Dynamics analysis of vibration process in Particle Impact Noise Detection

Particle Impact Noise Detection (PIND) test is a reliability screening technique for hermetic device that is prescribed by MIL-PRF-39016E. Some test conditions are specified, although MIL-PRF-39016E did not specify how to obtain these condi- tions. This paper establishes the dynamics model of vibration process based on first order mass-spring system. The corresponding Simulink model is also established to simulate vibration process in optional input excitations. The response equations are derived in sinusoidal excitations and the required electromagnetic force waves are computed in order to obtain a given vibration and shock accelerations. Last, some simulation results are given.     

研究生振动结构模态分析课程教学改革与实践探究

针对重庆交通大学航运与船舶工程学院研究生振动结构模态分析课程学时短、内容多且抽象、学生学习积极性不高、到课率低等问题,结合教学实际,通过创新教学模式、制定理论与工程实际相结合的教学内容、实施实验教学与科研结合等措施,对该门课程教学模式进行改革和创新。通过教学实践,研究生对振动结构模态分析课程的学习兴趣显著提高,课程教学改革取得良好效果。     

中厚板轧机非线性控制过程分析

本文建立了二自由度的中厚板轧机非线性垂直振动系统的动力学控制模型,并用Matlab对其进行了参数计算和仿真分析,得到了其相图和时程位移曲线,获得了一种求解中厚板轧机非线性动力学问题的简洁有效的方法。     

汽车NVH特性中的振动噪声分析

随着汽车产业的发展,NVH已经成为评价汽车品质的最重要的技术指标。本文介绍了汽车的NVH特性的意义,分析了汽车振动噪声的来源及其产生的机理,提出了相应的控制对策。     

The solutions of vibration control problems using artificial neural networks

This paper introduces an alternative method artificial neural networks (ANN) used to obtain numerical solutions of mathematical models of dynamic systems, represented by ordinary differential equations (ODEs) and partial differential equations (PDEs). The proposed trial solution of differential equations (DEs) consists of two parts: The initial and boundary conditions (BCs) should be satisfied by the first part. However, the second part is not affected from initial and BCs, but it only tries to satisfy DE. This part involves a feedforward ANN containing adjustable parameters (weight and bias). The proposed solution satisfying boundary and initial condition uses a feedforward ANN with one hidden layer varying the neuron number in the hidden layer according to complexity of the considered problem. The ANN having appropriate architecture has been trained with backpropagation algorithm using an adaptive learning rate to satisfy DE. Moreover, we have, first, developed the general formula for the numerical solutions of nth-order initial-value problems by using ANN.For numerical applications, the ODEs that are the mathematical models of linear and non-linear mass-damper-spring systems and the second- and fourth-order PDEs that are the mathematical models of the control of longitudinal vibrations of rods and lateral vibrations of beams have been considered. Finally, the responses of the controlled and non-controlled systems have been obtained. The obtained results have been graphically presented and some conclusion remarks are given.     

频谱细化技术与功率倒频谱在振动信号分析中的应用

频谱细化技术和功率倒频谱是振动信号分析的两种重要辅助方法.采用细化处理,可以对信号频谱上感兴趣的一段频带进行“局部放大”,从而提高频率分辨率;倒频谱可以识别信号中较弱的周期成分,并对识别调制信号的边频县有特殊的效果.本文在介绍这两种方法基本原理的基础上,运用工程实例说明了其在振动信号分析中的实际应用效果.     

不同频率振动训练对排球运动员核心区力量及稳定性的影响

目的：：研究旨在分析不同频率振动训练对核心区力量及稳定性的影响,选择两种较有代表性的频率(45Hz、30Hz)进行实验研究,探究排球力量训练的新思路,为振动训练方法的完善和排球体能训练的发展提供可参考的依据。方法：将受试者随机分为三组,对照组(无附加振动刺激)、30Hz组、45Hz组,训练时间为9周。实验后采用DAVID核心区力量测试系统对核心区力量进行测试,采用八级腹桥对核心区稳定性进行测试。结果：实验组核心部位后伸、前屈、侧屈、回旋、臀肌力量及核心区稳定性各测试指标提高幅度大于对照组;45Hz组在核心部位后伸、前屈、臀肌力量及稳定性测试成绩优于30Hz组,两实验组侧屈、回旋力量无明显差异。结论：振动训练能够改善核心区力量及稳定性,其中45Hz的振动频率对于提高核心区屈伸肌、臀肌力量和核心区稳定性的效果更好。     

Beam-stabilized optical switch using a voice-coil motor actuator

This paper presents the design, analysis, and implementation of a beam-stabilized optical switch using a voice-coil motor actuator. A closed-loop control system using a proportional-integral-derivative (PID) controller is developed to stabilize the beam at the desired angle to maximize the optical power detected by a photodiode. Experimental results show a good performance with 17 ms switching speed and a maximum overshoot of only 3%.     

A novel technique for optimal placement of piezoelectric actuators on smart structures

The problem of positioning of actuators and sensors on smart materials has been a point of interest in recent years. This is due to the fact that in many practical applications there are limitations in space, weight, etc. of the smart structures, which make the problem of positioning more complex. In addition, it is required that the actuators/sensors have the best possible performance. The development of smart structures technology in recent years has provided numerous opportunities for vibration control applications. The use of piezoelectric ceramics or polymers has shown great promise in the development of this technology. The employment of piezoelectric material as actuators in vibration control is beneficial because these actuators only excite the elastic modes of the structures without exciting the rigid-body modes. This is important since very often only elastic motions of the structures are needed to be controlled. The purpose of this paper is to introduce a novel approach developed for optimizing the location of piezoelectric actuators for vibration suppression of flexible structures. A flexible fin with bonded piezoelectric actuators is considered in this study. The frequency response function (FRF) of the system is then recorded and maximization of the FRF peaks is considered as the objective function of the optimization algorithm to find the optimal placement of the piezoelectric actuators on the smart fin. Three multi-layer perceptron neural networks are employed to perform surface fitting to the discrete data generated by the finite element method (FEM). Invasive weed optimization (IWO), a novel numerical stochastic optimization algorithm, is then employed to maximize the weighted summation of FRF peaks. Results indicate an accurate surface fitting for the FRF peak data and an optimal placement of the piezoelectric actuators for vibration suppression is achieved.     

The acute effects of vibration stimulus following FIFA 11+ on agility and reactive strength in collegiate soccer players

PurposeThe aim of this study was to assess the effects of combining the FIFA 11+ and acute vibration training on reactive strength index (RSI) and 505 agility.MethodsSeventy-four male collegiate soccer players took part in the study and were randomly assigned to FIFA 11+ with acute vibration group (FIFA + WBV), FIFA 11+ with isometric squat group (FIFA + IS) or a control group consisting of the FIFA 11+ alone (Con). The warm-up consisted of the FIFA 11+ and was administered to all participants. The participants in the acute vibration group were exposed to 30 s whole body vibration in squat position immediately post warm-up. The isometric group completed an isometric squat for 30 s immediately post warm-up.ResultsRSI significantly improved pre- to post-intervention amongst FIFA + WBV (p < 0.001) due to a decrease in contact time (p < 0.001) in comparison to FIFA + IS and Con, but 505 agility was not affected.ConclusionThe results of this study suggest the inclusion of an acute bout of WBV post FIFA 11+ warm-up produces a neuromuscular response leading to an improvement in RSI. Future research is required to examine the exact mechanisms behind these improvements amongst other populations and over time course of the performance.