A hardware-oriented method for simulating service loads
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This is the third paper in a series which includes A Computer Method for Simulating Service Loads' (pp. 42–46) and ‘A Spectral-Analysis Method for Nonstationary Field Measurements’ (pp. 47–55). This paper presents a hardware method to digitally simulate nonstationary stochastic signals which are analyzed using the procedures outlined in the first paper. The method of analysis hypothesizes that the nonstationary signal consists of two stationary signals which belong to different populations occurring consecutively according to a suitable probabilistic model. The analysis procedure involves the following steps: segmenting the time history, estimating the population of each segment, estimating the power spectrum of each segment, averaging the power spectra which belong to each population, presenting the power spectra via parameters of digital filters which shape white-noise sequences into sequences with the measured power spectra, and measuring the parameters of the probabilistic method.This paper presents a simulation method that uses the results of the analysis method above to create a sequence that simulates the statistical characteristics of nonstationary field data. This simulation method is designed to be efficiently generated via a simple digital-electronic circuit and to be available at a high sampling rate.First a review of the stochastic model is given. The simulation method is then illustrated by means of a block diagram. The main steps of the simulation method include generation of a white sequence, generation of the probabilistic model, and digital filtering. The circuits used for these three-functions are illustrated, and sample results of the use of this hardware are presented. This simulation method can provide a fast reproducible sequence for running mechanical testing mechines.
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