INVESTIGATION OF SIMULATION EXPERIMENT ON ACTIVE CONTROL OF TORSIONAL VIBRATION IN A TURBOGENERATOR SHAFT SYSTEM

According to the theoretical analysis and calculation on the base of continuous mass system, the simulation experimental investigation on active control of torsional vibration in a turbogenerator shaft system is conducted. A test installation with the excitation of generator motor and multi-stepped shaft system is established to simulate the torsional vibration of a turbogenerator rotor shaft system, and to examine the active control strategy presented. Some useful results are reached in the experimental study.     

电液主动悬架灵敏度分析与自适应跟踪控制

应急救援车辆载重量大、行驶路面复杂,电液主动悬架输出力的响应和控制精度对衰减振动至关重要。建立了电液主动悬架单元数学模型,给出了系统的轨迹灵敏度方程,并得到力阶跃响应对应各主要参数的灵敏度,为悬架性能优化提供理论依据;针对电液主动悬架负载质量大的特点,结合灵敏度分析结果,设计模型参考自适应控制器。最后,通过实验对自适应控制效果进行验证,结果表明所提出的控制方法可有效提高电液主动悬架单元的跟踪性能和对输出力的控制精度,助力整车主动悬架系统实现各种先进控制算法。     

基于磁流变阻尼器的转子系统振动PID控制研究

针对大型旋转机械通过临界转速时振动过大的问题,搭建了转子实验台,在不改变转子轴系原有支撑形式的基础上,将磁流变阻尼器作为辅助机构安装在转子上,通过实验研究了阻尼器对转子振动的影响规律。提出了一种PID控制策略,设计了转子振动主动控制系统,以振动幅值为反馈参数,实时调节阻尼器电流,在线抑制转子振动。研究结果表明,该阻尼器可以有效抑制转子临界转速附近的振动,降幅可达90%;通过采用PID控制策略,可根据转子振动变化在线改变控制电流,使转子振动稳定在目标值附近,实现了转子系统开机加速过程振动的自动调控。     

基于二次型全局最优控制算法的汽轮发电机组轴系扭振主动控制模拟

把线性定常二次型全局最优控制算法与大型汽轮发电机组轴系扭振理论相结合,以减少轴系扭振能和控制源能量为优化目标,提出了大型汽轮发电机组轴系扭振的线性定常二次型全局最优控制理论,构造了汽轮发电机组轴系扭振主动控制的状态空间方程。阐述了求解离散黎卡提矩阵代数方程的非递推解法,提出利用求解哈密特矩阵特征值问题来确定二次型最优控制反馈矩阵的方法。为了考查扭振主动控制效果,编制了适用于离散系统扭振主动控制的仿真计算程序,利用所编程序对一台200 MW汽轮发电机组轴系进行了扭振主动控制模拟计算,并进行了扭振主动控制的时域特性分析。分析结果表明,采用线性定常二次型全局最优控制理论对汽轮发电机组轴系扭振进行主动控制,不但有很好的减振效果,而且所需控制力矩较小。     

周期性机械振动主动控制算法

为提高周期性机械装置的隔振性能,减少其对底座(或地面)及周围环境的影响,采用由弹性橡胶和压电堆作动器组成的主动悬置(active control mount, ACM).针对压电堆作动器输出位移较小的情况,设计液压位移放大机构.通过对压电作动器和橡胶主簧性能的分析,建立由主动悬置构成的隔振系统的力学模型.周期性机械振动系统,其周期振动信号可用作控制同步信号,因此控制系统采用基于同步滤波-X LMS(least mean square)算法的自适应控制策略,传递到机座的残余力作为误差信号,实现对周期性机械振动系统的主动控制.计算机仿真实验结果表明,采用这种主动悬置和同步滤波-X LMS算法的主动控制系统,相对于采用普通橡胶悬置的被动系统,明显减少了对底座的力传递,减振效果明显.     

Stability and dynamics of rotor system with 45° slant crack on shaft

Crack on a shaft is one of the common damages in a rotor system. In this paper, transverse vibrations are calculated to compare the influences of transverse crack and slant crack on the rotor system. Results show that the vibration amplitude of the rotor system with a 45° slant crack on the shaft is larger than that with a transverse crack when the two types of crack have the same depth and the rotor system runs in the same condition. Stability and dynamic characteristics of the rotor system with a 45° slant crack on the shaft under torsional excitation are analyzed by considering opening and closing of the crack. It is shown that the instability of the transverse vibration of the rotor system increases with increasing difference between the bending stiffness in two main directions, and the vibration is stable when the two bending stiffness are identical. The spectrum analysis of the steady-state response reveals that the gravity and the eccentricity produce different frequency components, and when the two bending stiffness are identical, the multiple frequency components of the torsional excitation disappear. Further investigation shows that the vibration amplitudes in combined frequencies increase rapidly in transversal, torsional, and axial vibration with increasing slant crack depth. The results are helpful for the understanding the dynamic behavior of a rotor system with a slant crack on a shaft and can be used for the detection of the slant crack on a shaft.     

碰摩转子弯扭摆耦合振动非线性动力学特性

为进一步提高旋转轴系的安全性,研究旋转轴系弯扭摆振动耦合振动问题.推导一般意义下,考虑陀螺力矩的单盘转子弯扭摆耦合振动非线性方程,基于该方程推出不平衡转子和碰摩转子的非线性弯扭摆耦合振动方程.应用数值方法研究碰摩转子弯扭摆耦合振动相应的复杂动力学行为,研究转子转速对碰摩转子弯扭摆耦合振动的分岔和混沌行为的影响,以及扭转振动和摆动振动对弯曲振动的影响.分析结果为转子的安全运行和弯扭摆耦合振动故障的判别提供了理论依据.     

液体动静压球轴承轴心运动轨迹研究

为研究外载荷对轴承转子系统稳定性的影响,以小孔节流的液体动静压球轴承转子系统为研究对象,建立液体动静压球轴承转子系统动力学模型。通过求解轴承润滑数学模型获得非线性油膜力,分析转子所受到的外载荷,采用欧拉算法预测出轴心下一个时刻位移、速度和加速度,并分析转子系统质量、不平衡载荷和阶跃载荷对转子回转精度的影响。结果表明：随着转子系统质量的增加,所需平衡的油膜力增加,轴心振动幅度增加,从而导致转子回转精度降低;相对于不考虑不平衡载荷,考虑不平衡载荷后其振动形态为椭圆且振动幅值增大,减小不平衡值将减小振幅并提高旋转精度;随着阶跃载荷的增加,达到平衡所需的时间也增加。     

大型汽轮发电机组转子轴系扭振弹性波的解析研究

建立了汽轮发电机组轴系的弹性连续体扭振模型,提出了求解复杂阶梯轴系扭振波动方程的解析方法。计算了一台200MW机组转子轴系扭振波动特性的精确解,并与离散系统计算结果做了比较。根据机组扭振干扰力矩的复杂性和随机性,利用该方法进行了网机耦合作用下的扭振强迫振动考核。     

一种新的转子碰摩故障诊断特征的研究

建立Jeffcott碰摩转子的弯扭耦合振动非线性微分方程，通过数值仿真手段，着重分析转子碰摩故障的扭振时频域特点及其非线性振动特性，并描述动静间隙对碰摩转子扭振非线性特性的影响。研究表明，转子碰摩激起丰富的扭振频谱信息，主要包括N/2X、N/3X等分频成分以及1X、2X等倍频成分，且分频幅值往往比倍频大许多。在一定转速范围内，周期运动与复杂的非线性运动交替出现。而动静间隙对转子扭振特性影响明显，动静间隙越小，转子动静碰摩越严重，频谱成分越丰富，运动形式更趋复杂，相应的各复杂运动区的范围也越宽。文中揭示的扭振特征为转子碰摩的状态识别与诊断提供了一种新方法。     

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。     

ZERO MODE NATURAL FREQUENCY AND NONLINEAR VIBRATION OF COUPLED LATERAL AND TORSION OF A LARGE TURBINE GENERATOR

Zero mode natural frequency (ZMNF) is found during experiments. The ZMNF and vibrations resulted by it are studied. First, calculating method of the ZMNF excited by electromagnetic in vibrational system of coupled mechanics and electrics are given from the view of magnetic energy. Laws that the ZMNF vanes with active power and exciting current are obtained and are verified by experiments. Then, coupled lateral and torsional vibration of rotor shaft system is studied by considering rest eccentricity, rotating eccentricity and swing eccentricity. Using Largrange-Maxwell equation when three phases are asymmetric derives differential equation of the coupled vibration. With energy method of nonlinear vibration, amplitude-frequency characteristics of resonance are studied when rotating speed of rotor equals to ZMNF. The results show that ZMNF will occur in turbine gen erators by the action of electromagnetic Because ZMNF varies with electromagnetic parameters, resonance can occur when exciting frequency of the     

Boundary control of an axially moving string: actuator dynamics included

In this paper, an active vibration control of a translating tensioned string with the use of an electro-hydraulic servo mechanism at the right boundary is investigated. The equations of motion of the string are derived by using Hamilton’s principle for the systems with changing mass. The control objective is to suppress the transverse vibrations of the string via a rightboundary control. An energy-based right-boundary control law, generating a specific current input to the servo-valve, is derived. It is revealed that a time-varying boundary force, as a function of the slope of the string at the right end and a suitably chosen damping coefficient of the actuator, can successfully suppress the transverse vibrations. The exponential stability of the closed loop system is proved. The effectiveness of the proposed control law is demonstrated via simulations.     

高速转子系统振动控制技术评述

高速转子系统在正常工作过程中必须通过临界转速,此时由于不平衡质量的作用,转子系统会产生共振,导致强烈的振动。降低系统支承刚度以降低临界转速、增大支承阻尼,以减小振幅,这些措施可以抑制系统通过临界转速时的振动幅值和外传力。在振动被动控制技术中,常用弹性支承和挤压油膜阻尼器、金属橡胶减振器、高聚物复合材料减振结构等,降低系统支承刚度,增大支承阻尼,以减小系统振动;在主动控制技术中,通过主动控制挤压油膜阻尼器的参数,改变支承的刚度和阻尼的大小,以控制系统的振动;以及采用形状记忆合金调节器、电磁阻尼器、压电调器等装置,来主动控制系统的振动。目前控制技术仍存在装置结构复杂、性能不稳定等问题,采用粘弹阻尼复合材料与滚动轴承钢外圈复合结构的一体化滚动轴承,足一种有发展前途的研究方向。     

齿式联接不对中转子的弯扭耦合振动特性分析

以齿式联轴器的不对中故障为研究对象,推导不对中激励力表达式,并从动力学的角度,建立不对中弯扭耦合振动微分方程。基于该微分方程,文中先从理论分析角度,定性分析弯振对扭振的影响和扭振对弯振的影响,接着从变转速过程、质量偏心、不对中量以及阻尼系数对弯扭耦合特性影响几方面进行数值仿真分析。计算表明,弯振与扭振是相互耦合的,质量偏心是耦合的前提。弯振频率包含工频和二倍频成分等,不对中越严重,二倍频所占比例越大,其轴心轨迹为双环椭圆。弯扭耦合将激发各阶谐波扭振,包括工频、二倍频和三倍频,其中工频扭振占主导地位。     

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。     

Jeffcott裂纹转子弯扭耦合振动特性分析

以重力决定的开闭裂纹模型为研究对象，导出了固定坐标系下该模型的刚度扭阵，建立了裂纹转子弯扭耦合振动微分方程，并对转子裂纹的升速瞬态响应和影响因素进行了计算机仿真研究。结果表明：升速过程中，弯振存在1／3阶和1／2阶亚谐共振现象，扭振出现1／2阶亚谐共振；在弯扭左耦合区，出现弯扭耦合共振；在亚临界转速区，存在1X，2X和3X等倍频分量的弯振和扭振；影响弯扭耦合振动特性的因素很多，包括裂纹刚度、裂纹夹角、质量偏心和阻尼等。     

发电机组橡胶柱销联轴器异常振动噪声诊断

为诊断某型柴油发电机组产生的异常噪声故障,将经验模态分解方法(empirical mode decomposition,简称EMD)和Hilbert变换用于发电机主轴承的非平稳振动信号处理,有效提取了主轴承振动信号的时频特征,对机组振动噪声信号、发电机主轴承振动和轴系扭振信号进行了分析。诊断结果表明,由于柴油机激励下机组轴系扭振幅值过大,引起柱销联轴器橡胶件表面的相对运动,产生干摩擦作用力,导致机组轴系产生间歇性的异常振动噪声。该方法对旋转轴系部件摩擦引起的振动噪声故障诊断具有参考价值。     

Coupled bending and torsional vibration of a rotor system with nonlinear friction

Unacceptable vibrations induced by the nonlinear friction in a rotor system seriously affect the health and reliability of the rotating machinery. To find out the basic excitation mechanism and characteristics of the vibrations, a coupled bending and torsional nonlinear dynamic model of rotor system with nonlinear friction is presented. The dynamic friction characteristic is described with a Stribeck curve, which generates nonlinear friction related to relative velocity. The motion equations of unbalance rotor system are established by the Lagrangian approach. Through numerical calculation, the coupled vibration characteristics of a rotor system under nonlinear friction are well investigated. The influence of main system parameters on the behaviors of the system is discussed. The bifurcation diagrams, waterfall plots, the times series, orbit trails, phase plane portraits and Poincaré maps are obtained to analyze dynamic characteristics of the rotor system and the results reveal multiform complex nonlinear dynamic responses of rotor system under rubbing. These analysis results of the present paper can effectively provide a theoretical reference for structural design of rotor systems and be used to diagnose selfexcited vibration faults in this kind of rotor systems. The present research could contribute to further understanding on the self-excited vibration and the bending and torsional coupling vibration of the rotor systems with Stribeck friction model.     

卧式车床车削振动主动控制系统设计与实验研究

分析了车削加工时振动的一般模型,并根据不同车削振动来源建立了它们各自的振动力与振动位移关系模型.针对机床运动失衡下的周期性振动,提出了一种振动主动控制方法.设计了基于PID控制算法与超磁致执行器的车削振动主动控制系统.通过数字仿真与现场试验,表明所设计的车削振动主动控制系统能有效地降低车削振动,提高车削加工精度.