A new method for the integer order approximation of fractional order models

This paper is concerned with the finite–dimensional approximation of a fractional–order system represented in state–space form. To this purpose, resort is made to the Oustaloup method for approximating a fractional–order integrator by a rational filter. The dimension of the resulting integer–order model can be reduced using an efficient algorithm for the minimization of the L2 norm of a weighted equation error. Two numerical examples are worked out to show how the desired approximation accuracy can be ensured.