动故障表现为频谱图中的主频变为3APF,并出现新的2APF和1/2分数谐波频率.

S形转子连续混炼机混炼段流场的有限元分析

文中利用有限元软件ANSYS对S形转子连续混炼机的流场进行了模拟分析。研究了转子的不同相位和操作条件的改变对速度场和压力场的影响规律 ,可为这种新型设备在混炼加工领域的应用提供理论指导。

EAST低温系统氦透平膨胀机转子剩余不平衡量实验研究

EAST氦低温系统的氦透平膨胀机启动过程不稳定,主要表现为气体轴承失效,转子动平衡实验时,剩余不平衡量过大。采用软支撑动平衡机对氦透平膨胀机的转子进行动平衡实验,通过转子动平衡去重,降低了转子剩余不平衡量,提高了转子动平衡精度。针对软支撑动平衡机存在的低速动平衡精度不高的问题,在低速动平衡的基础上进行了全速动平衡实验,进一步降低了转子的剩余不平衡量,提高转子动平衡精度,降低了转子对气体轴承的要求,保证了氦透平膨胀机的稳定运行。