Analysis and Design of Vibration Isolation System Using Open Trenches

Field vibration tests were carried out at a proposed site for the vibration testing room, and 2D numerical analysis using finite difference tool FLAC 5.0 was performed to suggest effective vibration isolation systems. In the analysis, the numerical model is first calibrated with respect to material properties, damping value, and boundary conditions to obtain the output comparable to the field test results. The calibrated model was further used to perform a parametric study by (1)?providing vibrating input motions from vibrating machines to be operated; (2)?using two depths of cutoff trench; and (3)?providing gravel bed, gravel bed with rubber pad, and gravel bed with rubber pad and cutoff trench to study the isolation effects. Comparing the results from the parametric studies with the human perception level of vibration, a decision on the isolation system was determined.     

EIZ90-4型空压机异常振动的处理

因为转子密封器与定子密封器跑合不佳,使转子与定子之间发生摩擦,进而使EIZ90-4型空压机在试车中出现了轴振动值超标现象。简介空压机的结构及主要技术参数,详细介绍空压机试车和振动异常现象,阐述故障原因排查过程和相关处理措施。     

Designing unity magnitude input shaping by using PWM technique

This paper proposes a method for reducing vibrations in flexible systems by using the input shaping. A new input shaper technique based on Pulse Width Modulation (PWM) is used to shape the input.Since unity magnitude (UM) input shaping is easy to implement and provides less control duration, it has been preferred for many application areas. An analytical solution to time locations of the UM shaper requires very complex mathematical expressions due to involving in dependent constraint equations. This paper presents a simple PWM based input shaping method. The proposed technique allows designing UM shapers without analytical solution especially for the shapers having higher order impulse sequence. The method requires only the estimated value of system natural frequency and damping ratio. Desired numbers of impulses can be obtained by comparing reference signal amplitude and carrier wave frequency of a PWM. Analysis and experimental results demonstrate the effectiveness of the proposed method.     

超高速电梯横向振动控制策略的探讨

介绍了国内外超高速电梯横向振动的一些控制方式;提出采用多目标、系统级的集成设计方法,对主动被动控制方法进行优化设计,可能会取得较为满意的控制效果。     

冒落矿震强度预测试验研究

冒落矿震可能诱发一定范围内地下工程失稳,导致更大范围内采空区大面积冒落。基于振速来衡量矿震强度,通过室内岩石块落物冲击试验,总结了下落岩块位势能与诱发基座振动速度的关系;在此基础上,通过在井下特定环境下的抛掷岩石块测振试验,探讨了岩石冲击底板引发的振动效应,并研究了岩层中振速的衰减规律,建立了采空区冒落矿震强度的预测模型。     

地铁隧道内浮置板整体道床施工技术

浮制板整体道床是通过设置在道床下面及两侧的橡胶支座来阻隔轨道结构与主体结构之间的刚性连接,吸收列车冲击能量,从而达到减振和消音的目的。本文着重介绍了浮制板道床的施工工艺流程、关键施工技术和相关参数。     

Supervised locally linear embedding projection (SLLEP) for machinery fault diagnosis

Following the intuition that the measured signal samples usually distribute on or near the nonlinear low-dimensional manifolds embedded in the high-dimensional signal space, this paper proposes a new machinery fault diagnosis approach based on supervised locally linear embedding projection (SLLEP). The approach first performs the recently proposed manifold learning algorithm supervised locally linear embedding (SLLE) on the high-dimensional fault signal samples to learn the intrinsic embedded multiple manifold features corresponding to different fault modes, and map them into a low-dimensional embedded space to achieve fault feature extraction. For dealing with the new fault sample, the approach then applies local linear regression to find the projection that best approximates the implicit mapping from high-dimensional samples to the embedding. Finally fault classification is carried out in the embedded manifold space. The ball bearing data and rotor bed data are both used to validate the proposed approach. The results show that the proposed approach obviously improves the fault classification performance and outperform the other traditional approaches.     

Identification of bearing faults using time domain zero-crossings

In this paper, zero-crossing characteristic features are employed for early detection and identification of single point bearing defects in rotating machinery. As a result of bearing defects, characteristic defect frequencies appear in the machine vibration signal, normally requiring spectral analysis or envelope analysis to identify the defect type. Zero-crossing features are extracted directly from the time domain vibration signal using only the duration between successive zero-crossing intervals and do not require estimation of the rotational frequency. The features are a time domain representation of the composite vibration signature in the spectral domain. Features are normalized by the length of the observation window and classification is performed using a multilayer feedforward neural network. The model was evaluated on vibration data recorded using an accelerometer mounted on an induction motor housing subjected to a number of single point defects with different severity levels.     

The possibility of evaluating turbo-set bearing misalignment defects on the basis of bearing trajectory features

This paper presents the results of computer simulation of bearing misalignment defects in a power turbogenerator. This malfunction is typical for great multi-rotor and multi-bearing rotating machines and very common in power turbo-sets. Necessary calculations were carried out by the computer code system MESWIR, developed and used at the IFFM in Gdansk for calculating dynamics of rotors supported on oil bearings. The results are presented in the form of a set of journal and bush trajectories of all turbo-set bearings. Our analysis focuses on the vibrational effects of displacing the two most vulnerable machine bearings in horizontal and vertical directions by the maximum acceptable range calculated with regard to bearing vibration criterion. This assumption required preliminary assessment of the maximum values for the permissible bearing dislocations. We show the relations between the attributes of the particular bearing trajectories and the bearing displacements in relation to their base design position. The shape and dimensions of bearing trajectories are interpreted based on the theory of hydrodynamic lubrication of oil bearings. It was shown that the relative journal trajectories and absolute bush trajectories carry much important information about the dynamic state of the machine, indicating also the way in which bearings are loaded. Therefore, trajectories can be a source of information about the position and direction of bearing misalignments. This article indicates the potential of using trajectory patterns for diagnosing misalignment defects in rotating machines and suggests including sets of trajectory patterns to the knowledge base of a machine diagnostic system.