On the minimal order robust servo-regulator for nonlinear systems

This paper shows that the minimal order of the robust servo-regulator proposed by Huang and Lin (1991) and by Huang (1995) is equal to the number of the regulated output times the degree of the minimal polynomial of the what is called k-fold exosystem. This result, coupled with a characterization of the minimal polynomial of the k-fold exosystem leads to a straightforward and efficient procedure to synthesize a minimal order robust servo-regulator.