Current Issue : January - March Volume : 2014 Issue Number : 1 Articles : 5 Articles
This paper investigates the variation of vertical vibrations of vehicles using a neural network (NN). The NN is a back propagation\r\nNN, which is employed to predict the amplitude of acceleration for different road conditions such as concrete, waved stone block\r\npaved, and country roads. In this paper, four supervised functions, namely, newff, newcf, newelm, and newfftd, have been used for\r\nmodeling the vehicle vibrations.Thenetworks have four inputs of velocity (V), damping ratio (?),natural frequency of vehicle shock\r\nabsorber (Wn), and road condition (R.C) as the independent variables and one output of acceleration amplitude (AA). Numerical\r\ndata, employed for training the networks and capabilities of the models in predicting the vehicle vibrations, have been verified.\r\nSome training algorithms are used for creating the network. The results show that the Levenberg-Marquardt training algorithm\r\nand newelm function are better than other training algorithms and functions. This method is conceptually straightforward, and it\r\nis also applicable to other type vehicles for practical purposes....
Harvesting power with a piezoelectric vibration powered generator using a full-wave rectifier conditioning circuit is experimentally\r\ncompared for varying sinusoidal, random, and sine on random(SOR) input vibration scenarios; the implications of source vibration\r\ncharacteristics on harvester design are discussed. The rise in popularity of harvesting energy from ambient vibrations has made\r\ncompact, energy dense piezoelectric generators commercially available. Much of the available literature focuses on maximizing\r\nharvested power through nonlinear processing circuits that require accurate knowledge of generator internal mechanical and\r\nelectrical characteristics and idealization of the input vibration source, which cannot be assumed in general application. Variations\r\nin source vibration and load resistance are explored for a commercially available piezoelectric generator. The results agree with\r\nnumerical and theoretical predictions in the previous literature for optimal power harvesting in sinusoidal and flat broadband\r\nvibration scenarios. Going beyond idealized steady-state sinusoidal and flat random vibration input, experimental SOR testing\r\nallows for more accurate representation of real world ambient vibration. It is shown that characteristic interactions from more\r\ncomplex vibration sources significantly alter power generation and processing requirements by varying harvested power, shifting\r\noptimal conditioning impedance, inducing voltage fluctuations, and ultimately rendering idealized sinusoidal and randomanalyses\r\nincorrect....
Vibration analysis is widely used for rotating machinery diagnostics; however measuring vibration of operational oil well pumps is\r\nnot possible.The pump�s driver�s current signatures may provide condition-related information without the need for an access to\r\nthe pump itself. This paper investigates the degree of relationship between the pump�s driver�s current signatures and its induced\r\nvibration. This relationship between the driver�s current signatures (DCS) and its vibration signatures (DVS) is studied by calculating\r\nmagnitude-squared coherence and phase coherence parameters at a certain frequency band using continuous wavelet transform\r\n(CWT). The CWT coherence-based technique allows better analysis of temporal evolution of the frequency content of dynamic\r\nsignals and areas in the time-frequency planewhere the two signals exhibit common power or consistent phase behaviour indicating\r\na relationship between the signals. This novel approach is validated by experimental data acquired from 3 kW petroleum pump�s\r\ndriver. Both vibration and current signatureswere acquired under different speed and load conditions.Theoutcomes of this research\r\nsuggest the use of DCS analysis as reliable and inexpensive condition monitoring tool, which could be implemented for oil pumps,\r\nreal-time monitoring associated with condition-based maintenance (CBM) program....
In structural dynamic systems, there is inevitable uncertainty in the input power from a source to a receiver. Apart from the\r\nnondeterministic properties of the source and receiver, there is also uncertainty in the excitation. This comes from the uncertainty\r\nof the forcing location on the receiver and, for multiple contact points, the relative phases, the force amplitude distribution at those\r\npoints, and also their spatial separation. This paper investigates quantification of the uncertainty using possibilistic or probabilistic\r\napproaches. These provide the maximum and minimum bounds and the statistics of the input power, respectively. Expressions\r\nfor the bounds, mean, and variance are presented. First the input power from multiple point forces acting on an infinite plate is\r\nexamined.The problem is then extended to the input power to a finite plate described in terms of its modes. The uncertainty due\r\nto the force amplitude is also discussed. Finally, the contribution of moment excitation to the input power, which is often ignored\r\nin the calculation, is investigated. For all cases, frequency band-averaged results are presented....
This paper studies the influence of boundary conditions on a fluid medium of finite depth.We determine the frequencies and the\r\nmodal shapes of the fluid. The fluid is assumed to be incompressible and viscous. A potential technique is used to obtain in threedimensional\r\ncylindrical coordinates a general solution for a problem.Themethod consists in solving analytically partial differential\r\nequations obtained from the linearized Navier-Stokes equation. A finite element analysis is also used to check the validity of the\r\npresent method. The results from the proposed method are in good agreement with numerical solutions. The effect of the fluid\r\nthickness on the Stokes eigenmodes is also investigated. It is found that frequencies are strongly influenced....
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