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.     

车辆发动机悬架系统现状与进展

理想的发动机悬架系统应隔离发动机工作转速范围内由发动机干扰力所引起的发动机振动，并阻止由冲击而激起的发动机弹跳，这意味着发动机悬架的动态刚度和阻尼是与频率和振幅有关的，改善依赖于频率和振幅特性的动态刚度与阻尼是发动机悬架系统发展的关键所在。传统的弹性悬架不能满足所有的要求，它仅能在静偏转和隔振之间进行折衷，特别在低频域，被动的液压悬架能比弹性悬架提供更好的特性，通常半主动技术，由于其可调性而被用来进一步改善液压悬架的特性，为了隔振、低频时主动发动机悬架系统非常硬，而在高频域内被调整的非常软，主动的发动机悬架已被认为是发动机悬架的新一代，发动机悬架系统的优化是相当可取的，但发动机悬架的优化工作出现一些局限性，文中综述国内，外发动机悬架技术的现状与进展。     

同轴式微速差双转子系统整机动平衡方法研究

同轴式微速差双转子系统的不平衡振动信号是由内、外转子各自不平衡振动叠加而成的拍振,通过研究拍振波形的特征,提出不通过解拍,有效分离内、外转子各自不平衡振动响应的方法;通过理论分析和试验研究发现内、外转子不平衡振动之间的相互影响很小,提出用8影响系数法实现该类转子动平衡的方法。通过对双转子系统进行外转子单独平衡和内、外转子同时平衡的成功实践,证明8影响系数法能在保证足够高的平衡精度下,快速、高效地解决同轴式微速差双转子系统的动平衡问题,具有十分重要的工程应用价值。     

Application of computed order tracking, Vold-Kalman filtering and EMD in rotating machine vibration

This paper presents a study on rotating machine vibration signals by using computed order tracking, Vold-Kalman filtering and intrinsic mode functions from the empirical mode decomposition method. Through the sequential use of intrinsic mode function and order tracking methods, both speed synchronous and non-synchronous vibrations that modulate orders in rotating machine vibrations are distinguished, which is difficult when using each of the techniques in isolation alone. Simulation and experimental studies demonstrate the ability of extracting vibrations that modulate order signals through combining the techniques.     

空气弹簧液压悬置动特性及隔振特性研究

研究了具有可变刚度阻尼的发动机空气弹簧液压悬置的动特性和隔振特性。针对影响发动机空气弹簧液压悬置动特性的关键参数上液室等效体积刚度,采用理论和试验方法研究了上液室等效体积刚度的等效值,基于该等效值建立了空气弹簧液压悬置的理论模型,对空气腔开闭两种工况进行了空气弹簧液压悬置动特性的仿真和试验研究。搭建了发动机空气弹簧液压悬置系统试验台架,研究了台架各种激励频率下的空气弹簧液压悬置的隔振特性。结果表明:本研究采用的上液室等效体积刚度进行空气弹簧进行建模是正确、可行的,提高了空气弹簧建模效率和准确性;空气弹簧液压悬置在空气腔开启和关闭两种状态下,峰值动刚度增大幅值达78.5%,峰值阻尼角增大幅值达250%。台架试验表明:当台架激励频率小于25Hz时,悬置采用大刚度大阻尼;当台架激励频率大于等于25 Hz时,悬置采用小刚度小阻尼;悬置隔振率提升明显,不同频率下提升幅值达10%～67%。     

MODELING AND EXPERIMENTAL STUDY OF A PASSIVE HYDRAULIC ENGINE MOUNT WITH INERTIA AND DIRECT-DECOUPLER

To investigate the dynamic characteristics and damping theory of the passive hydraulic engine mount （PHEM）, numerical prediction is performed through lumped parameter model. System parameters, including volume compliance of the decoupler chamber, effective piston area, fluid inertia and resistance of inertia track and direct-decoupler, are identified by means of experiments and finite element method （FEM）. Dynamic behaviors are tested with elastomer test system for purpose of validating PHEM. With incorporation of inertia track and direct-decoupler, PHEM behaves effective and efficient vibration isolation in range of both low and high frequencies. The comparison of the numerical results with the experimental observations shows that the present PHEM achieves fairly good performance for the engine vibration isolation.     

基于瑞利法的内燃机曲轴扭纵耦合振动

采用瑞利法对高速内燃机曲轴扭纵耦合振动进行了研究。将内燃机曲轴等效为连续分布阶梯轴模型,根据当量轴段以及集中质量的动能和势能关系,通过拉格朗日方程分别建立轴系扭振模型和纵振模型。根据刚度耦合原理,并考虑轴系强迫激励进而建立了扭纵耦合强迫振动模型。采用谐次分析法对模型求解后,通过与采用三维振动测量装置对某直列四缸柴油机曲轴自由端的振动信号进行实际测量所得到的结果进行比较,可以发现,扭振和纵振与实际测量的结果在各主要谐次都保持相当的一致。     

Investigations of the torsional vibrations of a shaft with disks

Investigations of the direct and inverse spectral problems of torsional vibrations of a shaft with disks were performed. The Tolle method was used to solve the direct problem. The influence of the characteristics of a shaft with loads on the frequencies of its torsional vibrations was studied using the solution of the direct problem. It was shown that an increase in the moments of inertia of disk masses leads to a decrease in vibration frequencies and that an increase in the torsional rigidity of segments of a shaft leads to an increase in the system’s vibration frequencies. Examples, tables, and plots of the corresponding dependences are presented.     

遗传算法在柔性转子动平衡中的应用

现行的柔性转子动平衡技术离不开多次添加试重加起车，通常的无试重平衡法存在着过多的假设和对轴承先验知识的依赖，限制了其在工厂中的应用。通过建立以轴承参数和不平衡量的输入、轴承处振动响应为输出的系统模型，利用遗传算法逆向求解出不平衡量。藉此，料可大致了解旋转机械处于运行状态时轴承的参数和工作状态。     

Large displacement analysis of elastically constrained rotating disks with rigid body degrees of freedom

A central aspect of the linear vibration theory of rotating disks involves the concept of critical speeds. At such rotation speeds an axisymmetric disk can support a standing wave as recorded by a stationary observer. In such situations an applied space fixed constant force can give rise to a resonance in the disk. Such a response is of concern in industrial applications as diverse as circular saw blades and computer floppy disks. In such situations the magnitude of response may exceed the limits of linear theory. The present paper is concerned with the effects of large displacements upon the disk response in the neighborhood of such critical speeds. The effects of geometric nonlinearities and the influence of rigid body tilting and translation (caused by the boundary conditions) are considered. The equations of motion are based on Von Karman plate theory. The eigenfunctions of two self-adjoint eigenvalue problems, corresponding to the stress function and the transverse displacement, are determined and used as approximation functions in a numerically efficient Galerkin formulation. The coupled nonlinear ordinary differential equations of motion are solved using the Runge–Kutta method. Numerical results are presented for disks that are free to translate and rotate at their inner boundary and are constrained from lateral motion by space fixed linear springs. The effects of vibration magnitude on system response in the sub and super-critical speed regions are computed and the effects of large displacements on critical speed behavior and forced response are investigated. Experiments are conducted to verify the accuracy of the numerical results obtained in this paper.     

基于虚拟传感器内插法的叶片高倍频振动辨识方法

叶片的振动及其导致的高周疲劳断裂问题是当前高性能透平机械研发与运行中面临的主要问题,高负荷叶片的流动参数在尾迹的干扰下发生周期性脉动造成高倍频振动是造成高周疲劳的主要因素,因此叶片高倍频振动的监测对高周疲劳的诊断预警具有重要意义。提出了基于虚拟传感器内插法的旋转态叶片高倍频信号重构及辨识方法,可实现高倍频的求解。在传感器安装夹角为6°的情况下可实现高达60倍频以内的振动辨识,理论上只需2支传感器即可进行倍频的识别,实际应用中采用4支传感器即可保证辨识精度,且只需一次启车或停车就可实现叶片振动频率的识别,简化了测试步骤。所提出的辨识方法可应用于航空发动机等静叶片数量较多、振动形式为高阶次高倍频的高端旋转机械的振动监测识别,模拟仿真和试验结果验证了该方法的有效性及准确性。     

Identifying the frequency dependent material property of a hydraulic engine mount through an iterative procedure using 3D finite element modeling

Achieving very restricted noise, vibration and harshness targets in modern vehicles, makes using the hydraulic engine mount crucial. Hydraulic engine mounts have both solid and fluid media in their structures that make their dynamic behavior complex to figure out. We present a three-dimensional model of HEM with using finite element method that encompasses elastomeric material’s nonlinearity and fluid-structure-interaction. Dynamic equivalent modulus of elasticity for elastomeric material is identified through iterative model updating procedure. To do model updating, the results (here, namely, natural frequencies and frequency response function graphs) are compared with real hydraulic engine mount behavior that derived from modal tests. The results showed that the dynamic characteristic of elastomeric material is frequency dependent and can be divided into two distinct regions: below 30 Hz (low frequency) and above 30 Hz (high frequency) with different trends.     

汽车动力总成悬置系统隔振设计分析方法

动力总成是汽车的主要振源。动力总成隔振悬置系统的布置设计与发动机缸数、发动机布置方式、汽车动力传动系的型式及整车隔振性能要求等诸多因素有类。在讨论动力总成悬置系统的设计理论与优化方法的基础上，系统地分析了这些因素对于动力总成悬置系统隔振性能设计目标的影响。并针对两种动力总成进行了优化设计计算分析，通过调节悬置的安装位置，安装角度及悬置的三向主刚度，使系统的解耦程度提高。     

Control of a hybrid active-passive vibration isolation system

Precision vibration control is a major issue in nanotechnology. In particular, nano-precision measurement systems such as Atomic force microscopes (AFM) and Scanning probe microscopes (SPM) are sensitive to ground vibrations. The amplitude of a ground vibration is typically sub-micrometer and ground vibrations adversely affect both the precision and accuracy of these measuring equipment. Consequently, hybrid active-passive vibration isolation systems are typically used as they reduce ground vibrations. This paper presents a hybrid vibration isolation system composed of four spiral metal springs for passive isolation and eight voice coil motors for active isolation. H-infinite and Proportional–integral–derivative (PID) controllers are applied to its 6-DOF vibration control system using six velocity sensors to measure system vibrations. The transmissibility of the presented hybrid isolation system is in the range -10 to -48 dB at its passive resonance frequency and is at least -4 dB better than hybrid isolation systems employing acceleration sensors. The results of various tests conducted to verify the control performance of the developed system with a separately developed shaker indicate that it can serve as a bench-top device for precision measurement machines.     

载重车动力总成悬置系统隔振性能的仿真分析

利用动力学分析软件ADAMS,建立动力总成悬置系统的六自由度动力学模型。在发动机稳态工况下,以悬置支承处 响应力最小为目标函数,对动力总成悬置系统参数进行敏感度分析,选取敏感度高的几个性能参数作为设计变量,对动力总 成悬置系统进行参数优化,优化结果显示系统的隔振性能得到明显的提高。     

车辆动力总成悬置系统参数识别

精确识别车辆动力总成不平衡力以及惯性参数,是对车辆发动机振动进行主动隔离的基础.根据发动机不平衡力只与发动机内部结构以及转速相关的特性,提出一种利用磁流变减振器阻尼参数的可控性,通过测试不同阻尼环境下的各悬置加速度和支座反力,进而识别发动机惯性参数以及不平衡力的新方法.该方法在应用于车辆动力总成悬置系统参数识别时,对比...     

键合图理论在发动机电流变液力悬置中的应用

针对发动机宽频振动的特性,设计开发了一种电流变液力悬置。对键合图理论和电流变液力悬置结构进行了介绍,结合悬置的力学模型,建立了电流变液力悬置的键合图模型,并对模型分析得到状态方程。利用Adams 软件进行仿真分析,比较得出电流变液力悬置比普通液力悬置的隔振性能的优越之处。     

Fault detection and classification in automated assembly machines using machine vision

The geometry of rotary aircraft engine components is usually defined by thin mechanical elements and complex surfaces that are only achievable by 5-axis machining due to either limited access or the design itself. Such thin-walled characteristics make these components susceptible to vibrations while machining and usually require careful manipulation of the toolpath parameters to minimize cutting forces and vibration. Moreover, the tool suppliers’ approach leans towards the feature-build design of cutter geometry to increase the productivity and quality of a machined surface. Some examples of those recent improvements for rotary aircraft engine components are barrel-shaped tools that attempt to increase the contact radius on the tool-part interface to minimize step-over while conserving the scallop height to meet roughness tolerances. This research aims to fill a gap in the current literature by proposing a stability model for barrel-shaped tools. Stability contour maps make use of a mechanistic dynamic force model for barrel-shaped tools. The force model is also capable of including tool runout and orientation angles, tilt and lead, as named in most CAM software. By simulating dynamic forces on the time domain, a contour map is presented to address unstable vibrations. Since forced vibrations and surface location error (SLE) may also appear when milling aircraft parts, SLE and surface roughness are also determined. Finally, given the complexity and number of parameters, validation of the stability maps is performed through experimental chatter tests using a thin wall component.     

Semi-analytical solution of magneto-thermo-elastic stresses for functionally graded variable thickness rotating disks

In this paper, a semi-analytical solution for magneto-thermo-elastic problem in functionally graded (FG) hollow rotating disks with variable thickness placed in uniform magnetic and thermal fields is presented. Stresses and perturbation of magnetic field vector in FG rotating disks are determined using infinitesimal theory of magneto-thermo-elasticity under plane stress conditions. The material properties except Poisson’s ratio are modeled as power-law distribution of volume fraction. The profile of disk thickness is assumed to be a parabolic function of radius. The non-dimensional distribution of temperature, displacement, stresses and perturbation of magnetic field vector throughout radius are shown. Effects of material grading index, geometry of the disk and magnetic field on the stress and displacement fields are investigated. The results of stresses and radial displacements for two different boundary conditions with and without the effect of magnetic field are compared for a FG rotating disk with concave thickness profile. It has been found that imposing a magnetic field significantly decreases tensile circumferential stresses. Therefore the fatigue life of the disk will be significantly improved by applying the magnetic field. Results of this investigation could be applied for optimum design of FG hollow rotating disks with variable thickness.     

The stability of active balancing control using influence coefficients for a variable rotor system

High-speed rotating machines can be very sensitive to rotating mass unbalance that is a major source of harmful vibration for many types of rotating machinery. A balancing procedure is therefore needed for all high-speed rotating systems. To save the time and cost of off-line balancing, many researchers have developed on-line balancing devices and methods. In this paper, an active balancing device, which is of an electro-magnetic type, has been developed and an active balancing method using the influence coefficient method is proposed. The stability of active balancing control is studied in this paper. A stable condition for active balancing control is derived by estimating the errors of influencing coefficients. A gain scheduling control using influence coefficients of the standard model is proposed when the dynamic characteristics of a rotor system are changed. The stability of the balancing method is verified by experiments.