Identifying a non-commensurable fractional transfer function from a frequency response

This paper extends Levy׳s identification method to non-commensurable fractional models. This identification method allows finding a transfer function that models a frequency response. Explicit expressions for the calculations, using five different variations of the method, are given. A sensitivity analysis supports an empirical way of finding the orders involved. Two application examples, concerning the identification of a model for a viscoelastic material and a model the human arm, are given. •Levy׳s identification method is expanded to non-commensurable fractional models.•Numerical and empirical ways of finding the orders involved are justified.•Models for the human arm are found as an application.