Vehicle Vibration Safety Evaluation in the Time Domain

Abstract

The article is a sequel to studies of the nonlinear vibration isolation systems of a vehicle. The first published papers considered an application of the known methods of statistical linearization when determining the vibration safety performance in the frequency domain. The frequency domain is the most adaptive in the context of analysis of the obtained calculation results and evaluation of the initial dynamic system features. Therefore, a problem to determine the adequacy range of such calculations in the frequency and time domain is relevant.The paper deals with the problem of creating a technique to determine and analyze the spectral characteristics of the vehicle vibration isolation system when modeling in the time domain. Considers as an object, a nonlinear dynamic system equivalent to the nonlinear vibration isolation system of a vehicle under its spatial vibrations. In formulating a system of equations-of-motion of the adopted system a module-based method was used. As an example, the power unit is given. Modeling of input random perturbations, provided that the solutions obtained are adequate, is based on the recurrent difference equations. The subsequent transformation of the calculation results into the frequency domain is based on the finite Fourier transforms.To determine the final parameters which characterise the effectiveness of the vibration isolation system, at the first stage of calculations the dynamic system was tested in a linear setting.The vector of natural frequencies of a conservative system defined in the frequency domain was compared with the spectrum of natural frequencies (the frequency response) calculated in the time domain. Besides, the article has carried out a conformity evaluation of the amplitude-frequency characteristics obtained in the frequency and time domain and their determining accuracy. The obtained positive results made it possible to compare and analyze the spectral characteristics of vibration signals and dynamic system in its nonlinear and linearized formulation. The coherence function, the amplitude-frequency characteristic, the spectral density of perturbation and output vibration signal, the vehicle suspension and tyre load characteristics are considered as the analyzed ones. The article compares the output characteristics of the dynamic system under consideration for the case in linear, linearized, and nonlinear formulation of the problem.