Black-box modelling by rational function approximation

In this paper, a rational function approach is used to approximate the transfer function of linear systems characterized by sampled data. The ill-conditioned Vandermonde-like matrix associated with the ordinary power series is avoided by using Chebyshev polynomials. Clenshaw's recurrence algorithm is applied in transforming the Chebyshev coefficients to the ordinary power series. The passivity of the system is enforced through certain constraints on the residues.