Transfer-Function Identification Using a Complex Curve-Fitting Technique

Abstract

The mathematical analysis and synthesis of linear-dynamic systems, based on experimental test results, often requires that the frequency response of the system be fitted by an algebraic expression. The form in which this expression is usually desired is that of a ratio of two frequency-dependent polynomials. In this paper, a method based upon the minimization of the weighted sum of the squares of the differences between the measured data and the approximating function is presented as a means for the evaluation of the polynomial coefficients of the approximating function. The computer programme used will be discussed and the modifications that improve the accuracy of the calculated coefficients, although the data points may be subject to measurement inaccuracies.